WorldWideScience

Sample records for images saturne revisitee

  1. HST image of Saturn's 'white spot'

    Science.gov (United States)

    1990-01-01

    Saturn's 'white spot' or cloud believed to be ammonia ice crystals recorded by the Hubble Space Telescope (HST) planetary camera in blue and infrared light. HST data was computer-processed improving the image sharpness.

  2. Saturn

    CERN Document Server

    Vescia, Monique

    2017-01-01

    Saturn is one of the most surreal of all the planets in our solar system. With this intriguing curriculum-correlated book, young readers can learn just why. Saturn has many unusual features, such as rings made of ice, ammonia storms, and methane rain. Its density is less than that of water so theoretically it could float on water. The features of its many moons are sometimes even stranger. The Pioneer and Voyager missions in 1970s and 1980s offered stunning images included in the book, which will allow readers to have an armchair experience of exploring this fascinating planet.

  3. UV Imaging Spectroscopy of the Saturn System

    Science.gov (United States)

    Esposito, L. W.

    2014-12-01

    Highlights of the UVIS investigation on Cassini include the discovery of a neutral oxygen cloud surrounding Saturn and the determination that Saturn's magnetosphere is dominated by neutrals. Later, UVIS observed and measured the cause of these phenomena: that the icy moon Enceladus is erupting water molecules at about 200kg/sec from fissures in its south polar terrain. These eruptions also carry a fraction of small solid ice grains that are sufficient to produce Saturn's ethereal E ring. The morphology of the jets of vapor in the Enceladus plume imply supersonic flow velocities that loft the grains carried in the jets, consistent with theoretical models. UV occultations and spectroscopy define the constituents of Titan's upper atmosphere and explain its dayside and nightside emissions. UVIS sees Saturn's auroral oval evolve and has detected Enceladus' footprint. Self-Gravity Wakes in Saturn's rings were detected by comparing ring occultations with Voyager results and with multiple Cassini UVIS occultations at a range of viewing aspects. We developed a simple 'granola-bar model' to explain our observations and the azimuthal brightness asymmetry observed from the Earth and previous space missions. UVIS has detected numerous small structures in the rings: kittens, propellers and other embedded objects. Some are as small as meters across from UVIS 'tracking' occultations. Features preferentially form where the rings are stirred by resonances and nearby passing moons. This more active ring system seen by Cassini may explain bright haloes in the rings; how the ring system can recycle ring material so that the rings are much older than inferred from Voyager; and provide implications of how planets may form. Future observations will provide the best resolution on active features like edges of the rings, ring haloes and propeller bands.

  4. Constraints on Saturn's Tropospheric General Circulation from Cassini ISS Images

    Science.gov (United States)

    DelGenio, Anthony D.; Barbara, John M.

    2013-01-01

    An automated cloud tracking algorithm is applied to Cassini Imaging Science Subsystem high-resolution apoapsis images of Saturn from 2005 and 2007 and moderate resolution images from 2011 and 2012 to define the near-global distribution of zonal winds and eddy momentum fluxes at the middle troposphere cloud level and in the upper troposphere haze. Improvements in the tracking algorithm combined with the greater feature contrast in the northern hemisphere during the approach to spring equinox allow for better rejection of erroneous wind vectors, a more objective assessment at any latitude of the quality of the mean zonal wind, and a population of winds comparable in size to that available for the much higher contrast atmosphere of Jupiter. Zonal winds at cloud level changed little between 2005 and 2007 at all latitudes sampled. Upper troposphere zonal winds derived from methane band images are approx. 10 m/s weaker than cloud level winds in the cores of eastward jets and approx. 5 m/s stronger on either side of the jet core, i.e., eastward jets appear to broaden with increasing altitude. In westward jet regions winds are approximately the same at both altitudes. Lateral eddy momentum fluxes are directed into eastward jet cores, including the strong equatorial jet, and away from westward jet cores and weaken with increasing altitude on the flanks of the eastward jets, consistent with the upward broadening of these jets. The conversion rate of eddy to mean zonal kinetic energy at the visible cloud level is larger in eastward jet regions (5.2x10(exp -5) sq m/s) and smaller in westward jet regions (1.6x10(exp -5) sqm/s) than the global mean value (4.1x10(ep -5) sq m/s). Overall the results are consistent with theories that suggest that the jets and the overturning meridional circulation at cloud level on Saturn are maintained at least in part by eddies due to instabilities of the large-scale flow near and/or below the cloud level.

  5. Quantitative measurements of Jupiter, Saturn, their rings and satellites made from Voyager imaging data

    Science.gov (United States)

    Collins, S. A.; Bunker, A. S.

    1983-01-01

    The Voyager spacecraft cameras use selenium-sulfur slow scan vidicons to convert focused optical images into sensible electrical signals. The vidicon-generated data thus obtained are the basis of measurements of much greater precision than was previously possible, in virtue of their superior linearity, geometric fidelity, and the use of in-flight calibration. Attention is given to positional, radiometric, and dynamical measurements conducted on the basis of vidicon data for the Saturn rings, the Saturn satellites, and the Jupiter atmosphere.

  6. Saturn's Magnetotail

    Science.gov (United States)

    Jackman, Caitríona M.

    2015-01-01

    Saturn has often been described as intermediate between Earth and Jupiter in terms of its magnetospheric dynamics. It has a well-developed magnetotail, the region which stretches vast distances on the nightside of the planet, shaped by the solar wind and interplanetary magnetic field (IMF) flowing past the magnetosphere. This chapter describes the large-scale tail structure, magnetospheric dynamics, and remote sensing in detail. In addition to in situ exploration of Saturn's tail, planetary radio emissions and auroral images can be used as excellent remote diagnostics of tail dynamics. The chapter discusses Saturn's radio emissions and auroral images in more detail. Remote sensing of radio emissions and images of Saturn's aurora in a multitude of wavelengths show the far-reaching effects of tail reconfigurations.

  7. Image-processing techniques in precisely measuring positions of Saturn and its satellites

    Institute of Scientific and Technical Information of China (English)

    PENG; Qingyu; (彭青玉)

    2003-01-01

    After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn's position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more opportunities to accurately measure the positions of Mimas and Enceladus-- two satellites very close to the Saturn. Experimental tests with 127 frames of CCD images obtained on the 1-meter telescope at the Yunnan Observatory over three nights show that the geometric center of the Saturnian ring and its 4 satellites (Tethys, Dione, Rhea and Titan) have the same positional precision, and the standard error for a single observation is less than ±0.05 arcsec. It is believed that these new techniques would have important impetus to the positional measurement of both Saturn by using a CCD meridian instrument and its faint satellites by using a long focal length telescope.

  8. Saturn's vertical and latitudinal cloud structure 1991 2004 from HST imaging in 30 filters

    Science.gov (United States)

    Karkoschka, Erich; Tomasko, Martin

    2005-12-01

    We analyzed 134 images of Saturn taken by the Hubble Space Telescope between 1991 and 2004. The images cover wavelengths between 231 and 2370 nm in 30 filters. We combined some 10 million calibrated reflectivity measurements into 18,000 center-to-limb curves. We used the method of principal component analysis to find the main latitudinal and temporal variations in Saturn's atmosphere and their spectral characteristics. The first principal variation is a strong latitudinal variation of the aerosol optical depth in the upper troposphere. This structure shifts with Saturn's seasons, but the structure on small scales of latitude stays constant. The second principal variation is a variable optical depth of stratospheric aerosols. The optical depth is large at the poles and small at mid- and low latitudes with a steep gradient in-between. This structure remains essentially constant in time. The third principal variation is a variation in the tropospheric aerosol size, which has only shallow gradients with latitude, but large seasonal variations. Thus, aerosol sizes and their phase functions inferred at a particular season are not representative of Saturn's atmosphere at other seasons. Aerosols are largest in the summer and smallest in the winter. The fourth principal variation is a feature of the tropospheric aerosols with irregular latitudinal structure and fast variability, on the time scale of months. Spherical aerosols do not display the spectral characteristic of that feature. We suspect that variations in the shape of aerosols may play a role. We found a spectral feature of the imaginary index of aerosols, which darkens them near 400 nm wavelength. While we can describe Saturn's variations quite accurately, our presented model of Saturn's average atmosphere is still uncertain due to possible systematic offsets in methane absorption data and limitations of the knowledge about the shape of aerosols. In order to compare our results with those from comparable

  9. An objective classification of Saturn cloud features from Cassini ISS images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-06-01

    A k-means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible-infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baroclinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  10. An Objective Classification of Saturn Cloud Features from Cassini ISS Images

    Science.gov (United States)

    Del Genio, Anthony D.; Barbara, John M.

    2016-01-01

    A k -means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible- infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baro-clinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

  11. A Strong High Altitude Narrow Jet At Saturn'S Equator From Cassini/ISS Images

    Science.gov (United States)

    Garcia-Melendo, Enrique; Sánchez-Lavega, A.; Legarreta, J.; Pérez-Hoyos, S.; Hueso, R.

    2010-10-01

    The intense equatorial eastward jets observed at cloud level in Jupiter and Saturn, represent a major challenge for geophysical fluid dynamics. Saturn's equatorial jet is of particular interest in view of its three dimensional structure, suspected large temporal variability, and related stratospheric semiannual oscillation. Here we report the discovery at the upper cloud level of an extremely narrow and strong jet centered in the middle of the broad equatorial jet. Previously published works on Saturn's equatorial winds at cloud level provided only a partial coverage. Automatic correlation of brightness scans and manually tracked cloud features, retrieved from images obtained by the Cassini Imaging Science Subsystem (ISS), show that the jet reaches 430 ms-1 with a peak speed difference of 180 ms-1 relative to nearby latitudes at 60 mbar and 390 ms-1 at depths > 500 mbar. Images were obtained in two filters: MT3, centred at the 889nm strong methane absorption band, and CB3 centred at the near infrared 939nm continuum, which are sensitive to different altitude levels at the upper clouds and hazes. Contrarily to what is observed in other latitudes, its velocity increases with altitude. Our findings helps to extend the view we have of the equatorial stratospheric dynamics of fast rotating planets beyond the best known terrestrial environment, and extract more general consequences of the interaction between waves and mean flow. It remains to be known if this equatorial jet structure, now determined in detail in three dimensions, is permanent or variable with the seasonal solar insolation cycle, including the variable shadow cast by the rings. EGM, ASL, JL, SPH, and RH have been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and ASL, JL, SPH, and RH by Grupos Gobierno Vasco IT-464-07

  12. Searching for a traveling feature in Saturn's rings in Cassini Imaging Science Subsystem data

    Science.gov (United States)

    Aye, Klaus-Michael; Rehnberg, Morgan; Brown, Zarah; Esposito, Larry W.

    2016-10-01

    Introduction: Using Cassini UVIS occultation data, a traveling wave feature has been identified in the Saturn rings that is most likely caused by the radial positions swap of the moons Janus and Epimetheus [1]. The hypothesis is that non-linear interferences between the linear density waves when being relocated by the moon swap create a solitary wave that is traveling outward through the rings. The observations in [1] further lead to the derivation of values for the radial travel speeds of the identified traveling features, from 39.6 km/yr for the Janus 5:4 resonance up to 45.8 for the Janus 4:3 resonance.Previous confirmations in ISS data: Work in [1] also identified the feature in Cassini Imaging Science Subsystem (ISS) data that was taken around the time of the UVIS occultations where the phenomenon was first discovered, so far one ISS image for each Janus resonances 2:1, 4:3, 5:4, and 6:5.Search guided by predicted locations: Using the observation-fitted radial velocities from [1], we can extrapolate these to identify Saturn radii at which the traveling feature should be found at later times. Using this and new image analysis and plotting tools available in [2], we have identified a potential candidate feature in an ISS image that was taken 2.5 years after the feature causing moon swap in January 2006. We intend to expand our search by identifying candidate ISS data by a meta-database search constraining the radius at future times corresponding to the predicted future locations of the hypothesized solitary wave and present our findings at this conference.References: [1] Rehnberg, M.E., Esposito, L.W., Brown, Z.L., Albers, N., Sremčević, M., Stewart, G.R., 2016. A Traveling Feature in Saturn's Rings. Icarus, accepted in June 2016. [2] K.-Michael Aye. (2016). pyciss: v0.5.0. Zenodo. 10.5281/zenodo.53092

  13. Saturn and How to Observe it

    CERN Document Server

    Benton, Julius L

    2005-01-01

    Saturn is the second largest planet in the solar system, and the only one with a spectacular ring system easily visible from Earth. Julius Benton's Saturn and How to Observe It provides a compendium of the latest information, amateur and professional images of Saturn. These images are followed by advice on how to observe Saturn using a variety of telescope apertures, color filters and magnifications. This text is a goldmine of information for all levels of amateur observers, from the beginner to the highly experienced. Brought to life by crisp color photographs, Saturn and How to Observe It is a modern comprehensive review of Saturn as a planet and its magnificent ring system. The book includes some of the latest detailed theories and physical descriptions of Saturn and its satellites. The techniques for observing Saturn are outlined in this book, giving the reader a thorough explanation of what they are viewing.

  14. The Faces of Saturn: Images and Texts from Augustus through Dürer to Galileo

    Science.gov (United States)

    Shank, M. H.

    2013-04-01

    This paper follows the thread(s) of Saturn in astrology and art from the Babylonians to Galileo, paying special attention to the planet's political importance from Augustus to the Medici and to its medical/psychological significance from Ficino through Dürer. In passing, I extend David Pingree's astrological interpretation of Dürer's Melencholia I and propose a very personal rationale for the engraving, namely as a memorial to his mother.

  15. Saturns Thermal Emission at 2.2-cm Wavelength as Imaged by the Cassini RADAR Radiometer

    Science.gov (United States)

    Janssen, M. A.; Ingersoll, A. P.; Allison, M. D.; Gulkis, S.; Laraia, A. L.; Baines, K. H.; Edgington, S. G.; Anderson, Y. Z.; Kelleher, K.; Oyafuso, F. A.

    2013-01-01

    We present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10deg planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at -35deg latitude; occasional large oval features with depleted ammonia around -45deg latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.

  16. Crater Relaxation and Stereo Imaging of the Icy Satellites of Jupiter and Saturn

    Science.gov (United States)

    Phillips, C. B.; Beyer, R. A.; Nimmo, F.; Roberts, J. H.; Robuchon, G.

    2010-12-01

    Crater relaxation has been used as a probe of subsurface temperature structure for over thirty years, both on terrestrial bodies and icy satellites. We are developing and testing two independent methods for processing stereo pairs to produce digital elevation models, to address how crater relaxation depends on crater diameter, geographic location, and stratigraphic position on the icy satellites of Jupiter and Saturn. Our topographic profiles will then serve as input into two numerical models, one viscous and one viscoelastic, to allow us to probe the subsurface thermal profiles and relaxation histories of these satellites. We are constructing stereo topography from Galileo and Cassini image pairs using the NASA Ames Stereo Pipeline (Moratto et al. 2010), an automated stereogrammetry tool designed for processing planetary imagery captured from orbiting and landed robotic explorers on other planets. We will also be using the commercial program SOCET SET from BAE Systems (Miller and Walker 1993; 1995). Qualitatively, it is clear that there are large spatial variations in the degree of crater relaxation among Jupiter’s and Saturn’s satellites. However, our use of stereo topography will allow quantitative measures of crater relaxation (e.g. depth:diameter ratio or equivalent) to be derived. Such measures are essential to derive quantitative estimates of the heat fluxes responsible for this relaxation. Estimating how surface heat flux has varied with time provides critical constraints on satellite thermal (and orbital) evolution. Craters undergo viscous relaxation over time at a rate that depends on the temperature gradient and crater scale. We are investigating how the near-surface satellite heat flux varied in time and space, based on our crater relaxation observations. Once we have crater profiles from our DEMs, we use them as input to two theoretical approaches: a relatively simple (viscous) numerical model in which time-varying heat fluxes can be included, and

  17. Statistical study of Saturn's auroral electron properties with Cassini/UVIS FUV spectral images

    Science.gov (United States)

    Gustin, J.; Grodent, D.; Radioti, A.; Pryor, W.; Lamy, L.; Ajello, J.

    2017-03-01

    About 2000 FUV spectra of different regions of Saturn's aurora, obtained with Cassini/UVIS from December 2007 to October 2014 have been examined. Two methods have been employed to determine the mean energy of the precipitating electrons. The first is based on the absorption of the auroral emission by hydrocarbons and the second uses the ratio between the brightness of the Lyman-α line and the H2 total UV emission (Lyα/H2), which is directly related to via a radiative transfer formalism. In addition, two atmospheric models obtained recently from UVIS polar occultations have been employed for the first time. It is found that the atmospheric model related to North observations near 70° latitude provides the results most consistent with constraints previously published. On a global point of view, the two methods provide comparable results, with mostly in the 7-17 keV range with the hydrocarbon method and in the 1-11 keV range with the Lyα/H2 method. Since hydrocarbons have been detected on ∼20% of the auroral spectra, the Lyα/H2 technique is more effective to describe the primary auroral electrons, as it is applicable to all spectra and allows an access to the lowest range of energies (≤5 keV), unreachable by the hydrocarbon method. The distribution of is found fully compatible with independent HST/ACS constraints (emission peak in the 840-1450 km range) and FUSE findings (emission peaking at pressure level ≤0.2 μbar). In addition, exhibits enhancements in the 3 LT-10 LT sector, consistent with SKR intensity measurements. An energy flux-electron energy diagram built from all the data points strongly suggests that acceleration by field-aligned potentials as described by Knight's theory is a main mechanism responsible for electron precipitation creating the aurora. Assuming a fixed electron temperature of 0.1 keV, a best-fit equatorial electron source population density of 3 × 103 m-3 is derived, which matches very well to the plasma properties observed with

  18. Kinematics of Saturn's spokes

    Science.gov (United States)

    Gruen, E.; Garneau, G. W.; Terrile, R. J.; Johnson, T. V.; Morfill, G. E.

    1984-01-01

    Voyager 2 images of Saturn's rings have been analyzed for spoke activity. More than 80 and 40 different spokes have been measured at the morning and at the evening ansa, respectively. Higher rate of spoke formation has been found at 145 + or 15 deg SLS and at 305 + or - 15 deg SLS which persisted for at least 3 Saturn revolutions. Higher spoke activity (formation and growth in width) by more than a factor 3 has been observed over the nightside hemisphere of Saturn than over the dayside hemisphere. The age distribution (i.e., time from radial formation until observation, assuming Keplerian shear) of the leading (old) edges of spokes has its maximum at approximately 9,000 s and 6,000 s for spokes observed at the morning ansa and at the evening ansa, respectively. The highest spoke age observed is approximately 20,000 s.

  19. Measurements of Seasonal Changes in Saturn's Zonal Wind and Vertical Wind Shear between 2004 and 2016 from Cassini ISS Images

    Science.gov (United States)

    Blalock, John J.; Sayanagi, Kunio M.; Ingersoll, Andrew P.; Dyudina, Ulyana A.; Ewald, Shawn P.

    2016-10-01

    We present updated zonal wind measurements of Saturn using Cassini ISS images between 2004 and 2016. In addition, we present measurements of the vertical wind shear between the cloud levels sensed in the near-infrared continuum band at 750 nm (CB2 filter) and the methane bands at 727 and 889 nm (MT2 and MT3 filters). We previously reported that there may be small seasonal changes in Saturn's zonal wind profile but it was inconclusive due to measurement uncertainties. In our previous reports, we used the zonal standard deviation of the wind vectors as a proxy for the measurement uncertainty. However, zonal standard deviation contains contributions from both real spatial variations in the wind speed as well as uncertainties in the measurements. This raised a difficulty in distinguishing small, real changes in the wind field from the uncertainties in the measurement. We have developed a technique which isolates real spatial variations from measurement uncertainties by analyzing the correlation fields produced in the two-dimensional Correlation Imaging Velocimetry (CIV) cloud-tracking wind measurement method. In our new method, for each single wind vector measurement, we fit an ellipse to the correlation threshold contour, and define it as the uncertainty ellipse of each wind vector. The advantage of our method is that it allows quantification of the anisotropic uncertainty components of each single wind vector, i.e., using the uncertainty ellipse, we deduce the northward, southward, eastward and westward uncertainties for each wind vector from the correlation peak. Comparing the uncertainty values of each wind vector to the zonal standard deviation of all wind vectors at each latitude allows us to decouple the real spatial variations in the wind from the measurement uncertainties. Using this technique, our measurements show small seasonal variations in Saturn's zonal wind profile as well as the vertical wind shear. As a next step, we plan to apply our uncertainty

  20. Cassini at Saturn Huygens results

    CERN Document Server

    Harland, David M

    2007-01-01

    "Cassini At Saturn - Huygens Results" will bring the story of the Cassini-Huygens mission and their joint exploration of the Saturnian system right up to date. Cassini is due to enter orbit around Saturn on the 1 July 2004 and the author will have 8 months of scientific data available for review, including the most spectacular images of Saturn, its rings and satellites ever obtained by a space mission. As the Cassini spacecraft approached its destination in spring 2004, the quality of the images already being returned by the spacecraft clearly demonstrate the spectacular nature of the close-range views that will be obtained. The book will contain a 16-page colour section, comprising a carefully chosen selection of the most stunning images to be released during the spacecraft's initial period of operation. The Huygens craft will be released by Cassini in December 2004 and is due to parachute through the clouds of Saturn's largest moon, Titan, in January 2005.

  1. Overview of Saturn lightning observations

    CERN Document Server

    Fischer, G; Kurth, W S; Gurnett, D A; Zarka, P; Barry, T; Delcroix, M; Go, C; Peach, D; Vandebergh, R; Wesley, A

    2011-01-01

    The lightning activity in Saturn's atmosphere has been monitored by Cassini for more than six years. The continuous observations of the radio signatures called SEDs (Saturn Electrostatic Discharges) combine favorably with imaging observations of related cloud features as well as direct observations of flash-illuminated cloud tops. The Cassini RPWS (Radio and Plasma Wave Science) instrument and ISS (Imaging Science Subsystem) in orbit around Saturn also received ground-based support: The intense SED radio waves were also detected by the giant UTR-2 radio telescope, and committed amateurs observed SED-related white spots with their backyard optical telescopes. Furthermore, the Cassini VIMS (Visual and Infrared Mapping Spectrometer) and CIRS (Composite Infrared Spectrometer) instruments have provided some information on chemical constituents possibly created by the lightning discharges and transported upward to Saturn's upper atmosphere by vertical convection. In this paper we summarize the main results on Satur...

  2. Cryoclast distribution on the damascus sulcus region of enceladus moon (saturn) using vims images

    Science.gov (United States)

    Forero, L. M.; Sánchez, J.; Saavedra, F.

    2017-07-01

    At Damascus Sulcus area within SPT (South Polar Terrain) there were interpreted a series of images where it was analyzed the distribution of different size particles that are ejected by distinct criovolcanic sources based on the analysis of the morphology, tectonic, reflectance and spectral signature of the surface material. This work shows these observations by comparing high resolution images of VIMS and ISS in combination with a Digital Elevation Model.

  3. Imaging the interaction of the heliosphere with the interstellar medium from Saturn with Cassini.

    Science.gov (United States)

    Krimigis, S M; Mitchell, D G; Roelof, E C; Hsieh, K C; McComas, D J

    2009-11-13

    We report an all-sky image of energetic neutral atoms (ENAs) >6 kilo-electron volts produced by energetic protons occupying the region (heliosheath) between the boundary of the extended solar atmosphere and the local interstellar medium (LISM). The map obtained by the Ion and Neutral Camera (INCA) onboard Cassini reveals a broad belt of energetic protons whose nonthermal pressure is comparable to that of the local interstellar magnetic field. The belt, centered at approximately 260 degrees ecliptic longitude extending from north to south and looping back through approximately 80 degrees, appears to be ordered by the local interstellar magnetic field. The shape revealed by the ENA image does not conform to current models, wherein the heliosphere resembles a cometlike figure aligned in the direction of Sun's travel through the LISM.

  4. The Orbits of Saturn's Small Satellites Derived from Combined Historic and Cassini Imaging Observations

    Science.gov (United States)

    Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M., Jr.

    2006-08-01

    We report on the orbits of the small, inner Saturnian satellites, either recovered or newly discovered in recent Cassini imaging observations. The orbits presented here reflect improvements over our previously published values in that the time base of Cassini observations has been extended, and numerical orbital integrations have been performed in those cases in which simple precessing elliptical, inclined orbit solutions were found to be inadequate. Using combined Cassini and Voyager observations, we obtain an eccentricity for Pan 7 times smaller than previously reported because of the predominance of higher quality Cassini data in the fit. The orbit of the small satellite (S/2005 S1 [Daphnis]) discovered by Cassini in the Keeler gap in the outer A ring appears to be circular and coplanar; no external perturbations are apparent. Refined orbits of Atlas, Prometheus, Pandora, Janus, and Epimetheus are based on Cassini , Voyager, Hubble Space Telescope, and Earth-based data and a numerical integration perturbed by all the massive satellites and each other. Atlas is significantly perturbed by Prometheus, and to a lesser extent by Pandora, through high-wavenumber mean-motion resonances. Orbital integrations involving Atlas yield a mass of GMAtlas=(0.44+/-0.04)×10-3 km3 s -2, 3 times larger than reported previously (GM is the product of the Newtonian constant of gravitation G and the satellite mass M). Orbital integrations show that Methone is perturbed by Mimas, Pallene is perturbed by Enceladus, and Polydeuces librates around Dione's L5 point with a period of about 791 days. We report on the nature and orbits of bodies sighted in the F ring, two of which may have persisted for a year or more.

  5. Illustration of Saturn's Rings

    Science.gov (United States)

    2001-01-01

    This illustration shows a close-up of Saturn's rings. These rings are thought to have formed from material that was unable to form into a Moon because of tidal forces from Saturn, or from a Moon that was broken up by Saturn's tidal forces.

  6. Saturn's Rings

    Science.gov (United States)

    Cuzzi, J. N.

    2014-12-01

    observations: direct measurement of the still-unknown ring mass; direct in-situ sampling of ring particle composition (targeting the iron- or carbon-based red nonicy component); and radar backscattering observations. Cuzzi, J. N. et al. (2010) An Evolving View of Saturn's Dynamic Rings; Science (Inv. Review) 19 March 2010: 327. no. 5972, pp. 1470 - 1475

  7. Saturn Variable Thermosphere

    CERN Document Server

    Strobel, Darrell F; Mueller-Wodarg, Ingo

    2016-01-01

    Our knowledge of Saturns neutral thermosphere is far superior to that of the other giant planets due to Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of 15 solar occultations and 26 stellar occultations analyzed to date. These measurements yield H2 as the dominant species with an upper limit on the H mole fraction of 5 %. Inferred temperatures near the lower boundary are ~ 150 K, rising to an asymptotic value of ~ 400K at equatorial latitudes and increasing with latitude to polar values in the range of 550-600 K. The latter is consistent with a total estimated auroral power input of ~ 10TW generating Joule and energetic particle heating of ~ 5-6TW that is more than an order of magnitude greater than solar EUV/FUV heating. This auroral heating would be sufficient to solve the energy crisis of Saturns thermospheric heating, if it can be efficiently redistributed to low latitudes. The inferred structure of the thermosphere yields poleward directed pressure gradients on equipotential surfaces consi...

  8. Magnetospheric mapping of the dayside UV auroral oval at Saturn using simultaneous HST images, Cassini IMF data, and a global magnetic field model

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2011-07-01

    Full Text Available We determine the field-aligned mapping of Saturn's auroras into the magnetosphere by combining UV images of the southern dayside oval obtained by the Hubble Space Telescope (HST with a global model of the magnetospheric magnetic field. The model is tailored to simulate prevailing conditions in the interplanetary medium, corresponding to high solar wind dynamic pressure and variable interplanetary magnetic field (IMF strength and direction determined from suitably lagged field data observed just upstream of Saturn's dayside bow shock by the Cassini spacecraft. Two out of four images obtained in February 2008 when such simultaneous data are available are examined in detail, exemplifying conditions for northward and southward IMF. The model field structure in the outer magnetosphere and tail is found to be very different in these cases. Nevertheless, the dayside UV oval is found to have a consistent location relative to the field structure in each case. The poleward boundary of the oval is located close to the open-closed field boundary and thus maps to the vicinity of the magnetopause, consistent with previous results. The equatorward boundary of the oval then maps typically near the outer boundary of the equatorial ring current appropriate to the compressed conditions prevailing. Similar results are also found for related images from the January 2004 HST data set. These new results thus show that the mapped dayside UV oval typically spans the outer magnetosphere between the outer part of the ring current and the magnetopause. It does not encompass the region of primary corotation flow breakdown within the inner Enceladus torus.

  9. Contribution of amateur observations to Saturn storm studies

    CERN Document Server

    Delcroix, Marc

    2010-01-01

    Since 2004, Saturn Electrostatic Discharges (SEDs), which are the radio signatures of lightning in Saturn's atmosphere, have been observed by the Cassini Radio and Plasma Wave Science instrument (RPWS). Despite their important time coverage, these observations lack the resolution and positioning given by imaging around visible wavelengths. Amateur observations from Earth have been increasing in quality and coverage since a few years, bringing information on positions, drift rates and shape evolutions of large visible white spots in Saturn's atmosphere. Combining these two complementary sources has brought better analysis of Saturn's storms evolutions.

  10. The Saturn management concept

    Science.gov (United States)

    Bilstein, R. E.

    1974-01-01

    Management of the Saturn launch vehicles was an evolutionary process, requiring constant interaction between NASA Headquarters, the Marshall Space Flight Center (particularly the Saturn 5 Program Office), and the various prime contractors. Successful Saturn management was a blend of the decades of experience of the von Braun team, management concepts from the Army, Navy, Air Force, and Government, and private industry. The Saturn 5 Program Office shared a unique relationship with the Apollo Program Office at NASA Headquarters. Much of the success of the Saturn 5 Program Office was based on its painstaking attention to detail, emphasis on individual responsibilities (backed up by comprehensive program element plans and management matrices), and a high degree of visibility as embodied in the Program Control Center.

  11. Saturn's Polar Atmosphere

    CERN Document Server

    Sayanagi, Kunio M; Dyudina, Ulyana A; Fletcher, Leigh N; Sánchez-Lavega, Agustin; West, Robert A

    2016-01-01

    This book chapter, Saturn's Polar Atmosphere, is to be published by Cambridge University Press as part of a multi-volume work edited by Kevin Baines, Michael Flasar, Norbert Krupp, and Thomas Stallard, entitled "Saturn in the 21st Century." This chapter reviews the state of our knowledge about Saturn's polar atmosphere that has been revealed through Earth- and space-based observation as well as theoretical and numerical modeling. In particular, the Cassini mission to Saturn, which has been in orbit around the ringed planet since 2004, has revolutionized our understanding of the planet. The current review updates a previous review by Del Genio et al (2009; Saturn Atmospheric Structure and Dynamics, Chapter 7 of "Saturn from Cassini-Huygens"), written after Cassini's primary mission phase that ended in 2008, by focusing on the north polar region of Saturn and comparing it to the southern high latitudes. Two prominent features in the northern high latitudes are the northern hexagon and the north polar vortex; we...

  12. Saturn chorus latitudinal variations

    National Research Council Canada - National Science Library

    Menietti, J. D; Hospodarsky, G. B; Shprits, Y. Y; Gurnett, D. A

    2014-01-01

    The variation of propagation properties of whistler mode chorus as a function of latitude is not well known at Saturn but is important for the calculation of pitch angle diffusion and nonlinear growth of chorus...

  13. SMM Observations of Saturn

    Science.gov (United States)

    Schnopper, Herbert; Mushotzky, Richard (Technical Monitor)

    2001-01-01

    During the past year I have participated in a series of team telecons to I plan our observation of Saturn with SMM. The observation, scheduled for this month (September), was canceled and a new observation is being planned for 2002.

  14. Saturn's ionosphere and plasmasphere

    Science.gov (United States)

    Moore, Luke Edward

    2008-01-01

    A number of puzzling phenomena were revealed when the Voyager spacecraft flew past Saturn in 1981 to measure the ionized portions (ionosphere) of its upper atmosphere (thermosphere). Most of these issues have remained unexplained in the intervening 25 years due to a lack of conclusive observational data. With the arrival of Cassini at Saturn in July 2004, however, a new era of observations began, providing the promise of fresh evidence and demanding the development of a contemporary theoretical framework in order to re-examine old mysteries and understand new discoveries. This dissertation presents studies of Saturn's ionosphere and inner plasmasphere based on new time-dependent photochemical and diffusive transport models that solve the ion equations of continuity in one dimension. Calculations are conducted within the overall framework of a self-consistent, three-dimensional general circulation model (GCM) of Saturn's thermosphere, and the results of these studies are combined with GCM results to provide the building blocks of a new comprehensive model, the Saturn-Thermosphere- Ionosphere-Model (STIM). The one-dimensional model calculations are used to constrain and investigate a number of unresolved issues and to make testable predictions based on those investigations. Five primary topics are addressed: (1) the additional loss processes required to bring predicted electron densities into agreement with observations, (2) the discrepancy between theory and observations regarding the diurnal variation of peak electron density, (3) the effects of shadowing by Saturn's rings on its ionosphere, (4) the yet unknown electron and ion temperatures at Saturn, and (5) the ionospheric contribution to Saturn's plasmasphere. The models show that a steady influx of water into Saturn's atmosphere--from its rings or icy satellites--is required to explain observed electron densities. Additionally, the time-variability of the water source may be the cause of frequently observed

  15. OGLE-2012-BLG-0563Lb: a Saturn-mass Planet around an M Dwarf with the Mass Constrained by Subaru AO imaging

    CERN Document Server

    Fukui, A; Sumi, T; Bennett, D P; Bond, I A; Han, C; Suzuki, D; Beaulieu, J -P; Batista, V; Udalski, A; Street, R A; Tsapras, Y; Hundertmark, M; Abe, F; Freeman, M; Itow, Y; Ling, C H; Koshimoto, N; Masuda, K; Matsubara, Y; Muraki, Y; Ohnishi, K; Philpott, L C; Rattenbury, N; Saito, T; Sullivan, D J; Tristram, P J; Yonehara, A; Choi, J -Y; Christie, G W; DePoy, D L; Dong, Subo; Drummond, J; Gaudi, B S; Hwang, K -H; Kavka, A; Lee, C U; McCormick, J; Natusch, T; Ngan, H; Park, H; Pogge, R W; Shin, I-G; Tan, T -G; Yee, J C; Szymański, M K; Pietrzyński, G; Soszyński, I; Poleski, R; Kozłowski, S; Pietrukowicz, P; Ulaczyk, K; Bramich, Ł Wyrzykowski D M; Browne, P; Dominik, M; Horne, K; Ipatov, S; Kains, N; Snodgrass, C; Steele, I A

    2015-01-01

    We report the discovery of a microlensing exoplanet OGLE-2012-BLG-0563Lb with the planet-star mass ratio ~1 x 10^{-3}. Intensive photometric observations of a high-magnification microlensing event allow us to detect a clear signal of the planet. Although no parallax signal is detected in the light curve, we instead succeed at detecting the flux from the host star in high-resolution JHK'-band images obtained by the Subaru/AO188 and IRCS instruments, allowing us to constrain the absolute physical parameters of the planetary system. With the help of a spectroscopic information of the source star obtained during the high-magnification state by Bensby et al. (2013), we find that the lens system is located at 1.3^{+0.6}_{-0.8} kpc from us, and consists of an M dwarf (0.34^{+0.12}_{-0.20} M_sun) orbited by a Saturn-mass planet (0.39^{+0.14}_{-0.23} M_Jup) at the projected separation of 0.74^{+0.26}_{-0.42} AU (close model) or 4.3^{+1.5}_{-2.5} AU (wide model). The probability of contamination in the host star's flux...

  16. Saturn's Visible Aurora

    Science.gov (United States)

    Dyudina, U.; Ingersoll, A. P.; Wellington, D. F.; Ewald, S.; Porco, C.

    2013-12-01

    Cassini camera's movies show Saturn's aurora in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000-1500 km above the cloud tops. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras by [1]. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spiral around the pole, and sometimes double arcs. Auroras are observed at 70-75 degrees both north and south latitude. 10,000-km-scale longitudinal brightness structure can persist for more than 3 days. This structure rotates together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. 1000-km-scale disturbances may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The stability of the longitudinal structure of the aurora in 2009 allowed us to estimate its period of rotation of about 10.65 h. This is consistent with Voyager System III rotation and with the Saturn Kilometric Radiation (SKR) period detected by Cassini at the time of aurora observations. These periods are also close to the rotation period of the lightning storms on Saturn. We discuss those periodicities and their relevance to Saturn's rotation. In April-May 2013 a multi-instrument campaign using Cassini and Earth-based data was monitoring Saturn's aurora. We will discuss the results of this campaign. [1] Aguilar, A. et al. The Electron-Excited Mid-Ultraviolet to Near-Infrared Spectrum of H2: Cross Sections and Transition Probabilities. Astrophys. J. Supp. Ser. 177, 388-407 (2008).

  17. Saturn's magnetospheric refresh rate

    Science.gov (United States)

    Rymer, A. M.; Mitchell, D. G.; Hill, T. W.; Kronberg, E. A.; Krupp, N.; Jackman, C. M.

    2013-06-01

    A 2-3 day periodicity observed in Jupiter's magnetosphere (superposed on the giant planet's 9.5 h rotation rate) has been associated with a characteristic mass-loading/unloading period at Jupiter. We follow a method derived by Kronberg et al. () and find, consistent with their results, that this period is most likely to fall between 1.5 and 3.9 days. Assuming the same process operates at Saturn, we argue, based on equivalent scales at the two planets, that its period should be 4 to 6 times faster at Saturn and therefore display a period of 8 to 18 h. Applying the method of Kronberg et al. for the mass-loading source rates estimated by Smith et al. () based on data from the third and fifth Cassini-Enceladus encounters, we estimate that the expected magnetospheric refresh rate varies from 8 to 31 h, a range that includes Saturn's rotation rate of ~10.8 h. The magnetospheric period we describe is proportional to the total mass-loading rate in the system. The period is, therefore, faster (1) for increased outgassing from Enceladus, (2) near Saturn solstice (when the highest proportion of the rings is illuminated), and (3) near solar maximum when ionization by solar photons maximizes. We do not claim to explain the few percent jitter in period derived from Saturn Kilometric Radiation with this model, nor do we address the observed difference in period observed in the north and south hemispheres.

  18. The Interior of Saturn

    CERN Document Server

    Fortney, Jonathan J; Nettelmann, Nadine; Stevenson, David J; Marley, Mark S; Hubbard, William B; Iess, Luciano

    2016-01-01

    We review our current understanding of the interior structure and thermal evolution of Saturn, with a focus on recent results in the Cassini era. There has been important progress in understanding physical inputs, including equations of state of planetary materials and their mixtures, physical parameters like the gravity field and rotation rate, and constraints on Saturnian free oscillations. At the same time, new methods of calculation, including work on the gravity field of rotating fluid bodies, and the role of interior composition gradients, should help to better constrain the state of Saturn's interior, now and earlier in its history. However, a better appreciation of modeling uncertainties and degeneracies, along with a greater exploration of modeling phase space, still leave great uncertainties in our understanding of Saturn's interior. Further analysis of Cassini data sets, as well as precise gravity field measurements from the Cassini Grand Finale orbits, will further revolutionize our understanding ...

  19. "Saturn" remains in orbit

    Directory of Open Access Journals (Sweden)

    Glushechenko E. N.

    2013-05-01

    Full Text Available The article is dedicated to scientific and production enterprise "Saturn" — since its foundation up to the present day. The authors describe the determining stages of its development and its team’s scientific and technological achievements over the 45-year history of the enterprise.

  20. Saturn's Stratospheric Oxygen Compounds

    Science.gov (United States)

    Romani, Paul N.; Delgado Díaz, Héctor E.; Bjoraker, Gordon; Hesman, Brigette; Achterberg, Richard

    2016-10-01

    There are three known oxygenated species present in Saturn's upper atmosphere: H2O, CO and CO2. The ultimate source of the water must be external to Saturn as Saturn's cold tropopause effectively prevents any internal water from reaching the upper atmosphere. The carbon monoxide and dioxide source(s) could be internal, external, produced by the photochemical interaction of water with Saturn's stratospheric hydrocarbons or some combination of all of these. At this point it is not clear what the external source(s) are.Cassini's Composite InfraRed Spectrometer (CIRS) has detected emission lines of H2O and CO2 (Hesman et al., DPS 2015, 311.16 & Abbas et al. 2013, Ap. J. doi:10.1088/0004-637X/776/2/73) on Saturn. CIRS also retrieves the temperature of the stratosphere using CH4 lines at 7.7 microns. Using CIRS retrieved temperatures, the mole fraction of H2O at the 0.5-5 mbar level can be retrieved and the CO2 mole fraction at ~1-10 mbar. Coupled with ground based observations of CO (Cavalié et al., 2010, A&A, DOI: 10.1051/0004-6361/200912909) these observations provide a complete oxygen compound data set to test photochemical models.Preliminary results will be presented with an emphasis on upper limit analysis to determine the percentage of stratospheric CO and CO2 that can be produced photochemically from CIRS observational constraints on the H2O profile.

  1. Saturn's inner satellites: Orbits, masses, and the chaotic motion of atlas from new Cassini imaging observations

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, N. J.; Murray, C. D. [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS (United Kingdom); Renner, S. [Université Lille 1, Laboratoire d' Astronomie de Lille (LAL), 1 impasse de l' Observatoire, F-59000 Lille (France); Evans, M. W. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate GM{sub Atlas} = (0.384 ± 0.001) × 10{sup −3} km{sup 3} s{sup −2}, a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find GM{sub Prometheus} = (10.677 ± 0.006) × 10{sup −3} km{sup 3} s{sup −2}, GM{sub Pandora} = (9.133 ± 0.009) × 10{sup −3} km{sup 3} s{sup −2}, GM{sub Janus} = (126.51 ± 0.03) × 10{sup −3} km{sup 3} s{sup −2}, and GM{sub Epimetheus} = (35.110 ± 0.009) × 10{sup −3} km{sup 3} s{sup −2}, consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon, and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ∼10 years, and show that its chaotic behavior is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora, and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not

  2. Saturnʼs Inner Satellites: Orbits, Masses, and the Chaotic Motion of Atlas from New Cassini Imaging Observations

    Science.gov (United States)

    Cooper, N. J.; Renner, S.; Murray, C. D.; Evans, M. W.

    2015-01-01

    We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate G{{M}Atlas} = (0.384 ± 0.001) × 10-3 km3 s-2, a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find G{{M}Prometheus} = (10.677 ± 0.006) × 10-3 km3 s-2, G{{M}Pandora} = (9.133 ± 0.009) × 10-3 km3 s-2, G{{M}Janus} = (126.51 ± 0.03) × 10-3 km3 s-2, and G{{M}Epimetheus} = (35.110 ± 0.009) × 10-3 km3 s-2, consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon, and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ˜10 years, and show that its chaotic behavior is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora, and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not confined to times of apse anti-alignment.

  3. Saturn Ring Data Analysis and Thermal Modeling

    Science.gov (United States)

    Dobson, Coleman

    2011-01-01

    CIRS, VIMS, UVIS, and ISS (Cassini's Composite Infrared Specrtometer, Visual and Infrared Mapping Spectrometer, Ultra Violet Imaging Spectrometer and Imaging Science Subsystem, respectively), have each operated in a multidimensional observation space and have acquired scans of the lit and unlit rings at multiple phase angles. To better understand physical and dynamical ring particle parametric dependence, we co-registered profiles from these three instruments, taken at a wide range of wavelengths, from ultraviolet through the thermal infrared, to associate changes in ring particle temperature with changes in observed brightness, specifically with albedos inferred by ISS, UVIS and VIMS. We work in a parameter space where the solar elevation range is constrained to 12 deg - 14 deg and the chosen radial region is the B3 region of the B ring; this region is the most optically thick region in Saturn's rings. From this compilation of multiple wavelength data, we construct and fit phase curves and color ratios using independent dynamical thermal models for ring structure and overplot Saturn, Saturn ring, and Solar spectra. Analysis of phase curve construction and color ratios reveals thermal emission to fall within the extrema of the ISS bandwidth and a geometrical dependence of reddening on phase angle, respectively. Analysis of spectra reveals Cassini CIRS Saturn spectra dominate Cassini CIRS B3 Ring Spectra from 19 to 1000 microns, while Earth-based B Ring Spectrum dominates Earth-based Saturn Spectrum from 0.4 to 4 microns. From our fits we test out dynamical thermal models; from the phase curves we derive ring albedos and non-lambertian properties of the ring particle surfaces; and from the color ratios we examine multiple scattering within the regolith of ring particles.

  4. Tesseral resonances in the rings of Saturn

    Science.gov (United States)

    El Moutamid, Maryame; Nicholson, Philip D.; Hedman, Matthew M.; Gierasch, Peter J.; Burns, Joseph A.; French, Richard G.

    2016-05-01

    We will present a study of the behavior of the A, B, C and D rings using images and occultation data obtained by the Cassini spacecraft over a period of 8 years from 2006 to 2015. We have identified a variety of free and forced normal modes at the edge of the A ring, with values of ''m'' ranging from 3 to 18 and appropriate pattern speeds (El Moutamid et al, 2016). These modes may represent waves trapped in resonant cavities at the edge (Spitale and Porco 2010, Nicholson et al 2014). Moreover, Hedman et al. (2009) have identified structures in the D ring and the Roche division which appear to rotate with Saturn. These may represent Tesseral resonances associated with inhomogeneities in Saturn's interior.We are now searching for wave-like signatures in the main rings which are not associated with edges but also related to the rotation period of Saturn. We have identified several signatures consistent with other Tesseral resonances. These signatures may provide information about differential rotation in Saturn's interior.

  5. A CHANGE OF SEASONS ON SATURN

    Science.gov (United States)

    2002-01-01

    Looming like a giant flying saucer in our outer solar system, Saturn puts on a show as the planet and its magnificent ring system nod majestically over the course of its 29-year journey around the Sun. These Hubble Space Telescope images, captured from 1996 to 2000, show Saturn's rings open up from just past edge-on to nearly fully open as it moves from autumn towards winter in its Northern Hemisphere. Saturn's equator is tilted relative to its orbit by 27 degrees, very similar to the 23-degree tilt of the Earth. As Saturn moves along its orbit, first one hemisphere, then the other is tilted towards the Sun. This cyclical change causes seasons on Saturn, just as the changing orientation of Earth's tilt causes seasons on our planet. The first image in this sequence, on the lower left, was taken soon after the autumnal equinox in Saturn's Northern Hemisphere (which is the same as the spring equinox in its Southern Hemisphere). By the final image in the sequence, on the upper right, the tilt is nearing its extreme, or winter solstice in the Northern Hemisphere (summer solstice in the Southern Hemisphere). Astronomers are studying this set of images to investigate the detailed variations in the color and brightness of the rings. They hope to learn more about the rings' composition, how they were formed, and how long they might last. Saturn's rings are incredibly thin, with a thickness of only about 30 feet (10 meters). The rings are made of dusty water ice, in the form of boulder-sized and smaller chunks that gently collide with each other as they orbit around Saturn. Saturn's gravitational field constantly disrupts these ice chunks, keeping them spread out and preventing them from combining to form a moon. The rings, as shown here, have a slight pale reddish color due to the presence of organic material mixed with the water ice. Saturn is about 75,000 miles (120,000 km) across, and is flattened at the poles because of its very rapid rotation. A day is only 10 hours

  6. Intrinsic structure in Saturn's rings

    Science.gov (United States)

    Albers, N.

    2015-10-01

    Saturn's rings are the most prominent in our Solar system and one example of granular matter in space. Dominated by tides and inelastic collisions the system is highly flattened being almost 300000km wide while only tens of meters thick. Individual particles are composed of primarily water ice and range from microns to few tens of meters in size. Apparent patterns comprise ringlets, gaps, kinematic wakes, propellers, bending waves, and the winding spiral arms of density waves. These large-scale structures are perturbations foremost created by external as well as embedded moons. Observations made by the Cassini spacecraft currently in orbit around Saturn show these structures in unprecedented detail. But high-resolution measurements reveal the presence of small-scale structures throughout the system. These include self-gravity wakes (50-100m), overstable waves (100-300m), subkm structure at the A and B ring edges, "straw" and "ropy" structures (1-3km), and the C ring "ghosts". Most of these had not been anticipated and are found in perturbed regions, driven by resonances with external moons, where the system undergoes periodic phases of compression and relaxation that correlate with the presence of structure. High velocity dispersion and the presence of large clumps imply structure formation on time scales as short as one orbit (about 10 hours). The presence of these intrinsic structures is seemingly the response to varying local conditions such as internal density, optical depth, underlying particle size distribution, granular temperature, and distance from the central planet. Their abundance provides evidence for an active and dynamic ring system where aggregation and fragmentation are ongoing on orbital timescales. Thus a kinetic description of the rings may be more appropriate than the fluid one. I will present Cassini Ultraviolet Spectrometer (UVIS) High Speed Photometer (HSP) occultations, Voyager 1 and 2 Imaging Science Subsystem (ISS), and high

  7. The moons of Saturn

    Science.gov (United States)

    Soderblom, L. A.; Johnson, T. V.

    1982-01-01

    Knowledge gained of the 17 Saturn moons with observations by the Voyager spacecraft are reviewed. Titan was found to have the only atmosphere, which is opaque and precludes geologic inferences. Synchronous rotation is experienced by the 14 inner moons, with a constant inner face turned toward the planet. Phoebe is too far away from the planet to lose its spin to planetary tidal forces, and has an orbit inclined 150 deg from the equatorial plane, while Iapetus is inclined 14.7 deg in its orbit. The abundance of ice on the moons is accepted as evidence of condensation formation of the moons at very low temperatures. Newly discovered moons of Saturn, including both the shepherd moons, which are suspected to maintain the rings in place, and the moons discovered by earth-based astronomy, are discussed. Finally, photographs of all the moons are examined for definitive details.

  8. Titan Saturn System Mission

    Science.gov (United States)

    Reh, Kim R.

    2009-01-01

    Titan is a high priority for exploration, as recommended by NASA's 2006 Solar System Exploration (SSE) Roadmap. NASA's 2003 National Research Council (NRC) Decadal Survey and ESA's Cosmic Vision Program Themes. Recent revolutionary Cassini-Huygens discoveries have dramatically escalated interest in Titan as the next scientific target in the outer solar system. This study demonstrates that an exciting Titan Saturn System Mission (TSSM) that explores two worlds of intense astrobiological interest can be initiated now as a single NASA/ESA collaboration.

  9. Saturn's largest ring.

    Science.gov (United States)

    Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

    2009-10-22

    Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus.

  10. Localized Perturbations in Saturn's C Ring

    Science.gov (United States)

    Spitale, Joseph N.; Tiscareno, Matthew S.

    2016-10-01

    Years of high-resolution imaging of Saturn's rings have revealed many examples of perturbations arising from local causes. For example, the presence of 100-m-scale and smaller moonlets is inferred in the A ring based on the propeller-shaped disturbances that they create (Tiscareno et al. 2006, 2010); the F ring is shaped by regular collisions with its shepherd Prometheus, as well as with other smaller bodies orbiting in the vicinity (Murray et al. 2005, 2008); the "wisps" on the outer edge of the Keeler gap (Porco et al. 2005) may mark the locations of small moonlets that have emerged from the A ring (Tiscareno and Arnault 2015); wakes in the Huygens ringlet imply the presence of two multi-km bodies, and the irregular shape of its inner edge suggests the presence of many smaller bodies (Spitale and Hahn 2016); based on shadow measurements, the B ring contains an embedded 300-m object that produces a small propeller-shaped disturbance (Spitale and Porco 2010; Spitale and Tiscareno 2012).Here, we present evidence for localized perturbations in the C ring. The ringlet embedded in the Bond gap, near 1.470 Saturn radii, shows discrete clumps orbiting at the Keplerian rate in images spanning about eight years. The clumps are not detected in all image sequences at the expected longitudes. The Dawes ringlet, near 1.495 Saturn radii, has an irregular edge that does not appear as a simple superposition of low-wavenumber normal modes.

  11. Theory about Atlas morphology (Saturn moon)

    CERN Document Server

    Romay, Enrique Ordaz

    2007-01-01

    On June 12, 2007 the Cassini probe sent the images of a small moon of Saturn called Atlas which is located between the ring A and the small ring R/2004 S 1. These images have shown that the Atlas morphology is very different from other moons of similar dimensions. In the present article we propose a reasonable theory, to that we denominated "flying dune", that explains its morphologic characteristics from its magnitudes like mass, diameters and orbital radius, as well as its orbital position and the interpretation of the images caught by the Cassini probe.

  12. Size and shape of Saturn's moon Titan

    Science.gov (United States)

    Zebker, Howard A.; Stiles, Bryan; Hensley, Scott; Lorenz, Ralph; Kirk, Randolph L.; Lunine, Jonathan

    2009-01-01

    Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 ± 0.05 kilometers (km), 2574.36 ± 0.03 km, and 2574.91 ± 0.11 km, respectively; its mean radius is 2574.73 ± 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most—but not all—of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

  13. Saturn's F-ring and inner satellite

    Science.gov (United States)

    1981-01-01

    Saturn's F-ring and its inner shepherding satellite (1980S27) are pictured in this closeup Voyager 2 image acquired Aug. 25 from a range of 365,000 kilometers (227,000 miles). Features as small as 6 km. (3.7 mi.) across are visible. The satellite is elongated and irregular, with its longest axis pointing toward the center of Saturn (toward the upper right in this view). As seen here, the F-ring is thin and does not show the multiple, braided structure Voyager 1 saw last fall. Nor is there any indication of a band or kink in the ring at its closest point to the shepherd; such a feature would be consistent with some of the theories advanced on the formation of the braids. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  14. Plasmapause formation at Saturn

    Science.gov (United States)

    Thomsen, M. F.; Mitchell, D. G.; Jia, X.; Jackman, C. M.; Hospodarsky, G.; Coates, A. J.

    2015-04-01

    Cassini observations during a rapid, high-latitude, dawnside pass from Saturn's lobe to inner magnetosphere on 25 June 2009 provide strong evidence for the formation of a "plasmapause" at Saturn by Vasyliunas-type nightside reconnection of previously mass-loaded flux tubes. A population of hot, tenuous plasma that lies between the lobe and the dense inner magnetospheric plasma is consistent with a region formed by very recent injection from a reconnection region in the tail, including low density, high temperature, supercorotational flow, a significant O+ content, and the near-simultaneous observation of enhanced Saturn kilometric radiation emissions. The sharp boundary between that region and the cool dense inner magnetospheric plasma thus separates flux tubes that were involved in the reconnection from those that successfully traversed the nightside without mass loss. This event demonstrates that tail reconnection can strip off inner magnetospheric plasma in to at least dipole L = 8.6. Clear evidence of flux tube interchange driven by the sharp boundary is found, both inward moving flux tubes of hotter plasma and, for the first time, the outward moving cool population. The outward moving cool regions have azimuthal sizes less than 1 RS, were probably created within the past 1.2 h, and have outflow speeds greater than about 5 km/s. At the outer edge of the reconnected region, there is also a possible signature of Dungey-type lobe reconnection following the initial Vasyliunas-type reconnection. Observations from this event are entirely consistent with previously described global MHD simulations of tail reconnection, plasmoid departure, and Saturnward injection of reconnected flux.

  15. Saturn's rings - high resolution

    Science.gov (United States)

    1981-01-01

    Voyager 2 obtained this high-resolution picture of Saturn's rings Aug. 22, when the spacecraft was 4 million kilometers (2.5 million miles) away. Evident here are the numerous 'spoke' features, in the B-ring; their very sharp, narrow appearance suggests short formation times. Scientists think electromagnetic forces are responsible in some way for these features, but no detailed theory has been worked out. Pictures such as this and analyses of Voyager 2's spoke movies may reveal more clues about the origins of these complex structures. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  16. Formation of Saturn's spokes

    Science.gov (United States)

    Goertz, C. K.

    1984-01-01

    The theoretical requirements of the Goertz and Morfill (1983) model of the formation of spokes in the rings of Saturn are analyzed. Consideration is given to model predictions of dust particle size distribution, the optical depth of the spokes, and the radial speed of spoke evolution. It is shown that the electrostatic levitation of singly charged dust particles would be sufficient to cause the spokes to form. The maximum formation time for spokes of more than 10,000 km radial length is estimated to be less than five minutes. Observations of the scattering properties of the spokes showed general agreement with the theoretical calculations.

  17. Saturn's Other Ring Current

    Science.gov (United States)

    Crary, F. J.

    2014-04-01

    Saturn's main rings orbit the planet within an atmosphere and ionosphere of water, oxygen and hydrogen, produced by meteoritic impacts on and ultraviolet photodesorbtion of the ring particles [Johnson et al., 2006; Luhmann et al., 2006; Tseng et al., 2010]. The neutral atmosphere itself has only been tentatively detected through ultraviolet fluorescents of OH [Hall et al., 1996] while the ionosphere was observed in situ by the Cassini spacecraft shortly after orbital insertion [Coates et al.,2005; Tokar et al. 2005, Waite et al. 2005]. Although the plasma flow velocity of this ionosphere is not well-constrained, but the close association with the rings suggests that its speed would be couppled to the keplarian velocity of the rings themselves. As a result, the motion of the plasma through Saturn's magnetic field would produce an induced voltage, oriented away from the planet outside synchronous orbit and towards the planet inside synchronous orbit. Such a potential could result in currents flowing across the ring plane and closeing along magnetic field lines and through Saturn's ionosphere at latitudes between 36o and 48o. Cassini observations of whistler-mode plasma wave emissions [Xin et al.,2006] centered on synchronous orbit (1.76 Rs, mapping to 41o latitude) have been interpreted as a product of field-aligned electron beams associated with such a current. This presentation will investigate the magnitude of these currents and the resulting Joule heating of the ionosphere. An important constraint is that no auroral ultraviolet emissions have been observed at the relevant latitudes. In contrast, Joule heating could affect infrared emissions from H3+. Variations in H3+ emission associated with Saturn's rings have been reported by O'Donoghue et al., 2013, and interpreted as a result of ring "rain", i.e. precipitating water group species from the rings which alter ionosphereic chemistry and H3+ densities. As noted by O'Donoghue et al., this interpretation may be

  18. Saturn's rings revisited by the images of the CASSINI spacecraft: Dynamical evolution of the F ring and photometric study of the main rings

    Science.gov (United States)

    Deau, E.

    2007-12-01

    In the Solar system, the planetary rings represent a fantastic opportunity of studying a majority of phenomena taking place in the thin discs. One can find discs at all redshifts and on all scales of the Universe. Planetary discs are very different~: among the jovian rings, one finds a halo of fine and diffuse dust; the rings of Uranus are very compact, like radially confined strings and the system of rings of Neptune consists of azimuthally stable arcs. However our interest goes on Saturn which has the most complex and widest system of rings known to date~: 484.000 km and a vertical extension which increases with the distance to Saturn (typically less than 1km to 10.000 km). The interest of such a matter organization around Saturn plus its many moons (more than one forty including 8 of a size of several hundreds kilometers) gave birth to the exploration mission CASSINI, supposed to allow the development and the refinement of models set up at the flybies of the two interplanetary probes VOYAGER. The CASSINI Mission began its nominal tour on january, 15th 2005 after the orbital insertion the 1st july 2004 and the dropping of HUYGENS probe on january, 14th 2005 on Titan's surface. The purpose of this thesis consists to revisite two subjects unsolved of long date in the photometric and dynamic behaviours of the Saturn's rings. In a first part, we try to solve the problem of accretion of matter within the Roche limit by studying the F ring. This ring, since its discovery in 1979 by Pioneer 11, is involved in a most various dynamic theories to explain its complex multi-radial structure and its variable azimuthal structure. We showed that the multi-radial structure of this ring can be understood by the existence of a spiral which is rolled up around a central area, bright, eccentric and inclined~: the core. The lifespan of this spiral is not the same one as the core, suggesting that the processes which create the spiral are periodic. Moreover, we showed that the

  19. Accretion in Saturn's F Ring

    Science.gov (United States)

    Meinke, B. K.; Esposito, L. W.; Stewart, G.

    2012-12-01

    Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

  20. Condensation in Saturn's Stratospheric Haze Layers

    Science.gov (United States)

    Barth, Erika L.; Moses, Julianne I.

    2016-10-01

    Haze particles in Saturn's stratosphere can be seen in the visible limb images of Cassini's Imaging Science Subsystem (ISS). These hazes are likely a mix of particles, including solid organics formed as a result of methane photolysis and electron deposition, as well as the condensation of water and hydrocarbon ices. We have examined data from both Cassini and Voyager to study the detailed vertical structure of absorbing/scattering particulates in Saturn's stratosphere and developed a Saturn version of the Community Aerosol and Radiation Model for Atmospheres (CARMA), adding a large database of hydrocarbons that are observed or expected to be present in Saturn's atmosphere.Our modeling indicates that water ice condenses independently of the hydrocarbons to form a thin layer above the 0.1 mbar pressure level. Between about 5 and 50 mbar, the hydrocarbons reach their condensation levels (in order of increasing pressure level): C6H6, C5H12, C4H2, C4H10, and C2H2. Because of the proximity of their condensation levels and due to the gravitational settling of the particles, the hydrocarbons are likely condensing on one another and forming a thicker layer of mixed composition. Interestingly, butane (C4H10) has a triple point around 135 K which is much lower than most of the other condensing species we've explored. Given an approximate condensation level of 10 mbar and the observed temperature changes at this pressure level following the December 2010 northern-hemisphere storm (stratospheric temperatures were elevated by as much as 50-70 K in a region near 40° N latitude.), melting and further nucleation of droplets could be occurring.A number of factors including temperature profile, vapor pressure equation, volatile abundance, nucleation critical saturation, and coagulation efficiency will affect the altitudes of the individual ice layers. We will present a summary of results following the nucleation and growth of compounds in order to quantify the likely size and

  1. Pioneer fly-by of Saturn and its rings

    Science.gov (United States)

    Gehrels, T.; Esposito, L.

    1981-01-01

    Results acquired by the imaging photopolarimeter on board Pioneer 11 during the spacecraft fly-by of Saturn and its rings on September 1, 1979 are reviewed. Analysis of the broadband photometry and polarimetry obtained of the Saturn atmosphere has been used to determine a cloud top height of 300 mb and a scale height of the aerosol distribution about 1/4 that of the ambient gas, and to point out differences between the forward scattering and belt and zone characteristics of the Saturn and Jupiter atmospheres. Images of Saturn's rings have been used to derive a profile of ring optical depth between 1.22 and 2.35 Saturn radii, and reveal new divisions and thin rings and azimuthal variations in the brightness of the A ring not observable from earth. Linear polarization observations of Titan in red and blue light reveal that the aerosols near the top of the atmosphere have radii less than about 0.09 micron and that the optical thickness of the small aerosol layer is about 0.6 above an effectively depolarizing surface, and indicate radii of 2845 + or - 25 km and 2880 + or - 22 km in red and blue light, respectively. Earth-based and spacecraft data are consistent with the formation of rings structures as a result of Poynting-Robertson drag and gravitational satellite resonances with the original ice and rock particles.

  2. Saturn's Stratospheric Water Vapor Distribution

    Science.gov (United States)

    Hesman, B. E.

    2015-12-01

    Water is a sought after commodity in the solar system. It is used as an indication of life, planetary formation timescales, and signatures of past cometary impacts. In Saturn's atmosphere there are two sources of water: an internal primordial reservoir that is confined to the troposphere, and an external source of unknown origin that delivers water to the stratosphere. Potential sources of stratospheric water include: Saturn's main rings (via neutral infall and/or ions transported along magnetic field lines - "Ring Rain"), interplanetary dust particles, and the E-ring that is supplied with water from the plumes of Enceladus. Measuring the latitudinal and seasonal variation of H2O on Saturn will constrain the source of Saturn's stratospheric water. Cassini's Composite InfraRed Spectrometer (CIRS) has detected emission lines of H2O on Saturn at wavelengths of 40 and 50 microns. CIRS also retrieves the temperature of the stratosphere using CH4 lines at 7.7 microns. Using our retrieved temperatures, we derive the mole fraction of H2O at the 0.5-5 mbar level for comparison with water-source models. The latitudinal variation of stratospheric water vapor between 2004-2009 will be presented as a first step in understanding the external source of water on Saturn. The observed local maximum near Saturn's equator supports either a neutral infall from the rings or a source in the E-ring. We will look for secondary maxima at mid-latitudes to determine whether "Ring Rain" also contributes to the inventory of water in Saturn's upper atmosphere.

  3. Dynamics of Saturn's great storm of 2010-2011 from Cassini ISS and RPWS

    CERN Document Server

    Sayanagi, Kunio M; Ewald, Shawn P; Fischer, Georg; Ingersoll, Andrew P; Kurth, William S; Muro, Gabriel D; Porco, Carolyn C; West, Robert A

    2016-01-01

    Saturn's quasi-periodic planet-encircling storms are the largest convecting outbursts in the Solar System. The last eruption was in 1990. A new eruption started in December 2010 and presented the first-ever opportunity to observe such episodic storms from a spacecraft in orbit around Saturn. Here, we analyze images acquired with the Cassini Imaging Science Subsystem (ISS), which captured the storm's birth, evolution and demise. In studying the end of the convective activity, we also analyze the Saturn Electrostatic Discharge (SED) signals detected by the Radio and Plasma Wave Science (RPWS) instrument. [...

  4. Jupiter and Saturn Rotation Periods

    CERN Document Server

    Helled, Ravit; Anderson, John D

    2009-01-01

    Anderson & Schubert (2007, Science,317,1384) proposed that Saturn's rotation period can be ascertained by minimizing the dynamic heights of the 100 mbar isosurface with respect to the geoid; they derived a rotation period of 10h 32m 35s. We investigate the same approach for Jupiter to see if the Jovian rotation period is predicted by minimizing the dynamical heights of its isobaric (1 bar pressure level) surface using zonal wind data. A rotation period of 9h 54m 29s is found. Further, we investigate the minimization method by fitting Pioneer and Voyager occultation radii for both Jupiter and Saturn. Rotation periods of 9h 55m 30s and 10h 32m 35s are found to minimize the dynamical heights for Jupiter and Saturn, respectively. Though there is no dynamical principle requiring the minimization of the dynamical heights of an isobaric surface, the successful application of the method to Jupiter lends support to its relevance for Saturn. We derive Jupiter and Saturn rotation periods using equilibrium theory in ...

  5. 7. Saturne study meeting; Septiemes journees d`etudes saturne

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-12-31

    This Saturne workshop has welcomed 120 scientists. 3 sessions have been organized: accelerators, physics and miscellaneous. The most recent experiments realized or scheduled at Saturne have been presented and the discussions which followed showed the high scientific interest taken in that equipment and made the participants regret its definitive closing down. Presentations by european teams about existent equipment, machines under construction or new projects opened the way to new perspectives. A lot of contributions were dedicated to the realization of high intensity particle beams and to the applications of accelerators. (A.C.)

  6. An Explanation for Saturn's Hexagon

    Science.gov (United States)

    Kohler, Susanna

    2015-08-01

    For over three decades, weve been gathering observations of the mysterious hexagonal cloud pattern encircling Saturns north pole. Now, researchers believe they have a model that can better explain its formation.Fascinating GeometrySaturns northern Hexagon is a cloud band circling Saturns north pole at 78 N, first observed by the Voyager flybys in 198081. This remarkable pattern has now persisted for more than a Saturn year (29.5 Earth years).Eight frames demonstrating the motion within Saturns Hexagon. Click to watch the animation! The view is from a reference frame rotating with Saturn. [NASA/JPL-Caltech/SSI/Hampton University]Observations by Voyager and, more recently, Cassini have helped to identify many key characteristics of this bizarre structure. Two interesting things weve learned are:The Hexagon is associated with an eastward zonal jet moving at more than 200 mph.The cause of the Hexagon is believed to be a jet stream, similar to the ones that we experience on Earth. The path of the jet itself appears to follow the hexagons outline.The Hexagon rotates at roughly the same rate as Saturns overall rotation.While we observe individual storms and cloud patterns moving at different speeds within the Hexagon, the vertices of the Hexagon move at almost exactly the same rotational speed as that of Saturn itself.Attempts to model the formation of the Hexagon with a jet stream have yet to fully reproduce all of the observed features and behavior. But now, a team led by Ral Morales-Juberas of the New Mexico Institute of Mining and Technology believes they have created a model that better matches what we see.Simulating a Meandering JetThe team ran a series of simulations of an eastward, Gaussian-profile jet around Saturns pole. They introduced small perturbations to the jet and demonstrated that, as a result of the perturbations, the jet can meander into a hexagonal shape. With the initial conditions of the teams model, the meandering jet is able to settle into a

  7. Saturn from Cassini-Huygens

    CERN Document Server

    Dougherty, Michele K; Krimigis, Stamatios M

    2009-01-01

    This book reviews our current knowledge of Saturn featuring the latest results obtained by the Cassini-Huygens mission. A global author team addresses the planet’s origin and evolution, internal structure, composition and chemistry, the atmosphere and ionosphere, the magnetosphere, as well as its ring system. Furthermore, Saturn's icy satellites are discussed. The book closes with an outlook beyond the Cassini-Huygens mission. Colorfully illustrated, this book will serve as a reference to researchers as well as an introduction for students.

  8. IR spectra of Saturn's ring spokes and multiple shines in the Saturn-rings system

    Science.gov (United States)

    D'Aversa, Emiliano; Bellucci, Giancarlo; Filacchione, Gianrico; Cerroni, Priscilla; Nicholson, Phil D.; Carrozzo, Filippo G.; Altieri, Francesca; Oliva, Fabrizio; Geminale, Anna; Sindoni, Giuseppe; Hedman, Matthew M.

    2017-04-01

    During the last Saturn equinox, in 2009 August, spokes on the Saturn's B ring have been observed for the first time spectroscopically, at visible and infrared wavelengths. Measurements were obtained by Cassini-VIMS (Visual and Infrared Mapping Spectrometer) instrument in the 0.35-5.1 micron range. Spokes are either dark or bright features appearing on the B ring straddling the equinoxes, round to elongated in shape, lasting for minutes to hours, and moving partially pushed by Saturn's magnetic field. Previous spokes observations date back to the Voyager (1980 equinox,[1]), followed by a HST campaign (1995 equinox,[2]), and more recently Cassini-ISS images (2009 equinox,[3]). Theoretical models of spoke formation and evolution have been developed based on those observations, but there is not unanimous consensus on them. The most spread model considers the spoke as a cloud of very fine particles electrostatically levitating from the regolith of ring's boulders, and hovering on the ring plane while interacting with the ambient plasma until complete charge neutralization. The process triggering the grain charging is not yet clear (meteoroid bombardment, impacts of Saturn's lightnings electrons, etc.) but in any case a very small grain mass (high charge-to-mass ratio) is needed to allow electrostatic repulsion. From the observational point of view, small grain sizes (0.3-0.5 micron) have been retrieved by modeling the spoke reflectance in the visible spectral range (both Voyager, HST, and Cassini were equipped with multispectral imaging cameras). However, a first VIMS spoke observation ([4]) inferred a more spread size distribution (0.3 to 2.5 microns) to explain the high spoke contrast measured in the infrared. Here we will report about an analysis of two selected sets of spokes observed by VIMS. This selection aimed to include both high and low phase angle observations, and to take advantage from the highest spatial resolution data achieved in the infrared. We will

  9. Cassini Radio and Plasma Wave Observations at Saturn

    Science.gov (United States)

    Gurnett, D. A.; Kurth, W. S.; Hospodarsky, G. B.; Persoon, A. M.; Averkamp, T. F.; Ceccni, B.; Lecacheux, A.; Zarka, P.; Canu, P.; Cornilleau-Wehrlin, N.

    2005-01-01

    Results are presented from the Cassini radio and plasma wave instrument during the approach and first few orbits around Saturn. During the approach the intensity modulation of Saturn Kilometric Radiation (SKR) showed that the radio rotation period of Saturn has increased to 10 hr 45 min plus or minus 36 sec, about 6 min longer than measured by Voyager in 1980-81. Also, many intense impulsive radio signals called Saturn Electrostatic Discharges (SEDs) were detected from saturnian lightning, starting as far as 1.08 AU from Saturn, much farther than terrestrial lightning can be detected from Earth. Some of the SED episodes have been linked to cloud systems observed in Saturn s atmosphere by the Cassini imaging system. Within the magnetosphere plasma wave emissions have been used to construct an electron density profile through the inner region of the magnetosphere. With decreasing radial distance the electron density increases gradually to a peak of about 100 per cubic centimeter near the outer edge of the A ring, and then drops precipitously to values as low as .03 per cubic centimeter over the rings. Numerous nearly monochromatic whistler-mode emissions were observed as the spacecraft passed over the rings that are believed to be produced by meteoroid impacts on the rings. Whistlermode emissions, similar to terrestrial auroral hiss were also observed over the rings, indicating that an electrodynamic interaction, similar to auroral particle acceleration, may be occurring in or near the rings. During the Titan flybys Langmuir probe and plasma wave measurements provided observations of the density and temperature in Titan's ionosphere.

  10. DISCOVERY OF A DARK AURORAL OVAL ON SATURN

    Science.gov (United States)

    2002-01-01

    The ultraviolet image was obtained by the NASA/ESA Hubble Space Telescope with the European Faint Object Camera (FOC) on June 1992. It represents the sunlight reflected by the planet in the near UV (220 nm). * The image reveals a dark oval encircling the north magnetic pole of Saturn. This auroral oval is the first ever observed for Saturn, and its darkness is unique in the solar system (L. Ben-Jaffel, V. Leers, B. Sandel, Science, Vol. 269, p. 951, August 18, 1995). The structure represents an excess of absorption of the sunlight at 220 nm by atmospheric particles that are the product of the auroral activity itself. The large tilt of the northern pole of Saturn at the time of observation, and the almost perfect symmetry of the planet's magnetic field, made this observation unique as even the far side of the dark oval across the pole is visible! * Auroral activity is usually characterized by light emitted around the poles. The dark oval observed for Saturn is a STUNNING VISUAL PROOF that transport of energy and charged particles from the magnetosphere to the atmosphere of the planet at high latitudes induces an auroral activity that not only produces auroral LIGHT but also UV-DARK material near the poles: auroral electrons are probably initiating hydrocarbon polymer formation in these regions. Credits: L. Ben Jaffel, Institut d'Astrophysique de Paris-CNRS, France, B. Sandel (Univ. of Arizona), NASA/ESA, and Science (magazine).

  11. Spallation neutron experiment at SATURNE

    Energy Technology Data Exchange (ETDEWEB)

    Meigo, Shin-ichiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-11-01

    The double differential cross sections for (p,xn) reactions and the spectra of neutrons produced from the thick target have been measured at SATURNE in SACLAY from 1994 to 1997. The status of the experiment and the preliminary experimental results are presented. (author)

  12. Possible origin of the Saturn satellite, Phoebe

    Science.gov (United States)

    Di Sisto, R. P.; Brunini, A.

    The orbit of the outermost Saturn's irregular moon, Phoebe, suggests that it was captured by Saturn rather than formed in situ. The Cassini-Huygens mission results allowed to find that Phoebe's composition is similar to that derived for the outer solar system bodies and very different from the composition of the Saturn regular satellites. In this paper we present new results suggesting that Phoebe could be a component of a binary centaur captured by Saturn during a three-body gravitational encounter. FULL TEXT IN SPANISH

  13. Saturn Chorus as a Function of Latitude

    Science.gov (United States)

    Menietti, J. D.; Hospodarsky, G. B.; Gurnett, D. A.; Shprits, Y.

    2013-12-01

    Not only the dust but also the spatial scale of Saturn, including the background magnetic field inhomogeneity, make the study of whistler mode plasma wave emissions at Saturn quite different from Earth. The significant decrease in chorus intensity nearest the Saturn magnetic equator along a nearly constant L shell has already been reported. In the current study we analyze all known examples of these data and report the collective functional dependence of chorus intensity and wave normal angle, as well as density and magnetic inhomogeneity versus latitude. These values are important in the modeling of pitch angle scattering and possible electron acceleration at Saturn.

  14. The detection of benzene in Saturn's upper atmosphere

    Science.gov (United States)

    Koskinen, T. T.; Moses, J. I.; West, R. A.; Guerlet, S.; Jouchoux, A.

    2016-08-01

    The stratosphere of Saturn contains a photochemical haze that appears thicker at the poles and may originate from chemistry driven by the aurora. Models suggest that the formation of hydrocarbon haze is initiated at high altitudes by the production of benzene, which is followed by the formation of heavier ring polycyclic aromatic hydrocarbons. Until now there have been no observations of hydrocarbons or photochemical haze in the production region to constrain these models. We report the first vertical profiles of benzene and constraints on haze opacity in the upper atmosphere of Saturn retrieved from Cassini Ultraviolet Imaging Spectrograph stellar occultations. We detect benzene at several different latitudes and find that the observed abundances of benzene can be produced by solar-driven ion chemistry that is enhanced at high latitudes in the northern hemisphere during spring. We also detect evidence for condensation and haze at high southern latitudes in the polar night.

  15. Saturn's magnetosphere: An example of dynamic planetary systems

    Science.gov (United States)

    Krimigis, Stamatios M.

    2011-01-01

    Planetary magnetospheres are prime examples of interacting plasma regimes at different scales. There is the principal interaction with the solar wind that seems to be the main driver of the dynamics at Mercury and Earth. But these inner planet magnetospheres are relatively simple when compared to those of the outer planets which are primarily driven by planetary rotation and include internal plasma sources from various moons and rings, in addition to those from the planetary ionospheres and the solar wind. Io's volcanic source at Jupiter is a prime example, but now Enceladus at Saturn has joined the fray, while Titan is a surprisingly minor player despite its thick nitrogen atmosphere and its continued bombardment by energetic particles. Mass loading of plasma leads to interchange instability in the inner magnetospheres at both Jupiter and Saturn, while ionospheric slippage, among other processes, seems to contribute to a variable rotation period in the spin-aligned dipole field of Saturn, manifested in auroral kilometric radiation (SKR), components of the magnetic field itself, and the plasma periodicities measured at several energies. Through use of the ENA (energetic neutral atom) technique, it is now possible to observe bulk motions of the plasma and their connection to planetary auroral processes. Such imaging at Saturn by Cassini has revealed the location of a region of post-midnight acceleration events that seem to corotate with the planet and coincide with auroral brightening and SKR. Periodic injections of plasma have been identified and repeat at the Kronian rotation period of 10.8 hours. A semi-permanent but asymmetric ring current has also been imaged, located between the orbits of the satellites Rhea (~9 RS) and Titan (~20 RS), with a maximum at ~10+/- 1RS and dominated by the hot (>3 keV) plasma component.

  16. Physical and Statistical Modeling of Saturn's Troposphere

    Science.gov (United States)

    Yanamandra-Fisher, Padmavati A.; Braverman, Amy J.; Orton, Glenn S.

    2002-12-01

    The 5.2-μm atmospheric window on Saturn is dominated by thermal radiation and weak gaseous absorption, with a 20% contribution from sunlight reflected from clouds. The striking variability displayed by Saturn's clouds at 5.2 μm and the detection of PH3 (an atmospheric tracer) variability near or below the 2-bar level and possibly at lower pressures provide salient constraints on the dynamical organization of Saturn's atmosphere by constraining the strength of vertical motions at two levels across the disk. We analyse the 5.2-μm spectra of Saturn by utilising two independent methods: (a) physical models based on the relevant atmospheric parameters and (b) statistical analysis, based on principal components analysis (PCA), to determine the influence of the variation of phosphine and the opacity of clouds deep within Saturn's atmosphere to understand the dynamics in its atmosphere.

  17. Origin and Evolution of the Saturn System

    Science.gov (United States)

    Pollack, J. B.

    1985-01-01

    As was the case for Jupiter, Saturn formed either as a result of a gas instability within the solar nebula or the accretion of a solid core that induced an instability within the surrounding solar nebula. In either case, the protoplanet's history can be divided into three major stages: early, quasi-hydrostatic evolution (stage 1); very rapid contraction (stage 2); and late, quasi-hydrostatic contraction (stage 3). During the early history of the Saturn system, giant impact events may have catastrophically disrupted most of the original satellites of Saturn. Such disruption, followed by reaccretion, may be responsible, in part, for the occurrence of Trojans and coorbital moons in the Saturn system, the apparent presence of a stochastic component in the trend of satellite density with radial distance, and the present population of ring particles. Saturn's excess luminosity and viscous dissipation are also discussed in relation to the satellite formation.

  18. Corrugations and eccentric spirals in Saturn's D ring: New insights into what happened at Saturn in 1983

    CERN Document Server

    Hedman, M M; Showalter, M R

    2014-01-01

    Previous investigations of Saturn's outer D ring (73,200-74,000 km from Saturn's center) identified periodic brightness variations whose radial wavenumber increased linearly over time. This pattern was attributed to a vertical corrugation, and its temporal variability implied that some event --possibly an impact with interplanetary debris-- caused the ring to become tilted out the planet's equatorial plane in 1983. This work examines these patterns in greater detail using a more extensive set of Cassini images in order to obtain additional insights into the 1983 event. These additional data reveal that the D ring is not only corrugated, but also contains a time-variable periodic modulation in its optical depth that probably represents organized eccentric motions of the D-ring's particles. This second pattern suggests that whatever event tilted the rings also disturbed the radial or azimuthal velocities of the ring particles. Furthermore, the relative amplitudes of the two patterns indicate that the vertical m...

  19. More Kronoseismology with Saturn's rings

    CERN Document Server

    Hedman, M M

    2014-01-01

    In a previous paper (Hedman and Nicholson 2013), we developed tools that allowed us to confirm that several of the waves in Saturn's rings were likely generated by resonances with fundamental sectoral normal modes inside Saturn itself. Here we use these same tools to examine eight additional waves that are probably generated by structures inside the planet. One of these waves appears to be generated by a resonance with a fundamental sectoral normal mode in the planet with azimuthal harmonic number m=10. If this attribution is correct, then the m=10 mode must have a larger amplitude than the modes with m=5-9, since the latter do not appear to generate strong waves. We also identify five waves with pattern speeds between 807 degrees/day and 834 degrees/day. Since these pattern speeds are close to the planet's rotation rate, they probably are due to persistent gravitational anomalies within the planet. These waves are all found in regions of enhanced optical depth known as plateaux, but surprisingly the surface ...

  20. The Brightening of Saturn's F Ring

    CERN Document Server

    French, Robert S; Sfair, Rafael; Argüelles, Carlos A; Pajuelo, Myriam; Becerra, Patricio; Hedman, Matthew M; Nicholson, Philip D

    2014-01-01

    Image photometry reveals that the F ring is approximately twice as bright during the Cassini tour as it was during the Voyager flybys of 1980 and 1981. It is also three times as wide and has a higher integrated optical depth. We have performed photometric measurements of more than 4,800 images of Saturn's F ring taken over a five-year period with Cassini's Narrow Angle Camera. We show that the ring is not optically thin in many observing geometries and apply a photometric model based on single-scattering in the presence of shadowing and obscuration, deriving a mean effective optical depth tau = 0.033. Stellar occultation data from Voyager PPS and Cassini VIMS validate both the optical depth and the width measurements. In contrast to this decades-scale change, the baseline properties of the F ring have not changed significantly from 2004 to 2009. However, we have investigated one major, bright feature that appeared in the ring in late 2006. This transient feature increased the ring's overall mean brightness by...

  1. IMF dependence of Saturn's auroras: modelling study of HST and Cassini data from 12–15 February 2008

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2010-08-01

    Full Text Available To gain better understanding of auroral processes in Saturn's magnetosphere, we compare ultraviolet (UV auroral images obtained by the Hubble Space Telescope (HST with the position of the open-closed field line boundary in the ionosphere calculated using a magnetic field model that employs Cassini measurements of the interplanetary magnetic field (IMF as input. Following earlier related studies of pre-orbit insertion data from January 2004 when Cassini was located ~ 1300 Saturn radii away from the planet, here we investigate the interval 12–15 February 2008, when UV images of Saturn's southern dayside aurora were obtained by the HST while the Cassini spacecraft measured the IMF in the solar wind just upstream of the dayside bow shock. This configuration thus provides an opportunity, unique to date, to determine the IMF impinging on Saturn's magnetosphere during imaging observations, without the need to take account of extended and uncertain interplanetary propagation delays. The paraboloid model of Saturn's magnetosphere is then employed to calculate the magnetospheric magnetic field structure and ionospheric open-closed field line boundary for averaged IMF vectors that correspond, with appropriate response delays, to four HST images. We show that the IMF-dependent open field region calculated from the model agrees reasonably well with the area lying poleward of the UV emissions, thus supporting the view that the poleward boundary of Saturn's auroral oval in the dayside ionosphere lies adjacent to the open-closed field line boundary.

  2. Detection of lightning in Saturn's Northern Hemisphere

    CERN Document Server

    Moghimi, Mohsen Hassanzadeh

    2012-01-01

    During Cassini flyby of Saturn at a radial distance 6.18R_s (Saturn Radius), a signal was detected from about 200 to 430 Hz that had the proper dispersion characteristics to be a whistler. The frequency-time dispersion of the whistler was found to be 81 Hz1/2s. Based on this dispersion constant, we determined, from a travel time computation, that the whistler must have originated from lightning in the northern hemisphere of Saturn. Using a simple centrifugal potential model consisting of water group ions, and hydrogen ions we also determine the fractional concentration and scale height that gave the best fit to the observed dispersion.

  3. Dusty plasma around Enceladus affects Saturn's magnetosphere

    Science.gov (United States)

    Balcerak, Ernie

    2012-02-01

    Scientists have been puzzled by periodic bursts of radiation, known as the Saturn kilometric radiation (SKR), that occur in the planet's magnetosphere. These emissions occur at a rate that is close to, but not quite the same as, the rate at which the planet rotates. New observations from the Cassini Spacecraft's flybys of Saturn's moon Enceladus in 2008 are revealing new details about the plasma environment around Enceladus and how it may affect Saturn's magnetosphere. These observations could also shed some light on the SKR rotation rate.

  4. Phosphine photochemistry in Saturn's atmosphere

    Science.gov (United States)

    Kaye, J. A.; Strobel, D. F.

    1983-01-01

    The phosphine photochemistry on Saturn is studied with a 1D photochemical model. The PH3 concentration is rapidly depleted with height (scale height 3.5 km) in the upper troposphere. Formation of P, a probable precursor of P4, (a potential red chromophore in the atmosphere), is highly improbable unless the rate constant for the recombination reaction PH + H2 + M yields PH3 + M is less than 10 to the -41st cm exp 6/molecule-squared sec. Coupling of PH3 and hydrocarbon photochemistry, specifically the C2H2 catalyzed photodissociation of CH, is important. Column production rates of the organophosphorus compounds CH3PH2 and HCP of 3 x 10 to the 8th/sq cm sec are predicted, with potentially observable column densities of greater than 1 x 10 to the 17th/sq cm.

  5. SATURN. Studying Atmospheric Pollution in Urban Areas

    DEFF Research Database (Denmark)

    Moussiopoulos, N.; Hout, K. D. van den; Mestayer, P.

    SATURN is a subproject under EUROTRAC-2. (EUROTRAC-2 is the EUREKA Project on the Transport and Chemical Transformation of Environmentally Relevant Trace Constituents in the Troposphere over Europe; Second Phase)....

  6. Chon Ices And The Formation Of Saturn

    Science.gov (United States)

    Robinson, Sarah E.; Bodenheimer, P.; Willacy, K.; Laughlin, G.; Turner, N.; Beichman, C.

    2007-12-01

    Previous core accretions simulations have found that the formation timescale of Saturn is far longer than a reasonable lifetime of the solar nebula. Saturn's formation is impaired by (1) the long orbital timescale (compared with Jupiter), leading to a slower planetesimal collision rate, and (2) the assumption that H2O is the only volatile that gets incorporated into planet cores. We use a 1+1-d evolving solar nebula model and a 214-species chemical reaction network to calculate the solid surface density available to form Saturn. New core accretion simulations based on the results of our protostellar disk model show that Saturn can form in less than 4 Myr. This work was supported by an ARCS Foundation fellowship awarded to S.R., an NSF career grant to G.L., and a NASA grant to K.W.

  7. Survey analysis of chorus intensity at Saturn

    National Research Council Canada - National Science Library

    Menietti, J. D; Averkamp, T. F; Groene, J. B; Horne, R. B; Shprits, Y. Y; Woodfield, E. E; Hospodarsky, G. B; Gurnett, D. A

    2014-01-01

    In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, P...

  8. Cassini's Cameras Catch Delightful Dynamics Surrounding Saturn

    Science.gov (United States)

    Burns, J. A.; Cassini Imaging Team

    2005-05-01

    Saturn's rings and satellites delight DDA members because of the baroque variety of their extant features and the pivotal role played by resonances. I will review some of the highlights imaged by Cassini during the first nine months of its mission. Numerous density waves, mainly in the outer A ring, were identified with unprecedented accuracy from high-resolution approach images. These include waves initiated by the classically known perturbing satellites, but also by tiny (though nearby) Atlas and Pan, the latter embedded within the A ring. Wavelet analyses have eased identification of waves, allowing estimates of the ring's areal mass density and viscosity, and the perturber's mass. The latter, when combined with satellite images, indicate that low satellite densities (ρ ˜ 0.5 g-cm-3) are the norm. Pan pries open the Encke gap, producing edge waves and imposing numerous (kinematic) gravity wakes. A narrow ringlet within that gap, coincident with Pan's orbit, shows clumps and wiggles that march along relative to Pan, presumably horseshoeing particles. All aspects of the narrow Keeler gap still await explanation. Several previously unknown structures may result from collective effects or non-linear instabilities as particles are driven together. The F ring's structure is beautifully complex but can be mostly understood as resulting from Prometheus's tugs. A few isolated narrow ringlets have been found, occasionally sharing the paths of known satellites. Some parts of the rings show time variability already. We eagerly await the switch of co-orbital Janus/Epimetheus in 2006, and again in 2010, and the plunge of Prometheus into the F ring in 2010. To date, three new satellites have been discovered: two orbit between the classical moons Mimas and Enceladus, while the third is a trailing Lagrangian of Dione. Several other objects, probably temporary clumps of material, were sighted near the F ring.

  9. Collisional Features in Saturn's F Ring

    Science.gov (United States)

    Attree, Nicholas Oliver; Murray, Carl; Cooper, Nicholas; Williams, Gareth

    2016-10-01

    Saturn's highly dynamic F ring contains a population of small (radius ~ 1 km) moonlets embedded within its core or on nearby orbits. These objects interact, both gravitationally and collisionally, with the ring producing a range of features, some of which are unique to it. Here we present a brief overview of F ring collisional processes, investigated using a combination of Cassini imaging, simulations and orbital dynamics. Collisions produce linear debris clouds, known as 'jets' and 'mini-jets', which evolve, due to differential orbital motion, over periods ranging from hours to months. Mini-jet-forming collisions occur daily in the F ring whilst larger, more dramatic, events are rarer but produce jets that persist for many months, 'wrapping around' the ring to form almost parallel strands. Measuring jet properties, such as formation rates and relative orbits, allows us to infer a local population of order hundreds of objects colliding at relative velocities of a few metres per second. N-body modelling of the collisions shows good agreement with observations when two aggregates are allowed to impact and partially fragment (as opposed to a solid moonlet encountering dust), implying massive objects both in the core and nearby. Multiple, repeated collisions by the same, or fragments of the same, object are also important in explaining some jet morphology, showing that many objects survive the collisions. The F ring represents a natural laboratory for observing low-velocity collisions between icy objects as well as the ongoing aggregation and accretion that most-likely forms them.

  10. Saturn Plasma Sources and Associated Transport Processes

    Science.gov (United States)

    Blanc, M.; Andrews, D. J.; Coates, A. J.; Hamilton, D. C.; Jackman, C. M.; Jia, X.; Kotova, A.; Morooka, M.; Smith, H. T.; Westlake, J. H.

    2015-10-01

    This article reviews the different sources of plasma for Saturn's magnetosphere, as they are known essentially from the scientific results of the Cassini-Huygens mission to Saturn and Titan. At low and medium energies, the main plasma source is the H2O cloud produced by the "geyser" activity of the small satellite Enceladus. Impact ionization of this cloud occurs to produce on the order of 100 kg/s of fresh plasma, a source which dominates all the other ones: Titan (which produces much less plasma than anticipated before the Cassini mission), the rings, the solar wind (a poorly known source due to the lack of quantitative knowledge of the degree of coupling between the solar wind and Saturn's magnetosphere), and the ionosphere. At higher energies, energetic particles are produced by energy diffusion and acceleration of lower energy plasma produced by the interchange instabilities induced by the rapid rotation of Saturn, and possibly, for the highest energy range, by contributions from the CRAND process acting inside Saturn's magnetosphere. Discussion of the transport and acceleration processes acting on these plasma sources shows the importance of rotation-induced radial transport and energization of the plasma, and also shows how much the unexpected planetary modulation of essentially all plasma parameters of Saturn's magnetosphere remains an unexplained mystery.

  11. Surprises from Saturn: Implications for Other Environments

    Science.gov (United States)

    Coates, A. J.

    2014-05-01

    The exploration of Saturn by Cassini has provided many surprises regarding: Saturn's rapidly rotating magnetosphere, interactions with its diverse moons, and interactions with the solar wind. Enceladus, orbiting at 4 Saturn radii (RS), was found to have plumes of water vapour and ice which are the dominant source for the inner magnetosphere. Charged water clusters, charged dust and photoelectrons provide key populations in the 'dusty plasma' observed. Direct pickup is seen near Enceladus and field-aligned currents create a spot in Saturn's aurora. At Titan, orbiting at 20 RS, unexpected heavy negative and positive ions are seen in the ionosphere, which provide the source for Titan's haze. Ionospheric plasma is seen in Titan's tail, enabling ion escape to be estimated at 7 tonnes per day. Saturn's ring ionosphere was seen early in the mission and a return will be made in 2017. In addition, highly accelerated electrons are seen at Saturn's high Mach number (MA˜100) quasi-parallel bow shock. Here we review some of these key new results, and discuss the implications for other solar system objects.

  12. Cassini/MIMI Measurements in Saturn's Magnetosphere and their Implications for Magnetospheric Dynamics

    Science.gov (United States)

    Mitchell, D. G.

    2016-12-01

    The Cassini spacecraft has been in orbit about Saturn since early July, 2004. In less than a year, on September 15, 2017, Cassini will plunge into Saturn's atmosphere, ending what has been a highly successful and interesting mission. As befitting a Planetary Division Flagship Mission, Cassini's science payload included instrumentation designed for a multitude of science objectives, from surfaces of moons to rings to atmospheres to Saturn's vast, fast-rotating magnetosphere. Saturn's magnetosphere exhibits considerable variability, both from inner magnetosphere to outer, and over time. Characterizing the dynamics of the magnetosphere has required the full range of energetic particles (measured by the magnetospheric imaging instrument, MIMI - https://saturn.jpl.nasa.gov/magnetospheric-imaging-instrument/), plasma (provided by the Cassini plasma spectrometer, CAPS), gas (ion and neutral mass spectrometer, INMS), magnetic fields (Cassini magnetometer, MAG), radio and plasma waves (radio and plasma wave science, RPWS), dust (Cassini Dust Analyzer, CDA), as well as ultraviolet, visible and infrared imaging (ultraviolet imaging spectrograph, UVIS; Cassini imaging subsystem ISS; visible and infrared mapping spectrometer, VIMS; Cassini composite infrared spectrometer, CIRS) and ionospheric sounding by the Cassini radio science subsystem (RSS). It has also required the full range of orbital geometries from equatorial to high inclination and all local times, as well as the full range of solar wind conditions, seasonal sun-Saturn configurations. In this talk we focus on the contributions of the MIMI instrument suite (CHEMS, LEMMS, and INCA) to our understanding of the dynamics of Saturn's magnetosphere. We will both review past work, and present recent observations from the high inclination orbits that precede the final stages of the Cassini mission, the sets of high inclination orbits that cross the equator just beyond the edge of the main ring system, and later cross between

  13. Resistive Heating in Saturn's Thermosphere

    Science.gov (United States)

    Vriesema, Jess W.; Koskinen, Tommi; Yelle, Roger V.

    2016-10-01

    The thermospheres of the jovian planets are several times hotter than solar heating alone can account for. On Saturn, resistive heating appears sufficient to explain these temperatures in auroral regions, but the particular mechanism(s) responsible for heating the lower latitudes remains unclear. Smith et al. (2005) suggested that electrodynamics of the equatorial region—particularly resistive heating caused by strong electrojet currents—might explain the observed temperatures at low latitudes. Müller-Wodarg et al. (2006) found that their circulation model could reproduce low-latitude temperatures only when they included resistive heating at the poles and applied a uniform, generic heating source globally. Smith et al. (2007) concluded that heating at the poles leads to meridional circulation that cools low latitudes and argued that in-situ heating is required to explain the temperatures at low latitudes.Resistive heating at low latitudes, arising from enhanced current generation driven by thermospheric winds, is a potentially important in-situ heating mechanism. Ion drag caused by low-latitude electrodynamics can modify global circulation and meridional transport of energy. We present an axisymmetric, steady-state formulation of wind-driven electrodynamics to investigate these possibilities throughout Saturn's thermosphere. At present, we assume a dipole magnetic field and neglect any contributions from the magnetosphere. We use ion mixing ratios from the model of Kim et al. (2014) and the observed temperature-pressure profile from Koskinen et al. (2015) to calculate the generalized conductivity tensor as described by Koskinen et al. (2014). Our model solves the coupled equations for charge continuity and Ohm's law with tensor conductivity while enforcing zero current across the boundaries. The resulting partial differential equation is solved for the current density throughout the domain and used to calculate the net resistive heating rate. We demonstrate

  14. Evidence of differential rotation inside Saturn from waves of its rings

    Science.gov (United States)

    El Moutamid, Maryame; Hedman, Matthew M.; Nicholson, Philip D.; Gierasch, Peter J.; Burns, Joseph A.

    2016-10-01

    Saturn's average interior rotation rate has been estimated based on various analyses of its shape (Anderson and Schubert, 2007; Read et al., 2009; Helled et al., 2015), but we still have no clear information on its exact value and the degree of differential rotation versus depth.However, Hedman et al., (2009), Hedman and Nicholson (2014) and El Moutamid et al., (2016) have identified several structures in the main rings of Saturn which appear to be related to the planet's rotation rate.These structures (waves and perturbed edges) appear to be generated by so-called Tesseral Resonances, which are associated with gravity anomalies that rotate with Saturn's interior, rather than being driven by a satellite. Their locations are given by the usual formula for inner or outer Lindblad resonances.We have searched for additional wave-like signatures in stellar occultation data for the main rings which are related to the rotation period of Saturn and have identified several signatures consistent with other differential rotation in Saturn's interior. Our study of the behavior of the A, B and C rings uses images and occultation data obtained by the Cassini spacecraft over a period of 10 years from 2006 to 2015.

  15. Saturn's equatorial jet structure from Cassini/ISS

    Science.gov (United States)

    García-Melendo, Enrique; Legarreta, Jon; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Hueso, Ricardo

    2010-05-01

    Detailed wind observations of the equatorial regions of the gaseous giant planets, Jupiter and Saturn, are crucial for understanding the basic problem of the global circulation and obtaining new detailed information on atmospheric phenomena. In this work we present high resolution data of Saturn's equatorial region wind profile from Cassini/ISS images. To retrieve wind measurements we applied an automatic cross correlator to image pairs taken by Cassini/ISS with the MT1, MT2, MT3 filters centred at the respective three methane absorbing bands of 619nm, 727nm, and 889nm, and with the adjacent continuum CB1, CB2, and CB3 filters. We obtained a complete high resolution coverage of Saturn's wind profile in the equatorial region. The equatorial jet displays an overall symmetric structure similar to that shown the by same region in Jupiter. This result suggests that, in accordance to some of the latest compressible atmosphere computer models, probably global winds in gaseous giants are deeply rooted in the molecular hydrogen layer. Wind profiles in the methane absorbing bands show the effect of strong vertical shear, ~40m/s per scale height, confirming previous results and an important decay in the wind intensity since the Voyager era (~100 m/s in the continuum and ~200 m/s in the methane absorbing band). We also report the discovery of a new feature, a very strong and narrow jet on the equator, about only 5 degrees wide, that despite the vertical shear maintains its intensity (~420 m/s) in both, the continuum and methane absorbing band filters. Acknowledgements: Work supported by the Spanish MICIIN AYA2009-10701 with FEDER and Grupos Gobierno Vasco IT-464-07.

  16. Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

    Science.gov (United States)

    Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

    2011-01-01

    Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind

  17. Trapped radiation belts of saturn: first look.

    Science.gov (United States)

    Fillius, W; Ip, W H; McIlwain, C E

    1980-01-25

    Pioneer 11 has made the first exploration of the magnetosphere and trapped radiation belts of Saturn. Saturn's magnetosphere is intermediate in size between Earth's and Jupiter's, with trapped particle intensities comparable to Earth's. The outer region of Saturn's magnetosphere contains lower energy radiation and is variable with time; the inner region contains higher energy particles. The pitch angle distributions show a remarkable variety of field-aligned and locally mirroring configurations. The moons and especially the rings of Saturn are effective absorbers of trapped particles; underneath the rings, the trapped radiation is completely absorbed. We confirm the discovery of a new ring, called the F ring, a new division, the Pioneer division, and a moon, called 1979 S 2. The latter has probably been seen from Earth. There may be evidence for more bodies like 1979 S 2, but at this stage the interpretation of the data is ambiguous. Using particle diffusion rates, we estimate that the cross-sectional area of the F ring is > 7 x 10(13) square centimeters and that the opacity is > 10(-5). Cosmic-ray albedo neutron decay should be looked into as a source of energetic particles in the inner magnetosphere of Saturn.

  18. Trapped radiation belts of Saturn - First look

    Science.gov (United States)

    Fillius, W.; Ip, W. H.; Mcilwain, C. E.

    1980-01-01

    Data on the magnetosphere of Saturn obtained with the trapped radiation detector package on board the Pioneer 11 spacecraft is reported. Radiation belt profiles determined by the trapped radiation detectors on Pioneer 10 and 11 indicate that Saturn's magnetosphere is intermediate in size between those of the earth and Jupiter, with particle intensities similar to those of the earth. The outer region of the Saturn magnetosphere is found to contain particles of lower energy than the outer region, being strongly influenced by the time-varying solar wind. The moons and rings of Saturn are observed to be effective absorbers of trapped particles, confirming the discoveries of the F ring, the Pioneer ring division and the moon 1979 S 2. Particle diffusion rates are used to estimate a cross-sectional area of greater than 7 x 10 to the 13th sq cm and an opacity greater than 0.00001 for the F ring. It is suggested that cosmic-ray albedo neutron decay be studied as a possible source of energetic particles in the inner magnetosphere of Saturn.

  19. Managing Cassini Safe Mode Attitude at Saturn

    Science.gov (United States)

    Burk, Thomas A.

    2010-01-01

    The Cassini spacecraft was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. It has performed detailed observations and remote sensing of Saturn, its rings, and its satellites since that time. In the event safe mode interrupts normal orbital operations, Cassini has flight software fault protection algorithms to detect, isolate, and recover to a thermally safe and commandable attitude and then wait for further instructions from the ground. But the Saturn environment is complex, and safety hazards change depending on where Cassini is in its orbital trajectory around Saturn. Selecting an appropriate safe mode attitude that insures safe operation in the Saturn environment, including keeping the star tracker field of view clear of bright bodies, while maintaining a quiescent, commandable attitude, is a significant challenge. This paper discusses the Cassini safe table management strategy and the key criteria that must be considered, especially during low altitude flybys of Titan, in deciding what spacecraft attitude should be used in the event of safe mode.

  20. An Arc in Saturn's G Ring

    Science.gov (United States)

    Burns, Joseph A.; Hedman, M.; Tiscareno, M.; Porco, C.; Jones, G.; Roussos, E.; Krupp, N.

    2006-09-01

    The G ring is a narrow, faint ring located between the orbits of Janus and Mimas. Approximately 4000 km wide, it has a strongly asymmetric brightness profile with a sharp inner edge between 167,000 km and 168,000 km from Saturn's center and a more diffuse outer part. In Cassini images, a portion of the ring contains a bright arc that abuts the G-ring's inner edge and extends over 30 degrees in longitude. By tracking this arc over the first two years of the Cassini Mission, we find its orbital period is 0.80813 day, corresponding to a semi-major axis of 167,496 km. Since this location places the arc within 6 km of the Mimas 7:6 Co-rotation Eccentricity Resonance and within 12 km of the Mimas 7:6 Inner Lindblad Resonance, the arc is likely confined in longitude by Mimas just as Neptune's ring arcs are held in place by Galatea. The arc's longitude relative to Mimas is consistent with this model. Cassini now has the opportunity to study the dynamics of this sort of system in detail over a period of years. The arc, which may be the debris of a fragmented moon, may also supply the particles found in the rest of the G ring; micron-sized grains drift outwards by non-gravitational processes in this region. The G-ring is responsible for a broad, relatively modest decrease in the fluxes of magnetospheric charged particles. When Cassini passed over the G ring in the vicinity of the arc, on September 5, 2005, the MIMI instrument detected a particularly sharp and deep charged particle absorption signature. Such a pronounced charged particle absorption was not seen in the other G-ring passages that occurred longitudinally far from the arc. The nature of this absorption provides constraints on the population of large particles in this arc.

  1. A Traveling Feature in Saturn's Rings

    CERN Document Server

    Rehnberg, Morgan E; Brown, Zarah L; Albers, Nicole; Sremčević, Miodrag; Stewart, Glen R

    2016-01-01

    The co-orbital satellites of Saturn, Janus and Epimetheus, swap radial positions every 4.0 years. Since \\textit{Cassini} has been in orbit about Saturn, this has occurred on 21 January in 2006, 2010, and 2014. We describe the effects of this radial migration in the Lindblad resonance locations of Janus within the rings. When the swap occurs such that Janus moves towards Saturn and Epimetheus away, nonlinear interference between now-relocated density waves launches a solitary wave that travels through the rings with a velocity approximately twice that of the local spiral density wave group velocity in the A ring and commensurate with the spiral density wave group velocity in the B ring.

  2. Saturn facility oil transfer automation system

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, Nathan R.; Thomas, Rayburn Dean; Lewis, Barbara Ann; Malagon, Hector Ricardo.

    2014-02-01

    The Saturn accelerator, owned by Sandia National Laboratories, has been in operation since the early 1980s and still has many of the original systems. A critical legacy system is the oil transfer system which transfers 250,000 gallons of transformer oil from outside storage tanks to the Saturn facility. The oil transfer system was iden- ti ed for upgrade to current technology standards. Using the existing valves, pumps, and relay controls, the system was automated using the National Instruments cRIO FGPA platform. Engineered safety practices, including a failure mode e ects analysis, were used to develop error handling requirements. The uniqueness of the Saturn Oil Automated Transfer System (SOATS) is in the graphical user interface. The SOATS uses an HTML interface to communicate to the cRIO, creating a platform independent control system. The SOATS was commissioned in April 2013.

  3. Hydrocarbons on the Icy Satellites of Saturn

    Science.gov (United States)

    Cruikshank, Dale P.

    2010-01-01

    The Visible-Infrared Mapping Spectrometer on the Cassini Spacecraft has obtained spectral reflectance maps of the satellites of Saturn in the wavelength region 0.4-5.1 micrometers since its insertion into Saturn orbit in late 2004. We have detected the spectral signature of the C-H stretching molecular mode of aromatic and aliphatic hydrocarbons in the low albedo material covering parts of several of Saturn's satellites, notably Iapetus and Phoebe (Cruikshank et al. 2008). The distribution of this material is complex, and in the case of Iapetus we are seeking to determine if it is related to the native grey-colored materials left as lag deposits upon evaporation of the ices, or represents in-fall from an external source, notably the newly discovered large dust ring originating at Phoebe. This report covers our latest exploration of the nature and source of this organic material.

  4. Scientific rationale of Saturn's in situ exploration

    CERN Document Server

    Mousis, O; Lebreton, J -P; Wurz, P; Cavalié, T; Coustenis, A; Courtin, R; Gautier, D; Helled, R; Irwin, P G J; Morse, A D; Nettelmann, N; Marty, B; Rousselot, P; Venot, O; Atkinson, D H; Waite, J H; Reh, K R; Simon-Miller, A; Atreya, S; André, N; Blanc, M; Daglis, I A; Fischer, G; Geppert, W D; Guillot, T; Hedman, M M; Hueso, R; Lellouch, E; Lunine, J I; Murray, C D; O'Donoghue, J; Rengel, M; Sanchez-Lavega, A; Schmider, F -X; Spiga, A; Spilker, T; Petit, J -M; Tiscareno, M S; Ali-Dib, M; Altwegg, K; Bouquet, A; Briois, C; Fouchet, T; Guerlet, S; Kostiuk, T; Lebleu, D; Moreno, R; Orton, G S; Poncy, J

    2014-01-01

    Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn's atmosphere addresses two broad themes that are discussed throughout this paper: first, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn's bulk element...

  5. Far infrared spectrophotometry of Jupiter and Saturn

    Science.gov (United States)

    Erickson, E. F.; Goorvitch, D.; Simpson, J. P.; Strecker, D. W.

    1978-01-01

    Infrared spectral measurements of Mars, Jupiter, and Saturn were obtained from 100 to 470 kaysers and, by taking Mars as a calibration source, brightness temperatures of Jupiter and Saturn were determined with approximately 5 kayser resolution. Internal luminosities were determined from the data and are reported to be approximately 8 times 10 to the minus tenth power of the sun's luminosity for Jupiter and approximately 3.6 times 10 to the minus tenth power of the sun's luminosity for Saturn. Comparison of data with spectra predicted by models suggests the need for an opacity source in addition to gaseous hydrogen and ammonia to help explain Jupiter's observed spectrum in the vicinity of 250 kaysers.

  6. Radial plasma transport in Saturn's magnetosphere (Invited)

    Science.gov (United States)

    Hill, T. W.

    2010-12-01

    Radial plasma transport in the magnetosphere of Saturn, like that of Jupiter, is driven by the centrifugal force of (partial) corotation acting on internally generated plasma. A significant difference is that the internal plasma source is evidently broadly distributed throughout the inner magnetosphere of Saturn (4 CAPS and MAG), and reproduced in numerical simulations (RCM) that contain a distributed plasma source, although it has not, to my knowledge, been explained by an analytical theory containing an active plasma source. Both planets exhibit strong magnetospheric modulations near the planetary spin period, probably indicating a persistent longitudinal asymmetry of the radial plasma transport process. At Jupiter such an asymmetry is readily understood as a consequence of the dramatic asymmetry of the intrinsic planetary magnetic field. This is not so at Saturn, where any such field asymmetry is known to be very modest at best. In neither case has the precise nature of the asymmetry been identified either observationally or theoretically.

  7. Suprathermal electrons at Saturn's bow shock

    CERN Document Server

    Masters, A; Sergis, N; Stawarz, L; Fujimoto, M; Coates, A J; Dougherty, M K

    2016-01-01

    The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini. The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, 18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically onl...

  8. Nanograin densities outside Saturn's A-ring

    CERN Document Server

    Johnson, Robert E; Elrod, Meredith K; Persoon, Ann M

    2016-01-01

    The observed disparity between the radial dependence of the ion and electron densities measured by the Cassini plasma and radio science instruments are used to show that the region between the outer edge of Saturn's main rings and its tenuous G-ring is permeated with small charged grains (nanograins). These grains emanate from the edge of the A-ring and from the tenuous F-ring and G-ring. This is a region of Saturn's magnetosphere that is relatively unexplored, but will be a focus of Cassini's F-ring orbits prior to the end of mission in September 2017. Confirmation of the grain densities predicted here will enhance our ability to describe the formation and destruction of material in this important region of Saturn's magnetosphere.

  9. The Orbits of Saturn's Small Satellites

    Science.gov (United States)

    Spitale, J. N.; Jacobson, R. A.; Porco, C. C.; Owen, W. M.; Charnoz, S.

    2005-05-01

    We report on the orbits of the small, inner Saturnian satellites, either recovered or newly-discovered in recent Cassini imaging observations (excluding Helene, Telesto and Calypso, which will be discussed by another group). Using combined Cassini and Voyager observations, the mean motions of Pan and Atlas have been refined by several orders of magnitude. The Atlas orbit is based on a numerical integration perturbed by all of the massive Saturnian satellites including Prometheus, Pandora, Janus, and Epimetheus. We find that the dominant perturber is Prometheus. Cassini, Voyager, HST, and Earth-based data have been used to refine the orbits of Janus, Epimetheus, Prometheus and Pandora. The orbits of the co-orbitals, Janus and Epimetheus, remain stable; their orbital swap does not occur until Februrary, 2006. The orbits of Prometheus and Pandora remain close to recent values (Jacobson and French 2004, Icarus, 172, 382). Six new objects have been discovered to date -- three (S/2004 S3, S4, S6) in close proximity to the F ring, two (S/2004 S1(Methone), S/2004 S2(Pallene)) between the orbits of Mimas and Enceladus, and one (S/2004 S5(Polydeuces)) co-orbital with Dione, trailing by ˜60 deg (Porco et al., Science 307, 25 Feb 2005). One of the F-ring objects -- S/2004 S3 -- was seen over a 118-day interval, but none of those objects, including S/2004 S3, were subsequently recovered in an F-ring movie acquired on 15 November 2004 (29 days after the last sighting of S/2004 S3) with an image scale of 4 km/pixel, in which all were expected to appear. Consequently, we are confident only that Methone, Pallene and Polydeuces are solid satellites; S/2004 S3, S4 and S6 may be transient clumps. Our orbital fits, both precessing ellipse models and orbital integrations, suggest that Pallene is the same object as S/1981 S14, imaged by Voyager 2 on 23 August 1981, contrary to our initial reports (IAU circular 8389). The orbital inclination and eccentricity of Methone are considerably

  10. Exploring Saturn - The Saturn PRobe Interior and aTmosphere Explorer (SPRITE) Mission

    Science.gov (United States)

    Atkinson, David H.; Simon, Amy A.; Banfield, Don; Atreya, Sushil K.; Blacksberg, Jordana; Brinckerhoff, William; Colaprete, Anthony; Coustenis, Athena; Fletcher, Leigh; Guillot, Tristan; Hofstadter, Mark; Lunine, Jonathan I.; Mahaffy, Paul; Marley, Mark S.; Mousis, Olivier; Spilker, Thomas R.; Trainer, Melissa G.; Webster, Chris

    2016-10-01

    A Saturn Probe mission was identified by the Vision and Voyages Planetary Decadal Survey as a mission target of high priority for the New Frontiers program. To better constrain models of Solar System formation, as well as to provide an improved context for exoplanet systems, fundamental measurements of noble gas abundances and isotope ratios of hydrogen, carbon, oxygen, and nitrogen, as well as the interior structure of Saturn are needed. The SPRITE mission will fulfill the scientific goals defined in the Decadal Survey, as well as provide ground truth for remote sensing and conduct new investigations to improve understanding of Saturn's interior structure and composition, and by proxy, those of extrasolar giant planets.Many key questions regarding the structure and composition of Saturn's atmosphere remain elusive, including the abundance of noble gases and key isotopes, the abundance of helium, needed to understand the formation history and evolution of Saturn, and the water abundance in the deep atmosphere, a key diagnostic of Saturn's formation since it is thought that the heavy elements were delivered to Saturn by water-bearing planetesimals. Additionally, the structure of Saturn's deep interior including the presence of a core and any layered structure will test instability models in the protosolar nebula.SPRITE will make measurements that address these key questions through delivery of an atmospheric entry probe, as well as remote sensing from the carrier spacecraft. SPRITE will provide direct measurement of composition and atmospheric structure (including dynamics) along the probe descent path, providing science that is not accessible to remote sensing measurements, as well as providing ground truth for tropospheric measurements from carrier remote sensing. SPRITE will measure the deep atmospheric composition, as well as temperature, pressure and wind speeds.

  11. The behavior of spokes in Saturn's B ring

    Science.gov (United States)

    Mitchell, C. J.; Porco, C. C.; Dones, H. L.; Spitale, J. N.

    2013-07-01

    We present the first results from Cassini ISS observations aimed at determining both the short-term and long-term behavior of the spokes in Saturn's B ring. We have observed multiple spokes which appear between images where there was not a spoke before. The radial termini of these new spokes expand radially at ˜0.5 km/s in both the inward and outward directions and both towards and away from corotation. Defining a spoke's activity as the area-integrated optical depth over the region of the ring it covers, we find that the majority of spokes which are found in multiple images are either increasing or decreasing in activity. In addition, in analyzing the shapes and motions of spokes, we find the azimuthal profiles to be well-fitted by Gaussians for the majority of spokes. We have found that several of the imaged spokes were undergoing an "active" phase during which the spoke's optical depth increases and the spoke grows both azimuthally and radially. We interpret these motions to be either due to the Lorentz force acting on dust grains charged by a very high temperature plasma or the group velocity of an advancing spoke-forming front. The spokes' light scattering behavior suggests that the particles comprising them are not spherical but instead are irregularly shaped. We search for periodicities in the longer-term temporal variability of spoke activity, and for correlations between spoke activity and other processes ongoing in Saturn's magnetosphere and atmosphere. Using the latest results on the periods and locations of the sources of Saturn's Kilometric Radiation (SKR) obtained by the Cassini Radio and Plasma Wave experiment (RPWS) (Gurnett, D.A., Groene, J.B., Averkamp, J.B., Kurth, W.S., Ye, S.-Y., Fischer, G. [2011]. Planet. Solar Heliosph. Radio Emis. PRE VII, 51-64), we find that spoke activity observed on both sides of Saturn's rings occurs with a period equal to, within all uncertainties, the period of the SKR emissions arising from the northern SKR source

  12. Conjugate observations of Saturn's northern and southern H3+ aurorae

    CERN Document Server

    O'Donoghue, James; Melin, Henrik; Cowley, Stan W H; Badman, Sarah V; Moore, Luke; Miller, Steve; Tao, Chihiro; Baines, Kevin H; Blake, James S D

    2013-01-01

    We present an analysis of recent high spatial and spectral resolution ground-based infrared observations of H3+ spectra obtained with the 10-metre Keck II telescope in April 2011. We observed H3+ emission from Saturn's northern and southern auroral regions, simultaneously, over the course of more than two hours, obtaining spectral images along the central meridian as Saturn rotates. Previous ground-based work has derived only an average temperature of an individual polar region, summing an entire night of observations. Here we analyse 20 H3+ spectra, 10 for each hemisphere, providing H3+ temperature, column density and total emission in both the northern and southern polar regions simultaneously, improving on past results in temporal cadence and simultaneity. We find that: 1) the average thermospheric temperatures are 527+/-18 K in northern Spring and 583+/-13 K in southern Autumn, respectively; 2) this asymmetry in temperature is likely to be the result of an inversely proportional relationship between the t...

  13. Non-circular features in Saturn's D ring: D68

    CERN Document Server

    Hedman, M M; Burns, J A; Showalter, M R

    2014-01-01

    D68 is a narrow ringlet located only 67,627 km (1.12 planetary radii) from Saturn's spin axis. Images of this ringlet obtained by the Cassini spacecraft reveal that this ringlet exhibits persistent longitudinal brightness variations and a substantial eccentricity (ae=25+/-1 km). By comparing observations made at different times, we confirm that the brightness variations revolve around the planet at approximately the local orbital rate (1751.6 degrees/day), and that the ringlet's pericenter precesses at 38.243+/-0.008 degrees/day, consistent with the expected apsidal precession rate at this location due to Saturn's higher-order gravitational harmonics. Surprisingly, we also find that the ringlet's semi-major axis appears to be decreasing with time at a rate of 2.4+/-0.4 km/year between 2005 and 2013. A closer look at these measurements, along with a consideration of earlier Voyager observations of this same ringlet, suggests that the mean radius of D68 moves back and forth, perhaps with a period of around 15 E...

  14. Illustration of Saturn V Launch Vehicle

    Science.gov (United States)

    1967-01-01

    This is a cutaway illustration of the Saturn V launch vehicle with callouts of the major components. The Saturn V is the largest and most powerful launch vehicle developed in the United States. It was a three stage rocket, 363 feet in height, used for sending American astronauts to the moon and for placing the Skylab in Earth orbit. The Saturn V was designed to perform Earth orbital missions through the use of the first two stages, while all three stages were used for lunar expeditions. The S-IC stage (first stage) was powered by five F- engines, which burned kerosene and liquid oxygen to produce more than 7,500,000 pounds of thrust. The S-II (second) stage was powered by five J-2 engines, that burned liquid hydrogen and liquid oxygen and produced 1,150,000 pounds thrust. The S-IVB (third) stage used one J-2 engine, producing 230,000 pounds of thrust, with a re-start capability. The Marshall Space Flight Center and its contractors designed, developed, and assembled the Saturn V launch vehicle stages.

  15. Electrostatic discharges in Saturn's B-ring

    Science.gov (United States)

    Warwick, J. W.; Romig, J. H.; Evans, D. R.

    1983-01-01

    The Voyager observations of electrical discharges in Saturn's rings strongly support earlier speculations on the role played by electrostatics, magnetic fields, and lightning phenomena in the primitive solar system. They also suggest conditions then by direct analogy rather than by extrapolating backwards through time from conditions now. The observed discharges show a pronounced 10h periodicity, which suggests a source in Keplerian orbit at 1.80 + or - 0.01 Saturn radii. In that region, the B ring is thicker than optical depth 1.8 for about 5,000 km. At 1.805 + or - 0.001 Saturn radii, however, the ring is virtually transparent for a gap of width 200 m. It is concluded that a small satellite orbits Saturn at that radius and clears the gap. The gap edges must prevent diffusive filling of the gap by fine material which is especially abundant at this position in the rings and would otherwise destroy the gap in minutes. The discharges represent the satellite's interaction with the outer edge of the gap. Spoke formation may involve the interaction of ring material in the vicinity of the gap.

  16. Saturn's electrostatic discharges - Properties and theoretical considerations

    Science.gov (United States)

    Evans, D. R.; Romig, J. H.; Warwick, J. W.

    1983-01-01

    The properties of Saturn's electrostatic discharges (SED) as observed by the Voyager Planetary Radio Astronomy experiment during the two Voyager encounters with Saturn are summarized. Several models for the formation of SED are discussed in light of these observations. The most likely source regions appear to be either the equatorial zone of the planet or the dense part of the B ring near 1.80 Saturn radii. The strengths and weaknesses of each of these possibilities are examined. Neither possibility accounts fully for the observed SED properties in a simple way. A search for an anomaly near 1.80 Saturn radii in the data of other experiments aboard Voyager has been carried out, and at least one and possibly more such experiments do indeed obtain anomalous data at this point in the ring system. There thus appears to be unexplained phenomena at this point, independent of the PRA data, and it is a short step to postulate that a single object may be the cause of all such phenomena.

  17. Compositional mapping of Saturn's satellite Dione with Cassini VIMS and implications of dark material in the Saturn system

    Science.gov (United States)

    Clark, R.N.; Curchin, J.M.; Jaumann, R.; Cruikshank, D.P.; Brown, R.H.; Hoefen, T.M.; Stephan, K.; Moore, Johnnie N.; Buratti, B.J.; Baines, K.H.; Nicholson, P.D.; Nelson, R.M.

    2008-01-01

    Cassini VIMS has obtained spatially resolved imaging spectroscopy data on numerous satellites of Saturn. A very close fly-by of Dione provided key information for solving the riddle of the origin of the dark material in the Saturn system. The Dione VIMS data show a pattern of bombardment of fine, sub-0.5-??m diameter particles impacting the satellite from the trailing side direction. Multiple lines of evidence point to an external origin for the dark material on Dione, including the global spatial pattern of dark material, local patterns including crater and cliff walls shielding implantation on slopes facing away from the trailing side, exposing clean ice, and slopes facing the trailing direction which show higher abundances of dark material. Multiple spectral features of the dark material match those seen on Phoebe, Iapetus, Hyperion, Epimetheus and the F-ring, implying the material has a common composition throughout the Saturn system. However, the exact composition of the dark material remains a mystery, except that bound water and, tentatively, ammonia are detected, and there is evidence both for and against cyanide compounds. Exact identification of composition requires additional laboratory work. A blue scattering peak with a strong UV-visible absorption is observed in spectra of all satellites which contain dark material, and the cause is Rayleigh scattering, again pointing to a common origin. The Rayleigh scattering effect is confirmed with laboratory experiments using ice and 0.2-??m diameter carbon grains when the carbon abundance is less than about 2% by weight. Rayleigh scattering in solids is also confirmed in naturally occurring terrestrial rocks, and in previously published reflectance studies. The spatial pattern, Rayleigh scattering effect, and spectral properties argue that the dark material is only a thin coating on Dione's surface, and by extension is only a thin coating on Phoebe, Hyperion, and Iapetus, although the dark material abundance

  18. New `Moons' of Saturn May Be Transient Objects

    Science.gov (United States)

    1996-01-01

    ring plane crossings (RPX) . At the corresponding times, the Sun illuminates the thin Saturnian rings exactly from the side. Due to its own orbital motion around the Sun, the Earth will cross the ring plane either once or three times, just before and/or after a solar RPX event. In 1995, this happened on May 22 and August 10, and there will be a third Earth RPX event on February 11, 1996. RPX Events Offer Improved Possibilities to Discover Faint Moons The apparent brightness of Saturn's rings decreases dramatically around the time of a solar RPX event. It is then much easier to detect faint moons which would otherwise be lost in the strong glare of Saturn's ring system. Also, the edge-on view improves the chances of detecting faint and dilute rings [3]. Moreover, numerous `mutual events' (eclipses and occultations) occur between the moons during this period; exact timing of these events allows highly improved determination of the motions and orbits around Saturn of these objects. The most recent Earth RPX event took place on August 10, 1995. At this time, Saturn was situated nearly opposite the Sun (in `opposition'), as seen from the Earth, and conditions were very favourable for astronomical observations from both hemispheres. However, because of the longer nights during the southern winter, observing possibilities were particularly good in the south and thus at the ESO La Silla Observatory. The ADONIS Observations Here, a team of astronomers (Jean-Luc Beuzit, Bruno Sicardy and Francois Poulet of the Paris Observatory; Pablo Prado from ESO) followed this rare event during 6 half-nights around August 10, 1995, with the advanced ADONIS adaptive optics camera at the ESO 3.6-m telescope. This instrument neutralizes the image-smearing effects of the atmospheric turbulence and records very sharp images on an infrared-sensitive 256 x 256 pixel detector with a scale of 0.05 arcsec/pixel. Most of the Saturn images were taken through the `short K' filter with a central

  19. Solar wind dynamic pressure and electric field as the main factors controlling Saturn's aurorae.

    Science.gov (United States)

    Crary, F J; Clarke, J T; Dougherty, M K; Hanlon, P G; Hansen, K C; Steinberg, J T; Barraclough, B L; Coates, A J; Gérard, J-C; Grodent, D; Kurth, W S; Mitchell, D G; Rymer, A M; Young, D T

    2005-02-17

    The interaction of the solar wind with Earth's magnetosphere gives rise to the bright polar aurorae and to geomagnetic storms, but the relation between the solar wind and the dynamics of the outer planets' magnetospheres is poorly understood. Jupiter's magnetospheric dynamics and aurorae are dominated by processes internal to the jovian system, whereas Saturn's magnetosphere has generally been considered to have both internal and solar-wind-driven processes. This hypothesis, however, is tentative because of limited simultaneous solar wind and magnetospheric measurements. Here we report solar wind measurements, immediately upstream of Saturn, over a one-month period. When combined with simultaneous ultraviolet imaging we find that, unlike Jupiter, Saturn's aurorae respond strongly to solar wind conditions. But in contrast to Earth, the main controlling factor appears to be solar wind dynamic pressure and electric field, with the orientation of the interplanetary magnetic field playing a much more limited role. Saturn's magnetosphere is, therefore, strongly driven by the solar wind, but the solar wind conditions that drive it differ from those that drive the Earth's magnetosphere.

  20. Development of a Net Flux Radiometer for the Hera Saturn Probe Mission

    Science.gov (United States)

    Aslam, Shahid; Amato, Michael; Atkinson, David; Mousis, Olivier; Nixon, Conor; Simon, Amy A.; Hera Probe Mission Team

    2016-10-01

    In situ exploration of all the giant planets in the outer solar system is an imperative and a Saturn probe is the next compelling step beyond Galileo's in situ exploration of Jupiter, the remote investigation of its interior, gravity, and magnetic fields by the Juno mission, and the Cassini spacecraft's similar orbital reconnaissance of Saturn. One such proposed future mission is "HERA: an international atmospheric probe to unveil the depths of Saturn" a nominal configuration is a combined ESA/Class-M probe mission accompanied by a launch vehicle and carrier relay spacecraft provided by NASA. One of the instruments being considered for inclusion on the probe is a Net Flux Radiometer (NFR) to unravel the vertical structure and properties of Saturn's cloud and haze layers. A NFR concept is presented that can be included in an atmospheric structure instrument suite for the Hera mission. The current design has two spectral channels i.e., a solar channel (0.4-to-5 µm) and a thermal channel (4-to-50 µm). The NFR is capable of viewing five distinct viewing angles during the descent. Non-imaging Winston cones with window and filter combinations define the spectral channels with a 5° Field-Of View (FOV). Uncooled thermopile detectors are used in each spectral channel and are read out using a custom designed radiation-hard Application Specific Integrated Circuit (ASIC).

  1. Weak Waves and Wakes in Saturn's Rings: Observations by Cassini ISS

    Science.gov (United States)

    Burns, J. A.; Tiscareno, M. S.; Porco, C. C.; Dones, H.; Murray, C. D.; Cassini Imaging

    2004-11-01

    At Saturn Orbit Insertion (SOI), the Cassini Imaging Science Subsystem (ISS) imaged the rings of Saturn with unprecedented resolution and signal/noise. Many features are present with remarkable clarity, including density waves excited by first-order Lindblad resonances with the tiny satellite Atlas, as well as density waves excited by second-order Lindblad resonances with Janus, Prometheus, and Pandora. Additionally, we find much structure due to Pan, the satellite embedded in the Encke Gap. As one moves away from the gap, the Pan disturbances undergo a transition, from features best described as gravitional wakes to features best described as density waves. We will present examples of these phenomena and discuss their implications.

  2. Saturn's ``Gossamer'' Ring: The F Ring's Inner Sheet

    Science.gov (United States)

    Showalter, M. R.; Burns, J. A.; Hamilton, D. P.

    1998-09-01

    Recent Galileo and Earth-based images have revealed for the first time that Jupiter's ``gossamer'' ring is actually composed of two rings, one bounded at the outer edge by Amalthea and the other bounded by Thebe. Dynamical models suggest that these rings are composed of dust grains ejected off the surfaces of the two moons, which then evolve inward under Poynting-Robertson drag. A very faint sheet of material filling the region between Saturn's A and F Rings reported by Burns et al. (BAAS 15, 1013--1014, 1983) may be a dynamically analogous system, in which dust escapes from the F Ring and evolves inward to the A Ring. Unlike Jupiter's gossamer rings, however, the inner sheet of Saturn's F Ring has been well observed from a large range of phase angles and visual wavelengths by Voyager. Voyager images reveal that this faint ring shows a tenfold increase in brightness between phase angles of 125(deg) and 165(deg) , indicating that it is composed of fine dust microns in size. Preliminary estimates of the normal optical depth fall in the range 1--2*E(-4) , depending on the dust size distribution assumed. Initial spectrophotometry reveals that the ring is neutral in color. The ring is uniform in brightness over the entire region between the two rings, with no evidence for internal structure associated with Prometheus and Atlas, suggesting that neither of these embedded moons acts as either a source or a sink. We will refine the aforementioned measurements and develop photometric models to better constrain the properties of the dust in this ring. This will enable us to relate the dust population to that in the F Ring proper, and to better explore the dynamical processes at work.

  3. Energetic electron spectra in Saturn's plasma sheet

    Science.gov (United States)

    Carbary, J. F.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Krupp, N.

    2011-07-01

    The differential spectra of energetic electrons (27-400 keV) in Saturn's plasma sheet can be characterized by power law or kappa distributions. Using all available fluxes from 2005 to 2010, fits to these distributions reveal a striking and consistent pattern of radial dependence in Saturn's plasma sheet (∣z∣ constant throughout the Cassini mission. Inward of about 10 RS, the presence of the electron radiation belts and losses of lower-energy electrons to the gas and grain environment give rise to the very hard spectra in the inner magnetosphere, while the hard spectra in the outer magnetosphere may derive from auroral acceleration at high latitudes. The gradual softening of the spectra from 20 to 10 RS is explained by inward radial diffusion.

  4. Time variability in Saturn's magnetic rotation

    Science.gov (United States)

    Southwood, D. J.; Dougherty, M. K.; Kivelson, M. G.

    2006-12-01

    Magnetometer data from the Cassini Saturn orbiter spacecraft are analysed with the aim of distinguishing a Saturn rotation rate and possible time variation in it from the repeatable `cam shaft' signature seen on each periapsis. The cam signal (outward displacement in one longitude hemisphere and inward in the other) that is used appears to be generated by a rotating field aligned current system which is also likely to be the seat of the radio signal. Using the hypothesis of phase conservation between periapsis passes, it is shown that the magnetic rotation period has a time scale for evolution of years like that reported for the SKR planetary radio signal. Deviations from expectations are described as are implications for determination of a longitude system and defining deep rotation rates.

  5. Cassini: Mission to Saturn and Titan

    Science.gov (United States)

    Kerridge, Stuart J.; Flury, Walter; Horn, Linda J.; Lebreton, Jean-Pierre; Stetson, Douglas S.; Stoller, Richard L.; Tan, Grace H.

    1992-01-01

    The Cassini Mission to Saturn and Titan represents an important step into the exploration of the outerplanets. It will expand on the flyby encounters of Pioneer and Voyager and parallel the detailed exploration of the Jupiter system to be accomplished by the Galileo Mission. By continuing the study of the two giant planets and enabling detailed comparisons of their structure and behavior, Cassini will provide a tremendous insight into the formation and evolution of the solar system. In addition, by virtue of its focus on the Saturnian satellite Titan, Cassini will return detailed data on an environment whose atmospheric chemistry may resemble that of the primitive Earth. The scientific objectives can be divided into five categories: Titan, Saturn, rings, icy satellites, and magnetospheres. The key area of interest to exobiologists is Titan; the other four scientific categories will be discussed briefly to provide a comprehensive overview of the Cassini Mission.

  6. Evidence for reconnection at Saturn's magnetopause

    Science.gov (United States)

    McAndrews, H. J.; Owen, C. J.; Thomsen, M. F.; Lavraud, B.; Coates, A. J.; Dougherty, M. K.; Young, D. T.

    2008-04-01

    Observations of Saturn's magnetopause by the Cassini Plasma Spectrometer (CAPS) and magnetometer have revealed clear instances of magnetic reconnection signatures, two of which are described here. Both encounters occurred at the equator in the prenoon sector as Cassini was exiting the magnetosphere. Evidence of heating in the electrons and ions is highly suggestive of energization comparable to that associated with the reconnection process at Earth. In one case, the fields are strongly antiparallel and the magnetic data indicate the presence of a locally open magnetic field. In the other example, magnetic data indicate a locally closed magnetic field compatible with the field lines being locally parallel, but the particle signatures lead to the conclusion of a distant reconnection site poleward of the cusps being active. The reconnection voltage for the first case is calculated to be 48 kV, which is of the same order as previous estimates at Saturn. This is lower than the corotational voltage but is not insignificant.

  7. The Hera Saturn entry probe mission

    Science.gov (United States)

    Mousis, O.; Atkinson, D. H.; Spilker, T.; Venkatapathy, E.; Poncy, J.; Frampton, R.; Coustenis, A.; Reh, K.; Lebreton, J.-P.; Fletcher, L. N.; Hueso, R.; Amato, M. J.; Colaprete, A.; Ferri, F.; Stam, D.; Wurz, P.; Atreya, S.; Aslam, S.; Banfield, D. J.; Calcutt, S.; Fischer, G.; Holland, A.; Keller, C.; Kessler, E.; Leese, M.; Levacher, P.; Morse, A.; Muñoz, O.; Renard, J.-B.; Sheridan, S.; Schmider, F.-X.; Snik, F.; Waite, J. H.; Bird, M.; Cavalié, T.; Deleuil, M.; Fortney, J.; Gautier, D.; Guillot, T.; Lunine, J. I.; Marty, B.; Nixon, C.; Orton, G. S.; Sánchez-Lavega, A.

    2016-10-01

    The Hera Saturn entry probe mission is proposed as an M-class mission led by ESA with a contribution from NASA. It consists of one atmospheric probe to be sent into the atmosphere of Saturn, and a Carrier-Relay spacecraft. In this concept, the Hera probe is composed of ESA and NASA elements, and the Carrier-Relay Spacecraft is delivered by ESA. The probe is powered by batteries, and the Carrier-Relay Spacecraft is powered by solar panels and batteries. We anticipate two major subsystems to be supplied by the United States, either by direct procurement by ESA or by contribution from NASA: the solar electric power system (including solar arrays and the power management and distribution system), and the probe entry system (including the thermal protection shield and aeroshell). Hera is designed to perform in situ measurements of the chemical and isotopic compositions as well as the dynamics of Saturn's atmosphere using a single probe, with the goal of improving our understanding of the origin, formation, and evolution of Saturn, the giant planets and their satellite systems, with extrapolation to extrasolar planets. Hera's aim is to probe well into the cloud-forming region of the troposphere, below the region accessible to remote sensing, to the locations where certain cosmogenically abundant species are expected to be well mixed. By leading to an improved understanding of the processes by which giant planets formed, including the composition and properties of the local solar nebula at the time and location of giant planet formation, Hera will extend the legacy of the Galileo and Cassini missions by further addressing the creation, formation, and chemical, dynamical, and thermal evolution of the giant planets, the entire solar system including Earth and the other terrestrial planets, and formation of other planetary systems.

  8. Energy-banded ions in Saturn's magnetosphere

    Science.gov (United States)

    Thomsen, M. F.; Badman, S. V.; Jackman, C. M.; Jia, X.; Kivelson, M. G.; Kurth, W. S.

    2017-05-01

    Using data from the Cassini Plasma Spectrometer ion mass spectrometer, we report the first observation of energy-banded ions at Saturn. Observed near midnight at relatively high magnetic latitudes, the banded ions are dominantly H+, and they occupy the range of energies typically associated with the thermal pickup distribution in the inner magnetosphere (L distance (or time or decreasing latitude). Their pitch angle distribution suggests a source at low (or slightly southern) latitudes. The band energies, including their pitch angle dependence, are consistent with a bounce-resonant interaction between thermal H+ ions and the standing wave structure of a field line resonance. There is additional evidence in the pitch angle dependence of the band energies that the particles in each band may have a common time of flight from their most recent interaction with the wave, which may have been at slightly southern latitudes. Thus, while the particles are basically bounce resonant, their energization may be dominated by their most recent encounter with the standing wave.Plain Language SummaryDuring an outbound passage by the Cassini spacecraft through Saturn's inner magnetosphere, ion energy distributions were observed that featured discrete flux peaks at regularly spaced energies. The peaks persisted over several hours and several Saturn radii of distance away from the planet. We show that these "bands" of ions are plausibly the result of an interaction between the Saturnian plasma and standing waves that form along the magnetospheric magnetic field lines. These observations are the first reported evidence that such standing waves may be present in the inner magnetosphere, where they could contribute to the radial transport of Saturn's radiation belt particles.

  9. 全新土星Saturn Sky

    Institute of Scientific and Technical Information of China (English)

    张琼

    2002-01-01

    @@ 大多数概念车都为测试公众的反应而设计,而全新敞蓬概念车土星天家(Saturn SKY)却是为了迎合青年人的鼓掌好而诞生,满足他们自己和朋友寻找一片乐土的迫切愿望.

  10. Evidence for Corotating Convection in Saturn's Magnetosphere

    Science.gov (United States)

    Kivelson, M. G.; Southwood, D. J.; Dougherty, M. K.

    2006-05-01

    Saturn's magnetic field exhibits a high degree of azimuthal symmetry, yet the field and plasma signatures of the magnetosphere are modulated at a period close to that of planetary rotation. How, then, is a clear periodicity imposed on the magnetic field and plasma of the planetary magnetosphere? In this talk, Cassini magnetometer data are used to develop a scenario for the dynamics of the Saturn magnetosphere. The proposal is that mass transport, accomplished in the inner magnetosphere by interchange motion, feeds into the outer magnetosphere where ballooning driven by centrifugal stress leads to outward transport, field reconnection and plasma loss in a favored local time sector; flux is transported inward in other regions. The model is closely related to the concept of corotating convection proposed by Dessler, Hill, and co-workers for Jupiter. The proposed mechanism can be consistent with aspects of the empirical camshaft model introduced by Espinosa et al., 2003 to explain Pioneer and Voyager magnetometer data. Anomalous transport here proposed could originate from a localized ionospheric conductivity anomaly. The resulting cyclic stress modulates the current in the current sheet and can account for its north-south excursions. The convection patterns proposed also imply that corotating, field-aligned currents would be a basic feature of the Saturn system.

  11. X-ray emission from Saturn

    CERN Document Server

    Ness, J U; Wolk, S J; Dennerl, K; Burwitz, V

    2004-01-01

    We report the first unambiguous detection of X-ray emission originating from Saturn with a Chandra observation, duration 65.5 ksec with ACIS-S3. Beyond the pure detection we analyze the spatial distribution of X-rays on the planetary surface, the light curve, and some spectral properties. The detection is based on 162 cts extracted from the ACIS-S3 chip within the optical disk of Saturn. We found no evidence for smaller or larger angular extent. The expected background level is 56 cts, i.e., the count rate is (1.6 +- 0.2) 10^-3 cts/s. The extracted photons are rather concentrated towards the equator of the apparent disk, while both polar caps have a relative photon deficit. The inclination angle of Saturn during the observation was -27 degrees, so that the northern hemisphere was not visible during the complete observation. In addition, it was occulted by the ring system. We found a small but significant photon excess at one edge of the ring system. The light curve shows a small dip twice at identical phases,...

  12. The Hera Saturn Entry Probe Mission

    CERN Document Server

    Mousis, O; Spilker, T; Venkatapathy, E; Poncy, J; Frampton, R; Coustenis, A; Reh, K; Lebreton, J -P; Fletcher, L N; Hueso, R; Amato, M J; Colaprete, A; Ferri, F; Stam, D; Wurz, P; Atreya, S; Aslam, S; Banfield, D J; Calcutt, S; Fischer, G; Holland, A; Keller, C; Kessler, E; Leese, M; Levacher, P; Morse, A; Munoz, O; Renard, J -B; Sheridan, S; Schmider, F -X; Snik, F; Waite, J H; Bird, M; Cavalié, T; Deleuil, M; Fortney, J; Gautier, D; Guillot, T; Lunine, J I; Marty, B; Nixon, C; Orton, G S; Sanchez-Lavega, A

    2015-01-01

    The Hera Saturn entry probe mission is proposed as an M--class mission led by ESA with a contribution from NASA. It consists of one atmospheric probe to be sent into the atmosphere of Saturn, and a Carrier-Relay spacecraft. In this concept, the Hera probe is composed of ESA and NASA elements, and the Carrier-Relay Spacecraft is delivered by ESA. The probe is powered by batteries, and the Carrier-Relay Spacecraft is powered by solar panels and batteries. We anticipate two major subsystems to be supplied by the United States, either by direct procurement by ESA or by contribution from NASA: the solar electric power system (including solar arrays and the power management and distribution system), and the probe entry system (including the thermal protection shield and aeroshell). Hera is designed to perform in situ measurements of the chemical and isotopic compositions as well as the dynamics of Saturn's atmosphere using a single probe, with the goal of improving our understanding of the origin, formation, and ev...

  13. Estimating the mass of Saturn's B ring

    Science.gov (United States)

    Hedman, Matthew M.; Nicholson, Philip D.

    2016-10-01

    The B ring is the brightest and most opaque of Saturn's rings, but it is also amongst the least well understood because basic parameters like its surface mass density have been poorly constrained. Elsewhere in the rings, spiral density waves driven by resonances with Saturn's various moons provide precise and robust mass density estimates, but for most the B ring extremely high opacities and strong stochastic optical depth variations obscure the signal from these wave patterns. We have developed a new wavelet-based technique that combines data from multiple stellar occultations (observed by the Visual and Infrared Mapping Spectrometer instrument onboard the Cassini spacecraft) that has allowed us to identify signals that appear to be due to waves generated by the strongest resonances in the central and outer B ring. These wave signatures yield new estimates of the B-ring's mass density and indicate that the B-ring's total mass could be quite low, between 1/3 and 2/3 the mass of Saturn's moon Mimas.

  14. Saturn's Exploration Beyond Cassini-Huygens

    CERN Document Server

    Guillot, Tristan; Charnoz, Sébastien; Dougherty, Michele K; Read, Peter

    2009-01-01

    For its beautiful rings, active atmosphere and mysterious magnetic field, Saturn is a fascinating planet. It also holds some of the keys to understanding the formation of our Solar System and the evolution of giant planets in general. While the exploration by the Cassini-Huygens mission has led to great advances in our understanding of the planet and its moons, it has left us with puzzling questions: What is the bulk composition of the planet? Does it have a helium core? Is it enriched in noble gases like Jupiter? What powers and controls its gigantic storms? We have learned that we can measure an outer magnetic field that is filtered from its non-axisymmetric components, but what is Saturn's inner magnetic field? What are the rings made of and when were they formed? These questions are crucial in several ways: a detailed comparison of the compositions of Jupiter and Saturn is necessary to understand processes at work during the formation of these two planets and of the Solar System. This calls for the contin...

  15. Suprathermal Electrons at Saturn's Bow Shock

    Science.gov (United States)

    Masters, A.; Sulaiman, A. H.; Sergis, N.; Stawarz, L.; Fujimoto, M.; Coates, A. J.; Dougherty, M. K.

    2016-07-01

    The leading explanation for the origin of galactic cosmic rays is particle acceleration at the shocks surrounding young supernova remnants (SNRs), although crucial aspects of the acceleration process are unclear. The similar collisionless plasma shocks frequently encountered by spacecraft in the solar wind are generally far weaker (lower Mach number) than these SNR shocks. However, the Cassini spacecraft has shown that the shock standing in the solar wind sunward of Saturn (Saturn's bow shock) can occasionally reach this high-Mach number astrophysical regime. In this regime Cassini has provided the first in situ evidence for electron acceleration under quasi-parallel upstream magnetic conditions. Here we present the full picture of suprathermal electrons at Saturn's bow shock revealed by Cassini. The downstream thermal electron distribution is resolved in all data taken by the low-energy electron detector (CAPS-ELS, 18 keV) measured a suprathermal electron signature at 31 of 508 crossings, where typically only the lowest energy channels (process involves interaction with whistler waves at the shock front, and becomes possible for all upstream magnetic field orientations at high Mach numbers like those of the strong shocks around young SNRs. A future dedicated study will analyze the rare crossings with evidence for relativistic electrons (up to ˜1 MeV).

  16. The auroral footprint of Enceladus on Saturn.

    Science.gov (United States)

    Pryor, Wayne R; Rymer, Abigail M; Mitchell, Donald G; Hill, Thomas W; Young, David T; Saur, Joachim; Jones, Geraint H; Jacobsen, Sven; Cowley, Stan W H; Mauk, Barry H; Coates, Andrew J; Gustin, Jacques; Grodent, Denis; Gérard, Jean-Claude; Lamy, Laurent; Nichols, Jonathan D; Krimigis, Stamatios M; Esposito, Larry W; Dougherty, Michele K; Jouchoux, Alain J; Stewart, A Ian F; McClintock, William E; Holsclaw, Gregory M; Ajello, Joseph M; Colwell, Joshua E; Hendrix, Amanda R; Crary, Frank J; Clarke, John T; Zhou, Xiaoyan

    2011-04-21

    Although there are substantial differences between the magnetospheres of Jupiter and Saturn, it has been suggested that cryovolcanic activity at Enceladus could lead to electrodynamic coupling between Enceladus and Saturn like that which links Jupiter with Io, Europa and Ganymede. Powerful field-aligned electron beams associated with the Io-Jupiter coupling, for example, create an auroral footprint in Jupiter's ionosphere. Auroral ultraviolet emission associated with Enceladus-Saturn coupling is anticipated to be just a few tenths of a kilorayleigh (ref. 12), about an order of magnitude dimmer than Io's footprint and below the observable threshold, consistent with its non-detection. Here we report the detection of magnetic-field-aligned ion and electron beams (offset several moon radii downstream from Enceladus) with sufficient power to stimulate detectable aurora, and the subsequent discovery of Enceladus-associated aurora in a few per cent of the scans of the moon's footprint. The footprint varies in emission magnitude more than can plausibly be explained by changes in magnetospheric parameters--and as such is probably indicative of variable plume activity.

  17. Jovian-like aurorae on Saturn.

    Science.gov (United States)

    Stallard, Tom; Miller, Steve; Melin, Henrik; Lystrup, Makenzie; Cowley, Stan W H; Bunce, Emma J; Achilleos, Nicholas; Dougherty, Michele

    2008-06-19

    Planetary aurorae are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. Earth's main auroral oval is formed through interactions with the solar wind, whereas that at Jupiter is formed through interactions with plasma from the moon Io inside its magnetic field (although other processes form aurorae at both planets). At Saturn, only the main auroral oval has previously been observed and there remains much debate over its origin. Here we report the discovery of a secondary oval at Saturn that is approximately 25 per cent as bright as the main oval, and we show this to be caused by interaction with the middle magnetosphere around the planet. This is a weak equivalent of Jupiter's main oval, its relative dimness being due to the lack of as large a source of ions as Jupiter's volcanic moon Io. This result suggests that differences seen in the auroral emissions from Saturn and Jupiter are due to scaling differences in the conditions at each of these two planets, whereas the underlying formation processes are the same.

  18. A Long-lived Cyclone In Saturn's Atmosphere: Observations And Models

    Science.gov (United States)

    Del Rio Gaztelurrutia, Teresa; Legarreta, J.; Hueso, R.; Pérez-Hoyos, S.; Sánchez-Lavega, A.

    2009-09-01

    The atmospheres of the Giant Planets Jupiter and Saturn possess large numbers of atmospheric vortices. On Jupiter, anticyclones are generally long-lived structures while cyclones survive a much shorter time. A long term survey of images of Saturn atmosphere obtained by the Cassini ISS camera has revealed the presence of a long-lived cyclone in Saturn's southern hemisphere during at least four years, making this vortex the longest lived cyclone on either Jupiter or Saturn. We find that the vortex drifts following the wind profile, with changes in velocity following changes of latitude. During the four years of our survey its size remained essentially constant, and there was no other structure of comparable size at its latitude. Internal circulation is cyclonic, with a maximum velocity of 20±5 m/s and an average vorticity of 4·10-5 s-1, an order of magnitude lower than planetary vorticity, but only slightly higher than the ambient vorticity. Photometric analysis shows that the vortex is located at a slightly lower altitude than its surroundings, at an average of 10-20 mbar below adjacent clouds. Finally, EPIC simulations of the vortex that reproduce its behavior imply a Rossby deformation radius of 2000 km in the weather layer (1 - 10 bar), consistent with the size of the cyclone. The long-lifetime of this cyclonic spot is surprising in view of its low tangential velocity and it suggests that low dissipation conditions prevail at mid-latitudes in Saturn's upper troposphere. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

  19. Light curves, Spherical and Bond albedos of Jupiter, Saturn, and exoplanets.

    Science.gov (United States)

    Dyudina, U.

    2015-12-01

    We estimate how the light curve and stellar light reflection of a planet depends on forward and backward scattering, which was observed on Jupiter and Saturn. We fit analytical scattering phase function to Pioneer 10 and 11 spacecraft observations of Jupiter at 0.64 μm and Saturn at 0.64 and 0.44 μm and to Cassini spacecraft observations of Jupiter at 0.938 μm atmospheric window, 0.889 μm CH4 absorption band, and 0.258 μm UV filter. Using scattering ray-tracing model of a planet by Dyudina et al. (2005)*, the images of the planets with different scattering properties are simulated to calculate the reflected luminosity as it varies with scattering phase to produce full-orbit light curves. We compare the light curve shapes and total reflection integrated in all directions (spherical albedos) for Jupiter and Saturn with the ones for planets with Lambertian and semi-infinite Rayleigh-scattering atmosphere. Saturn-like and especially Jupiter-like atmosphere produces light curves that are several times fainter at half-phase than does a Lambertian planet, given the same brightness at transit. The spherical albedo (and hence the wavelengh-integrated Bond albedo) is lower than for a Lambertian planet. Corresponding absorption of the stellar light and planet's heating rate would be higher than estimated for Lambertian planets, especially for bright planets. In extreme case of Jupiter-like scattering at 0.64 μm Lambertian assumption can overestimate spherical albedo by a factor of ˜1.5. We will discuss how the light curves and absorption for planets covered by atmospheres would differ from the light curves of rocky planet without atmosphere. * Dyudina, U. A., et al., Phase Light Curves for Extrasolar Jupiters and Saturns. ApJ, 618, 973-986, 2005

  20. Resonance capture and Saturn's rings

    Energy Technology Data Exchange (ETDEWEB)

    Patterson, C.W.

    1986-05-01

    We have assigned the resonances apparently responsible for the stabilization of the Saturn's shepherd satellites and for the substructure seen in the F-ring and the ringlets in the C-ring. We show that Saturn's narrow ringlets have a substructure determined by three-body resonances with Saturn's ringmoons and the sun. We believe such resonances have important implications to satellite formation. 17 refs., 1 fig., 1 tab.

  1. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    CERN Document Server

    Dyudina, Ulyana; Li, Liming; Kopparla, Pushkar; Yung, Yuk L; Ingersoll, Andrew P; Dones, Luke

    2015-01-01

    We estimate how the light curve and total stellar heating of a planet depend on forward and backward scattering clouds. To do that, we construct light curves for Jupiter- and Saturn-like planet based on observations. We fit analytical functions to the reflected brightness of Jupiter's and Saturn's surface versus planet's phase. We use Pioneer and Cassini spacecraft images to estimate these functions. These observations cover broad bands at 0.59-0.72 microns and 0.39-0.5 microns, and narrow bands at 0.938 microns (atmospheric window), 0.889 microns (CH4 absorption band), and 0.24-0.28 microns. We simulate the images of the planets at different phases with ray-tracing model of a planet by Dyudina et al. (2005). The full-disk luminosity of these simulated images changes with planet's phase producing the full-orbit light curves. We also derive total planet's reflection integrated in all directions (spherical albedos) for Jupiter, Saturn, and for planets with Lambertian and Rayleigh-scattering atmosphere. For Jupi...

  2. Correction terms for the thermodynamics of a black Saturn

    Energy Technology Data Exchange (ETDEWEB)

    Faizal, Mir, E-mail: f2mir@uwaterloo.ca [Department of Physics and Astronomy, University of Waterloo, Waterloo, ON N2L 3G1 (Canada); Pourhassan, Behnam, E-mail: b.pourhassan@du.ac.ir [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of)

    2015-12-17

    In this paper, we will analyze the effects of thermal fluctuations on the stability of a black Saturn. The entropy of the black Saturn will get corrected due to these thermal fluctuations. We will demonstrate that the correction term generated by these thermal fluctuations is a logarithmic term. Then we will use this corrected value of the entropy to obtain bounds for various parameters of the black Saturn. We will also analyze the thermodynamical stability of the black Saturn in presence of thermal fluctuations, using this corrected value of the entropy.

  3. Saturn's Magnetosphere, Rings, and Inner Satellites.

    Science.gov (United States)

    VAN Allen, J A; Thomsen, M F; Randall, B A; Rairden, R L; Grosskreutz, C L

    1980-01-25

    Our 31 August to 5 September 1979 observations together with those of the other Pioneer 11 investigators provide the first credible discovery of the magnetosphere of Saturn and many detailed characteristics thereof. In physical dimensions and energetic charged particle population, Saturn's magnetosphere is intermediate between those of Earth and Jupiter. In terms of planetary radii, the scale of Saturn's magnetosphere more nearly resembles that of Earth and there is much less inflation by entrapped plasma than in the case at Jupiter. The orbit of Titan lies in the outer fringes of the magnetosphere. Particle angular distributions on the inbound leg of the trajectory (sunward side) have a complex pattern but are everywhere consistent with a dipolar magnetic field approximately perpendicular to the planet's equator. On the outbound leg (dawnside) there are marked departures from this situation outside of 7 Saturn radii (Rs), suggesting an equatorial current sheet having both longitudinal and radial components. The particulate rings and inner satellites have a profound effect on the distribution of energetic particles. We find (i) clear absorption signatures of Dione and Mimas; (ii) a broad absorption region encompassing the orbital radii of Tethys and Enceladus but probably attributable, at least in part, to plasma physical effects; (iii) no evidence for Janus (1966 S 1) (S 10) at or near 2.66 Rs; (iv) a satellite of diameter greater, similar 170 kilometers at 2.534 R(s) (1979 S 2), probably the same object as that detected optically by Pioneer 11 (1979 S 1) and previously by groundbased telescopes (1966 S 2) (S 11); (v) a satellite of comparable diameter at 2.343 Rs (1979 S 5); (vi) confirmation of the F ring between 2.336 and 2.371 Rs; (vii) confirmation of the Pioneer division between 2.292 and 2.336 Rs; (viii) a suspected satellite at 2.82 Rs (1979 S 3); (ix) no clear evidence for the E ring though its influence may be obscured by stronger effects; and (x) the

  4. The 2010 Saturn's Great White Spot: Observations and models

    Science.gov (United States)

    Sanchez-Lavega, A.

    2011-12-01

    On December 5, 2010, a major storm erupted in Saturn's northern hemisphere at a planetographic latitude of 37.7 deg [1]. These phenomena are known as "Great White Spots" (GWS) and they have been observed once per Saturn year since the first case confidently reported in 1876. The last event occurred at Saturn's Equator in 1990 [2]. A GWS differs from similar smaller-scale storms in that it generates a planetary-scale disturbance that spreads zonally spanning the whole latitude band. We report on the evolution and motions of the 2010 GWS and its associated disturbance during the months following the outbreak, based mainly on high quality images obtained in the visual range submitted to the International Outer Planet Watch PVOL database [3], with the 1m telescope at Pic-du-Midi Observatory and the 2.2 m telescope at Calar Alto Observatory. The GWS "head source" extinguished by June 2011 implying that it survived about 6 months. Since this source is assumed to be produced by water moist convection, a reservoir of water vapor must exist at a depth of 10 bar and at the same time a disturbance producing the necessary convergence to trigger the ascending motions. The high temporal sampling and coverage allowed us to study the dynamics of the GWS in detail and the multi-wavelength observations provide information on its cloud top structure. We present non-linear simulations using the EPIC code of the evolution of the potential vorticity generated by a continuous Gaussian heat source extending from 10 bar to about 1 bar, that compare extraordinary well to the observed cloud field evolution. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. The presentation is done on behalf of the team listed in Reference [1]. [1]Sánchez-Lavega A., et al., Nature, 475, 71-74 (2011) [2]Sánchez-Lavega A., et al., Nature, 353, 397-401 (1991) [3]Hueso R., et al., Planet. Space Sci., 58, 1152-1159 (2010).

  5. A season in Saturn's rings: Cycling, recycling and ring history

    Science.gov (United States)

    Esposito, L. W.; Meinke, B. K.; Albers, N.; Sremcevic, M.

    2012-04-01

    Cassini experiments have watched Saturn's ring system evolve before our eyes. Images and occultations show changes and transient events. The rings are a dynamic and complex geophysical system, incompletely modeled as a single-phase fluid. Key Cassini observations: High resolution images show straw, propellers, embedded moonlets, and F ring objects. Multiple UVIS, RSS and VIMS occutlations indicate multimodal ringlet and edge structure, including free and forced modes along with stochastic perturbations that are most likely caused by nearby mass concentrations. Vertical excursions are evident at ring edges and in other perturbed regions. The rings are occasionally hit by meteorites that leave a signature that may last centuries; meteoritic dust pollutes the rings. Temperature, reflectance and transmission spectra are influenced by the dynamical state of the ring particles. Saturn's Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry. Sub-kilometer structure in power spectral analysis: Wavelet analysis shows features in the strongest density waves and at the shepherded outer edge of the B ring. Edges are variable as shown by multiple occultations and occultations of double stars. F ring kittens: 25 features seen in the first 102 occultations show a weak correlation with Prometheus location. We interpret these features as temporary aggregations. Simulation results indicate that accretion must be enhanced to match the kittens' size distribution. Images show that Prometheus triggers the formation of transient objects. Propellers and ghosts: Occulations and images provide evidence for small moonlets in the A, B and C rings. These indicate accretion occurs inside the classical Roche limit. Implications

  6. Overview of the Cassini In-Situ Observations of Auroral Field-Aligned Currents During the 2013 Saturn Aurora Campaign

    Science.gov (United States)

    Bunce, E. J.; Badman, S. V.; Cowley, S. W.; Dougherty, M. K.; Gurnett, D. A.; Jinks, S.; Kurth, W. S.; Mitchell, D. G.; Nichols, J. D.; Provan, G.; Pryor, W. R.

    2013-12-01

    The Saturn Aurora Campaign 2013 is a coordinated effort to provide a clearer understanding of Saturn's auroral emissions at multiple wavelengths in the upper atmosphere, and their associated magnetospheric signatures and dynamics. Structures such as Corotating Interaction Regions (CIRs) are known to play a significant role in the modulation of Saturn's auroral emissions via abrupt changes in the dynamic pressure associated with forward shocks at the start of the CIR compression regions. Recent observations from the Cassini spacecraft at Saturn have also taught us that the 'magnetosphere oscillations' observed in magnetic field perturbations in the northern and southern hemispheres, which are associated with the SKR modulations in each hemisphere, also significantly modulate the magnetosphere and auroral emissions. Here we present an overview of the in situ magnetosphere measurements during the campaign, along with an overview of the solar wind conditions upstream of Saturn inferred from the Saturn Kilometric Radiation (SKR) emissions. We will discuss evidence of the high-latitude field-aligned currents and plasma boundaries (e.g. the open-closed field line (or related) boundary) from the magnetic field data, plasma signatures and/or auroral hiss observations (using the Cassini magnetometer-MAG, the Magnetospheric Imaging Instrument-MIMI, and the Radio Plasma Wave Science-RPWS instruments respectively). We will attempt to characterise the morphology and variability (e.g. co-latitude, intensity) of the current system(s) from both the knowledge of the northern or southern magnetosphere oscillation phase (according to the location of the spacecraft) and the inferred solar wind conditions. We will compare these results with available IR/UV auroral images from the campaign.

  7. Overview of the Cassini in-situ magnetosphere measurements and solar wind modelling during the 2013 Saturn Aurora Campaign

    Science.gov (United States)

    Bunce, E. J.; Badman, S. V.; Cowley, S. W. H.; Jinks, S. L.; Provan, G.; Burton, M.; Crary, F. J.; Dougherty, M. K.; Kurth, W. S.; Luhmann, J.; Mitchell, D. G.; Zheng, Y.

    2013-09-01

    The Saturn Aurora Campaign 2013 is a coordinated effort to provide a clearer understanding of Saturn's auroral emissions at multiple wavelengths in the upper atmosphere, and their associated magnetospheric signatures and dynamics. In addition, modelling and Earth-based observations of the solar wind conditions throughout the campaign provide an important insight to the way in which Saturn's magnetosphere responds to the changing conditions in interplanetary space. Structures such as Corotating Interaction Regions (CIRs) are thought to play a significant role in the modulation of Saturn's auroral emissions via abrupt changes in the dynamic pressure associated with forward shocks at the start of the CIR compression regions. Recent observations from the Cassini spacecraft at Saturn have also taught us that the "magnetosphere oscillations" observed in magnetic field perturbations in the northern and southern hemispheres, which are associated with the SKR modulations in each hemisphere, significantly affect the magnetosphere and auroral emissions. During April and May 2013 a combination of the Hubble Space Telescope (HST) ultraviolet (UV) instrument the Advanced Camera for Surveys (ACS), and ground-based infrared (IR) telescopes observed the northern hemisphere auroras, whilst the Cassini spacecraft's remote sensing instruments (the Ultraviolet Imaging Spectrograph-UVIS, the Visual and Infrared Mapping Spectrometer-VIMS, and the Imaging Science SubSystem-ISS) made simultaneous (or near-simultaneous) observations of the UV, IR and visible auroras respectively, in one or other hemisphere. At the same time, the "in situ" instruments on board Cassini measured the magnetic field, plasma populations, and radio plasma wave emissions in Saturn's magnetosphere. Here we present an overview of the in situ magnetosphere measurements during the campaign, along with an overview of the predicted solar wind conditions upstream of Saturn from modeling work. We will discuss the evidence

  8. Saturn's Auroral Response to the Solar Wind: Centrifugal Instability Model

    Science.gov (United States)

    Sittler, Edward C.; Blanc, Michel F.; Richardson, J. D.

    2008-01-01

    We describe a model initially presented by Sittler et al. [2006] which attempts to explain the global response of Saturn's magnetosphere and its corresponding auroral behavior to variations in the solar wind. The model was derived from published simultaneous Hubble Space Telescope (HST) auroral images and Cassini upstream measurements taken during the month of January 2004. These observations show a direct correlation between solar wind dynamic pressure and (1) auroral brightening toward dawn local time, (2) an increase of rotational movement of auroral features to as much as 75% of the corotation speed, (3) the movement of the auroral oval to higher latitudes and (4) an increase in the intensity of Saturn Kilometric Radiation (SKR). This model is an alternative to the reconnection model of Cowley et al. [2004a,b; 2005] which is more Earth-like while ours stresses rotation. If angular momentum is conserved in a global sense, then when compressed the magnetosphere will tend to spin up and when it expands will tend to spin down. With the plasma sheet outer boundary at L approximates 15 we argue this region to be the dominant source region for the precipitating particles. If radial transport is dominated by centrifugal driven flux tube interchange motions, then when the magnetosphere spins up, outward transport will increase, the precipitating particles will move radially outward and cause the auroral oval to move to higher latitudes as observed. The Kelvin-Helmholtz instability may contribute to the enhanced emission along the dawn meridian as observed by HST. We present this model in the context of presently published observations by Cassini.

  9. Lightning on Saturn observed by Cassini ISS and RPWS during 2006-2009

    Science.gov (United States)

    Dyudina, U.; Ingersoll, A. P.; Ewald, S. P.; Porco, C.; Fischer, G.

    2009-12-01

    Throughout the Cassini mission thousands of images had been taken on the night side of saturn in search for optical lightning flashes. No flashes were unambiguously detected so far. The reasons for that may be the lightning located too deep and covered by the thick clouds, and thus faint as seen from the orbit, cosmic rays hitting the detector that could be confused with lightning, and the ringshine compromising the observations both by potential saturation of the images and by illuminating small convective clouds whose shape in reflected light can be confused with lightning flash. The only time of nearly zero ringshine in the 30-year-long Saturnian year is during the equinox, which happened on August 11, 2009. Cassini ISS took 211 lightning search images within ten days from the equinox. We will report on possible lightning detections in those images and also in the previous Cassini ISS lightning searches. We also report on Cassini Imaging Science Subsystem (ISS) and Radio and Plasma Wave Science (RPWS) observations that indicate lightning on Saturn. A lightning storm that began in 2007 lasted for 7.5 months. Another storm started in mid-January 2009 and was still active in August of 2009. We will compare these recent storms with those studied by Cassini in 2004 and 2006. In all cases, radio emissions (Saturn Electrostatic Discharges, or SEDs) occur when a rare bright cloud erupts at a unique latitude ˜ 35 degrees South (planetocentric).The cloud typically lasts for several weeks to months, and then both the cloud and the SEDs disappear.The cloud and SED's reappear synchronously after being inactive for several months. The SEDs are periodic with roughly Saturn's rotation rate, and show correlated phase relative to the times when the clouds are seen on the spacecraft-facing side of the planet. The storm clouds erupt to unusually high altitudes and then slowly descend and spread.The eruption lasts for less than a day during which time the SEDs reach their maximum

  10. Saturn kilometric radiation intensities during the Saturn auroral campaign of 2013

    Science.gov (United States)

    Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Lamy, L.; Dougherty, M. K.; Nichols, J.; Bunce, E. J.; Pryor, W.; Baines, K.; Stallard, T.; Melin, H.; Crary, F. J.

    2016-01-01

    The Saturn auroral campaign carried out in the spring of 2013 used multiple Earth-based observations, remote-sensing observations from Cassini, and in situ-observations from Cassini to further our understanding of auroras at Saturn. Most of the remote sensing and Earth-based measurements are, by nature, not continuous. And, even the in situ measurements, while continuously obtained, are not always obtained in regions relevant to the study of the aurora. Saturn kilometric radiation, however, is remotely monitored nearly continuously by the Radio and Plasma Wave Science instrument on Cassini. This radio emission, produced by the cyclotron maser instability, is tightly tied to auroral processes at Saturn as are auroral radio emissions at other planets, most notably Jupiter and Earth. This paper provides the time history of the intensity of the radio emissions through the auroral campaign as a means of understanding the temporal relationships between the sometimes widely spaced observations of the auroral activity. While beaming characteristics of the radio emissions are known to prevent single spacecraft observations of this emission from being a perfect auroral activity indicator, we demonstrate a good correlation between the radio emission intensity and the level of UV auroral activity, when both measurements are available.

  11. Modeling the disequilibrium species for Jupiter and Saturn: Implications for Juno and Saturn entry probe

    Science.gov (United States)

    Wang, D.; Lunine, J. I.; Mousis, O.

    2016-12-01

    Disequilibrium species have been used previously to probe the deep water abundances and the eddy diffusion coefficient for giant planets. In this abstract, we present a diffusion-kinetics code that predicts the abundances of disequilibrium species in the tropospheres of Jupiter and Saturn with updated thermodynamic and kinetic data. The dependence on the deep water abundance and the eddy diffusion coefficient is investigated. We quantified the disagreements in CO kinetics that comes from using different reaction networks and identified C2H6 as a useful tracer for the eddy diffusion coefficient. We first apply an H/P/O reaction network to Jupiter and Saturn's atmospheres and suggest a new PH3 destruction pathway. New chemical pathways for SiH4 and GeH4 destruction are also suggested, and another AsH3 destruction pathway is investigated thanks to new thermodynamic and kinetic data. These new models should enhance the interpretation of the measurement of disequilibrium species by JIRAM on board Juno and allow disentangling between methods for constraining the Saturn's deep water abundance with the Saturn entry probes envisaged by NASA or ESA.

  12. On plasma convection in Saturn's magnetosphere

    Science.gov (United States)

    Livi, Roberto

    We use CAPS plasma data to derive particle characteristics within Saturn's inner magnetosphere. Our approach is to first develop a forward-modeling program to derive 1-dimensional (1D) isotropic plasma characteristics in Saturn's inner, equatorial magnetosphere using a novel correction for the spacecraft potential and penetrating background radiation. The advantage of this fitting routine is the simultaneous modeling of plasma data and systematic errors when operating on large data sets, which greatly reduces the computation time and accurately quantifies instrument noise. The data set consists of particle measurements from the Electron Spectrometer (ELS) and the Ion Mass Spectrometer (IMS), which are part of the Cassini Plasma Spectrometer (CAPS) instrument suite onboard the Cassini spacecraft. The data is limited to peak ion flux measurements within +/-10° magnetic latitude and 3-15 geocentric equatorial radial distance (RS). Systematic errors such as spacecraft charging and penetrating background radiation are parametrized individually in the modeling and are automatically addressed during the fitting procedure. The resulting values are in turn used as cross-calibration between IMS and ELS, where we show a significant improvement in magnetospheric electron densities and minor changes in the ion characteristics due to the error adjustments. Preliminary results show ion and electron densities in close agreement, consistent with charge neutrality throughout Saturn's inner magnetosphere and confirming the spacecraft potential to be a common influence on IMS and ELS. Comparison of derived plasma parameters with results from previous studies using CAPS data and the Radio And Plasma Wave Science (RPWS) investigation yields good agreement. Using the derived plasma characteristics we focus on the radial transport of hot electrons. We present evidence of loss-free adiabatic transport of equatorially mirroring electrons (100 eV - 10 keV) in Saturn's magnetosphere between

  13. Through Saturn's Haze, a First Look at Titan

    Institute of Scientific and Technical Information of China (English)

    John Noble Wilford; 李严

    2004-01-01

    @@ Dazzling as Saturn and its rings① are, to scientists the most intriguing②target of exploration by the Cassini③ spacecraft is Saturn's giant moon④ Titan.At a diameter of 3,200 miles, it is larger than the planet Mercury⑤, and is the only moon in the solar system with a substantial atmosphere.

  14. X-Rays from Saturn and its Rings

    Science.gov (United States)

    Bhardwaj, Anil; Elsner, Ron F.; Waite, J. Hunter; Gladstone, G. Randall; Cravens, Tom E.; Ford, Peter G.

    2005-01-01

    In January 2004 Saturn was observed by Chandra ACIS-S in two exposures, 00:06 to 11:00 UT on 20 January and 14:32 UT on 26 January to 01:13 UT on 27 January. Each continuous observation lasted for about one full Saturn rotation. These observations detected an X-ray flare from the Saturn's disk and indicate that the entire Saturnian X-ray emission is highly variable -- a factor of $\\sim$4 variability in brightness in a week time. The Saturn X-ray flare has a time and magnitude matching feature with the solar X-ray flare, which suggests that the disk X-ray emission of Saturn is governed by processes happening on the Sun. These observations also unambiguously detected X-rays from Saturn's rings. The X-ray emissions from rings are present mainly in the 0.45-0.6 keV band centered on the atomic OK$\\alpha$ fluorescence line at 525 eV: indicating the production of X-rays due to oxygen atoms in the water icy rings. The characteristics of X-rays from Saturn's polar region appear to be statistically consistent with those from its disk X-rays, suggesting that X-ray emission from the polar cap region might be an extension of the Saturn disk X-ray emission.

  15. Thermal Infrared Spectroscopy of Saturn and Titan from Cassini

    Science.gov (United States)

    Jennings, Donald E.; Brasunas, J. C.; Carlson, R. C.; Flasar, F. M.; Kunde, V. G.; Mamoutkine, A. A.; Nixon, A.; Pearl, J. C.; Romani, P. N.; Simon-Miller, A. A.; Bjoraker, G. L.

    2009-01-01

    The Cassini spacecraft completed its nominal mission at Saturn in 2008 and began its extended mission. Cassini carries the Composite Infrared Spectrometer (CIRS); a Fourier transform spectrometer that measures the composition, thermal structure and dynamics of the atmospheres of Saturn and Titan, and also the temperatures of other moons and the rings.

  16. Sustained lobe reconnection in Saturn's magnetotail

    Science.gov (United States)

    Thomsen, M. F.; Jackman, C. M.; Mitchell, D. G.; Hospodarsky, G.; Kurth, W. S.; Hansen, K. C.

    2015-12-01

    The degree to which solar wind driving may affect Saturn's magnetosphere is not yet fully understood. We present observations that suggest that under some conditions the solar wind does govern the character of the plasma sheet in Saturn's outer magnetosphere. On 16 September 2006, the Cassini spacecraft, at a radial distance of 37 Rs near local midnight, observed a sunward flowing ion population for ~5 h, which was accompanied by enhanced Saturn Kilometric Radiation emissions. We interpret this beam as the outflow from a long-lasting episode of Dungey-type reconnection, i.e., reconnection of previously open flux containing magnetosheath material. The beam occurred in the middle of a several-day interval of SKR activity and enhanced lobe magnetic field strength, apparently caused by the arrival of a solar wind compression region with significantly higher than average dynamic pressure. The arrival of the high-pressure solar wind also marked a change in the composition of the plasma-sheet plasma, from water-group-dominated material clearly of inner-magnetosphere origin to material dominated by light-ion composition, consistent with captured magnetosheath plasma. This event suggests that under the influence of prolonged high solar wind dynamic pressure, the tail plasma sheet, which normally consists of inner-magnetospheric plasma, is eroded away by ongoing reconnection that then involves open lobe field lines. This process removes open magnetic flux from the lobes and creates a more Earth-like, Dungey-style outer plasma sheet dominantly of solar wind origin. This behavior is potentially a recurrent phenomenon driven by repeating high-pressure streams (corotating interaction regions) in the solar wind, which also drive geomagnetic storms at Earth.

  17. Saturn kilometric radiation periodicity after equinox

    Science.gov (United States)

    Fischer, G.; Gurnett, D. A.; Kurth, W. S.; Ye, S.-Y.; Groene, J. B.

    2015-07-01

    The rotation period of Saturn's magnetosphere was found to vary with time, and changing periodicities were identified in magnetic fields, radio emissions, and charged particles. Here we analyze the varying period of Saturn kilometric radiation (SKR) from 2009 to early 2013, i.e. mainly after Saturn equinox of August 2009. A periodicity analysis is first applied to the complete SKR signal, and second to SKR intensities separated by spacecraft latitude and wave polarization, attributed to SKR from the northern and southern hemisphere. Our analyses are done with the tracking filter approach of Gurnett et al. (Gurnett et al. [2009a]. Geophys. Res. Lett. 36, L16102) and by simply tracing the phases of normalized SKR intensity maxima (north and south) with time. It is shown that SKR periods from the northern and southern hemisphere converged during 2009, crossed shortly after equinox, and coalesced in spring 2010. We will show that SKR from both hemispheres not only exhibited similar periods, but also similar phases from March 2010 until February 2011 and from August 2011 until June 2012. The in-between time interval (March to July 2011) shows a slowdown of the southern SKR rotation rate and a slight increase in rotation speed for the northern SKR before rotation rates and phases become equal again in August 2011. We also identify SKR signals where the modulation phase deviation exceeds one rotation each time Cassini completes one orbit, i.e. this is consistent with the characteristic of a rotating signal. However, the main SKR modulation signals from 2009 to 2012 can be viewed as being clock-like with no correction needed for the derived periods. A comparison of SKR periodicities after equinox to the planetary period oscillations of the magnetic field shows major differences, and we compare SKR phases to magnetic field phases to explain the deviations.

  18. Non-Linear Dynamics of Saturn's Rings

    Science.gov (United States)

    Esposito, L. W.

    2015-12-01

    Non-linear processes can explain why Saturn's rings are so active and dynamic. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw', as observed ny Cassini cameras. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon-triggered clumping at perturbed regions in Saturn's rings creates both high velocity dispersion and large aggregates at these distances, explaining both small and large particles observed there. This confirms the triple architecture of ring particles: a broad size distribution of particles; these aggregate into temporary rubble piles; coated by a regolith of dust. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating the Markov chain as an asymmetric random walk with reflecting boundaries allows us to determine the power law index from

  19. 德国特色店:Saturn

    Institute of Scientific and Technical Information of China (English)

    文子

    2005-01-01

    @@ SATURN,德文是土星的意思,代表着巨大广阔.而有着这个名称的电脑店,绝对堪称电器专卖的航母.它的经营范围不仅是电脑,销售产品几乎涵盖了所有的多媒体配件、家电类的产品,在德国经济一片风雨飘摇的形势下,它是如何能够在该行业一枝独秀的?

  20. 德国特色店:Saturn

    Institute of Scientific and Technical Information of China (English)

    文子

    2005-01-01

      SATURN,德文是土星的意思,代表着巨大广阔.而有着这个名称的电脑店,绝对堪称电器专卖的航母.它的经营范围不仅是电脑,销售产品几乎涵盖了所有的多媒体配件、家电类的产品,在德国经济一片风雨飘摇的形势下,它是如何能够在该行业一枝独秀的?……

  1. The Saturn System's Icy Satellites: New Results from Cassini

    Science.gov (United States)

    Lopes-Gautier, Rosaly M.; Buratti, Bonnie; Hendrix, A. R.

    2008-01-01

    Cassini-Huygens is a multidisciplinary, international planetary mission consisting of an orbiting spacecraft and a probe. The Huygens probe successfully landed on Titan's surface on January 14, 2005, while the orbiter has performed observations of Saturn, its rings, satellites, and magnetosphere since it entered orbit around Saturn on July 1, 2004. The Cassini mission has been prolific in its scientific discoveries about the Saturn system. In this special section, we present new mission results with a focus on the 'icy satellites,' which we define as all Saturn's moons with the exception of Titan. The results included in this section have come out of the Cassini SOST--Satellites Orbiter Science Team--a multi-instrument and multidiscipline group that works together to better understand the icy satellites and their interactions with Saturn and its rings. Other papers included in this issue present ground-based observations and interior modeling of these icy moons.

  2. A statistical analysis of the location and width of Saturn's southern auroras

    Directory of Open Access Journals (Sweden)

    S. V. Badman

    2006-12-01

    Full Text Available A selection of twenty-two Hubble Space Telescope images of Saturn's ultraviolet auroras obtained during 1997–2004 has been analysed to determine the median location and width of the auroral oval, and their variability. Limitations of coverage restrict the analysis to the southern hemisphere, and to local times from the post-midnight sector to just past dusk, via dawn and noon. It is found that the overall median location of the poleward and equatorward boundaries of the oval with respect to the southern pole are at ~14° and ~16° co-latitude, respectively, with a median latitudinal width of ~2°. These median values vary only modestly with local time around the oval, though the poleward boundary moves closer to the pole near noon (~12.5° such that the oval is wider in that sector (median width ~3.5° than it is at both dawn and dusk (~1.5°. It is also shown that the position of the auroral boundaries at Saturn are extremely variable, the poleward boundary being located between 2° and 20° co-latitude, and the equatorward boundary between 6° and 23°, this variability contrasting sharply with the essentially fixed location of the main oval at Jupiter. Comparison with Voyager plasma angular velocity data mapped magnetically from the equatorial magnetosphere into the southern ionosphere indicates that the dayside aurora lie poleward of the main upward-directed field-aligned current region associated with corotation enforcement, which maps to ~20°–24° co-latitude, while agreeing reasonably with the position of the open-closed field line boundary based on estimates of the open flux in Saturn's tail, located between ~11° and ~15°. In this case, the variability in location can be understood in terms of changes in the open flux present in the system, the changes implied by the Saturn data then matching those observed at Earth as fractions of the total planetary flux. We infer that the broad (few degrees diffuse auroral emissions

  3. Saturn Trojans: a dynamical point of view

    Science.gov (United States)

    Hou, X. Y.; Scheeres, D. J.; Liu, L.

    2014-01-01

    Different from the usual approach in the inertial frame, the stability problem of fictitious Saturn Trojans is studied in the synodic frame in this paper. First, some numerical facts are shown to allow us to simplify the force model. Then, motion equations centred at the geometrical triangular libration points for the planar S-JS model are derived. Using these equations, the resonance mechanism that causes the instability is studied. We confirm the opinion that the secular resonances and the near-commensurability between the libration frequency and the great inequality are the reasons to cause the instability of motions close to the triangular libration point. By studying the survivability of the long period family and the short period family in the S-JSUN model, the planar stable region far away from the triangular libration point is studied. By frequency analysis of the orbits in the stable region, we are able to find two secular resonances associated with the boundary of the stable region. Three-dimensional motion is also discussed, by starting with the survivability of the vertical period family in the S-JSUN model. The secular resonance that causes the orbit inclination restriction on the Trojans is qualitatively discussed. Lastly, the effects of planetary migrations are briefly studied. With the contribution in this paper, a global picture of the dynamics around the triangular libration points in the Sun-Saturn system perturbed by Jupiter is presented.

  4. Source mechanism of Saturn narrowband emission

    Directory of Open Access Journals (Sweden)

    J. D. Menietti

    2010-04-01

    Full Text Available Narrowband emission (NB is observed at Saturn centered near 5 kHz and 20 kHz and harmonics. This emission appears similar in many ways to Jovian kilometric narrowband emission observed at higher frequencies, and therefore may have a similar source mechanism. Source regions of NB near 20 kHz are believed to be located near density gradients in the inner magnetosphere and the emission appears to be correlated with the occurrence of large neutral plasma clouds observed in the Saturn magnetotail. In this work we present the results of a growth rate analysis of NB emission (~20 kHz near or within a probable source region. This is made possible by the sampling of in-situ wave and particle data. The results indicate waves are likely to be generated by the mode-conversion of directly generated Z-mode emission to O-mode near a density gradient. When the local hybrid frequency is close n fce (n is an integer and fce is the electron cyclotron frequency with n=4, 5 or 6 in our case, electromagnetic Z-mode and weak ordinary (O-mode emission can be directly generated by the cyclotron maser instability.

  5. Satellite And Propeller Migration In Saturn's Rings

    Science.gov (United States)

    Crida, Aurelien; Charnoz, S.; Papaloizou, J.; Salmon, J.

    2009-09-01

    Saturn's rings host satellites like Pan and Daphnis, and smaller bodies like the recently discovered propellers (Tiscareno et al. 2006). These bodies interact gravitationally with the rings. Actually, the resulting perturbations on the ring system have revealed the presence of embedded objects (the Encke and Keeler gaps associated with Pan and Daphnis respectively, the little two-folded structures called propellers tracing the scattering of ring particles by some embedded small objects). Reciprocally, the rings must act on the embedded bodies, leading to their migration. Here, we study how the standard theory of planetary migration applies in Saturn's ring, where the pressure is negligible in contrast with standard protoplanetary disks. Pan and Daphnis should be in standard type II migration, governed by the global disk evolution. Therefore, their presence and position provide constraints on the history of the A-ring, which can be studied using numerical simulations of disk-satellite interactions. The propellers are fully embedded in the disc, and therefore should be subject to type I migration. The simple impulse approximation used by Lin and Papaloi zou (1979) to derive the one-sided torque is particularly suited to this case. Refining their calculation, taking density variations into account, and discussing the possibility for these bodies to enter the type III, runaway regime of migration, we aim at estimating a possible migration rate for these propellers, to be compared to the system life time.

  6. Structures of the Planets Jupiter and Saturn

    CERN Document Server

    Kerley, Gerald I

    2013-01-01

    New equations of state (EOS) for hydrogen, helium, and compounds containing heavier elements are used to construct models for the structures of the planets Jupiter and Saturn. Good agreement with the gravitational moments J2 and J4 is obtained with a model that uses a two-layer gas envelope, in which the inner region is denser than the outer one, together with a small, dense core. It is possible to match J2 with a homogeneous envelope, but an envelope with a denser inner region is needed to match both moments. The two-layer envelope also gives good agreement with the global oscillation data for Jupiter. In Jupiter, the boundary between the inner and outer envelopes occurs at 319 GPa, with an 8% density increase. In Saturn, it occurs at 227 GPa, with a 69% density increase. The differences between the two planets show that the need for a density increase is not due to EOS errors. It is also shown that helium enrichment cannot be the cause of the density increase. The phenomenon can be explained as the result o...

  7. The DISTO Data Acquisition System at SATURNE

    CERN Document Server

    Maggiora, A

    1997-01-01

    The DISTO collaboration has built a large-acceptance magnetic spectrometer designed to provide broad kinematic coverage of multi-particle final states produced in $pp$ scattering. The spectrometer has been installed in the polarized proton beam of the Saturne accelerator in Saclay to study polarization observables in the $\\vec{p} p \\to p K^{+} \\vec{Y}$ ($Y = \\Lambda, and $\\rho$) in $pp$ collisions. The data acquisition system is based on a VME 68030 CPU running the OS/9 operating system, housed in a single VME crate together with the CAMAC interface, the triple port ECL memories, and four RISC R3000 CPU. The digitization of signals from the detectors is made by PCOS III and FERA front-end electronics. Data of several events belonging to a single Saturne extraction are stored in VME triple-port ECL memories using a hardwired fast sequencer. The buffer, optionally filtered by the RISC R3000 CPU, is recorded on a DLT cassette by DAQ CPU using the on-board SCSI interface during the acceleration cycle. Two UNIX wo...

  8. The population of propellers in Saturn's A Ring

    CERN Document Server

    Tiscareno, Matthew S; Hedman, Matthew M; Porco, Carolyn C

    2007-01-01

    We present an extensive data set of ~150 localized features from Cassini images of Saturn's Ring A, a third of which are demonstrated to be persistent by their appearance in multiple images, and half of which are resolved well enough to reveal a characteristic "propeller" shape. We interpret these features as the signatures of small moonlets embedded within the ring, with diameters between 40 and 500 meters. The lack of significant brightening at high phase angle indicates that they are likely composed primarily of macroscopic particles, rather than dust. With the exception of two features found exterior to the Encke Gap, these objects are concentrated entirely within three narrow (~1000 km) bands in the mid-A Ring that happen to be free from local disturbances from strong density waves. However, other nearby regions are similarly free of major disturbances but contain no propellers. It is unclear whether these bands are due to specific events in which a parent body or bodies broke up into the current moonlet...

  9. How Prometheus creates structure in Saturn's F ring.

    Science.gov (United States)

    Murray, Carl D; Chavez, Carlos; Beurle, Kevin; Cooper, Nick; Evans, Michael W; Burns, Joseph A; Porco, Carolyn C

    2005-10-27

    Images of Saturn's narrow and contorted F ring returned by the Cassini spacecraft have revealed phenomena not previously detected in any planetary ring system. The perturbing effect of the inner shepherding satellite, Prometheus, seems to introduce channels through the F ring and a 'streamer'--a line of particles that link the ring to the satellite. The detailed mechanism for the formation of these features has been lacking an explanation. Here we show that these phenomena can be understood in terms of a simple gravitational interaction as Prometheus approaches and recedes from the F ring every 14.7 hours. Our numerical models show that as Prometheus recedes from its closest approach to the F ring, it draws out ring material; one orbital period later, this affected region has undergone keplerian shear and is visible as a channel, in excellent agreement with structures seen in the Cassini images. Prometheus' periodic disruption of the F ring will become more pronounced as the two orbits approach their minimum separation in 2009. The model predicts that the appearance of streamers and the associated channels will vary in a regular fashion on a timescale of one orbital period.

  10. Saturn's F ring: A decade of perturbations and collisions

    Science.gov (United States)

    Murray, Carl D.; Cooper, Nicholas; Attree, Nicholas; Williams, Gareth

    2015-05-01

    We present an overview of the gravitational and collisional processes at work in Saturn's F ring deduced from images obtained by the Imaging Science Subsystem (ISS) on the Cassini spacecraft since 2004. The moon Prometheus exerts the dominant gravitational perturbation on the ring. As well as creating the observed periodic "streamer-channel" structures in the ring, there is evidence that Prometheus also causes the formation and orbital evolution of clumps that can, in turn, perturb local ring particles. We show how Prometheus' effect can be understood in terms of a simple epicyclic model. Jets of material seen emanating from the F ring are produced when objects orbiting nearby collide with material in the core. We show that there are fundamental differences between the larger and smaller jets even though both are caused by collisions. A comparison between the morphology seen in ISS observations and the results of simulations suggests that both the impactors and the core material are in the form of aggregates of material. We present the results of a study of one particular sheared jet and its associated clumps over a two-month interval in early 2008, deriving orbits for the clumps and showing how they change as they encounter Prometheus.

  11. Discovery of Oxygen Kalpha X-ray Emission from the Rings of Saturn

    CERN Document Server

    Bhardwaj, A; Waite, J H; Gladstone, G R; Cravens, T E; Ford, P G; Bhardwaj, Anil; Elsner, Ronald F.; Cravens, Thomas E.; Ford, Peter G.

    2005-01-01

    Using the Advanced CCD Imaging Spectrometer (ACIS), the Chandra X-ray Observatory (CXO) observed the Saturnian system for one rotation of the planet (~37 ks) on 20 January, 2004, and again on 26-27 January, 2004. In this letter we report the detection of X-ray emission from the rings of Saturn. The X-ray spectrum from the rings is dominated by emission in a narrow (~130 eV wide) energy band centered on the atomic oxygen K-alpha fluorescence line at 0.53 keV. The X-ray power emitted from the rings in the 0.49-0.62 keV band is 84 MW, which is about one-third of that emitted from Saturn disk in the photon energy range 0.24-2.0 keV. Our analysis also finds a clear detection of X-ray emission from the rings in the 0.49-0.62 keV band in an earlier (14-15 April, 2003) Chandra ACIS observation of Saturn. Fluorescent scattering of solar X-rays from oxygen atoms in the H2O icy ring material is the likely source mechanism for ring X-rays, consistent with the scenario of solar photo-production of a tenuous ring oxygen at...

  12. Could Jean-Dominique Cassini see the famous division in Saturn's rings?

    CERN Document Server

    Lozi, Julien; Semery, Alain; Lhomé, Emilie; Jacquinod, Sophie; Combes, Michel; Bernardi, Pernelle; Andretta, Rémi; Motisi, Maxime; Bobis, Laurence; Kaftan, Emilie

    2013-01-01

    Nowadays, astronomers want to observe gaps in exozodiacal disks to confirm the presence of exoplanets, or even make actual images of these companions. Four hundred and fifty years ago, Jean-Dominique Cassini did a similar study on a closer object: Saturn. After joining the newly created Observatoire de Paris in 1671, he discovered 4 of Saturn's satellites (Iapetus, Rhea, Tethys and Dione), and also the gap in its rings. He made these discoveries observing through the best optics at the time, made in Italy by famous opticians like Giuseppe Campani or Eustachio Divini. But was he really able to observe this black line in Saturn's rings? That is what a team of optical scientists from Observatoire de Paris - LESIA with the help of Onera and Institut d'Optique tried to find out, analyzing the lenses used by Cassini, and still preserved in the collection of the observatory. The main difficulty was that even if the lenses have diameters between 84 and 239 mm, the focal lengths are between 6 and 50 m, more than the f...

  13. On the Magnetospheric Engine Behind Kilometric Radiation at Earth and Saturn

    Science.gov (United States)

    Brandt, Pontus; Mitchell, Donald

    2014-05-01

    The planets of the solar system display a range of different space environments and solar interaction regimes, from non/weakly magnetized, to magnetized with convective- versus rotation-dominated magnetospheres. All magnetized planets with an appreciable magnetosphere are immersed in a dynamic energetic particle (hot plasma), as well as cold plasma, environment. These five planetary magnetospheres (Earth, Jupiter, Saturn, Uranus and Neptune) are also significant emitters of low-frequency radio waves that are consistent with a cyclotron-maser instability set up in a field-aligned current region. Radio observations in the Kilometric Radiation (AKR) emissions in the ~30-800 kHz range have long been known to be associated with auroral intensifications and magnetospheric substorms. In a similar fashion, recent remote imaging using Energetic Neutral Atoms (ENAs) obtained by the Cassini mission have revealed that the periodic Saturn Kilometric Radiation (SKR) emission from Saturn's high-latitude magnetosphere is highly correlated with simultaneous large-scale injections of energetic particles in the night side magnetosphere. These observations imply that the engine behind the AKR and SKR is current system associated with the planet ward fast plasma flows during an injection and/or the resulting plasma pressure gradients of the heated plasma.

  14. Identification of Saturn-driven bending waves in Saturn's inner C ring

    Science.gov (United States)

    French, Richard; Colwell, Joshua; Nicholson, Phillip; Marouf, Essam; McGhee-French, Colleen; Hedman, Matthew

    2016-07-01

    Saturn's C ring is host to more than a dozen wavelike features whose detailed nature has been a mystery since their discovery in high-resolution Voyager radio occultations of the rings. Rosen et al. (1991 Icarus 93, 25) enumerated several of these, and the list was augmented by Baillié et al. (2011 Icarus 216, 292), based on a detailed analysis of Cassini UVIS stellar occultation profiles. Recently, Hedman and Nicholson (2013 Astron. J. 146, 12; 2014 MNRAS 444, 1369) were able to identify the wavenumbers and pattern speeds for several of the waves. They showed that several Outer Lindblad Resonances (OLR) density waves had properties that were in general quite consistent with the predictions of Marley and Porco (1993 Icarus, 106, 508) and Marley (2014 Icarus, 234, 194) that Saturn's acoustic oscillations had pattern speeds with corresponding resonance radii in the C ring. Hedman and Nicholson also identified a set of Inner Lindblad Resonance density waves with pattern speeds very close to Saturn's rotation period. Finally, French et al. (2016 Icarus, in press) identified an inward-propagating m=2 wave in the Maxwell Ringlet. These new identifications ushered in the field of Kronoseismology -- the probing of the nature of Saturn's interior from the analysis of Saturn-driven waves in the rings. Here, we report the identification of six additional wave features, all in the inner C ring, from Cassini occultation measurements. Two of the waves are OLRs: Baillié feature #5 (B1 = W76.022 (i.e., r=76022 km)) with wavenumber m=-9, and Baillié #9 (B9 = W76.435) with m=-2. The first of these is presumably Saturn-driven, but of unknown origin; W76.435 fits very nicely in the pattern predicted by Marley (2014) for an m=l-2, q=2 internal oscillation. We also report the identification of a new class of Saturn-driven waves: B1 (W74.666), B3 (W74.936), B4 (W74.941), and B6 (W76.234) are all bending waves at Outer Vertical Resonances (OVR) with wavenumbers between m=-4 and m=-9

  15. Saturn's auroral morphology and field-aligned currents during a solar wind compression

    Science.gov (United States)

    Badman, S. V.; Provan, G.; Bunce, E. J.; Mitchell, D. G.; Melin, H.; Cowley, S. W. H.; Radioti, A.; Kurth, W. S.; Pryor, W. R.; Nichols, J. D.; Jinks, S. L.; Stallard, T. S.; Brown, R. H.; Baines, K. H.; Dougherty, M. K.

    2016-01-01

    On 21-22 April 2013, during a coordinated auroral observing campaign, instruments onboard Cassini and the Hubble Space Telescope observed Saturn's aurora while Cassini traversed Saturn's high latitude auroral field lines. Signatures of upward and downward field-aligned currents were detected in the nightside magnetosphere in the magnetic field and plasma measurements. The location of the upward current corresponded to the bright ultraviolet auroral arc seen in the auroral images, and the downward current region was located poleward of the upward current in an aurorally dark region. Within the polar cap magnetic field and plasma fluctuations were identified with periods of ∼20 and ∼60 min. The northern and southern auroral ovals were observed to rock in latitude in phase with the respective northern and southern planetary period oscillations. A solar wind compression impacted Saturn's magnetosphere at the start of 22 April 2013, identified by an intensification and extension to lower frequencies of the Saturn kilometric radiation, with the following sequence of effects: (1) intensification of the auroral field-aligned currents; (2) appearance of a localised, intense bulge in the dawnside (04-06 LT) aurora while the midnight sector aurora remained fainter and narrow; and (3) latitudinal broadening and poleward contraction of the nightside aurora, where the poleward motion in this sector is opposite to that expected from a model of the auroral oval's usual oscillation. These observations are interpreted as the response to tail reconnection events, initially involving Vasyliunas-type reconnection of closed mass-loaded magnetotail field lines, and then proceeding onto open lobe field lines, causing the contraction of the polar cap region on the night side.

  16. Effect of thermal fluctuations on a charged dilatonic black Saturn

    Energy Technology Data Exchange (ETDEWEB)

    Pourhassan, Behnam, E-mail: b.pourhassan@du.ac.ir [School of Physics, Damghan University, Damghan (Iran, Islamic Republic of); Faizal, Mir, E-mail: f2mir@uwaterloo.ca [Department of Physics and Astronomy, University of Lethbridge, Lethbridge, AB T1K 3M4 (Canada)

    2016-04-10

    In this paper, we will analyze the effect of thermal fluctuations on the thermodynamics of a charged dilatonic black Saturn. These thermal fluctuations will correct the thermodynamics of the charged dilatonic black Saturn. We will analyze the corrections to the thermodynamics of this system by first relating the fluctuations in the entropy to the fluctuations in the energy. Then, we will use the relation between entropy and a conformal field theory to analyze the fluctuations in the entropy. We will demonstrate that similar physical results are obtained from both these approaches. We will also study the effect of thermal fluctuations on the phase transition in this charged dilatonic black Saturn.

  17. Effect of thermal fluctuations on a charged dilatonic black Saturn

    Directory of Open Access Journals (Sweden)

    Behnam Pourhassan

    2016-04-01

    Full Text Available In this paper, we will analyze the effect of thermal fluctuations on the thermodynamics of a charged dilatonic black Saturn. These thermal fluctuations will correct the thermodynamics of the charged dilatonic black Saturn. We will analyze the corrections to the thermodynamics of this system by first relating the fluctuations in the entropy to the fluctuations in the energy. Then, we will use the relation between entropy and a conformal field theory to analyze the fluctuations in the entropy. We will demonstrate that similar physical results are obtained from both these approaches. We will also study the effect of thermal fluctuations on the phase transition in this charged dilatonic black Saturn.

  18. The Saturn System Through the Eyes of Cassini

    Science.gov (United States)

    Green, James

    2017-01-01

    More than 400 years ago, Galileo Galilei trained his homemade telescope on the night sky and observed that Saturn had two objects closely related to the planet extending on either side. At the time, in 1610, Galileo declared them to be moons. A few decades later, Saturn moon science accelerated at a dizzying pace. Christiaan Huygens first observed Saturn's largest moon Titan in 1655 and was the first to describe the extended moon-like features at Saturn as a disk of material sounding the planet. From 1671 to 1674, Giovanni Cassini discovered the moons lapetus, Rhea, Dione and Tethys. In 1675, Cassini discovered the gap in Saturn's rings that we now know as the Cassini Division. In the space age, before the Cassini-Huygens mission, we had only hints of the discoveries awaiting us at Saturn. Pioneer 11 and Voyagers 1 and 2 conducted flybys decades ago. But these quick encounters didn't allow time for more extensive research. NASA and the European Space Agency created a partnership to orbit a Saturn orbiter (Cassini) and a lander (Huygens) on Titan. Like its namesakes, the Cassini-Huygens mission not only discovered previously unknown moons, but it also helped us understand the science behind their formation, their interactions with the rings, and how truly diverse they are. The Cassini-Huygens mission revolutionized what we know about the Saturn system. The rings of Saturn, the moons, and the planet itself offer irresistible and inexhaustible subjects for intense study, and Cassini-Huygens did not disappoint. The Saturnian system proved to be a rich ground for science exploration and discoveries, and Cassini has been nothing short of a discovery machine. At the time Cassini plunged into Saturn at the end of its mission, it had observed the planet for a little less than half of a Saturn year. But it also orbited the gas giant 293 times, forever changing our understanding of the Saturn system and yielding tremendous insight for understanding the entire Solar System.

  19. Saturn's gravitational field, internal rotation, and interior structure.

    Science.gov (United States)

    Anderson, John D; Schubert, Gerald

    2007-09-07

    Saturn's internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft's gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and 35 +/- 13 seconds. This more rapid spin implies slower equatorial wind speeds on Saturn than previously assumed, and the winds at higher latitudes flow both east and west, as on Jupiter. Our related Saturn interior model has a molecular-to-metallic hydrogen transition about halfway to the planet's center.

  20. Effect of Thermal Fluctuations on a Charged Dilatonic Black Saturn

    CERN Document Server

    Pourhassan, Behnam

    2016-01-01

    In this paper, we will analyze the effect of thermal fluctuations on the thermodynamics of a charged dilatonic black Saturn. These thermal fluctuations will correct the thermodynamics of the charged dilatonic black Saturn. We will analyze the corrections to the thermodynamics of this system by first relating the fluctuations in the entropy to the fluctuations in the energy. Then, we will use the relation between entropy and a conformal field theory to analyze the fluctuations in the entropy. We will demonstrate that similar physical results are obtained from both these approaches. We will also study the effect of thermal fluctuations on the phase transition in this charged dilatonic black Saturn.

  1. The Diogene 4 pi detector at Saturne

    Science.gov (United States)

    Alard, J. P.; Arnold, J.; Augerat, J.; Babinet, R.; Bastid, N.; Brochard, F.; Costilhes, J. P.; Crouau, M.; De Marco, N.; Drouet, M.; Dupieux, P.; Fanet, H.; Fodor, Z.; Fraysse, L.; Girard, J.; Gorodetzky, P.; Gosset, J.; Laspalles, C.; Lemaire, M. C.; L'Hote, D.; Lucas, B.; Montarou, G.; Papineau, A.; Parizet, M. J.; Schimmerling, W.

    1987-01-01

    Diogene, an electronic 4 pi detector, has been built and installed at the Saturne synchrotron in Saclay. The forward angular range (0 degree-6 degrees) is covered by 48 time-of-flight scintillator telescopes that provide charge identification. The trajectories of fragments emitted at larger angles are recorded in a cylindrical 0.4-m3 Pictorial Drift Chamber (PDC) surrounding the target. The PDC is inside a 1-T magnetic field; the axis of the PDC cylinder and the magnetic field are parallel to the beam. Good identification has been obtained for both positive and negative pi mesons and for hydrogen and helium isotopes. Multiplicities in relativistic nucleus-nucleus reactions up to 40 have been detected, limited mainly by the present electronics.

  2. Phosphine photochemistry in the atmosphere of Saturn

    Science.gov (United States)

    Kaye, J. A.; Strobell, D. F.

    1984-01-01

    The photochemistry of PH3 in the atmosphere of Saturn is studied, including the effects of coupling with the photochemistries of NH3 and hydrocarbons. The vertical concentration of PH3 is found to be extremely sensitive to the eddy diffusion coefficient (K) profile used. If K is roughly 10,000 sq cm/sec in the upper troposphere, PH3 should be depleted there with a scale height of about 3.5 km. An upper limit of 100,000 sq cm/sec is estimated for K. If the gas phase concentration of P2H4 can be neglected, production of molecular phophorus is very unlikely unless the spin-forbidden recombination reaction PH+H2+M - PH3+M occurs with an exceptionally low rate. Coupling of PH3 and hydrocarbon photochemistries is very important. Possible observable amounts of the organophosphorus molecules CH3PH2 and HCP are tentatively predicted.

  3. Saturn's Quasi-Periodic Magnetohydrodynamic Waves

    Science.gov (United States)

    Yates, J. N.; Dougherty, M. K.; Southwood, D. J.; Sulaiman, A.; Masters, A.; Cowley, S. W. H.; Provan, G.; Chen, C. H. K.; Kivelson, M.; Mitchell, D. G.; Hospodarsky, G. B.; Achilleos, N. A.; Sorba, A. M.; Coates, A. J.

    2016-12-01

    Quasi-periodic 1 hour fluctuations have been recently observed in numerous instruments on-board the Cassini spacecraft. The source of these fluctuations has remained elusive to date. Here we present a case study of such fluctuations observed using the magnetometer instrument during six days in December 2006. We find that magnetic field observations at high-latitudes have small scale ( 0.4 nT) Alfvénic fluctuations present and these fluctuations are concentrated in wave-packets similar to those observed in Kleindienst et al., 2009. The observed wave-packets recur periodically at the northern magnetic oscillation period. Furthermore, we explore the nature of these fluctuations with regards to the consistency of the 1 h period using a magnetospheric box model. Our model results suggest that the observed magnetic fluctuations are standing second harmonic Alfvén waves within Saturn's outer magnetosphere.

  4. Theory of radio occultation by Saturn's rings

    Science.gov (United States)

    Marouf, E. A.; Tyler, G. L.; Eshleman, V. R.

    1982-01-01

    The radio occultation technique, as applied to Saturn's rings, is developed as a new method for the study of the physical properties of planetary ring systems. The rings are treated as a Doppler-spread radar target composed of an ensemble of discrete scatterers. The mathematical formulation of the received signal as a random-phasor-sum process is carried out following a conventional radar theory approach, providing a convenient starting point for deriving coherent signal parameters. A classical result is rederived for the equivalent refractive index of the medium. The analysis is generalized to include ringlets of arbitrary width and it is shown that when the width is such that two adjacent rays are differentially perturbed in phase, ray bending that causes focusing of the coherent signal may result. The diffuse component is also treated in detail.

  5. Final Origin of the Saturn System

    Science.gov (United States)

    Asphaug, Erik; Reufer, A.

    2012-10-01

    Saturn’s middle-sized moons (MSMs) are of diverse geology and composition, totaling 4.4% of the system mass. The rest is Titan, with more mass per planet than Jupiter’s satellites combined. Jupiter has four large satellites with 99.998% of the system mass, and no MSMs. Models to explain the discrepancy exist (e.g. Canup 2010; Mosqueira et al. 2010; Charnoz et al. 2011) but have important challenges. We introduce a new hypothesis, in which Saturn starts with a comparable family of major satellites (Ogihara and Ida 2012). These satellites underwent a final sequence of mergers, each occurring at a certain distance from Saturn. Hydrocode simulations show that galilean satellite mergers can liberate ice-rich spiral arms, mostly from the outer layers of the smaller of the accreting pair. These arms gravitate into clumps 100-1000 km diameter that resemble Saturn’s MSMs in diverse composition and other major aspects. Accordingly, a sequence of mergers (ultimately forming Titan) could leave behind populations of MSMs at a couple of formative distances, explaining their wide distribution in semimajor axis. However, MSMs on orbits that cross that of the merged body are rapidly accumulated unless scattered by resonant interactions, or circularized by mutual collisions, or both. Scattering is likely for the first mergers that take place in the presence of other resonant major satellites. Lastly, we consider that the remarkable geophysical and dynamical vigor of Titan and the MSMs might be explained if the proposed sequence of mergers happened late, triggered by impulsive giant planet migration (Morbidelli et al. 2009). The dynamical scenario requires detailed study, and we focus on analysis of the binary collisions. By analysis of the hydrocode models, we relate the provenance of the MSMs to their geophysical aspects (Thomas et al. 2010), and consider the geophysical, thermal and dynamical implications of this hypothesis for Titan’s origin.

  6. NASA's Chandra Finds That Saturn Reflects X-rays From Sun

    Science.gov (United States)

    2005-05-01

    , which allows them to navigate. But other affects of magnetic fields, only recently studied in detail, are obvious only to those living at Earth's high latitudes, or to those observing the Earth from space. Of the three magnetic planets in our solar system that have been studied extensively, Jupiter and Earth emit two general types of X rays -- auroral emissions from polar regions and disk emissions from low latitudes. However, no research to-date - including the recent study using the Chandra Observatory - has observed unambiguous signatures of auroral X-ray emissions on Saturn. "We were surprised to find no clear evidence of auroral X-ray emissions during our observations," said Bhardwaj. "It is interesting to note that even as research solves some mysteries, it confirms there is much more we have to learn. The research appeared in the May 10, 2005 issue of Astrophysical J. Letters, and the team also included Ron Elsner of MSFC; Hunter Waite of the University of Michigan in Ann Arbor; Randy Gladstone of the Southwest Research Institute in San Antonio, Texas; Thomas Cravens of the University of Kansas in Lawrence and Peter Ford from the Massachusetts Institute of Technology in Cambridge. Bhardwaj is working at MSFC on leave from the Space Physics Laboratory of the Vikram Sarabhai Space Centre in India. The Marshall Center manages the Chandra program for NASA's Science Mission Directorate in Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

  7. Noncircular features in Saturn's rings IV: Absolute radius scale and Saturn's pole direction

    Science.gov (United States)

    French, Richard G.; McGhee-French, Colleen A.; Lonergan, Katherine; Sepersky, Talia; Jacobson, Robert A.; Nicholson, Philip D.; Hedman, Mathew M.; Marouf, Essam A.; Colwell, Joshua E.

    2017-07-01

    We present a comprehensive solution for the geometry of Saturn's ring system, based on orbital fits to an extensive set of occultation observations of 122 individual ring edges and gaps. We begin with a restricted set of very high quality Cassini VIMS, UVIS, and RSS measurements for quasi-circular features in the C and B rings and the Cassini Division, and then successively add suitably weighted additional Cassini and historical occultation measurements (from Voyager, HST and the widely-observed 28 Sgr occultation of 3 Jul 1989) for additional non-circular features, to derive an absolute radius scale applicable across the entire classical ring system. As part of our adopted solution, we determine first-order corrections to the spacecraft trajectories used to determine the geometry of individual occultation chords. We adopt a simple linear model for Saturn's precession, and our favored solution yields a precession rate on the sky n^˙P = 0.207 ± 0 .006‧‧yr-1 , equivalent to an angular rate of polar motion ΩP = 0.451 ± 0 .014‧‧yr-1 . The 3% formal uncertainty in the fitted precession rate is approaching the point where it can provide a useful constraint on models of Saturn's interior, although realistic errors are likely to be larger, given the linear approximation of the precession model and possible unmodeled systematic errors in the spacecraft ephemerides. Our results are largely consistent with independent estimates of the precession rate based on historical RPX times (Nicholson et al., 1999 AAS/Division for Planetary Sciences Meeting Abstracts #31 31, 44.01) and from theoretical expectations that account for Titan's 700-yr precession period (Vienne and Duriez 1992, Astronomy and Astrophysics 257, 331-352). The fitted precession rate based on Cassini data only is somewhat lower, which may be an indication of unmodeled shorter term contributions to Saturn's polar motion from other satellites, or perhaps the result of inconsistencies in the assumed

  8. Planetary science: The birth of Saturn's baby moons

    Science.gov (United States)

    Burns, Joseph A.

    2010-06-01

    Simulations show that Saturn's nearby moons, after forming on the outskirts of the planet's main rings, get pushed clear of them. This model reproduces the moons' orbital locations and remarkably low densities.

  9. Multi-Spacecraft Observations of Saturn Kilometric Radio Emission

    Science.gov (United States)

    MacDowall, R. J.; Hess, R. A.

    2011-01-01

    Saturn kilometric radiation (SKR) is the auroral radio emission of Saturn, which has been observed by Voyager 1 & 2, Cassini, and Ulysses. Ulysses is able to detect the intense intervals of SKR from distances up to 10 AU, because of its long antennas (72 m tip-to-tip) and sensitive radio receivers. Studies of SKR by A. Lecacheux gave the surprising result that the periodicity of SKR varied with time; it was not locked to a planetary rotation of Saturn. This result has been confirmed by Cassini radio observations. Here, we compare Ulysses and Cassini observations of SKR to constrain a mode! for the SKR emission geometry. SpecifIcally, we examine the question - are the brighter sources of 5KR fixed in Saturn longitude or local time? The results have significant consequences for our understanding of SKR and its varying periodicity

  10. Observing the polarisation pattern of Saturn using CARMA

    CERN Document Server

    Aich, Moumita; Moodley, Kavilan; Sievers, Jonathan; Hedman, Matthew M

    2015-01-01

    We observe Saturn and its ring system at wavelengths of 1.3 mm (220 GHz) using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) interferometric array. We study the intensity and polarisation structure of the planet and present the best polarisation data of Saturn at these frequencies. Observations using CARMA E-array configuration exhibited some anomalous polarisation pattern in the rings. We provide details of our analysis and discuss the possibility of self gravity wakes in Saturn's ring system resulting in this anomaly. We observe Venus in intensity and polarisation to cross-check the levels of polarisation signal detectable by CARMA. We also discuss how limitations in CARMA instrumental accuracy for observing weakly polarised sources, project this signature as an upper bound of polarisation measurements of Saturn using CARMA.

  11. Cassini Discovers a Kinematic Spiral Ring around Saturn

    National Research Council Canada - National Science Library

    S. Charnoz; C. C. Porco; E. Déau; A. Brahic; J. N. Spitale; C. Bacques; K. Baillie

    2005-01-01

    .... New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn...

  12. Ring-Ringlet Interactions in Saturn's C Ring

    Science.gov (United States)

    Rappaport, N. J.

    1997-01-01

    The overall obejective of this work is to derive a theoretical model for the formation of gaps harboring isolated ringlets in order to explain the presence of such features in Saturn's C ring and Cassini division.

  13. Cassini discovers a kinematic spiral ring around Saturn.

    Science.gov (United States)

    Charnoz, S; Porco, C C; Déau, E; Brahic, A; Spitale, J N; Bacques, G; Baillie, K

    2005-11-25

    Since the time of the Voyager flybys of Saturn in 1980-1981, Saturn's eccentric F ring has been known to be accompanied on either side by faint strands of material. New Cassini observations show that these strands, initially interpreted as concentric ring segments, are in fact connected and form a single one-arm trailing spiral winding at least three times around Saturn. The spiral rotates around Saturn with the orbital motion of its constituent particles. This structure is likely the result of differential orbital motion stretching an initial cloud of particles scattered from the dense core of the F ring. Different scenarios of formation, implying ringlet-satellite interactions, are explored. A recently discovered moon candidate, S/2004 S6, is on an orbit that crosses the F-ring core at the intersection of the spiral with the ring, which suggests a dynamical connection between S/2004 S6 and the spiral.

  14. Ballistic transport in Saturn's rings - An analytic theory

    Science.gov (United States)

    Lissauer, J. J.

    1984-01-01

    Ejecta from impacts of micrometeoroids on Saturn's ring particles will, in most cases, remain in orbit about Saturn and eventually be reaccreted by the rings, possibly at a different radial location. The resulting mass transport has been suggested as the cause of some of the features observed in Saturn's rings. Previous attempts to model this transport have used numerical simulations which have not included the effects of the angular momentum transport coincident with mass transport. An analytical model for ballistic mass transport in Saturn's rings is developed. The model includes the effects of angular momentum advection and shows that the net material movement due to angular momentum advection is comparable to that caused by direct ballistic mass transport.

  15. The shape of Saturn's Huygens ringlet viewed by Cassini ISS

    Science.gov (United States)

    Spitale, J. N.; Hahn, J. M.

    2016-11-01

    A new model for the shape of the prominent eccentric ringlet in the gap exterior to Saturn's B ring is developed based on Cassini imaging observations taken over about 8 years. Unlike previous analyses, the new model treats each edge of the ringlet separately. The Keplerian component of the model is consistent with results derived from Voyager observations, and m = 2 modes forced by the nearby Mimas 2:1 Lindblad resonance are seen. Additionally, a free m = 2 mode is seen on the outer edge of the ringlet. Significant irregular structure that cannot be described using normal-mode analysis is seen on the ringlet edges as well. Particularly on the inner edge, that structure remains coherent over multi-year intervals, moving at the local Keplerian rate. We interpret the irregular structure as the signature of embedded massive bodies. The long coherence time suggests the responsible bodies are concentrated near the edge of the ringlet. Long wake-like structures originate from two locations on the inner edge of the ringlet, revealing the locations of the two most massive embedded bodies in that region. As with the Voyager observations, the Cassini data sets showed no correlation between the width and the radius of the ringlet as would be expected for a self-gravitating configuration, except for a brief interval during late 2006, when the width-radius relation was similar to those seen in most other narrow eccentric ringlets in the Solar System.

  16. Width of Injection/Dispersion Events in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Chen, Y.; Hill, T. W.

    2008-05-01

    Longitudinally localized injection and drift dispersion of hot plasma are frequently observed by the Cassini Plasma Spectrometer (CAPS) and the Cassini Magnetospheric Imaging Instrument (MIMI) in Saturn's magnetosphere. These signatures provide direct evidence for the major convective process in the inner magnetosphere of a rapidly rotating planet, in which the radial transport of plasma is expected to comprise hot, tenuous plasma moving inward and cooler, denser plasma moving outward. Previous analyses of Cassini plasma observations are consistent with this scenario, but suggest further that the hot inflow sectors are significantly narrower than the adjacent cooler outflow sectors, a property that was not anticipated theoretically. Here we quantify this property by calculating the fraction of the available time that is occupied by injection structures in a two-year data set containing 429 such structures. This fraction is found to be small, typically ~ 3 - 7%, with no obvious dependence on SKR longitude. We will expand our data set by including the very young injection events discussed by Burch et al. [2005 GRL], which were excluded by the selection criteria in our previous study.

  17. Cassini Science Highlights: Surprises in the Saturn System

    Science.gov (United States)

    Spilker, Linda J.

    2012-10-01

    Cassini’s exploration of the Saturn system has generated a treasure trove of scientific data on Saturn, Titan, Enceladus, and other diverse icy satellites, the rings, and magnetosphere. After eight years of close study of this exceptionally complex and dynamic environment, Cassini is still unveiling new scientific discoveries that continue to amaze us. Standout recent highlights include aftereffects from Saturn’s huge storm, a possible subsurface ocean on Titan, close flybys of icy satellites, migrating ring “propellers”, and unexpected variations in Saturn kilometric radiation periodicities. Current observations show seasonal changes including the formation of a polar vortex at Titan’s south pole. To date, Cassini has observed Saturn from just after northern winter solstice through northern spring equinox and now is observing the Saturn system in the previously unobserved period leading up to northern summer solstice. In the remaining five years of the on-going Solstice Mission, Cassini will continue to study seasonally and temporally dependent processes. Given the long Saturnian year ( 30 years) the longevity of Cassini is essential for elucidating seasonal change in the Saturn system. The grand finale of the mission occurs in 2017, when a series of inclined orbits brings Cassini between the innermost D ring and the upper regions of Saturn’s atmosphere. This geometry will offer unique opportunities for new discoveries and ground-breaking science, including Saturn interior structure science from otherwise unobtainable gravity and magnetic field measurements and unprecedented determination of the ring mass, currently uncertain by an order of magnitude. This Proximal orbit phase is similar to Juno’s mission at Jupiter. Comparing Jupiter and Saturn is the first step toward the next great leap in solar system origins research. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA

  18. The Origin and Evolution of Saturn, with Exoplanet Perspective

    CERN Document Server

    Atreya, Sushil K; Guillot, Tristan; Lunine, Jonathan I; Madhusudhan, Nikku; Mousis, Olivier

    2016-01-01

    Saturn formed beyond the snow line in the primordial solar nebula that made it possible for it to accrete a large mass. Disk instability and core accretion models have been proposed for Saturn?s formation, but core accretion is favored on the basis of its volatile abundances, internal structure, hydrodynamic models, chemical characteristics of protoplanetary disk, etc. The observed frequency, properties and models of exoplanets provide additional supporting evidence for core accretion. The heavy elements with mass greater than 4He make up the core of Saturn, but are presently poorly constrained, except for carbon. The C/H ratio is super-solar, and twice that in Jupiter. The enrichment of carbon and other heavy elements in Saturn and Jupiter requires special delivery mechanisms for volatiles to these planets. In this chapter we will review our current understanding of the origin and evolution of Saturn and its atmosphere, using a multi-faceted approach that combines diverse sets of observations on volatile com...

  19. The radial distribution of water ice and chromophores across Saturn's system

    CERN Document Server

    Filacchione, G; Clark, R N; Nicholson, P D; Cruikshank, D P; Cuzzi, J N; Lunine, J I; Brown, R H; Cerroni, P; Tosi, F; Ciarniello, M; Buratti, B J; Hedman, M M; Flamini, E

    2013-01-01

    Over the last eight years, the Visual and Infrared Mapping Spectrometer (VIMS) aboard the Cassini orbiter has returned hyperspectral images in the 0.35-5.1 micron range of the icy satellites and rings of Saturn. These very different objects show significant variations in surface composition, roughness and regolith grain size as a result of their evolutionary histories, endogenic processes and interactions with exogenic particles. The distributions of surface water ice and chromophores, i.e. organic and non-icy materials, across the saturnian system, are traced using specific spectral indicators (spectral slopes and absorption band depths) obtained from rings mosaics and disk-integrated satellites observations by VIMS.

  20. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/Vims

    Science.gov (United States)

    Baines, K.H.; Momary, T.W.; Buratti, B.J.; Matson, D.L.; Nelson, R.M.; Drossart, P.; Sicardy, B.; Formisano, V.; Bellucci, G.; Coradini, A.; Griffith, C.; Brown, R.H.; Bibring, J.-P.; Langevin, Y.; Capaccioni, F.; Cerroni, P.; Clark, R.N.; Combes, M.; Cruikshank, D.P.; Jaumann, R.; McCordt, T.B.; Mennella, V.; Nicholson, P.D.; Sotin, C.

    2006-01-01

    The wide spectral coverage and extensive spatial, temporal, and phase-angle mapping capabilities of the Visual Infrared Mapping Spectrometer (VIMS) onboard the Cassini-Huygens Orbiter are producing fundamental new insights into the nature of the atmospheres of Saturn and Titan. For both bodies, VIMS maps over time and solar phase angles provide information for a multitude of atmospheric constituents and aerosol layers, providing new insights into atmospheric structure and dynamical and chemical processes. For Saturn, salient early results include evidence for phosphine depletion in relatively dark and less cloudy belts at temperate and mid-latitudes compared to the relatively bright and cloudier Equatorial Region, consistent with traditional theories of belts being regions of relative downwelling. Additional Saturn results include (1) the mapping of enhanced trace gas absorptions at the south pole, and (2) the first high phase-angle, high-spatial-resolution imagery of CH4 fluorescence. An additional fundamental new result is the first nighttime near-infrared mapping of Saturn, clearly showing discrete meteorological features relatively deep in the atmosphere beneath the planet's sunlit haze and cloud layers, thus revealing a new dynamical regime at depth where vertical dynamics is relatively more important than zonal dynamics in determining cloud morphology. Zonal wind measurements at deeper levels than previously available are achieved by tracking these features over multiple days, thereby providing measurements of zonal wind shears within Saturn's troposphere when compared to cloudtop movements measured in reflected sunlight. For Titan, initial results include (1) the first detection and mapping of thermal emission spectra of CO, CO2, and CH3D on Titan's nightside limb, (2) the mapping of CH4 fluorescence over the dayside bright limb, extending to ??? 750 km altitude, (3) wind measurements of ???0.5 ms-1, favoring prograde, from the movement of a persistent

  1. In Situ Probe Science at Saturn

    Science.gov (United States)

    Atkinson, D.H.; Lunine, J.I.; Simon-Miller, A. A.; Atreya, S. K.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L. N.; Guillot, T.; Lebreton, J.-P.; Mahaffy, P.; Mousis, O.; Orton, G. S.; Reh, K.; Spilker, L. J.; Spilker, T. R.; Webster, C.

    2014-01-01

    A fundamental goal of solar system exploration is to understand the origin of the solar sys-tem, the initial stages, conditions, and processes by which the solar system formed, how the formation pro-cess was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Several theories have been put forward to explain the process of solar system formation, and the origin and evolution of the giant planets and their atmospheres. Each theory offers quantifiable predictions of the abundances of noble gases He, Ne, Ar, Kr, and Xe, and abundances of key isotopic ratios 4He3He, DH, 15N14N, 18O16O, and 13C12C. Detection of certain dis-equilibrium species, diagnostic of deeper internal pro-cesses and dynamics of the atmosphere, would also help discriminate between competing theories. Measurements of the critical abundance profiles of these key constituents into the deeper well-mixed at-mosphere must be complemented by measurements of the profiles of atmospheric structure and dynamics at high vertical resolution and also require in situ explora-tion. The atmospheres of the giant planets can also serve as laboratories to better understand the atmospheric chem-istries, dynamics, processes, and climates on all planets including Earth, and offer a context and provide a ground truth for exoplanets and exoplanetary systems. Additionally, Giant planets have long been thought to play a critical role in the development of potentially habitable planetary systems. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Sat-urn, a small, relatively shallow Saturn probe capable of measuring abundances and isotopic ratios of key at-mospheric constituents, and atmospheric structure in-cluding pressures, temperatures, dynamics, and cloud

  2. Studies of Saturn's Main Rings at Multiple Wavelengths

    Science.gov (United States)

    Spilker, L. J.; Deau, E.; Filacchione, G.; Morishima, R.; Hedman, M. M.; Nicholson, P. D.; Colwell, J. E.; Bradley, E. T.; Showalter, M.; Pilorz, S.; Brooks, S. M.

    2015-12-01

    A wealth of information about the characteristics of Saturn's ring particles and their regolith can be obtained by modeling the changes in their brightness, color and temperature with changing viewing geometry over a wide range of wavelengths, from ultraviolet through the thermal infrared. Data from Cassini's Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly studied using data from the lit and unlit main rings at multiple geometries and solar elevations over 11 years of the Cassini mission. Using multi-wavelength data sets allow us to test different thermal models by combining the effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, particle spin rate and spin axis orientation. The CIRS temperature and ISS color variations are confined primarily to phase angle over a range of solar elevations with only small differences from changing spacecraft elevation. Color and temperature dependence with varying solar elevation angle are also observed. Brightness dependence with changing solar elevation angle and phase angle is observed with UVIS. VIMS observations show that the IR ice absorption band depths are a very weak function of phase angle, out to ~140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The temperature and color variation with phase angle may be a result of scattering within the regolith and on possibly rough surfaces of the clumps, as well as a contribution from scattering between individual particles in a many-particle-thick layer. Preliminary results from our joint studies will be presented. This research was carried out in part at

  3. The puzzling structure in Saturn's outer B ring

    Science.gov (United States)

    Nicholson, Philip D.; Hedman, Matt; Buckingham, Rikley

    2017-06-01

    As first noted in Voyager images, the outer edge of Saturn's B ring is strongly perturbed by the 2:1 inner Lindblad resonance with Mimas (Porco \\etal\\ 1984). Cassini imaging and occultation data have revealed a more complex situation, where the expected resonantly-forced m=2 perturbation with an amplitude of 33~km is accompanied by freemodes with m=1, 2, 3, 4 and 5 (Spitale & Porco 2010, Nicholson \\etal\\ 2014a). To date, however, the structure immediately interior to the ring edge has not been examined carefully. We have compared optical depth profiles of the outer 1000~km of the B ring, using a large set of stellar occultations carried out since 2005 by the Cassini VIMS instrument. A search for wavelike structure, using a code written to search for hidden density waves (Hedman \\& Nicholson 2016), reveals a significant signature at a radius of ~117,150 km with a radial wavelength of ~110 km. This appears to be a trailing spiral with m=1 and a pattern speed equal to the local apsidal precession rate, $\\dpi\\simeq5.12\\dd$. Further searches for organized large-scale structure have revealed none with m=2 (as might have been expected), but several additional regions with significant m=1 variations and pattern speeds close to the local value of $\\dpi$. At present, it is unclear if these represent propagating spirals, standing waves, or perhaps features more akin to the eccentric ringlets often seen within gaps in the C ring and Cassini Division (Nicholson \\etal\\ 2014b, French \\etal\\ 2016). Comparisons of sets of profiles from 2008/9, 2012-14 and 2016 seem to show that these structures are changing over time.

  4. Precision Pointing Reconstruction and Geometric Metadata Generation for Cassini Images

    Science.gov (United States)

    French, R. S.; Showalter, M. R.; Gordon, M. K.

    2017-06-01

    We are reconstructing accurate pointing for 400,000 images taken by Cassini at Saturn. The results will be provided to the public along with per-pixel metadata describing precise image contents such as geographical location and viewing geometry.

  5. Reflected Light Curves, Spherical and Bond Albedos of Jupiter- and Saturn-like Exoplanets

    Science.gov (United States)

    Dyudina, Ulyana A.; Zhang, Xi; Li, Liming; Kopparla, Pushkar; Ingersoll, Andrew P.; Dones, Henry C. Luke; Verbiscer, Anne J.; Yung, Yuk

    2016-10-01

    Reflected light curves observed for exoplanets indicate that a few of them host bright clouds. We estimate how the light curve and total stellar heating of a planet depends on forward and backward scattering in the clouds based on Pioneer and Cassini spacecraft images of Jupiter and Saturn. We fit analytical functions to the local reflected brightnesses of Jupiter and Saturn depending on the planet's phase. These observations cover broad bands at 0.59-0.72 and 0.39-0.5 μm, and narrow bands at 0.938 (atmospheric window), 0.889 (CH4 absorption band), and 0.24-0.28 μm. We simulate the images of the planets with a ray-tracing model, and disk-integrate them to produce the full-orbit light curves. For Jupiter, we also fit the modeled light curves to the observed full-disk brightness. We derive spherical albedos for Jupiter and Saturn, and for planets with Lambertian and Rayleigh-scattering atmospheres. Jupiter-like atmospheres can produce light curves that are a factor of two fainter at half-phase than the Lambertian planet, given the same geometric albedo at transit. The spherical albedo is typically lower than for a Lambertian planet by up to a factor of ˜1.5. The Lambertian assumption will underestimate the absorption of the stellar light and the equilibrium temperature of the planetary atmosphere. We also compare our light curves with the light curves of solid bodies: the moons Enceladus and Callisto. Their strong backscattering peak within a few degrees of opposition (secondary eclipse) can lead to an even stronger underestimate of the stellar heating. This work is published: Dyudina, U.,et al., 2016: ApJ, 822, 76, http://arxiv.org/abs/1511.04415.

  6. Saturn's Radio Emissions and their Relation to Magnetospheric Dynamics

    Science.gov (United States)

    Jackman, C. M.

    With the arrival of the Cassini spacecraft at Saturn in July 2004, there have been quasi-continuous observations of Saturn Kilometric Radiation (SKR) emissions. In this paper we review the response of these emissions to dynamics in Saturn's magnetosphere, driven by factors internal and external to the system. We begin by reviewing solar wind data upstream of Saturn and discuss the link between solar wind compressions and dynamics in Saturn's magnetosphere, evidenced by intensifications and occasional phase changes in the SKR emission. We then review the link between magnetotail reconnection and planetary radio emissions. We begin in the well-sampled magnetotail of Earth and then move to Saturn where exploration of the nightside magnetosphere has revealed evidence of plasmoid-like magnetic structures and other phenomena indicative of the kronian equivalent of terrestrial substorms. In general, there is a good correlation between the timing of reconnection events and enhancements in the SKR emission, coupled with extension of the emission to lower frequencies. We interpret this as growth of the radio source region to higher altitudes along the field lines, stimulated by increased precipitation of energetic electrons into the auroral zones following reconnection. We also comment on the observation that the majority of reconnection events occur at SKR phases where the SKR power would be expected to be rising with time, indicating that reconnection is most likely to occur at a preferred phase. We conclude with a summary of the current knowledge of the link between Saturn's magnetospheric dynamics and SKR emissions, and list a number of open questions to be addressed in the future.

  7. The Evolution of Hydrocarbons in Saturn's Northern Storm Region

    Science.gov (United States)

    Bjoraker, Gordon; Hesman, B. E.; Achterberg, R. K.; Romani, P. N.

    2012-01-01

    The massive storm at 40N on Saturn that began in December 2010 has produced significant and lasting effects in the northern hemisphere on temperature and species abundances (Fletcher et aL 2011). The northern storm region was observed on several occasions between March 2011 and April 2012 by Cassini's Composite Infrared Spectrometer (CIRS) at a spectral resolution (0.5/cm) which permits the study of trace species in Saturn's stratosphere. During this time period, stratospheric temperatures in regions referred to as "beacons" (warm regions at specific longitudes at the latitude of the storm) became significantly warmer than pre-storm values of 140K, peaking near 220K, and subsequently cooling. These warm temperatures led to greatly enhanced infrared emission due to C4H2, C3H4, C2H2, and C2H6 in the stratosphere as well as the first detection of C2H4 on Saturn in the thermal infrared (Hesman et al. 2012). Using CH4 as a thermometer of Saturn's stratosphere in the beacon regions, we can derive the mixing ratios of each of these molecules. The most common hydrocarbons (C2H2 and C2H6) serve as dynamical tracers on Saturn and their abundances may constrain vertical motion in the stratosphere. All of these hydrocarbons are products of methane photolysis. Since many of the photochemical reactions that produce heavier hydrocarbons such as C4H2 and C3H4 are temperature sensitive, the beacon region provides a natural laboratory for studying these reactions on Saturn. We will discuss the time evolution of the abundances of each of these hydrocarbons from their pre-storm values, through the period of maximum heating , and during the period of cooling that is taking place in Saturn's stratosphere.

  8. The magnetic fields of Jupiter and Saturn

    Science.gov (United States)

    Ness, N. F.

    1981-01-01

    The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

  9. Prometheus Induced Vorticity In Saturns F Ring

    CERN Document Server

    Sutton, Phil J

    2016-01-01

    Saturns rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of grea...

  10. Rotational modulation of Saturn's auroral radio emissions

    Science.gov (United States)

    Lamy, L.

    2011-10-01

    Among the persistent questions raised by the existence of a rotational modulation of the Saturn Kilometric Radiation (SKR), the origin of the variability of the 10.8 hours SKR period at a 1% level over weeks to years remains intriguing. While its short-term fluctuations (20-30 days) have been related to the variations of the solar wind speed, its long-term fluctuations (months to years) were proposed to be triggered by Enceladus mass-loading and/or seasonal variations. This situation has become even more complicated since the recent identification of two separated periods at 10.8h and 10.6h, each varying with time, corresponding to SKR sources located in the southern (S) and the northern (N) hemispheres, respectively. Here, six years of Cassini continuous radio measurements have been used to derive long-term radio periods and phase systems separately for each hemisphere 1. The S phase has then been used to investigate the S SKR rotational modulation (see Figure 1), shown to be consistent with an intrinsically rotating phenomenon, in contrast with the early Voyager picture, but in agreement with the diurnal modulation observed in other kronian auroral phenomena.

  11. [Biochemical principles of early saturnism recognition].

    Science.gov (United States)

    Tsimakuridze, M P; Mansuradze, E A; Zurashvili, D G; Tsimakuridze, M P

    2009-03-01

    The aim of the work is to determine the major sensitive criteria of biochemical indicators that allow timely discovery of negative influence of lead on organism and assist in early diagnosis of primary stages of saturnism. The workers of Georgian typographies, performing technological processes of letterpress printing were observed. Professional groups having contact with lead aerosols (main group of 66 people) and the workers of the same typography not being in touch with the poison (control group of 24 people) were studied. It was distinguished that, protracted professional contact with lead causes moderate increase of lead, coproporphyrin and DALA in daily urine in most cases; it is more clearly evidenced in the professional groups of lead smelters and lino operators and less clearly among typesetter and printers. Upon the checkup of people, having a direct contact with lead, biochemical analysis of urine should be given a preference, especially the determination of quantitative content of lead and coproporphyrin in urine with the aim of revealing the lead carrier, which is one of the first signals for occupational lookout and medical monitoring of the similar contingent.

  12. Dust Sources of Saturn's E Ring

    Science.gov (United States)

    Spahn, F.; Schmidt, J.; Albers, N.; Kempf, S.; Krivov, A. V.; Sremcevic, M.

    The recent detection of a dust plume at Enceladus' south pole sheds new light on the origin of the E ring of Saturn. The particles probably condense from gas vents escaping from a system of cracks covering the south pole that appears unusually hot in the Cassini infrared experiments. The main fraction of the E ring dust is created in these gas vents. Still, significant amounts of dust should originate from grains ejected by hypervelocity impacts of E ring particles (ERPs), or alternatively, of interplanetary dust grains (IDPs) on the Saturnian moons embedded in the E ring. We estimate the contributions of impactor -ejecta created dust at these various satellites in the ring, relative to the production rate of grains in the plume at Enceladus. Furthermore, we compare the amount of dust created by both projectile families - ERPs and IDPs - and predict that one can clearly discriminate between the ejecta raised by either projectile families in the data of the Cassini dust detector (CDA) collected at close flybys with the moons embedded in the E ring.

  13. Modeling the disequilibrium species for Jupiter and Saturn: Implications for Juno and Saturn entry probe

    CERN Document Server

    Wang, Dong; Mousis, Olivier

    2016-01-01

    Disequilibrium species have been used previously to probe the deep water abundances and the eddy diffusion coefficient for giant planets. In this paper, we present a diffusion-kinetics code that predicts the abundances of disequilibrium species in the tropospheres of Jupiter and Saturn with updated thermodynamic and kinetic data. The dependence on the deep water abundance and the eddy diffusion coefficient is investigated. We quantified the disagreements in CO kinetics that comes from using different reaction networks and identified C$_2$H$_6$ as a useful tracer for the eddy diffusion coefficient. We first apply a H/P/O reaction network to Jupiter and Saturn's atmospheres and suggest a new PH$_3$ destruction pathway. New chemical pathways for SiH$_4$ and GeH$_4$ destruction are also suggested, and another AsH$_3$ destruction pathway is investigated thanks to new thermodynamic and kinetic data. These new models should enhance the interpretation of the measurement of disequilibrium species by JIRAM on board Jun...

  14. Observations of Saturn Kilometric Radiation during the Saturn Auroral Campaign of Spring 2013

    Science.gov (United States)

    Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Lamy, L.; Mitchell, D. G.; Dougherty, M. K.; Nichols, J.; Pryor, W.; Baines, K. H.; Dyudina, U.; Stallard, T.; O'Donoghue, J.; Melin, H.; Crary, F. J.; Miller, S.

    2013-09-01

    During April and May 2013, a concerted effort to study Saturn's auroras was mounted using multi-wavelength observations from Cassini and a number of Earth-based observations. It has been shown that the integrated power of Saturn Kilometric Radiation (SKR) provides a good proxy for auroral activity and there is at least a qualitative correlation between auroral brightness and SKR intensity. While the SKR observations can be complicated by beaming issues, they provide a reasonable, continuous context within which to place other observations. For example, during the first Hubble Space Telescope visit on 5 April 2013, a brightened poleward expansion of the UV aurora was observed while the SKR intensity was elevated during most of the day as shown in Figure 1. In the following, more extended interval of the campaign over 19 - 23 April 2013, the SKR intensity is low for the first few days but intensifies later in the interval, reflecting increasing UV auroral activity as seen by Hubble. In this paper we will present the SKR intensities over time intervals of the auroral campaign along with other Cassini and Earth-based observations for selected events.

  15. The formation of Saturn's satellites and rings, as influenced by Saturn's contraction history

    Science.gov (United States)

    Pollack, J. B.; Grossman, A. S.; Moore, R.; Graboske, H. C., Jr.

    1976-01-01

    The paper investigates constraints imposed on the ice content of Saturn's satellites and rings by the planet's high luminosity during the early part of its quasi-equilibrium contraction phase. It is assumed that the addition of ices to the satellites was not completed until after the start of the quasi-equilibrium contraction and that the condensation of ices ceased at the same time within the primordial nebulae of Jupiter and Saturn. Using previously derived limits on the time of condensation cessation for Jupiter's system, the following tentative conclusions are made: (1) Titan is the innermost satellite at whose position a methane-containing ice could condense; (2) water ice could have condensed at the positions of all the satellites; (3) the systematic decrease in the mass of the regular satellites with decreasing distance from the planet may have been caused, in part, by the larger time intervals, for the closer satellites, between the start of contraction and the first condensation of ices at their positions; and (4) ammonia ices, primarily NH4SH, were able to condense at the positions of all but the innermost satellites. It is also shown that water ice could have condensed in the region of the rings near the end of the condensation period.

  16. Cassini ISS observation of Saturn's north polar vortex and comparison to the south polar vortex

    Science.gov (United States)

    Sayanagi, Kunio M.; Blalock, John J.; Dyudina, Ulyana A.; Ewald, Shawn P.; Ingersoll, Andrew P.

    2017-03-01

    We present analyses of Saturn's north pole using high-resolution images captured in late 2012 by the Cassini spacecraft's Imaging Science Subsystem (ISS) camera. The images reveal the presence of an intense cyclonic vortex centered at the north pole. In the red and green visible continuum wavelengths, the north polar region exhibits a cyclonically spiraling cloud morphology extending from the pole to 85°N planetocentric latitude, with a 4700 km radius. Images captured in the methane bands, which sense upper tropospheric haze, show an approximately circular hole in the haze extending up to 1.5° latitude away from the pole. The spiraling morphology and the "eye"-like hole at the center are reminiscent of a terrestrial tropical cyclone. In the System III reference frame (rotation period of 10h39m22.4s, Seidelmann et al. 2007; Archinal et al. 2011), the eastward wind speed increases to about 140 m s-1 at 89°N planetocentric latitude. The vorticity is (6.5± 1.5) × 10-4 s-1 at the pole, and decreases to (1.3± 1.2) × 10-4 s-1 at 89°N. In addition, we present an analysis of Saturn's south polar vortex using images captured in January 2007 to compare its cloud morphology to the north pole. The set of images captured in 2007 includes filters that have not been analyzed before. Images captured in the violet filter (400 nm) also reveal a bright polar cloud. The south polar morphology in 2007 was more smooth and lacked the small clouds apparent around the north pole in 2012. Saturn underwent equinox in August 2009. The 2007 observation captured the pre-equinox south pole, and the 2012 observation captured the post-equinox north pole. Thus, the observed differences between the poles are likely due to seasonal effects. If these differences indeed are caused by seasonal effects, continuing observations of the summer north pole by the Cassini mission should show a formation of a polar cloud that appears bright in short-wavelength filters.

  17. Three 2012 Transits of Venus: From Earth, Jupiter, and Saturn

    Science.gov (United States)

    Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Edelman, E.; Reardon, K.; Widemann, T.; Tanga, P.; Dantowitz, R.; Silverstone, M. D.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Willson, R. C.; Kopp, G. A.; Yurchyshyn, V. B.; Sterling, A. C.; Scherrer, P. H.; Schou, J.; Golub, L.; McCauley, P.; Reeves, K.

    2013-01-01

    We observed the 2012 June 6/5 transit seen from Earth (E/ToV), simultaneously with Venus Express and several other spacecraft not only to study the Cytherean atmosphere but also to provide an exoplanet-transit analog. From Haleakala, the whole transit was visible in coronal skies; among our instruments was one of the world-wide Venus Twilight Experiment's nine coronagraphs. Venus's atmosphere became visible before first contact. SacPeak/IBIS provided high-resolution images at Hα/carbon-dioxide. Big Bear's NST also provided high-resolution observations of the Cytherean atmosphere and black-drop evolution. Our liaison with UH's Mees Solar Observatory scientists provided magneto-optical imaging at calcium and potassium. Solar Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope (SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance measurements with ACRIMSAT and SORCE/TIM, were used to observe the event as an exoplanet-transit analog. On September 20, we imaged Jupiter for 14 Hubble Space Telescope orbits, centered on a 10-hour ToV visible from Jupiter (J/ToV), as an exoplanet-transit analog in our own solar system, using Jupiter as an integrating sphere. Imaging was good, although much work remains to determine if we can detect the expected 0.01% solar irradiance decrease at Jupiter and the even slighter differential effect between our violet and near-infrared filters caused by Venus's atmosphere. We also give a first report on our currently planned December 21 Cassini UVIS observations of a transit of Venus from Saturn (S/ToV). Our E/ToV expedition was sponsored by the Committee for Research and Exploration/National Geographic Society; supplemented: NASA/AAS's Small Research Grant Program. We thank Rob Ratkowski, Stan Truitt, Rob Lucas, Aram Friedman, and Eric Pilger '82 at Haleakala, and Joseph Gangestad '06 at Big Bear for assistance, and Lockheed Martin Solar and Astrophysics Lab and Hinode science and operations teams for support

  18. The Atmospheric Dynamics of Jupiter, Saturn, and Titan

    Science.gov (United States)

    Flasar, F. M.

    2009-01-01

    Comparative studies of Jupiter and Saturn often emphasize their similarities, but recent observations have highlighted important differences. The stratospheres of both planets exhibit an equatorial oscillation reminiscent of that in Earth's middle atmosphere. Jupiter's oscillation has a 4-5 year period, not linked to its season, and it has been modeled as an analog to the terrestrial quasi-biennial oscillation, driven by the stresses associated with vertically propagating waves. Saturn's equatorial oscillation is nearly semiannual, but wave activity may still be a driver. Jupiter's internal rotation rate is inferred from its steady modulated radio emission. Saturn's internal rotation is more enigmatic. It has been inferred from the modulation of the body's kilometric radio emission, but this period has varied by 1% over the last 25 years. Saturn's equatorial winds are also puzzling, as those inferred from cloud tracking by Cassini and more recent HST observations are weaker than those from Voyager. Whether this is attributable to a difference in altitudes of the tracked clouds in winds with vertical shear or a real temporal change in the winds is not known. Both winter and summer poles of Saturn exhibit very compact circumpolar vortices with warm cores, indicating subsidence. Titan's middle atmosphere is characterized by global cyclostrophic winds, particularly the strong circumpolar vortex in the winter hemisphere. In many ways, the spatial distribution of temperature, gaseous constituents, and condensates is reminiscent of conditions in terrestrial winter vortices, albeit with different chemistry. The meridional contrast in Titan's tropospheric temperatures is small, only a few kelvins.

  19. Cassini RPWS Observation of Saturn's Radio Rotation Rates After Equinox

    Science.gov (United States)

    Ye, S.; Fischer, G.; Kurth, W. S.; Gurnett, D. A.

    2015-12-01

    Saturn's radio rotation rate, originally thought to be constant, was found to vary with time by comparing the Voyager and Ulysses observation of Saturn kilometric radiation (SKR). Later on, Cassini RPWS observation of SKR revealed that the two hemispheres of Saturn are rotating at two different rotational periods, and it was proposed that the two periods are subject to seasonal change. The topic we would like to focus on resolving is whether the north and south rotational periods actually crossed after equinox. The almost continuous observation of SKR, Saturn narrowband emission, and auroral hiss by RPWS provide a good method of tracking the radio rotation periods of the planet. SKR power from the northern and southern hemispheres can be separated by the polarization of the radiation. Based on the evolution of SKR phase in the northern and southern hemispheres, we show that the rotation rate of the northern SKR is slower than that of the southern SKR starting from late 2014. Auroral hiss provides another unambiguous method of isolating the rotation signals from one hemisphere because the whistler mode plasma wave cannot cross the equator. Rotational modulation rates of auroral hiss are shown to agree with those of SKR during Cassini's high inclination orbits. Hemispherical origins of the narrowband emission are not distinguishable due to its unique generation mechanism. However, Lomb-Scargle periodogram of the 5 kHz narrowband emissions indicates that the two separate radio rotation periods of Saturn's magnetosphere reappeared after a long break since equinox.

  20. Revealing Saturn's Rotation Period from its Gravitational Field

    Science.gov (United States)

    Helled, Ravit; Galanti, Eli; Kaspi, Yohai

    2015-04-01

    Knowledge of the rotation period of a giant planet is fundamental for constraining its internal structure and atmosphere dynamics. Until the arrival of the Cassini spacecraft to Saturn, Saturn's rotation period was set to the Voyager 2 radio period, 10h 39m 22.4s that was derived from the periodicity in Saturn's kilometric radiation (SKR). Surprisingly, Cassini's SKR measured a rotation period of 10h 47m 6s using the exact same method. It was then realized that Saturn's rotation period is unknown to within a few minutes. We show that Saturn's rotation period can be determined from its measured gravitational field. We find that without imposing any constraints on the planetary shape and internal density profile the rotation rate can be determined to within several minutes, and is 10h 43m 10s ± 4m. If we include limits based on the observed shape and possible internal density profiles, the rotation period is found to be 10h 32m 45s ± 46s. The success of our method is confirmed by applying it for Jupiter and reproducing exactly its measured rotation period that is well constrained.

  1. Dual periodicities in the rotational modulation of Saturn narrowband emissions

    Science.gov (United States)

    Ye, S.-Y.; Gurnett, D. A.; Groene, J. B.; Wang, Z.; Kurth, W. S.

    2010-12-01

    Using the Cassini Radio and Plasma Wave Science (RPWS) instrument it has recently been shown that the rotational modulation period of Saturn kilometric radiation (SKR) has two components, one with a period of 10.6 h and the other with a period of 10.8 h. The longer period is primarily observed in the southern hemisphere and the shorter period is primarily observed in the northern hemisphere. In this paper, the modulation period of 5 kHz Saturn narrowband radio emissions is examined, restricting the spacecraft location to either the northern or the southern hemisphere of Saturn. It is found that in both hemispheres, the modulation period of 5 kHz narrowband emissions has two components that are equal to the SKR periods. It is known that Saturn narrowband emissions are first generated in the auroral regions as Z-mode and then mode convert to escaping L-O modes at density gradients. These Z-mode waves are trapped in a region close to the planet and can propagate from one hemisphere to another before they mode convert to L-O modes, thereby leading to dual periods of Saturn narrowband emissions in each hemisphere. The phase shift between the SKR and narrowband emissions is around 90° in the longitude, which means that SKR leads narrowband emissions by 2-3 h.

  2. Modelling Saturn's atmospheric circulations and cloud structure with OPUS

    Science.gov (United States)

    Zuchowski, L. C.; Read, P. L.; Yamazaki, Y. H.

    2009-04-01

    We are investigating Saturn's atmospheric circulations and cloud structure in the Northern and Southern hemisphere as initial value problems by use of the Oxford Planetary Unified model System (OPUS), a sophisticated GCM based on the UK Met Office Unified Model. Solving an extended form of the Hydrodynamic Primitive Equations, OPUS is capable of including 40 vertical levels from 0.1 bar to 100 bar. The model was initiated with temperature and balanced thermal wind profiles recently obtained by Cassini's Composite InfraRed Spectrometer (CIRS). A simple cloud scheme for the Jovian planets has been added to OPUS and is employed to model the three major cloud decks (ammonia, ammonium-hydrosulfide and water) on Saturn and the advection of these clouds with the atmosphere. We have already conducted several numerical studies with OPUS, simulating jet scale meridional circulations, the formation of cloud bands and discrete turbulent features on Jupiter. By modelling the dynamics and clouds of Saturn in a similar way, we are hoping to gain further insight into the formation of circulation cells over the zonal jet streams as well as to examine the distribution of atmospheric condensates in response to these motions. The model will also be used to numerically investigate the characteristic features in Saturn's Northern hemisphere. It is envisioned to directly compare the atmospheric configurations obtained for Saturn with previous results from the Jupiter model.

  3. Saturn's aurora in the January 2004 events

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2006-07-01

    Full Text Available Differences in the solar wind interaction with the magnetosphere of Saturn relative to the Earth result from the decrease in the solar wind plasma density and magnetic field strength with distance from the Sun, and from the change in the average angle of the IMF at Saturn's orbit. Other reasons are related to Saturn's rapid rotation and internal magnetospheric plasma sources. Moreover, the IMF structure observed by Cassini in 2003–2004 during the approach to Saturn is consistent with corotating interaction regions (CIRs existing during the declining phase of the solar cycle. Two cases on 16 and 26 January 2004 are considered when disturbances in the solar wind passed Cassini and then Saturn. After the solar wind shock encountered the kronian magnetosphere, the auroral oval became brighter (especially at dawn with a reduced radius. In these cases the auroral power was anti-correlated with the radius of the oval. Possible mechanisms responsible for such unexpected behavior are presented and discussed in detail.

  4. Exploration of the Saturn System by the Cassini Mission: Observations with the Cassini Infrared Spectrometer

    Science.gov (United States)

    Abbas, Mian M.

    2014-01-01

    Outline: Introduction to the Cassini mission, and Cassini mission Objectives; Cassini spacecraft, instruments, launch, and orbit insertion; Saturn, Rings, and Satellite, Titan; Composite Infrared Spectrometer (CIRS); and Infrared observations of Saturn and titan.

  5. How Janus' orbital swap affects the edge of Saturn's A ring?

    Science.gov (United States)

    El Moutamid, Maryame; Nicholson, Philip D.; French, Richard G.; Tiscareno, Matthew S.; Murray, Carl D.; Evans, Michael W.; French, Colleen McGhee; Hedman, Matthew M.; Burns, Joseph A.

    2016-11-01

    We present a study of the behavior of Saturn's A ring outer edge, using images and occultation data obtained by the Cassini spacecraft over a period of 8 years from 2006 to 2014. More than 5000 images and 170 occultations of the A ring outer edge are analyzed. Our fits confirm the expected response to the Janus 7:6 Inner Lindblad resonance (ILR) between 2006 and 2010, when Janus was on the inner leg of its regular orbit swap with Epimetheus. During this period, the edge exhibits a regular 7-lobed pattern with an amplitude of 12.8 km and one minimum aligned with the orbital longitude of Janus, as has been found by previous investigators. However, between 2010 and 2014, the Janus/Epimetheus orbit swap moves the Janus 7:6 LR away from the A ring outer edge, and the 7-lobed pattern disappears. In addition to several smaller-amplitudes modes, indeed, we found a variety of pattern speeds with different azimuthal wave numbers, and many of them may arise from resonant cavities between the ILR and the ring edge; also we found some other signatures consistent with tesseral resonances that could be associated with inhomogeneities in Saturn's gravity field. Moreover, these signatures do not have a fixed pattern speed. We present an analysis of these data and suggest a possible dynamical model for the behavior of the A ring's outer edge after 2010.

  6. Dynamical variability in Saturn Equatorial Atmosphere

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.; Hueso, R.; Rojas, J. F.; French, R. G.; Grupo Ciencias Planetarias Team

    2003-05-01

    Historical ground-based and recent HST observations show that Saturn's Equatorial Atmosphere is the region where the most intense large-scale dynamical variability took place at cloud level in the planet. Large-scale convective storms (nicknamed the ``Great White Spots") occurred in 1876, 1933 and 1990. The best studied case (the 1990 storm), produced a dramatic change in the cloud aspect in the years following the outburst of September 1990. Subsequently, a new large storm formed in 1994 and from 1996 to 2002 our HST observations showed periods of unusual cloud activity in the southern part of the Equator. This contrast with the aspect observed during the Voyager 1 and 2 encounters in 1980 and 1981 when the Equator was calm, except for some mid-scale plume-like features seen in 1981. Cloud-tracking of the features have revealed a dramatic slow down in the equatorial winds from maximum velocities of ˜ 475 m/s in 1980-1981 to ˜ 275 m/s during 1996-2002, as we have recently reported in Nature, Vol. 423, 623 (2003). We discuss the possibility that seasonal and ring-shadowing effects are involved in generating this activity and variability. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. SPH acknowledges a PhD fellowship from the Spanish MECD and RH a post-doc fellowship from Gobierno Vasco. RGF was supported in part by NASA's Planetary Geology and Geophysics Program NAG5-10197 and STSCI Grant GO-08660.01A.

  7. Hydrocarbons on Saturn's satellites Iapetus and Phoebe

    Science.gov (United States)

    Cruikshank, D.P.; Wegryn, E.; Dalle, Ore C.M.; Brown, R.H.; Bibring, J.-P.; Buratti, B.J.; Clark, R.N.; McCord, T.B.; Nicholson, P.D.; Pendleton, Y.J.; Owen, T.C.; Filacchione, G.; Coradini, A.; Cerroni, P.; Capaccioni, F.; Jaumann, R.; Nelson, R.M.; Baines, K.H.; Sotin, C.; Bellucci, G.; Combes, M.; Langevin, Y.; Sicardy, B.; Matson, D.L.; Formisano, V.; Drossart, P.; Mennella, V.

    2008-01-01

    Material of low geometric albedo (pV ??? 0.1) is found on many objects in the outer Solar System, but its distribution in the saturnian satellite system is of special interest because of its juxtaposition with high-albedo ice. In the absence of clear, diagnostic spectral features, the composition of this low-albedo (or "dark") material is generally inferred to be carbon-rich, but the form(s) of the carbon is unknown. Near-infrared spectra of the low-albedo hemisphere of Saturn's satellite Iapetus were obtained with the Visible-Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft at the fly-by of that satellite of 31 December 2004, yielding a maximum spatial resolution on the satellite's surface of ???65 km. The spectral region 3-3.6 ??m reveals a broad absorption band, centered at 3.29 ??m, and concentrated in a region comprising about 15% of the low-albedo surface area. This is identified as the C{single bond}H stretching mode vibration in polycyclic aromatic hydrocarbon (PAH) molecules. Two weaker bands attributed to {single bond}CH2{single bond} stretching modes in aliphatic hydrocarbons are found in association with the aromatic band. The bands most likely arise from aromatic and aliphatic units in complex macromolecular carbonaceous material with a kerogen- or coal-like structure, similar to that in carbonaceous meteorites. VIMS spectra of Phoebe, encountered by Cassini on 11 June 2004, also show the aromatic hydrocarbon band, although somewhat weaker than on Iapetus. The origin of the PAH molecular material on these two satellites is unknown, but PAHs are found in carbonaceous meteorites, cometary dust particles, circumstellar dust, and interstellar dust. ?? 2007 Elsevier Inc. All rights reserved.

  8. Prometheus Induced Vorticity in Saturn's F Ring

    Science.gov (United States)

    Sutton, Phil J.; Kusmartsev, Feo V.

    2016-11-01

    Saturn's rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non-zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of great interest to planet and planetesimals in proto-planetary disks where vortices and turbulence are suspected of having a significant role in their formation and migrations. Additionally, it is found that the immediate channel edges created by the close passage of Prometheus actually show high radial dispersions in the order 20-50 cm/s, up to a maximum of 1 m/s. This is much greater than the value required by Toomre for a disk to be unstable to the growth of axisymmetric oscillations. However, an area a few hundred km away from the edge shows a more promising location for the growth of coherent objects.

  9. Prometheus Induced Vorticity in Saturn's F Ring

    Science.gov (United States)

    Sutton, Phil J.; Kusmartsev, Feo V.

    2016-09-01

    Saturn's rings are known to show remarkable real time variability in their structure. Many of which can be associated to interactions with nearby moons and moonlets. Possibly the most interesting and dynamic place in the rings, probably in the whole Solar System, is the F ring. A highly disrupted ring with large asymmetries both radially and azimuthally. Numerically non-zero components to the curl of the velocity vector field (vorticity) in the perturbed area of the F ring post encounter are witnessed, significantly above the background vorticity. Within the perturbed area rich distributions of local rotations is seen located in and around the channel edges. The gravitational scattering of ring particles during the encounter causes a significant elevated curl of the vector field above the background F ring vorticity for the first 1-3 orbital periods post encounter. After 3 orbital periods vorticity reverts quite quickly to near background levels. This new found dynamical vortex life of the ring will be of great interest to planet and planetesimals in proto-planetary disks where vortices and turbulence are suspected of having a significant role in their formation and migrations. Additionally, it is found that the immediate channel edges created by the close passage of Prometheus actually show high radial dispersions in the order ~20-50 cm/s, up to a maximum of 1 m/s. This is much greater than the value required by Toomre for a disk to be unstable to the growth of axisymmetric oscillations. However, an area a few hundred km away from the edge shows a more promising location for the growth of coherent objects.

  10. Tilting Saturn without tilting Jupiter: Constraints on giant planet migration

    CERN Document Server

    Brasser, R

    2015-01-01

    The migration and encounter histories of the giant planets in our Solar System can be constrained by the obliquities of Jupiter and Saturn. We have performed secular simulations with imposed migration and N-body simulations with planetesimals to study the expected obliquity distribution of migrating planets with initial conditions resembling those of the smooth migration model, the resonant Nice model and two models with five giant planets initially in resonance (one compact and one loose configuration). For smooth migration, the secular spin-orbit resonance mechanism can tilt Saturn's spin axis to the current obliquity if the product of the migration time scale and the orbital inclinations is sufficiently large (exceeding 30 Myr deg). For the resonant Nice model with imposed migration, it is difficult to reproduce today's obliquity values, because the compactness of the initial system raises the frequency that tilts Saturn above the spin precession frequency of Jupiter, causing a Jupiter spin-orbit resonance...

  11. Quasi-Periodic Whistler Mode Emissions in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Hospodarsky, George; Leisner, Jared; Cinar, Gokcin; Kurth, William; Gurnett, Donald; Santolik, Ondrej

    2016-04-01

    The Cassini Radio and Plasma Wave Science (RPWS) instrument often detects at Saturn a series of quasi-periodic (QP) whistler mode emissions that rise in frequency and repeat every few to about ten minutes. These QP emissions are detected about 5% of the time when Cassini is within ~5.5 Rs of Saturn and are primarily observed near the magnetic equator. They are usually detected in the frequency range of about 1 to 3 kHz, and appear to be related to electrons with energies of a few keV. Their spectral characteristics are very similar to the quasi-periodic whistler mode emissions detected in Earth's magnetosphere. However, it is unclear if the same type of source generation can explain the Earth and Saturn QP emissions.

  12. Cassini/CAPS Observations of Tail Dynamics at Saturn

    Science.gov (United States)

    Thomsen, M. F.; Tokar, R. L.; Wilson, R. J.; Jackman, C. M.

    2013-12-01

    Following up a recent study of the density and flow direction of plasmas in Saturn's premidnight tail, we apply the same methodology to examine Cassini's near- and post-midnight tail passes as well. Specifically, we focus on intervals when CAPS was able to view both inward and outward plasma flows, and we examine the spatial distribution and other properties of such flows. We compare our results with those found by McAndrews et al. [Plasma in Saturn's nightside magnetosphere and the implications for global circulation, Plan. Sp. Sci. (2009)], using a different approach to the analysis of Cassini/CAPS data. These observations provide important clues to Saturn's tail structure and dynamics.

  13. Post-equinox periodicities in Saturn's energetic electrons

    Science.gov (United States)

    Carbary, J. F.; Mitchell, D. G.; Krimigis, S. M.; Krupp, N.

    2011-12-01

    Since Saturn's vernal equinox in August 2009 (day 223), energetic electrons (110-365 keV) have exhibited a variety of periodic and aperiodic behavior within a spectral window of 5-15 hours. From late 2009 through the end of 2010, when the observed at dusk, a single period near 10.7 hours dominated the Lomb spectra of these particles. Near the end of 2010, however, the energetic electrons displayed multiple periods, with the strongest at 10.65 hours. The periodicity observed after equinox has a mean value of 10.69 ± 0.06 hours and agreed closely with that of Saturn kilometric radio (south) emissions. By early 2011, when the observer had moved to the dayside, the periodicities abruptly disappeared and the Lomb spectra show no periodicity. This behavior may suggest changes in Saturn's ionosphere as a result of seasonal change, or may alternately imply a local time dependence of periodicity caused by magnetodisk thickness asymmetry.

  14. Exploration of the magnetodisk of Saturn around equinox

    Science.gov (United States)

    Szego, K.; Nemeth, Z.; Bebesi, Z.; Foldy, L.; Erdos, G.; Thomsen, M.; Delapp, D.

    2012-04-01

    In 2009 eleven consecutive orbits of the Cassini spacecraft (from Rev 108 to Rev 119, with the exception of Rev 118) were constructed in such a way, that each of them intersected the equatorial plane of Saturn at about 22:00 LT, and approached the equator at decreasing inclination. Along all of these orbits Cassini flew by Titan, starting with T52 (2009-094T01:47:48 on 4 April), and finishing with T62 (2009-285T08:36:25 on 12 October). The equinox of Saturn was in August 2009, therefore this set of orbits is of particular interest for studying the nightside plasmadisk of Saturn. One of the most striking features of the Kronian magnetosphere is that it displays rotational modulation effects and the periodicity of these effects is determined by the Saturn Kilometric Radiation (SKR) - a radio emission originating from the planet. This (variable) periodicity modulates the plasma environment of the Kronian satellites, and strongly influences the moon-magnetosphere interactions, but its properties and origin are not completely understood yet. The SKR periodicity was observed in magnetic field, as well as in particle data, even in the outer magnetosphere. In this contribution we analyze plasma features observed along Rev 108 - Rev 119, and we compare the periodicity of the features with a simple structural model (SSM) describing the flapping motion of Saturn's plasma sheet [Arridge et al. 2011]. We also investigate deviations from the simple model. Arridge, C. S., et al. (2011), Periodic motion of Saturn's nightside plasma sheet, J. Geophys. Res., 116, A11205, doi:10.1029/2011JA016827

  15. Saturn's Aurora Observed by Cassini Camera in Visible Wavelengths

    Science.gov (United States)

    Dyudina, U.; Ingersoll, A. P.; Ewald, S.; Wellington, D. F.

    2014-12-01

    Cassini camera's movies in 2009-2013 show Saturn's aurora in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000-1500 km above the cloud tops. The spectrum observed in 9 lters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras [1]. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spiral around the pole, and sometimes double arcs at 70-75 both north and south latitude. 10,000-km-scale longitudinal brightness structures can persist for more than 100 hours. This structures rotate together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. 1000-km-scale disturbances may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of the longitudinal structure of the aurora in two long observations in 2009 and 2012 allowed us to estimate its period of rotation of 10.65±0.15 h for 2009 and 10.8±0.1 h for 2012. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time. The 2012 south aurora period is longer than the SKR periods detected at the time. These periods are also close to the rotation period of the lightning storms on Saturn. We discuss those periodicities and their relevance to Saturn's internal rotation. [1] Aguilar, A. et al. The Electron-Excited Mid-Ultraviolet to Near-Infrared Spectrum of H2:Cross Sections and Transition Probabilities. Astrophys. J. Supp. Ser. 177, 388-407 (2008).

  16. Global Deep Convection Models of Saturn's Atmospheric Features

    Science.gov (United States)

    Heimpel, Moritz; Cuff, Keith; Gastine, Thomas; Wicht, Johannes

    2016-04-01

    The Cassini mission, along with previous missions and ground-based observations, has revealed a rich variety of atmospheric phenomena and time variability on Saturn. Some examples of dynamical features are: zonal flows with multiple jet streams, turbulent tilted shear flows that seem to power the jets, the north polar hexagon, the south polar cyclone, large anticyclones in "storm alley", numerous convective storms (white spots) of various sizes, and the 2010/2011 great storm, which destroyed an array of vortices dubbed the "string of pearls". Here we use the anelastic dynamo code MagIC, in non-magnetic mode, to study rotating convection in a spherical shell. The thickness of the shell is set to approximate the depth of the low electrical conductivity deep atmosphere of Saturn, and the convective forcing is set to yield zonal flows of similar velocity (Rossby number) to those of Saturn. Internal heating and the outer entropy boundary conditions allow simple modelling of atmospheric layers with neutral stability or stable stratification. In these simulations we can identify several saturnian and jovian atmospheric features, with some variations. We find that large anticyclonic vortices tend to form in the first anticyclonic shear zones away from the equatorial jet. Cyclones form at the poles, and polar polygonal jet streams, comparable to Saturn's hexagon, may or may not form, depending on the model conditions. Strings of small scale vortical structures arise as convective plumes near boundaries of shear zones. They typically precede larger scale convective storms that spawn propagating shear flow disturbances and anticyclonic vortices, which tend to drift across anticyclonic shear zones, toward the equator (opposite the drift direction of Saturn's 2010/2011 storm). Our model results indicate that many identifiable dynamical atmospheric features seen on Jupiter and Saturn arise from deep convection, shaped by planetary rotation, underlying and interacting with stably

  17. Radial growth of an extended spoke in Saturn's B ring

    Science.gov (United States)

    Eplee, R. E., Jr.; Smith, B. A.

    1985-01-01

    An analysis is reported of the pattern of radial growth of an extended spoke observed in the Voyager 2 low-resolution Saturn ring 'movie'. The feature is atypical in that it orbits Saturn at the corotational rate for 1-1/2 hours after the onset of its formation and then undergoes a 40-min acceleration to sustained Keplerian velocities. A correlation between the dynamical phases and the radial growth modes of the spoke is observed, one that seems consistent with the plasma cloud model of spoke formation and evolution proposed by Goertz and Morfill (1983), taken in the limit of high charge density.

  18. Study of Saturn electrostatic discharges with high time resolution

    Science.gov (United States)

    Zakharenko, V.; Mylostna, K.; Konovalenko, A.; Kolyadin, V.; Zarka, P.; Griessmeier, J.-M.; Litvinenko, G.; Sidorchuk, M.; Rucker, H.; Fischer, G.; Cecconi, B.; Coffre, A.; Denis, L.; Shevchenko, V.; Nikolaenko, V.

    2013-09-01

    Ground-based observations of SED (Saturn Electrostatic Discharges) with high time resolution are the next stage of extraterrestrial atmospheric processes study. Due to extremely high intensity of Saturn's storm J (2010) [1] we have obtained the records with high signal-to-noise (S/N) ratio with the time resolution of 15 ns. It permitted us to investigate the microsecond structure of lightning and clearly distinguish SED in the presence of local interference in virtue of a dispersive delay of extraterrestrial planetary signals.

  19. Analyses d'Observations infrarouges et Modélisation photochimique de l'Atmosphère de Saturne

    Science.gov (United States)

    Ollivier, Jean-Luc

    2000-09-01

    L'objet de cette thèse est l'étude de l'atmosphère de Saturne. Deux aspects principaux sont abordés: la composition atmosphérique et la structure thermique. L'atmosphère de Saturne, comme celle des autres planètes géantes, est essentiellement composée d'hydrogène moléculaire et d'hélium. Des composés minoritaires, tels que le méthane, l'ammoniac ou l'eau, dont l'abondance a été déterminée par différentes observations, sont aussi présents. La première partie de cette thèse s'attache à étudier les processus de formation des composés atmosphériques carbones et oxygènes. Pour cela, un modèle photochimique de la stratosphère de Saturne a été développé. Ce code permet de reproduire les différents phénomènes physico-chimiques gouvernant la composition atmosphérique et ainsi, de calculer l'abondance des différentes espèces chimiques présentes dans l'atmosphère. Différents thèmes sont abordés, en particulier les processus de formation et de perte du radical méthyl, les phénomènes de transport verticaux, et les flux externes de matière oxygénée. Enfin, une comparaison des modèles photochimiques de Saturne et Neptune est réalisée. La deuxième partie de cette thèse porte sur la réalisation et l'analyse de différentes observations infrarouges de Saturne. Des images de Saturne dans la fenêtre atmosphérique à 10 microns, à des longueurs d'onde sensibles au continuum thermique et à l'éthane ou l'acétylène, ont été obtenues en décembre 1992. Nous présentons ces images et leur analyse. Un modèle de transfert radiatif est utilisé afin de comparer un flux théorique avec le flux observé. Nous avons mis en évidence l'évolution saisonnière de la structure thermique de l'atmosphère de Saturne. Enfin, nous présentons de nouvelles images de Saturne réalisées en juillet 1999. On-line Thesis, Jean-Luc Ollivier

  20. Saturn's north polar cyclone and hexagon at depth revealed by Cassini/VIMS

    Science.gov (United States)

    Baines, K.H.; Momary, T.W.; Fletcher, L.N.; Showman, A.P.; Roos-Serote, M.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

    2009-01-01

    A high-speed cyclonic vortex centered on the north pole of Saturn has been revealed by the visual-infrared mapping spectrometer (VIMS) onboard the Cassini-Huygens Orbiter, thus showing that the tropospheres of both poles of Saturn are occupied by cyclonic vortices with winds exceeding 135 m/s. High-spatial-resolution (~200 km per pixel) images acquired predominantly under night-time conditions during Saturn's polar winter-using a thermal wavelength of 5.1 ??m to obtain time-lapsed imagery of discrete, deep-seated (>2.1-bar) cloud features viewed in silhouette against Saturn's internally generated thermal glow-show a classic cyclonic structure, with prograde winds exceeding 135 m/s at its maximum near 88.3?? (planetocentric) latitude, and decreasing to <30 m/s at 89.7?? near the vortex center and<20 m/s at 80.5??. High-speed winds, exceeding 125 m/s, were also measured for cloud features at depth near 76?? (planetocentric) latitude within the polar hexagon consistent with the idea that the hexagon itself, which remains nearly stationary, is a westward (retrograde) propagating Rossby wave - as proposed by Allison (1990, Science 247, 1061-1063) - with a maximum wave speed near 2-bars pressure of ~125 m/s. Winds are ~25 m/s stronger than observed by Voyager, suggesting temporal variability. Images acquired of one side of the hexagon in dawn conditions as the polar winter wanes shows the hexagon is still visible in reflected sunlight nearly 28 years since its discovery, that a similar 3-lane structure is observed in reflected and thermal light, and that the cloudtops may be typically lower in the hexagon than in nearby discrete cloud features outside of it. Clouds are well-correlated in visible and 5.1 ??m images, indicating little windshear above the ~2-bar level. The polar cyclone is similar in size and shape to its counterpart at the south pole; a primary difference is the presence of a small (<600 km in diameter) nearly pole-centered cloud, perhaps indicative of

  1. On the long-term variability of Jupiter and Saturn zonal winds

    Science.gov (United States)

    Sanchez-Lavega, A.; Garcia-Melendo, E.; Hueso, R.; Barrado-Izagirre, N.; Legarreta, J.; Rojas, J. F.

    2012-12-01

    We present an analysis of the long-term variability of Jupiter and Saturn zonal wind profiles at their upper cloud level as retrieved from cloud motion tracking on images obtained at ground-based observatories and with different spacecraft missions since 1979, encompassing about three Jovian and one Saturn years. We study the sensitivity and variability of the zonal wind profile in both planets to major planetary-scale disturbances and to seasonal forcing. We finally discuss the implications that these results have for current model efforts to explain the global tropospheric circulation in these planets. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support, Grupos Gobierno Vasco IT-464-07 and UPV/EHU UFI11/55. [1] Sánchez-Lavega A., et al., Icarus, 147, 405-420 (2000). [2] García-Melendo E., Sánchez LavegaA., Icarus, 152, 316-330 (2001) [3] Sánchez-Lavega A., et al., Nature, 423, 623-625 (2003). [4] García-Melendo E., et al., Geophysical Research Letters, 37, L22204 (2010).

  2. Bimodality and the formation of Saturn's ring particles

    Energy Technology Data Exchange (ETDEWEB)

    Gehrels, T.

    1980-11-01

    The F ring appears to have an outer and an inner rim, with only the latter observed by the imaging photopolarimeter (IPP) on the Pioneer Saturn spacecraft. The inside of the G ring, near 2.49 R/sub S/, may also be seen in the optical data. 1979S1 is red as well as dark. The light scattered through the B ring is noticeably red. The A ring has a dense outer rim. The Cassini Division and the French Division (Dollfus Division) have a dark gap near their centers. The C ring becomes weaker toward the center such that outer, middle, and inner C rings can be recognized. The Pioneer and earth-based observations are explained with a model for the B and A rings to some extent of a bimodal size distributions of particles; the larger ones may be original accretions, while small debris diffuses inward through the Cassini Division and the C ring. During the formation of the ring system, differential gravitation allowed only silicaceous grains of higher density (rho> or approx. =3 g cm/sup -3/) to coagulate. These serve as interstitial cores for snowy carbonaceous grains, between the times of accretion from interplanetary cometary grains and liberation by collision followed by diffusion inward to Saturn and final evaporation.

  3. First Results of ISO-SWS Grating Observations of Saturn

    NARCIS (Netherlands)

    de Graauw, Th.; Encrenaz, Th.; Schaeidt, S.; Lellouch, E.; Feuchtgruber, H.; Beintema, D. A.; Bezard, B.; Drossart, P.; Griffin, M.; Heras, A.; Kessler, M.; Leech, K.; Morris, A.; Roelfsema, P. R.; Roos-Serote, M.; Salama, A.; Vandenbussche, B.; Valentijn, E. A.; Davies, G. R.; Naylor, D. A.

    1996-01-01

    The spectrum of Saturn has been recorded between 2.3 and 15 mu m, on June 13, 1996, with the grating mode of the Short-Wavelength Spectrometer of ISO (Infrared Space Observatory). The resolving power is about 1500 and the sensitivity is better than 1 Jy. As compared to Jupiter, the spectrum of

  4. Saturn: A large area X-ray simulation accelerator

    Science.gov (United States)

    Bloomquist, D. D.; Stinnett, R. W.; McDaniel, D. H.; Lee, J. R.; Sharpe, A. W.; Halbleib, J. A.; Schlitt, L. G.; Spence, P. W.; Corcoran, P.

    1987-06-01

    Saturn is the result of a major metamorphosis of the Particle Beam Fusion Accelerator-I (PBFA-I) from an ICF research facility to the large-area X-ray source of the Simulation Technology Laboratory (STL) project. Renamed Saturn, for its unique multiple-ring diode design, the facility is designed to take advantage of the numerous advances in pulsed power technology. Saturn will include significant upgrades in the energy storage and pulse-forming sections. The 36 magnetically insulated transmission lines (MITLs) that provided power flow to the ion diode of PBFA-I were replaced by a system of vertical triplate water transmission lines. These lines are connected to three horizontal triplate disks in a water convolute section. Power will flow through an insulator stack into radial MITLs that drive the three-ring diode. Saturn is designed to operate with a maximum of 750 kJ coupled to the three-ring e-beam diode with a peak power of 25 TW to provide an X-ray exposure capability of 5 x 10 rads/s (Si) and 5 cal/g (Au) over 500 cm.

  5. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  6. New constraints on Saturn's interior from Cassini astrometric data

    CERN Document Server

    Lainey, Valéry; Tajeddine, Radwan; Cooper, Nicholas J; Murray, Carl; Robert, Vincent; Tobie, Gabriel; Guillot, Tristan; Mathis, Stéphane; Remus, Françoise; Desmars, Josselin; Arlot, Jean-Eudes; De Cuyper, Jean-Pierre; Dehant, Véronique; Pascu, Dan; Thuillot, William; Poncin-Lafitte, Christophe Le; Zahn, Jean-Paul

    2015-01-01

    Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital moons. We have used the latter to make the first determination of Saturn's Love number, $k_2=0.390 \\pm 0.024$, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which $k_2$ ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a reduction of up to 80% in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio $k_2/Q=(1.59 \\pm 0.74) \\times 10^{-4}$ and implying fast orbital expansions of the moons. This high dissipation, with no obvious variati...

  7. Modulation of Saturn's radio clock by solar wind speed.

    Science.gov (United States)

    Zarka, Philippe; Lamy, Laurent; Cecconi, Baptiste; Prangé, Renée; Rucker, Helmut O

    2007-11-08

    The internal rotation rates of the giant planets can be estimated by cloud motions, but such an approach is not very precise because absolute wind speeds are not known a priori and depend on latitude: periodicities in the radio emissions, thought to be tied to the internal planetary magnetic field, are used instead. Saturn, despite an apparently axisymmetric magnetic field, emits kilometre-wavelength (radio) photons from auroral sources. This emission is modulated at a period initially identified as 10 h 39 min 24 +/- 7 s, and this has been adopted as Saturn's rotation period. Subsequent observations, however, revealed that this period varies by +/-6 min on a timescale of several months to years. Here we report that the kilometric radiation period varies systematically by +/-1% with a characteristic timescale of 20-30 days. Here we show that these fluctuations are correlated with solar wind speed at Saturn, meaning that Saturn's radio clock is controlled, at least in part, by conditions external to the planet's magnetosphere. No correlation is found with the solar wind density, dynamic pressure or magnetic field; the solar wind speed therefore has a special function. We also show that the long-term fluctuations are simply an average of the short-term ones, and therefore the long-term variations are probably also driven by changes in the solar wind.

  8. Saturn's fast spin determined from its gravitational field and oblateness

    CERN Document Server

    Helled, Ravit; Kaspi, Yohai

    2015-01-01

    The alignment of Saturn's magnetic pole with its rotation axis precludes the use of magnetic field measurements to determine its rotation period. The period was previously determined from radio measurements by the Voyager spacecraft to be 10h 39m 22.4s. When the Cassini spacecraft measured a period of 10h 47m 6s, which was additionally found to change between sequential measurements, it became clear that the radio period could not be used to determine the bulk planetary rotation period. Estimates based upon Saturn's measured wind fields have increased the uncertainty even more, giving numbers smaller than the Voyager rotation period, and at present Saturn's rotation period is thought to be between 10h 32m and 10h 47m, which is unsatisfactory for such a fundamental property. Here we report a period of 10h 32m 45s +- 46s, based upon an optimization approach using Saturn's measured gravitational field and limits on the observed shape and possible internal density profiles. Moreover, even when solely using the co...

  9. Cassini at Saturn Proximal Orbits - Attitude Control Challenges

    Science.gov (United States)

    Burk, Thomas A.

    2013-01-01

    The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

  10. In Situ Cassini Spacecraft Observations of Turbulence in Saturn's Magnetosheath

    Science.gov (United States)

    Hadid, L.; Sahraoui, F.; Retino, A.; Modolo, R.; Canu, P.; Jackman, C.; Masters, A.; Dougherty, M. K.; Gurnett, D. A.

    2013-09-01

    Throughout this work we investigate, the properties of turbulence in the Magnetosheath of Saturn. To do so, we computed Power Spectral Densities (PSD) based on Cassini interplanetary magnetic field data between 2004 and 2007. As a preliminary result, we show the absence of the Kolmogorov scale ~ f-5/3 in the inertial range whereas only the f-1 scale is present.

  11. Saturn V Stage I (S-IC) Overview

    Science.gov (United States)

    Interbartolo, Michael

    2009-01-01

    Objectives include: a) Become familiar with the Saturn V Stage I (S-IC) major structural components: Forward Skirt, Oxidizer Tank, Intertank, Fuel Tank, and Thrust Structure. b) Gain a general understanding of the Stage I subsystems: Fuel, Oxidizer, Instrumentation, Flight Control, Environmental Control, Electrical, Control Pressure, and Ordinance.

  12. Equatorial winds on Saturn and the stratospheric oscillation

    Science.gov (United States)

    Li, Liming; Jiang, Xun; Ingersoll, Andrew P.; Del Genio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Nixon, Conor A.; Achterberg, Richard K.; Orton, Glenn S.; Fletcher, Leigh N.; Baines, Kevin H.

    2011-11-01

    The zonal jets on the giant planets have been thought to be stable in time. A decline in the velocity of Saturn's equatorial jet has been identified, on the basis of a comparison of cloud-tracking data across two decades, but the differences in cloud speeds have since been suggested to stem from changes in cloud altitude in combination with vertical wind shear, rather than from temporal changes in wind strength at a given height. Here, we combine observations of cloud tracks and of atmospheric temperatures taken by two instruments on the Cassini spacecraft to reveal a significant temporal variation in the strength of the high-altitude equatorial jet on Saturn. Specifically, we find that wind speeds at atmospheric pressure levels of 60mbar, corresponding to Saturn's tropopause, increased by about 20ms-1 between 2004 and 2008, whereas the wind speed has been essentially constant over time in the southern equatorial troposphere. The observations further reveal that the equatorial jet intensified by about 60ms-1 between 2005 and 2008 in the stratosphere, that is, at pressure levels of 1-5mbar. Because the wind acceleration is weaker near the tropopause than higher up, in the stratosphere, we conclude that the semi-annual equatorial oscillation of Saturn's middle atmosphere is also damped as it propagates downwards.

  13. Did Saturn's rings form during the Late Heavy Bombardment ?

    CERN Document Server

    Charnoz, Sebastien; Dones, Luke H; Salmon, Julien

    2008-01-01

    The origin of Saturn\\' s massive ring system is still unknown. Two popular scenarios - the tidal splitting of passing comets and the collisional destruction of a satellite - rely on a high cometary flux in the past. In the present paper we attempt to quantify the cometary flux during the Late Heavy Bombardment (LHB) to assess the likelihood of both scenarios. Our analysis relies on the so-called Nice model of the origin of the LHB (Tsiganis et al., 2005; Morbidelli et al., 2005; Gomes et al., 2005) and on the size distribution of the primordial trans-Neptunian planetesimals constrained in Charnoz & Morbidelli (2007). We find that the cometary flux on Saturn during the LHB was so high that both scenarios for the formation of Saturn rings are viable in principle. However, a more detailed study shows that the comet tidal disruption scenario implies that all four giant planets should have comparable ring systems whereas the destroyed satellite scenario would work only for Saturn, and perhaps Jupiter. This is ...

  14. First Results of ISO-SWS Grating Observations of Saturn

    NARCIS (Netherlands)

    de Graauw, Th.; Encrenaz, Th.; Schaeidt, S.; Lellouch, E.; Feuchtgruber, H.; Beintema, D. A.; Bezard, B.; Drossart, P.; Griffin, M.; Heras, A.; Kessler, M.; Leech, K.; Morris, A.; Roelfsema, P. R.; Roos-Serote, M.; Salama, A.; Vandenbussche, B.; Valentijn, E. A.; Davies, G. R.; Naylor, D. A.

    1996-01-01

    The spectrum of Saturn has been recorded between 2.3 and 15 mu m, on June 13, 1996, with the grating mode of the Short-Wavelength Spectrometer of ISO (Infrared Space Observatory). The resolving power is about 1500 and the sensitivity is better than 1 Jy. As compared to Jupiter, the spectrum of Satur

  15. 10 years of surprises at Saturn: CAPS and INMS highlights

    Science.gov (United States)

    Coates, A. J.; Waite, J. H.

    2014-04-01

    The Cassini mission at Saturn has provided many surprises on Saturn's rapidly rotating magnetosphere and its interaction with the diverse moons, as well as its interaction with the solar wind. One of the early discoveries was the water-rich composition of the magnetosphere. Its structure and dynamics indicate remarkable injections, periodicities and interchange events. Enceladus, orbiting at 4 RS, was found to have plumes of water vapour and ice which are the dominant source for the inner magnetosphere. Charged water clusters, charged dust and photoelectrons provide key populations in the 'dusty plasma' seen here, as well as chemical complexity in the plume material. Direct pickup is seen near Enceladus and field aligned currents create a spot in Saturn's aurora. At Titan, orbiting at 20 RS, heavy negative and positive ions are seen in the ionosphere, as well as neutrals, all of which have surprising chemical complexity. These provide the source for Titan's haze. Ionospheric plasma is seen in Titan's tail, enabling ion escape to be estimated at 7 tonnes per day. Saturn's ring ionosphere was seen early in the mission, which was oxygen rich and produced photoelectrons; a return will be made in 2017. At Rhea, pickup positive and negative ions indicated weak atmospheres sustained by energetic particle impact, seen in the neutrals also. A weak atmosphere was also seen at Dione. The exosphere production process operates at Jupiter's moons also. Here we review some of the key new results, and discuss the implications for other solar system contexts.

  16. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes.

    Science.gov (United States)

    Felici, M; Arridge, C S; Coates, A J; Badman, S V; Dougherty, M K; Jackman, C M; Kurth, W S; Melin, H; Mitchell, D G; Reisenfeld, D B; Sergis, N

    2016-01-01

    Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 10(9) and (1.43 ± 0.21) × 10(10) cm(-2) s(-1), 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×10(2) and 1.1 ×10(3) kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how

  17. Cassini observations of ionospheric plasma in Saturn's magnetotail lobes

    Science.gov (United States)

    Felici, M.; Arridge, C. S.; Coates, A. J.; Badman, S. V.; Dougherty, M. K.; Jackman, C. M.; Kurth, W. S.; Melin, H.; Mitchell, D. G.; Reisenfeld, D. B.; Sergis, N.

    2016-01-01

    Studies of Saturn's magnetosphere with the Cassini mission have established the importance of Enceladus as the dominant mass source for Saturn's magnetosphere. It is well known that the ionosphere is an important mass source at Earth during periods of intense geomagnetic activity, but lesser attention has been dedicated to study the ionospheric mass source at Saturn. In this paper we describe a case study of data from Saturn's magnetotail, when Cassini was located at ≃ 2200 h Saturn local time at 36 RS from Saturn. During several entries into the magnetotail lobe, tailward flowing cold electrons and a cold ion beam were observed directly adjacent to the plasma sheet and extending deeper into the lobe. The electrons and ions appear to be dispersed, dropping to lower energies with time. The composition of both the plasma sheet and lobe ions show very low fluxes (sometimes zero within measurement error) of water group ions. The magnetic field has a swept-forward configuration which is atypical for this region, and the total magnetic field strength is larger than expected at this distance from the planet. Ultraviolet auroral observations show a dawn brightening, and upstream heliospheric models suggest that the magnetosphere is being compressed by a region of high solar wind ram pressure. We interpret this event as the observation of ionospheric outflow in Saturn's magnetotail. We estimate a number flux between (2.95 ± 0.43) × 109 and (1.43 ± 0.21) × 1010 cm-2 s-1, 1 or about 2 orders of magnitude larger than suggested by steady state MHD models, with a mass source between 1.4 ×102 and 1.1 ×103 kg/s. After considering several configurations for the active atmospheric regions, we consider as most probable the main auroral oval, with associated mass source between 49.7 ±13.4 and 239.8 ±64.8 kg/s for an average auroral oval, and 10 ±4 and 49 ±23 kg/s for the specific auroral oval morphology found during this event. It is not clear how much of this mass is

  18. Galactic Cosmic Rays in the inner magnetosphere of Saturn

    Science.gov (United States)

    Kotova, Anna; Roussos, Elias; Krupp, Norbert; Dandouras, Iannis

    2015-04-01

    Existence of the Saturn innermost radiation belt in the tiny gap between planetary atmosphere and D-ring was first proposed in 2004 after the discovery of the significant fluxes of the energetic neutral atoms (ENA) coming from this area, what was measured by Ion and Neutron Camera on board of Cassini during the insertion orbit (1). One of the main sources of energetic charged particles for such inner radiation belt is the interaction of the Galactic Cosmic Rays (GCR) with the Saturn's atmosphere and rings, which due to CRAND process can produce the keV-MeV ions or electrons in the region. Using charged particles tracer developed in our group, we simulate the motion of the GCR using the backward tracing method and analyze the differences, arising from the usage of different magnetospheric models. The simulation was performed under assumptions of the dipole magnetic field model, then using more complex model with a magnetic equator offset and some other non-dipolar effects and later on using the Khurana model (2), which is based on the Cassini observations and for today is the most realistic model of the Saturn magnetosphere. We created maps of the GCR access to the Saturn atmosphere, analyzed changes of the minimum energy needed for GCR to reach the planet from different directions depending on the latitude and longitude and explained difference with analytically derived by Stormer theory values. Using those simulations and combine its results with Saturn atmospheric model and rings composition model, we estimate the production of secondaries resulting from the interaction of the GCR with atmosphere and from its penetration of the rings. This allows us to estimate the flux of energetic particles close to the planet, what will be useful for the preparation of the final "proximal" orbits of the Cassini spacecraft in 2017. For the validation of the results they are compared with the data from the Cassini insertion orbit. References: (1) S. M. Krimigis et al., "Dynamics

  19. New constraints on Saturn's interior from Cassini astrometric data

    Science.gov (United States)

    Lainey, Valéry; Jacobson, Robert A.; Tajeddine, Radwan; Cooper, Nicholas J.; Murray, Carl; Robert, Vincent; Tobie, Gabriel; Guillot, Tristan; Mathis, Stéphane; Remus, Françoise; Desmars, Josselin; Arlot, Jean-Eudes; De Cuyper, Jean-Pierre; Dehant, Véronique; Pascu, Dan; Thuillot, William; Le Poncin-Lafitte, Christophe; Zahn, Jean-Paul

    2017-01-01

    Using astrometric observations spanning more than a century and including a large set of Cassini data, we determine Saturn's tidal parameters through their current effects on the orbits of the eight main and four coorbital Moons. We have used the latter to make the first determination of Saturn's Love number from observations, k2=0.390 ± 0.024, a value larger than the commonly used theoretical value of 0.341 (Gavrilov & Zharkov, 1977), but compatible with more recent models (Helled & Guillot, 2013) for which the static k2 ranges from 0.355 to 0.382. Depending on the assumed spin for Saturn's interior, the new constraint can lead to a significant reduction in the number of potential models, offering great opportunities to probe the planet's interior. In addition, significant tidal dissipation within Saturn is confirmed (Lainey et al., 2012) corresponding to a high present-day tidal ratio k2/Q=(1.59 ± 0.74) × 10-4 and implying fast orbital expansions of the Moons. This high dissipation, with no obvious variations for tidal frequencies corresponding to those of Enceladus and Dione, may be explained by viscous friction in a solid core, implying a core viscosity typically ranging between 1014 and 1016 Pa.s (Remus et al., 2012). However, a dissipation increase by one order of magnitude at Rhea's frequency could suggest the existence of an additional, frequency-dependent, dissipation process, possibly from turbulent friction acting on tidal waves in the fluid envelope of Saturn (Ogilvie & Lin, 2004; Fuller et al. 2016).

  20. Birotor dipole for Saturn's inner magnetic field from Cassini observations

    Science.gov (United States)

    Galopeau, Patrick

    2017-04-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR). These two periods were attributed to the northern and southern hemispheres respectively. We suppose that the periodic time modulations present in the SKR are mainly due to the rotation of Saturn's inner magnetic field. The existence of a double period implies that the inner field is not only limited to a simple rotation dipole but displays more complex structures having the same time periodicities than the radio emission. In order to build a model of this complex magnetic field, it is absolutely necessary to know the accurate phases of rotation linked with the two periods. The radio observations from the RPWS experiment allow a continuous and accurate follow-up of these rotation phases, since the SKR emission is permanently observable and produced very close to the planetary surface. A continuous wavelet transform analysis of the intensity of the SKR signal received at 290 kHz between July 2004 and June 2012 was performed in order to calculate in the same time the different periodicities and phases. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to have North and South poles rotating around Saturn's axis at two different angular velocities; this dipole is tilted and not centered. 57 Cassini's revolutions, the periapsis of which is less than 5 Saturnian radii, have been selected for this study. For each of these chosen orbits, it is possible to fit with high precision the measurements of the MAG data experiment given by the magnetometers embarked on board Cassini. A nonrotating external magnetic field completes the model. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. These results can be used as a boundary condition for

  1. HERA: an atmospheric probe to unveil the depths of Saturn

    Science.gov (United States)

    Mousis, Olivier; Atkinson, David H.; Amato, Michael; Aslam, Shahid; Atreya, Sushil K.; Blanc, Michel; Bolton, Scott J.; Brugger, Bastien; Calcutt, Simon; Cavalié, Thibault; Charnoz, Sébastien; Coustenis, Athena; DELEUIL, Magali; Ferri, Francesca; Fletcher, Leigh N.; Guillot, Tristan; Hartogh, Paul; Holland, Andrew; Hueso, Ricardo; Keller, Christoph; Kessler, Ernst; Lebreton, Jean-Pierre; leese, Mark; Lellouch, Emmanuel; Levacher, Patrick; Marty, Bernard; Morse, Andrew; Nixon, Conor; Reh, Kim R.; Renard, Jean-Baptiste; Sanchez-Lavega, Agustin; Schmider, François-Xavier; Sheridan, Simon; Simon, Amy A.; Snik, Frans; Spilker, Thomas R.; Stam, Daphne M.; Venkatapathy, Ethiraj; Vernazza, Pierre; Waite, J. Hunter; Wurz, Peter

    2016-10-01

    The Hera Saturn entry probe mission is proposed as an M-class mission led by ESA with a significant collaboration with NASA. It consists of a Saturn atmospheric probe and a Carrier-Relay spacecraft. Hera will perform in situ measurements of the chemical and isotopic compositions as well as the dynamics of Saturn's atmosphere, with the goal of improving our understanding of the origin, formation, and evolution of Saturn, the giant planets and their satellite systems, with extrapolation to extrasolar planets.The primary science objectives will be addressed by an atmospheric entry probe that would descend under parachute and carry out in situ measurements beginning in the stratosphere to help characterize the location and properties of the tropopause, and continue into the troposphere to pressures of at least 10 bars. All of the science objectives, except for the abundance of oxygen, which may be only addressed indirectly via observations of species whose abundances are tied to the abundance of water, can be achieved by reaching 10 bars. As in previous highly successful collaborative efforts between ESA and NASA, the proposed mission has a baseline concept based on a NASA-provided carrier/data relay spacecraft that would deliver the ESA-provided atmospheric probe to the desired atmospheric entry point at Saturn. ESA's proposed contribution should fit well into the M5 Cosmic Vision ESA call cost envelope.A nominal mission configuration would consist of a probe that detaches from the carrier one to several months prior to probe entry. Subsequent to probe release, the carrier trajectory would be deflected to optimize the over-flight phasing of the probe descent location for both probe data relay as well as performing carrier approach and flyby science, and would allow multiple retransmissions of the probe data for redundancy. The Saturn atmospheric entry probe would in many respects resemble the Jupiter Galileo probe. It is anticipated that the probe architecture for

  2. METER-SIZED MOONLET POPULATION IN SATURN'S C RING AND CASSINI DIVISION

    Energy Technology Data Exchange (ETDEWEB)

    Baillie, Kevin; Colwell, Joshua E. [Department of Physics, University of Central Florida, Orlando, FL 32816-2385 (United States); Esposito, Larry W. [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, 392 UCB, Boulder, CO 80309-0392 (United States); Lewis, Mark C., E-mail: kevin.baillie@cea.fr [Department of Computer Science, Trinity University, One Trinity Place, San Antonio, TX 78212-7200 (United States)

    2013-06-01

    Stellar occultations observed by the Cassini Ultraviolet Imaging Spectrograph reveal the presence of transparent holes a few meters to a few tens of meters in radial extent in otherwise optically thick regions of the C ring and the Cassini Division. We attribute the holes to gravitational disturbances generated by a population of {approx}10 m boulders in the rings that is intermediate in size between the background ring particle size distribution and the previously observed {approx}100 m propeller moonlets in the A ring. The size distribution of these boulders is described by a shallower power-law than the one that describes the ring particle size distribution. The number and size distribution of these boulders could be explained by limited accretion processes deep within Saturn's Roche zone.

  3. Observations of ejecta clouds produced by impacts onto Saturn's rings.

    Science.gov (United States)

    Tiscareno, Matthew S; Mitchell, Colin J; Murray, Carl D; Di Nino, Daiana; Hedman, Matthew M; Schmidt, Jürgen; Burns, Joseph A; Cuzzi, Jeffrey N; Porco, Carolyn C; Beurle, Kevin; Evans, Michael W

    2013-04-26

    We report observations of dusty clouds in Saturn's rings, which we interpret as resulting from impacts onto the rings that occurred between 1 and 50 hours before the clouds were observed. The largest of these clouds was observed twice; its brightness and cant angle evolved in a manner consistent with this hypothesis. Several arguments suggest that these clouds cannot be due to the primary impact of one solid meteoroid onto the rings, but rather are due to the impact of a compact stream of Saturn-orbiting material derived from previous breakup of a meteoroid. The responsible interplanetary meteoroids were initially between 1 centimeter and several meters in size, and their influx rate is consistent with the sparse prior knowledge of smaller meteoroids in the outer solar system.

  4. Thermal structure and dynamics of Saturn's northern springtime disturbance

    Science.gov (United States)

    Fletcher, L.N.; Hesman, B.E.; Irwin, P.G.J.; Baines, K.H.; Momary, T.W.; Sanchez-Lavega, A.; Flasar, F.M.; Read, P.L.; Orton, G.S.; Simon-Miller, A.; Hueso, R.; Bjoraker, G.L.; Mamoutkine, A.; Del, Rio-Gaztelurrutia; Gomez, J.M.; Buratti, B.; Clark, R.N.; Nicholson, P.D.; Sotin, C.

    2011-01-01

    Saturn's slow seasonal evolution was disrupted in 2010-2011 by the eruption of a bright storm in its northern spring hemisphere. Thermal infrared spectroscopy showed that within a month, the resulting planetary-scale disturbance had generated intense perturbations of atmospheric temperatures, winds, and composition between 20?? and 50??N over an entire hemisphere (140,000 kilometers). The tropospheric storm cell produced effects that penetrated hundreds of kilometers into Saturn's stratosphere (to the 1-millibar region). Stratospheric subsidence at the edges of the disturbance produced "beacons" of infrared emission and longitudinal temperature contrasts of 16 kelvin. The disturbance substantially altered atmospheric circulation, transporting material vertically over great distances, modifying stratospheric zonal jets, exciting wave activity and turbulence, and generating a new cold anticyclonic oval in the center of the disturbance at 41??N.

  5. A Close Encounter with a Saturn Kilometric Radiation Source Region

    Science.gov (United States)

    Kurth, W. S.; Gurnett, D. A.; Menietti, J. D.; Mutel, R. L.; Kivelson, M. G.; Bunce, E. J.; Cowley, S. W. H.; Talboys, D. L.; Dougherty, M. K.; Arridge, C.; Coates, A.; Grimald, S.; Lamy, L.; Zarka, P.; Cecconi, B.; Schippers, P.; André, N.; Louarn, P.; Mitchell, D.; Leisner, J.; Morooka, M.

    Earth-orbiting satellites have routinely traversed the source regions of auroral kilometric radiation. This radio emission is generated via the cyclotron maser instability very close to the electron cyclotron frequency. While Cassini's orbit has crossed auroral field lines, the radial distance at auroral latitudes is typically too high for the analogous Saturn kilometric radiation source. However, on Oct. 17, 2008, the Radio and Plasma Wave Science instrument detected the kilometric radiation at and just below the electron cyclotron frequency. At this time the spacecraft was at a distance of 5 Saturn radii, at 0.9 hours local time, and on L-shells in the range of 25 to above 30. Here the magnetic field suggests the corresponding current was directed upward, away from the planet. Low energy electron observations by the Cassini Plasma Spectrometer instrument suggest that growth of the SKR is likely due to an unstable shell-like distribution.

  6. The formation of the Cassini division in Saturn's rings

    Science.gov (United States)

    Goldreich, P.; Tremaine, S.

    1978-01-01

    An explanation for the size and location of the Cassini division in Saturn's rings is proposed. The explanation is based on the collective response of the particles in the ring to the resonant forcing by Mimas. An upper limit is calculated for the width of the gap that could be opened at a resonance. In addition, an estimate is obtained regarding the damping of the density waves by viscous and nonlinear effects. A picture is presented of the development of a gap. The results are compared with the observed properties of the divisions in Saturn's rings. The exact position of the inner edge of the Cassini division is difficult to predict, because the 2:1 resonance lies very near several weaker resonances (4:2 and 6:3 with Mimas, 4:1 with Tethys). However, the edge should lie near 17 seconds, and this is consistent with ground based observations.

  7. Exploring overstabilities in Saturn's A ring using two stellar occultations

    CERN Document Server

    Hedman, M M; Salo, H

    2014-01-01

    Certain regions of Saturn's rings exhibit periodic opacity variations with characteristic radial wavelengths of up to a few hundred meters that have been attributed to viscous overstabilities. The Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft observed two stellar occultations of the star gamma Crucis that had sufficient resolution to discern a sub-set of these periodic patterns in a portion of the A ring between 124,000 and 125,000 km from Saturn center. These data reveal that the wavelengths and intensities of the patterns vary systematically across this region, but that these parameters are not strictly determined by the ring's average optical depth. Furthermore, our observations indicate that these opacity variations have an azimuthal coherence scale of around 3000 km.

  8. New Secular Resonances Involving the Irregular Satellies of Saturn

    Science.gov (United States)

    Cuk, M.; Burns, J. A.; Carruba, V.; Nicholson, P. D.; Jacobson, R. A.

    2002-09-01

    We report that some of the recently found irregular satellites of Saturn, and possibly Uranus, dwell in hitherto unobserved resonances. These include the Kozai resonance, previously postulated but never before found in our Solar System. We also describe a new type of secular resonance for irregular satellites at higher inclinations (40-45o ), which locks the satellite's pericenter with that of the planet. Comparing theoretical predictions (Carruba et al. 2002)with the orbits of those Saturnian irregulars having inclinations around 45o , we found that Saturn's 2000_S5 and 2000_S6 have extremely slow motions of their arguments of pericenter, and their pericenters are presently almost 90 degrees away from their nodes (Jacobson 2001). Longitude of pericenter of another prograde satellite of Saturn, 2000_S3, precesses extremely slowly (Jacobson 2001). We simulated the motion of a clone of 2000_S3 and found that its longitude of pericenter could be librating around that of Saturn, with a very long period (on the order of 30,000 years) and large amplitude (120o ). The nature of this resonance appears different from one affecting certain Jovian moons (Saha and Tremaine 1993). If the amplitude of pericenter librations can be that large, another Saturnian irregular, 2000_S2, could be in a similar resonance. The Uranian retrograde satellites Stephano and Caliban (at inclinations of about 140o ) also have ϖ's that precess very slowly and are roughly aligned with Uranus's (Jacobson 2000). We are currently examining their motion to see if they are also in a resonance similar to that seen at 2000_S3.

  9. Saturn's aurora observed by the Cassini camera at visible wavelengths

    Science.gov (United States)

    Dyudina, Ulyana A.; Ingersoll, Andrew P.; Ewald, Shawn P.; Wellington, Danika

    2016-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70° and 80° latitude north and between 65° and 80° latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 h. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of ∼1 h. Smaller, 1000-km-scale structures may move faster or lag behind Saturn's rotation on timescales of tens of minutes. The persistence of nearly-corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10.65 ± 0.15 h for 2009 in the northern oval and 10.8 ± 0.1 h for 2012 in the southern oval. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time.

  10. Modeling plasma pressure anisotropy's effect on Saturn's global magnetospheric dynamics

    Science.gov (United States)

    Tilley, M.; Harnett, E. M.; Winglee, R.

    2014-12-01

    A 3D multi-fluid, multi-scale plasma model with a complete treatment of plasma pressure anisotropy is employed to study global magnetospheric dynamics at Saturn. Cassini has observed anisotropies in the Saturnian magnetosphere, and analyses have showed correlations between anisotropy and plasma convection, ring current structure and intensity, confinement of plasma to the equatorial plane, as well as mass transport to the outer magnetosphere. The energization and transport of plasma within Saturn's magnetosphere is impactful upon the induced magnetic environments and atmospheres of potentially habitable satellites such as Enceladus and Titan. Recent efforts to couple pressure anisotropy with 3D multi-fluid plasma modeling have shown a significant move towards matching observations for simulations of Earth's magnetosphere. Our approach is used to study the effects of plasma pressure anisotropy on global processes of the Saturnian magnetosphere such as identifying the effect of pressure anisotropy on the centrifugal interchange instability. Previous simulation results have not completely replicated all aspects of the structure and formation of the interchange 'fingers' measured by Cassini at Saturn. The related effects of anisotropy, in addition to those mentioned above, include contribution to formation of MHD waves (e.g. reduction of Alfvén wave speed) and formation of firehose and mirror instabilities. An accurate understanding of processes such as the interchange instability is required if a complete picture of mass and energy transport at Saturn is to be realized. The results presented here will detail how the inclusion of a full treatment of pressure anisotropy for idealized solar wind conditions modifies the interchange structure and shape of the tail current sheet. Simulation results are compared to observations made by Cassini.

  11. Modeling the ion abundances in Saturn's inner magnetosphere

    Science.gov (United States)

    Fleshman, B. L.; Bagenal, F.; Delamere, P. A.

    2011-12-01

    Water ejected from Enceladus's plumes provides much of the material that fills both the dense H2O torus centered on Enceladus's orbit, as well as Saturn's neutral clouds which extend at least four times farther from Saturn. Photo- and impact ionization transforms a few percent of these neutrals into the ions co-rotating with Saturn's magnetosphere, and charge exchange is responsible for a substantial redistribution among the hydrogen and water-group ions, though it does not alter the overall plasma density. In this paper, we explore ion abundances at Saturn with a chemistry model developed to include all of these processes. Building on our earlier attempts, we now include a source of neutrals from a neutral cloud model, so as to advance our description to include radial and latitudinal variations. At the same time, we now prescribe a radially-varying plasma diffusion coefficient to study the magnetosphere's inability to contain centrifigually-unstable plasma. We also are interested in the effect of hot electrons (102-103 eV) beamed along field lines into the equatorial region chiefly of interest. Our parameter study of radial diffusion and hot-electron flux is anchored to available Cassini CAPS water-group and proton abundances. Preliminary results suggest an injection of ~10 MW by hot electrons, and reveal promising radial trends in the water-group abundances that agree well with Sittler et al. (2008). We can also simulate an Enceladus torus dominated H3O+ -- a result not obtainable prior to coupling the chemistry and neutral cloud models.

  12. Magnetotail Reconnection and Flux Circulation: Jupiter and Saturn Compared

    Science.gov (United States)

    Jackman, C. M.; Vogt, M. F.; Slavin, J. A.; Cowley, S. W. H.; Boardsen, S. A.

    2011-01-01

    The Jovian magnetosphere has been visited by eight spacecraft, and the magnetometer data have been used to identify dozens of plasmoids and 250 field dipolarizations associated with magnetic reconnection in the tail [e.g. Vogt et al., 2010]. Since the arrival of the Cassini spacecraft at Saturn in 2004, the magnetometer instrument has also been used to identify reconnection signatures. The deepest magnetotail orbits were in 2006, and during this time 34 signatures of plasmoids were identified. In this study we compare the statistical properties of plasmoids at Jupiter and Saturn such as duration, size, location, and recurrence period. Such parameters can be influenced by many factors, including the different Dungey cycle timescales and cross-magnetospheric potential drops at the two planets. We present superposed epoch analyses of plasmoids at the two planets to determine their average properties and to infer their role in the reconfiguration of the nightside of the magnetosphere. We examine the contributions of plasmoids to the magnetic flux transfer cycle at both planets. At Jupiter, there is evidence of an extended interval after reconnection where the field remains northward (analogous to the terrestrial post-plasmoid plasma sheet). At Saturn we see a similar feature, and calculate the amount of flux closed on average in reconnection events, leading us to an estimation of the recurrence rate of plasmoid release.

  13. Rotational modulation of Saturn's radio emissions after equinox

    Science.gov (United States)

    Ye, Shengyi; Fischer, Georg; Kurth, William; Gurnett, Donald

    2016-04-01

    The modulation rate of Saturn kilometric radiation (SKR), originally thought to be constant, was found to vary with time by comparing the Voyager and Ulysses observations. More recently, Cassini RPWS observations of SKR revealed two different modulation rates, one associated with each hemisphere of Saturn, and it was proposed that the rotation rates are subject to seasonal change. The almost continuous observations of SKR, Saturn narrowband emission, and auroral hiss by RPWS provide a good method of tracking the rotation rates of the planet's magnetosphere. We will show that the rotation rate of the northern SKR is slower than that of the southern SKR in 2015. Auroral hiss provides another unambiguous method of tracking the rotation signals from each hemisphere because the whistler mode wave cannot cross the equator. Rotation rates of auroral hiss are shown to agree with those of SKR when both are observed at high latitudes. The dual rotation rates of 5 kHz narrowband emissions reappeared after a long break since equinox and they agree with those of auroral hiss in 2013.

  14. Rotating magnetospheres: transport compared at Jupiter and Saturn

    Science.gov (United States)

    Kivelson, M. G.; Southwood, D. J.; Dougherty, M. K.

    The magnetospheres of Jupiter and Saturn are dominated by the effects of rotation and the associated outward stress exerted by heavy ions picked up near the inner moons Fields and particle measurements in both systems show dramatic signatures of rotational periodicity At Jupiter the periodicity results principally from the effects of dipole tilt and the related displacements of the equatorial plasma sheet At Saturn there is little dipole tilt yet field and plasma properties vary periodically Efforts to understand how Saturn s rotational motion can be converted into what appears to be radial motion a conversion from rotation to rocking or reciprocating motion that is imposed in mechanical systems by a camshaft have recently focused on convective patterns with preferred sectors for transport see Southwood et al this session It is possible that similar effects are present at Jupiter and can account for plasma properties that have been described in terms of what has been referred to as the magnetic anomaly model Hill Goertz and Dessler 1983 This talk will use magnetometer data for the two systems to identify the possibly subtle signatures of the camshaft effect at Jupiter

  15. 3-Dimensional simulations of storm dynamics on Saturn

    Science.gov (United States)

    Hueso, R.; Sanchez-Lavega, A.

    2000-10-01

    The formation and evolution of convective clouds in the atmosphere of Saturn is investigated using an anelastic three-dimensional time-dependent model with parameterized microphysics. The model is designed to study the development of moist convection on any of the four giant planets and has been previously used to investigate the formation of water convective storms in the jovian atmosphere. The role of water and ammonia in moist convection is investigated with varying deep concentrations. Results imply that most of the convective activity observed at Saturn may occur at the ammonia cloud deck while the formation of water moist convection may happen only when very strong constraints on the lower troposphere are met. Ammonia storms can ascend to the 300 mb level with vertical velocities around 30 ms-1. The seasonal effect on the thermal profile at the upper troposphere may have important effects on the development of ammonia storms. In the cases where water storms can develop they span many scale heights with peak vertical velocities around 160 ms-1 and cloud particles can be transported up to the 150 mb level. These predicted characteristics are similar to the Great White Spots observed in Saturn which, therefore, could be originated at the water cloud base level. This work has been supported by Gobierno Vasco PI 1997-34. R. Hueso acknowledges a PhD fellowship from Gobierno Vasco.

  16. Quasiperiodic ULF-pulsations in Saturn's magnetosphere

    Directory of Open Access Journals (Sweden)

    G. Kleindienst

    2009-02-01

    Full Text Available Recent magnetic field investigations made onboard the Cassini spacecraft in the magnetosphere of Saturn show the existence of a variety of ultra low frequency plasma waves. Their frequencies suggest that they are presumably not eigenoscillations of the entire magnetospheric system, but excitations confined to selected regions of the magnetosphere. While the main magnetic field of Saturn shows a distinct large scale modulation of approximately 2 nT with a periodicity close to Saturn's rotation period, these ULF pulsations are less obvious superimposed oscillations with an amplitude generally not larger than 3 nT and show a package-like structure. We have analyzed these wave packages and found that they are correlated to a certain extent with the large scale modulation of the main magnetic field. The spatial localization of the ULF wave activity is represented with respect to local time and Kronographic coordinates. For this purpose we introduce a method to correct the Kronographic longitude with respect to a rotation period different from its IAU definition. The observed wave packages occur in all magnetospheric regions independent of local time, elevation, or radial distance. Independent of the longitude correction applied the wave packages do not occur in an accentuated Kronographic longitude range, which implies that the waves are not excited or confined in the same selected longitude ranges at all times or that their lifetime leads to a variable phase with respect to the longitudes where they have been exited.

  17. Spontaneous axisymmetry breaking of Saturn's external magnetic field

    CERN Document Server

    Goldreich, P; Goldreich, Peter; Farmer, Alison J.

    2006-01-01

    Saturn's magnetic field is remarkably axisymmetric. Its dipole axis is inclined by less than 0.2 deg with respect to its rotation axis. Rotationally driven convection of magnetospheric plasma breaks the axisymmetry of its external magnetic field. Field aligned currents transfer angular momentum from the planet to a tongue of outflowing plasma. This transfer slows the rate of rotation of the ionosphere relative to that of the underlying atmosphere. The currents are the source for the non-axisymmetric components of the field. The common rotation rates of these components and Saturn's kilometric radio (SKR) bursts is that of the plasma near the orbit of Enceladus, and by extension the rotation rate in the ionosphere to which this plasma is coupled. That rate tells us nothing about the rotation rate of Saturn's deep interior. Of that we remain ignorant. Magnetic perturbations with magnitudes similar to those observed by Cassini are produced for Mdot ~ 10^4 g/s, a value similar to estimates for the rate of product...

  18. The domination of Saturn's low latitude ionosphere by ring `rain'

    CERN Document Server

    O'Donoghue, J; Melin, H; Jones, G H; Cowley, S W H; Miller, S; Baines, K H; Blake, J S D

    2013-01-01

    Saturn's ionosphere is produced when the otherwise neutral atmosphere is exposed to a flow of energetic charged particles or solar radiation. At low latitudes the latter should result in a weak planet-wide glow in infrared (IR), corresponding to the planet's uniform illumination by the Sun. The observed low-latitude ionospheric electron density is lower and the temperature higher than predicted by models. A planet-ring magnetic connection has been previously suggested in which an influx of water from the rings could explain the lower than expected electron densities in Saturn's atmosphere. Here we report the detection of a pattern of features, extending across a broad latitude band from ~25 to 60 degrees, that is superposed on the lower latitude background glow, with peaks in emission that map along the planet's magnetic field lines to gaps in Saturn's rings. This pattern implies the transfer of charged water products from the ring-plane to the ionosphere, revealing the influx on a global scale, flooding betw...

  19. Rotational modulation of Saturn's radio emissions after equinox

    Science.gov (United States)

    Ye, S.-Y.; Fischer, G.; Kurth, W. S.; Menietti, J. D.; Gurnett, D. A.

    2016-12-01

    Saturn kilometric radiation (SKR), narrowband emission, and auroral hiss are periodically modulated due to Saturn's rotation, and the periods were found to vary with time. We analyze Cassini observations of Saturn's radio emissions with the main focus on the four years 2012-2015. It is shown that the rotation rates of SKR north and south were different since mid-2012 with SKR north being faster until autumn 2013, followed by a 1 year interval of similar north and south rotation rates and phases, before the northern SKR component finally became slower than the southern SKR in late 2014. The dual rotation rates of 5 kHz narrowband emissions reappeared for slightly longer than 1 year after a long break since equinox. Auroral hiss provides an unambiguous way of tracking the rotation signals from each hemisphere because the whistler mode waves cannot cross the equator. Rotation rates of auroral hiss and narrowband emissions are consistent with each other and those of SKR when they are observed at high latitudes in early 2013. The phase difference between SKR and auroral hiss and the intensity of auroral hiss are local time dependent.

  20. Are Dual Periodicities at Saturn Really, Really Real?

    Science.gov (United States)

    Carbary, J. F.

    2011-12-01

    Since the discovery of dual periodicities in Saturn's kilometric radiation (SKR), similar dual periods have been putatively observed in energetic charged particles, energetic neutral atoms, low energy plasma, and magnetic field oscillations. Ostensibly, one period (~10.8 hours) derives from a source in the southern hemisphere, while the second period (~10.6 hours) derives from a source in the northern hemisphere. Recent work on SKR, however, has demonstrated that at least southern SKR simultaneously oscillates at both frequencies. Recent work in the magnetic field oscillations further indicates that dual periodicities can sporadically arise from "beating" of Cassini's orbit with the single southern period. A rotating spiral configuration of the plasma sheet can readily produce dual periods in energetic particle data when considered along the Cassini trajectory. Furthermore, solar wind modulation at ~26 days of any "carrier" phenomena at ~10.7 hours will generate a dual frequency spectrum very similar to that observed in the SKR, as well as Saturn's particles and fields. This presentation suggests that Saturn's magnetosphere really has only one fundamental (carrier) period and that dual (or even multiple) periodicities arise when this fundamental is amplitude-modulated by an external driver such as the solar wind, Titan, or even the orbit of Cassini!

  1. The mass flux of micrometeoroids into the Saturn

    Science.gov (United States)

    Kempf, Sascha; Altobelli, Nicolas; Horanyi, Mihaly; Srama, Ralf

    2014-05-01

    The origin of Saturn's ring is still not known. There is an ongoing argument whether Saturn's ring are rather young or have been formed shortly after Saturn together with its satellites. The water-ice rings contain about 5% rocky material resulting from continuous meteoroid bombardment of the ring material with interplanetary micrometeoroids. Knowledge of the incoming mass flux would allow to estimate the ring's exposure time. Model calculations suggest exposure times of 108 years implying a late ring formation. This scenario is problematic because the tidal disruption of a Mimas-sized moon or of a comet within the planet's Roche zone would lead to a much larger rock content as observed today. Here we report on the first direct measurements of the meteoroid flux into the Saturnian system by Cassini's Cosmic Dust Analyzer (CDA). We measured the impact speed vectors of about 100 extrinsic micrometeoroids ≥ 2μm and determined their orbital elements. On the basis of these measurements we determined the mass flux into the Saturnian system. Our findings suggest a ring exposure time of 4.5 billion years and is in support of an early ring generation from a proto-Titan during the formation of the Saturnian system.

  2. Sensitivity of Saturn's orbit to a hypothetical distant planet

    Science.gov (United States)

    Folkner, William; Jacobson, Robert A.; Park, Ryan; Williams, James G.

    2016-10-01

    Several distant scattered Kuiper belt objects have similar perihelion directions that might be aligned due to the influence an unknown planet well outside the orbit of Neptune (Batygin & Brown, 2016 Astronomical J. 151:22). Such a planet, with a mass up to an order of magnitude larger than the Earth, would affect the rest of the solar system. Saturn, which is well observed from radio range and VLBI observations of the Cassini spacecraft, provides an opportunity to look for these perturbations. An unknown large planet would be expected to affect the orbit of Saturn, but the effect might be partially absorbed in the estimation of parameters used to fit the planetary ephemerides. Ephemeris parameters include the planetary orbital elements, the mass of the Sun and the masses of asteroids that perturb the orbit of Mars. Earlier analysis of the Cassini data showed no effect as suggested by the Modified Newtonian Dynamics theory (Hees et al., 2014 Phys. Rev. D 89:102002). We present an updated Cassini data set, with the accuracy of ranges to Saturn improved through updated estimates of the Cassini spacecraft orbit, and an analysis of the largest possible perturbing distant planet mass consistent with the ranging data.

  3. Long-term changes in reflectivity and larger scale motions in the atmospheres of Jupiter and Saturn

    Science.gov (United States)

    Beebe, R. F.

    1986-01-01

    A multi-color, broad-band photographic program for monitoring atmospheric variability of Jupiter and Saturn with the 61-cm, f/75 telescope was continued. The archivial product consists of approximately 20 sequential images on 3 1/4 x 4 1/4 glass plates with a plate scale of 4.53 arc sec/mm. An eleven-step sensitometric wedge, recorded times of acquisition, and fiducial marks which determine the orientation of the plate, are recorded on each individual plate. This allows accurate positional measurements, as well as detailed relative surface brightness determinations. Detailed measurements of the Red Spot are being utilized in a study of zonal velocity variation and the ability to predict the longitude of the Red Spot during the Galileo mission. An ongoing 5-color series of Saturn has been maintained to map the seasonal changes in the belt-zone reflectivity. Digitization of a series of blue images containing the Red Spot and a series of red and blue images excluding the Red Spot are being processed and reduced to normalized surface brightness maps. This data is being utilized to map time-dependent brightness variations of selected features, belts, and ones.

  4. Saturn's Great Storm of 2010-2011: Cloud particles containing ammonia and water ices indicate a deep convective origin. (Invited)

    Science.gov (United States)

    Sromovsky, L. A.; Baines, K. H.; Fry, P.

    2013-12-01

    Saturn's Great Storm of 2010-2011 was first detected by amateur astronomers in early December 2010 and later found in Cassini Imaging Science Subsystem (ISS) images taken on 5 December, when it took the form of a 1000 km wide bright spot. Within a week the head of the storm grew by a factor of ten in width and within a few months created a wake that encircled the planet. This is the sixth Great Saturn Storm in recorded history, all having appeared in the northern hemisphere, and most near northern summer solstice at intervals of roughly 30 years (Sanchez-Lavega et al. 1991, Nature 353, 397-401). That the most recent storm appeared 10 years early proved fortunate because Cassini was still operating in orbit around Saturn and was able to provide unique observations from which we could learn much more about these rare and enormous events. Besides the dramatic dynamical effects displayed at the visible cloud level by high-resolution imaging observations (Sayanagi et al. 2013, Icarus 223, 460-478), dramatic thermal changes also occurred in the stratosphere above the storm (Fletcher et al. 2011, Science 332, 1413), and radio measurements of lightning (Fischer et al., 2011, Nature 475, 75-77) indicated strong convective activity at deeper levels. Numerical models of Saturn's Giant storms (Hueso and Sanchez-Lavega 2004, Icarus 172, 255-271) suggest that they are fueled by water vapor condensation beginning at the 10-12 bar level, some 250 km below the visible cloud tops. That idea is also supported by our detection of water ice near the cloud tops (Sromovsky et al. 2013, Icarus 226, 402-418). From Cassini VIMS spectral imaging taken in February 2011, we learned that the storm's cloud particles are strong absorbers of sunlight at wavelengths from 2.8 to 3.1 microns. Such absorption is not seen on Saturn outside of storm regions, implying a different kind of cloud formation process as well as different cloud composition inside the storm region. We found compelling evidence

  5. The variable rotation period of the inner region of Saturn's plasma disk.

    Science.gov (United States)

    Gurnett, D A; Persoon, A M; Kurth, W S; Groene, J B; Averkamp, T F; Dougherty, M K; Southwood, D J

    2007-04-20

    We show that the plasma and magnetic fields in the inner region of Saturn's plasma disk rotate in synchronism with the time-variable modulation period of Saturn's kilometric radio emission. This relation suggests that the radio modulation has its origins in the inner region of the plasma disk, most likely from a centrifugally driven convective instability and an associated plasma outflow that slowly slips in phase relative to Saturn's internal rotation. The slippage rate is determined by the electrodynamic coupling of the plasma disk to Saturn and by the drag force exerted by its interaction with the Enceladus neutral gas torus.

  6. Modeling of global variations and ring shadowing in Saturn's ionosphere

    Science.gov (United States)

    Moore, L. E.; Mendillo, M.; Müller-Wodarg, I. C. F.; Murr, D. L.

    2004-12-01

    A time-dependent one-dimensional model of Saturn's ionosphere has been developed as an intermediate step towards a fully coupled Saturn Thermosphere-Ionosphere Model (STIM). A global circulation model (GCM) of the thermosphere provides the latitude and local time dependent neutral atmosphere, from which a globally varying ionosphere is calculated. Four ion species are used (H +, H +2, H +3, and He +) with current cross-sections and reaction rates, and the SOLAR2000 model for the Sun's irradiance. Occultation data from the Voyager photopolarimeter system (PPS) are adapted to model the radial profile of the ultraviolet (UV) optical depth of the rings. Diurnal electron density peak values and heights are generated for all latitudes and two seasons under solar minimum and solar maximum conditions, both with and without shadowing from the rings. Saturn's lower ionosphere is shown to be in photochemical equilibrium, whereas diffusive processes are important in the topside. In agreement with previous 1-D models, the ionosphere is dominated by H + and H +3, with a peak electron density of ˜10 electrons cm -3. At low- and mid-latitudes, H + is the dominant ion, and the electron density exhibits a diurnal maximum during the mid-afternoon. At higher latitudes and shadowed latitudes (smaller ionizing fluxes), the diurnal maximum retreats towards noon, and the ratio of [H +]/[H +3] decreases, with H +3 becoming the dominant ion at altitudes near the peak (˜1200-1600 km) for noon-time hours. Shadowing from the rings leads to attenuation of solar flux, the magnitude and latitudinal structure of which is seasonal. During solstice, the season for the Cassini spacecraft's encounter with Saturn, attenuation has a maximum of two orders of magnitude, causing a reduction in modeled peak electron densities and total electron column contents by as much as a factor of three. Calculations are performed that explore the parameter space for charge-exchange reactions of H + with

  7. The Case for Massive and Ancient Rings of Saturn

    Science.gov (United States)

    Esposito, Larry W.

    2016-10-01

    Analysis of Voyager and Pioneer 11 results give a mass for Saturn's rings, M = 5 x 10-8 Msat. This is about the mass of Saturn's small moon Mimas. This has been interpreted as a lower limit to the ring mass (Esposito et al 1983), since the thickest parts of the rings were not penetrated by the stellar occultstion, and this calculation assumes an unvarying particle size throughout the rings. Because the rings are constantly bombarded by micrometeroids, their current composition of nearly pure water ice implies such low mass rings must have formed recently. The case is particularly strong for Saturn's A ring, where the data are the best, implying the A ring is less than 10% of the age of the Saturn (Esposito 1986). Cassini results compound this problem. UVIS spectra are consistent with either young rings or rings about 10x as massive as the Voyager estimate (Elliott and Esposito (2011). CDA confirms the impacting mass flux is similar to that assumed for the pollution calculations (Kempf etal 2015). VIMS analysis of density wave signatures in the B ring gives a value of about 1/3 the Voyager value (Hedmann etal 2016). This VIMS result implies the rings are even younger! The problem is that young rings are very unlikely to be formed recently, meaning that we live in a very special epoch, following some unlikely recent origin… like disruption of a medium sized moon or capture of the fragments of a disrupted comet (Charnoz etal 2009).To take the VIMS results at face value, Saturn's low mass rings must be very young. The optically thick B ring must be made of small, porous or fractal particles. An alternative is that we accept the higher mass interpretation of the Pioneer 11 results (Esposito etal 2008) using the granola bar model of Colwell etal 2007. This would imply that the density wave structure seen by VIMS is not sensing all the mass in the rings, where structure near strong resonances is dominted by temporary aggregates, and where non-linear effects cause the

  8. Moist convective storms in the atmosphere of Saturn

    Science.gov (United States)

    Hueso, R.; Sánchez-Lavega, A.

    2003-05-01

    Moist convective storms might be a key aspect in the global energy budget of the atmospheres of the Giant Planets. In spite of its dull appearance, Saturn is known to develop the largest scale convective storms in the Solar System, the Great White Spots, the last of them arising in 1990 triggered a planetary scale disturbance that encircled the whole Equatorial region. However, Saturn seems to be very much less convective than Jupiter, being convective storms rare and small for the most part of the cases. Here we present simulations of moist convective storms in the atmosphere of Saturn at different latitudes, the Equator and 42 deg S, the regions where most of the convective activity of the planet has been observed. We use a 3D anelastic model of the atmosphere with parameterized microphysics (Hueso and Sánchez-Lavega, 2001) and we study the onset and evolution of moist convective storms. Ammonia storms are able to develop only if the static stability of the upper atmosphere is slightly decreased. Water storms are difficult to develop requiring very specific atmospheric conditions. However, when they develop they can be very energetic arriving at least to the 150 mbar level. The Coriolis forces play a mayor role in the characteristics of water based storms in the atmosphere of Saturn. The 3-D Coriolis forces at the Equator transfer upward momentum to westward motions acting to diminish the strength of the equatorial jet. The GWS of 1990 could have been a mayor force in reducing the intensity of the equatorial jet stream as revealed recently (Sánchez-Lavega et al. Nature, 2003). The Cassini spacecraft will arrive to Saturn in a year. Its observations of the atmosphere will allow to measure the amount of convective activity on the planet, its characteristics and it will clarify the role of moist convection in the atmospheric dynamics of the Giant Planets. Acknowledgements: This work was supported by the Spanish MCYT PNAYA 2000-0932. RH acknowledges a Post

  9. The Source of Planetary Period Oscillations in Saturn's Magnetosphere

    Science.gov (United States)

    Khurana, Krishan K.; Mitchell, Jonathan L.; Mueller, Ingo C. F.

    2017-04-01

    In this presentation, we resolve a three-decades old mystery of how Saturn is able to modulate its kilometric wave radiation and many field and plasma parameters at the planetary rotation period even though its magnetic field is extremely axisymmetric. Such waves emanating from the auroral regions of planets lacking solid surfaces have been used as clocks to measure the lengths of their days, because asymmetric internal magnetic fields spin-modulate wave amplitudes. A review by Carbary and Mitchell (2013, Periodicities in Saturn's magnetosphere, Reviews of Geophysics, 51, 1-30) on the topic summarized findings from over 200 research articles, on what the phenomena is, how it is manifested in a host of magnetospheric and auroral parameters; examined several proposed models and pointed out their shortcomings. The topic has now been explored in several topical international workshops, but the problem has remained unsolved so far. By quantitatively modeling the amplitudes and phases of these oscillations in the magnetic field observed by the Cassini spacecraft, we have now uncovered the generation mechanism responsible for these oscillations. We show that the observed oscillations are the manifestations of two global convectional conveyor belts excited in Saturn's upper atmosphere by auroral heating below its northern and southern auroral belts. We demonstrate that a feedback process develops in Saturn system such that the magnetosphere expends energy to drive convection in Saturn's upper stratosphere but gains back an amplified share in the form of angular momentum that it uses to enforce corotation in the magnetosphere and power its aurorae and radio waves. In essence, we have uncovered a new mechanism (convection assisted loss of angular momentum in an atmosphere) by which gaseous planets lose their angular momentum to their magnetospheres and outflowing plasma at rates far above previous predictions. We next show how the m = 1 convection system in the upper

  10. GCR as a source for Inner radiation belt of Saturn.

    Science.gov (United States)

    Kotova, A.; Roussos, E.; Krupp, N.; Dandouras, I. S.

    2014-12-01

    During the insertion orbit of Cassini in 2004 the Ion and Neutron Camera measured significant fluxes of the energetic neutral atoms (ENA) coming from the area between the D-ring and the Saturn's atmosphere, what brought up the idea of the possible existence of the innermost radiation belt in this narrow gap (1). There are two main sources of energetic charged particles for such inner radiation belt: the interaction of the Galactic Cosmic Rays (GCR) with the Saturn's atmosphere and rings, which due to CRAND process can produce the keV-MeV ions or electrons in the region, and the double charge exchange of the ENAs, coming from the middle magnetosphere, what can bring the keV ions to the region of our interest. Using the particles tracer, which was developed in our group, and GEANT4 software, we study in details those two processes. With a particle tracer we evaluate the GCR access to the Saturn atmosphere and rings. Simulation of the GCR trajectories allows to calculate the energy spectra of the arriving energetic particles, which is much more accurate, compare to the analytically predicted spectra using the Stoermer theory, since simulation includes effects of the ring shadow and non-dipolar processes in the magnetosphere. Using the GEANT4 software the penetration of the GCR through the matter of rings was simulated, and the production of secondaries particles was estimated. Finally, the motion of secondaries was simulated using the particles tracer, and evaluation of the energy spectrum of neutrons the decay of which leads to the production of final CRAND elements in the inner Saturnian radiation belts was done. We show that for inner radiation belt most energetic ions comes from GCR interaction with rings, it's penetration and from interaction of secondaries with Saturn's atmosphere. This simulation allows us to predict the fluxes of energetic ions and electrons, which particle detector MIMI/LEMMS onboard the Cassini can measure during the so-called "proximal

  11. A Physical Model of Electron Radiation Belts of Saturn

    Science.gov (United States)

    Lorenzato, L.; Sicard-Piet, A.; Bourdarie, S.

    2012-04-01

    Radiation belts causes irreversible damages on on-board instruments materials. That's why for two decades, ONERA proposes studies about radiation belts of magnetized planets. First, in the 90's, the development of a physical model, named Salammbô, carried out a model of the radiation belts of the Earth. Then, for few years, analysis of the magnetosphere of Jupiter and in-situ data (Pioneer, Voyager, Galileo) allow to build a physical model of the radiation belts of Jupiter. Enrolling on the Cassini age and thanks to all information collected, this study permits to adapt Salammbô jovian radiation belts model to the case of Saturn environment. Indeed, some physical processes present in the kronian magnetosphere are similar to those present in the magnetosphere of Jupiter (radial diffusion; interaction of energetic electrons with rings, moons, atmosphere; synchrotron emission). However, some physical processes have to be added to the kronian model (compared to the jovian model) because of the particularity of the magnetosphere of Saturn: interaction of energetic electrons with neutral particles from Enceladus, and wave-particle interaction. This last physical process has been studied in details with the analysis of CASSINI/RPWS (Radio and Plasma Waves Science) data. The major importance of the wave particles interaction is now well known in the case of the radiation belts of the Earth but it is important to investigate on its role in the case of Saturn. So, importance of each physical process has been studied and analysis of Cassini MIMI-LEMMS and CAPS data allows to build a model boundary condition (at L = 6). Finally, results of this study lead to a kronian electrons radiation belts model including radial diffusion, interactions of energetic electrons with rings, moons and neutrals particles and wave-particle interaction (interactions of electrons with atmosphere particles and synchrotron emission are too weak to be taken into account in this model). Then, to

  12. Scavenging of ammonia by raindrops in Saturn's great storm clouds

    Science.gov (United States)

    Delitsky, M. L.; Baines, Kevin

    2016-10-01

    Observations of the great Saturn storms of 2010-2011 by Cassini instruments showed a very large depletion in atmospheric ammonia. While dynamics will play a role, the very high solubility of ammonia in water may be another important contributor to ammonia depletion in storms. Ammonia exists in Earth's atmosphere and rainstorms dissolve ammonia to a great degree, leaving almost no NH3 in the atmosphere. Studies by Elperin et al (2011, 2013) show that scavenging of ammonia is greatest as a rainstorm starts and lessens as raindrops fall, tapering off to almost zero by the time the rain reaches the ground (Elperin et al 2009). Ammonia is reaching saturation as it dissolves in the aqueous solution. As concentration increases, NH3 is then converted to aqueous species (NH3)x.(H2O)y (Max and Chapados 2013).Ammonia has the highest solubility in water compared to all other gases in the Saturn atmosphere. The Henry's Law constant for NH3 in water is 60 M/atm at 25 C. For H2S, it is 0.001 M/atm. In Saturn storms, it is "raining UP": As water-laden storm clouds convectively rise, ammonia gas will be scavenged and go into solution to a great degree, whilst all the other gases remain mostly in the gas phase. Aqueous ammonia acts as an antifreeze: if ammonia is dissolved in water cloud droplets to the limit of its solubility, as water droplets rise, they can stay liquid (and continue to scavenge NH3) to well below their normal freezing point of 0 Celsius (273 K). The freezing point for a 30 wt % water-ammonia solution is ~189 K. The pressure level where T = 189 K is at 2.8 bars. The normal freezing point of water occurs at the 9 bar pressure level in Saturn's atmosphere. 2.8 bars occurs at the -51 km altitude (below the 1 bar level). 9 bars is at the -130 km level: a difference of 79 km. A water droplet containing 30 wt% NH3 can move upwards from 9 bars to 2.8 bars (79 km) and still remain liquid, only freezing above that altitude. Calculations by the E-AIM model show that ammonia

  13. Self-gravity density waves in Saturn's rings A, B, and C

    Science.gov (United States)

    Griv, Evgeny

    The presence of fine-scale of the order of 100 m density structure in Saturn's brightest rings A and B with the appearance of record-grooves has been revealed by Voyager PPS stellar occultation, and Cassini scince images, UVIS and radio occultations. Both spacecraft missions have shown that these relatively large "irregular variations" in optical depth are not associated with any resonances with known or embedded satellites. This microstructure explains an azimuthal brightness assymetry in Saturn's A ring observed first by Camichel in 1958. We examine the problem of the linear stability of the Saturnian ring system of mutually gravitating particles with special emphasis on its fine-scale density wave structure (almost regularly spaced, aligned cylindric density enhancements and rarefications). In our theory, the density pattern is the manifestation of a compression (longitudinal) density wave propagating around the ring disk at a fixed angular phase velocity despite the general differential rotation of a system; the density enhancements consist of different material at different times. Jeans' gravitational instabilities of small-amolitude gravity perturbations (e.g., those produced by a spontaneous disturbance) are analysed through the use of hydrodynamic equations. An essential feature of this study is that the theory is not restricted by any assumptions regarding the thickness of the system. The ring disk is considered to be thin and its vertical structure is considered in a horizontally local approximation. In the dynamically equilibrium state, the density is regarded as nonuniform between two sharp surfaces, with a vacuum exterior. A plasma physics analytical method is given for the solution of the self-consistent system of the gasdynamical equations and the Poisson equation describing the stability of Saturn's rings when the system is perturbed in an arbitrary manner. That is, when a gravity perturbation does not distort the rings' plane (modes of even

  14. Evidence for dust-driven, radial plasma transport in Saturn's inner radiation belts

    Science.gov (United States)

    Roussos, E.; Krupp, N.; Kollmann, P.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Andriopoulou, M.

    2016-08-01

    between the magnetosphere and Saturn's faint rings that may drive such radial transport processes may also exist in previously reported measurements of plasma density by Cassini. Alternative explanations that do not involve enhanced plasma transport near the rings require the presence of a transient absorbing medium, such as E-ring clumps. Such clumps may form at the L-shell range where microsignatures have been observed due to resonances between charged dust and corotating magnetospheric structures, but remote imaging observations of the E-ring are not consistent with such a scenario.

  15. Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions

    CERN Document Server

    Bhardwaj, A; Elsner, R F; Ford, P G; Gladstone, G R; Bhardwaj, Anil; Cravens, Thomas E.; Elsner, Ronald F.; Ford, Peter G.

    2005-01-01

    Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one full Saturn rotation (10.7 hr) at each epoch. We report here the first observation of an X-ray flare from Saturn's non-auroral (low-latitude) disk, which is seen in direct response to an M6-class flare emanating from a sunspot that was clearly visible from both Saturn and Earth. Saturn's disk X-ray emissions are found to be variable on time scales of hours to weeks to months, and correlated with solar F10.7 cm flux. Unlike Jupiter, X-rays from Saturn's polar (auroral) region have characteristics similar to those from its disk. This report, combined with earlier studies, establishes that disk X-ray emissions of the giant planets Saturn and Jupiter are directly regulated by processes happening on the Sun. We suggest that these emissions could be monitored to study X-ray flaring from solar active regions when they are on the far side and not visible to Near-Earth space weather satellites.

  16. Saturn's Ionospheric Clock(s): A Concept for Generating and Maintaining Saturn's Observed Magnetospheric Periodicities

    Science.gov (United States)

    Mitchell, D. G.; Brandt, P. C.; Ukhorskiy, A. Y.

    2010-12-01

    Saturn’s 10.X hour periodicity, observed throughout the magnetosphere, remains a mystery. It has been observed in many regions, modulating many phenomena. During the Cassini mission most observations have shown a period at about 10.8 hours, expressed in Saturn kilometric radiation from the high latitude auroral zone, in magnetic field components (both equatorial and high latitude) from 3 to 12 Rs, in current sheet encounters in the outer magnetosphere and magnetotail, in energetic neutral atom emission from the equatorial magnetosphere, and in plasma and energetic particles throughout the magnetosphere. More recently, various authors have shown at least two dominant periods expressed (in SKR and in magnetic field components), with slightly different values in the southern and northern hemispheres. The cause of this behavior is still not accounted for. Although loosely associated with Saturn’s rotation, the variability in the period precludes a direct connection with Saturn’s interior (e.g., a magnetic anomaly). Other candidates that have been discussed by others are an ionospheric source (conductivity anomaly), a perturbation in the cold plasma circulation pattern, a magnetospheric cam, asymmetric ring current particle pressure, and/or a natural frequency of the magnetosphere (cavity mode or traveling wave front of some sort). In this paper we present a concept that derives its energy from the subcorotating cold, dense plasma (which exhibits a rotation period on the order of 13 to 14 hours throughout L-shells between ~3 and 20), but is triggered by a process linked with the ionosphere. Key components of the model include significant slippage between the ionosphere and the magnetosphere (with the ionosphere rotating at the expressed period in each hemisphere, only slightly more slowly than the planet interior), subcorotating cold dense plasma with a source in the inner magnetosphere, predominantly radial transport of the cold dense plasma in the rotational

  17. The near-surface electron radiation environment of Saturn's moon Mimas

    Science.gov (United States)

    Nordheim, Tom; Hand, Kevin P.; Paranicas, Christopher; Howett, Carly; Hendrix, Amanda R.; Jones, Geraint H.; Coates, Andrew

    2016-10-01

    Introduction: Saturn's inner mid-size moons are exposed to a number of external weathering processes, including charged particle bombardment and UV photolysis, as well as deposition of E ring grains and interplanetary dust. While optical remote sensing observations by several instruments onboard the Cassini spacecraft have revealed a number of weathering patterns across the surfaces of these moons, it is currently not entirely clear which external process is responsible for which observed weathering pattern. Here we focus on Saturn's moon Mimas and model the effect of energetic electron bombardment across its surface. Our results are discussed in the context of previously reported Cassini remote sensing observations of Mimas.Methods: To model the access of energetic electrons to different surface locations we used a guiding center, bounce-averaged approach which has previously been employed for the Jovian and Saturnian moons. The electron spectrum at the orbit of Mimas was implemented according to the fit functions provided by, which are based on averaged measurements from the Cassini Magnetospheric Imaging Instrument (MIMI) Low Energy Magnetospheric Measurement System (LEMMS) at a narrow corridor near the orbit of Mimas (~3.08 Rs) during the period 2004-2013. The interaction of electrons with the surface of Mimas was implemented using the PLANETOCOSMICS code, which is based on the Geant4 toolkit.Results: We predict a lens-shaped electron energy deposition pattern which extends down to ~cm depths at low latitudes near the center of the leading hemisphere. These results are consistent with previous remote sensing observations of a lens-shaped color anomaly [4] as well as a thermal inertia anomaly at this location. At the trailing hemisphere, we predict a similar lens-shaped electron energy deposition pattern, which to date has not been observed by the Cassini optical remote sensing instruments. We suggest that no corresponding lens-shaped weathering pattern has been

  18. The Evolution and Fate of Saturn's Stratospheric Vortex: Infrared Spectroscopy from Cassini

    Science.gov (United States)

    Fletcher, Leigh N.; Hesman, B. E.; Arhterberg, R. K.; Bjoraker, G.; Irwin, P. G. J.; Hurley, J.; Sinclair, J.; Gorius, N.; Orton, G. S.; Read, P. L.; Simon-Miller, A. A.; Flasar, F. M.

    2012-01-01

    The planet-encircling springtime storm in Saturn's troposphere (December 2010-July 2011) produced dramatic perturbations to stratospheric temperatures, winds and composition at mbar pressures that persisted long after the tropospheric disturbance had abated. Observations from the Cassini Composite Infrared Spectrometer (CIRS), supported by ground-based imaging from the VISIR instrument on the Very Large Telescope,is used to track the evolution of a large, hot stratospheric anticyclone between January 2011 and the present day. The evolutionary sequence can be divided into three phases: (I) the formation and intensification of two distinct warm airmasses near 0.5 mbar between 25 and 35N (one residing directly above the convective storm head) between January-April 2011, moving westward with different zonal velocities; (II) the merging of the warm airmasses to form the large single 'stratospheric beacon' near 40N between April and June 2011, dissociated from the storm head and at a higher pressure (2 mbar) than the original beacons; and (III) the mature phase characterized by slow cooling and longitudinal shrinkage of the anticyclone since July 2011, moving west with a near-constant velocity of 2.70+/-0.04 deg/day (-24.5+/-0.4 m/s at 40N). Peak temperatures of 220 K at 2 mbar were measured on May 5th 2011 immediately after the merger, some 80 K warmer than the quiescent surroundings. Thermal winds hear calculations in August 2011 suggest clockwise peripheral velocities of 200400 mls at 2 mbar, defining a peripheral collar with a width of 65 degrees longitude (50,000 km in diameter) and 25 degrees latitude. Stratospheric acetylene (C2H2) was uniformly enhanced by a factor of three within the vortex, whereas ethane (C2H6) remained unaffected. We will discuss the thermal and chemical characteristics of Saturn's beacon in its mature phase, and implications for stratospheric vortices on other giant planets.

  19. Images

    Data.gov (United States)

    National Aeronautics and Space Administration — Images for the website main pages and all configurations. The upload and access points for the other images are: Website Template RSW images BSCW Images HIRENASD...

  20. Seasonal variation of the radial brightness contrast of Saturn's rings viewed in mid-infrared by Subaru/COMICS

    Science.gov (United States)

    Fujiwara, Hideaki; Morishima, Ryuji; Fujiyoshi, Takuya; Yamashita, Takuya

    2017-02-01

    Aims: This paper investigates the mid-infrared (MIR) characteristics of Saturn's rings. Methods: We collected and analyzed MIR high spatial resolution images of Saturn's rings obtained in January 2008 and April 2005 with the COoled Mid-Infrared Camera and Spectrometer (COMICS) mounted on the Subaru Telescope, and investigated the spatial variation in the surface brightness of the rings in multiple bands in the MIR. We also composed the spectral energy distributions (SEDs) of the C, B, and A rings and the Cassini Division, and estimated the temperatures of the rings from the SEDs assuming the optical depths. Results: We found that the C ring and the Cassini Division were warmer than the B and A rings in 2008, which could be accounted for by their lower albedos, lower optical depths, and smaller self-shadowing effect. We also fonud that the C ring and the Cassini Division were considerably brighter than the B and A rings in the MIR in 2008 and the radial contrast of the ring brightness is the inverse of that in 2005, which is interpreted as a result of a seasonal effect with changing elevations of the Sun and observer above the ring plane. The reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A29

  1. A close look at Saturn's rings with Cassini VIMS

    Science.gov (United States)

    Nicholson, P.D.; Hedman, M.M.; Clark, R.N.; Showalter, M.R.; Cruikshank, D.P.; Cuzzi, J.N.; Filacchione, G.; Capaccioni, F.; Cerroni, P.; Hansen, G.B.; Sicardy, B.; Drossart, P.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Coradini, A.

    2008-01-01

    Soon after the Cassini-Huygens spacecraft entered orbit about Saturn on 1 July 2004, its Visual and Infrared Mapping Spectrometer obtained two continuous spectral scans across the rings, covering the wavelength range 0.35-5.1 ??m, at a spatial resolution of 15-25 km. The first scan covers the outer C and inner B rings, while the second covers the Cassini Division and the entire A ring. Comparisons of the VIMS radial reflectance profile at 1.08 ??m with similar profiles at a wavelength of 0.45 ??m assembled from Voyager images show very little change in ring structure over the intervening 24 years, with the exception of a few features already known to be noncircular. A model for single-scattering by a classical, many-particle-thick slab of material with normal optical depths derived from the Voyager photopolarimeter stellar occultation is found to provide an excellent fit to the observed VIMS reflectance profiles for the C ring and Cassini Division, and an acceptable fit for the inner B ring. The A ring deviates significantly from such a model, consistent with previous suggestions that this region may be closer to a monolayer. An additional complication here is the azimuthally-variable average optical depth associated with "self-gravity wakes" in this region and the fact that much of the A ring may be a mixture of almost opaque wakes and relatively transparent interwake zones. Consistently with previous studies, we find that the near-infrared spectra of all main ring regions are dominated by water ice, with a typical regolith grain radius of 5-20 ??m, while the steep decrease in visual reflectance shortward of 0.6 ??m is suggestive of an organic contaminant, perhaps tholin-like. Although no materials other than H2O ice have been identified with any certainty in the VIMS spectra of the rings, significant radial variations are seen in the strength of the water-ice absorption bands. Across the boundary between the C and B rings, over a radial range of ???7000 km, the

  2. Exploring the Jupiter's and Saturn's radiation belts with LOFAR

    Science.gov (United States)

    Girard, Julien N.; Zarka, Philippe; Pater Imke, de; Hess, Sebastien; Tasse, Cyril; Courtin, Regis; Hofstadter, Mark; Santos-Costa, Daniel; Nettelmann, Nadine; lorenzato, Lise

    2014-05-01

    Since its detection in the mid-fifties, the decimeter synchrotron radiation (DIM), originating from the radiation belts of Jupiter, has been extensively observed over a wide spectrum (from >300 MHz to 22 GHz) by various radio instruments (VLA, ATCA, WSRT, Cassini...). They provided accurate flux measurements as well as resolved maps of the emission that revealed spatial, temporal and spectral variabilities. The strong magnetic field (~4.2 G at the equator) is responsible for the radio emission generated by relativistic electrons. The emission varies at different time scales (short-time variations of hours to long-term variation over decades) due to the combination of visibility configuration (fast rotating 'dipole' magnetic field, beamed radio emission) and intrinsic local variations (interaction between relativistic electrons and satellites/dust, delayed effect of the solar wind ram pressure, impacts events) (e.g. de Pater & Klein, 1989; de Pater & Dunn, 2003; Bagenal (ed.) et al., 2004; Santos-Costa, 2009, 2011). A complete framework is necessary to fully understand the source, loss and transport processes of the electrons populating the inner magnetosphere over a wide frequency range. The low frequencies are associated with electron of lower energies situated in weaker magnetic field regions. LOFAR, the LOw Frequency ARray (LOFAR) (van Haarlem et al., 2012), the last generation of versatile and digital ground-based radio interferometer operates in the [30-250] MHz bandwidth. It brings very high time (~μsec), frequency (~kHz) and angular (~asec) resolutions and huge sensitivities (~mJy). In November 2011, a single 10-hour track enabled to cover an entire planetary rotation and led to image, for the first time, the radiation belts between 127-172 MHz (Girard et al. 2012, 2013). In Feb 2013, an 11-hour joint LOFAR/WSRT observing campaign seized the dyname state of the radiation belts from 45 MHz up to 5 GHz. We will present the current study of the radiation belts

  3. The Pole Orientation, Pole Precession, and Moment of Inertia Factor of Saturn

    Science.gov (United States)

    Jacobson, R. A.; French, R. G.; Nicholson, P. D.; Hedman, M.; Colwell, J. E.; Marouf, E.; Rappaport, N.; McGhee, C.; Sepersky, T.; Lonergan, K.

    2011-01-01

    This paper discusses our determination of the Saturn's pole orientation and precession using a combination of Earthbased and spacecraft based observational data. From our model of the polar motion and the observed precession rate we obtain a value for Saturn's polar moment of inertia

  4. Driving Saturn's magnetospheric periodicities from the upper atmosphere/ionosphere

    Science.gov (United States)

    Jia, Xianzhe; Kivelson, Margaret G.; Gombosi, Tamas I.

    2012-04-01

    Saturn's magnetospheric structure and the intensity of radio frequency emissions from its immediate surroundings are modulated at close to the planet's rotation period. Analogous rotation-modulated variations at Jupiter are readily interpreted as effects of the non-axisymmetric intrinsic magnetic field. At Saturn, to the contrary, the high level of axial symmetry in the intrinsic field suggests that the periodicity is not internally imposed. A number of mechanisms have been proposed to account for the observations. Each model explains a subset of the observations in a qualitative manner, but no quantitative models yet exist. Here, using a magnetohydrodynamic simulation, we investigate the magnetospheric perturbations that arise from a localized vortical flow structure in the ionosphere near 70° S-latitude that rotates at roughly the rate of planetary rotation. The model reproduces nearly quantitatively a host of observed magnetospheric periodicities associated with the period of the dominant (southern) radio frequency emissions during the Cassini epoch including rotating, quasi-uniform magnetic perturbations in the equatorial plane, rotating mass density perturbations, periodic plasmoid releases that we associate with observed bursts of energetic neutral atoms (ENAs), periodic oscillations of magnetospheric boundaries, current sheet flapping, and periodic modulation of the field-aligned currents linked to Saturn's kilometric radiation (SKR). The model is not unique but is representative of a class of models in which asymmetric flows in the (as yet unmeasured) upper atmosphere couple to the ionosphere and generate currents that flow into the magnetosphere. It can be extended to include the second periodicity that has been associated with SKR emissions in the northern hemisphere.

  5. Charged particle diffusion and acceleration in Saturn's radiation belts

    Science.gov (United States)

    Mckibben, R. B.; Simpson, J. A.

    1980-01-01

    In the present paper, an attempt is made to determine, from the observed intensity profiles for protons and electrons in the region of L smaller than 4, whether population of Saturn's innermost trapped radiation zones from an external source is possible. It is found that if diffusion proceeds in an episodic rather than a steady-state manner (long periods of quiescence interrupted by brief periods of rapid diffusion), the basic features of the observed phase space density profiles are qualitatively reproduced for both the trapped protons and electrons.

  6. Saturn's Doppler velocimetry wind measurements with VLT/UVES

    Science.gov (United States)

    Silva, Miguel; Mota Machado, Pedro; Luz, David; Sanchez-Lavega, Agustin; Hueso, Ricardo; Peralta, Javier

    2016-10-01

    We present Doppler wind velocity results of Saturn's zonal flow at ~0.4 mbar pressure level. Our aim is help to constrain the characterization of the equatorial jet at the referred altitude and the latitudinal variation of the zonal winds, to contribute to monitor the spatial and temporal variability in order to achieve a better understanding of the dynamics of Saturn's zonal winds, which Sánchez-Lavega et al. (2003, Nature, 423, 623) have found to have strongly changed in recent years, as the planet approached southern summer solstice.The UVES/VLT instrument has been used, which simultaneously achieves high spectral resolving power and high spatial resolution. The field has been derotated in order to have the aperture aligned perpendicularly to Saturn's rotation axis. In this configuration, spatial information in the East-West direction is preserved in a set of spectra in the direction perpendicular to dispersion.The technique of absolute accelerometry (AA, Connes, 1985, ApSS 110, 211) has been applied to the backscattered solar spectrum in order to determine the Doppler shift associated with the zonal circulation. Our measurements have been made in the wavelength range of 480-680 nm. Previously we successfully adapted this Doppler velocimetry technique for measuring winds at Venus cloud tops (Machado et al. 2012).The observations consisted of 4 blocks of 15 exposures of 90 sec, plus two shorter blocks of 9 exposures, totalling 7.3 hours of telescope time. In order to cover the whole disk the aperture has been offset by 1 arcsec in the North-South direction between consecutive exposures. Most of the northern hemisphere was covered by the rings. Saturn's diameter was 17.4 arcsec, and the slit aperture was 0.3x25 arcsec. The aperture offset between consecutive exposures was 1 arcsec. Two observations blocks of 9 exposures only covered the central part of the disk, and four others covered the whole disk. The sub-terrestrial point was at -26.1 degrees South. The

  7. Atmospheric, Ionospheric, and Energetic Radiation Environments of Saturn's Rings

    Science.gov (United States)

    Cooper, J. F.; Kollmann, P.; Sittler, E. C., Jr.; Johnson, R. E.; Sturner, S. J.

    2015-12-01

    Planetary magnetospheric and high-energy cosmic ray interactions with Saturn's rings were first explored in-situ during the Pioneer 11 flyby in 1979. The following Voyager flybys produced a wealth of new information on ring structure and mass, and on spatial structure of the radiation belts beyond the main rings. Next came the Cassini Orbiter flyover of the rings during Saturn Orbital Insertion in 2004 with the first in-situ measurements of the ring atmosphere and plasma ionosphere. Cassini has since fully explored the radiation belt and magnetospheric plasma region beyond the main rings, discovering how Enceladus acts as a source of water group neutrals and water ions for the ion plasma. But do the main rings also substantially contribute by UV photolysis to water group plasma (H+, O+, OH+, H2O+, H3O+, O2+) and neutrals inwards from Enceladus? More massive rings, than earlier inferred from Pioneer 11 and Voyager observations, would further contribute by bulk ring ice radiolysis from interactions of galactic cosmic ray particles. Products of these interactions include neutron-decay proton and electron injection into the radiation belts beyond the main rings. How does radiolysis from moon and ring sweeping of the radiation belt particles compare with direct gas and plasma sources from the main rings and Enceladus? Can the magnetospheric ion and electron populations reasonably be accounted for by the sum of the ring-neutron-decay and outer magnetospheric inputs? Pioneer 11 made the deepest radial penetration into the C-ring, next followed by Cassini SOI. What might Cassini's higher-inclination proximal orbits reveal about the atmospheric, ionospheric, and energetic radiation environments in the D-ring and the proximal gap region? Recent modeling predicts a lower-intensity innermost radiation belt extending from the gap to the inner D-ring. Other remaining questions include the lifetimes of narrow and diffuse dust rings with respect to plasma and energetic particle

  8. Convective and radiative heating of a Saturn entry probe

    Science.gov (United States)

    Tiwari, S. N.; Szema, K. Y.; Moss, J. N.; Subramanian, S. V.

    1984-01-01

    The extent of convective and radiative heating for a Saturn entry probe is investigated in the absence and presence of ablation mass injection. The flow in the shock layer is assumed to be axisymmetric, viscous and in local thermodynamic equilibrium. The importance of chemical nonequilibrium effects for both the radiative and convective nonblowing surface heating rates is demonstrated for prescribed entry conditions. Results indicate that the nonequilibrium chemistry can significantly influence the rate of radiative heating to the entry probes. With coupled carbon-phenolic ablation injection, the convective heating rates are reduced substantially. Turbulence has little effect on radiative heating but it increases the convective heating considerably.

  9. Saturn's rings resolved by the VLA. [Very Larg Array (VLA)

    Science.gov (United States)

    Depater, I.; Dickel, J. B.

    1982-01-01

    High resolution radio data of Saturn were obtained at 1.3, 2, 6, and 21 cm, at different inclination angles of the ring plane. Results on optical depth measurements in the rings are described. There is no wavelength dependence in the optical depth of the rings between 1.3 and 6 cm. This indicates that there are not many small particles (sizes of a few centimeters) in the B-ring, which ring is responsible for most of the observed obscuration. This result agrees with the Voyager radio occultation experiment.

  10. Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

    Science.gov (United States)

    Pendleton, Y. J.; Cruikshank, D. P.

    2014-01-01

    The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton & Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saurn. VIMS spaectral maps of PHoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and alophatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (approximately 5-20 micrometer size) spiral inward toward Saturn. They encounter Iapetus and Hperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, ad in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 approximately 4, which is larger than the value found in the diffuse ISM (approximately 2-2.5). In so far as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of procesing of the nebular material. There are other Phoebe-like TNOs that are presently

  11. Scientific Value of a Saturn Atmospheric Probe Mission

    Science.gov (United States)

    Simon-Miller, A. A.; Lunine, J. I.; Atreya, S. K.; Spilker, T. R.; Coustenis, A.; Atkinson, D. H.

    2012-01-01

    Atmospheric entry probe mISSions to the giant planets can uniquely discriminate between competing theories of solar system formation and the origin and evolution of the giant planets and their atmospheres. This provides for important comparative studies of the gas and ice giants, and to provide a laboratory for studying the atmospheric chemistries, dynamics, and interiors of all the planets including Earth. The giant planets also represent a valuable link to extrasolar planetary systems. As outlined in the recent Planetary Decadal Survey, a Saturn Probe mission - with a shallow probe - ranks as a high priority for a New Frontiers class mission [1].

  12. Ground-based observations of Saturn's auroral ionosphere over three days: Trends in H3+ temperature, density and emission with Saturn local time and planetary period oscillation

    Science.gov (United States)

    O'Donoghue, James; Melin, Henrik; Stallard, Tom S.; Provan, G.; Moore, Luke; Badman, Sarah V.; Cowley, Stan W. H.; Baines, Kevin H.; Miller, Steve; Blake, James S. D.

    2016-01-01

    On 19-21 April 2013, the ground-based 10-m W.M. Keck II telescope was used to simultaneously measure H3+ emissions from four regions of Saturn's auroral ionosphere: (1) the northern noon region of the main auroral oval; (2) the northern midnight main oval; (3) the northern polar cap and (4) the southern noon main oval. The H3+ emission from these regions was captured in the form of high resolution spectral images as the planet rotated. The results herein contain twenty-three H3+ temperatures, column densities and total emissions located in the aforementioned regions - ninety-two data points in total, spread over timescales of both hours and days. Thermospheric temperatures in the spring-time northern main oval are found to be cooler than their autumn-time southern counterparts by tens of K, consistent with the hypothesis that the total thermospheric heating rate is inversely proportional to magnetic field strength. The main oval H3+ density and emission is lower at northern midnight than it is at noon, in agreement with a nearby peak in the electron influx in the post-dawn sector and a minimum flux at midnight. Finally, when arranging the northern main oval H3+ parameters as a function of the oscillation period seen in Saturn's magnetic field - the planetary period oscillation (PPO) phase - we see a large peak in H3+ density and emission at ∼115° northern phase, with a full-width at half-maximum (FWHM) of ∼44°. This seems to indicate that the influx of electrons associated with the PPO phase at 90° is responsible at least in part for the behavior of all H3+ parameters. A combination of the H3+ production and loss timescales and the ±10° uncertainty in the location of a given PPO phase are likely, at least in part, to be responsible for the observed peaks in H3+ density and emission occurring at a later time than the peak precipitation expected at 90° PPO phase.

  13. Improved orbits of Saturn and Jupiter from the Cassini and Juno missions

    Science.gov (United States)

    Folkner, William M.; Jacobson, Robert Arthur; Jones, Dayton

    2015-08-01

    Since entering orbit about Saturn in 2004, radio tracking data of the Cassini spacecraft has provided accurate measurements of its position leading to marked improvement in the Saturn ephemeris. The Cassini spacecraft orbit period has varied between 14 and 30 days as the orbit was changed to provide views of Saturn’s rings and satellites. This relatively large orbit period has required care to separate the spacecraft orbit relative to Saturn from the orbit of Saturn relative to the Sun. The resulting estimates give a series of range measurements of Saturn relative to Earth with accuracy of ~30 m. In addition to improving the Saturn ephemeris, the range measurements have been used to place stringent upper bounds on possible deviation from General Relativity suggested by the theory of Modified Newtonian Dynamics. The Very Large Baseline Array has been used to observe Cassini and determine the right ascension and declination of Saturn approximately every year since entering orbit. The combination of range and VLBA measurements over more than one-quarter of the Saturn orbit period have resulted in Saturn ephemeris accuracy comparable to that of the inner planets.The Juno spacecraft will enter orbit about Jupiter in July 2016. Juno will be the second spacecraft to orbit Jupiter, but the first to provide a time series of ranging measurements since the Galileo spacecraft high-gain antenna failure prevented range measurements from that mission. Ranging measurements to Juno, combined with VLBA observations, will cover less than one-quarter of an orbit period. But, when combined with the accurate measurements of the Ulysses spacecraft during Jupiter flyby in February 1992, the Jupiter ephemeris accuracy is expected to be close to that of Saturn and the inner planets.

  14. IMF dependence of the open-closed field line boundary in Saturn's ionosphere, and its relation to the UV auroral oval observed by the Hubble Space Telescope

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2007-06-01

    Full Text Available We study the dependence of Saturn's magnetospheric magnetic field structure on the interplanetary magnetic field (IMF, together with the corresponding variations of the open-closed field line boundary in the ionosphere. Specifically we investigate the interval from 8 to 30 January 2004, when UV images of Saturn's southern aurora were obtained by the Hubble Space Telescope (HST, and simultaneous interplanetary measurements were provided by the Cassini spacecraft located near the ecliptic ~0.2 AU upstream of Saturn and ~0.5 AU off the planet-Sun line towards dawn. Using the paraboloid model of Saturn's magnetosphere, we calculate the magnetospheric magnetic field structure for several values of the IMF vector representative of interplanetary compression regions. Variations in the magnetic structure lead to different shapes and areas of the open field line region in the ionosphere. Comparison with the HST auroral images shows that the area of the computed open flux region is generally comparable to that enclosed by the auroral oval, and sometimes agrees in detail with its poleward boundary, though more typically being displaced by a few degrees in the tailward direction.

  15. Analysis of plasma waves observed in the inner Saturn magnetosphere

    Directory of Open Access Journals (Sweden)

    J. D. Menietti

    2008-09-01

    Full Text Available Plasma waves observed in the Saturn magnetosphere provide an indication of the plasma population present in the rotationally dominated inner magnetosphere. Electrostatic cyclotron emissions often with harmonics and whistler mode emission are a common feature of Saturn's inner magnetosphere. The electron observations for a region near 5 RS outside and near a plasma injection region indicate a cooler low-energy (<100 eV, nearly isotropic plasma, and a much warmer (E>1000 eV more pancake or butterfly distribution. We model the electron plasma distributions to conduct a linear dispersion analysis of the wave modes. The results suggest that the electrostatic electron cyclotron emissions can be generated by phase space density gradients associated with a loss cone that may be up to 20° wide. This loss cone is sometimes, but not always, observed because the field of view of the electron detectors does not include the magnetic field line at the time of the observations. The whistler mode emission can be generated by the pancake-like distribution and temperature anisotropy (T/T||>1 of the warmer plasma population.

  16. Probing Saturn's tropospheric cloud with Cassini/VIMS

    CERN Document Server

    Barstow, Joanna K; Fletcher, Leigh N; Giles, Rohini S; Merlet, Cecile

    2016-01-01

    In its decade of operation the Cassini mission has allowed us to look deep into Saturn's atmosphere and investigate the processes occurring below its enshrouding haze. We use Visual and Infrared Mapping Spectrometer (VIMS) 4.6-5.2 micron data from early in the mission to investigate the location and properties of Saturn's cloud structure between 0.6 and 5 bars. We average nightside spectra from 2006 over latitude circles and model the spectral limb darkening using the NEMESIS radiative transfer and retrieval tool. We present our best-fit deep cloud model for latitudes between -40 and 50 degrees, along with retrieved abundances for NH3, PH3 and AsH3. We find an increase in NH3 abundance at the equator, a cloud base at ~2.3 bar and no evidence for cloud particles with strong absorption features in the 4.6-5.2 micron wavelength range, all of which are consistent with previous work. Non-scattering cloud models assuming a composition of either NH3 or NH4SH, with a scattering haze overlying, fit limb darkening curv...

  17. DSMC Shock Simulation of Saturn Entry Probe Conditions

    Science.gov (United States)

    Higdon, Kyle J.; Cruden, Brett A.; Brandis, Aaron M.; Liechty, Derek S.; Goldstein, David B.; Varghese, Philip L.

    2016-01-01

    This work describes the direct simulation Monte Carlo (DSMC) investigation of Saturn entry probe scenarios and the influence of non-equilibrium phenomena on Saturn entry conditions. The DSMC simulations coincide with rarefied hypersonic shock tube experiments of a hydrogen-helium mixture performed in the Electric Arc Shock Tube (EAST) at the NASA Ames Research Center. The DSMC simulations are post-processed through the NEQAIR line-by-line radiation code to compare directly to the experimental results. Improved collision cross-sections, inelastic collision parameters, and reaction rates are determined for a high temperature DSMC simulation of a 7-species H2-He mixture and an electronic excitation model is implemented in the DSMC code. Simulation results for 27.8 and 27.4 km/s shock waves are obtained at 0.2 and 0.1 Torr, respectively, and compared to measured spectra in the VUV, UV, visible, and IR ranges. These results confirm the persistence of non-equilibrium for several centimeters behind the shock and the diffusion of atomic hydrogen upstream of the shock wave. Although the magnitude of the radiance did not match experiments and an ionization inductance period was not observed in the simulations, the discrepancies indicated where improvements are needed in the DSMC and NEQAIR models.

  18. Shock Radiation Tests for Saturn and Uranus Entry Probes

    Science.gov (United States)

    Cruden, Brett A.; Bogdanoff, David W.

    2014-01-01

    This paper describes a test series in the Electric Arc Shock Tube at NASA Ames Research Center with the objective of quantifying shock-layer radiative heating magnitudes for future probe entries into Saturn and Uranus atmospheres. Normal shock waves are measured in Hydrogen/Helium mixtures (89:11 by mole) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 km/s. No shock layer radiation is detected below 25 km/s, a finding consistent with predictions for Uranus entries. Between 25-30 km/s, radiance is quantified from the Vacuum Ultraviolet through Near Infrared, with focus on the Lyman-alpha and Balmer series lines of Hydrogen. Shock profiles are analyzed for electron number density and electronic state distribution. The shocks do not equilibrate over several cm, and distributions are demonstrated to be non-Boltzmann. Radiation data are compared to simulations of Decadal survey entries for Saturn and shown to be significantly lower than predicted with the Boltzmann radiation model.

  19. Particle dynamics in the central ringlet of Saturn's Encke gap

    CERN Document Server

    Sun, Kai-Lung; Spahn, Frank

    2015-01-01

    A kinky and clumpy ringlet shares orbit with the moon Pan in the center of the 320-km wide Encke gap in Saturn's rings (Porco et al., 2005). The ringlet is mainly composed of micron-sized particles (Showalter, 1991, Hedman et al., 2011), implying that these particles may be significantly perturbed by non-gravitational forces, which can limit their lifetimes. We establish a kinetic model considering the birth, evolution, and death of dust in the Encke central ringlet allowing to evaluate the ringlet optical depth. First, we investigate the generation of dust by micrometeorite impacts (the `impact-ejecta' process) on putative, yet undetected embedded moonlets. Taking into account the orbital evolution under the influence of the relevant perturbation forces, the dominant loss mechanisms are collisions with ring particles in the gap edges, the putative moonlets in the gap, or erosion by sputtering in Saturn's plasma environment. However, our results show that this impact-ejecta process alone can only sustain a ri...

  20. Variations of Saturn's radio rotation period measured at kilometer wavelengths

    Science.gov (United States)

    Galopeau, Patrick H. M.; Lecacheux, Alain

    2000-06-01

    The Unified Radio and Plasma Wave (URAP) experiment on the interplanetary spacecraft Ulysses is able to detect the Saturnian kilometric radiation (SKR) thanks to the high sensitivity of the receiver and in spite of the remoteness of the planet (8-13 AU). Our knowledge about Saturn comes essentially from the observations by the two Voyager spacecraft. Ulysses allows us to reassess the main properties of the SKR as they had been observed by Voyager 1 and 2: average flux density, spectrum, periodicity, and polarization. A striking difference between the results obtained from Voyager and those obtained from Ulysses is the periodicity of the radio emission linked to the planetary rotation (10 hours 39 min 24 s): The period deduced from Ulysses' observations is not constant and may differ by 1% from that of Voyager. The northern and southern sources of SKR are distributed along magnetic field lines which are fixed in local time. We interpret the source location by a Kelvin-Helmholtz instability developing on the flanks of Saturn's magnetopause, in the morningside. This instability could be at the origin of the acceleration of the particles responsible for the radio emission. Because of the solar wind fluctuations, the position of the magnetopause and the magnetohydrodynamic flow around it are modified so that the zone of Kelvin-Helmholtz instability slowly moves, implying a drift of the radio sources in local time. We examine and discuss the possibility for this drift to be the cause of the variations observed for the SKR period.

  1. New observational constraints on hydrocarbon chemistry in Saturn's upper atmosphere

    Science.gov (United States)

    Koskinen, Tommi; Moses, Julianne I.; West, Robert; Guerlet, Sandrine; Jouchoux, Alain

    2016-10-01

    Until now there have been only a few observations of hydrocarbons and photochemical haze in the region where they are produced in Saturn's upper atmosphere. We present new results on hydrocarbon abundances and atmospheric structure based on more than 40 stellar occultations observed by the Cassini/UVIS instrument that we have combined with results from Cassini/CIRS to generate full atmosphere structure models. In addition to detecting CH4, C2H2, C2H4 and C2H6, we detect benzene (C6H6) in UVIS occultations that probe different latitudes and present the first vertical abundance profiles for this species in its production region. Benzene is the simplest ring polyaromatic hydrocarbon (PAH) and a stepping stone to the formation of more complex molecules that are believed to form stratospheric haze. Our calculations show that the observed abundances of benzene can be explained by solar-driven ion chemistry that is enhanced by high-latitude auroral production at least in the northern spring hemisphere. Condensation of benzene and heavier hydrocarbons is possible in the cold polar night of the southern winter where we detect evidence for high altitude haze. We also report on substantial variability in the CH4 profiles that arise from dynamics and affects the minor hydrocarbon abundances. Our results demonstrate the importance of hydrocarbon ion chemistry and coupled models of chemistry and dynamics for future studies of Saturn's upper atmosphere.

  2. Fates of satellite ejecta in the Saturn system, II

    Science.gov (United States)

    Alvarellos, José Luis; Dobrovolskis, Anthony R.; Zahnle, Kevin J.; Hamill, Patrick; Dones, Luke; Robbins, Stuart

    2017-03-01

    We assess the fates of ejecta from the large craters Aeneas on Dione and Ali Baba on Enceladus (161 and 39 km in diameter, respectively), as well as that from Herschel (130 km in diameter) on Mimas. The ejecta are treated either as 'spalls' launched from hard surfaces, or as 'rubble' launched from a weak rubble pile regolith. Once in orbit we consider the ejecta as massless test particles subject to the gravity of Saturn and its classical satellites. The great majority of escaped ejecta get swept up by the source moons. The best fit to the ejecta population decay is a stretched exponential with exponent near 1/2 (Dobrovolskis et al., Icarus 188, 481-505, 2007). We bracket the characteristic ejecta sizes corresponding to Grady-Kipp fragments and spalls. Based on this and computed impact velocities and incidence angles, the resulting sesquinary craters, if they exist, should have diameters on the order of a few meters to a few km. The observed longitude distribution of small craters on Mimas along with the findings of Bierhaus et al. that small moons should not have a secondary crater population (Icarus 218, 602-621, 2012) suggest that the most likely place to find sesquinary craters in the Saturn system is the antapex of Mimas.

  3. Metric Observations of Saturn with the Giant Metrewave Radio Telescope

    Science.gov (United States)

    Courtin, R.; Pandey-Pommier, M.; Gautier, D.; Zarka, P.; Hofstadter, M.; Hersant, F.; Girard, J.

    2015-12-01

    We used the Giant Metrewave Radio Telescope (GMRT, India) to observe Saturn in the metric domain – at 0.49 m (610 MHz), 1.28 m (235 MHz), and 2.0 m (150 MHz) -with the aim of constraining the deep atmospheric ammonia and water vapor concentrations around 10-20 kbar. We have obtained a clean detection at 610 MHz, with a disk brightness temperature Tb= 216 ± 32 K, and no significant emission outside of the disk, thus confirming model predictions about the weakness of synchrotron radiation by magnetospheric electrons (Lorenzato et al. 2012, Lorenzato et al. 2012). A marginal detection was obtained at 235 MHz, with Tb= 404 ± 249 K, while an upper limit of 1210 K was set at 150 MHz. Unfortunately, some of the GMRT measurements were affected by strong ionospheric scintillation or radio frequency interferences (RFI). Although the reduction of the LOFAR measurements is much more complex, results are expected in the near future and they will complement nicely with those obtained with the GMRT. We will discuss the constraints resulting from these observations on Saturn's deep atmospheric composition.

  4. The Great Saturn Storm of 2010-2011

    CERN Document Server

    Sánchez-Lavega, Agustín; Fletcher, Leigh N; García-Melendo, Enrique; Hesman, Brigette; Pérez-Hoyos, Santiago; Sayanagi, Kunio M; Sromovsky, Lawrence A

    2016-01-01

    In December 2010, a major storm erupted in Saturn's northern hemisphere near 37 degree planetographic latitude. This rather surprising event, occurring at an unexpected latitude and time, is the sixth "Great White Spot" (GWS) storm observed over the last century and a half. Such GWS events are planetary-scale atmospheric phenomena that dramatically change the typically bland appearance of the planet. Occurring while the Cassini mission was on-orbit at Saturn, the Great Storm of 2010-2011 was well-suited for intense scrutiny by the suite of sophisticated instruments onboard the Cassini spacecraft as well by modern instrumentation on ground-based telescopes and onboard the Hubble Space Telescope. This GWS erupted on December 5th and generated a major dynamical disturbance that affected the whole latitude band from 25 deg to 48 deg N. Lightning events were prominent and detected as outbursts and flashes at both optical and radio wavelengths. The activity of the head ceased after about seven months, leaving the c...

  5. Saturn's aurora observed by the Cassini camera at visible wavelengths

    CERN Document Server

    Dyudina, Ulyana A; Ewald, Shawn P; Wellington, Danika

    2015-01-01

    The first observations of Saturn's visible-wavelength aurora were made by the Cassini camera. The aurora was observed between 2006 and 2013 in the northern and southern hemispheres. The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon. The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs between 70 and 80 degree latitude north and between 65 and 80 degree latitude south, which sometimes spiral around the pole, and sometimes form double arcs. A large 10,000-km-scale longitudinal brightness structure persists for more than 100 hours. This structure rotates approximately together with Saturn. On top of the large steady structure, the auroras brighten suddenly on the timescales of a few minutes. These brightenings repeat with a period of about 1 hour....

  6. Statistical Eclipses of Close-in Kepler Sub-Saturns

    CERN Document Server

    Sheets, Holly A

    2014-01-01

    We present a method to detect small atmospheric signals in Kepler's planet candidate light curves by averaging light curves for multiple candidates with similar orbital and physical characteristics. Our statistical method allows us to measure unbiased physical properties of Kepler's planet candidates, even for candidates whose individual signal-to-noise precludes the detection of their secondary eclipse. We detect a secondary eclipse depth of 3.83 +1.10/-1.11 ppm for a group of 31 sub-Saturn (R 10 ppm). Including Kepler-10b in this group increases the depth to 5.08 +0.71/-0.72 ppm. For a control group with (R_p/a)^2 < 1 ppm, we find a depth of 0.36 +/- 0.37 ppm, consistent with no detection. We also analyze the light curve of Kepler-10b and find an eclipse depth of 7.08 +/- 1.06 ppm. If the eclipses are due solely to reflected light, this corresponds to a geometric albedo of 0.22 +/- 0.06 for our group of close-in sub-Saturns, 0.37 +/- 0.05 if including Kepler-10b in the group, and 0.60 +/- 0.09 for Keple...

  7. Local variability in the orbit of Saturn's F ring

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, N. J.; Murray, C. D.; Williams, G. A., E-mail: n.cooper@qmul.ac.uk [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

    2013-06-01

    We present an analysis of the orbit of Saturn's F ring using images recorded by the Imaging Science Subsystem of the Cassini spacecraft. A total of 9805 observations have been made from 10 image sequences obtained between 2006 November 23 and 2009 July 28. Each sequence of up to 240 images spans a single orbit of the F ring, allowing 10 independent high-precision estimates of the ring orbit to be made over this ∼3 year period. The ring has been modeled as an inclined uniformly precessing ellipse. The results show a variability in the orbital elements with, for example, the semi-major axis scattered between 140211.2 ± 0.1 km and 140232.9 ± 0.4 km and the fitted periapses locked to the value obtained from a combined fit using the entire three-year span of observations. We show that the observed scatter between the individual estimates of the ring orbit reflect the differing past histories of the particular segments of ring being fitted and that the values are scattered within the limits expected from a single gravitational encounter with the nearby moon, Prometheus. In the combined fit, the scatter averages out to reveal a small systematic bias with respect to the results of Bosh et al. and Albers et al. We believe this is a consequence of the proximity of Prometheus to the ring in the image sequences chosen for this analysis. Finally, we note a close empirical commensurability between the apsidal precession rate, ϖ-dot , of the F ring and the synodic period between Prometheus and the F ring, such that n {sub Prom} – n {sub Fring} ≈ 2 ϖ-dot {sub Fring}, where n {sub Prom} and n {sub Fring} are the mean motions, and discuss its implications.

  8. Ion Acceleration at Earth, Saturn and Jupiter and its Global Impact on Magnetospheric Structure

    Science.gov (United States)

    Brandt, Pontus

    2016-07-01

    The ion plasma pressures at Earth, Saturn and Jupiter are significant players in the electrodynamic force-balance that governs the structure and dynamics of these magnetospheres. There are many similarities between the physical mechanisms that are thought to heat the ion plasma to temperatures that even exceed those of the solar corona. In this presentation we compare the ion acceleration mechanisms at the three planetary magnetospheres and discuss their global impacts on magnetopsheric structure. At Earth, bursty-bulk flows, or "bubbles", have been shown to accelerate protons and O+ to high energies by the earthward moving magnetic dipolarization fronts. O+ ions display a more non-adiabatic energization in response to these fronts than protons do as they are energized and transported in to the ring-current region where they reach energies of several 100's keV. We present both in-situ measurements from the NASA Van Allen Probes Mission and global Energetic Neutral (ENA) images from the High-Energy Neutral Atom (HENA) Camera on board the IMAGE Mission, that illustrate these processes. The global impact on the magnetospheric structure is explored by comparing the empirical magnetic field model TS07d for given driving conditions with global plasma pressure distributions derived from the HENA images. At Saturn, quasi-periodic energization events, or large-scale injections, occur beyond about 9 RS around the post-midnight sector, clearly shown by the Ion and Neutral Atom Camera (INCA) on board the Cassini mission. In contrast to Earth, the corotational drift dominates even the energetic ion distributions. The large-scale injections display similar dipolarization front features can be found and there are indications that like at Earth the O+ responds more non-adiabatically than protons do. However, at Saturn there are also differences in that there appears to be energization events deep in the inner magnetosphere (6-9 RS) preferentially occurring in the pre

  9. Cloud and Wind Variability in Saturn's Equatorial Jet prior to the Cassini orbital tour

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.; Hueso, R.; Rojas, J. F.; French, R. G.

    2004-11-01

    We use ground-based observations (going back to 1876), Pioneer-11 data (1979), Voyager 1 and 2 encounter images in 1980 and 1981, and HST 1990-2004 images, to study the changes that occurred in the vertical cloud structure and morphology and motions, in Saturn's Equatorial Region (approximately the band between latitudes 40 deg North and South). We compare ``calm periods" with ``stormy periods" i. e. those that occur during the development of the phenomenon known as the ``Great White Spots." We discuss different interpretations of the mechanisms that can be involved in the observed changes: vertical wind shears, waves, storm - mean flow interaction and changes in atmospheric angular momentum. Acknowledgements: This work was supported by the Spanish MCYT AYA 2003-03216. SPH acknowledges a PhD fellowship from the Spanish MECD and RH a post-doc fellowship from Gobierno Vasco. RGF was supported in part by NASA's Planetary Geology and Geophysics Program NAG5-10197 and STSCI Grant GO-08660.01A.

  10. How Janus' Orbital Swap Affects the Edge of Saturn's A Ring?

    CERN Document Server

    Moutamid, Maryame El; French, Richard G; Tiscareno, Matthew S; Murray, Carl D; Evans, Michael W; French, Colleen McGhee; Hedman, Matthew M; Burns, Joseph A

    2015-01-01

    We present a study of the behavior of Saturn's A ring outer edge, using images and occultation data obtained by the Cassini spacecraft over a period of 8 years from 2006 to 2014. More than 5000 images and 170 occultations of the A ring outer edge are analyzed. Our fits confirm the expected response to the Janus 7:6 Inner Lindblad resonance (ILR) between 2006 and 2010, when Janus was on the inner leg of its regular orbit swap with Epimetheus. During this period, the edge exhibits a regular 7-lobed pattern with an amplitude of 12.8 km and one minimum aligned with the orbital longitude of Janus, as has been found by previous investigators. However, between 2010 and 2014, the Janus/Epimetheus orbit swap moves the Janus 7:6 LR away from the A ring outer edge, and the 7-lobed pattern disappears. In addition to several smaller-amplitudes modes, indeed, we found a variety of pattern speeds with different azimuthal wave numbers, and many of them may arise from resonant cavities between the ILR and the ring edge; also ...

  11. Measurements of C02 Distribution in Saturn's Atmosphere by Cassini-Infrared Observations

    Science.gov (United States)

    Abbas, M. M.; LeClair, A.; Woodard, E.; Young, M.; Stanbro, M.; Flasar, M.

    2013-01-01

    The Fourier transform infrared spectrometer aboard the Cassini spacecraft, inserted in Saturn s orbit in July 2004, has been providing high resolution/high sensitivity infrared (IR) spectra of the Saturnian system. The measurements cover the spectral range of 10-1400/cm with variable spectral resolutions of 0.53 to 15/cm, exhibiting spectral features of a series of trace gases including CO2 and H2O. The observed spectra may be analyzed for retrieval of global P/T and gas density profiles of Saturn. The infrared measurements of Saturn by ISO(SWS) have indicated unexpected large abundances of CO2 in Saturn's atmosphere. The rigorous photochemical models of Saturn's atmosphere that have been developed indicate exogenic oxygen influx of icy dust grains that lead to the production of CO2. The distribution of CO2 in Saturn's atmosphere needs to be confirmed, and the nature of exogenic sources remains to be investigated. This paper presents comprehensive measurements of the CO2 distribution in Saturn's atmosphere by Cassini IR observations.

  12. Saturn's magnetospheric rotation after equinox and a possible influence by the Great White Spot

    Science.gov (United States)

    Fischer, G.; Gurnett, D. A.; Ye, S.-Y.; Groene, J. B.; Ingersoll, A. P.; Sayanagi, K. M.; Menietti, J. D.; Kurth, W. S.

    2013-09-01

    In this presentation we will show the rotational modulation of Saturn kilometric radiation (SKR) and Saturn narrowband emissions after equinox until early 2013. The rotation period of Saturn's magnetosphere was found to vary with time [1], and changing periodicities were identified in magnetic fields, radio emissions, and charged particles [2,3]. SKR acts as a good tracer of this rotation since these radio emissions have been observed almost permanently by the Cassini Radio and Plasma Wave Science (RPWS) instrument [4] in recent years. The SKR period temporarily slowed down by ~0.5% from the end of 2010 until August 2011, when it shows a large discontinuity and jumps back to its previous period. This time interval of unusual SKR behavior exactly coincides with the occurrence of the so-called Great White Spot (GWS), a giant thunderstorm that raged in Saturn's northern hemisphere [5]. For several months in 2011, the visible head of the GWS had the same period of ~10.69 h as the SKR. We suggest that there is a relation and that Saturn's magnetospheric periodicities are driven by the upper atmosphere [6]. The GWS was most likely a source of intense gravity waves that caused a global change in Saturn's thermospheric temperatures and winds. Gravity waves can propagate to high altitudes and produce significant drag on the mean zonal wind [7]. The resulting deceleration might have slowed down the SKR and the hypothetical ionospheric vortices, which, according to some models [8], are driving Saturn's magnetospheric periodicities.

  13. INTERIOR MODELS OF SATURN: INCLUDING THE UNCERTAINTIES IN SHAPE AND ROTATION

    Energy Technology Data Exchange (ETDEWEB)

    Helled, Ravit [Department of Geophysics, Atmospheric and Planetary Sciences, Tel-Aviv University, Tel-Aviv (Israel); Guillot, Tristan [Universite de Nice-Sophia Antipolis, Observatoire de la Cote d' Azur, CNRS UMR 7293, BP 4229, F-06304 Nice (France)

    2013-04-20

    The accurate determination of Saturn's gravitational coefficients by Cassini could provide tighter constraints on Saturn's internal structure. Also, occultation measurements provide important information on the planetary shape which is often not considered in structure models. In this paper we explore how wind velocities and internal rotation affect the planetary shape and the constraints on Saturn's interior. We show that within the geodetic approach the derived physical shape is insensitive to the assumed deep rotation. Saturn's re-derived equatorial and polar radii at 100 mbar are found to be 54,445 {+-} 10 km and 60,365 {+-} 10 km, respectively. To determine Saturn's interior, we use one-dimensional three-layer hydrostatic structure models and present two approaches to include the constraints on the shape. These approaches, however, result in only small differences in Saturn's derived composition. The uncertainty in Saturn's rotation period is more significant: with Voyager's 10{sup h}39{sup m} period, the derived mass of heavy elements in the envelope is 0-7 M{sub Circled-Plus }. With a rotation period of 10{sup h}32{sup m}, this value becomes <4 M{sub Circled-Plus }, below the minimum mass inferred from spectroscopic measurements. Saturn's core mass is found to depend strongly on the pressure at which helium phase separation occurs, and is estimated to be 5-20 M{sub Circled-Plus }. Lower core masses are possible if the separation occurs deeper than 4 Mbar. We suggest that the analysis of Cassini's radio occultation measurements is crucial to test shape models and could lead to constraints on Saturn's rotation profile and departures from hydrostatic equilibrium.

  14. SPRITE - The Saturn PRobe Interior and aTmosphere Explorer Mission.

    Science.gov (United States)

    Atkinson, D. H.; Simon, A. A.; Banfield, D. J.; Atreya, S. K.; Blacksberg, J.; Brinckerhoff, W. B.; Colaprete, A.; Coustenis, A.; Danner, R. M.; Fletcher, L. N.; Guillot, T.; Hofstadter, M. D.; Keithly, D.; Lobbia, M. A.; Lunine, J. I.; Mahaffy, P. R.; Marley, M. S.; Mousis, O.; Spilker, T. R.; Trainer, M. G.; Webster, C. R.; Youmans, T. A.

    2016-12-01

    The 2013-2022 Planetary Science Decadal Survey (PSDS) Vision and Voyages Planetary identified a Saturn Probe mission as a high priority mission target for the NASA New Frontiers program. Fundamental measurements of noble gas abundances and isotope ratios of hydrogen, carbon, oxygen, and nitrogen, as well as the interior structure of Saturn are needed to help constrain Solar System formation models and to provide an improved context for understanding exoplanet systems. The SPRITE mission would fulfill the PSDS scientific goals for in situ exploration of Saturn, and would additionally provide ground truth for remote sensing that would improve the understanding of the composition and interior structure of Saturn and, by proxy, extrasolar giant planets. In Situ measurements are the only means to address many key questions regarding the structure and composition of Saturn's atmosphere including the abundance of noble gases and key isotopes, the abundance of helium needed to understand the formation history and thermal evolution of Saturn, and the abundance of water in the deep atmosphere, a key diagnostic of Saturn's formation since it is thought that the heavy elements were delivered by water-bearing planetesimals. The SPRITE atmospheric entry probe mission including remote sensing from a carrier-relay spacecraft would measure many of these key atmospheric constituents as well as the atmospheric structure of Saturn including temperature, pressure and wind speeds along the probe descent path thereby providing interior science not accessible to remote sensing measurements. Additionally, the SPRITE carrier-relay spacecraft would make remote sensing measurements to support probe measurements in the upper troposphere of Saturn.

  15. Infrared Observations Of Saturn's Rings : Azimuthal Variations And Thermal Modeling

    Science.gov (United States)

    Leyrat, C.; Spilker, L. J.; Altobelli, N.; Pilorz, S.; Ferrari, C.; Edgington, S. G.; Wallis, B. D.; Nugent, C.; Flasar, M.

    2007-12-01

    Saturn's rings represent a collection of icy centimeter to meter size particles with their local dynamic dictated by self gravity, mutual collisions, surface roughness and thickness of the rings themselves. The infrared observations obtained by the CIRS infrared spectrometer on board Cassini over the last 3.5 year contain informations on the local dynamic, as the thermal signature of planetary rings is influenced both by the ring structure and the particle properties. The ring temperature is very dependent on the solar phase angle (Spilker et al., this issue), and on the local hour angle around Saturn, depending on whether or not particles' visible hemispheres are heated by the Sun. The geometric filling factor, which can be estimated from CIRS spectra, is less dependent on the local hour angle, suggesting that the non isothermal behavior of particles' surfaces have low impact, but it is very dependent on the spacecraft elevation for the A and C rings. The ring small scale structure can be explored using CIRS data. Variations of the filling factor with the local hour angle relative to the spacecraft azimuth reveals self-gravity wakes. We derive morphological parameters of such wakes in both A and B rings assuming that wakes can be modeled either by regularly spaced bars with infinite or finite optical depth. Our results indicates that wakes in the A ring are almost flat, with a ratio height/width ≈ 0.44 ± 0.16 and with a pitch angle relative to the orbital motion direction of ≍ 27deg. This is consistent with UVIS (Colwell et al., 2006) and VIMS data (Hedman et al., 2007). Such models are more difficult to constrain in the B ring, but small variations of the filling factor indicate that the pitch angle decreases drastically in this ring. We also present a new thermal bar model to explain azimuthal variations of temperatures in the A ring. We compare results with previous ring thermal models of spherical particles. The Cassini/CIRS azimuthal scans data set is

  16. Statistical eclipses of close-in Kepler sub-Saturns

    Energy Technology Data Exchange (ETDEWEB)

    Sheets, Holly A.; Deming, Drake, E-mail: hsheets@astro.umd.edu [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States)

    2014-10-20

    We present a method to detect small atmospheric signals in Kepler's planet candidate light curves by averaging light curves for multiple candidates with similar orbital and physical characteristics. Our statistical method allows us to measure unbiased physical properties of Kepler's planet candidates, even for candidates whose individual signal-to-noise precludes the detection of their secondary eclipse. We detect a secondary eclipse depth of 3.83{sub −1.11}{sup +1.10} ppm for a group of 31 sub-Saturn (R < 6 R {sub ⊕}) planet candidates with the greatest potential for a reflected light signature ((R{sub p} /a){sup 2} > 10 ppm). Including Kepler-10b in this group increases the depth to 5.08{sub −0.72}{sup +0.71} ppm. For a control group with (R{sub p} /a){sup 2} < 1 ppm, we find a depth of 0.36 ± 0.37 ppm, consistent with no detection. We also analyze the light curve of Kepler-10b and find an eclipse depth of 7.08 ± 1.06 ppm. If the eclipses are due solely to reflected light, this corresponds to a geometric albedo of 0.22 ± 0.06 for our group of close-in sub-Saturns, 0.37 ± 0.05 if including Kepler-10b in the group, and 0.60 ± 0.09 for Kepler-10b alone. Including a thermal emission model does not change the geometric albedo appreciably, assuming A{sub B} = (3/2)*A{sub g} . Our result for Kepler-10b is consistent with previous works. Our result for close-in sub-Saturns shows that Kepler-10b is unusually reflective, but our analysis is consistent with the results of Demory for super-Earths. Our results also indicate that hot Neptunes are typically more reflective than hot Jupiters.

  17. Saturn's polar ionospheric flows and their relation to the main auroral oval

    Directory of Open Access Journals (Sweden)

    S. W. H. Cowley

    2004-04-01

    upward current bounding the region of open and closed field lines. Estimates indicate that auroras of brightness from a few kR to a few tens of kR can be produced by precipitating accelerated magnetospheric electrons of a few keV to a few tens of keV energy, if the current flows in a region which is sufficiently narrow, of the order of or less than ~1000 km (~1° latitude wide. Arguments are also given which indicate that the auroras should typically be significantly brighter on the dawn side of the oval than at dusk, by roughly an order of magnitude, and should be displaced somewhat towards dawn by the down-tail outflow at dusk associated with the Vasyliunas cycle. Model estimates are found to be in good agreement with data derived from high quality images newly obtained using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope, both in regard to physical parameters, as well as local time effects. The implication of this picture is that the form, position, and brightness of Saturn's main auroral oval provide remote diagnostics of the magnetospheric interaction with the solar wind, including dynamics associated with magnetopause and tail plasma interaction processes.

    Key words. Magnetospheric physics (auroral phenomena, magnetosphere-ionosphere interactions, solar windmagnetosphere interactions

  18. Scheme of Saturn rings origination and nature of the Cassini's division

    Energy Technology Data Exchange (ETDEWEB)

    Davydov, V.D.

    The united solution of two problems: the problem of Cassini division width and the problem of the former Saturn satellite plunging into the tidal destruction zone is suggested on the base of the analysis of observed properties of the Saturn rings. The scheme of the ring system formation is built up; the concrete characteristics of the former satellite from which this system has been formed are found out. The literature data on the Saturn rings observation from the ''Voyadger-1'', ''Voyadger-2'' space probes are used in the paper.

  19. Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing

    Energy Technology Data Exchange (ETDEWEB)

    Gaudi, B; Bennett, D; Udalski, A; Gould, A; Christie, G; Maoz, D; Dong, S; McCormick, J; Szymanski, M; Tristram, P; Nikolaev, S; Paczynski, B; Kubiak, M; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; DePoy, D; Han, C; Kaspi, S; Lee, C; Mallia, F; Natusch, T; Pogge, R; Park, B; Abe, F; Bond, I; Botzler, C; Fukui, A; Hearnshaw, J; Itow, Y; Kamiya, K; Korpela, A; Kilmartin, P; Lin, W; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Okumura, T; Ohnishi, K; Rattenbury, N; Sako, T; Saito, T; Sato, S; Skuljan, L; Sullivan, D; Sumi, T; Sweatman, W; Yock, P; Albrow, M; Beaulieu, J; Burgdorf, M; Cook, K; Coutures, C; Dominik, M; Dieters, S; Fouque, P; Greenhill, J; Horne, K; Steele, I; Tsapras, Y; Chaboyer, B; Crocker, A; Frank, S; Macintosh, B

    2007-11-08

    Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the first detection of a multiple-planet system with microlensing. We identify two planets with masses of {approx} 0.71 and {approx} 0.27 times the mass of Jupiter and orbital separations of {approx} 2.3 and {approx} 4.6 astronomical units orbiting a primary of mass {approx} 0.50 solar masses. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only 6 confirmed microlensing planet detections suggests that solar system analogs may be common.

  20. The influence of Titan on Saturn kilometric radiation

    Directory of Open Access Journals (Sweden)

    J. D. Menietti

    2010-02-01

    Full Text Available Previous studies have shown that the occurrence probability of Saturn Kilometric Radiation (SKR appears to be influenced by the local time of Titan. Using a more extensive set of data than the original study, we confirm the correlation of higher occurrence probability of SKR when Titan is located near local midnight. In addition, the direction finding capability of the Cassini Radio Plasma Wave instrument (RPWS is used to determine if this radio emission emanates from particular source regions. We find that most source regions of SKR are located in the mid-morning sector of local time even when Titan is located near midnight. However, some emission does appear to have a source in the Saturnian nightside, consistent with electron precipitation from field lines that have recently mapped to near Titan.

  1. Saturn's Seasonally Changing Atmosphere: Thermal Structure, Composition and Aerosols

    CERN Document Server

    Fletcher, Leigh N; Moses, Julianne I; Guerlet, Sandrine; West, Robert A

    2015-01-01

    The longevity of Cassini's exploration of Saturn's atmosphere (a third of a Saturnian year) means that we have been able to track the seasonal evolution of atmospheric temperatures, chemistry and cloud opacity over almost every season, from solstice to solstice and from perihelion to aphelion. Cassini has built upon the decades-long ground-based record to observe seasonal shifts in atmospheric temperature, finding a thermal response that lags behind the seasonal insolation with a lag time that increases with depth into the atmosphere, in agreement with radiative climate models. Seasonal hemispheric contrasts are perturbed at smaller scales by atmospheric circulation, such as belt/zone dynamics, the equatorial oscillations and the polar vortices. Temperature asymmetries are largest in the middle stratosphere and become insignificant near the radiative-convective boundary. Cassini has also measured southern-summertime asymmetries in atmospheric composition, including ammonia (the key species for the topmost clo...

  2. Analysis of Electric Propulsion System for Exploration of Saturn

    Directory of Open Access Journals (Sweden)

    Carlos Renato Huaura Solórzano

    2009-01-01

    Full Text Available Exploration of the outer planets has experienced new interest with the launch of the Cassini and the New Horizons Missions. At the present time, new technologies are under study for the better use of electric propulsion system in deep space missions. In the present paper, the method of the transporting trajectory is used to study this problem. This approximated method for the flight optimization with power-limited low thrust is based on the linearization of the motion of a spacecraft near a keplerian orbit that is close to the transfer trajectory. With the goal of maximizing the mass to be delivered in Saturn, several transfers were studied using nuclear, radioisotopic and solar electric propulsion systems.

  3. Could Jupiter or Saturn Have Ejected a Fifth Giant Planet?

    CERN Document Server

    Cloutier, Ryan; Valencia, Diana

    2015-01-01

    Models of the dynamical evolution of the early solar system following the dispersal of the gaseous protoplanetary disk have been widely successful in reconstructing the current orbital configuration of the giant planets. Statistically, some of the most successful dynamical evolution simulations have initially included a hypothetical fifth giant planet, of ice giant mass, which gets ejected by a gas giant during the early solar system's proposed instability phase. We investigate the likelihood of an ice giant ejection event by either Jupiter or Saturn through constraints imposed by the current orbits of their wide-separation regular satellites Callisto and Iapetus respectively. We show that planetary encounters that are sufficient to eject an ice giant, often provide excessive perturbations to the orbits of Callisto and Iapetus making it difficult to reconcile a planet ejection event with the current orbit of either satellite. Quantitatively, we compute the likelihood of reconciling a regular Jovian satellite ...

  4. Ion cyclotron harmonics in the Saturn downward current auroral region

    Science.gov (United States)

    Menietti, J. D.; Schippers, P.; Santolík, O.; Gurnett, D. A.; Crary, F.; Coates, A. J.

    2011-12-01

    Observations of intense upgoing electron beams and diffuse ion beams have been reported during a pass by Cassini in a downward current auroral region, nearby a source region of Saturn kilometric radiation. Using the Cassini Radio and Plasma Wave Science (RPWS) instrument low frequency waveform receiver and the Cassini Plasma Spectrometer Investigation (CAPS) instrument we have been able to identify ion cyclotron harmonic waves associated with the particle beams. These observations indicate similarities with terrestrial auroral emissions, and may be a source of wave-particle interactions. We fit the observed plasma electron distribution with drifting Maxwellians and perform a linear numerical analysis of plasma wave growth. The results are relevant to ion heating and possibly to electron acceleration.

  5. A model for the formation of spokes in Saturn's rings

    Science.gov (United States)

    Goertz, C. K.; Morfill, G.

    1983-01-01

    Evidence is mounting which implies that the generation, evolution, and motion of spokes require a dense plasma near the Saturn ring plane. It is presently suggested that spokes consist of charged, micron-sized dust particles which are elevated from the rings by radially moving, dense plasma columns due to meteor impacts on the ring. Electrostatic wall sheaths at the ring, and ring charging by electric fields sufficiently strong to overcome the gravitational force on small dust particles, arise from the dense plasma, which also increases the probability of dust particle excess electronic charge. The radial motion of the plasma column is due to an azimuthal polarization electric field due to the relative motion between the corotating plasma and the negatively charged dust particles moving at Keplerian speeds.

  6. RCM simulation of interchange transport in Saturn's inner magnetosphere

    Science.gov (United States)

    Hill, T. W.; Liu, X.; Sazykin, S. Y.; Wolf, R.

    2013-12-01

    Numerical simulations with the Rice Convection Model have been used to study the radial transport of plasma in Saturn's inner magnetosphere (L process is the pervasive presence of V-shaped injection/dispersion signatures in linear energy-time spectrograms that are observed by the Cassini Plasma Spectrometer (CAPS) on every pass through the inner magnetosphere. Using observed hot plasma distributions at L~12 as input, we have now successfully simulated these V-shaped signatures. We will show these simulation results and compare them with observed signatures. We will also describe future improvements to the model including relaxing the dipole-field assumption, thus enabling us to simulate local-time asymmetries imposed by the outer magnetosphere and tail.

  7. Empirical Models of Pressure and Density in Saturn's Interior: Implications for the Helium Concentration, its Depth Dependence, and Saturn's Precession Rate

    CERN Document Server

    Helled, Ravit; Anderson, John D

    2008-01-01

    We present 'empirical' models (pressure vs. density) of Saturn's interior constrained by the gravitational coefficients J_2, J_4, and J_6 for different assumed rotation rates of the planet. The empirical pressure-density profile is interpreted in terms of a hydrogen and helium physical equation of state to deduce the hydrogen to helium ratio in Saturn and to constrain the depth dependence of helium and heavy element abundances. The planet's internal structure (pressure vs. density) and composition are found to be insensitive to the assumed rotation rate for periods between 10h:32m:35s and 10h:41m:35s. We find that helium is depleted in the upper envelope, while in the high pressure region (P >~ 1 Mbar) either the helium abundance or the concentration of heavier elements is significantly enhanced. Taking the ratio of hydrogen to helium in Saturn to be solar, we find that the maximum mass of heavy elements in Saturn's interior ranges from ~ 6 to 20 M_Earth. The empirical models of Saturn's interior yield a mome...

  8. Auroral counterpart of magnetic field dipolarizations in Saturn's tail

    Science.gov (United States)

    Jackman, C. M.; Badman, S. V.; Achilleos, N.; Bunce, E. J.; Cowley, S. W. H.; Radioti, A.; Grodent, D.; Dougherty, M. K.; Pryor, W.

    2012-04-01

    Following magnetic reconnection in a planetary magnetotail, newly closed field lines can be rapidly accelerated back towards the planet, becoming "dipolarized" in the process. At Saturn, dipolarizations can be initially identified in magnetometer data by looking for a southward turning of the magnetic field, indicating the transition from a radially stretched configuration to a more dipolar field topology. The highly stretched geometry of the kronian magnetotail lobes gives rise to a tail current which flows eastward (dusk to dawn) in the near equatorial plane across the centre of the tail. During reconnection and associated dipolarization of the field, the inner edge of this tail current can be diverted through the ionosphere, in a situation analogous to the substorm current wedge picture at Earth. We present a picture of the current circuit arising from this tail reconfiguration, and outline the equations which govern the field-current relationship. We show an example of a dipolarization identified in the Cassini magnetometer data and use this formalism to constrain the ionospheric current density that would arise for this example and the implications for auroral electron acceleration in regions of upward directed field-aligned current. We then present a separate example of data from the Cassini UVIS instrument where we observe small 'spots' of auroral emission lying near the main oval; features thought to be associated with dipolarizations in the tail. In the example shown, such auroral spots are the precursor to more intense activity associated with recurrent energisation via particle injections from the tail following reconnection. We conclude that dipolarizations in Saturn's magnetotail have an observable auroral counterpart, opening up the possibility to search for further examples and to use this auroral property as a remote proxy for tail reconnection.

  9. A simple model for the location of Saturn's F ring

    Science.gov (United States)

    Benet, Luis; Jorba, Àngel

    2017-03-01

    In this paper, we introduce a simplified model to understand the location of Saturn's F ring. The model is a planar restricted five-body problem defined by the gravitational field of Saturn, including its second zonal harmonic J2, the shepherd moons Prometheus and Pandora, and Titan. We compute accurate long-time numerical integrations of (about 2.5 million) non-interacting test-particles initially located in the region between the orbits of Prometheus and Pandora, and address whether they escape or remain trapped in this region. We obtain a wide region of initial conditions of the test particles that remain confined. We consider a dynamical stability indicator for the test particles' motion defined by computing the ratio of the standard deviation over the average value of relevant dynamical quantities, in particular, for the mean-motion and the semi-major axis. This indicator separates clearly a subset of trapped initial conditions that appear as very localized stripes in the initial semi-major axis and eccentricity space for the most stable orbits. Retaining only these test particles, we obtain a narrow eccentric ring which displays sharp edges and collective alignment. The semi-major axis of the accumulation stripes of the stable ring-particles can be associated with resonances, mostly involving Prometheus' outer Lindblad and co-rotation resonances, but not exclusively. Pandora's inner Lindblad and co-rotation resonances as well as low-order three-body resonances typically coincide with gaps, i.e., regions of instabilities. Comparison of our results with the nominal data for the F ring shows some correspondence.

  10. Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements

    Science.gov (United States)

    Sittler, E.; Cooper, J.; Hartle, R.; Simpson, D.; Johnson, R.; Thomsen, M.; Arridge, C.

    2011-01-01

    We present the present status of an investigation of the rotation rate of Saturn's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. for SOI and similar to that used by Thomsen et al.. This technique allows one to nearly cover the full energy range of the Cassini Plasma Spectrometer (CAPS) IMS from 1 V . E/Q work during roll maneuvers. We make comparisons with the bi-Maxwellian fitting technique developed by Wilson et al. and the similar velocity moment technique by Thomsen et al. . We concentrate our analysis when ion composition data is available, which is used to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The chosen periods have high enough telemetry rates (4 kbps or higher) so that coincidence ion data, similar to that used by Sittler et al. for SOI is available. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. In the future we will then make comparisons with magnetic field observations, Saturn ionosphere conductivities as presently known and the field aligned currents necessary for the planet to enforce corotation of the rotating plasma.

  11. Modeling Saturn Ring Temperature Variations as Solar Elevation Decreases

    Science.gov (United States)

    Spilker, L.; Flandes, A.; Altobelli, N.; Leyrat, C.; Pilorz, S.; Ferrari, C.

    2008-12-01

    After more than four years in orbit around Saturn, the Cassini Composite Infrared Spectrometer (CIRS) has acquired a wide-ranging set of thermal measurements of Saturn's main rings (A, B, C and Cassini Division). Temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include solar phase angle, spacecraft elevation, solar elevation and local hour angle. To first order, the largest temperature changes on the lit face of the rings are driven by variations in phase angle while differences in temperature with changing spacecraft elevation and local time are a secondary effect. Decreasing ring temperature with decreasing solar elevation are observed for both the lit and unlit faces of the rings after phase angle and local time effects are taken into account. For the lit rings, decreases of 2- 4 K are observed in the C ring and larger decreases, 7-10 and 10 - 13 K, are observed in the A and B rings respectively. Our thermal data cover a range of solar elevations from -21 to -8 degrees (south side of the rings). We test two simple models and evaluate how well they fit the observed decreases in temperature. The first model assumes that the particles are so widely spaced that they do not cast shadows on one another while the second model assumes that the particles are so close together they essentially form a slab. The optically thinnest and optically thickest regions of the rings show the best fits to these two end member models. We also extrapolate to the expected minimum ring temperatures at equinox. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA and at CEA Saclay supported by the "Programme National de Planetologie". Copyright 2008 California Institute of Technology. Government sponsorship acknowledged.

  12. Investigating Fresh Hot Plasma Injections in Saturn's Inner-Magnetosphere

    Science.gov (United States)

    Vandegriff, J. D.; Loftus, K.; Rymer, A. M.; Mitchell, D. G.

    2015-12-01

    A decreasing density gradient in Saturn's plasma disk allows for centrifugal interchange instability between the dense, heavy plasma inside 10 Rs and the lighter plasma outside. This instability results in the less dense plasma of the mid-magnetosphere moving inward to the inner-magnetosphere. As flux tubes move inward, their volume decreases, and the contained plasma heats adiabatically. Most studies of interchange have focused on older events that have had time to gradient and curvature drift such that they are easily identified by a characteristic "V" energy dispersion signature in the ion and electron data [e.g. Hill et al., 2005; Chen et al., 2010]. Recently, Kennelly et al. (2013) used radio wave data to identify >300 possible "fresh" injection events. These are characterized in the plasma data by a bite-out at low energies, an enhancement at high energies, and little to no energy dispersion. Our study builds on the Kennelly et al. study to investigate the shape and frequency of injection events in order to better characterize how hot plasma transports into the inner magnetosphere. In most models of centrifugal interchange at Saturn, the time and spatial scales for inward and outward transport are fairly symmetric, but Cassini data suggests that inward injections of plasma move at much greater velocity and in narrower flow channels than their outgoing counterparts. Here we investigate the morphology of Kronian inward injection events to see if our dataset of young injections can inform on whether the inward injections are extended fingers or more like "bubbles", isolated flux tubes. Specifically, we apply minimum variance analysis to Cassini magnetic field data to determine the boundary normals at the spacecraft's entrance and exit points for each event, from which we can statistically analyze the structure's cross section. We will present our initial results on the morphology as well as the distribution of the injections over radial distance, latitude, and

  13. Multispectral simultaneous diagnosis of Saturn's aurorae throughout a planetary rotation

    Science.gov (United States)

    Lamy, L.; Prangé, R.; Pryor, W.; Gustin, J.; Badman, S. V.; Melin, H.; Stallard, T.; Mitchell, D.-G.; Brandt, P. C.

    2013-08-01

    From 27 to 28 January 2009, the Cassini spacecraft remotely acquired combined observations of Saturn's southern aurorae at radio, ultraviolet, and infrared wavelengths, while monitoring ion injections in the middle magnetosphere from energetic neutral atoms. Simultaneous measurements included the sampling of a full planetary rotation, a relevant timescale to investigate auroral emissions driven by processes internal to the magnetosphere. In addition, this interval coincidentally matched a powerful substorm-like event in the magnetotail, which induced an overall dawnside intensification of the magnetospheric and auroral activity. We comparatively analyze this unique set of measurements to reach a comprehensive view of kronian auroral processes over the investigated timescale. We identify three source regions for the atmospheric aurorae, including a main oval associated with the bulk of Saturn Kilometric Radiation (SKR), together with polar and equatorward emissions. These observations reveal the coexistence of corotational and subcorototational dynamics of emissions associated with the main auroral oval. Precisely, we show that the atmospheric main oval hosts short-lived subcorotating isolated features together with a bright, longitudinally extended, corotating region locked at the southern SKR phase. We assign the substorm-like event to a regular, internally driven, nightside ion injection possibly triggered by a plasmoid ejection. We also investigate the total auroral energy budget, from the power input to the atmosphere, characterized by precipitating electrons up to 20 keV, to its dissipation through the various radiating processes. Finally, through simulations, we confirm the search-light nature of the SKR rotational modulation and we show that SKR arcs relate to isolated auroral spots. We characterize which radio sources are visible from the spacecraft and we estimate the fraction of visible southern power to a few percent. The resulting findings are discussed

  14. Saturn kilometric radiation periodicity before and after equinox

    Science.gov (United States)

    Fischer, G.; Gurnett, D. A.; Kurth, W. S.; Ye, S.-Y.; Groene, J. B.

    2014-04-01

    The rotation period of Saturn's magnetosphere was found to vary with time, and changing periodicities were identified in magnetic fields [1], radio emissions [2], and charged particles [3]. In this presentation we show the varying period of Saturn kilometric radiation (SKR) from 2004 to early 2014, a time period of almost 10 years. From 2004 until early 2009 SKR had two periods, 10.8 h and 10.6 h, attributed to SKR radiated from the southern and northern hemisphere, respectively [4]. The periods converged during 2009 and show a complicated behavior afterwards which we will analyze in more detail. Our analysis is first applied to the complete SKR signal, and second to SKR intensities separated by spacecraft latitude and wave polarization, with right-handed SKR attributed to the northern hemisphere and lefthanded SKR to the southern hemisphere. We apply the so-called tracking filter analysis [5], and we will also simply follow the phases of normalized SKR intensity maxima (north and south) with time. Both analyses yield similar results. A comparison of SKR periodicities after equinox to the planetary period oscillations of the magnetic field [6] shows major differences, and we will try to explain the deviations. We also identify minor SKR components where the modulation phase deviation exceeds one rotation each time Cassini completes one orbit, i.e. this is consistent with the characteristic of a searchlight-like signal. However, the main SKR signal still acts like a clock with a modulation phase independent of the local time of the Cassini spacecraft.

  15. Effects of radial motion on interchange injections at Saturn

    Science.gov (United States)

    Paranicas, C.; Thomsen, M. F.; Achilleos, N.; Andriopoulou, M.; Badman, S. V.; Hospodarsky, G.; Jackman, C. M.; Jia, X.; Kennelly, T.; Khurana, K.; Kollmann, P.; Krupp, N.; Louarn, P.; Roussos, E.; Sergis, N.

    2016-01-01

    Charged particle injections are regularly observed in Saturn's inner magnetosphere by Cassini. They are attributed to an ongoing process of flux-tube interchange driven by the strong centrifugal force associated with Saturn's rapid rotation. Numerical simulations suggest that these interchange injections can be associated with inward flow channels, in which plasma confined to a narrow range of longitudes moves radially toward the planet, gaining energy, while ambient plasma in the adjacent regions moves more slowly outward. Most previous analyses of these events have neglected this radial motion and inferred properties of the events under the assumption that they appear instantaneously at the spacecraft's L-shell and thereafter drift azimuthally. This paper describes features of injections that can be related to their radial motion prior to observation. We use a combination of phase space density profiles and an updated version of a test-particle model to quantify properties of the injection. We are able to infer the longitudinal width of the injection, the radial travel time from its point of origin, and the starting L shell of the injection. We can also predict which energies can remain inside the channel during the radial transport. To highlight the effects of radial propagation at a finite speed, we focus on those interchange injections without extensive features of azimuthal dispersion. Injections that have traveled radially for one or more hours prior to observation would have been initiated at a different local time than that of the observation. Finally, we describe an injection where particles have drifted azimuthally into a flow channel prior to observation by Cassini.

  16. Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HST

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2008-02-01

    Full Text Available We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF vector. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively. It is also shown that the computed open field region agrees with the poleward boundary of the auroras as well as or better than those derived previously from a model in which only the variation of the IMF vector was taken into account. The results again support the hypothesis that the auroral oval at Saturn is associated with the open-closed field line boundary and hence with the solar wind interaction.

  17. Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

    Science.gov (United States)

    Bates, David M.

    2015-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

  18. Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

    Science.gov (United States)

    Bates, David M.

    2015-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

  19. The Saturn PRobe Interior and aTmosphere Explorer (SPRITE) Mission Concept

    Science.gov (United States)

    Atkinson, David H.; Simon, Amy; Banfield, Don

    2017-04-01

    The proposed NASA New Frontiers Saturn PRobe Interior and aTmosphere Explorer (SPRITE) mission would measure the abundance of helium and the other noble gases, elemental and isotopic abundances, the clouds, dynamics, and processes within Saturn's troposphere. In situ measurements of Saturn's atmosphere by SPRITE would provide a significantly improved context for understanding the results from the Galileo Jupiter probe, and the formation and evolution of the gas giant planets, resulting in a paradigm shift in our understanding of the formation, evolution, and ultimately the present day structure of the solar system. The proposed SPRITE concept carries an instrument payload to measure Saturn's atmospheric structure, dynamics, composition, chemistry, and clouds to at least 10 bars. A Quadrupole Mass Spectrometer measures noble gases and noble gas isotopes to accuracies that exceed the Galileo probe measurements at Jupiter and allows for discrimination between competing theories of giant planet formation, evolution, and possible migration. Of particular importance are measurements of helium, key to understanding Saturn's thermal evolution. A Tunable Laser Spectrometer measures molecular abundances and isotope ratios to determine the chemical structure of Saturn's atmosphere, and disequilibrium species such as PH3 and CO which can be used to predict Saturn's deep water abundance. An Atmospheric Structure Instrument provides the pressure/temperature profile of Saturn's atmosphere to determine the altitude profile of static stability, and when combined with cloud measurements from the SPRITE Nephelometer, would elucidate processes that determine the location and structure of Saturn's multiple cloud layers. Coupled with the measurement of atmospheric vertical velocities from the Atmospheric Structure Instrument, a Doppler Wind Experiment provides a measure of the 3-dimensional dynamics of the Saturn atmosphere, including the profile of zonal winds with depth and vertical

  20. The Location of Magnetic Reconnection at Saturn's Magnetopause: a Comparison with Earth

    Science.gov (United States)

    Lewis, W. S.; Fuselier, S.; Frahm, R. A.; Masters, A.; Mukherjee, J.; Petrinec, S. M.; Sillanpaa, I.

    2014-12-01

    Data from the Cassini Electron Spectrometer are used to investigate the location of magnetic reconnection at Saturn's magnetopause. Heated, streaming electron distributions in the boundary layer on the magnetosheath side of the magnetopause are evidence of reconnection and an open magnetopause. A model for the location of reconnection is used to compare the modeled and observed streaming direction of the heated electron distributions. Magnetic reconnection at Saturn's magnetopause is predicted and observed to occur at locations similar to those at Earth's magnetopause. Although not conclusive, the results here are consistent with the expected importance of x-line drifts in suppressing low-shear reconnection. Because of different conditions at Saturn's magnetopause, this suppression is predicted to be stronger at Saturn than at Earth.

  1. Planetary Formation and Evolution Revealed with a Saturn Entry Probe: The Importance of Noble Gases

    CERN Document Server

    Fortney, Jonathan J; Baraffe, Isabelle; Burrows, Adam; Dodson-Robinson, Sarah E; Chabrier, Gilles; Guillot, Tristan; Helled, Ravit; Hersant, Franck; Hubbard, William B; Lissauer, Jack J; Marley, Mark S

    2009-01-01

    The determination of Saturn's atmospheric noble gas abundances are critical to understanding the formation and evolution of Saturn, and giant planets in general. These measurements can only be performed with an entry probe. A Saturn probe will address whether enhancement in heavy noble gases, as was found in Jupiter, are a general feature of giant planets, and their ratios will be a powerful constraint on how they form. The helium abundance will show the extent to which helium has phase separated from hydrogen in the planet's deep interior. Jupiter's striking neon depletion may also be tied to its helium depletion, and must be confirmed or refuted in Saturn. Together with Jupiter's measured atmospheric helium abundance, a consistent evolutionary theory for both planets, including "helium rain" will be possible. We will then be able to calibrate the theory of the evolution of all giant planets, including exoplanets. In addition, high pressure H/He mixtures under giant planet conditions are an important area of...

  2. Chorus, ECH, and Z mode emissions observed at Jupiter and Saturn and possible electron acceleration

    National Research Council Canada - National Science Library

    J D Menietti; Y Y Shprits; R B Horne; E E Woodfield; G B Hospodarsky; D A Gurnett

    2012-01-01

      In this paper we compare and contrast chorus, electron cyclotron harmonics (ECH), and Z mode emissions observed at Jupiter and Saturn and relate them to recent work on electron acceleration at Earth...

  3. A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

    National Research Council Canada - National Science Library

    G. Fischer; S.-Y. Ye; J. B. Groene; A. P. Ingersoll; K. M. Sayanagi; J. D. Menietti; W. S. Kurth; D. A. Gurnett

    2014-01-01

    The periodicity of Saturn kilometric radiation (SKR) varies with time, and its two periods during the first 5 years of the Cassini mission have been attributed to SKR from the northern and southern hemisphere...

  4. Cassini in situ observations of long-duration magnetic reconnection in Saturn's magnetotail

    CERN Document Server

    Arridge, Christopher S; Jackman, Caitriona M; Poh, Gang-Kai; Slavin, James A; Thomsen, Michelle F; André, Nicolas; Jia, Xianzhe; Kidder, Ariah; Lamy, Laurent; Radioti, Aikaterina; Reisenfeld, Dan B; Sergis, Nick; Volwerk, Martin; Walsh, Andrew P; Zarka, Philippe; Coates, Andrew J; Dougherty, Michele K

    2015-01-01

    Magnetic reconnection is a fundamental process in solar system and astrophysical plasmas, through which stored magnetic energy associated with current sheets is converted into thermal, kinetic and wave energy. Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field. The region where magnetic fields reconnect is known as the diffusion region and in this letter we report on the first encounter of the Cassini spacecraft with a diffusion region in Saturn's magnetotail. The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn. This counters the view of reconnection as a transient method of internal plasma loss at Saturn. These results, although d...

  5. Periods, Poles, and Shapes of Irregular Satellites of Saturn from Lightcurves

    Science.gov (United States)

    Denk, Tilmann; Mottola, Stefano

    2014-11-01

    The lightcurve-observation campaign of irregular (outer) moons of Saturn with the Cassini Imaging experiment is ongoing successfully. 21 rotation periods are now known, ranging from 5.5 h to ~3 d. The position of the Cassini spacecraft inside the orbits of the irregular moons allows observations from unusual geometries, especially at various phase angles and rapidly changing aspect angles. Many lightcurves are non-symmetric, and the large diversity of lightcurves for different objects indicates very different shapes. Lightcurves with three prominent maxima and minima are quite common, especially at phase angles higher than ~50°. For several moons, recent observations from different viewing geometries provide the potential to reveal pole directions and convex-hull "photometric shapes". As seen from the poles, Ymir is now known to have a triangular shape with two about equally long sides and one shorter side. Its pole is approximately oriented antipodally to the major planets. Siarnaq data indicate that this moon has also a triangular cross-section, but with a very different pole direction and extreme seasons. Kiviuq’s lightcurves show a very large amplitude even at low phase angles, suggesting a very elongated configuration with a ratio of the equatorial axes of about 3:1.

  6. THE RADIAL DISTRIBUTION OF WATER ICE AND CHROMOPHORES ACROSS SATURN'S SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Filacchione, G.; Capaccioni, F.; Cerroni, P.; Tosi, F.; Ciarniello, M. [INAF-IAPS, Istituto di Astrofisica e Planetologia Spaziali, Area di Ricerca di Tor Vergata, via del Fosso del Cavaliere, 100, I-00133, Rome (Italy); Clark, R. N. [Federal Center, US Geological Survey, Denver, CO 80228 (United States); Nicholson, P. D.; Lunine, J. I.; Hedman, M. M. [Astronomy Department, Cornell University, 418 Space Sciences Building, Ithaca, NY 14853 (United States); Cruikshank, D. P.; Cuzzi, J. N. [NASA Ames Research Center, Moffett Field, CA 94035-1000 (United States); Brown, R. H. [Lunar Planetary Laboratory, University of Arizona, Kuiper Space Sciences 431A, Tucson, AZ 85721-0092 (United States); Buratti, B. J. [NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Flamini, E., E-mail: gianrico.filacchione@iaps.inaf.it [ASI, Italian Space Agency, viale Liegi 26, I-00198 Rome (Italy)

    2013-04-01

    Over the past eight years, the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini orbiter has returned hyperspectral images in the 0.35-5.1 {mu}m range of the icy satellites and rings of Saturn. These very different objects show significant variations in surface composition, roughness, and regolith grain size as a result of their evolutionary histories, endogenic processes, and interactions with exogenic particles. The distributions of surface water ice and chromophores, i.e., organic and non-icy materials, across the Saturnian system, are traced using specific spectral indicators (spectral slopes and absorption band depths) obtained from rings mosaics and disk-integrated satellites observations by VIMS. Moving from the inner C ring to Iapetus, we found a marking uniformity in the distribution of abundance of water ice. On the other hand, the distribution of chromophores is much more concentrated in the rings particles and on the outermost satellites (Rhea, Hyperion, and Iapetus). A reduction of red material is observed on the satellites' surfaces orbiting within the E ring environment likely due to fine particles from Enceladus' plumes. Once the exogenous dark material covering the Iapetus' leading hemisphere is removed, the texture of the water ice-rich surfaces, inferred through the 2 {mu}m band depth, appears remarkably uniform across the entire system.

  7. Analysis of Clumps in Saturn's F Ring from Voyager and Cassini

    CERN Document Server

    French, Robert S; Showalter, Mark R; Antonsen, Adrienne K; Packard, Douglas R

    2014-01-01

    Saturn's F ring is subject to dynamic structural changes over short periods. Among the observed phenomena are diffuse extended bright clumps (ECs) ~ 3-40 degrees in longitudinal extent. These ECs appear, evolve, and disappear over a span of days to months. ECs have been seen by the two Voyager spacecraft, the Cassini orbiter, and various ground- and space-based telescopes. Showalter (2004, Icarus, 171, 356-371) analyzed all Voyager images of the F ring and found that there were 2-3 major and 20-40 minor ECs present in the ring at any given time. We expand upon these results by comparing the ECs seen by Voyager to those seen by Cassini in 2004-2010. We find that the number of minor ECs has stayed roughly constant and the ECs have similar distributions of angular width, absolute brightness, and semimajor axis. However, the common exceptionally bright ECs seen by Voyager are now exceedingly rare, with only two instances seen by Cassini in the six years, and they are now also much dimmer relative to the mean ring...

  8. Propeller peregrinations: Ongoing observations of disk-embedded migration in Saturn's rings

    Science.gov (United States)

    Tiscareno, Matthew S.; Cassini Imaging Team

    2016-10-01

    The "propeller" moons within Saturn's rings are the first objects ever to have their orbits tracked while embedded in a disk, rather than moving through empty space (Tiscareno et al. 2010, ApJL). The km-sized "giant propellers" whose orbits have been tracked in the outer-A ring, as well as their smaller 0.1-km-sized brethren swarming in the mid-A ring, are not seen directly; rather, their locations are inferred by means of the propeller-shaped disturbances they create in the surrounding ring material (Tiscareno et al. 2006, Nature; Sremcevic et al. 2007, Nature; Tiscareno et al. 2008, AJ). The orbits of giant propellers are primarily Keplerian, but with clear excursions of up to several degrees longitude over a decade of observations. Most theories that have been proposed to explain the non-Keplerian motion of propeller moons (e.g., Pan et al. 2012, MNRAS; Tiscareno 2013, P&SS) rely on gravitational and/or collisional interactions between the moon and the surrounding disk, and thus hold out the prospect for directly observing processes that are important in protoplanetary scenarios and other disk systems. We will review the current dynamical models and report on recent ongoing observations by the Cassini imaging camera.

  9. A Survey of Low-Velocity Collisional Features in Saturn's F Ring

    CERN Document Server

    Attree, Nicholas O; Williams, Gareth A; Cooper, Nicholas J

    2013-01-01

    Small (~50km scale), irregular features seen in Cassini images to be emanating from Saturn's F ring have been termed mini-jets by Attree et al. (2012). One particular mini-jet was tracked over half an orbital period, revealing its evolution with time and suggesting a collision with a local moonlet as its origin. In addition to these data we present here a much more detailed analysis of the full catalogue of over 800 F ring mini-jets, examining their distribution, morphology and lifetimes in order to place constraints on the underlying moonlet population. We find mini-jets randomly located in longitude around the ring, with little correlation to the moon Prometheus, and randomly distributed in time, over the full Cassini tour to date. They have a tendency to cluster together, forming complicated `multiple' structures, and have typical lifetimes of ~1d. Repeated observations of some features show significant evolution, including the creation of new mini-jets, implying repeated collisions by the same object. Thi...

  10. Vortices in Saturn's Northern Hemisphere (2008-2015) observed by Cassini ISS

    Science.gov (United States)

    Trammell, Harold Justin; Li, Liming; Jiang, Xun; Pan, Yefeng; Smith, Mark A.; Bering, Edgar A.; Hörst, Sarah M.; Vasavada, Ashwin R.; Ingersoll, Andrew P.; Janssen, Michael A.; West, Robert A.; Porco, Carolyn C.; Li, Cheng; Simon, Amy A.; Baines, Kevin H.

    2016-09-01

    We use observations from the Imaging Science Subsystem on Cassini to create maps of Saturn's Northern Hemisphere (NH) from 2008 to 2015, a time period including a seasonal transition (i.e., spring equinox in 2009) and the 2010 giant storm. The processed maps are used to investigate vortices in the NH during the period of 2008-2015. All recorded vortices have diameters (east-west) smaller than 6000 km except for the largest vortex that developed from the 2010 giant storm. The largest vortex decreased its diameter from ~11,000 km in 2011 to ~5000 km in 2015, and its average diameter is ~6500 km during the period of 2011-2015. The largest vortex lasts at least 4 years, which is much longer than the lifetimes of most vortices (less than 1 year). The largest vortex drifts to north, which can be explained by the beta drift effect. The number of vortices displays varying behaviors in the meridional direction, in which the 2010 giant storm significantly affects the generation and development of vortices in the middle latitudes (25-45°N). In the higher latitudes (45-90°N), the number of vortices also displays strong temporal variations. The solar flux and the internal heat do not directly contribute to the vortex activities, leaving the temporal variations of vortices in the higher latitudes (45-90°N) unexplained.

  11. OGLE-2012-BLG-0724Lb: A Saturn-mass Planet around an M-dwarf

    CERN Document Server

    Hirao, Y; Sumi, T; Bennett, D P; Bond, I A; Rattenbury, N; Suzuki, D; Koshimoto, N; Abe, F; Asakura, Y; Bhattacharya, A; Freeman, M; Fukui, A; Itow, Y; Li, M C A; Ling, C H; Masuda, K; Matsubara, Y; Matsuo, T; Muraki, Y; Nagakane, M; Ohnishi, K; Oyokawa, H; Saito, To; Sharan, A; Shibai, H; Sullivan, D J; Tristram, P J; Yonehara, A; Poleski, R; Skowron, J; Mróz, P; Szymański, M K; Kozłowski, S; Pietrukowicz, P; Soszyński, I; Wyzykowski, Ł; Ulaczyk, K

    2016-01-01

    We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a planetary event, the anomaly was well covered thanks to high cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio $q=(1.58\\pm0.15)\\times10^{-3}$. By conducting a Bayesian analysis, we estimate that the host star is an M-dwarf star with a mass of $M_{\\rm L}=0.29_{-0.16}^{+0.33} \\ M_{\\odot}$ located at $D_{\\rm L}=6.7_{-1.2}^{+1.1} \\ {\\rm kpc}$ away from the Earth and the companion's mass is $m_{\\rm P}=0.47_{-0.26}^{+0.54} \\ M_{\\rm Jup}$. The projected planet-host separation is $a_{\\perp}=1.6_{-0.3}^{+0.4} \\ {\\rm AU}$. Because the lens-source relative proper motion is relatively high, future high resolution images would detect the lens host star and determine the lens properties uniquely. This system is likely a Saturn-mass exoplanet around an ...

  12. Radial Variations in Particle Clumping in Perturbed Regions of Saturn's Rings from Cassini UVIS Stellar Occultations

    Science.gov (United States)

    Colwell, Joshua E.; Esposito, Larry W.; Cooney, James

    2016-10-01

    Showalter and Nicholson (1990, Icarus 87, 285-306) showed that the variance in the Voyager 2 stellar occultation by Saturn's rings could be analyzed to extract information on the sizes of particles in the rings, or, more precisely, on the autocorrelation length, R, of the distribution of ring particles. We have previously reported on applying this principle to the many stellar occultations observed by Cassini's Ultraviolet Imaging Spectrograph (UVIS). Here we present results of the variance at 2 km radial resolution, fine enough to examine changes in the autocorrelation length within the broad troughs of the strongest density waves. We find dips in R in the first several wavelengths of the Janus 2:1 density wave in the inner B ring. In addition, we find a decrease in R in the Mimas 5:3 bending wave. Strong Janus density waves in the A ring show an increase in R in the peaks of the density waves, but no dip below the background level in the troughs. We also see a decrease in R in the broad "halo" regions of the A ring around the strongest resonances, implying less-well-organized self-gravity wakes in those regions and/or smaller or more abundant particles in the gaps between the wakes. We will present our results from multiple occultations and their implications for the collisional environment in strongly perturbed regions in the rings.

  13. Sub-cm Particles in Saturn's Rings from VIMS, UVIS, and RSS occultations

    Science.gov (United States)

    Jerousek, Richard Gregory; Colwell, Josh E.; Hedman, Matthew M.; Marouf, Essam A.; Esposito, Larry W.; Nicholson, Philip D.; French, Richard G.

    2016-10-01

    Particles sizes in Saturn's rings roughly follow a truncated power law. One way to determine the governing parameters of the size distribution is through the analysis of differential optical depths (Zebker et al. 1983). Non-axisymmetric self-gravity wakes complicate this approach when optical depth measurements at different wavelengths are not made at same viewing geometry. Using occultations spanning a wide range of viewing angles and from multiple instruments onboard Cassini (the Ultraviolet Imaging Spectrograph (UVIS), the Visual and Infrared Mapping Spectrometer (VIMS), and the Radio Science Subsystem (RSS)), we forward-model the properties of the self-gravity wakes in Saturn's A and B rings while simultaneously constraining the parameters of the cm – sub-cm particle size distribution. In the absence of wakes, and in regions where particles smaller than ~ 8.86 mm are present, VIMS stellar occultations measure larger optical depths than UVIS stellar occultations due to the diffraction of 2.9 μm light out of the small (0.25 × 0.5 mrad) VIMS field of view compared with UVIS which measures shorter wavelength (0.15 μm) light over a much larger (6.4 × 6.0 mrad) field of view. This excess optical depth combined with RSS X-band (λ = 3.6 cm) optical depths provides a way to probe both the power law slope and the minimum particle size. In the A and B rings where self-gravity wakes are prevalent, we use the wake model of Colwell et al. (2006, 2007) with an additional free parameter representing the excess optical depth which would be measured through the gaps between opaque wakes, by VIMS compared to UVIS. In the B ring and inner A ring we find and absence of sub-cm particles and power law slopes of q ~ 2.8. In the trans-Encke region, where there are a multitude of satellite driven resonances, we find an increasing abundance of sub-cm particles as the outer edge of the A ring is approached. In the C Ring and the Cassini Division, where self-gravity wakes are absent

  14. Tidal Response of Jupiter and Saturn from CMS calculationsTidal Response of Jupiter and Saturn from CMS calculations

    Science.gov (United States)

    Wahl, Sean; Hubbard, William B.; Militzer, Burkhard

    2016-10-01

    The Juno gravity science system promises to provide observational data from Jupiter's gravitational field at an unprecedented precision. Meanwhile, recent ab-initio simulations on mixtures of hydrogen and helium allow for the construction of realistic interior models. The concentric Maclaurin spheroid (CMS) numerical method has been developed for efficient, non-perturbative, self-consistent calculations of shape and gravitational field of a rotating liquid body to this desired precision. Here we present a generalization of the CMS method to three dimensions and included the effect of tides from a satellite. We have identified a number of unexpected features of the static tidal response in the case where a planet's shape is dominated by the rotational bulge. In the general case, there is state mixing of the spherical-harmonic components of the response to the corresponding components of the rotational and tidal excitations. This breaks the degeneracy of the tidal love numbers knm with m, and introduces a dependence of knm on the orbital distance of the satellite. Notably for Jupiter and Saturn, the predicted value of k2 is significantly higher when the planet's high rotation rates are taken into account: k2=0.413 for Saturn and k2=0.590 for Jupiter, accounting for an ~13% and 10% increase over the non-rotating case respectively. We have also done preliminary estimates for the off-resonance dynamic response, which may lead to an additional significant increase in k2. Accurate models of tidal response will be essential for interpreting gravity observations from Juno and future studies, particularly for when filtering for signals from interior dynamics in the observed field. This work was supported by NASA's Juno project. Sean Wahl and Burkhard Militzer acknowledge the support of the National Science Foundation (astronomy and astrophysics research grant 1412646).

  15. An Induced Representation Method for Studying the Stability of Saturn's Ring

    CERN Document Server

    Chakraborty, Soumangsu Bhusan

    2016-01-01

    MacKey constructed a set of induced representation character formulas to calculate the sum of different powers of the eigenvalues of a matrix with finite group symmetry. We show that these results of MacKey can be used to derive the stability condition, m > Cn3, of Maxwell using his symmetric model for a ring of Saturn, as a collection of n identical unit mass particles revolving round Saturn, which has mass m, in a circular orbit.

  16. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft.

    Science.gov (United States)

    Jasinski, J M; Arridge, C S; Lamy, L; Leisner, J S; Thomsen, M F; Mitchell, D G; Coates, A J; Radioti, A; Jones, G H; Roussos, E; Krupp, N; Grodent, D; Dougherty, M K; Waite, J H

    2014-03-16

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions-a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ∼27 and 51 RS . An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection. We observe evidence for reconnection in the cusp plasma at SaturnWe present evidence that the reconnection process can be pulsed at SaturnSaturn's cusp shows similar characteristics to the terrestrial cusp.

  17. Spinning, Breathing, and Flapping: Ion Periodicities in Saturn's Middle Magnetosphere

    Science.gov (United States)

    Ramer, K. M.; Kivelson, M.; Khurana, K. K.; Jia, X.; Sergis, N.; Walker, R. J.

    2013-12-01

    In Saturn's magnetosphere, periodic fluctuations are ubiquitous; for example, periodicities have been observed in Saturn Kilometric Radiation (SKR), in auroral emissions, the magnetic field, electron density, and energetic particle fluxes. In previous work, we extended earlier investigations of periodicities near Saturn's equatorial plane from 6 to 15 RS, determining that ion pressure, magnetic pressure, velocity, and ion density perturbations are roughly modulated at the SLS period. However, the phase relationships obtained in this analysis were confusing and the large scatter inherent in the data led us to question results that suggested significant differences from one radial and local time bin to the next in the phases at which perturbations peaked. In this work, we use an MHD simulation by Jia et al. [2012], which posits rotating vortices in the ionosphere, to put our initial results into context, leading to a deeper understanding of magnetospheric processes and the data returned by Cassini. The simulation shows compellingly that periodicities in field and plasma properties arise from a combination of rotational and compressional perturbations. For example, the magnetic pressure perturbations systematically rotate at the SLS period in the middle magnetosphere. When SLS phase near noon is 250°, near noon at 7.5 Rs the data show that the magnetic pressure perturbation is maximum whereas the ion pressure perturbations are near minimum. The simulation allows us to argue that these anticorrelated extrema occur at the phase of maximum magnetospheric compression when the magnetic field of the dayside plasma sheet in the middle magnetosphere is most dipolarized. At this phase, plasma is not confined to the equator but is distributed along the flux tube; in the resulting thick plasma sheet, the equatorial pressure drops to its lowest value. At the same rotation phase at midnight, near 7.5 Rs the data show that the magnetic pressure is at a minimum and is

  18. Deciphering the embedded wave in Saturn's Maxwell ringlet

    Science.gov (United States)

    French, Richard G.; Nicholson, Philip D.; Hedman, Mathew M.; Hahn, Joseph M.; McGhee-French, Colleen A.; Colwell, Joshua E.; Marouf, Essam A.; Rappaport, Nicole J.

    2016-11-01

    The eccentric Maxwell ringlet in Saturn's C ring is home to a prominent wavelike structure that varies strongly and systematically with true anomaly, as revealed by nearly a decade of high-SNR Cassini occultation observations. Using a simple linear "accordion" model to compensate for the compression and expansion of the ringlet and the wave, we derive a mean optical depth profile for the ringlet and a set of rescaled, background-subtracted radial wave profiles. We use wavelet analysis to identify the wave as a 2-armed trailing spiral, consistent with a density wave driven by an m = 2 outer Lindblad resonance (OLR), with a pattern speed Ωp = 1769.17° d-1 and a corresponding resonance radius ares = 87530.0 km. Estimates of the surface mass density of the Maxwell ringlet range from a mean value of 11g cm-2 derived from the self-gravity model to 5 - 12gcm-2 , as inferred from the wave's phase profile and a theoretical dispersion relation. The corresponding opacity is about 0.12 cm2 g-1, comparable to several plateaus in the outer C ring (Hedman, M.N., Nicholson, P.D. [2014]. Mont. Not. Roy. Astron. Soc. 444, 1369-1388). A linear density wave model using the derived wave phase profile nicely matches the wave's amplitude, wavelength, and phase in most of our observations, confirming the accuracy of the pattern speed and demonstrating the wave's coherence over a period of 8 years. However, the linear model fails to reproduce the narrow, spike-like structures that are prominent in the observed optical depth profiles. Using a symplectic N-body streamline-based dynamical code (Hahn, J.M., Spitale, J.N. [2013]. Astrophys. J. 772, 122), we simulate analogs of the Maxwell ringlet, modeled as an eccentric ringlet with an embedded wave driven by a fictitious satellite with an OLR located within the ring. The simulations reproduce many of the features of the actual observations, including strongly asymmetric peaks and troughs in the inward-propagating density wave. We argue that

  19. Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Key Molecules and Observations of Dust Content

    Science.gov (United States)

    Edgington, Scott G.; Atreya, Sushil H.; Wilson, Eric H.; Baines, Kevin H.; West, Robert A.; Bjoraker, Gordon L.; Fletcher, Leigh N.; Momary, Tom

    2015-04-01

    Cassini has been orbiting Saturn for over ten years now. During this epoch, the ring shadow has moved from covering a large portion of the northern hemisphere to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion in 2004, the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian (~52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (~58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Our previous work [1] examined the variation of the solar flux as a function of solar inclination, i.e. ~8 year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons in Saturn's stratosphere and upper troposphere, including acetylene, ethane, propane, and benzene. Beginning with methane, we investigate the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. Similarly, we assess its impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convective processes in the deep atmosphere. We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically

  20. Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modeling of Key Molecules and Observations of Dust Content

    Science.gov (United States)

    Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; West, R. A.; Fletcher, L. N.; Baines, K. H.; Bjoraker, G. L.; Momary, T.

    2014-12-01

    Cassini has been orbiting Saturn for over ten years now. During this epoch, the ring shadow has moved from covering a large portion of the northern hemisphere to covering a large swath south of the equator and continues to move southward. At Saturn Orbit Insertion in 2004, the ring plane was inclined by ~24 degrees relative to the Sun-Saturn vector. The projection of the B-ring onto Saturn reached as far as 40N along the central meridian (~52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (~58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating into any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like venetian blinds. Our previous work [1] examined the variation of the solar flux as a function of solar inclination, i.e. ~7.25 year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons in Saturn's stratosphere and upper troposphere, including acetylene, ethane, propane, and benzene. Beginning with methane, we investigate the impact on production and loss rates of the long-lived photochemical products leading to haze formation are examined at several latitudes over a Saturn year. Similarly, we assess its impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere is a tracer of convective processes in the deep atmosphere. We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically

  1. NASA Helps Keep the Light Burning for the Saturn Car Company

    Science.gov (United States)

    2003-01-01

    The Saturn Electronics & Engineering, Inc. (Saturn) facility in Marks, Miss., that produces lamp assemblies was experiencing itermittent problems with its automotive under the hood lamps. After numerous testing and engineering efforts, technicians could not pin down the root of the problem. So Saturn contacted the NASA Technology Assistance Program (TAP) at Stennis Space Center. The Marks production facility had been experiencing intermittent problems with under the hood lamp assemblies for some time. The failure rate, at 2 percent, was unacceptable. Every effort was made to identify the problem so that corrective action could be put in place. The problem was investigated and researched by Saturn's engineering department. In addition, Saturn brought in several independent testing laboratories. Other measures included examining the switch component suppliers and auditing them for compliance to the design specifications and for surface contaminants. All attempts to identify the factors responsible for the failures were inconclusive. In an effort to get to the root of the problem, and at the recommendation of the Mississippi Department of Economic Development, Saturn contacted the NASA TAP at Stennis. The NASA Materials and Contamination Laboratory, with assistance from the Stennis Prototype Laboratory, conducted a materials evaluation study on the switch components. The laboratory findings showed the failures were caused by a build-up of carbon-based contaminants on the switch components. Saturn Electronics & Engineering, Inc., is a minority-owned provider of contract manufacturing services to a diverse global marketplace. Saturn operates manufacturing facilities globally serving the North American, European, and Asian markets. Saturn's production facility in Marks, Mississippi, produces more than 1,000,000 lamps and switches monthly. "Since the NASA recommendations were implemented, our internal failure rate for intermittency has dropped to less than .02 percent

  2. Rotation Rate of Saturn's Magnetosphere using CAPS Plasma Measurements

    Science.gov (United States)

    Sittler, E.; Cooper, J.; Simpson, D.; Paterson, W.

    2012-01-01

    We present the present status of an investigation of the rotation rate of Saturn 's magnetosphere using a 3D velocity moment technique being developed at Goddard which is similar to the 2D version used by Sittler et al. (2005) [1] for SOI and similar to that used by Thomsen et al. (2010). This technique allows one to nearly cover the full energy range of the CAPS IMS from 1 V less than or equal to E/Q less than 50 kV. Since our technique maps the observations into a local inertial frame, it does work during roll manoeuvres. We have made comparisons with Wilson et al. (2008) [2] (2005-358 and 2005-284) who performs a bi-Maxwellian fit to the ion singles data and our results are nearly identical. We will also make comparisons with results by Thomsen et al. (2010) [3]. Our analysis uses ion composition data to weight the non-compositional data, referred to as singles data, to separate H+, H2+ and water group ions (W+) from each other. The ion data set is especially valuable for measuring flow velocities for protons, which are more difficult to derive using singles data within the inner magnetosphere, where the signal is dominated by heavy ions (i.e., proton peak merges with W+ peak as low energy shoulder). Our technique uses a flux function, which is zero in the proper plasma flow frame, to estimate fluid parameter uncertainties. The comparisons investigate the experimental errors and potential for systematic errors in the analyses, including ours. The rolls provide the best data set when it comes to getting 4PI coverage of the plasma but are more susceptible to time aliasing effects. Since our analysis is a velocity moments technique it will work within the inner magnetosphere where pickup ions are important and velocity distributions are non-Maxwellian. So, we will present results inside Enceladus' L shell and determine if mass loading is important. In the future we plan to make comparisons with magnetic field observations, use Saturn ionosphere conductivities as

  3. The electron density of Saturn's magnetosphere

    Directory of Open Access Journals (Sweden)

    M. W. Morooka

    2009-07-01

    Full Text Available We have investigated statistically the electron density below 5 cm−3 in the magnetosphere of Saturn (7–80 RS, Saturn radii using 44 orbits of the floating potential data from the RPWS Langmuir probe (LP onboard Cassini. The density distribution shows a clear dependence on the distance from the Saturnian rotation axis (√X2+Y2 as well as on the distance from the equatorial plane (|Z|, indicating a disc-like structure. From the characteristics of the density distribution, we have identified three regions: the extension of the plasma disc, the magnetodisc region, and the lobe regions. The plasma disc region is at L<15, where L is the radial distance to the equatorial crossing of the dipole magnetic field line, and confined to |Z|<5 RS. The magnetodisc is located beyond L=15, and its density has a large variability. The variability has quasi-periodic characteristics with a periodicity corresponding to the planetary rotation. For Z>15 RS, the magnetospheric density distribution becomes constant in Z. However, the density still varies quasi-periodically with the planetary rotation also in this region. In fact, the quasi-periodic variation has been observed all over the magnetosphere beyond L=15. The region above Z=15 RS is identified as the lobe region. We also found that the magnetosphere can occasionally move latitudinally under the control of the density in the magnetosphere and the solar wind. From the empirical distributions of the electron densities obtained in this study, we have constructed an electron density model of the Saturnian nightside magnetosphere beyond 7 RS. The obtained model can well reproduce the observed density distribution, and can thus be useful for magnetospheric modelling studies.

  4. Watch Cassini-Huygens setting off for Saturn and Titan

    Science.gov (United States)

    1997-10-01

    NASA's Cassini spacecraft, to which the Italian Space Agency ASI has made an important contribution, is crammed with instruments prepared by American and European scientists. It will spend four busy years in orbit around Saturn, and explore its famous rings and eighteen known moons. On its arrival at Saturn in 2004, the Cassini orbiter will release the European Space Agency's probe Huygens towards the largest moon, Titan.Also equipped by multinational scientific teams, Huygens will parachute through Titan's atmosphere to accomplish the most distant landing ever made, on the surface of another world. Television coverage of the launch for viewers in Europe On Monday 13 October the launch window for Cassini-Huygens opens at 4.55 a.m. Florida time (EDT). Starting at 4.00 a.m. Florida time (10.00 a.m. in most of western Europe and 9.00 a.m. in Great Britain and Ireland) ESA will provide a live TV transmission via satellite for European news organizations and other organizations wishing to receive it. Views of the launch will be accompanied by interviews with scientists and engineers of the Cassini-Huygens joint mission. A short news package will be transmitted near the end of transmission, and details will be announced on air. If the launch occurs promptly, ESA's TV operation will last until about 60 minutes after launch (i.e. about noon, European time). Technical details for TV reception Two satellites links are available, both carrying English on audio channel 1 and French on audio channel 2. Broadcasters and others with digital receivers will favour Intelsat K, while those with analogue receivers can use Eutelsat 2. Full information on transponders etc. is contained in an appendix to this press release. Paris press centre At ESA Headquarters in Paris, journalists will be able to view the TV transmission and to obtain news and background information about the Cassini-Huygens mission. The press centre will open at 10.00 a.m. on 13 October. If you wish to attend, please

  5. Case study of quasi-steady reconnection in Saturn's magnetotail, and update on our current understanding of mass transport and loss in Saturn's nightside magnetosphere

    Science.gov (United States)

    Jackman, C. M.; Thomsen, M. F.; Mitchell, D. G.; Sergis, N.; Arridge, C. S.; Felici, M.; Badman, S. V.; Paranicas, C.; Jia, X.; Hospodarsky, G. B.; Andriopoulou, M.; Khurana, K. K.; Smith, A. W.; Dougherty, M. K.

    2015-10-01

    We present a case study of an event from August20th (day 232) of 2006, as viewed by magnetic field, plasma, energetic particle and plasma wave sensors (MAG/CAPS/MIMI/RPWS) when the Cassini spacecraft was sampling the region near 32 Rs and 22 hours LT in Saturn's magnetotail. Cassini observed a strong northward-to-southward turning of the magnetic field, which is interpreted as the signature of dipolarization of the field as seen by the spacecraft planetward of the reconnection x-line. This event was accompanied by very rapid (up to ~1500 km s-1) thermal plasma flow toward the planet. At energies above 28 keV, energetic hydrogen and oxygen ion flow bursts were observed to stream planetward from a reconnection site downtail of the spacecraft. Meanwhile a strong field-aligned beam of energetic hydrogen was also observed to stream tailward, likely from an ionospheric source. Saturn Kilometric Radiation emissions were stimulated shortly after the observation of the dipolarization. We discuss the field, plasma, energetic particle and radio observations in the context of the impact this reconnection event had on global magnetospheric dynamics.We also discuss this event in terms of other recent studies of reconnection in Saturn's tail and update on the emerging picture concerning our understanding of how mass is transported and lost within Saturn's magnetosphere.

  6. Modelling of the ring current in Saturn's magnetosphere

    Science.gov (United States)

    Giampieri, G.; Dougherty, M.

    2004-02-01

    . The existence of a ring current inside Saturn's magnetosphere was first suggested by smith80 and ness81,ness82, in order to explain various features in the magnetic field observations from the Pioneer 11 and Voyager 1 and 2 spacecraft. connerney83 formalized the equatorial current model, based on previous modelling work of Jupiter's current sheet and estimated its parameters from the two Voyager data sets. Here, we investigate the model further, by reconsidering the data from the two Voyager spacecraft, as well as including the Pioneer 11 flyby data set. First, we obtain, in closed form, an analytic expression for the magnetic field produced by the ring current. We then fit the model to the external field, that is the difference between the observed field and the internal magnetic field, considering all the available data. In general, through our global fit we obtain more accurate parameters, compared to previous models. We point out differences between the model's parameters for the three flybys, and also investigate possible deviations from the axial and planar symmetries assumed in the model. We conclude that an accurate modelling of the Saturnian disk current will require taking into account both of the temporal variations related to the condition of the magnetosphere, as well as non-axisymmetric contributions due to local time effects.

  7. On the recently determined anomalous perihelion precession of Saturn

    CERN Document Server

    Iorio, Lorenzo

    2008-01-01

    The astronomer E.V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant non-zero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e. \\Delta\\dot\\varpi_Sat = -0.006 +/- 0.002 arcsec/cy; the formal, statistical error is 0.0007 arcsec/cy. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodelled/unmodelled in the force models of the EPM2008 ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter. Both independent analyses by other teams of astronomers and further processing of larger data sets from Cassini will be helpful in clarifying the nature and the true existence of the anomalous pre...

  8. Orbital dynamics in the planar Saturn-Titan system

    CERN Document Server

    Zotos, Euaggelos E

    2015-01-01

    We use the planar circular restricted three-body problem in order to numerically investigate the orbital dynamics of orbits of a spacecraft, or a comet, or an asteroid in the Saturn-Titan system in a scattering region around the Titan. The orbits can escape through the necks around the Lagrangian points $L_1$ and $L_2$ or collide with the surface of the Titan. We explore all the four possible Hill's regions depending on the value of the Jacobi constant. We conduct a thorough numerical analysis on the phase space mixing by classifying initial conditions of orbits and distinguishing between three types of motion: (i) bounded, (ii) escaping and (iii) collisional. In particular, we locate the different basins and we relate them with the corresponding spatial distributions of the escape and crash times. Our results reveal the high complexity of this planetary system. Furthermore, the numerical analysis shows a strong dependence of the properties of the considered basins with the total orbital energy, with a remark...

  9. Dynamical Evidence for a Late Formation of Saturn's Moons

    CERN Document Server

    Ćuk, Matija; Nesvorný, David

    2016-01-01

    We explore the past evolution of Saturn's moons using direct numerical integrations. We find that the past Tethys-Dione 3:2 orbital resonance predicted in standard models likely did not occur, implying that the system is less evolved than previously thought. On the other hand, the orbital inclinations of Tethys, Dione and Rhea suggest that the system did cross the Dione-Rhea 5:3 resonance, which is closely followed by a Tethys-Dione secular resonance. A clear implication is that either the moons are significantly younger than the planet, or that their tidal evolution must be extremely slow (Q > 80,000). As an extremely slow-evolving system is incompatible with intense tidal heating of Enceladus, we conclude that the moons interior to Titan are not primordial, and we present a plausible scenario for the system's recent formation. We propose that the mid-sized moons re-accreted from a disk about 100 Myr ago, during which time Titan acquired its significant orbital eccentricity. We speculate that this disk has f...

  10. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey

    Science.gov (United States)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.

    2016-04-01

    Reconnection within planetary magnetotails is responsible for locally energizing particles and changing the magnetic topology. Its role in terms of global magnetospheric dynamics can involve changing the mass and flux content of the magnetosphere. We have identified reconnection related events in spacecraft magnetometer data recorded during Cassini's exploration of Saturn's magnetotail. The events are identified from deflections in the north-south component of the magnetic field, significant above a background level. Data were selected to provide full tail coverage, encompassing the dawn and dusk flanks as well as the deepest midnight orbits. Overall 2094 reconnection related events were identified, with an average rate of 5.0 events per day. The majority of events occur in clusters (within 3 h of other events). We examine changes in this rate in terms of local time and latitude coverage, taking seasonal effects into account. The observed reconnection rate peaks postmidnight with more infrequent but steady loss seen on the dusk flank. We estimate the mass loss from the event catalog and find it to be insufficient to balance the input from the moon Enceladus. Several reasons for this discrepancy are discussed. The reconnection X line location appears to be highly variable, though a statistical separation between events tailward and planetward of the X line is observed at a radial distance of between 20 and 30RS downtail. The small sample size at dawn prevents comprehensive statistical comparison with the dusk flank observations in terms of flux closure.

  11. The ballistic transport instability in Saturn's rings III: numerical simulations

    CERN Document Server

    Latter, Henrik; Chupeau, Marie

    2014-01-01

    Saturn's inner B-ring and its C-ring support wavetrains of contrasting amplitudes but with similar length scales, 100-1000 km. In addition, the inner B-ring is punctuated by two intriguing `flat' regions between radii 93,000 km and 98,000 km in which the waves die out, whereas the C-ring waves coexist with a forest of plateaus, narrow ringlets, and gaps. In both regions the waves are probably generated by a large-scale linear instability whose origin lies in the meteoritic bombardment of the rings: the ballistic transport instability. In this paper, the third in a series, we numerically simulate the long-term nonlinear evolution of this instability in a convenient local model. Our C-ring simulations confirm that the unstable system forms low-amplitude wavetrains possessing a preferred band of wavelengths. B-ring simulations, on the other hand, exhibit localised nonlinear wave `packets' separated by linearly stable flat zones. Wave packets travel slowly while spreading in time, a result that suggests the obser...

  12. Discovery of a Jupiter/Saturn Analog with Gravitational Microlensing

    CERN Document Server

    Gaudi, B S; Udalski, A; Gould, A; Christie, G W; Maoz, D; Dong, S; McCormick, J; Szymanski, M K; Tristram, P J; Nikolaev, S; Paczynski, B; Kubiak, M; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; De Poy, D L; Han, C; Kaspi, S; Lee, C -U; Mallia, F; Natusch, T; Pogge, R W; Park, B -G; Abe, F; Bond, I A; Botzler, C S; Fukui, A; Hearnshaw, J B; Itow, Y; Kamiya, K; Korpela, A V; Kilmartin, P M; Lin, W; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Okumura, T; Ohnishi, K; Rattenbury, N J; Sako, T; Saito, To; Sato, S; Skuljan, L; Sullivan, D J; Sumi, T; Sweatman, W L; Yock, P C M; Albrow, M D; Allan, A; Beaulieu, J -P; Burgdorf, M J; Cook, K H; Coutures, C; Dominik, M; Dieters, S; Fouqué, P; Greenhill, J; Horne, K; Steele, I; Tsapras, Y; Chaboyer, B; Crocker, A; Frank, S; MacIntosh, B

    2008-01-01

    Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the detection of a multiple-planet system with microlensing. We identify two planets with masses of ~0.71 and ~0.27 times the mass of Jupiter and orbital separations of ~2.3 and ~4.6 astronomical units orbiting a primary star of mass ~0.50 solar masses at a distance of ~1.5 kiloparsecs. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only six confirmed microlensing planet detections suggests that solar system analogs may be common.

  13. Analysis of Saturn kilometric radiation near a source center

    Science.gov (United States)

    Menietti, J. D.; Mutel, R. L.; Schippers, P.; Ye, S.-Y.; Gurnett, D. A.; Lamy, L.

    2011-12-01

    The Cassini spacecraft flew very near a source region of Saturn kilometric radiation (SKR) on day 73 of 2008, the second known encounter with a source region at high latitude. The radio and plasma wave instrument, Radio and Plasma Wave Science, observed intense kilometric emission in the extraordinary X mode, ordinary O mode, and Z mode. The electron low-energy spectrometer obtained a phase space distribution of sufficient energy and pitch angle resolution to allow growth rate calculations. There is evidence of a shell-like electron plasma distribution that is unstable to the growth of SKR via the cyclotron maser instability. The growth rates calculated are adequate to explain the observed X and Z mode emission, but nonlinear effects are required to explain the large O mode gain (as is true for terrestrial observations). Narrowband emission, also present at the time, could also explain both the Z mode and the O mode. We present the results for comparison with a previously reported source region encounter and with similar observations at Earth auroral kilometric source regions.

  14. Variability of southern and northern periodicities of Saturn Kilometric Radiation

    Science.gov (United States)

    Lamy, Laurent

    Among the persistent questions raised by the existence of a rotational modulation of the Saturn Kilometric Radiation (SKR), the origin of the variability of the 10.8 hours SKR period at a 1% level over weeks to years remains intriguing. While its short-term fluctuations (20-30 days) have been related to the variations of the solar wind speed, its long-term fluctuations (months to years) were proposed to be triggered by Enceladus mass-loading and/or seasonal variations. This situation has become even more complicated since the recent identification of two separated periods at 10.8h and 10.6h, each varying with time, corresponding to SKR sources located in the southern (S) and the northern (N) hemispheres, respectively. Here, six years of Cassini continuous radio measurements are investigated, from 2004 (pre-equinox) to the end of 2010 (post-equinox). From S and N SKR, radio periods and phase systems are derived separately for each hemisphere and fluctuations of radio periods are investigated at time scales of years to a few months. Then, the S phase is used to demonstrate that the S SKR rotational modulation is consistent with an intrinsically rotating phenomenon, in contrast with the early Voyager picture.

  15. The Shape of Saturn's Huygens Ringlet Viewed by Cassini ISS

    CERN Document Server

    Spitale, Joseph N

    2015-01-01

    A new model for the shape of the prominent eccentric ringlet in the gap exterior to Saturn's B-ring is developed based on Cassini observations taken over about 8 years. Unlike previous treatments, the new model treats each edge of the ringlet separately. The Keplerian component of the model is consistent with results derived from Voyager observations, and $m=2$ modes forced by the nearby Mimas 2:1 Lindblad resonance are seen. Additionally, a free $m=2$ mode is seen on the outer edge of the ringlet. Significant irregular structure that cannot be described using normal-mode analysis is seen on the ringlet edges as well. Particularly on the inner edge, that structure remains coherent over multi-year intervals, moving at the local Keplerian rate. We interpret the irregular structure as the signature of embedded massive bodies. The long coherence time suggests the responsible bodies are concentrated near the edge of the ringlet. Long wake-like structures originate from two locations on the inner edge of the ringle...

  16. A new model for plasma transport and chemistry at Saturn

    Science.gov (United States)

    Richardson, John D.

    1992-01-01

    A model of plasma transport and chemistry is described which calculates the evolution of a plasma population in latitude and radial distance. This model is applied to the magnetosphere of Saturn, where it is used to fit the density profile of the heavy ions assuming both satellite and ring sources of plasma. Use of an extended source region is found to significantly alter the resulting plasma profile. Water ions cannot fit the observed density profile inside L = 6 even with a large ring source. Oxygen ions can fit the density profile throughout the region inside L = 12 given a suitable profile of neutral hydrogen; a suitable profile contains up to 5 H/cu cm outside L = 4 with the number increasing inside this. Preferred values of K are 1-3 x 10 exp -10 R(S)2/s, but any value K less than 10 exp -9 R(S)2/s can be accommodated. The temperature profile is shown to favor models invoking in situ plasma formation and loss as opposed to models where transport is important.

  17. 通用新星 SATURN AURA XR

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    土星(Saturn)品牌很年轻,所以可以不用考虑什么品牌传统,看到通用集团什么东西好,直接拿来使用就可以了,比如北极星发动机和Epsilon底盘。土星品牌创立的初衷,就是要和国外的进口车进行直接的厮杀。面对强手林立的欧洲、日本竞争者,土星必然要在外观上足够接近美国人的审美。还有,对美国人来说,舒适性是绝对不能妥协的。在土星旗下的L系列停产之后,很多人都预测土星在酝酿一款更具吸引力的豪华型运动车。今天,Saturn为我们带来了Aura这款概念车,意图抢占北美运动车房车市场。

  18. Polar heating in Saturn's thermosphere

    Directory of Open Access Journals (Sweden)

    C. G. A. Smith

    2005-10-01

    Full Text Available A 3-D numerical global circulation model of the Kronian thermosphere has been used to investigate the influence of polar heating. The distributions of temperature and winds resulting from a general heat source in the polar regions are described. We show that both the total energy input and its vertical distribution are important to the resulting thermal structure. We find that the form of the topside heating profile is particularly important in determining exospheric temperatures. We compare our results to exospheric temperatures from Voyager occultation measurements (Smith et al., 1983; Festou and Atreya, 1982 and auroral H3+ temperatures from ground-based spectroscopic observations (e.g. Miller et al., 2000. We find that a polar heat source is consistent with both the Smith et al. determination of T~400 K at ~30° N and auroral temperatures. The required heat source is also consistent with recent estimates of the Joule heating rate at Saturn (Cowley et al., 2004. However, our results show that a polar heat source can probably not explain the Festou and Atreya determination of T~800 K at ~4° N and the auroral temperatures simultaneously.

    Keywords. Ionosphere (Planetary ionosphere – Magnetospherica physics (Planetary magnetospheres – Meterology and atmospheric dynamics (Thermospheric dynamics

  19. Identification of photoelectron energy peaks in Saturn's inner neutral torus

    Science.gov (United States)

    Schippers, P.; André, N.; Johnson, R. E.; Blanc, M.; Dandouras, I.; Coates, A. J.; Krimigis, S. M.; Young, D. T.

    2009-12-01

    We present observations from the Cassini Plasma Electron Spectrometer (CAPS/ELS) of characteristic peaks in the electron energy spectrum that are identified in the innermost regions of the Saturnian magnetosphere during low-latitude orbits of the Cassini spacecraft around Saturn. We show how a narrow electron energy peak at about 20 eV and a possible peak at about 42 eV can be extracted from the background in CAPS observations after the contamination from high-energy particles has been removed from the measurements. We estimate the density of the newly discovered electron population to be a small fraction (10%) of the electron density measured in the CAPS/ELS energy range, and a much smaller fraction (about 1%) of the total electron density measured by Radio and Plasma Wave Science since our measurements are affected by spacecraft negative potential. We suggest that this population corresponds to photoelectrons generated by the solar EUV photoionization of the extended cloud of neutral gas observed in these regions. We use pitch angle information to assess the near-equatorial source of these photoelectrons and a simple model of chemistry in order to further support our interpretation. Therefore, photoionization seems to be an additional process for plasma production in the innermost Saturnian magnetosphere. Finally, we mention that the comparison of the modeled and the observed photoelectron peak energies could be used to estimate the spacecraft potential in this region which is measured independently by the Langmuir Probe.

  20. Poynting-Robertson Effects in Saturn's F Ring

    Science.gov (United States)

    Giuliatti Winter, S. M.

    2000-10-01

    Observations from the Voyager spacecraft have shown that the narrow F ring of Saturn is composed of micrometer-sized particles that extend inward from the core (Showalter et al., Icarus, 1992; Graps et al., Icarus, 1984). These small particles can be disturbed by the effects of the Poynting-Robertson drag (PR drag), which cause their orbital decay. The F ring particles are also perturbed by the nearby satellite Prometheus. The effects of the satellite are intensified during the closest approach with the ring particles. At this special configuration gaps are formed in the ring as result of scattering of particles in the direction of the planet (Giuliatti Winter et al.,PSS, 2000). In this work we analyze the effects of the PR drag combined with the perturbations of the satellite Prometheus. Our results show that depending on the initial conditions of the ring particles the satellite can avoid the orbital decay caused by the PR drag (Giuliatti Winter & Guimar\\ aes, 2000). There are some resonance locations in the region between Prometheus and the F ring, some of them with the satellite Atlas (Giuliatti Winter, 1994). We also analyze the orbital evolution of a dust ring particle subjected to PR drag and Atlas perturbations. Acknowledgement: SMGW (Proc. 99/11965) thanks FAPESP for the financial support.

  1. Seasonal Evolution of Saturn's Polar Temperatures and Composition

    CERN Document Server

    Fletcher, Leigh N; Sinclair, J A; Orton, G S; Giles, R S; Hurley, J; Gorius, N; Achterberg, R K; Hesman, B E; Bjoraker, G L

    2014-01-01

    The seasonal evolution of Saturn's polar atmospheric temperatures and hydrocarbon composition is derived from a decade of Cassini Composite Infrared Spectrometer (CIRS) 7-16 $\\mu$m thermal infrared spectroscopy. We construct a near-continuous record of atmospheric variability poleward of 60$^\\circ$ from northern winter/southern summer (2004, $L_s=293^\\circ$) through the equinox (2009, $L_s=0^\\circ$) to northern spring/southern autumn (2014, $L_s=56^\\circ$). The hot tropospheric polar cyclones and the hexagonal shape of the north polar belt are both persistent features throughout the decade of observations. The hexagon vertices rotated westward by $\\approx30^\\circ$ longitude between March 2007 and April 2013, confirming that they are not stationary in the Voyager-defined System III longitude system as previously thought. The extended region of south polar stratospheric emission has cooled dramatically poleward of the sharp temperature gradient near 75$^\\circ$S, coinciding with a depletion in the abundances of ...

  2. Discovery of a Jupiter/Saturn analog with gravitational microlensing.

    Science.gov (United States)

    Gaudi, B S; Bennett, D P; Udalski, A; Gould, A; Christie, G W; Maoz, D; Dong, S; McCormick, J; Szymanski, M K; Tristram, P J; Nikolaev, S; Paczynski, B; Kubiak, M; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; Depoy, D L; Han, C; Kaspi, S; Lee, C-U; Mallia, F; Natusch, T; Pogge, R W; Park, B-G; Abe, F; Bond, I A; Botzler, C S; Fukui, A; Hearnshaw, J B; Itow, Y; Kamiya, K; Korpela, A V; Kilmartin, P M; Lin, W; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Okumura, T; Ohnishi, K; Rattenbury, N J; Sako, T; Saito, To; Sato, S; Skuljan, L; Sullivan, D J; Sumi, T; Sweatman, W L; Yock, P C M; Albrow, M D; Allan, A; Beaulieu, J-P; Burgdorf, M J; Cook, K H; Coutures, C; Dominik, M; Dieters, S; Fouqué, P; Greenhill, J; Horne, K; Steele, I; Tsapras, Y; Chaboyer, B; Crocker, A; Frank, S; Macintosh, B

    2008-02-15

    Searches for extrasolar planets have uncovered an astonishing diversity of planetary systems, yet the frequency of solar system analogs remains unknown. The gravitational microlensing planet search method is potentially sensitive to multiple-planet systems containing analogs of all the solar system planets except Mercury. We report the detection of a multiple-planet system with microlensing. We identify two planets with masses of approximately 0.71 and approximately 0.27 times the mass of Jupiter and orbital separations of approximately 2.3 and approximately 4.6 astronomical units orbiting a primary star of mass approximately 0.50 solar mass at a distance of approximately 1.5 kiloparsecs. This system resembles a scaled version of our solar system in that the mass ratio, separation ratio, and equilibrium temperatures of the planets are similar to those of Jupiter and Saturn. These planets could not have been detected with other techniques; their discovery from only six confirmed microlensing planet detections suggests that solar system analogs may be common.

  3. The Smallest Particles in Saturn's A and C Rings

    CERN Document Server

    Harbison, Rebecca A; Hedman, Matthew M

    2013-01-01

    Radio occultations of Saturn's main rings by spacecraft suggest a power law particle size-distribution down to sizes of the order of 1 cm (Marouf et al., 1983), (Zebker et al., 1985). The lack of optical depth variations between ultraviolet and near-IR wavelengths indicate a lack of micron-sized particles. Between these two regimes, the particle-size distribution is largely unknown. A cutoff where the particle-size distribution turns over must exist, but the position and shape of it is not clear from existing studies. Using a series of solar occultations performed by the VIMS instrument on-board Cassini in the near-infrared, we are able to measure light forward scattered by particles in the A and C rings. With a model of diffraction by ring particles, and the previous radio work as a constraint on the slope of the particle size distribution, we estimate the minimum particle size using a truncated power-law size distribution. The C Ring shows a minimum particle size of $4.1^{+3.8}_{-1.3}$ mm, with an assumed p...

  4. Planetary period oscillations in Saturn's magnetosphere: Evidence in magnetic field phase data for rotational modulation of Saturn kilometric radiation emissions

    Science.gov (United States)

    Andrews, D. J.; Cecconi, B.; Cowley, S. W. H.; Dougherty, M. K.; Lamy, L.; Provan, G.; Zarka, P.

    2011-09-01

    Initial Voyager observations of Saturn kilometric radiation (SKR) indicated that the modulations in emitted power near the ˜11 h planetary rotation period are “strobe like,” varying with a phase independent of observer position, while subsequent Cassini studies of related oscillations in the magnetospheric magnetic field and plasma parameters have shown that these rotate around the planet with a period close to the SKR period. However, analysis of magnetic oscillation data over the interval 2004-2010 reveals the presence of variable secular drifts between the phases of the dominant southern period magnetic oscillations and SKR modulations, which become very marked after Cassini apoapsis moved for the first time into the postdusk sector in mid-2009. Here we use a simple theoretical model to show that such phase drifts arise if the SKR modulation phase also rotates around the auroral oval, combined with a highly restricted view of the SKR sources by the spacecraft due to the conical beaming of the emissions. Strobe-like behavior then occurs in the predawn-to-noon sector where the spacecraft has a near-continuous view of the most intense midmorning SKR sources, in agreement with the Voyager findings, while elsewhere the SKR modulation phase depends strongly on spacecraft local time, being in approximate antiphase with the midmorning sources in the postdusk sector. Supporting evidence for this scenario is provided through an independent determination of the variable rotation period of the southern magnetic field perturbations throughout the 6 year interval.

  5. The Cassini Imaging Science Subsystem: Science Today and in Cassini's Final Three Years

    Science.gov (United States)

    West, R. A.

    2014-12-01

    The Cassini Imaging Science Subsystem (ISS) instrument was designed for long-range, high resolution imaging of Saturn and its system of rings and moons. It consists of two cameras, a Narrow Angle Camera (NAC, 2000 mm focal length) and a Wide Angle Camera (WAC, 200 mm focal length). The NAC has sensitivity from 200 nm to 1100 nm. The WAC is sensitive from 350 nm to 1100 nm. Among the mission highlights thus far for ISS have been discoveries of particulate plumes from Enceladus, details of surface topography along the 'tiger stripes', the discovery of an equatorial ridge on Iapetus, detailed images of small inner moons and distant moons Phoebe and Hyperion, features in Saturn's rings including perturbed edges near embedded moons, 'propellers', ephemeral clumps, and evidence for impacts in the rings and free-oscillation modes in Saturn's interior. The camera documented the aftermath of a methane/ethane 'rain' storm on Titan as well as seasonal behavior in the detached haze and visible airglow generated by magnetospheric plasma. The cameras documented the formation and evolution of a giant storm on Saturn, lightning from storms on Saturn, and determined that eddies are powering Saturn's zonal jets. In the F-ring and Proximal orbits ISS will obtain even better resolution on the rings, planet and inner moons.

  6. Exploration of the Saturn System by the Cassini Mission: Observations with the Cassini Infrared Spectrometer

    Science.gov (United States)

    Abbas, Mian M.

    2014-01-01

    The Cassini mission is a joint NASA-ESA international mission, launched on October 17, 1997 with 12 instruments on board, for exploration of the Saturn system. A composite Infrared Spectrometers is one of the major instruments. Successful insertion of the spacecraft in Saturn's orbit for an extended orbital tour occurred on July 1, 2004. The French Huygens-Probe on board, with six instruments was programmed for a soft landing on Titan's surface occurred in January 2005. The broad range scientific objectives of the mission are: Exploration of the Saturn system for investigations of the origin, formation, & evolution of the solar system, with an extensive range of measurements and the analysis of the data for scientific interpretations. The focus of research dealing with the Cassini mission at NASA/MSFC in collaboration with the NASA/Goddard Space Flight Center, JPL, as well as the research teams at Oxford/UK and Meudon Observatory/France, involves the Infrared observations of Saturn and its satellites, for measurements of the thermal structure and global distributions of the atmospheric constituents. A brief description of the Cassini spacecraft, the instruments, the objectives, in particular with the infrared observations of the Saturn system will be given. The analytical techniques for infrared radiative transfer and spectral inversion programs, with some selected results for gas constituent distributions will be presented.

  7. Simultaneous multi-wavelength observations of Saturn's aurorae : energy budget and magnetospheric dynamics

    Science.gov (United States)

    Lamy, L.

    2011-10-01

    Similarly to other magnetized planets, accelerated electrons entering Saturn's auroral regions generate powerful emissions. They divide into Ultraviolet (UV) and Infrared (IR) aurorae, originating from collisions with the upper atmosphere, and Saturn's Kilometric Radiation (SKR), radiated by an electron cyclotron resonance above the atmosphere up a few Saturn's radii (Rs). Previous studies have identified a large scale conjugacy between radio and UV, as well as IR and UV auroral emissions. Here, we investigate two days of observations of Saturn's aurorae at radio, UV and IR wavelengths, by the Cassini RPWS, UVIS and VIMS instruments, and their relationship with a reservoir of equatorial energetic particles mapped by energetic neutral atoms (ENA), as measured by MIMI-INCA (see Figure ??). This interval of time reveals a series of regular SKR modulations at the southern SKR phase, and interestingly includes an unusual (while also regular) enhancement of the auroral activity observed simultaneously at all wavelengths. This event is likely to illustrate a (regular) nightside injection of energetic particles, possibly induced by a plasmoid ejection, then co-rotating with the planet at the southern SKR period, while feeding an extended longitudinal sector of intense auroral emissions. We analyze quantitatively complementary informations brought by these different datasets in terms of energy budget transferred to the southern auroral region, as well as magnetospheric dynamics, in order to address the nature and the scheme of the Saturn's southern rotational modulation.

  8. NEW INSIGHTS ON SATURN'S FORMATION FROM ITS NITROGEN ISOTOPIC COMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Mousis, Olivier; Lunine, Jonathan I. [Center for Radiophysics and Space Research, Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Fletcher, Leigh N. [Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, Parks Road, Oxford OX1 3PU (United Kingdom); Mandt, Kathleen E. [Southwest Research Institute, San Antonio, TX 78228 (United States); Ali-Dib, Mohamad [Université de Franche-Comté, Institut UTINAM, CNRS/INSU, UMR 6213, Observatoire des Sciences de l' Univers de Besançon (France); Gautier, Daniel [LESIA, Observatoire de Paris, CNRS, UPMC, Univ. Paris-Diderot, F-92195 Meudon Cedex (France); Atreya, Sushil, E-mail: olivier.mousis@obs-besancon.fr [Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143 (United States)

    2014-12-01

    The recent derivation of a lower limit for the {sup 14}N/{sup 15}N ratio in Saturn's ammonia, which is found to be consistent with the Jovian value, prompted us to revise models of Saturn's formation using as constraints the supersolar abundances of heavy elements measured in its atmosphere. Here we find that it is possible to account for both Saturn's chemical and isotopic compositions if one assumes the formation of its building blocks at ∼45 K in the protosolar nebula, provided that the O abundance was ∼2.6 times protosolar in its feeding zone. To do so, we used a statistical thermodynamic model to investigate the composition of the clathrate phase that formed during the cooling of the protosolar nebula and from which the building blocks of Saturn were agglomerated. We find that Saturn's O/H is at least ∼34.9 times protosolar and that the corresponding mass of heavy elements (∼43.1 M {sub ⊕}) is within the range predicted by semi-convective interior models.

  9. Structures in the D ring and Roche division tied to asymmetries in Saturn's magnetosphere

    Science.gov (United States)

    Chancia, Robert O.; Hedman, Matthew M.; Carter, Brian

    2016-10-01

    Saturn's dusty rings contain multiple patterns that appear to be rotating around the planet at about the same rate as Saturn itself, and so are probably generated by resonances with asymmetries in the planet's gravitational or magnetic fields. These structures are found in the D ring (which lies interior to the main rings) and in the Roche Division (which is located just outside the main rings, between the A and F rings). In 2007 the strongest patterns in both of these regions appeared to track magnetospheric anomalies associated with the Saturn Kilometric Radiation (SKR). This implied that these rings were responding to structures in the planet's magnetosphere, which is not unreasonable since the particles in both these ring regions are very small and therefore sensitive to non-gravitational forces. Over the last few years, the frequencies of the SKR and related magnetospheric asymmetries have shifted, and we have observed some changes in the ring patterns that might be connected with these shifts. However, there are also patterns in these rings that appear to have more stable rotation rates and so could reflect more persistent asymmetries in Saturn's magnetosphere. These patterns can therefore provide novel insights into the structure and evolution of Saturn's magnetosphere.

  10. Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis

    Science.gov (United States)

    Wilson, Jeffrey D.

    1999-01-01

    The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.

  11. Cassini Radio Science Experiments on Saturn and Titan Preserved Because of Lewis Analysis

    Science.gov (United States)

    Wilson, Jeffrey D.

    1999-01-01

    The Cassini mission to Saturn is an international venture with participation from NASA, the European Space Agency, and the Italian Space Agency. The Cassini spacecraft was launched from Cape Canaveral in October 1997 and is scheduled to arrive at Saturn in July 2004. After arrival, the spacecraft will orbit Saturn about 60 times over a period of 4 years. During this time, the Cassini Radio Science Subsystem will be used to investigate the atmosphere and rings of Saturn and the atmosphere of its largest moon, Titan--which is larger than Mercury and is the only moon in our solar system with a dense atmosphere. A critical component in Cassini s Radio Science Subsystem is a traveling-wave tube (TWT) that was designed at the NASA Lewis Research Center and built by Hughes Electronic Dynamics Division (ref. 1). This TWT will amplify downlink microwave signals at a frequency of 32 GHz for the Deep Space Network and will be involved in a number of experiments. These include occultation experiments in which the microwave signal will be beamed through rings and atmospheres toward Earth. Researchers will analyze the received signals to determine the sizes and distributions of the particles in the rings and the structure and composition of the atmospheres. The Radio Science Subsystem also will also be used to more accurately determine the mass and size of Saturn and its moons, to investigate the solar corona, and to search for gravity waves from outside the solar system.

  12. [Imaging].

    Science.gov (United States)

    Chevrot, A; Drapé, J L; Godefroy, D; Dupont, A M; Pessis, E; Sarazin, L; Minoui, A

    1997-01-01

    The panoply of imaging techniques useful in podology is essentially limited to X-rays. Standard "standing" and "lying" X-rays furnish most of the required information. Arthrography is sometimes performed, in particular for trauma or tumour of the ankle. CT scan and MRI make a decisive contribution in difficult cases, notably in fractures and in small fractures without displacement. The two latter techniques are useful in tendon, ligament and muscular disorders, where echography is also informative. Rigorous analysis of radiographies and a good knowledge of foot disorders make these imaging techniques efficacious.

  13. How Iapetus is Painted by Saturn's Irregular Satellites

    Science.gov (United States)

    Tamayo, Dan; Burns, J. A.; Hamilton, D. P.; Hedman, M. M.

    2010-10-01

    The leading hemisphere of Iapetus, Saturn's outermost regular satellite, is ten times darker than its trailing side. To explain this unique albedo distribution, Soter (1974) proposed that collisionally generated dust from the dark outer irregular satellite Phoebe has evolved inward due to radiation forces and coated Iapetus’ leading side. The recent discovery (Verbiscer et al. 2009) of the colossal Phoebe ring between the orbits of Iapetus and Phoebe indicates that Soter's mechanism is active at some level. . To calibrate the effectiveness of this source, we follow the histories of Phoebe-ring dust under the relevant perturbations and thereby evaluate the particles’ probability of striking Iapetus, as well as the expected spatial distribution on the Iapetan surface. We find that, of the long-lived particles (those larger than 4 µm), those larger than 10 µm are virtually certain to strike Iapetus. Their calculated distribution across the surface matches well the measured albedo pattern in longitude. To explain the observed bright polar caps, our computed polar-dust-deposition rates must be overwhelmed by sublimation products from equatorial regions as proposed in the thermal runaway model of Spencer & Denk (2010); we thus constrain the latter model. We also track the dust originating from all the other known irregular moons, finding that a substantial fraction of the material from retrograde moons would eventually coat Iapetus--perhaps explaining why the spectrum of Iapetus’ dark material differs somewhat from Phoebe's (Buratti et al. 2005). We find that dust from lower-eccentricity moons with inclinations nearer 180° is more likely to strike Iapetus. . Finally, of those dust particles that do not strike Iapetus, we find that most land on Titan, with a smaller fraction hitting Hyperion. As has been previously conjectured (Burns et al. 1996), such exogenous dust, coupled with Hyperion's chaotic rotation could explain Hyperion's roughly uniform, moderate

  14. Slicing The 2010 Saturn's Storm: Upper Clouds And Hazes

    Science.gov (United States)

    Perez-Hoyos, Santiago; Sanz-Requena, J. F.; Sanchez-Lavega, A.; Hueso, R.

    2012-10-01

    At the end of 2010 a small storm erupted in Saturn's northern mid-latitudes. Starting from a localized perturbation, it grew up to be a global-scale disturbance and cover the whole latitude band by February, 2011 (Fletcher et al. 2011, Science 332; Sánchez-Lavega et al. 2011, Nature 475; Fischer et al. 2011, Nature 475). By June, 2011 the storm was facing its end and gradually disappeared (Sánchez-Lavega et al. 2012, Icarus 220). In this work we use the observations acquired by the Cassini ISS instrument during the whole process to investigate the vertical cloud and haze structure above the ammonia condensation level (roughly 1 bar). Cassini ISS observations cover visual wavelengths from the blue to the near-infrared including two methane absorption bands. Such observations have been modeled using a radiative transfer code which reproduces the atmospheric reflectivity as a function of observation/illumination geometry and wavelength together with a retrieval technique to find maximum likelihood atmospheric models. This allows to investigate some atmospheric parameters: cloud-top pressures, aerosol optical thickness and particle absorption, among others. We will focus on two aspects: (1) maximum likelihood models for the undisturbed reference atmosphere in the 15°N to 45°N band before and after the disturbance; (2) models for particular structures during the development of the global-scale phenomenon. Our results show a general increase of particle density and single-scattering albedo inside the storm. However, some discrete features showing anomalous structure and related to the storm peculiar dynamics will also be discussed. Acknowledgments: This work was supported by the Spanish MICIIN project AYA2009-10701 with FEDER funds, by Grupos Gobierno Vasco IT-464-07 and by Universidad País Vasco UPV/EHU through program UFI11/55.

  15. MIGRATION OF SMALL MOONS IN SATURN's RINGS

    Energy Technology Data Exchange (ETDEWEB)

    Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-02-20

    The motions of small moons through Saturn's rings provide excellent tests of radial migration models. In theory, torque exchange between these moons and ring particles leads to radial drift. We predict that moons with Hill radii r {sub H} {approx} 2-24 km should migrate through the A ring in 1000 yr. In this size range, moons orbiting in an empty gap or in a full ring eventually migrate at the same rate. Smaller moons or moonlets-such as the propellers-are trapped by diffusion of disk material into corotating orbits, creating inertial drag. Larger moons-such as Pan or Atlas-do not migrate because of their own inertia. Fast migration of 2-24 km moons should eliminate intermediate-size bodies from the A ring and may be responsible for the observed large-radius cutoff of r {sub H} {approx} 1-2 km in the size distribution of the A ring's propeller moonlets. Although the presence of Daphnis (r {sub H} Almost-Equal-To 5 km) inside the Keeler gap challenges this scenario, numerical simulations demonstrate that orbital resonances and stirring by distant, larger moons (e.g., Mimas) may be important factors. For Daphnis, stirring by distant moons seems the most promising mechanism to halt fast migration. Alternatively, Daphnis may be a recent addition to the ring that is settling into a low inclination orbit in {approx}10{sup 3} yr prior to a phase of rapid migration. We provide predictions of observational constraints required to discriminate among possible scenarios for Daphnis.

  16. A vertical rift in Saturn's inner C ring

    Science.gov (United States)

    Nicholson, Philip D.; Hedman, Matthew M.

    2016-11-01

    In 1988 Rosen and Lissauer identified an unusual wavelike feature in Saturn's inner C ring as a bending wave driven by a nodal resonance with Titan (Science 241, 690). This is sometimes referred to as the - 1 : 0 resonance since it occurs where the local nodal regression rate is approximately equal to -nT , where nT = 22 .577∘d-1 is Titan's orbital mean motion. We have used a series of 44 stellar occultation profiles of this wave observed by the Cassini VIMS instrument to test their hypothesis. We find that, as predicted, this wave is an outward-propagating m = 1 spiral with a leading orientation and a retrograde pattern speed approximately equal to -nT . But the most intriguing feature associated with the wave is a narrow gap that lies ∼7 km outside the resonance. This gap varies noticeably in width and is seen in roughly 3/4 of the occultation profiles, appearing to rotate with the wave in a retrograde direction. We have developed a simple kinematical model that accounts for the observations and consists of a continuous but very narrow gap (radial width ≃ 0.6 km), the edges of which are vertically distorted by the propagating bending wave as it crosses the region. Differences in viewing geometry then largely account for the apparent width variations. We find vertical amplitudes of 3.8 km for the inner edge and 1.2 km for the outer edge in 2008, with nodes misaligned by ∼110°. Moreover, both edges of the gap are slightly eccentric, with pericenters aligned with Titan, suggesting that the eccentricities are forced by the nearby Titan apsidal resonance. We hypothesize that the gap forms because the local slopes in the bending wave become so great that nonlinear effects result in the physical disruption of the ring within its first wavelength, beyond which point the wave re-establishes itself with a reduced amplitude.

  17. Magnetic reconnection in Saturn's magnetotail: A comprehensive magnetic field survey.

    Science.gov (United States)

    Smith, A. W.; Jackman, C. M.; Thomsen, M. F.; Dougherty, M. K.

    2015-10-01

    Magnetic reconnection is a fundamental process throughout the solar system, significantly shaping and modulating the magnetospheres of the magnetized planets. Within planetary magnetotails reconnection can be responsible for energizing particles and potentially changing the total flux and mass contained within the magnetosphere. The Kronian magnetosphere is thought to be a middle ground between the rotationally dominated Jovian magnetosphere and the solar wind driven terrestrial magnetosphere. However, previous studies have not been able to find a statistical reconnection x-line, as has been possible at both Jupiter and Earth. Additionally the standard picture of magnetotail reconnection at Saturn, developed by Cowley et al. [2004], suggests a potential asymmetry between the dawn and dusk flanks, caused by different reconnection processes dominating. This work centers on the development of an algorithm designed to find reconnection related events in spacecraft magnetometer data, aiming to reduce the bias that manual searches could inherently introduce, thereby ensuring the validity of any statistical analysis. The algorithm primarily identifies the reconnection related events from deflections in the north-south component of the magnetic field, allowing an almost uninterrupted in-situ search (when the spacecraft is situated within the magnetotail). The new catalogue of candidate reconnection events, produced by the algorithm, enables a more complete statistical view of reconnection in the Kronian magnetotail. Well-studied data encompassing the deep magnetotail and dawn flank (particularly from orbits in 2006) were used to train the algorithm and develop reasonable criteria. The algorithm was then applied to data encompassing the dusk flank (including orbits from 2009, for which plasma data have been examined by Thomsen et al. [2014]). This combination enables a robust, and global, comparison of reconnection rates, signatures and properties in the Kronian magnetotail.

  18. Cassini RSS occultation observations of density waves in Saturn's rings

    Science.gov (United States)

    McGhee, C. A.; French, R. G.; Marouf, E. A.; Rappaport, N. J.; Schinder, P. J.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Johnston, D.; Rochblatt, D.

    2005-08-01

    On May 3, 2005, the first of a series of eight nearly diametric occultations by Saturn's rings and atmosphere took place, observed by the Cassini Radio Science (RSS) team. Simultaneous high SNR measurements at the Deep Space Network (DSN) at S, X, and Ka bands (λ = 13, 3.6, and 0.9 cm) have provided a remarkably detailed look at the radial structure and particle scattering behavior of the rings. By virtue of the relatively large ring opening angle (B=-23.6o), the slant path optical depth of the rings was much lower than during the Voyager epoch (B=5.9o), making it possible to detect many density waves and other ring features in the Cassini RSS data that were lost in the noise in the Voyager RSS experiment. Ultimately, diffraction correction of the ring optical depth profiles will yield radial resolution as small as tens of meters for the highest SNR data. At Ka band, the Fresnel scale is only 1--1.5 km, and thus even without diffraction correction, the ring profiles show a stunning array of density waves. The A ring is replete with dozens of Pandora and Prometheus inner Lindblad resonance features, and the Janus 2:1 density wave in the B ring is revealed with exceptional clarity for the first time at radio wavelengths. Weaker waves are abundant as well, and multiple occultation chords sample a variety of wave phases. We estimate the surface mass density of the rings from linear density wave models of the weaker waves. For stronger waves, non-linear models are required, providing more accurate estimates of the wave dispersion relation, the ring surface mass density, and the angular momentum exchange between the rings and satellite. We thank the DSN staff for their superb support of these complex observations.

  19. Microwave absorptivity in the Saturn atmosphere from Cassini Radio Science

    Science.gov (United States)

    Kliore, A. J.; Marouf, E. A.; Flasar, F. M.

    2011-12-01

    Since 2005, the Cassini spacecraft has collected data from numerous radio occultations by the atmosphere of Saturn. These occultations probed a wide range of latitudes, ranging from equatorial to near-polar. The radio system of Cassini transmits three coherent downlinks to Earth at S-Band (13.04 cm), X-Band (3.56 cm), and Ka-Band (0.94 cm) wavelengths. With the Deep Space Net 70 m receiving stations, The signal-to-noise ratio (SNR) is approximately 48 dB at X-Band, and 38 dB at S-band. At Ka-band, 34 m DSN stations are used, resulting in an SNR of about 41 dB. These SNRs are quite adequate to follow the signals through the top of the microwave-absorbing regions before the noise-floor is reached. By subtracting the refractive defocusing attenuation in the atmosphere (derived from the phase data) from the total attenuation, one obtains the attenuation due to absorption (dB0, which can then be inverted to obtain vertical profiles of absorptivity (dB km-1 ) at each of the three wavelengths. Preliminary results show the expected large effect of wavelength on the absorptivity profiles, with the shorter wavelength signals being absorbed higher in the atmosphere. These profiles can be used to estimate the vertical density profiles of known microwave absorbers, such as NH3 and PH3, examples of which are presented .This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, San Jose State University, and NASA Goddard Space Flight Center with support from the Cassini program.

  20. Ogle-2012-blg-0724lb: A Saturn Mass Planet Around an M-dwarf

    Science.gov (United States)

    Hirao, Y.; Sumi, T.; Bennett, D. P.; Bond, I. A.; Rattenbury, N.; Suzuki, D.; Koshimoto, N.; Abe, F.; Asakura, Y.; Bhattacharya, A.

    2016-01-01

    We report the discovery of a planet by the microlensing method, OGLE-2012-BLG-0724Lb. Although the duration of the planetary signal for this event was one of the shortest seen for a planetary event, the anomaly was well covered thanks to high-cadence observations taken by the survey groups OGLE and MOA. By analyzing the light curve, this planetary system is found to have a mass ratio q = (1.58 +/- 0.15) x 10(exp -3). By conducting a Bayesian analysis, we estimate that the host star is an M dwarf with a mass of M(sub L) = 0.29(+0.33/-0.16) solar mass located at D(sub L) = 6.7(+1.1/-1.2) kpc away from the Earth and the companion's mass is m(sub P) = 0.47(+0.54/-0.26) M(Jup). The projected planet- host separation is a falsum = 1.6(+0.4/-0.3) AU. Because the lens-source relative proper motion is relatively high, future highresolution images would detect the lens host star and determine the lens properties uniquely. This system is likely a Saturn-mass exoplanet around an M dwarf, and such systems are commonly detected by gravitational microlensing. This adds another example of a possible pileup of sub-Jupiters (0.2 less than m(sub P)/M(sub Jup) less than 1) in contrast to a lack of Jupiters (approximately 1-2 M(sub Jup)) around M dwarfs, supporting the prediction by core accretion models that Jupiter-mass or more massive planets are unlikely to form around M dwarfs.

  1. HST Hot-Jupiter Transmission Spectral Survey: Clear Skies for Cool Saturn WASP-39b

    Science.gov (United States)

    Fischer, Patrick D.; Knutson, Heather A.; Sing, David K.; Henry, Gregory W.; Williamson, Michael W.; Fortney, Jonathan J.; Burrows, Adam S.; Kataria, Tiffany; Nikolov, Nikolay; Showman, Adam P.; Ballester, Gilda E.; Désert, Jean-Michel; Aigrain, Suzanne; Deming, Drake; Lecavelier des Etangs, Alain; Vidal-Madjar, Alfred

    2016-08-01

    We present the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) optical transmission spectroscopy of the cool Saturn-mass exoplanet WASP-39b from 0.29-1.025 μm, along with complementary transit observations from Spitzer IRAC at 3.6 and 4.5 μm. The low density and large atmospheric pressure scale height of WASP-39b make it particularly amenable to atmospheric characterization using this technique. We detect a Rayleigh scattering slope as well as sodium and potassium absorption features; this is the first exoplanet in which both alkali features are clearly detected with the extended wings predicted by cloud-free atmosphere models. The full transmission spectrum is well matched by a clear H2-dominated atmosphere, or one containing a weak contribution from haze, in good agreement with the preliminary reduction of these data presented in Sing et al. WASP-39b is predicted to have a pressure-temperature profile comparable to that of HD 189733b and WASP-6b, making it one of the coolest transiting gas giants observed in our HST STIS survey. Despite this similarity, WASP-39b appears to be largely cloud-free, while the transmission spectra of HD 189733b and WASP-6b both indicate the presence of high altitude clouds or hazes. These observations further emphasize the surprising diversity of cloudy and cloud-free gas giant planets in short-period orbits and the corresponding challenges associated with developing predictive cloud models for these atmospheres.

  2. Six Centuries Old Spiral of Vertical Corrugations in Saturn's C-Ring

    Science.gov (United States)

    Marouf, E. A.; French, R. G.; Rappaport, N. J.; Wong, K.; McGhee, C.; Anabtawi, A.

    2011-12-01

    Likely evidence of nearly six centuries old collision of captured cometary material with Saturn's Ring C is uncovered in recent Cassini Radio Science ring observations. Three Cassini ring occultation experiments were especially designed so that radio signals transmitted by Cassini to the Earth pass through the rings when the rings are nearly closed as viewed by the ground receiving stations of the NASA Deep Space Network (DSN). In this special geometry, the long path of the radio signals through the rings enhances sensitivity to detection of very tenuous ring material and allows ~400 meters resolution profiling of its radial structure. The observations uncover previously undetectable quasi-periodic optical depth undulations in 4 sub-regions of the innermost ~4000 km of Ring C (~74,480-77,740 km). The structure modulates a tenuous background optical depth of ~0.05 and has peak-to-peak fluctuations corrugations 4-10 meters in height likely caused by a past ring tilting event (collision with cometary debris) and subsequent differential nodal regression of particle orbits. Time evolution of the perturbations creates a tightly wound spiral pattern of ring height variations which when probed by the radio signals yield the observed tenuous quasi-periodic optical depth fluctuations. The corrugations model was proposed by Hedman et al. [Science 332, 2011] to explain intriguing 30-50 km wavelength structure observed in Cassini images (ISS) across Ring C. The RSS wavelength-radius behavior is in general agreement with the corrugation model prediction; however, important differences persist (ring mass effect?). The much shorter RSS corrugation wavelength compared with ISS implies a separate ring tilting event that is older by ~600 years (late 1300's), and the two tones separation suggests two sub-events ~50 years apart. Together with reported detection of similar corrugations within the tenuous Jovian rings [Showalter et al., Science 332, 2011], the collective observations

  3. Planar wire array performance scaling at multi-MA levels on the Saturn generator.

    Energy Technology Data Exchange (ETDEWEB)

    Chuvatin, Alexander S. (Laboratoire du Centre National de la Recherche Scientifique Ecole Polytechnique, Palaiseau, France); Jones, Michael; Vesey, Roger Alan; Waisman, Eduardo M.; Esaulov, Andrey A. (University of Nevada, Reno, NV); Ampleford, David J.; Kantsyrev, Victor Leonidovich (University of Nevada, Reno, NV); Cuneo, Michael Edward; Rudakov, L. I. (Icarus Research Inc., Bethesda, MD); Coverdale, Christine Anne; Jones, Brent Manley; Safronova, Alla S. (University of Nevada, Reno, NV)

    2007-10-01

    A series of twelve shots were performed on the Saturn generator in order to conduct an initial evaluation of the planar wire array z-pinch concept at multi-MA current levels. Planar wire arrays, in which all wires lie in a single plane, could offer advantages over standard cylindrical wire arrays for driving hohlraums for inertial confinement fusion studies as the surface area of the electrodes in the load region (which serve as hohlraum walls) may be substantially reduced. In these experiments, mass and array width scans were performed using tungsten wires. A maximum total radiated x-ray power of 10 {+-} 2 TW was observed with 20 mm wide arrays imploding in {approx}100 ns at a load current of {approx}3 MA, limited by the high inductance. Decreased power in the 4-6 TW range was observed at the smallest width studied (8 mm). 10 kJ of Al K-shell x-rays were obtained in one Al planar array fielded. This report will discuss the zero-dimensional calculations used to design the loads, the results of the experiments, and potential future research to determine if planar wire arrays will continue to scale favorably at current levels typical of the Z machine. Implosion dynamics will be discussed, including x-ray self-emission imaging used to infer the velocity of the implosion front and the potential role of trailing mass. Resistive heating has been previously cited as the cause for enhanced yields observed in excess of jxB-coupled energy. The analysis presented in this report suggests that jxB-coupled energy may explain as much as the energy in the first x-ray pulse but not the total yield, which is similar to our present understanding of cylindrical wire array behavior.

  4. Tilting Jupiter (a bit) and Saturn (a lot) During Planetary Migration

    CERN Document Server

    Vokrouhlicky, David

    2015-01-01

    We study the effects of planetary late migration on the gas giants obliquities. We consider the planetary instability models from Nesvorny & Morbidelli (2012), in which the obliquities of Jupiter and Saturn can be excited when the spin-orbit resonances occur. The most notable resonances occur when the $s_7$ and $s_8$ frequencies, changing as a result of planetary migration, become commensurate with the precession frequencies of Jupiter's and Saturn's spin vectors. We show that Jupiter may have obtained its present obliquity by crossing of the $s_8$ resonance. This would set strict constrains on the character of migration during the early stage. Additional effects on Jupiter's obliquity are expected during the last gasp of migration when the $s_7$ resonance was approached. The magnitude of these effects depends on the precise value of the Jupiter's precession constant. Saturn's large obliquity was likely excited by capture into the $s_8$ resonance. This probably happened during the late stage of planetary ...

  5. Skirting Saturn's Rings and Skimming Its Cloud Tops: Planning Cassini's End of Mission

    Science.gov (United States)

    Manor-Chapman, Emily; Magee, Kari; Brooks, Shawn; Edgington, Scott; Heventhal, William; Sturm, Erick

    2014-01-01

    In October 2010, the Cassini spacecraft embarked on the seven-year Solstice Mission. The mission will culminate with a spectacular series of orbits that bring Cassini between Saturn's innermost ring, the D ring, and the cloud tops of the planet. The spacecraft will make its closest passages ever to the planet allowing for unprecedented science to be collected on Saturn and its rings. These final orbits will expose the spacecraft to new environments, which presents a number of challenges to planning the final mission phase. While these challenges will require adaptations to planning processes and operations, they are not insurmountable. This paper describes the challenges identified and the steps taken to mitigate them to enable collection of unique Saturn system science.

  6. Cassini Operational Sun Sensor Risk Management During Proximal Orbit Saturn Ring Plane Crossings

    Science.gov (United States)

    Bates, David M.

    2016-01-01

    NASA's Cassini Spacecraft, launched on October 15th, 1997 which arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004–08), and has since been approved for a first and second extended mission through 2017. As part of the final extended missions, Cassini will begin an aggressive and exciting campaign of high inclination, low altitude flybys within the inner most rings of Saturn, skimming Saturn’s outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, requires a strategy for managing the Sun Sensor Assembly (SSA) health, the details of which are presented in this paper.

  7. Lyman-alpha observations in the vicinity of Saturn with Copernicus

    Science.gov (United States)

    Barker, E.; Cazes, S.; Emerich, C.; Vidal-Madjar, A.; Owen, T.

    1980-01-01

    For the first time, high-resolution Ly-alpha observations of the Saturn vicinity were completed with the Princeton spectrometer on board the Copernicus satellite. They showed that near a minimum solar activity the emissions related to several sources are 250 + or - 50 rayleighs for the interplanetary medium in a near-downwind direction, less than 100 rayleighs for the rings, 200 + or - 100 rayleighs for a torus linked to the Titan orbit, and 1400 + or - 450 rayleighs for the disk of Saturn. These results induce some constraints through the corresponding theoretical evaluations: the B ring as the primary source of the atoms for the ring emissions; an efficient production mechanism for hydrogen atoms in the Titan torus; and a slightly larger eddy diffusion coefficient in the Saturn atmosphere than in the Jupiter atmosphere near solar minimum.

  8. Observations of the J = 10 manifold of the pure rotational band of phosphine on Saturn

    Science.gov (United States)

    Haas, M. R.; Erickson, E. F.; Goorvitch, D.; Mckibbin, D. D.; Rank, D. M.

    1986-01-01

    Saturn was observed in the vicinity of the J = 10 manifold of the pure rotational band of phosphine on 1984 July 10 and 12 from NASA's Kuiper Airborne Observatory with the facility far-infrared cooled grating spectrometer. On each night observations of the full disk plus rings were made at 4 to 6 discrete wavelengths which selectively sampled the manifold and the adjacent continuum. The previously reported detection of this manifold is confirmed. After subtraction of the flux due to the rings, the data are compared with disk-averaged models of Saturn. It is found that PH3 must be strongly depleted above the thermal inversion (approx. 70 mbar). The best fitting models consistent with other observational constaints indicate that PH3 is significantly depleted at even deeper atmospheric levels ( or = 500 mbar), implying an eddy diffusion coefficient for Saturn of 10 to the 4 cm sq/sec.

  9. The Concentric Maclaurin Spheroid method with tides and a rotational enhancement of Saturn's tidal response

    Science.gov (United States)

    Wahl, Sean M.; Hubbard, William B.; Militzer, Burkhard

    2017-01-01

    We extend to three dimensions the Concentric Maclaurin Spheroid method for obtaining the self-consistent shape and gravitational field of a rotating liquid planet, to include a tidal potential from a satellite. We exhibit, for the first time, an important effect of the planetary rotation rate on tidal response of gas giants, whose shape is dominated by the centrifugal potential from rapid rotation. Simulations of planets with fast rotation rates like those of Jupiter and Saturn, exhibit significant changes in calculated tidal love numbers knm when compared with non-rotating bodies. A test model of Saturn fitted to observed zonal gravitational multipole harmonics yields k2 = 0.413 , consistent with a recent observational determination from Cassini astrometry data (Lainey et al., 2016.). The calculated love number is robust under reasonable assumptions of interior rotation rate, satellite parameters, and details of Saturn's interior structure. The method is benchmarked against several published test cases.

  10. The Concentric Maclaurin Spheroid method with tides and a rotational enhancement of Saturn's tidal response

    CERN Document Server

    Wahl, Sean M; Militzer, Burkhard

    2016-01-01

    We extend to three dimensions the Concentric Maclaurin Spheroid method for obtaining the self-consistent shape and gravitational field of a rotating liquid planet, to include a tidal potential from a satellite. We exhibit, for the first time, the important effect of the planetary rotation rate on tidal response of gas giants. Simulations of planets with fast rotation rates like those of Jupiter and Saturn, exhibit significant changes in calculated tidal love numbers $k_{nm}$ when compared with non-rotating bodies. A test model of Saturn fitted to observed zonal gravitational multipole harmonics yields $k_2=0.413$, consistent with a recent observational determination from Cassini astrometry data (Lainey et al., 2016). The calculated love number is robust under reasonable assumptions of interior rotation rate, satellite parameters, and details of Saturn's interior structure. The method is benchmarked against several published test cases.

  11. Interaction of moist convection with zonal jets on Jupiter and Saturn

    Science.gov (United States)

    Li, Liming; Ingersoll, Andrew P.; Huang, Xianglei

    2006-01-01

    Observations suggest that moist convection plays an important role in the large-scale dynamics of Jupiter's and Saturn's atmospheres. Here we use a reduced-gravity quasigeostrophic model, with a parameterization of moist convection that is based on observations, to study the interaction between moist convection and zonal jets on Jupiter and Saturn. Stable jets with approximately the same width and strength as observations are generated in the model. The observed zonal jets violate the barotropic stability criterion but the modeled jets do so only if the flow in the deep underlying layer is westward. The model results suggest that a length scale and a velocity scale associated with moist convection control the width and strength of the jets. The length scale and velocity scale offer a possible explanation of why the jets of Saturn are stronger and wider than those of Jupiter.

  12. Cusp observation at Saturn's high-latitude magnetosphere by the Cassini spacecraft

    Science.gov (United States)

    Jasinski, J. M.; Arridge, C. S.; Lamy, L.; Leisner, J. S.; Thomsen, M. F.; Mitchell, D. G.; Coates, A. J.; Radioti, A.; Jones, G. H.; Roussos, E.; Krupp, N.; Grodent, D.; Dougherty, M. K.; Waite, J. H.

    2014-03-01

    We report on the first analysis of magnetospheric cusp observations at Saturn by multiple in situ instruments onboard the Cassini spacecraft. Using this we infer the process of reconnection was occurring at Saturn's magnetopause. This agrees with remote observations that showed the associated auroral signatures of reconnection. Cassini crossed the northern cusp around noon local time along a poleward trajectory. The spacecraft observed ion energy-latitude dispersions—a characteristic signature of the terrestrial cusp. This ion dispersion is "stepped," which shows that the reconnection is pulsed. The ion energy-pitch angle dispersions suggest that the field-aligned distance from the cusp to the reconnection site varies between ˜27 and 51 RS. An intensification of lower frequencies of the Saturn kilometric radiation emissions suggests the prior arrival of a solar wind shock front, compressing the magnetosphere and providing more favorable conditions for magnetopause reconnection.

  13. The Evolution and Internal Structure of Jupiter and Saturn with Compositional Gradients

    CERN Document Server

    Vazan, A; Podolak, M; Kovetz, A

    2016-01-01

    The internal structure of gas giant planets may be more complex than the commonly assumed core-envelope structure with an adiabatic temperature profile. Different primordial internal structures as well as various physical processes can lead to non-homogenous compositional distributions. A non-homogenous internal structure has a significant impact on the thermal evolution and final structure of the planets. In this paper, we present alternative structure and evolution models for Jupiter and Saturn allowing for non-adiabatic primordial structures and the mixing of heavy elements by convection as these planets evolve. We present the evolution of the planets accounting for various initial composition gradients, and in the case of Saturn, include the formation of a helium-rich region as a result of helium rain. We investigate the stability of regions with composition gradients against convection, and find that the helium shell in Saturn remains stable and does not mix with the rest of the envelope. In other cases,...

  14. Cassini spectra and photometry 0.25–5.1 μm of the small inner satellites of Saturn

    Science.gov (United States)

    Buratti, B.J.; Bauer, J.M.; Hicks, M.D.; Mosher, J.A.; Filacchione, G.; Momary, T.; Baines, K.H.; Brown, R.H.; Clark, R.N.; Nicholson, P.D.

    2010-01-01

    The nominal tour of the Cassini mission enabled the first spectra and solar phase curves of the small inner satellites of Saturn. We present spectra from the Visual Infrared Mapping Spectrometer (VIMS) and the Imaging Science Subsystem (ISS) that span the 0.25-5.1 ??m spectral range. The composition of Atlas, Pandora, Janus, Epimetheus, Calypso, and Telesto is primarily water ice, with a small amount (???5%) of contaminant, which most likely consists of hydrocarbons. The optical properties of the "shepherd" satellites and the coorbitals are tied to the A-ring, while those of the Tethys Lagrangians are tied to the E-ring of Saturn. The color of the satellites becomes progressively bluer with distance from Saturn, presumably from the increased influence of the E-ring; Telesto is as blue as Enceladus. Janus and Epimetheus have very similar spectra, although the latter appears to have a thicker coating of ring material. For at least four of the satellites, we find evidence for the spectral line at 0.68 ??m that Vilas et al. [Vilas, F., Larsen, S.M., Stockstill, K.R., Gaffley, M.J., 1996. Icarus 124, 262-267] attributed to hydrated iron minerals on Iapetus and Hyperion. However, it is difficult to produce a spectral mixing model that includes this component. We find no evidence for CO2 on any of the small satellites. There was a sufficient excursion in solar phase angle to create solar phase curves for Janus and Telesto. They bear a close similarity to the solar phase curves of the medium-sized inner icy satellites. Preliminary spectral modeling suggests that the contaminant on these bodies is not the same as the exogenously placed low-albedo material on Iapetus, but is rather a native material. The lack of CO2 on the small inner satellites also suggests that their low-albedo material is distinct from that on Iapetus, Phoebe, and Hyperion. ?? 2009 Elsevier Inc.

  15. Zonal jets and QBO-like oscillations on Jupiter and Saturn

    Science.gov (United States)

    Showman, Adam P.; Zhang, Xi; Tan, Xianyu

    2016-10-01

    At the levels of their visible cloud decks, the giant planets Jupiter and Saturn exhibit numerous east-west (zonal) jet streams with speeds ranging up to 150 m/sec on Jupiter and 400 m/sec on Saturn. Moreover, both planets exhibit long-term stratospheric oscillations involving perturbations of zonal wind and temperature that propagate downward over time on timescales of ~4 years (Jupiter) and ~15 years (Saturn). These oscillations, dubbed the Quasi Quadrennial Oscillation (QQO) for Jupiter and the Semi-Annual Oscillation (SAO) on Saturn, are thought to be analogous to the Quasi-Biennial Oscillation (QBO) on Earth, which is driven by upward propagation of equatorial waves from the troposphere. Here, we test the hypothesis that the zonal jets on Jupiter and Saturn, as well as QBO-like oscillations, can result from interaction of the stably stratified atmosphere with an underlying convective interior. We performed global, three-dimensional, high-resolution numerical simulations of the flow in the stratosphere and upper troposphere of Jupiter-like planets. The effect of convection is parameterized by introducing thermal perturbations that randomly perturb the radiative convective boundary with some characteristic timescale, horizontal wavenumber, and amplitude. Radiative damping is represented using a Newtonian cooling scheme with a characteristic radiative time constant. In the simulations, the convective perturbations generate atmospheric waves and turbulence that interact with the rotation to produce numerous zonal jets. Moreover, the equatorial stratosphere exhibits stacked eastward and westward jets that migrate downward over time, exactly as occurs in the terrestrial QBO, Jovian QQO, and Saturnian SAO. This is the first demonstration of a QBO-like phenomenon in 3D numerical simulations of a giant planet. We will describe how the properties of the zonal jets and equatorial oscillation depend on the details of the forcing and damping. These simulations have

  16. Search for Saturn's X-ray aurorae at the arrival of a solar wind shock

    Science.gov (United States)

    Branduardi-Raymont, G.; Ford, P. G.; Hansen, K. C.; Lamy, L.; Masters, A.; Cecconi, B.; Coates, A. J.; Dougherty, M. K.; Gladstone, G. R.; Zarka, P.

    2013-05-01

    After a decade of observations, evidence for X-ray auroral emission from Saturn has yet to be found. By analogy with processes known to take place on Jupiter, Saturnian X-ray aurorae may be expected to be powered by charge exchange (CX) between energetic ions and the planet's atmospheric neutrals; if the ions are of solar origin, the emission should be brightest during episodes of enhanced solar wind (SW). We have explored this possibility by propagating SW parameters measured near the Earth to Saturn, and triggering X-ray observations at the time SW enhancements were expected to reach the planet. This was done in April-May 2011 with the Chandra X-ray Observatory, and we report on two observations carried out at the time when a significant SW disturbance reached Saturn, as indicated by Cassini magnetic field, plasma and radio measurements: variability is observed between the two Chandra datasets, but we do not find evidence for X-ray brightening in the auroral regions. The variability can be explained by scattering of solar X-rays in Saturn's atmosphere during an episode of solar X-ray flaring. We conclude that the strength of any CX auroral X-ray emission on Saturn was below Chandra's detectability threshold. By-products of this investigation are stringent upper limits on the X-ray emission of Titan and Enceladus. The Cassini measurements concurrent with the Chandra observations confirm and pinpoint temporally the arrival of the SW enhancement at Saturn. SW propagation predictions are a useful tool for investigating and interpreting the effects of SW interactions with planetary environments.

  17. NEXT Ion Propulsion System Configurations and Performance for Saturn System Exploration

    Science.gov (United States)

    Benson, Scott W.; Riehl, John P.; Oleson, Steven R.

    2007-01-01

    The successes of the Cassini/Huygens mission have heightened interest to return to the Saturn system with focused robotic missions. The desire for a sustained presence at Titan, through a dedicated orbiter and in-situ vehicle, either a lander or aerobot, has resulted in definition of a Titan Explorer flagship mission as a high priority in the Solar System Exploration Roadmap. The discovery of active water vapor plumes erupting from the tiger stripes on the moon Enceladus has drawn the attention of the space science community. The NASA's Evolutionary Xenon Thruster (NEXT) ion propulsion system is well suited to future missions to the Saturn system. NEXT is used within the inner solar system, in combination with a Venus or Earth gravity assist, to establish a fast transfer to the Saturn system. The NEXT system elements are accommodated in a separable Solar Electric Propulsion (SEP) module, or are integrated into the main spacecraft bus, depending on the mission architecture and performance requirements. This paper defines a range of NEXT system configurations, from two to four thrusters, and the Saturn system performance capability provided. Delivered mass is assessed parametrically over total trip time to Saturn. Launch vehicle options, gravity assist options, and input power level are addressed to determine performance sensitivities. A simple two-thruster NEXT system, launched on an Atlas 551, can deliver a spacecraft mass of over 2400 kg on a transfer to Saturn. Similarly, a four-thruster system, launched on a Delta 4050 Heavy, delivers more than 4000 kg spacecraft mass. A SEP module conceptual design, for a two thruster string, 17 kW solar array, configuration is characterized.

  18. The inner small satellites of Saturn: Their varied surfaces tell dynamic tales

    Science.gov (United States)

    Thomas, Peter C.; Helfenstein, P.; Burns, J. A.

    2013-10-01

    According to images from the Cassini Imaging Science Subsystem (ISS), the surface forms and overall shapes of Saturn’s inner small satellites occur in groups that populate different orbital niches. Co-orbitals Janus and Epimetheus are the most lunar-like of the small satellites; ring moons Atlas, Pan, and Daphnis have latitude-dependent morphology likely related to how ring material is supplied (Charnoz et al., 2007). The shepherding moon Prometheus may show a stripped mantle/core structure. Arc/ring embedded moons are small, smooth ellipsoids, unique among well-imaged small solar system objects. The Trojan satellites (Calypso, Telesto, Helene) have deep coverings showing multi-step histories of deposition and erosion, and include branching networks of downslope transport. We report the quantitative characteristics of these bodies’ shapes, mean properties, and surface characteristics. The differences may arise from the amounts of loose material available to cover the surfaces. Modeling of ejecta sources from large icy satellites in addition to interactions with ring particles may be required to explain all the variation among these small, icy bodies. The semi-global drainage patterns on the Trojans are especially enigmatic. Why is there nothing comparable on other small satellites? The tapered albedo markings on the Trojans suggest process-specific surface properties. Cassini ISS UV3/IR3 color ratios show that, for Helene, erosion and downslope motion result in a surface that is bluer in color; or a less active surface remains/becomes redder. Sustained exogenic processes such as E-ring particle impacts and charged-particle bombardment compete with geological processes, but on the Trojans, both leave strong signatures. The different amounts of interconnected surfaces on the small satellites range from the cratered landscapes of Janus and Epimetheus, through the semi-global drainage patterns of the Trojans, to complete smoothing of the arc/ring embedded objects

  19. Influence of Hot Plasma Pressure on Global Structure of Saturn's Magnetodisk

    CERN Document Server

    Achilleos, N; Arridge, C S; Sergis, N; Wilson, R J; Thomsen, M F; Coates, A J

    2010-01-01

    Using a model of force balance in Saturn's disk-like magnetosphere, we show that variations in hot plasma pressure can change the magnetic field configuration. This effect changes (i) the location of the magnetopause, even at fixed solar wind dynamic pressure, and (ii) the magnetic mapping between ionosphere and disk. The model uses equatorial observations as a boundary condition-we test its predictions over a wide latitude range by comparison with a Cassini high-inclination orbit of magnetic field and hot plasma pressure data. We find reasonable agreement over time scales larger than the period of Saturn kilometric radiation (also known as the camshaft period).

  20. Temperature Variations of Saturn Rings with Viewing Geometries from Prime to Equinox Cassini Missions

    Science.gov (United States)

    Deau, E. A.; Spilker, L. J.; Morishima, R.; Brooks, S.; Pilorz, S.; Altobelli, N.

    2011-01-01

    After more than six years in orbit around Saturn, the Cassini Composite Infrared Spectrometer (CIRS) has acquired an extensive set of measurements of Saturn's main rings (A, B, C and Cassini Division) in the thermal infrared. Temperatures were retrieved for the lit and unlit rings over a variety of ring geometries that include phase angle, solar and spacecraft elevations and local time. We show that some of these parameters (solar and spacecraft elevations, phase angle) play a role in the temperature variations in the first order, while the others (ring and particle local time) produced second order effects. The results of this comparison will be presented.

  1. Waves and eddies simulated by high-resolution Global Climate Modeling of Saturn's troposphere and stratosphere

    Science.gov (United States)

    Spiga, Aymeric; Guerlet, Sandrine; Meurdesoif, Yann; Indurain, Mikel; Millour, Ehouarn; Dubos, Thomas; Sylvestre, Mélody; Leconte, Jérémy; Fouchet, Thierry

    2015-11-01

    The longevity of the Cassini mission permitted a detailed analysis of Saturn's tropospheric storms, an exceptional coverage of Saturn's Great White Spot (and subsequent stratospheric warming), an assessment of the remarkable stability of the hexagonal polar jet, and the seasonal monitoring of Saturn's equatorial oscillation. Those observations open new questions that add to those related to the extent and forcing of Saturn's alternated jets. One of the best step forward to progress is to build a Global Climate Model (GCM) for giant planets by coupling an hydrodynamical solver (dynamical core) with physical models for external forcings on the fluid. We built a new GCM for Saturn both versatile and powerful enough to resolve resolve the eddies arising from hydrodynamical instabilities and forcing the planetary-scale jets, extend from the troposphere to the stratosphere with good enough vertical resolution, and use optimized radiative transfer to predict seasonal tendencies over decade-long giant planets' years. To that end, we coupled our seasonal radiative model tailored for Saturn with DYNAMICO, the next state-of-the-art dynamical core for Earth and planetary climate studies in our lab, using an original icosahedral mapping of the planetary sphere which ensures excellent conservation and scalability properties in massively parallel resources. Using a new petaflops acquisition by CINES (France), we run our GCM for Saturn down to unprecedented resolutions of 1/4° and 1/8°, and to run sensitivity tests at 1/2° resolution. Those high-resolution GCM runs show a detailed view into a striking variety of eddies and vortices on Saturn, as well as the arising of alternated banded jets, the formation of a polar vortex, the deformation of the polar jet into polygonal structures. We will assess the nature and characteristics of both eddies and eddy-driven features in the troposphere and in the stratosphere, using spectral and dynamical analysis. We will discuss how close our

  2. Ion Composition of the Thermal Plasma in the F-Ring Region of Saturn

    Science.gov (United States)

    Ip, W. H.; Tseng, W. L.; Hsu, J. K.; Wei, C. E.; Shen, C. H.

    2016-12-01

    In the final phase of the Cassini mission in 2016-2017, the spacecraft will first move to orbits with periapse outside the F-ring and then to orbits grazing the upper atmosphere of Saturn. These trajectories will provide the unique opportunity to sample the structures and composition of Saturn's ionosphere but also those of the main rings. From an assessment of the neutral gas and plasma environment of the rings, we investigate the formation of molecular ions and nano-grains in the areas to be probed by Cassini during its F-ring and Proximal orbits

  3. Density waves in Saturn's rings probed by radio and optical occultation - Observational tests of theory

    Science.gov (United States)

    Brophy, Thomas G.; Rosen, Paul A.

    1992-01-01

    A parallel examination is conducted of Voyager radio and photopolarimeter occultation observations of the Saturn A ring's density waves. The radio instrument waves exhibit an average -90 deg offset from the dynamical phase. A warping height of about 100-m amplitude can qualtitatively reproduce this phase shift, while preserving the overall model wave shape. These results may be profoundly relevant for satellite-ring torque calculations in Saturn's rings, given the deposition of all of the net torque of the standard model in the first wavelength.

  4. Sex-related differences of coronary atherosclerosis regression following maximally intensive statin therapy: insights from SATURN.

    Science.gov (United States)

    Puri, Rishi; Nissen, Steven E; Shao, Mingyuan; Ballantyne, Christie M; Barter, Phillip J; Chapman, M John; Erbel, Raimund; Libby, Peter; Raichlen, Joel S; Uno, Kiyoko; Kataoka, Yu; Nicholls, Stephen J

    2014-10-01

    .12 ± 0.13%, p = 0.007) and TAV regression (-10.1 ± 1.1 mm(3) vs. -7.16 ± 0.65 mm(3), p = 0.023) than men, whereas PAV and TAV regression did not differ by sex, with LDL-C levels ≥70 mg/dl. Women with coronary disease demonstrate greater coronary atheroma regression than men when empirically prescribed guideline-driven potent statin therapy. This benefit appears in the setting of lower on-treatment LDL-C levels. (CRESTOR Athero Imaging Head to Head IVUS Study [SATURN]; NCT000620542). Copyright © 2014 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  5. Transport and chemical loss rates in Saturn's inner plasma disk

    Science.gov (United States)

    Holmberg, M. K. G.; Wahlund, J.-E.; Vigren, E.; Cassidy, T. A.; Andrews, D. J.

    2016-03-01

    The Kronian moon Enceladus is constantly feeding its surrounding with new gas and dust, from cryovolcanoes located in its south polar region. Through photoionization and impact ionization of these neutrals, a plasma disk is created, which mainly contains hydrogen ions and water group ions. This paper investigates the importance of ion loss by outward radial transport and ion loss by dissociative recombination, which is the dominant chemical loss process in the inner plasma disk. We use plasma densities derived from several years of measurements by the Cassini Radio and Plasma Wave Science electric field power spectral density and Langmuir probe to calculate the total flux tube content NL2. Our calculation shows that NL2 agrees well with earlier estimates within dipole L shell 8. We also show that loss by transport dominates chemical loss between L shells 4 and 10. Using extrapolation of available measurements, we extend the study to include L shells 2.5 to 4. The results indicate that loss by transport dominates chemical loss also between L shells 2.5 and 4. The loss rate by transport is around five times larger at L shell 5, and the difference increases as L7.7 beyond L = 5, for the net ion population. Chemical loss may still be important for the structure of the plasma disk in the region closest to Enceladus (around ±0.5 RS) at 3.95 RS (1 RS = Saturn's equatorial radius = 60,268 km), since the transport and chemical loss rates only differ by a factor of ˜2 in this region. We also derive the total plasma content of the plasma disk between L shells 4 and 10 to be 1.9 × 1033 ions and the total ion source rate for the same region to be 5.8 × 1027 s-1. The estimated equatorial ion production rate P ranges from 2.6 × 10-5 cm-3 s-1 (at L = 10) to 1.1 × 10-4 cm-3 s-1 (at L = 4.8). The net mass loading rate is derived to be 123 kg/s for L shells 4 to 10.

  6. Photometric modeling of viscous overstability in Saturn's rings

    Science.gov (United States)

    Salo, H.; Schmidt, J.

    2011-10-01

    The viscous overstability of dense planetary rings offers a plausible mechanism for the generation of observed ~ 150 m radial density variations in the B and the inner A ring of Saturn [1, 12]. Viscous overstability, in the form of spontaneous growth of axisymmetric oscillations, arises naturally in N-body simulations, in the limit of high impact frequency and moderately weak selfgravity [4, 8, 9, 10]. For example, a selfgravitating system of identical particles with internal density ~ half of solid ice, becomes overstable for optical depths τ > 1, forming oscillations on about 100 meter scale. Like self-gravity wakes (with typical ~ 20° trailing pitch angle), overstable oscillations lead to alongitude-dependent brightness of the rings. Due to their axisymmetric nature, the expected longitude of minimum brightness is shifted closer to ring ansae (for small phase angles). Moreover, according to simulations, the axisymmetric oscillations may coexist with the inclined selfgravity wake structures, which can lead to complicated photometric behavior as a function of illumination and viewing geometries, depending on properties of the simulated system. For example, at low viewing elevations, the vertical thickenings associated with the density crests should cast shadows on the nearby ring particles (see Fig. 1 for an example; darker areas are due to shadows, not due to depletion of particles). Though these shadows would be unresolved, they might still affect the integrated brightness at certain geometries. The overstable systems may also exhibit amplitude variations (in km-scales), arising from the mutual beating patterns of the basic sub-km overstable oscillations [3]. Such modulations of oscillation amplitude may lead to associated brightness variations. New results of photometric modeling of viscously overstable dynamical simulations systems are reported, related to the above mentioned topics. The Monte Carlo method of [5] is used, previously applied to modeling of

  7. Saturn Ring Radiation Environment for the Cassini Grand Finale Orbits

    Science.gov (United States)

    Cooper, John F.; Kollmann, Peter; Johnson, Robert E.; Roussos, Elias; Sittler, Edward C.; Sturner, Steven J.

    2016-10-01

    protons. Work is in progress to model these responses, particularly for gamma rays which could be decisive in confirmation of the total ring mass. We also consider prospects for detection of the innermost Van Allen belt of Saturn inwards of the D ring.

  8. On the vertical wind shear of Saturn's Equatorial Jet at cloud level

    Science.gov (United States)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.

    2005-08-01

    With the aim of retrieving the altitude of cloud features used as zonal wind tracers in Saturn's atmosphere, we have reanalyzed three different sets of photometric and calibrated data corresponding to the Voyager epoch 1979-1981 (ground-based in 1979, Voyager 2 PPS and ISS observations in 1981), and we have analyze a new set of Hubble Space Telescope images for 2004. This analysis is put in the perspective of our previous HST study for 1994-2003 (Pérez-Hoyos et al., Icarus, 176, 155. 2005). A common result is found that the individual cloud tracers are embedded within a variable tropospheric haze. According to our models, the Voyager 2 ISS images locate the cloud tracers moving with zonal velocities of 455 to 465 (± 2) m/s at a pressure level of 360 ± 140 mbar. For HST observations, the cloud tracers moving with zonal wind speeds of 280 ± 10 m/s, locate at a pressure level of about 50 ± 10 mbar. All these values are calculated in the latitude 3 deg North. The speed difference, if interpreted as a vertical wind shear (Porco et al., Science, 307, 1226. 2005), requires a change of 90 m/s per scale height, two times greater than that estimated from Cassini CIRS data (Flasar et al., Science, 307, 1247, 2005). We also perform an initial guess on Cassini ISS vertical sounding levels, retrieving values compatible with the HST ones but not with Voyager wind measurements. We conclude that the wind speed velocity differences measured between 1979-81 and 2004 in the upper troposphere cannot be solely explained as a wind shear effect and demand dynamical processes. We discuss the possible action of Rossby waves or an intrinsic circulation change in the ammonia cloud layer and above, following a large period of equatorial storm activity. Acknowledgments: This work was supported by MCYT AYA2003-03216, FEDER, and Grupos UPV 15946/2004. S.P.-H. acknowledges a PhD fellowship from the Spanish MEC and R. H. a post-doc contract from Gobierno Vasco.

  9. Habitability potential of satellites around Jupiter and Saturn

    Science.gov (United States)

    Coustenis, Athena; Raulin, Francois; Encrenaz, Therese; Grasset, Olivier; Solomonidou, Anezina

    2016-07-01

    In looking for habitable conditions in the outer solar system recent research focuses on the natural satellites rather than the planets themselves. Indeed, the habitable zone as traditionally defined may be larger than originally conceived. The outer solar system satellites provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the ground but also by the Voyager, Galileo and the Cassini spacecrafts revealed the potential of these satellites in this context, and our understanding of habitability in the solar system and beyond can be greatly enhanced by investigating several of these bodies together [1]. Their environments seem to satisfy many of the "classical" criteria for habitability (liquid water, energy sources to sustain metabolism and chemical compounds that can be used as nutrients over a period of time long enough to allow the development of life). Indeed, several of the moons show promising conditions for habitability and the development and/or maintenance of life. The strong gravitational pull caused by the giant planets may produce enough energy to sufficiently heat the cores of orbiting icy moons. Europa and Ganymede may be hiding, under their icy crust, putative undersurface liquid water oceans [2] which, in the case of Europa [3], may be in direct contact with a silicate mantle floor and kept warm by tidally generated heat [4]. Titan and Enceladus, Saturn's satellites, were found by the Cassini-Huygens mission to possess active organic chemistries with seasonal variations, unique geological features and possibly internal liquid water oceans. Titan's rigid crust and the probable existence of a subsurface ocean create an analogy with terrestrial-type plate tectonics, at least surficial [5], while Enceladus' plumes find an analogue in geysers. As revealed by Cassini the liquid hydrocarbon lakes [6] distributed mainly at polar latitudes on Titan are ideal isolated environments to look for

  10. Interactive Visualization of Shadow Effects in the Planetary System of Saturn, its Rings and its Moons using an OpenGL Shader in IDL

    Science.gov (United States)

    Fajardo Hernandez, E. M.; Pomarède, D.

    2012-09-01

    The planetary system of Saturn, its rings and its moons is a fantastic playground where physicists are confronting theories and observations. Since its insertion into orbit in 2004, the Cassini-Huygens spacecraft has returned a wealth of high-resolution images and data that calls for the development of dedicated interactive, immersive, three-dimensional, multi-purpose analysis and visualization tools. Alongside with observations, numerical simulations also provide new insights into the fundamental processes at stake in the formation of this system. The SDvision graphical interface, developed in the context of IDL Object Graphics and intended primarily for the visualization of complex and massive astrophysical plasma simulations, has been extended to provide an interactive visualization of both numerical simulations and observations of Saturn, its rings, and its moons. One major missing feature of IDL Object Graphics is the ability to render shadow effects at all. We have overcome this limitation by developing a custom GLSL Shader that is invoked by IDL objects. This Shader, based on purely geometrical computations, is fast and allows for seamless exploratory visualization of the planetary system.

  11. Tilting Saturn without Tilting Jupiter or Ejecting an Ice Giant: Constraints on migration

    Science.gov (United States)

    McNeil, Douglas S.; Lee, M. H.

    2010-10-01

    The obliquities of the giant planets preserve information about their migration and encounter histories. Are the classic Nice models (Tsiganis et al. 2005) or the resonant Nice models (Morbidelli et al. 2007) compatible with Jupiter's 3 degree tilt and Saturn's 27? Here we consider the obliquity evolution of the giants during the planetesimal-driven migration phase using two methods: (1) a purely secular integration of the Laplace-Lagrange equations with spin, and (2) a hybrid N-body scheme with full interactions between the Sun and the giants but imposed prescriptions for migration and eccentricity and inclination damping. We find that it is difficult to reproduce today's obliquity values as migration timescales sufficient to tilt Saturn via the Hamilton & Ward (2004) secular spin-orbit resonance mechanism generally suffice to tilt Jupiter more than is observed. Moreover, long migration timescales which make tilting Saturn easier simultaneously reduce the survival fraction (to below 20% for timescales longer than 20 Myr.) We discuss the constraints these observations provide on the dynamical history of the giant planets, and the remaining possibility of tilting Saturn during a late very slow migration of Neptune to its present location after the main phase of migration is complete. [This work was supported by Hong Kong RGC grant HKU 7024/08P.

  12. Computer simulation of Saturn 5 response to pre-launch wind loads

    Science.gov (United States)

    Coffin, T.

    1970-01-01

    A digital computer program is described which was developed to estimate Saturn 5 response to prelaunch wind conditions at Cape Kennedy. The program computes displacement and bending moment statistics as a function of parameters defining the atmospheric environment. A sample problem is provided to illustrate utilization of the program.

  13. Saturn's moon Phoebe as a captured body from the outer Solar System.

    Science.gov (United States)

    Johnson, Torrence V; Lunine, Jonathan I

    2005-05-05

    The orbital properties of Phoebe, one of Saturn's irregular moons, suggest that it was captured by the ringed planet's gravitational field rather than formed in situ. Phoebe's generally dark surface shows evidence of water ice, but otherwise the surface most closely resembles that of C-type asteroids and small outer Solar System bodies such as Chiron and Pholus that are thought to have originated in the Kuiper belt. A close fly-by of Phoebe by the Cassini-Huygens spacecraft on 11 June 2004 (19 days before the spacecraft entered orbit around Saturn) provided an opportunity to test the hypothesis that this moon did not form in situ during Saturn's formation, but is instead a product of the larger protoplanetary disk or 'solar nebula'. Here we derive the rock-to-ice ratio of Phoebe using its density combined with newly measured oxygen and carbon abundances in the solar photosphere. Phoebe's composition is close to that derived for other solar nebula bodies such as Triton and Pluto, but is very different from that of the regular satellites of Saturn, supporting Phoebe's origin as a captured body from the outer Solar System.

  14. How tides get dissipated in Saturn? A question probably answerable by Cassni

    Science.gov (United States)

    Luan, Jing

    2017-06-01

    Tidal dissipation inside a giant planet is important in understanding the orbital evolutions of its natural satellites and perhaps some of the extrasolar giant planets. The tidal dissipation is conventionally parameterized by the tidal quality factor, Q. The corresponding tidal torque declines rapidly with distance adopting constant Q. However, the current fast migration rates of some Saturnian satellites reported by Lainey et al. (2015) conflict this conventional conceptual belief. Alternatively, resonance lock between a satellite and an internal oscillation mode or wave of Saturn, proposed by Fuller et al. (2016), could naturally match the observational migration rates. However, the question still remains to be answered what type of mode or wave is locked with each satellite. There are two candidates for resonance lock, one is gravity mode, and the other is inertial wave attractor. They generate very different gravity acceleration anomaly near the surface of Saturn, which may be distinguishable by the data to be collected by Cassini during its proximal orbits between April and September, 2017. Indicative information about the interior of Saturn may be extracted since the existence of both gravity mode and inertial wave attractor depends on the internal structure of Saturn.

  15. USM3D Simulations of Saturn V Plume Induced Flow Separation

    Science.gov (United States)

    Deere, Karen; Elmlilgui, Alaa; Abdol-Hamid, K. S.

    2011-01-01

    The NASA Constellation Program included the Ares V heavy lift cargo vehicle. During the design stage, engineers questioned if the Plume Induced Flow Separation (PIFS) that occurred along Saturn V rocket during moon missions at some flight conditions, would also plague the newly proposed rocket. Computational fluid dynamics (CFD) was offered as a tool for initiating the investigation of PIFS along the Ares V rocket. However, CFD best practice guidelines were not available for such an investigation. In an effort to establish a CFD process and define guidelines for Ares V powered simulations, the Saturn V vehicle was used because PIFS flight data existed. The ideal gas, computational flow solver USM3D was evaluated for its viability in computing PIFS along the Saturn V vehicle with F-1 engines firing. Solutions were computed at supersonic freestream conditions, zero degree angle of attack, zero degree sideslip, and at flight Reynolds numbers. The effects of solution sensitivity to grid refinement, turbulence models, and the engine boundary conditions on the predicted PIFS distance along the Saturn V were discussed and compared to flight data from the Apollo 11 mission AS-506.

  16. Forces and Phases: An Investigation of Azimuthal Plasma and Field Periodicities in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Ramer, K. M.; Kivelson, M. G.; Khurana, K. K.; Sergis, N.; Walker, R. J.; Jia, X.

    2012-12-01

    In Saturn's magnetosphere, periodic fluctuations are ubiquitous; for example, periodicities have been observed in Saturn Kilometric Radiation (SKR), in auroral emissions, in magnetic perturbations, in electron density, and in energetic particle fluxes. In this study, we extend the search for periodicities at Saturn by examining additional plasma and magnetic field parameters in Saturn's inner magnetosphere near the equatorial plane. Our study uses data acquired by the Cassini spacecraft during the equatorial passes from Oct 11, 2005 to May 24, 2006. We have found that the intermittency of in situ measurements in the inner magnetosphere precludes the use of the frequency sweeping technique adopted by Gurnett et al. [2007] to establish the optimum rotation period. We, therefore, use rotation periods already in use: first the slowly changing SLS3 period based on SKR measurements, and second the period based on the magnetic field [Provan et al., 2011], to establish phases and obtain evidence that magnetic pressure, plasma pressure, density, and angular velocity are periodically modulated. We then establish the phase relationships among these parameters to test azimuthal force balance and we compare these results to simulations by Jia et al. [2012].

  17. Cassini Observations During the Saturn Auroral Campaign of Spring 2013 (Invited)

    Science.gov (United States)

    Kurth, W. S.; Lamy, L.; Gurnett, D. A.; Mitchell, D. G.; Dougherty, M. K.; Bunce, E. J.; Badman, S. V.; Burton, M. E.; Crary, F. J.; Pryor, W. R.; Baines, K. H.; Dyudina, U.; Nichols, J. D.; Stallard, T.; Luhmann, J. G.; Zheng, Y.; Hansen, K. C.

    2013-12-01

    During April and May 2013, a concerted effort to study Saturn's auroras was mounted using multi-wavelength observations from Cassini and a number of Earth-based observations. This paper will focus on the Cassini observations acquired during the campaign with an emphasis on the fields and particle observations and Saturn Kilometric Radiation, in particular. It has been shown that the integrated power of Saturn Kilometric Radiation (SKR) provides a good proxy for auroral activity and there is at least a qualitative correlation between auroral brightness and SKR intensity. While the SKR observations can be complicated by beaming issues, they provide a reasonable, continuous context within which to place other observations. We compare the time history of SKR intensity with models of the solar wind input based on models which propagate 1 AU observations to the distance of Saturn. Further, direction-finding measurements of the SKR reveal the source of the SKR and these can be related to Earth-based and Cassini-based observations of the auroras. In this paper we will use the SKR observations to construct the evolution of auroral activity and place other in situ and remote sensing observations within this context.

  18. Gaseous toroid around Saturn. [Saturnian ring system for atomic hydrogen trapping in Titan atmospheric model

    Science.gov (United States)

    Mcdonough, T. R.

    1974-01-01

    The trapping of Titan's escaping atmosphere in the Saturnian system by a toroidal ring is discussed. The radius of the toroid is comparable to Titan's orbit, or about ten times larger than the visible rings. Theoretical atmospheric models are formulated that consider Saturn's gravitational attraction and magnetospheric properties in forming this toroid and in protecting toroid particles from direct ionization by solar wind particles.

  19. Formation of fine dust on Saturn's rings as suggested by the presence of spokes

    Science.gov (United States)

    Smoluchowski, R.

    1983-01-01

    The common interpretation of spokes on the B ring of Saturn is that they are the result of light scattered by electrostatically levitated micrometer- and submicrometer-size dust particles. The origin of this dust in terms of radiation-induced thermal fatigue and collisions between the particles of the ring as well as meteoritic bombardment is investigated.

  20. The deuterium abundance in Jupiter and Saturn from ISO-SWS observations

    NARCIS (Netherlands)

    Lellouch, E; Bezard, B; Fouchet, T; Feuchtgruber, H; Encrenaz, T; de Graauw, T

    2001-01-01

    Observations with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) are used to determine the D/H ratio in Jupiter's and Saturn's atmospheres. The D/H ratio is measured independently in hydrogen (i.e. from the HD/H-2 ratio) and methane (from CH3D/CH4). Observations

  1. The deuterium abundance in Jupiter and Saturn from ISO-SWS observations

    NARCIS (Netherlands)

    Lellouch, E; Bezard, B; Fouchet, T; Feuchtgruber, H; Encrenaz, T; de Graauw, T

    Observations with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) are used to determine the D/H ratio in Jupiter's and Saturn's atmospheres. The D/H ratio is measured independently in hydrogen (i.e. from the HD/H-2 ratio) and methane (from CH3D/CH4). Observations

  2. VizieR Online Data Catalog: MIR brightness contrast of Saturn's rings (Fujiwara+, 2017)

    Science.gov (United States)

    Fujiwara, H.; Morishima, R.; Fujiyoshi, T.; Yamashita, T.

    2016-11-01

    Brightness maps for Saturn's rings at 8.8, 9.7, 10.5, 11.7, 12.5, 17.7, 18.8, 20.5, and 24.5 micron observed with Subaru Telescope/COMICS in 2008 and at 12.5 and 24.5 micron in 2005 are provides as fits files. (2 data files).

  3. A Statistical Study of Injection/Dispersion Events in Saturn's Inner Magnetosphere

    Science.gov (United States)

    Chen, Y.; Hill, T. W.

    2007-12-01

    In the inner magnetosphere of a rapidly rotating planet like Jupiter or Saturn, radial transport of plasma is mainly composed of hot, tenuous plasma moving inward and cold, denser plasma moving outward. The drift dispersion of injecting hot plasma provides direct evidence for this convective process. The Cassini Plasma Spectrometer (CAPS) has frequently reported observations of such injection/dispersion events [e.g., Burch et al., 2005 GRL L14S02; Hill et al., 2005 GRL L14S10]. Based on the study of Hill et al., the analysis of the properties of such signatures is continued in this paper, with a much larger data set of 26 Cassini orbits of Saturn, extending from July 2004 to August 2006. A statistical picture of the injection/dispersion characteristics is developed, indicating the distributions of ages, time scales and length scales. Moreover, an interesting rotational modulation of occurrence frequency is present in the Voyager-era Saturn Longitude System (SLS), but not in the Cassini-era Saturn Kilometric Radiation (SKR) system. A periodogram analysis using the Lomb-Scargle algorithm is underway to provide the accurate information of the recurrence period. Preliminary results show multiple-peaks in the period window near 11 hours.

  4. Tethys and Dione as sources of outward-flowing plasma in Saturn's magnetosphere.

    Science.gov (United States)

    Burch, J L; Goldstein, J; Lewis, W S; Young, D T; Coates, A J; Dougherty, M K; André, N

    2007-06-14

    Rotating at over twice the angular speed of Earth, Saturn imposes a rapid spin on its magnetosphere. As a result, cold, dense plasma is believed to be flung outward from the inner magnetosphere by centrifugal force and replaced by hotter, more tenuous plasma from the outer magnetosphere. The centrifugal interchange of plasmas in rotating magnetospheres was predicted many years ago and was conclusively demonstrated by observations in Jupiter's magnetosphere, which--like that of Saturn (but unlike that of Earth)--is rotationally dominated. Recent observations in Saturn's magnetosphere have revealed narrow injections of hot, tenuous plasma believed to be the inward-moving portion of the centrifugal interchange cycle. Here we report observations of the distribution of the angle between the electron velocity vector and the magnetic field vector ('pitch angle') obtained in the cold, dense plasma adjacent to these inward injection regions. The observed pitch-angle distributions are indicative of outward plasma flow and consistent with centrifugal interchange in Saturn's magnetosphere. Further, we conclude that the observed double-peaked ('butterfly') pitch-angle distributions result from the transport of plasma from regions near the orbits of Dione and Tethys, supporting the idea of distinct plasma tori associated with these moons.

  5. Kronoseismology: Using density waves in Saturn's C ring to probe the planet's interior

    CERN Document Server

    Hedman, M M

    2013-01-01

    Saturn's C ring contains multiple spiral patterns that appear to be density waves driven by periodic gravitational perturbations. In other parts of Saturn's rings, such waves are generated by Lindblad resonances with Saturn's various moons, but most of the wave-like C-ring features are not situated near any strong resonance with any known moon. Using stellar occultation data obtained by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft, we investigate the origin of six unidentified C-ring waves located between 80,900 and 87,200 km from Saturn's center. By measuring differences in the waves' phases among the different occultations, we are able to determine both the number of arms in each spiral pattern and the speeds at which these patterns rotate around the planet. We find that all six of these waves have between 2 and 4 arms and pattern speeds between 1660 degrees/day and 1861 degrees/day. These speeds are too large to be attributed to any satellite resonance. Instead they ar...

  6. A Study of Saturn's Normal Mode Oscillations and Their Forcing of Density Waves in the Rings

    Science.gov (United States)

    Friedson, Andrew James; Cao, Lyra

    2016-10-01

    Analysis of Cassini Visual and Infrared Mapping Spectrometer (VIMS) ring occultation profiles has revealed the presence of spiral density waves in Saturn's C ring that are consistent with being driven by gravitational perturbations associated with normal-mode oscillations of the planet [1]. These waves allow the C ring to serve as a sort of seismometer, since their pattern speeds (i.e., azimuthal phase speeds) can in principle be mapped onto the frequencies of the predominant normal oscillations of the planet. The resonant mode frequencies in turn are sensitive to Saturn's internal structure and rotational state. Characterization of the normal modes responsible for the forcing holds the potential to supply important new constraints on Saturn's internal structure and rotation. We perform numerical calculations to determine the resonant frequencies of the normal modes of a uniformly rotating planet for various assumptions regarding its internal stratification and compare the implied pattern speeds to those of density waves observed in the C ring. A question of particular interest that we address is whether quasi-toroidal modes are responsible for exciting a mysterious class of slowly propagating density waves in the ring. We also explore the implications of avoided crossings between modes for explaining observed fine splitting in the pattern speeds of spiral density waves having the same number of spiral arms, and weigh the role that convective overstability may play in exciting large-scale quasi-toroidal modes in Saturn. [1] Hedman, M.M. and Nicholson, P.D. 2014. MNRAS 444, 1369.

  7. Explorer of Enceladus and Titan (E2T): Investigating the habitability and evolution of ocean worlds in the Saturn system

    Science.gov (United States)

    Mitri, Giuseppe; Postberg, Frank; Soderblom, Jason M.; Tobie, Gabriel; Tortora, Paolo; Wurz, Peter; Barnes, Jason W.; Coustenis, Athena; Ferri, Francesca; Hayes, Alexander; Hayne, Paul O.; Hillier, Jon; Kempf, Sascha; Lebreton, Jean-Pierre; Lorenz, Ralph; Orosei, Roberto; Petropoulos, Anastassios; Yen, Chen-wan; Reh, Kim R.; Schmidt, Jürgen; Sims, Jon; Sotin, Christophe; Srama, Ralf

    2016-10-01

    The NASA-ESA-ASI Cassini-Huygens mission has revealed Titan and Enceladus to be two of the most enigmatic worlds in the Solar System. Titan, with its organically rich and dynamic atmosphere and geology, and Enceladus, with its active plume of water vapor and ice laced with organics, salts, and silica nano-particles, both harbouring subsurface oceans, are prime environments in which to investigate the conditions for the emergence of life and the habitability potential of ocean worlds as well as the origin and evolution of unique complex planetary systems. Explorer of Enceladus and Titan (E2T) is a space mission concept dedicated to investigating the evolution and habitability of these Saturnian satellites and is proposed as a medium-class mission led by ESA in collaboration with NASA in response to ESA's M5 Cosmic Vision Call. E2T has a focused state-of-the-art adapted payload that will provide in-situ sampling, high-resolution imaging and radio science measurements from multiple flybys of Enceladus and Titan using a solar-electric powered spacecraft in orbit around Saturn. With significant improvements in mass range and resolution, as compared with Cassini, the Ion and Neutral Gas Mass Spectrometer (INMS) and the Enceladus Icy Jet Analyzer (ENIJA) time of flight mass spectrometers will provide the data needed to decipher the subtle details of the aqueous environment of Enceladus from plume sampling and of the complex pre-biotic chemistry occurring in Titan's atmosphere. The Titan Imaging and Geology, Enceladus Reconnaissance (TIGER) mid-wave infrared camera will map thermal emission from Enceladus' tiger stripes at meter scales and investigate Titan's geology and compositional variability at decameter scales. The Radio Science Experiment (RSE) measurements will provide constraints on the ice shell structure and the properties of the internal oceans of Enceladus and Titan. We will present the concept and discuss the major improvements to our understanding of these

  8. Ground-based observations of Saturn's H3+ aurora and ring rain from Keck in 2013

    Science.gov (United States)

    O'Donoghue, J.; Melin, H.; Stallard, T.; Provan, G.; Moore, L.; Badman, S. V.; Baines, K. H.; Miller, S.; Cowley, S. W. H.

    2014-12-01

    The ground-based 10-metre Keck telescope was used to probe Saturn's H3+ ionosphere in 2013. The slit on the high resolution near infrared spectrometer (NIRSPEC; (R~25,000) was aligned pole-to-pole along Saturn's rotational axis at local noon. This is also aligned (within uncertainties) to the effectively dipolar magnetic field. Four polar/auroral regions of Saturn's ionosphere were measured simultaneously as the planet rotated: 1) the northern noon main auroral oval; 2) the northern midnight main oval; 3) the northern polar cap and 4) the southern main oval at noon. The results here contain twenty-three H3+ temperatures, column densities and total emissions located at the above regions spread over timescales of both hours and days. The main findings of this study are that ionospheric temperatures in the northern main oval are cooler than their southern counterparts by tens of K; supportive of the hypothesis that the total thermospheric heating rate (Joule heating and ion drag) is inversely proportional to magnetic field strength. The main oval H3+ density and emission is lower at northern midnight than at noon, and this is in agreement with an electron influx peaking at 08:00 Saturn local time and having a minimum at midnight. When ordering the northern main oval parameters of H3+ as a function of the oscillation period seen in Saturn's magnetic field - the planetary period oscillation (PPO) phase - we see a large peak in H3+ density and emission at ˜110° phase, with a full-width at half-maximum (FWHM) of ˜40°. This seems to indicate that the influx of electrons associated with the PPO phase at 90° is responsible at least in part for the behavior of all H3+ parameters. In addition to the auroral/polar data we also present the latest results from observations of Saturn's mid-to-low latitude H3+ emission. This emission is thought to be modulated by charged water product influx which flows into the planet along magnetic field lines from Saturn's rings, i.e. ring

  9. Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Observations of Dust Content

    Science.gov (United States)

    Edgington, Scott G.; Atreya, Sushil K.; Wilson, Eric; Baines, Kevin; West, Robert; Bjoraker, Gordon; Fletcher, Leigh N.; Momary, Thomas W.

    2016-10-01

    Cassini has been orbiting Saturn for over twelve years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere with solar inclination of 24 degrees to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds.Previous work examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn's stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. We assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere.We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze.The research described in this paper was carried out

  10. Strong Tidal Dissipation in Saturn and Constraints on Enceladus' Thermal State from Astrometry

    Science.gov (United States)

    Lainey, Valéry; Karatekin, Özgür; Desmars, Josselin; Charnoz, Sébastien; Arlot, Jean-Eudes; Emelyanov, Nicolai; Le Poncin-Lafitte, Christophe; Mathis, Stéphane; Remus, Françoise; Tobie, Gabriel; Zahn, Jean-Paul

    2012-06-01

    Tidal interactions between Saturn and its satellites play a crucial role in both the orbital migration of the satellites and the heating of their interiors. Therefore, constraining the tidal dissipation of Saturn (here the ratio k 2/Q) opens the door to the past evolution of the whole system. If Saturn's tidal ratio can be determined at different frequencies, it may also be possible to constrain the giant planet's interior structure, which is still uncertain. Here, we try to determine Saturn's tidal ratio through its current effect on the orbits of the main moons, using astrometric data spanning more than a century. We find an intense tidal dissipation (k 2/Q = (2.3 ± 0.7) × 10-4), which is about 10 times higher than the usual value estimated from theoretical arguments. As a consequence, eccentricity equilibrium for Enceladus can now account for the huge heat emitted from Enceladus' south pole. Moreover, the measured k 2/Q is found to be poorly sensitive to the tidal frequency, on the short frequency interval considered. This suggests that Saturn's dissipation may not be controlled by turbulent friction in the fluid envelope as commonly believed. If correct, the large tidal expansion of the moon orbits due to this strong Saturnian dissipation would be inconsistent with the moon formations 4.5 Byr ago above the synchronous orbit in the Saturnian subnebulae. But it would be compatible with a new model of satellite formation in which the Saturnian satellites formed possibly over a longer timescale at the outer edge of the main rings. In an attempt to take into account possible significant torques exerted by the rings on Mimas, we fitted a constant rate da/dt on Mimas' semi-major axis as well. We obtained an unexpected large acceleration related to a negative value of da/dt = -(15.7 ± 4.4) × 10-15 AU day-1. Such acceleration is about an order of magnitude larger than the tidal deceleration rates observed for the other moons. If not coming from an astrometric

  11. STRONG TIDAL DISSIPATION IN SATURN AND CONSTRAINTS ON ENCELADUS' THERMAL STATE FROM ASTROMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Lainey, Valery; Desmars, Josselin; Arlot, Jean-Eudes; Emelyanov, Nicolai; Remus, Francoise [IMCCE-Observatoire de Paris, UMR 8028 du CNRS, UPMC, 77 Av. Denfert-Rochereau, 75014 Paris (France); Karatekin, Oezguer [Royal Observatory of Belgium, Avenue Circulaire 3, 1180 Uccle, Bruxelles (Belgium); Charnoz, Sebastien; Mathis, Stephane [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SAp Centre de Saclay, 91191 Gif-sur-Yvette (France); Le Poncin-Lafitte, Christophe [SyRTE-Observatoire de Paris, UMR 8630 du CNRS, 77 Av. Denfert-Rochereau, 75014 Paris (France); Tobie, Gabriel [Laboratoire de Planetologie et Geodynamique de Nantes, Universite de Nantes, CNRS, UMR 6112, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Zahn, Jean-Paul, E-mail: lainey@imcce.fr [LUTH-Observatoire de Paris, UMR 8102 du CNRS, 5 place Jules Janssen, 92195 Meudon Cedex (France)

    2012-06-10

    Tidal interactions between Saturn and its satellites play a crucial role in both the orbital migration of the satellites and the heating of their interiors. Therefore, constraining the tidal dissipation of Saturn (here the ratio k{sub 2}/Q) opens the door to the past evolution of the whole system. If Saturn's tidal ratio can be determined at different frequencies, it may also be possible to constrain the giant planet's interior structure, which is still uncertain. Here, we try to determine Saturn's tidal ratio through its current effect on the orbits of the main moons, using astrometric data spanning more than a century. We find an intense tidal dissipation (k{sub 2}/Q = (2.3 {+-} 0.7) Multiplication-Sign 10{sup -4}), which is about 10 times higher than the usual value estimated from theoretical arguments. As a consequence, eccentricity equilibrium for Enceladus can now account for the huge heat emitted from Enceladus' south pole. Moreover, the measured k{sub 2}/Q is found to be poorly sensitive to the tidal frequency, on the short frequency interval considered. This suggests that Saturn's dissipation may not be controlled by turbulent friction in the fluid envelope as commonly believed. If correct, the large tidal expansion of the moon orbits due to this strong Saturnian dissipation would be inconsistent with the moon formations 4.5 Byr ago above the synchronous orbit in the Saturnian subnebulae. But it would be compatible with a new model of satellite formation in which the Saturnian satellites formed possibly over a longer timescale at the outer edge of the main rings. In an attempt to take into account possible significant torques exerted by the rings on Mimas, we fitted a constant rate da/dt on Mimas' semi-major axis as well. We obtained an unexpected large acceleration related to a negative value of da/dt = -(15.7 {+-} 4.4) Multiplication-Sign 10{sup -15} AU day{sup -1}. Such acceleration is about an order of magnitude larger

  12. Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Observations of Dust Content

    Science.gov (United States)

    Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T.

    2016-12-01

    Cassini has been orbiting Saturn for over twelve years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere with solar inclination of 24 degrees to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds.Previous work examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn's stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. We assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere.We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze.The research described in this paper was carried out

  13. "Storm Alley" on Saturn and "Roaring Forties" on Earth: two bright phenomena of the same origin

    Science.gov (United States)

    Kochemasov, G. G.

    2009-04-01

    "Storm Alley" on Saturn and "Roaring Forties' on Earth: two bright phenomena of the same origin. G. Kochemasov IGEM of the Russian Academy of Sciences, Moscow, Russia, kochem.36@mail.ru Persisting swirling storms around 35 parallel of the southern latitude in the Saturnian atmosphere and famous "Roaring Forties" of the terrestrial hydro- and atmosphere are two bright phenomena that should be explained by the same physical law. The saturnian "Storm Alley" (as it is called by the Cassini scientists) is a stable feature observed also by "Voyager". The Earth's "Roaring Forties" are well known to navigators from very remote times. The wave planetology [1-3 & others] explains this similarity by a fact that both atmospheres belong to rotating globular planets. This means that the tropic and extra-tropic belts of these bodies have differing angular momenta. Belonging to one body these belts, naturally, tend to equilibrate their angular momenta mainly by redistribution of masses and densities [4]. But a perfect equilibration is impossible as long as a rotating body (Saturn or Earth or any other) keeps its globular shape due to mighty gravity. So, a contradiction of tropics and extra-tropics will be forever and the zone mainly between 30 to 50 degrees in both hemispheres always will be a zone of friction, turbulence and strong winds. Some echoes of these events will be felt farther poleward up to 70 degrees. On Earth the Roaring Forties (40˚-50˚) have a continuation in Furious Fifties (50˚-60˚) and Shrieking (Screaming) Sixties (below 60˚, close to Antarctica). Below are some examples of excited atmosphere of Saturn imaged by Cassini. PIA09734 - storms within 46˚ south; PIA09778 - monitoring the Maelstrom, 44˚ north; PIA09787 - northern storms, 59˚ north; PIA09796 - cloud details, 44˚ north; PIA10413 - storms of the high north, 70˚ north; PIA10411 - swirling storms, "Storm Alley", 35˚ south; PIA10457 - keep it rolling, "Storm Alley", 35˚ south; PIA10439 - dance

  14. Seasons on Saturn. II. Influence of solar activity on variation of methane absorption

    Science.gov (United States)

    Vidmachenko, A. P.

    2015-10-01

    Methane and ammonia in the atmosphere of Saturn are in the form of impurities at the level of less than tenths of a percentage. They take part in photochemical processes, the main products of which are hydrocarbons and ammonia NH3. Polyacetylenes absorb sunlight almost to 400 nm, and hydrocarbons distribution over the disk of Saturn for 1964-2012 showed a significant seasonal changes in the levels of visible clouds and above clouds haze. Changes of methane absorption along the meridian in the equinox 1966 and 1995, had the opposite course to the results in equinox 1980. But the expected differences in the change of methane absorption at the equinox 2009, similar to 1980, did not happen. Although all the physical and orbital characteristics of Saturn at equinoxes in these moments repeated, but the response to them were received various. A few years before the equinox in 1966, 1980 and 1995, the number of R, characterizing solar activity, varied from 40 to 180. Before equinox 2009 the Sun has minimal activity and the R value was practically zero. According to observations at the time of equinox 2009, convection in the Saturn's atmosphere stayed at a minimal level. After exiting of rings shadows in winter northern hemisphere deep cloud layer was "frozen" at the same low level at absence of active processes on the Sun. This allowed easily to register a thick layer of methane and ammonia gas. So how such haze has a photochemical nature, it can be assumed that due to minimum of solar activity, in the Saturn’s atmosphere was not enough energy for formation of photochemical aerosol layer. Because of such a set of physical and chemical conditions in Saturn's atmosphere, and low-activity in winter hemisphere, the methane absorption remained almost unchanged and equal to the absorption in the former summer hemisphere with maximum irradiated sunlight.

  15. Synergism of Saturn, Enceladus and Titan and Formation of HCNO Exobiological Molecules

    Science.gov (United States)

    Sittler, Edward C., Jr.; Cooper, John F.

    2010-01-01

    Saturn as a system has two very exotic moons Titan and Enceladus. Titan with energy input from Saturn's magnetosphere, solar UV irradiation, and cosmic rays can make HCN based molecules as discussed in earlier paper by [1]. Space radiation effects at both moons, and as coupled by the Saturn magnetosphere could cause an unexpected series of events leading to the evolution of biological models at Titan composed of HCNO with oxygen as the new ingredient. The "Old Faithful" model by [2] suggests that Enceladus, highly irradiated by Saturn magnetospheric electrons, has episodic ejections of water vapor driven by radiolytic oxidation gas products into Saturn's magnetosphere. At Titan Cassini discovered 1) that keV oxygen ions, evidently from Enceladus, are bombarding Titan's upper atmosphere [3] and 2) the discovery of heavy positive and negative ions within Titan's upper atmosphere [4]. Initial models of heavy ion formation in Titan's upper atmosphere invoked polymerization of aromatics such as Benzenes and their radicals to make PAHs [5], while a more recent model by [6] has raised the possibility of carbon chains forming from the polymerization of acetylene and its radicals to eventually make fullerenes. Laboratory measurements indicate that fullerenes, which are hollow carbon shells, can trap the keV oxygen and with the clustering of fullerenes and possible mixture with PAHs, some with nitrogen molecules, can make the larger aerosols with oxygen within them. Then with further ionizing irradiation from cosmic rays deep in the atmosphere "tholin" molecules are produced with all the molecular components present from which organic molecules can form. Among the molecular components are amino acids, the fundamental building blocks of life as we know it. This process maybe a common chemical pathway, both at the system level and at the molecular level, to form prebiotic and perhaps even biotic molecules. Such processes can be occurring throughout our universe, such as

  16. Innermost Van Allen Radiation Belt for High Energy Protons at Saturn

    Science.gov (United States)

    Cooper, John F.

    2008-01-01

    The high energy proton radiation belts of Saturn are energetically dominated by the source from cosmic ray albedo neutron decay (CRAND), trapping of protons from beta decay of neutrons emitted from galactic cosmic ray nuclear interactions with the main rings. These belts were originally discovered in wide gaps between the A-ring, Janus/Epimetheus, Mimas, and Enceladus. The narrow F and G rings significant affected the CRAND protons but did not produce total depletion. Voyager 2 measurements subsequently revealed an outermost CRAND proton belt beyond Enceladus. Although the source rate is small, the trapping times limited by radial magnetospheric diffusion are very long, about ten years at peak measured flux inwards of the G ring, so large fluxes can accumulate unless otherwise limited in the trapping region by neutral gas, dust, and ring body interactions. One proposed final extension of the Cassini Orbiter mission would place perikrone in a 3000-km gap between the inner D ring and the upper atmosphere of Saturn. Experience with CRAND in the Earth's inner Van Allen proton belt suggests that a similar innermost belt might be found in this comparably wide region at Saturn. Radial dependence of magnetospheric diffusion, proximity to the ring neutron source, and northward magnetic offset of Saturn's magnetic equator from the ring plane could potentially produce peak fluxes several orders of magnitude higher than previously measured outside the main rings. Even brief passes through such an intense environment of highly penetrating protons would be a significant concern for spacecraft operations and science observations. Actual fluxes are limited by losses in Saturn's exospheric gas and in a dust environment likely comparable to that of the known CRAND proton belts. The first numerical model of this unexplored radiation belt is presented to determine limits on peak magnitude and radial profile of the proton flux distribution.

  17. Spinning, Breathing, and Flapping: The Changing Size and Shape of Saturn's Middle Magnetosphere

    Science.gov (United States)

    Ramer, K. M.; Kivelson, M.; Sergis, N.; Khurana, K. K.; Jia, X.; Strangeway, R. J.

    2014-12-01

    In Saturn's magnetosphere, periodic fluctuations are observed in Saturn Kilometric Radiation (SKR), auroral emissions, magnetic field, electron density, and energetic particle fluxes. We have extended previous Cassini investigations at Saturn by characterizing periodicities in additional plasma and magnetic field properties in Saturn's middle magnetosphere near the equatorial plane. It is customary to model perturbations in the middle magnetosphere as if they rotate rigidly, but we find that this assumption does not work well for all properties of interest and that the phase dependence of the perturbations may vary with radius and local time. We use a magnetohydrodynamic (MHD) simulation [Jia et al., 2012], which generates a rotating pattern of field aligned currents centered at 70° invariant latitude in Saturn's southern ionosphere that impose periodic variations on the entire magnetosphere, to understand how the changing size and shape affects the observed properties. In particular, we find that the dayside magnetopause roughly follows the 80 invariant latitude field lines as they move in and out. We identify three different modes of magnetospheric periodicity linked to rotation (spinning), compression (breathing), and north-south motion (flapping). All have the same ~10.7 hour period, but impose significant changes at phases that depend on the plasma property considered and the location of the measurement. Multiple modes acting concurrently can produce distinctly non-sinusoidal waveforms of the variations of plasma parameters through a rotation cycle. Within limitations of data coverage, we find good agreement between the simulation and the data in the rotation phase modulation of magnetic pressure, plasma pressure, and density perturbations.

  18. Birotor dipole model for Saturn's inner magnetic field from CASSINI RPWS measurements and MAG data

    Science.gov (United States)

    Galopeau, Patrick H. M.

    2016-10-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR). These two periods were attributed to the northern and southern hemispheres respectively. The existence of a double period makes the study of the planetary magnetic field much more complicated and the building of a field model, based on the direct measurements of the MAG experiment from the magnetometers embarked on board Cassini, turns out to be uncertain. The first reason is the difficulty for defining a longitude system linked to the variable period, because the internal magnetic field measurements from MAG are not continuous. The second reason is the existence itself of two distinct periods which could imply the existence of a double rotation magnetic structure generated by Saturn's dynamo. However, the radio observations from the RPWS experiment allow a continuous and accurate follow-up of the rotation phase of the variable two periods, since the SKR emission is permanently observable and produced very close to the planetary surface. A wavelet transform analysis of the intensity of the SKR signal received at 290 kHz was performed in order to calculate the rotation phase of each Saturnian hemisphere. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to rotate around Saturn's axis at two different angular velocities; it is tilted and not centered. Then it is possible to fit the MAG data for each Cassini's revolution around the planet the periapsis of which is less than 5 Saturnian radii. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. Such a result can be used as a boundary condition for modelling and constraining the planetary dynamo.

  19. A possible influence of the Great White Spot on Saturn kilometric radiation periodicity

    Science.gov (United States)

    Fischer, G.; Ye, S.-Y.; Groene, J. B.; Ingersoll, A. P.; Sayanagi, K. M.; Menietti, J. D.; Kurth, W. S.; Gurnett, D. A.

    2014-12-01

    The periodicity of Saturn kilometric radiation (SKR) varies with time, and its two periods during the first 5 years of the Cassini mission have been attributed to SKR from the northern and southern hemisphere. After Saturn equinox in August 2009, there were long intervals of time (March 2010 to February 2011 and September 2011 to June 2012) with similar northern and southern SKR periods and locked SKR phases. However, from March to August 2011 the SKR periods were split up again, and the phases were unlocked. In this time interval, the southern SKR period slowed down by ~ 0.5% on average, and there was a large jump back to a faster period in August 2011. The northern SKR period speeded up and coalesced again with the southern period in September 2011. We argue that this unusual behavior could be related to the so-called Great White Spot (GWS), a giant thunderstorm that raged in Saturn's atmosphere around that time. For several months in 2011, the visible head of the GWS had the same period of ~ 10.69 h as the main southern SKR modulation signal. The GWS was most likely a source of intense gravity waves that may have caused a global change in Saturn's thermospheric winds via energy and momentum deposition. This would support the theory that Saturn's magnetospheric periodicities are driven by the upper atmosphere. Since the GWS with simultaneous SKR periodicity measurements have only been made once, it is difficult to prove a physical connection between these two phenomena, but we provide plausible mechanisms by which the GWS might modify the SKR periods.

  20. Overview of Cassini radio science at Saturn, Titan, and the icy satellites

    Science.gov (United States)

    Kliore, A. J.; Ambrosini, R.; Armstrong, J. W.; Flasar, F. M.; French, R. G.; Iess, L.; Marouf, E. A..; Nagy, A. F.; Rappaport, N. J.; Tortora, P.; Jpl/Dsn Radio Science Support Team

    The Cassini spacecraft which has been in orbit about Saturn for over two years is the first Radio Science platform to provide three downlink frequencies In addition to the X-band telemetry link 3 56 cm w l two other frequencies S-band 13 04 cm and Ka-band 0 94 cm are available This plus the high SNR 50 dBHz at X-band afforded by the 4 m diameter s c high gain antenna in combination with the excellent low noise receivers of the DSN as well as overall system stabilities of 1 part in 10 13 when referenced to the on-board ultra-stable oscillator USO in one-way operation and 1 part inx 10 15 for a two-way link make Cassini an unprecedented instrument of radio science The orbital tour phase of the mission has the following main radio science objectives a determination of the masses and gravity fields of Saturn s icy satellites Titan and Saturn through two-way tracking during fly-bys To date the masses of Phoebe Iapetus Dione Enceladus Rhea and Titan have been measured and will be reported here b Measurement of the structure and other properties of Saturn s rings through three-band occultation Seven near-diametric occultations at a high ring opening angle have been completed and the results will be presented here c Measurement of the vertical structure of the atmosphere and ionosphere of Saturn The same series of occultations have provided nearly equatorial observations of the atmosphere structure and the ionosphere and the results will be described here d Measurement of the vertical structure of

  1. Evolution of stratospheric chemistry in the Saturn storm beacon region

    Science.gov (United States)

    Moses, Julianne I.; Armstrong, Eleanor S.; Fletcher, Leigh N.; Friedson, A. James; Irwin, Patrick G. J.; Sinclair, James A.; Hesman, Brigette E.

    2015-11-01

    The giant northern-hemisphere storm that erupted on Saturn in December 2010 triggered significant changes in stratospheric temperatures and species abundances that persisted for more than a year after the original outburst. The stratospheric regions affected by the storm have been nicknamed "beacons" due to their prominent infrared-emission signatures (Fletcher, L.N. et al. [2011]. Science 332, 1413). The two beacon regions that were present initially merged in April 2011 to form a single, large, anticyclonic vortex (Fletcher, L.N. et al. [2012]. Icarus 221, 560). We model the expected photochemical evolution of the stratospheric constituents in the beacons from the initial storm onset through the merger and on out to March 2012. The results are compared with longitudinally resolved Cassini/CIRS spectra from May 2011. If we ignore potential changes due to vertical winds within the beacon, we find that C2H2, C2H6, and C3H8 remain unaffected by the increased stratospheric temperatures in the beacon, the abundance of the shorter-lived CH3C2H decreases, and the abundance of C2H4 increases significantly due to the elevated temperatures, the latter most notably in a secondary mixing-ratio peak located near mbar pressures. The C4H2 abundance in the model decreases by a factor of a few in the 0.01-10 mbar region but has a significant increase in the 10-30 mbar region due to evaporation of the previously condensed phase. The column abundances of C6H6 and H2O above ∼30 mbar also increase due to aerosol evaporation. Model-data comparisons show that models that consider temperature changes alone underpredict the abundance of C2Hx species by a factor of 2-7 in the beacon core in May 2011, suggesting that other processes not considered by the models, such as downwelling winds in the vortex, are affecting the species profiles. Additional calculations indicate that downwelling winds of order - 10 cm s-1 near ∼0.1 mbar need to be included in the photochemical models in order to

  2. Pioneer: First to Jupiter, Saturn, and beyond. Bibliography

    Science.gov (United States)

    1980-01-01

    The reference citatons are grouped by experiment. Experiments include: the charged particle instrument experiment; the ultraviolet photometer experiment; imaging experiments; and magnetometer experiments. The asteroid dete