WorldWideScience

Sample records for exosphere

  1. Modeling Mars' Hydrogen Exosphere

    Science.gov (United States)

    Holmstrom, M.

    2006-12-01

    Traditionally, exospheric densities and velocity distributions are modelled by spherical symmetric analytical Chamberlain functions, assuming gravity is the only force acting on the neutrals. Planetary exospheres are however not spherical symmetric to any good approximation, as evident from observations, due to non- uniformexobase conditions and effects such as photoionization, radiation pressure, charge exchange, recombination and planetary rotation. To account for these effects numerical simulations are needed. Using Monte Carlo test particle simulations it is possible to account for the above effects (if ion distributions are assumed). Even though neutrals in the exospheres by definition do not collide often, collisions occur. Especially near the exobase the transition is gradual from collision dominated regions at lower heights (with Maxwellian velocity distributions) to essentially collisionless regions at greater heights. We present exospheric simulations that include collisions self consistently using the direct simulation Monte Carlo (DSMC) approach. The code is three dimensional, parallel and uses an adaptive grid, allowing many particles to be included in the simulations, leading to accurate results. In particular, we here study Mars' hydrogen exosphere and the effects of the above processes, including thermal escape rates.

  2. The Giant Planet Satellite Exospheres

    Science.gov (United States)

    McGrath, M. A.

    2014-12-01

    Exospheres are relatively common in the outer solar system among the moons of the gas giant planets. They span the range from very tenuous, surface-bounded exospheres (e.g., Rhea, Dione) to quite robust exospheres with exobase above the surface (e.g., Io, Triton), and include many intermediate cases (e.g., Europa, Ganymede, Enceladus). The exospheres of these moons exhibit an interesting variety of sources, from surface sputtering, to frost sublimation, to active plumes, and also well illustrate another common characteristic of the outer planet satellite exospheres, namely, that the primary species often exists both as a gas in atmosphere, and a condensate (frost or ice) on the surface. As described by Yelle et al. (1995) for Triton, "The interchange of matter between gas and solid phases on these bodies has profound effects on the physical state of the surface and the structure of the atmosphere." A brief overview of the exospheres of the outer planet satellites will be presented, including an inter-comparison of these satellites exospheres with each other, and with the exospheres of the Moon and Mercury.

  3. Lunar exospheric argon modeling

    Science.gov (United States)

    Grava, Cesare; Chaufray, J.-Y.; Retherford, K. D.; Gladstone, G. R.; Greathouse, T. K.; Hurley, D. M.; Hodges, R. R.; Bayless, A. J.; Cook, J. C.; Stern, S. A.

    2015-07-01

    Argon is one of the few known constituents of the lunar exosphere. The surface-based mass spectrometer Lunar Atmosphere Composition Experiment (LACE) deployed during the Apollo 17 mission first detected argon, and its study is among the subjects of the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) and Lunar Atmospheric and Dust Environment Explorer (LADEE) mission investigations. We performed a detailed Monte Carlo simulation of neutral atomic argon that we use to better understand its transport and storage across the lunar surface. We took into account several loss processes: ionization by solar photons, charge-exchange with solar protons, and cold trapping as computed by recent LRO/Lunar Orbiter Laser Altimeter (LOLA) mapping of Permanently Shaded Regions (PSRs). Recycling of photo-ions and solar radiation acceleration are also considered. We report that (i) contrary to previous assumptions, charge exchange is a loss process as efficient as photo-ionization, (ii) the PSR cold-trapping flux is comparable to the ionization flux (photo-ionization and charge-exchange), and (iii) solar radiation pressure has negligible effect on the argon density, as expected. We determine that the release of 2.6 × 1028 atoms on top of a pre-existing argon exosphere is required to explain the maximum amount of argon measured by LACE. The total number of atoms (1.0 × 1029) corresponds to ∼6700 kg of argon, 30% of which (∼1900 kg) may be stored in the cold traps after 120 days in the absence of space weathering processes. The required population is consistent with the amount of argon that can be released during a High Frequency Teleseismic (HFT) Event, i.e. a big, rare and localized moonquake, although we show that LACE could not distinguish between a localized and a global event. The density of argon measured at the time of LACE appears to have originated from no less than four such episodic events. Finally, we show that the extent of the PSRs that trap

  4. Methane Ions Produced by Titan's Exosphere

    Science.gov (United States)

    Sittler, E. C.; Hartle, R. E.; Simpson, D. G.; Sarantos, M.; Cooper, J. F.; Ali, A.; Lipatov, A. S.

    2013-12-01

    The main source of CH4+ above Titan's exobase is from pickup ions produced by its CH4+ exosphere. Such ions are predicted from a CH4+ exosphere model describing density, temperature and wind at the exobase. Ionizing the CH4+ exosphere forms CH4+ ions that are picked up by the motional electric field of the magnetosphere. A range of exosphere models is considered relative to the Sun, accounting for the 360-degree ram direction produced by Saturn's magnetospheric rotation. Exospheric densities increase in the equatorial or polar regions when exobase winds are zonal or meridianal. Pickup ions entering the thermosphere produce heating as they slow down, raising the exobase temperature in these places. Hot spots also occur in different places of the exobase depending on where Saturn's magnetospheric current sheet is relative to Titan's orbit, being above, below or within; dipolar magnetospheric magnetic fields will cause equatorial heating on the Saturn side of Titan, while equatorially confined magnetospheric magnetic fields (current sheet geometry) heating will be at north polar region when Titan is below current sheet and on south polar region when Titan is above current sheet. When the methane exosphere is exposed to the magnetosphere's sheet, its temperature may be as high as 190 K. The corresponding CH4+ pickup ion density peaks at about 2×10-3 cm-3 in the up-flow direction of Titan, 2000 km above its ionopause. Alternatively, if the magnetosphere is in a lobe state, the exosphere's temperature may be reduced to 110 K, reducing the peak to 10-6 cm-3. This CH4+ pickup ion density difference can be used by the CAPS ion instruments to determine if the magnetosphere is in the sheet or lobe state at Titan's orbit. Furthermore, there are enough CH4+ pickup ions measured to be consistent with classical exosphere theories but may not be enough to support hydrodynamic expansion models [Sittler et al., 2009]. References: Sittler et al., (2009), Methane Group Ions in Saturn

  5. Mercury's Seasonal Sodium Exosphere: MESSENGER Orbital Observations

    Science.gov (United States)

    Cassidy, Timothy A.; Merkel, Aimee W.; Burger, Matthew H.; Killen, Rosemary M.; McClintock, William E.; Vervack, Ronald J., Jr.; Sarantos, Menelaos

    2014-01-01

    The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury provides the first close-up look at the planet's sodium exosphere. UVVS has observed the exosphere from orbit almost daily for over 10 Mercury years. In this paper we describe and analyze a subset of these data: altitude profiles taken above the low-latitude dayside and south pole. The observations show spatial and temporal variations, but there are no obvious year-to-year variations in most of the observations. We do not see the episodic variability reported by some ground-based observers. We used these altitude profiles to make estimates of sodium density and temperature. The bulk of the exosphere, at about 1200 K, is much warmer than Mercury's surface. This value is consistent with some ground-based measurements and suggests that photon-stimulated desorption is the primary ejection process. We also observe a tenuous energetic component but do not see evidence of the predicted thermalized (or partially thermalized) sodium near Mercury's surface temperature. Overall we do not see the variable mixture of temperatures predicted by most Monte Carlo models of the exosphere.

  6. Modeling Insights into the Lunar Exosphere

    Science.gov (United States)

    Hurley, D.; Feldman, P. D.; Retherford, K. D.; Cook, J.; Stern, S. A.

    2012-12-01

    In addition to Apollo data from the 1970s and ground-based observations, recent data from the Lyman Alpha Mapping Project (LAMP) onboard the Lunar Reconnaissance Orbiter (LRO) are revealing the structure and variability of the lunar exosphere. LAMP has detected helium in the lunar exosphere having many sources of variability. We use a Monte Carlo model to interpret variability in the observations of helium in the lunar exosphere from LAMP. Some of the variability stems from a time-varying source rate. Because the helium in the lunar exosphere predominately derives from the solar wind, we investigate the timescale of transport from release on the dayside to the nightside where it is observed. The model computes transport times for various assumptions about the energy distribution during the initial release and the effects of subsequent surface interactions on the ballistic transport. Owing to the changing geometry of the LRO orbit, spatial gradients also factor into the variability of the observations. We study the expected column density of helium as a function of latitude and longitude using surface temperatures measured by Diviner. The spatial distribution resulting from model runs is strongly influenced by the surface temperature and the assumed thermalization parameter. These dependencies can be used to extract information about the surface interactions. We compare model latitude and longitude dependences to LAMP and Apollo data. Finally, using upstream solar wind measurements and the position of LRO, we calculate the model time-varying helium exosphere of the Moon for comparison with LAMP data obtained in January, June, and July of 2012, including three passages of the Moon through Earth's magnetotail.

  7. Mercury's exosphere: observations during MESSENGER's First Mercury flyby.

    Science.gov (United States)

    McClintock, William E; Bradley, E Todd; Vervack, Ronald J; Killen, Rosemary M; Sprague, Ann L; Izenberg, Noam R; Solomon, Sean C

    2008-07-04

    During MESSENGER's first Mercury flyby, the Mercury Atmospheric and Surface Composition Spectrometer measured Mercury's exospheric emissions, including those from the antisunward sodium tail, calcium and sodium close to the planet, and hydrogen at high altitudes on the dayside. Spatial variations indicate that multiple source and loss processes generate and maintain the exosphere. Energetic processes connected to the solar wind and magnetospheric interaction with the planet likely played an important role in determining the distributions of exospheric species during the flyby.

  8. Calcium in Mercury's Exosphere: Modeling MESSENGER Data

    Science.gov (United States)

    Burger, M. H.; Killen, R. M.; McClintock, W. E.; Merkel, A. W.; Vervack, R. J.; Sarantos, M.; Sprague, A. L.

    2011-12-01

    Mercury is surrounded by a surface-bounded exosphere known to contain hydrogen, sodium, potassium, calcium, and magnesium. Because the exosphere is collisionless, its composition represents a balance of active source and loss processes. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has made high-spatial-resolution observations of sodium, calcium, and magnesium near Mercury's surface and in the extended, anti-sunward direction. The most striking feature of these data is the substantial differences among species, which was detected during three close flybys of the planet and has been persistantly present during MESSENGER's orbital phase. Our modeling demonstrates that these differences are not because of post-ejection dynamics such as differences in photo-ionization rate and radiation pressure, but rather result from differences in the source mechanisms and regions on the surface from which each species is ejected. The observations of calcium have revealed a strong dawn/dusk asymmetry, with the abundance over the dawn hemisphere substantially greater than that on the dusk side. To understand this asymmetry, we use a Monte Carlo model of Mercury's exosphere that we developed to track the motions of exospheric neutrals under the influence of gravity and radiation pressure. In this model, Ca atoms can be ejected directly from the surface or produced by ejection of CaO followed by dissociation to produce Ca and O. Particles are removed from the system if they stick to the surface or escape from the model region of interest (within 15 Mercury radii). Photoionization reduces the final weighting given to each particle when simulating the Ca radiance. Data from the flybys are consistent with a high temperature (~1-2 x 104 K) source of atomic Ca concentrated over the dawn hemisphere. Such a high temperature resutls from dissociation of CaO in a near

  9. The effects of Mars' exosphere on ENA observations

    Science.gov (United States)

    Holmstrom, M.; Gunell, H.; Ekenback, A.

    Traditionally, exospheric densities and velocity distributions are modelled by spherical symmetric analytical Chamberlain functions, assuming gravity is the only force acting on the neutrals. Planetary exospheres are however not spherical symmetric to any good approximation, as evident from observations, due to non-uniform exobase conditions and effects such as photoionization, radiation pressure, charge exchange, recombination and planetary rotation. To account for these effects numerical simulations are needed. Using Monte Carlo test particle simulations it is possible to account for the above effects (if ion distributions are assumed). Even though neutrals in the exospheres by definition do not collide often, collisions occur. Especially near the exobase the transition is gradual from collision dominated regions at lower heights (with Maxwellian velocity distributions) to essentially collisionless regions at greater heights. We present exospheric simulations that include collisions self consistently using the direct simulation Monte Carlo (DSMC) approach. The code is three dimensional, parallel and uses an adaptive grid, allowing many particles to be included in the simulations, leading to accurate results. In particular, we here study Mars' hydrogen exosphere and the effects of the above processes. Accurate exosphere models are important for analysis of energetic neutral atom (ENA) images, since the measured fluxes are line of sight convolutions of ion fluxes and neutral densities, and asymmetries in the exospheric profiles will directly affect the images. We compare observations by the neutral particle imager (NPI) on-board Mars Express with the predicted ENA fluxes from the simulation model.

  10. Mercury's Na Exosphere from MESSENGER Data

    Science.gov (United States)

    Killen, Rosemary M.; Burger, M. H.; Cassidy, T. A.; Sarantos, M.; Vervack, R. J.; McClintock, W. El; Merkel, A. W.; Sprague, A. L.; Solomon, S. C.

    2012-01-01

    MESSENGER entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UWS) channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) has been observing Mercury's exosphere nearly continuously. Daily measurements of Na brightness were fitted with non-uniform exospheric models. With Monte Carlo sampling we traced the trajectories of a representative number of test particles, generally one million per run per source process, until photoionization, escape from the gravitational well, or permanent sticking at the surface removed the atom from the simulation. Atoms were assumed to partially thermally accommodate on each encounter with the surface with accommodation coefficient 0.25. Runs for different assumed source processes are run separately, scaled and co-added. Once these model results were saved onto a 3D grid, we ran lines of sight from the MESSENGER spacecraft :0 infinity using the SPICE kernels and we computed brightness integrals. Note that only particles that contribute to the measurement can be constrained with our method. Atoms and molecules produced on the nightside must escape the shadow in order to scatter light if the excitation process is resonant-light scattering, as assumed here. The aggregate distribution of Na atoms fits a 1200 K gas, with a PSD distribution, along with a hotter component. Our models constrain the hot component, assumed to be impact vaporization, to be emitted with a 2500 K Maxwellian. Most orbits show a dawnside enhancement in the hot component broadly spread over the leading hemisphere. However, on some dates there is no dawn/dusk asymmetry. The portion of the hot/cold source appears to be highly variable.

  11. LADEE Search for a Dust Exosphere: A Historical Perspective

    Science.gov (United States)

    Glenar, D. A.; Stubbs, T. J.; Elphic, R.

    2014-01-01

    The LADEE search for exospheric dust is strongly motivated by putative detections of forward-scattered sunlight from exospheric dust grains which were observed during the Apollo era. This dust population, if it exists, has been associated with charging and transport of dust near the terminators. It is likely that the concentration of these dust grains is governed by a saltation mechanism originated by micrometeoroid impacts, which are the source of the more tenuous ejecta cloud.

  12. The long egress of GJ 436b's giant exosphere

    Science.gov (United States)

    Lavie, B.; Ehrenreich, D.; Bourrier, V.; Lecavelier des Etangs, A.; Vidal-Madjar, A.; Delfosse, X.; Gracia Berna, A.; Heng, K.; Thomas, N.; Udry, S.; Wheatley, P. J.

    2017-09-01

    The M dwarf GJ 436 hosts a transiting warm Neptune known to experience atmospheric escape. Previous observations revealed the presence of a giant hydrogen exosphere transiting the star for more than 5 h, and absorbing up to 56% of the flux in the blue wing of the stellar Lyman-α line of neutral hydrogen (H I Lyα). The unexpected size of this comet-like exosphere prevented observing the full transit of its tail. In this Letter, we present new Lyα observations of GJ 436 obtained with the Space Telescope Imaging Spectrograph (STIS) instrument onboard the Hubble Space Telescope. The stability of the Lyα line over six years allowed us to combine these new observations with archival data sets, substantially expanding the coverage of the exospheric transit. Hydrogen atoms in the tail of the exospheric cloud keep occulting the star for 10-25 h after the transit of the planet, remarkably confirming a previous prediction based on 3D numerical simulations with the EVaporating Exoplanet code (EVE). This result strengthens the interpretation that the exosphere of GJ 436b is shaped by both radiative braking and charge exchanges with the stellar wind. We further report flux decreases of 15 ± 2% and 47 ± 10% in the red wing of the Lyα line and in the line of ionised silicon (Si III). Despite some temporal variability possibly linked with stellar activity, these two signals occur during the exospheric transit and could be of planetary origin. Follow-up observations will be required to assess the possibility that the redshifted Lyα and Si III absorption signatures arise from interactions between the exospheric flow and the magnetic field of the star.

  13. Centrifugally Stimulated Exospheric Ion Escape at Mercury

    Science.gov (United States)

    Delcourt, Dominique; Seki, K.; Terada, N.; Moore, Thomas E.

    2012-01-01

    We investigate the transport of ions in the low-altitude magnetosphere magnetosphere of Mercury. We show that, because of small spatial scales, the centrifugal effect due to curvature of the E B drift paths can lead to significant particle energization in the parallel direction. We demonstrate that because of this effect, ions with initial speed smaller than the escape speed such as those produced via thermal desorption can overcome gravity and escape into the magnetosphere. The escape route of this low-energy exosphere originating material is largely controlled by the magnetospheric convection rate. This escape route spreads over a narrower range of altitudes when the convection rate increases. Bulk transport of low-energy planetary material thus occurs within a limited region of space once moderate magnetospheric convection is established. These results suggest that, via release of material otherwise gravitationally trapped, the E B related centrifugal acceleration is an important mechanism for the net supply of plasma to the magnetosphere of Mercury.

  14. Observation of suprathermal argon in the exosphere of Mars

    Science.gov (United States)

    Bhardwaj, Anil; Thampi, Smitha V.; Das, Tirtha Pratim; Dhanya, M. B.; Naik, Neha; Vajja, Dinakar Prasad; Pradeepkumar, P.; Sreelatha, P.; Abhishek J., K.; Thampi, R. Satheesh; Yadav, Vipin K.; Sundar, B.; Nandi, Amarnath; Padmanabhan, G. Padma; Aliyas, A. V.

    2017-03-01

    The altitude profiles of argon-40 (Ar) in the Martian exosphere are reported using Mars Exospheric Neutral Composition Analyser aboard Indian Mars Orbiter Mission (MOM) from four orbits during December 2014 (Ls = 250°-257°), when MOM's periapsis altitude was the lowest. The upper limit of Ar number density corresponding to this period is ˜5 × 105 cm-3 (˜250 km), and the typical scale height is ˜16 km, corresponding to an exospheric temperature of ˜275 K. However, on two orbits, the scale height over this altitude region is found to increase significantly making the effective temperature >400 K. Neutral Gas and Ion Mass Spectrometer observations on the Mars Atmosphere and Volatile Evolution mission also indicate that the change in slope in Ar density occurs near the upper exosphere (around 230-260 km). These observations indicate significant suprathermal CO2 and Ar populations in the Martian exosphere. Significant wave-like perturbations are observed but only on certain days when suprathermal population is seen. Pickup ion-induced heating is discussed as the other viable source.

  15. Conditions for Sublimating Water Ice to Supply Ceres' Exosphere

    Science.gov (United States)

    Landis, M. E.; Byrne, S.; Schörghofer, N.; Schmidt, B. E.; Hayne, P. O.; Castillo-Rogez, J.; Sykes, M. V.; Combe, J.-P.; Ermakov, A. I.; Prettyman, T.; Raymond, C. A.; Russell, C. T.

    2017-09-01

    We explore the conditions for sublimating water ice on Ceres to explain the observed water vapor output from telescopic observations. We find that while a buried ice table cannot produce enough vapor via sublimation to explain the exosphere, exposed surface ice (given it is exposed at the right time during the Ceres day and year, and at the right location) can.

  16. Mercury's Sodium Exosphere: Observations during the MESSENGER Orbital Phase

    Science.gov (United States)

    Killen, Rosemary M.; Cassidy, Timothy A.; Vervack, Ronald J., Jr.; Burger, Matthew H.; Merkel, Aimee W.; Sarantos, Menelaos; Sprague, Ann L.; McClintock, William E.; Benna, Mehdi; Solomon, Sean C.

    2012-01-01

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft entered into orbit about Mercury on March 18,2011. We now have approximately five Mercury years of data from orbit. Prior to the MESSENGER mission, Mercury's surface-bounded exosphere was known to contain H, He, Na. K, and Ca. The Ultraviolet and Visible Spectrometer (UVVS) began routine orbital observations of both the dayside and nightside exosphere on March 29. 2011, measuring altitude profiles for all previously detected neutral species except for He and K. We focus here on what we have learned about the sodium exosphere: its spatial, seasonal, and sporadic variation. Observations to date permit delineation of the relative roles of photon-stimulated desorption (PSD) and impact vaporization (IV) from seasonal and spatial effects, as well as of the roles of ions both as sputtering agents and in their possible role to enhance the efficiency of PSD. Correlations of Mercury's neutral sodium exosphere with measurements from MESSENGER's Magnetometer (MAG) and Energetic Particle and Plasma Spectrometer (EPPS) provide insight into the roles of ions and electrons. Models incorporating MAG observations provide a basis for identifying the location and area of the surface exposed to solar wind plasma, and EPPS observations reveal episodic populations of energetic electrons in the magnetosphere and the presence of planetary He(+), 0(+), and Na(+),

  17. An exospheric temperature model from CHAMP thermospheric density

    Science.gov (United States)

    Weng, Libin; Lei, Jiuhou; Sutton, Eric; Dou, Xiankang; Fang, Hanxian

    2017-02-01

    In this study, the effective exospheric temperature, named as T∞, derived from thermospheric densities measured by the CHAMP satellite during 2002-2010 was utilized to develop an exospheric temperature model (ETM) with the aid of the NRLMSISE-00 model. In the ETM, the temperature variations are characterized as a function of latitude, local time, season, and solar and geomagnetic activities. The ETM is validated by the independent GRACE measurements, and it is found that T∞ and thermospheric densities from the ETM are in better agreement with the GRACE data than those from the NRLMSISE-00 model. In addition, the ETM captures well the thermospheric equatorial anomaly feature, seasonal variation, and the hemispheric asymmetry in the thermosphere.

  18. Methane Group Ions Produced by Titan's Exosphere and Ionosphere

    Science.gov (United States)

    Sittler, Edward; Hartle, Richard; Simpson, David; Sarantos, Menelaos; Cooper, John; Ali, Ashraf; Lipatov, Alexander

    2014-05-01

    We will be presenting results of methane ions that can be injected into Saturn's magnetosphere as pick up ions from Titan's exosphere and outflowing methonium ions CH5+, the HCNH+ ion and the ethenium ions C2H5+ from Titan's ionosphere. Ionospheric outflows have been seen during the T9 flyby (Sittler et al., 2010), and the T63 and T75 flybys (Coates et al., 2012) where source rates to magnetosphere can be significant ~ 4.0x1024 ions/s. When methane pickup ions are born within Titan's exosphere and convective electric field points outward these ions will populate Saturn's magnetosphere, while inward convective electric field (Saturn side for dipolar magnetospheric fields) will heat the upper atmosphere and exosphere. Using 1D exosphere Westlake et al. (2011) found that the exosphere was hotter and more extended when Titan was within Saturn's sheet, while in lobe like regions of magnetosphere the exosphere is cooler. Using a 3D exosphere model, which can include winds and asymmetric heating at exobase to model methane pickup ion densities; we estimate that when within Saturn's sheet the exobase T ~ 190° K and the estimated density is ~ 2x10-3 ions/cm3 which are observable, while in lobe like regions exosphere T ~ 110° K and densities ~ 10-6 ions/cm3 not observable. The heating from methane pickup ions can be complex depending upon magnetic field geometry, dipolar (heating on Saturn side) and disc geometry (below sheet north polar heating and above sheet south polar heating). This CH4+ pickup ion density difference we estimate can be used by the CAPS ion instruments to determine if the magnetosphere is in the sheet (also plasma sheet usually dominated by water group ions with O+ ions) or lobe state (light ions H+/H2+ dominating the composition). We find CH4+ pickup ions for T36 and T39 flybs when Titan is within Saturn's magntospheric sheet, while during T41 when within lobe regions of Saturn's magnetosphere CH4+ pickup ions were not observed. But for T41 the

  19. Insights into the Nature of Mercury's Exosphere: Early Results from the MESSENGER Orbital Mission Phase

    Science.gov (United States)

    McClintock, William E.; Burger, Matthew H.; Killen, Rosemary M.; Merkel, Aimee W.; Sarantos, Menelaos; Sprague, Ann L.; Solomon, Sean C.; Vervack, Ronald J., Jr.

    2011-01-01

    The Ultraviolet and Visible Spectrometer aboard the MESSENGER spacecraft has been making routine observations of Mercury's exosphere since March 29, 2011. Correlations of the spatial distributions of Ca, Mg, and Na with MESSENGER magnetic field and energetic particle distribution data provide insight into the processes that populate the neutral exosphere

  20. A Global Plume-Fed Europan Exosphere: Structure, Composition, Temporal Variability, and Surface Interactions

    Science.gov (United States)

    Teolis, B. D.; Waite, J. H., Jr.; Wyrick, D. Y.; Bouquet, A.; Magee, B.

    2014-12-01

    We present results from our Europa global exospheric modeling, which includes both sputtering / radiolytic and potential plume sources, and a sophisticated treatment of the exosphere-surface interaction, i.e., surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials. We consider the effect of Europa's gravity in pulling plume vapor back to the surface and the subsequent spreading of adsorbed and exospheric material by thermal desorption and re-sputtering across the entire body. Our results show the global spatial distribution and temporal evolution of the surface exospheric density and composition for several scenarios, e.g., a solely sputtered / radiolytic exosphere, and the inclusion of transient and/or steady plume sources with an Enceladus-like composition. The model provides a useful tool for interpreting remote observations, and for extrapolating possible neutral and ion densities and compositional profiles along potential future spacecraft trajectories.

  1. Estimating Exospheric Hydrogen Density Using Lyman-a Solar Irradiance Measurements From SOLSTICE

    Science.gov (United States)

    Pierrat, Z.; Snow, M. A.; Machol, J. L.

    2016-12-01

    The final layer of the earth's atmosphere, the exosphere, extends from 500km-10,000km above the earth's surface and is characterized by atomic densities of hydrogen so low that atomic collisions seldom occur. The small amount of hydrogen, however, still has a significant impact on satellite drag and satellite sensor observations that must look through the exosphere. The Solar Radiation Comparison Experiment (SORCE), which orbits well within the exosphere, at 645km, exemplifies this effect. The Solar-Stellar Irradiance Comparison Experiment (SOLSTICE) on SORCE samples a wide range of solar spectral irradiances, including Lyman-a, and is impacted by the effects of exospheric hydrogen. As solar photons enter the exosphere, hydrogen scatters Lyman-a out of the line of sight to SOLSTICE. SOLSTICE measures over a range of path lengths through the exosphere as it orbits, dependent on the angle between the satellite and the sun. The longer the path length, the more scattering of light occurs before reaching the satellite. By correcting the data from SOLSTICE for Lyman-a scattering, we not only produce a better solar irradiance data set for climate and other studies, but we can also learn more about the density of hydrogen in the exosphere. SORCE has been in orbit since 2003, so we can track the changes in the density of exospheric hydrogen through the solar cycle. This research is aimed at determining the impact of Lyman-a scattering on the SOLSTICE data set, finding a function to model the density of hydrogen in the exosphere, and tracking the changes in exospheric hydrogen density through time. This information will improve our understanding of the interactions between the sun and the upper atmosphere, as well as helping improve satellite drag models.

  2. The Exosphere of Ceres Generated by Photolysis and Radiolysis

    Science.gov (United States)

    Tseng, W. L.; Ip, W. H.; Kuan, Y. J.

    2016-12-01

    Ceres is the largest object (with a diameter of 950 km) among the main-belt asteroids. The OH cloud, the photodissociated products of H2O, was suggested by the IUE (International Ultraviolet Explorer) observations to be present around Ceres (A'Hearn and Feldman, 1992). Recently, Kuppers et al. (2014) reported a direct detection of water vapor by Herschel that > 1026 molecules s-1was produced from localized sources on Ceres' surface. Most excitingly, the Dawn images showed that a haze layer consisting of water-ice particles and dust was found above the Occator crater (Nathues et al., 2015). The haze was also shown to have a diurnal change of brightness, indicating a comet-like sublimation activity. In addition, subsurface outgassing (e.g., cryovolcanism and/or the plume activity similar to that found in Enceladus) is another possible source mechanism, which is not fully understood yet. Following the Ceres' exospheric model of Tu et al. (2014), here we focus on O2, O3 and H2O2 molecules, which are the primary products of radiolytic and photolytic decomposition of water ice, and possibly the CO2 and SO2 molecules produced from the impurities. We will compute the source rates from various production mechanisms and simulate the cloud morphologies. Then we will compare with the available data (e.g., the atomic oxygen emission observed by HST from Roth et al., 2016) and seek for any evidence in the ground-based millimeter/submillimeter observations. Understanding the chemical composition of Ceres and its evolved exosphere, in analogy to comets and the icy satellites, would reveal the secret of the origin and evolution of the solar system. 1. A'Hearn, M.F., Feldman, P.D., (1992) Water vaporization on Ceres. Icarus 98, 389-407. 2. Küppers, M., et al., (2014) Localized sources of water vapour on the dwarf planet (1) Ceres. Nature 505, 525-527. 3. Nathues, A., et al. (2015), Sublimation in bright spots on (1) Ceres, Nature, 528(7581), 237-240. 4. Tu, L., W.-H. Ip, and Y

  3. Mercury's complex exosphere: results from MESSENGER's third flyby.

    Science.gov (United States)

    Vervack, Ronald J; McClintock, William E; Killen, Rosemary M; Sprague, Ann L; Anderson, Brian J; Burger, Matthew H; Bradley, E Todd; Mouawad, Nelly; Solomon, Sean C; Izenberg, Noam R

    2010-08-06

    During MESSENGER's third flyby of Mercury, the Mercury Atmospheric and Surface Composition Spectrometer detected emission from ionized calcium concentrated 1 to 2 Mercury radii tailward of the planet. This measurement provides evidence for tailward magnetospheric convection of photoions produced inside the magnetosphere. Observations of neutral sodium, calcium, and magnesium above the planet's north and south poles reveal altitude distributions that are distinct for each species. A two-component sodium distribution and markedly different magnesium distributions above the two poles are direct indications that multiple processes control the distribution of even single species in Mercury's exosphere.

  4. Seasonal Variations of Mercury's Magnesium Dayside Exosphere from MESSENGER Observations

    Science.gov (United States)

    Merkel, Aimee W.; Cassidy, Timothy A.; Vervack, Ronald J., Jr.; McClintock, William E.; Sarantos, Menelaos; Burger, Matthew H.; Killen, Rosemary M.

    2017-01-01

    The Ultraviolet and Visible Spectrometer channel of the Mercury Atmospheric and Surface Composition Spectrometer instrument aboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft made near-daily observations of solar-scattered resonant emission from magnesium in Mercury's exosphere during the mission's orbital phase (March 2011-April 2015, approx.17 Mercury years). In this paper, a subset of these data (March 2013-April 2015) is described and analyzed to illustrate Mg's spatial and temporal variations. Dayside altitude profiles of emission are used to make estimates of the Mg density and temperature. The main characteristics of the Mg exosphere are (a) a predominant enhancement of emission in the morning (6 am-10 am) near perihelion, (b) a bulk temperature of approx. 6000 K, consistent with impact vaporization as the predominant ejection process, (c) a near-surface density that varies from 5/cu cm to 50/cu cm and (d) a production rate that is strongest in the morning on the inbound leg of Mercury's orbit with rates ranging from 1×10(exp 5)/sq cm/s to 8×10(exp 5)/sq cm/s.

  5. An Analytic Function of Lunar Surface Temperature for Exospheric Modeling

    Science.gov (United States)

    Hurley, Dana M.; Sarantos, Menelaos; Grava, Cesare; Williams, Jean-Pierre; Retherford, Kurt D.; Siegler, Matthew; Greenhagen, Benjamin; Paige, David

    2014-01-01

    We present an analytic expression to represent the lunar surface temperature as a function of Sun-state latitude and local time. The approximation represents neither topographical features nor compositional effects and therefore does not change as a function of selenographic latitude and longitude. The function reproduces the surface temperature measured by Diviner to within +/-10 K at 72% of grid points for dayside solar zenith angles of less than 80, and at 98% of grid points for nightside solar zenith angles greater than 100. The analytic function is least accurate at the terminator, where there is a strong gradient in the temperature, and the polar regions. Topographic features have a larger effect on the actual temperature near the terminator than at other solar zenith angles. For exospheric modeling the effects of topography on the thermal model can be approximated by using an effective longitude for determining the temperature. This effective longitude is randomly redistributed with 1 sigma of 4.5deg. The resulting ''roughened'' analytical model well represents the statistical dispersion in the Diviner data and is expected to be generally useful for future models of lunar surface temperature, especially those implemented within exospheric simulations that address questions of volatile transport.

  6. Impact Vaporization as a Possible Source of Mercury's Calcium Exosphere

    Science.gov (United States)

    Killen, Rosemary M.; Hahn, Joseph M.

    2015-01-01

    Mercury's calcium exosphere varies in a periodic way with that planet's true anomaly. We show that this pattern can be explained by impact vaporization from interplanetary dust with variations being due to Mercury's radial and vertical excursions through an interplanetary dust disk having an inclination within 5 degrees of the plane of Mercury's orbit. Both a highly inclined dust disk and a two-disk model (where the two disks have a mutual inclination) fail to reproduce the observed variation in calcium exospheric abundance with Mercury true anomaly angle. However, an additional source of impacting dust beyond the nominal dust disk is required near Mercury's true anomaly (?) 25deg +/-5deg. This is close to but not coincident with Mercury's true anomaly (?=45deg) when it crosses comet 2P/Encke's present day orbital plane. Interestingly, the Taurid meteor storms at Earth, which are also due to Comet Encke, are observed to occur when Earth's true anomaly is +/-20 or so degrees before and after the position where Earth and Encke orbital planes cross. The lack of exact correspondence with the present day orbit of Encke may indicate the width of the potential stream along Mercury's orbit or a previous cometary orbit. The extreme energy of the escaping calcium, estimated to have a temperature greater than 50000 K if the source is thermal, cannot be due to the impact process itself but must be imparted by an additional mechanism such as dissociation of a calcium-bearing molecule or ionization followed by recombination.

  7. A Collisonal Exospheric Model for Mars: Implications for X-ray and ENA Imaging

    Science.gov (United States)

    Holmstrom, M.

    2005-12-01

    Traditionally, exospheric densities and velocity distributions are modelled by spherical symmetric analytical Chamberlain functions, assuming gravity is the only force acting on the neutrals. Planetary exospheres are however not spherical symmetric to any good approximation, as evident from observations, due to effects such as photoionization, radiation pressure, charge exchange, recombination and planetary rotation. To account for these effects numerical simulations are needed. Using Monte Carlo test particle simulations it is possible to account for the above effects (if ion distributions are assumed). Even though neutrals in the exospheres by definition do not collide often, collisions occur. Especially near the exobase the transition is gradual from collision dominated regions at lower heights (with Maxwellian velocity distributions) to essentially collisionless regions at greater heights. We present exospheric simulations that include collisions self consistently using the direct simulation Monte Carlo (DSMC) approach. The code is three dimensional, parallel and uses an adaptive grid, allowing many particles to be included in the simulations, leading to accurate results. In particular, we here study Mars' hydrogen exosphere and the effects of the above processes, including thermal escape rates. Accurate exosphere models are also important for analysis of X-ray and energetic neutral atom (ENA) images, since the measured fluxes are line of sight convolutions of ion fluxes and neutral densities, and asymmetries in the exospheric profiles will directly affect the images. We present implications for observations of solar wind charge exchange X-rays and for observations of ENAs at Mars.

  8. The Transformation of the Lunar Exosphere by a Comet Impact

    Science.gov (United States)

    Prem, P.; Artemieva, N. A.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.

    2014-12-01

    Several observations suggest that water and other volatiles delivered by past comet impacts may have migrated to permanently shadowed regions near the poles of the Moon and Mercury, where they may still remain cold-trapped. Here, we compare the nature of gas transport and loss processes in a collisionless exosphere to the situation after a lunar comet impact. The sheer quantity of volatiles delivered by a comet can transform the way in which gas transport and deposition occur; we model this using the Direct Simulation Monte Carlo method. It is observed that post-impact gas transport occurs primarily through low-altitude winds that sweep over the lunar day-side, as opposed to migration of molecules through ballistic hops. The resultant deposition patterns are markedly non-uniform, with preferential redistribution of water antipodal to the point of impact, and short-term variations in simulated volatile abundance between different cold traps, suggesting that a non-uniform delivery mechanism could contribute towards the non-uniform distribution of lunar polar volatiles observed in remote sensing datasets. Due to the amount of vapor that remains gravitationally bound to the Moon, the transient, impact-generated atmosphere is initially sufficiently dense that lower layers are shielded from photodestruction, prolonging the lifetime of water molecules and allowing greater amounts of water to reach cold traps. Other physical processes, such as radiative heat transfer and photochemical reactions, also operate differently when the exosphere becomes collisionally and optically thick. The longevity of the transient atmosphere and the significance of the phenomena mentioned above depend on specific impact parameters, as well as the gravitational and solar environment of the body in question - for instance, Mercury could retain a thicker atmosphere, but sees much more intense ultraviolet radiation than the Moon. However, the characteristic structure of the atmosphere and the

  9. The ancient oxygen exosphere of Mars: Implications for atmosphere evolution

    Science.gov (United States)

    Zhang, M. H. G.; Luhmann, J. G.; Nagy, A. F.; Bougher, S. W.

    1992-01-01

    This study involves the calculation, by the 2-stream method of Nagy and Cravens, of 'hot' oxygen exosphere density profiles for 'ancient' atmospheres and ionospheres (e.g., different extreme ultraviolet fluxes) and the associated escaping fluxes. We computed the total production rates above different 'nominal' ionopause altitudes (not taking into account the fact that some will reenter the atmosphere). We do not consider the additional neutral escape due to the sputtering process described by Luhmann and Kozyra. The results presented here thus represent conservative estimations of the neutral escape fluxes, but generous estimates of ion loss rates (except that here we do not consider charge exchange and impact ionization ion production processes). Further work along the lines of Luhmann and Kozyra can lead to estimates of sputtering losses over time and the roles played by impact ionization and charge exchange.

  10. The ancient oxygen exosphere of Mars - Implications for atmosphere evolution

    Science.gov (United States)

    Zhang, M. H. G.; Luhmann, J. G.; Bougher, S. W.; Nagy, A. F.

    1993-01-01

    The paper considers absorption of oxygen (atoms and ions) by the surface as a mechanism for the early Martian atmosphere escape, due to the effect of high EUV flux of the ancient sun. Hot oxygen exosphere densities in ancient atmosphere and ionosphere are calculated for different EUV fluxes and the escape fluxes associated with these exposures. Using these densities, the ion production rate above the ionopause is calculated for different epochs including photoionization, charge exchange, and solar wind electron impact. It is found that, when the inferred high solar EUV fluxes of the past are taken into account, oxygen equivalent to that in several tens of meters of water, planet-wide, should have escaped Martian atmosphere to space over the last 3 Gyr.

  11. Wide-Field Ultraviolet Spectrometer for Planetary Exospheres and Thermospheres

    Science.gov (United States)

    Fillingim, M. O.; Wishnow, E. H.; Miller, T.; Edelstein, J.; Lillis, R. J.; Korpela, E.; England, S.; Shourt, W. V.; Siegmund, O.; McPhate, J.; Courtade, S.; Curtis, D. W.; Deighan, J.; Chaffin, M.; Harmoul, A.; Almatroushi, H. R.

    2016-12-01

    Understanding the composition, structure, and variability of a planet's upper atmosphere - the exosphere and thermosphere - is essential for understanding how the upper atmosphere is coupled to the lower atmosphere, magnetosphere and near-space environment, and the Sun. Ultraviolet spectroscopy can directly observe emissions from constituents in the exosphere and thermosphere. From such observations, the structure, composition, and variability can be determined.We will present the preliminary design for a wide field ultraviolet imaging spectrometer for remote sensing of planetary atmospheres. The imaging spectrometer achieves an extremely large instantaneous 110 degree field of view with no moving scanning mirror. The imaging resolution is very appropriate for extended atmospheric emission studies, with a resolution of better than 0.3 degrees at the center to 0.4 degrees at the edges of the field. The spectral range covers 120 - 170 nm, encompassing emissions from H, O, C, N, CO, and N2, with an average spectral resolution of 1.5 nm. The instrument is composed of a 2-element wide-field telescope, a 3-element Offner spectrometer, and a sealed MCP detector system contained within a compact volume of about 40 x 25 x 20 cm. We will present the optical and mechanical design as well as the predicted optical performance.The wide instantaneous FOV simplifies instrument and spacecraft operations by removing the need for multiple scans (either from a scan mirror or spacecraft slews) to cover the regions of interest. This instrumentation can allow for two-dimensional spectral information to be built up with simple spacecraft operation or just using spacecraft motion. Applications to the terrestrial geocorona and thermosphere will be addressed as well as applications to the upper atmospheres of other planetary objects.

  12. Plume and surface feature structure and compositional effects on Europa's global exosphere: Preliminary Europa mission predictions

    Science.gov (United States)

    Teolis, B. D.; Wyrick, D. Y.; Bouquet, A.; Magee, B. A.; Waite, J. H.

    2017-03-01

    A Europa plume source, if present, may produce a global exosphere with complex spatial structure and temporal variability in its density and composition. To investigate this interaction we have integrated a water plume source containing multiple organic and nitrile species into a Europan Monte Carlo exosphere model, considering the effect of Europa's gravity in returning plume ejecta to the surface, and the subsequent spreading of adsorbed and exospheric material by thermal desorption and re-sputtering across the entire body. We consider sputtered, radiolytic and potential plume sources, together with surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials, and examine the spatial distribution and temporal evolution of the exospheric density and composition. These models provide a predictive basis for telescopic observations (e.g. HST, JWST) and planned missions to the Jovian system by NASA and ESA. We apply spacecraft trajectories to our model to explore possible exospheric compositions which may be encountered along proposed flybys of Europa to inform the spatial and temporal relationship of spacecraft measurements to surface and plume source compositions. For the present preliminary study, we have considered four cases: Case A: an equatorial flyby through a sputtered only exosphere (no plumes), Case B: a flyby over a localized sputtered 'macula' terrain enriched in non-ice species, Case C: a south polar plume with an Enceladus-like composition, equatorial flyby, and Case D: a south polar plume, flyby directly through the plume.

  13. LRO-LAMP Observations of Lunar Exospheric Helium

    Science.gov (United States)

    Grava, Cesare; Retherford, Kurt D.; Hurley, Dana M.; Feldman, Paul D.; Gladstone, Randy; Greathouse, Thomas K.; Cook, Jason C.; Stern, Alan; Pryor, Wayne R.; Halekas, Jasper S.; Kaufmann, David E.

    2015-11-01

    latitude of the lunar exospheric helium, allowing for a better understanding of the temporal and spatial structure of the lunar exosphere.

  14. Regions of enhanced density in the Martian exosphere

    Science.gov (United States)

    Williamson, Hayley; Johnson, Robert E.; Elrod, Meredith K.; Curry, Shannon; Leclercq, Ludivine; Tucker, Orenthal

    2017-10-01

    The Neutral Gas and Ion Mass Spectrometer (NGIMS) instrument on the Mars Atmosphere and Volatile EvolutioN Mission (MAVEN) provides in-situ measurements of neutral and ion gases in the Martian exosphere. We studied these measurements for atomic oxygen, argon, and carbon dioxide for a full Martian year and discovered that in roughly 10% of the orbits, there is a significant and sharp increase in density versus altitude above the calculated neutral exobase. We calculate temperature and scale height profiles for these orbits that suggest local heating on the order of several hundred degrees Kelvin is likely occurring and investigate the causes of these features using both correlation with other MAVEN data and atmospheric modeling. These features do not appear to correspond with any particular location or local time, nor do they appear to correlate with solar wind variables. Therefore, it is possible that these are either the result of gravity waves propagating above the exobase or are produced by the stochastic ion precipitation environment. Using models, we compare both of these scenarios to the existing data.

  15. Conditions for Sublimating Water Ice to Supply Ceres' Exosphere

    Science.gov (United States)

    Landis, M. E.; Byrne, S.; Schörghofer, N.; Schmidt, B. E.; Hayne, P. O.; Castillo-Rogez, J.; Sykes, M. V.; Combe, J.-P.; Ermakov, A. I.; Prettyman, T. H.; Raymond, C. A.; Russell, C. T.

    2017-10-01

    Observations of a water vapor exosphere around Ceres suggest that the dwarf planet may be episodically outgassing at a rate of 6 kg s-1 from unknown sources. With data from the Dawn mission as constraints, we use a coupled thermal and vapor diffusion model to explore three different configurations of water ice (global buried pore-filling ice, global buried excess ice, and local exposed surface ice) that could be present on Ceres. We conclude that a buried ice table cannot alone explain the vapor production rates previously measured, but newly exposed surface ice, given the right conditions, can exceed that vapor production rate. Sublimation lag deposits form that bury and darken this surface ice over a large range of timescales (from <1 year to approximately hundreds of kyr) that depend on latitude and ice regolith content. Sublimating water vapor can loft regolith particles from the surface of exposed ice, possibly prolonging the visible lifespan of those areas. We find that this process is only effective for regolith grains smaller than approximately ones of microns.

  16. Metallic Species, Oxygen and Silicon in the Lunar Exosphere: Upper Limits and Prospects for LADEE Measurements

    Science.gov (United States)

    Sarantos, Menelaos; Killen, Rosemary Margaret; Glenar, David A.; Benna, Mehdi; Stubbs, Timothy J.

    2012-01-01

    The only species that have been so far detected in the lunar exosphere are Na, K, Ar,and He. However, models for the production and loss of species derived from the lunarregolith through micrometeoroid impact vaporization, sputtering, and photon-stimulateddesorption, predict that a host of other species should exist in the lunar exosphere.Assuming that loss processes are limited to ballistic escape, photoionization, and recyclingto the surface, we have computed column abundances and compared them to publishedupper limits for the Moon. Only for Ca do modeled abundances clearly exceed theavailable measurements. This result suggests the relevance of some loss processes thatwere not included in the model, such as the possibility of gas-to-solid phasecondensation during micrometeoroid impacts or the formation of stable metallic oxides.Our simulations and the recalculation of efficiencies for resonant light scattering showthat models for other species studied are not well constrained by existingmeasurements. This fact underlines the need for improved remote and in situmeasurements of the lunar exosphere such as those planned by the Lunar Atmosphereand Dust Environment Explorer (LADEE) spacecraft. Our simulations of the LADEEneutral mass spectrometer and visibleultraviolet spectrometer indicate that LADEE measurements promise to provide definitive observations or set stringent upper limitsfor all regolith-driven exospheric species. We predict that observations by LADEE willconstrain assumed model parameters for the exosphere of the Moon.

  17. Probing of Hermean Exosphere by ultraviolet spectroscopy: Instrument presentation, calibration philosophy and first lights results

    Science.gov (United States)

    Mariscal, J. F.; Rouanet, N.; Maria, J. L.; Quémerais, E.; Mine, P. O.; Zuppella, P.; Suman, M.; Nicolosi, P.; Pelizzo, M. G.; Yoshikawa, I.; Yoshioka, K.; Murakami, G.

    2017-11-01

    PHEBUS (Probing of Hermean Exosphere by Ultraviolet Spectroscopy) is a double spectrometer for the Extreme Ultraviolet range (55-155 nm) and the Far Ultraviolet range (145-315 nm) dedicated to the characterization of Mercury's exosphere composition and dynamics, and surface-exosphere connections. PHEBUS is part of the ESA BepiColombo cornerstone mission payload devoted to the study of Mercury. The BepiColombo mission consists of two spacecrafts: the Mercury Magnetospheric Orbiter (MMO) and the Mercury Planetary Orbiter (MPO) on which PHEBUS will be mounted. PHEBUS is a French-led instrument implemented in a cooperative scheme involving Japan (detectors), Russia (scanner) and Italy (ground calibration). Before launch, PHEBUS team want to perform a full absolute calibration on ground, in addition to calibrations which will be made in-flight, in order to know the instrument's response as precisely as possible. Instrument overview and calibration philosophy are introduced along with the first lights results observed by a first prototype.

  18. Dione and Rhea seasonal exospheres revealed by Cassini CAPS and INMS

    Science.gov (United States)

    Teolis, B. D.; Waite, J. H.

    2016-07-01

    A Dione O2 and CO2 exosphere of similar composition and density to Rhea's is confirmed by Cassini spacecraft Ion Neutral Mass Spectrometer (INMS) flyby data. INMS results from three Dione and two Rhea flybys show exospheric spatial and temporal variability indicative of seasonal exospheres, modulated by winter polar gas adsorption and desorption at the equinoxes. Cassini Plasma Spectrometer (CAPS) pickup ion fluxes also show exospheric structure and evolution at Rhea consistent with INMS, after taking into consideration the anticipated charge exchange, electron impact, and photo-ionization rates. Data-model comparisons show the exospheric evolution to be consistent with polar frost diffusion into the surface regolith, which limits surface exposure and loss of the winter frost cap by sputtering. Implied O2 source rates of ∼45(7) × 1021 s-1 at Dione(Rhea) are ∼50(300) times less than expected from known O2 radiolysis yields from ion-irradiated pure water ice measured in the laboratory, ruling out secondary sputtering as a major exospheric contributor, and implying a nanometer scale surface refractory lag layer consisting of concentrated carbonaceous impurities. We estimate ∼30:1(2:1) relative O2:CO2 source rates at Dione(Rhea), consistent with a stoichiometric bulk composition below the lag layer of 0.01(0.13) C atoms per H2O molecule, deriving from endogenic constituents, implanted micrometeoritic organics, and (in particular at Dione) exogenous H2O delivery by E-ring grains. Impact deposition, gardening and vaporization may thereby control the global O2 source rates by fresh H2O ice exposure to surface radiolysis and trapped oxidant ejection.

  19. Particle Tracing of Heavy Ions in Hermean Exosphere With Applications to the MESSENGER.

    Science.gov (United States)

    Paral, J.; Travnicek, P.; Rankin, R.; Kabin, K.

    2008-12-01

    We carry out Monte Carlo simulations of heavy particle species which are released from the surface of the planet Mercury as neutral particles and later on they are ionized. We consider three major sources of particle injection, namely Photon stimulated desorption, Solar wind sputtering and Micro-meteoroid vaporisation to build neutral exosphere. Then, we investigate the resulting exosphere and identify regions of particle acceleration due to the electromagnetic fields as well as distribution of ionization in the simulation box. The results are put into the context of the MESSENGER mission which measure the in situ data during its first fly by on January, 14 2008.

  20. Monte Carlo Simulations of the Lunar Exosphere: Insights into Polar Volatiles

    Science.gov (United States)

    Crider, Dana; Vondrak, R.

    2007-10-01

    We have constructed a Monte Carlo model applicable to a surface bounded exosphere, like those at the Moon and Mercury. It computes the motion of exospheric particles on ballistic trajectories as they hop around the surface until they are lost from the system. The model can be used to determine column density, surface concentrations, escape rates, or delivery efficiencies. We use the model to investigate the migration of volatiles on the Moon. We perform simulations to determine observable features that would help distinguish characteristics of volatiles that may be sequestered in permanently shadowed regions near the lunar poles, including composition, source, and distribution.

  1. Observations of Mercury’s Neutral Hydrogen Exosphere During the MESSENGER Orbital Phase

    Science.gov (United States)

    Vervack, Ronald J.; Hurley, Dana; Pryor, Wayne R.

    2017-10-01

    Because of the difficulty of observing H Lyman α at Mercury remotely, the MESSENGER mission afforded the first chance since the Mariner 10 flybys to investigate the neutral hydrogen exosphere of Mercury in detail. Mariner 10 discovered H at Mercury, but left many questions about the puzzling temperature and density distributions unanswered. Sparse observations during the MESSENGER flybys of Mercury suggested that the H exosphere was grossly similar to what was observed by Mariner 10, but with higher overall emission levels, and they provided no answers to the outstanding issues from Mariner 10. Observations of H Lyman α emission by the Ultraviolet and Visible Spectrometer (UVVS) component of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument onboard MESSENGER were conducted regularly throughout the MESSENGER orbital phase. These observations provide a much more complete picture of the H exosphere at Mercury. We present an analysis of the UVVS orbital observations, focusing on the temporal and spatial distribution of the hydrogen about the planet. Preliminary models will be shown, and the UVVS data will be compared and contrasted to the Mariner 10 data to address the long-outstanding questions about this element of Mercury’s complex exosphere. Support from the NASA Discovery Data Analysis Program is gratefully acknowledged.

  2. Methods for Monte Carlo simulation of the exospheres of the moon and Mercury

    Science.gov (United States)

    Hodges, R. R., Jr.

    1980-01-01

    A general form of the integral equation of exospheric transport on moon-like bodies is derived in a form that permits arbitrary specification of time varying physical processes affecting atom creation and annihilation, atom-regolith collisions, adsorption and desorption, and nonplanetocentric acceleration. Because these processes usually defy analytic representation, the Monte Carlo method of solution of the transport equation, the only viable alternative, is described in detail, with separate discussions of the methods of specification of physical processes as probabalistic functions. Proof of the validity of the Monte Carlo exosphere simulation method is provided in the form of a comparison of analytic and Monte Carlo solutions to three classical, and analytically tractable, exosphere problems. One of the key phenomena in moonlike exosphere simulations, the distribution of velocities of the atoms leaving a regolith, depends mainly on the nature of collisions of free atoms with rocks. It is shown that on the moon and Mercury, elastic collisions of helium atoms with a Maxwellian distribution of vibrating, bound atoms produce a nearly Maxwellian distribution of helium velocities, despite the absence of speeds in excess of escape in the impinging helium velocity distribution.

  3. LRO-LAMP Observations of the Lunar Exosphere Coordinated with LADEE

    Science.gov (United States)

    Grava, C.; Retherford, K. D.; Greathouse, T. K.; Gladstone, R.; Hurley, D.; Cook, J. C.; Stern, S. A.; Feldman, P. D.; Kaufmann, D. E.; Miles, P. F.; Pryor, W. R.; Halekas, J. S.

    2014-12-01

    The polar orbiting Lunar Reconnaissance Orbiter's (LRO) Lyman Alpha Mapping Project (LAMP) carried out an atmospheric campaign during the month of December 2013, at the same time the Lunar Atmospheric and Dust Environment Explorer (LADEE) mission was sampling the lunar exosphere in a retrograde equatorial orbit. Observations of the lunar exosphere were performed by LAMP during a solar "beta-90" geometry, i.e. riding along the lunar terminator. During this geometry, the LAMP nadir-pointed line of sight to the nightside surface also includes illuminated columns of foreground emissions from exospheric species, which is invaluable in the study of the tenuous lunar exosphere. Other types of maneuvers to probe the lunar exosphere were also performed by LAMP/LRO during this campaign. During backward pitch slews, the LRO spacecraft was pitched to look opposite its direction of motion to a point just inside the limb in the nightside region around the polar terminator. Forward pitch slews were also obtained, and the angles of 63 deg or 77 deg from nadir were set depending on the polar region observed. Finally, during lateral roll slews, LRO rotated by ~60 deg towards the nightside limb, maximizing the amount of illuminated atmosphere in the foreground probed by the LAMP field of view. We extract day to day density variations on helium and/or upper limits for numerous other species that were accessible to both LAMP and LADEE (e.g., Ar, Ne, O, and H2). Moreover, constraints on helium density will complement measurements of solar wind alpha particles (He++) from the ARTEMIS (Acceleration, Reconnection, Turbulence, & Electrodynamics of Moon's Interaction with the Sun) mission. This comparison will provide a comprehensive picture of composition, abundance, and spatial and temporal variations of volatiles of the lunar exosphere, combining equatorial (LADEE) and polar (LAMP) measurements for the first time. Volatiles in the lunar exosphere, especially water, are of paramount

  4. Investigation of the possible effects of comet's encke metoeroid stream on the ca-exosphere of mercury

    Science.gov (United States)

    Plainaki, Christina; Mura, Alessandro; Milillo, Anna; Orsini, Stefano; Livi, Stefano; Mangano, Valeria; Massetti, Stefano; Rispoli, Rosanna; De Angelis, Elisabetta

    2017-04-01

    The MESSENGER observations of the Ca-exosphere seasonal variability were consistent with the general idea that the Ca-atoms originate from the bombardment of the surface by particles from comet 2P/Encke. The generating process is a chain and combination of different processes including atomic and molecular release of surface particles and photo-dissociation. Including generation and loss mechanisms due to different planet-environment interactions, we perform simulations using a 3D Monte Carlo model based on the exosphere generation model by Mura et al. (2009). We present for the first time the 3D spatial distribution of the CaO and Ca exospheres generated through Micrometeoroid Impact Vaporization (MIV) and we show that the morphology of the latter is consistent with the available MESSENGER/MASCS observations. The results presented in this paper can be of help during the preparation phase of the exosphere observations to be performed with Bepi Colombo in the next years

  5. MESSENGER observations of the composition of Mercury's ionized exosphere and plasma environment.

    Science.gov (United States)

    Zurbuchen, Thomas H; Raines, Jim M; Gloeckler, George; Krimigis, Stamatios M; Slavin, James A; Koehn, Patrick L; Killen, Rosemary M; Sprague, Ann L; McNutt, Ralph L; Solomon, Sean C

    2008-07-04

    The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 +/- 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 +/- 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere.

  6. The Dependence of the Cerean Exosphere on Solar Energetic Particle Events

    Energy Technology Data Exchange (ETDEWEB)

    Villarreal, M. N.; Russell, C. T. [Earth, Planetary and Space Sciences, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1567 (United States); Luhmann, J. G. [Space Sciences Lab, University of California, Berkeley, CA (United States); Thompson, W. T. [Goddard Space Flight Center, Greenbelt, MD (United States); Prettyman, T. H. [Planetary Science Institute, Tucson, AZ (United States); A’Hearn, M. F. [University of Maryland, College Park, MD (United States); Küppers, M.; O’Rourke, L. [European Space Agency/European Space Astronomy Centre, Villanueva de la Cañada (Spain); Raymond, C. A., E-mail: mvillarreal@igpp.ucla.edu [Jet Propulsion Laboratory, Pasadena, CA (United States)

    2017-03-20

    Observations from Earth-based ground and orbiting telescopes indicate that the Ceres’s exosphere has a time-varying water component. Evidence of a transient atmosphere was also detected by Dawn upon its arrival, inferred from the response on the Gamma Ray and Neutron Detector. That atmosphere appeared shortly after the passage of a large enhancement in the local flux of high-energy solar protons. Solar proton events have highly variable fluxes over a range of proton energies from 10 s of keV to over 100 MeV and are capable of sputtering water ice at or near the surface. Herein, we examine the fluxes of solar energetic protons measured during Earth-based attempts to detect water vapor and OH in the Ceres’ atmosphere. We find that the presence of the cerean exosphere is correlated with the inferred presence of solar energetic protons at Ceres, consistent with the event detected by Dawn.

  7. Temporal Variability of Lunar Exospheric Helium During January 2012 from LRO/LAMP

    OpenAIRE

    Feldman, Paul D.; Hurley, Dana M.; Retherford, Kurt D.; Gladstone, G. Randall; Stern, S. Alan; Pryor, Wayne; Parker, Joel Wm.; Kaufmann, David E.; Davis, Michael W; Versteeg, Maarten; team, LAMP

    2012-01-01

    We report observations of the lunar helium exosphere made between December 29, 2011, and January 26, 2012, with the Lyman Alpha Mapping Project (LAMP) ultraviolet spectrograph on NASA's Lunar Reconnaissance Orbiter Mission (LRO). The observations were made of resonantly scattered He I 584 from illuminated atmosphere against the dark lunar surface on the dawn side of the terminator. We find no or little variation of the derived surface He density with latitude but day-to-day variations that li...

  8. High-Resolution Spectroscopic Observations of Potassium Emissions in the Lunar Exosphere

    Science.gov (United States)

    Robertson, Sarena D.; Oliversen, Ronald J.; Mierkiewicz, Edwin J.; Kuruppuaratchi, Dona Chathuni P.; Derr, Nicholas James; Gallant, Margaret A.; McFarland, Christina G.; Sarantos, Menelaos

    2018-01-01

    We investigate lunar exospheric potassium D1 emissions (7698.9646 Å) using high-resolution (R = 180,000 or 1.7 km/s) spectroscopy with our dual-etalon Fabry-Perot instrument to measure line widths and radial velocities. The Field of View (FOV) is 2 arcmins (~224 km at the mean lunar distance of 384,400 km) positioned tangent to the sunlit limb. The FOV placements are at cardinal directions from a variety of reference craters. All observations are collected at the National Solar Observatory McMath-Pierce Telescope in Kitt Peak, Arizona. The data are from several observations from 2014 through 2017 at various times of the year. Results are produced via a newly created automated data reduction using Python. Python was chosen as an open-source alternative to the previously used IDL and MATLAB scripts to decrease the cost of software licenses and maintenance. The potassium spectral line profiles provide a direct method to track exospheric effective temperatures and velocities. By monitoring the state of the potassium emissions over different lunar phases, solar activity, and the influx of meteor streams, we can constrain physical processes of sources and sinks at the lunar surface. Mechanisms that create the exosphere include photon-stimulated desorption, thermal evaporation, meteoroid impact vaporization, and ion sputtering via solar wind. In contrast, the exosphere is diminished due to the low lunar escape velocity, solar radiation pressure, and neutral gas being ionized and swept away by the interplanetary and terrestrial magnetic field. Preliminary analysis of 2017 data (January through June, excluding February) indicates an average potassium temperature of 1140 K but varying over the range of 550 K to 2000 K. Preliminary results from 2014 data depict a similar range of temperatures to that of 2017. Further analysis is expected for additional data from 2014 to later observations in 2017 that were not included in the initial set of models.

  9. Reconciling the dawn-dusk asymmetry in Mercury's exosphere with the micrometeoroid impact directionality

    OpenAIRE

    Pokorný, Petr; Sarantos, Menelaos; Janches, Diego

    2017-01-01

    Combining dynamical models of dust from Jupiter Family Comets and Halley-type Comets, we demonstrate that the seasonal variation of the dust/meteoroid environment at Mercury is responsible for producing the dawn-dusk asymmetry in Mercury's exosphere observed by the MESSENGER spacecraft. Our latest models, calibrated recently from ground-based and space-borne measurements, provide unprecedented statistics that enable us to study the longitudinal and latitudinal distribution of meteoroids impac...

  10. Photolysis of metal oxides as a source of atoms in planetary exospheres

    Science.gov (United States)

    Valiev, R. R.; Berezhnoy, A. A.; Sidorenko, A. D.; Merzlikin, B. S.; Cherepanov, V. N.

    2017-10-01

    The cross sections of photolysis of LiO, NaO, KO, MgO, and CaO molecules have been calculated by the use of quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides have the order of 10-17 cm2, and for alkaline earth metal monoxides these values are less on 1-2 orders of the magnitude. The lifetimes of photolysis at 1 astronomical unit are estimated as 5, 3, 60, 70, and 3,000 s for LiO, NaO, KO, MgO, and CaO, respectively. Typical kinetic energies of main peaks of photolysis-generated metal atoms are determined. Impact-produced LiO, NaO, KO, and MgO molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight while CaO molecule is more stable against destruction by photolysis. Photolysis-generated metal atoms in planetary exospheres can be detected by performing high-resolution spectral observations of velocity distribution of exospheric metal atoms.

  11. Interfacing MHD Single Fluid and Kinetic Exospheric Solar Wind Models and Comparing Their Energetics

    Science.gov (United States)

    Moschou, Sofia-Paraskevi; Pierrard, Viviane; Keppens, Rony; Pomoell, Jens

    2017-09-01

    An exospheric kinetic solar wind model is interfaced with an observation-driven single-fluid magnetohydrodynamic (MHD) model. Initially, a photospheric magnetogram serves as observational input in the fluid approach to extrapolate the heliospheric magnetic field. Then semi-empirical coronal models are used for estimating the plasma characteristics up to a heliocentric distance of 0.1 AU. From there on, a full MHD model that computes the three-dimensional time-dependent evolution of the solar wind macroscopic variables up to the orbit of Earth is used. After interfacing the density and velocity at the inner MHD boundary, we compare our results with those of a kinetic exospheric solar wind model based on the assumption of Maxwell and Kappa velocity distribution functions for protons and electrons, respectively, as well as with in situ observations at 1 AU. This provides insight into more physically detailed processes, such as coronal heating and solar wind acceleration, which naturally arise from including suprathermal electrons in the model. We are interested in the profile of the solar wind speed and density at 1 AU, in characterizing the slow and fast source regions of the wind, and in comparing MHD with exospheric models in similar conditions. We calculate the energetics of both models from low to high heliocentric distances.

  12. Short-term observations of double peaked Na emission from Mercury's exosphere

    Science.gov (United States)

    Massetti, Stefano; Mangano, Valeria; Milillo, Anna; Mura, Alessandro; Orsini, Stefano; Plainaki, Christina

    2017-04-01

    Analysis of a sequence of short-term ground-based observations of the Na emission from the exosphere of Mercury, recorded during three consecutive days (June 7-9, 2012), is presented. We observed a stable double-peak pattern where the exospheric Na emission was confined close to the nominal magnetospheric cusp footprints. During a series of scheduled observations of the global Na emission from the THEMIS telescope, achieved by scanning the whole planet's disc, we performed some extra measurements by recording the Na emission from a narrow North-South strip only, centred above the two Na emission peaks. When possible, these complementary measurements were recorded when the NASA Messenger spacecraft, orbiting around Mercury, was outside the planet's magnetosphere, in order to have contemporary in-situ data of the unperturbed interplanetary magnetic field. Our aim was to inspect the existence of short-term variabilities, which were never been reported before from ground-based observations, and their possible relationship with IMF variations. In spite of the fact that Mercury possess a miniature magnetosphere, characterized by fast reconnection events that develops on a timescale of few minutes (1-3 min), ground-based observations show that the exospheric Na emission pattern can be globally stable for a very prolonged period (some days), but it seems it can also shows variations in the time range of tens of minutes. In specific, we observed a decrease of the South/North ratio due to the decrease of the Na release from the southern cusp with respect to the northern one. This event lasted for about one hour, within several minor in-phase variations that involved both hemispheres.

  13. Plasma precipitation on Mercury's nightside and its implications for magnetospheric convection and exosphere generation.

    Science.gov (United States)

    Raines, J. M.; Slavin, J. A.; Tracy, P.; Gershman, D. J.; Zurbuchen, T.; Dewey, R. M.; Sarantos, M.

    2016-12-01

    Plasma impact onto Mercury's surface can be an important contributor to Mercury's exosphere through the process of ion sputtering. Under some circumstances, this process can produce a substantial fraction of the exosphere. When the impacting plasma originates from the magnetosphere itself, this sputtering process can conversely be considered as a sink for the plasma of the Mercury magnetosphere, providing evidence for the processes at work in that system. One such process is reconnection in Mercury's magnetotail, which can accelerate ions and electrons from the central plasma sheet toward the nightside of the planet. By analogy with processes at Earth, it is hypothesized that as these flows approach the planet, much of the plasma is diverted from impact onto the surface by the increasingly strong planetary magnetic field closer to the planet. The remainder of the plasma is expected to follow nearly dipolar field lines, impacting the nightside surface and potentially contributing to field-aligned currents. We present the first direct evidence that this process is operating at Mercury. We examine ion precipitation events on Mercury's nightside with the Fast Imaging Plasma Spectrometer (FIPS) on the MESSENGER spacecraft, which orbited Mercury from 2011 to 2015. We characterize the energy distributions of these events and their extent in latitude and local time. We use these observations to predict the precipitating proton flux from altitudes as low as 11 km. We use this information to bound the region of Mercury's surface that remains protected from plasma bombardment by the planetary dipole magnetic field, and to explore the implications of this information for magnetospheric convection and exosphere generation at Mercury.

  14. Mercury's Exosphere During MESSENGER's Second Flyby: Detection of Magnesium and Distinct Distributions of Neutral Species

    Science.gov (United States)

    McClintock, William E.; Vervack, Ronald J., Jr.; Bradley, E. Todd; Killen, Rosemary M.; Mouawad, Nelly; Sprague, Ann L.; Burger, Matthew H.; Solomon, Sean C.; Izenberg, Noam R.

    2009-01-01

    During MESSENGER's second Mercury flyby, the Mercury Atmospheric and Surface Composition Spectrometer observed emission from Mercury's neutral exosphere. These observations include the first detection of emission from magnesium. Differing spatial distributions for sodium, calcium, and magnesium were revealed by observations beginning in Mercury's tail region, approximately 8 Mercury radii anti-sunward of the planet, continuing past the nightside, and ending near the dawn terminator. Analysis of these observations, supplemented by observations during the first Mercury flyby as well as those by other MESSENGER instruments, suggests that the distinct spatial distributions arise from a combination of differences in source, transfer, and loss processes.

  15. Short-term observations of double-peaked Na emission from Mercury's exosphere

    Science.gov (United States)

    Massetti, S.; Mangano, V.; Milillo, A.; Mura, A.; Orsini, S.; Plainaki, C.

    2017-04-01

    We report the analysis of short-term ground-based observations of the exospheric Na emission (D1 and D2 lines) from Mercury, which was characterized by two high-latitude peaks confined near the magnetospheric cusp footprints. During a series of scheduled observations from the Télescope Héliographique pour l'Etude du Magnétisme et des Instabilités Solaires (THEMIS) telescope, achieved by scanning the whole planet, we implemented a series of extra measurements by recording the Na emission from a narrow north-south strip only, centered above the two emission peaks. Our aim was to inspect the existence of short-term variations, which were never analyzed before from ground-based observations, and their possible correlation with interplanetary magnetic field variations. Though Mercury possesses a miniature magnetosphere, characterized by fast reconnection events that develop on a timescale of few minutes, ground-based observations show that the exospheric Na emission pattern can be globally stable for a prolonged period (some days) and also exhibits fluctuations in the time range of tens of minutes.

  16. Imaging the Extended Hot Hydrogen Exosphere at Mars to Determine the Water Escape Rate

    Science.gov (United States)

    Bhattacharyya, Dolon

    2017-08-01

    ACS SBC imaging of the extended hydrogen exosphere of Mars is proposed to identify the hot hydrogen population present in the exosphere of Mars. Determining the characteristics of this population and the underlying processes responsible for its production are critical towards constraining the escape flux of H from Mars, which in turn is directly related to the water escape history of Mars. Since the hot atoms appear mainly at high altitudes, these observations will be scheduled when Mars is far from Earth allowing us to image the hot hydrogen atoms at high altitudes where they dominate the population. The altitude coverage by HST will extend beyond 30,000 km or 8.8 Martian radii in this case, which makes it perfect for this study as orbiting spacecraft remain at low altitudes (MAVEN apoapse is 6000 km) and cannot separate hot atoms from the thermal population at those altitudes. The observations will also be carried out when Mars is near aphelion, the atmospheric temperature is low, and the thermal population has a small scale height, allowing the clear characterization of the hot hydrogen layer. Another advantage of conducting this study in this cycle is that the solar activity is near its minimum, allowing us to discriminate between changes in the hot hydrogen population from processes taking place within the atmosphere of Mars and changes due to external drivers like the solar wind, producing this non-thermal population. This proposal is part of the HST UV initiative.

  17. Variability of helium, neon, and argon in the lunar exosphere as observed by the LADEE NMS instrument

    National Research Council Canada - National Science Library

    Benna, M; Mahaffy, P. R; Halekas, J. S; Elphic, R. C; Delory, G. T

    2015-01-01

    .... Helium was found to be controlled by the supply of solar wind alpha particles and by the presence of an endogenous source that supplies the exosphere at a rate of 1.9 × 10 23  atoms s −1...

  18. Long-Range Transhorizon Lunar Surface Radio Wave Propagation in the Presence of a Regolith and a Sparse Exospheric Plasma

    Science.gov (United States)

    Manning, Robert M.

    2008-01-01

    Long-range, over-the-horizon (transhorizon) radio wave propagation is considered for the case of the Moon. In the event that relay satellites are not available or otherwise unwarranted for use, transhorizon communication provides for a contingency or backup option for non line-of-sight lunar surface exploration scenarios. Two potential low-frequency propagation mechanisms characteristic of the lunar landscape are the lunar regolith and the photoelectron induced plasma exosphere enveloping the Moon. Although it was hoped that the regolith would provide for a spherical waveguide which could support a trapped surface wave phenomena, it is found that, in most cases, the regolith is deleterious to long range radio wave propagation. However, the presence of the plasma of the lunar exosphere supports wave propagation and, in fact, surpasses the attenuation of the regolith. Given the models of the regolith and exosphere adopted here, it is recommended that a frequency of 1 MHz be considered for low rate data transmission along the lunar surface. It is also recommended that further research be done to capture the descriptive physics of the regolith and the exospheric plasma so that a more complete model can be obtained. This comprehensive theoretical study is based entirely on first principles and the mathematical techniques needed are developed as required; it is self-contained and should not require the use of outside resources for its understanding.

  19. Lunar exospheric helium observations of LRO/LAMP coordinated with ARTEMIS

    Science.gov (United States)

    Grava, C.; Retherford, K. D.; Hurley, D. M.; Feldman, P. D.; Gladstone, G. R.; Greathouse, T. K.; Cook, J. C.; Stern, S. A.; Pryor, W. R.; Halekas, J. S.; Kaufmann, D. E.

    2016-07-01

    We present results from Lunar Reconnaissance Orbiter's (LRO) UV spectrograph LAMP (Lyman-Alpha Mapping Project) campaign to study the lunar atmosphere. Several off-nadir maneuvers (lateral rolls) were performed to search for resonantly scattering species, increasing the illuminated line-of-sight (and hence the signal from atoms resonantly scattering the solar photons) compared to previously reported LAMP's "twilight observations" (Cook, J.C., Stern, S.A. [2014]. Icarus 236, 48-55). Helium was the only element distinguishable on a daily basis, and we present latitudinal profiles of its line-of-sight column density in December 2013. We compared the helium line-of-sight column densities with solar wind alpha particle fluxes measured from the ARTEMIS (Acceleration, Reconnection, Turbulence, & Electrodynamics of Moon's Interaction with the Sun) twin spacecraft. Our data show a correlation with the solar wind alpha particle flux, confirming that the solar wind is the main source of the lunar helium. We also support the finding by Benna et al. (Benna, M. et al. [2015]. Geophys. Res. Lett. 42, 3723-3729) and Hurley et al. (Hurley, D.M. et al. [2015]. Icarus, this issue), that a non-zero contribution from endogenic helium, coming from radioactive decay of 232Th and 238U, is present. Moreover, our results suggest that not all of the incident alpha particles are converted to thermalized helium, allowing for a non-negligible fraction to escape as suprathermal helium or simply backscattered from the lunar surface. We compare LAMP-derived helium surface density with the one recorded by the mass spectrometer LACE (Lunar Atmospheric Composition Experiment) deployed on the lunar surface during the Apollo 17 mission, finding good agreement between the two measurements. The LRO/LAMP roll observations presented here are in agreement with the most recent lunar exospheric helium model (Hurley, D.M. et al. [2015]. Icarus, this issue) around mid- to high-latitudes (50-70°) regardless of

  20. Reconciling the Dawn-Dusk Asymmetry in Mercury’s Exosphere with the Micrometeoroid Impact Directionality

    Science.gov (United States)

    Pokorny, Petr; Sarantos, Menelaos; Janches, Diego

    2017-10-01

    Combining dynamical models of dust from Jupiter-family comets and Halley-type comets, we demonstrate that the seasonal variation of the dust/meteoroid environment at Mercury is responsible for producing the dawn-dusk asymmetry in Mercury’s exosphere observed by the MESSENGER spacecraft. Our latest models, calibrated recently from ground-based and space-borne measurements, provide unprecedented statistics that enable us to study the longitudinal and latitudinal distribution of meteoroids impacting Mercury’s surface. We predict that the micrometeoroid impact vaporization source is expected to undergo significant motion on Mercury’s surface toward the nightside during Mercury’s approach to aphelion and toward the dayside when the planet is approaching the Sun.

  1. Plasma transport modelling in the inner magnetosphere: effects of magnetic field, electric field and exospheric models

    Directory of Open Access Journals (Sweden)

    A. Woelfflé

    2011-02-01

    Full Text Available A qualitative study is performed on plasma transport modelling in the inner magnetosphere, revealing the significance of a model use choice and its parameterization. First, we examine particle transport using comparative analysis of both magnetic and electric field models. This work reveals that the electric field plays an important role in understanding particle dynamics and the models lead to various results in terms of plasma source, energy and particle trajectory. We then concentrate particularly on proton loss assessment considering the charge exchange phenomenon. For that, models are needed to provide a neutral hydrogen density estimation. So, exospheric models were tested in light of the Dynamics Explorer 1 measurements analysed by Rairden.

  2. Observations of Titanium, Aluminum and Magnesium in the Lunar Exosphere by LADEE UVS

    Science.gov (United States)

    Colaprete, A.; Wooden, D.; Cook, A.; Shirley, M.; Sarantos, M.

    2016-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) was an orbital lunar science mission designed to address the goals of the 2003 National Research Council decadal survey, the Lunar Exploration Analysis Group Roadmap, and the "Scientific Context for Exploration of the Moon" (SCEM) report, and has been recommended for execution by the 2011 Planetary Missions Decadal Survey. The LADEE mission goal was to determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. It will monitor variations in known gasses, such as sodium, potassium, argon and helium, and will search for other, as-yet-undetected gasses of both lunar and extra-lunar origin. Another goal of LADEE was to determine whether dust is present in the lunar exosphere, and reveal the processes that contribute to its sources and variability.

  3. LRO/LAMP Observations of Temporal Variability of Lunar Exospheric Helium During June and July 2012

    Science.gov (United States)

    Feldman, P. D.; Hurley, D. M.; Retherford, K. D.; Gladstone, R.; Stern, S. A.; Pryor, W. R.; Parker, J.

    2012-12-01

    We have previously reported on observations of the lunar helium exosphere made in January 2012 with the Lyman Alpha Mapping Project (LAMP) ultraviolet spectrograph on NASA's Lunar Reconnaissance Orbiter Mission. Those observations, of resonantly scattered He I emission at 584 Å from illuminated atmosphere against the dark lunar surface, were made over the night side of the Moon within 30 degrees of the dawn terminator. During June-July 2012 these observations were repeated, this time including both the dusk and dawn terminators. We find temporal variability of the derived surface He density as well as a strong dawn/dusk asymmetry with the He density on the dawn side approximately a factor of three higher than at corresponding longitudes on the dusk side. We again observe a factor of two decrease in surface density during the passage of the Moon through the Earth's magnetotail.

  4. Temporal variability of lunar exospheric helium during January 2012 from LRO/LAMP

    Science.gov (United States)

    Feldman, Paul D.; Hurley, Dana M.; Retherford, Kurt D.; Gladstone, G. Randall; Stern, S. Alan; Pryor, Wayne; Parker, Joel Wm.; Kaufmann, David E.; Davis, Michael W.; Versteeg, Maarten H.; LAMP Team

    2012-11-01

    We report observations of the lunar helium exosphere made between December 29, 2011, and January 26, 2012, with the Lyman Alpha Mapping Project (LAMP) ultraviolet spectrograph on NASA’s Lunar Reconnaissance Orbiter Mission (LRO). The observations were made of resonantly scattered He Iλ584 from illuminated atmosphere against the dark lunar surface on the dawn side of the terminator. We find no or little variation of the derived surface He density with latitude but day-to-day variations that likely reflect variations in the solar wind alpha flux. The five-day passage of the Moon through the Earth’s magnetotail results in a factor of two decrease in surface density, which is well explained by model simulations.

  5. Detection of a southern peak in Mercury's sodium exosphere with the TNG in 2005

    Science.gov (United States)

    Mangano, V.; Leblanc, F.; Barbieri, C.; Massetti, S.; Milillo, A.; Cremonese, G.; Grava, C.

    2009-06-01

    A long term plan of observations of the sodium exosphere of Mercury began in 2002 by using the high resolution echelle spectrograph SARG and a devoted sodium filter at the 3.5 m Galileo National Telescope (TNG) located in La Palma, Canary Islands. This program is meant to investigate the variations of the sodium exosphere appearance under different conditions of observations, namely Mercury's position along its orbit, phase angle and different solar conditions, as reported by previous observations in August 2002 and August 2003 [Barbieri, C., Verani, S., Cremonese, G., Sprague, A., Mendillo, M., Cosentino, R., Hunten, D., 2004. Planet. Space Sci. 52, 1169-1175; Leblanc, F., Barbieri, C., Cremonese, G., Verani, S., Cosentino, R., Mendillo, M., Sprague, A., Hunten, D., 2006. Icarus 185 (2), 395-402]. Here we present the analysis of data taken in June 29th and 30th and in July 1st 2005, when Mercury's true anomaly angle (TAA) was in the range 124-130°. The spectra show particularly intense sodium lines with a distinctive peak in emission localized in the southern hemisphere at mid-latitudes. This seems to be a persistent feature related to consecutive favorable IMF conditions inducing localized enhancements of surface sodium density. The comparison with previous data taken by Potter et al. [Potter, A.E., Killen, R.M., Morgan, T.H., 2002. Meteorit. Planet. Sci. 37 (9), 1165-1172] evidences a surprising consistency of the anti-sunward component, which appears to remain constant regardless of the changing illumination and space weather conditions at Mercury.

  6. Evidence for a Localized Source of the Argon in the Lunar Exosphere

    Science.gov (United States)

    Kegerreis, Jacob A.; Eke, Vincent R.; Massey, Richard J.; Beaumont, Simon K.; Elphic, Rick C.; Teodoro, Luís. F.

    2017-10-01

    We perform the first tests of various proposed explanations for observed features of the Moon's argon exosphere, including models of the following: spatially varying surface interactions; a source that reflects the lunar near-surface potassium distribution; and temporally varying cold trap areas. Measurements from the Lunar Atmosphere and Dust Environment Explorer (LADEE) and the Lunar Atmosphere Composition Experiment (LACE) are used to test whether these models can reproduce the data. The spatially varying surface interactions hypothesized in previous work cannot reproduce the persistent argon enhancement observed over the western maria. They also fail to match the observed local time of the near-sunrise peak in argon density, which is the same for the highland and mare regions and is well reproduced by simple surface interactions with a ubiquitous desorption energy of 28 kJ mol-1. A localized source can explain the observations, with a trade-off between an unexpectedly localized source or an unexpectedly brief lifetime of argon atoms in the exosphere. To match the observations, a point-like source requires source and loss rates of ˜1.9 × 1021 atoms s-1. A more diffuse source, weighted by the near-surface potassium, requires much higher rates of ˜1.1 × 1022 atoms s-1, corresponding to a mean lifetime of just 1.4 lunar days. We do not address the mechanism for producing a localized source, but demonstrate that this appears to be the only model that can reproduce the observations. Large, seasonally varying cold traps could explain the long-term fluctuation in the global argon density observed by LADEE, but not that by LACE.

  7. LADEE UVS (UltraViolet Visible Spectrometer) and the Search for Lunar Exospheric Dust: A Detailed Spectral Analysis

    Science.gov (United States)

    Wooden, Diane H.; Cook, Amanda; Colaprete, Anthony; Shirley, Mark; Vargo, Kara; Elphic, Richard C.; Hermalyn, Brendan; Stubbs, Timothy John; Glenar, David A.

    2014-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) executed science observations in lunar orbit spanning 2013-Oct-16- 2014-04-18 UT. LADEE's Ultraviolet/Visible Spectrometer (UVS) studies the composition and temporal variations of the tenuous lunar exosphere and dust environment, utilizing two sets of optics: a limb-viewing telescope, and a solar-viewer. The limb-viewing telescope observes illuminated dust and emitting gas species while the Sun is just behind the lunar limb. The solar viewer, with its diffuser, allows UVS to also stare directly at the solar disk as it approaches the limb, sampling progressively lower exosphere altitudes. Solar viewer "Occultation" activities occur at the lunar sunrise limb, as the LADEE spacecraft passes into the lunar night side, facing the Sun (the spacecraft orbit is near-equatorial retrograde). A loss of transmission of sunlight occurs by the occultation of dust grains along the line-of-sight. So-called "Inertial Limb" activities have the limb-viewing telescope pointed at the lit exosphere just after the Sun has set. Inertial Limb activities follow a similar progression of diminishing sampling altitudes but hold the solar elongation angle constant so the zodiacal light contribution remains constant while seeking to observe the weak lunar horizon glow. On the dark side of the moon, "Sodium Tail" activities pointed the limb-viewing telescope in the direction of the Moon's sodium tail (similar to anti-sunward), during different lunar phases. Of the UVS data sets, these show the largest excess of scattered blue light, indicative of the presence of small (approximately 100 nm) dust grains in the tail. Correlations are sought between dust in the sodium tail and meteor streams and magnetotail crossings to investigate impact- versus electrostatic-lofting. Once lofted, nanoparticles can become charged and picked up by the solar wind. The LADEE UVS Occultation, Inertial Limb, and Sodium Tail spectral datasets provide evidence of

  8. In-situ observation of Martian neutral exosphere: Results from MENCA aboard Indian Mars Orbiter Mission (MOM)

    Science.gov (United States)

    Bhardwaj, Anil; Pratim Das, Tirtha; Dhanya, M. B.; Thampi, Smitha V.

    2016-07-01

    Till very recently, the only in situ measurements of the Martian upper atmospheric composition was from the mass spectrometer experiments aboard the two Viking landers, which covered the altitude region from 120 to 200 km. Hence, the exploration by the Mars Exospheric Neutral Composition Analyser (MENCA) aboard the Mars Orbiter Mission (MOM) spacecraft of ISRO and the Neutral Gas and Ion Mass Spectrometer (NGIMS) experiment aboard the Mars Atmosphere and Volatile ENvironment (MAVEN) mission of NASA are significant steps to further understand the Martian neutral exosphere and its variability. MENCA is a quadrupole based neutral mass spectrometer which observes the radial distribution of the Martian neutral exosphere. The analysis of the data from MENCA has revealed unambiguous detection of the three major constituents, which are amu 44 (CO2), amu 28 (contributions from CO and N2) and amu 16 (atomic O), as well as a few minor species. Since MOM is in a highly elliptical orbit, the MENCA observations pertain to different local times, in the low-latitude region. Examples of such observations would be presented, and compared with NGIMS results. Emphasis would be given to the observations pertaining to high solar zenith angles and close to perihelion period. During the evening hours, the transition from CO2 to O dominated region is observed near 270 km, which is significantly different from the previous observations corresponding to sub-solar point and SZA of ~45°. The mean evening time exospheric temperature derived using these observations is 271±5 K. These are the first observations corresponding to the Martian evening hours, which would help to provide constraints to the thermal escape models.

  9. Seasonal Changes in Hydrogen Escape From Mars Through Analysis of HST Observations of the Martian Exosphere Near Perihelion

    Science.gov (United States)

    Bhattacharyya, D.; Clarke, J. T.; Chaufray, J. Y.; Mayyasi, M.; Bertaux, J. L.; Chaffin, M. S.; Schneider, N. M.; Villanueva, G. L.

    2017-11-01

    Hubble Space Telescope (HST) observations of the Martian hydrogen exosphere in Lyman α are presented in this paper for a period when Mars passed perihelion and southern summer solstice in its orbit. The peak intensity in the exospheric Lyman α brightness was recorded after Mars went past its perihelion, slightly after southern summer solstice. The increase in brightness as Mars approached perihelion was found to not be symmetric around the peak, making it impossible to fit the H escape flux trend with a single sinusoidal curve with the peak at perihelion. While the short-term ( 30 Earth days) changes were not directly correlated with changes in the solar Lyman α flux, the long-term ( 10 Earth years) trend in the data does show some correlation with solar activity. This suggests that the short-term changes brought about in the exosphere could be due to intrinsic changes occurring within the lower atmosphere. For example, thermospheric heating by dust can alter the cold-trapping mechanism for water vapor resulting in it being present in large quantities at higher altitudes (60-80 km), possibly enhancing the escape flux of H. Therefore, it is important to understand the drivers of atmospheric dynamics in the Martian atmosphere, which produce the yearly enhanced seasonal changes observed at Mars around periapsis and southern summer solstice in order to accurately determine the total amount of water lost over its history.

  10. ROSAT Observations of Soft X-ray Emission from the Solar Wind Interaction with the Lunar Exosphere

    Science.gov (United States)

    Collier, Michael

    We analyze the ROSAT PSPC soft X-ray image of the moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the antisolar point. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now along with Mars, Venus, and Earth, the moon represents another solar system body at which solar wind charge exchange has been observed.

  11. A Seasonal Feature in Mercury's Exosphere Caused by Meteoroids from Comet Encke

    Science.gov (United States)

    Burger, M. H.; Christou, A.; Killen, R. M.

    2015-12-01

    The planet Mercury is enveloped in a tenuous atmosphere, the result of a delicate balance between poorly understood sources and sinks (Killen et al, 2007). Meteoroid impacts are a contributing source process (eg Wurz et al, 2010), but their importance compared to other production mechanisms is uncertain. Killen and Hahn (2015) found that seasonal variations in Mercury's calcium exosphere as observed by the MASCS spectrometer onboard the MESSENGER spacecraft (Burger et al, 2014) may be due to impact vaporization of surface material by the infall of interplanetary dust. However, an additional dust source was required to explain a Ca excess at a True Anomaly Angle (TAA) of 25±5 deg. Killen and Hahn suggested that dust from comet 2P/Encke, crossing Mercury's orbital plane at TAA=45 deg, may be the culprit. We have simulated numerically the stream of meteoroids ejected from Encke to test the Killen and Hahn conjecture. We find that Encke particles evolving solely under the gravity of the major planets and the Sun encounter Mercury at TAA=50-60 deg, well after the peak of the Ca excess emission. However, the addition of Poynting-Robertson (P-R) drag in our model couples the age and size of the meteoroids to the TAA at encounter, causing smaller, older particles to encounter Mercury progressively earlier in the Hermean year. In particular, mm-sized grains ejected between 10 and 20 kyr ago impact on the nightside hemisphere of Mercury at TAA = 350-30 deg, near the observed peak time of the exospheric feature. During this presentation, we will describe our model results and discuss their implications for the physical mechanism that injects impact-liberated Ca into sunlight as well as the origin and evolution of the Encke stream of meteoroids. Astronomical research at the Armagh Observatory is funded by the Northern Ireland Department of Culture, Arts and Leisure (DCAL). RMK was supported by NASA Grant NNX07AR78G-S01 as a Participating Scientist on the NASA MESSENGER

  12. Saturn Neutron Exosphere as Source for Inner and Innermost Radiation Belts

    Science.gov (United States)

    Cooper, John; Lipatov, Alexander; Sittler, Edward; Sturner, Steven

    2011-01-01

    Energetic proton and electron measurements by the ongoing Cassini orbiter mission are expanding our knowledge of the highest energy components of the Saturn magnetosphere in the inner radiation belt region after the initial discoveries of these belts by the Pioneer 11 and Voyager 2 missions. Saturn has a neutron exosphere that extends throughout the magnetosphere from the cosmic ray albedo neutron source at the planetary main rings and atmosphere. The neutrons emitted from these sources at energies respectively above 4 and 8 eV escape the Saturn system, while those at lower energies are gravitationally bound. The neutrons undergo beta decay in average times of about 1000 seconds to provide distributed sources of protons and electrons throughout Saturn's magnetosphere with highest injection rates close to the Saturn and ring sources. The competing radiation belt source for energetic electrons is rapid inward diffusion and acceleration of electrons from the middle magnetosphere and beyond. Minimal losses during diffusive transport across the moon orbits, e.g. of Mimas and Enceladus, and local time asymmetries in electron intensity, suggest that drift resonance effects preferentially boost the diffusion rates of electrons from both sources. Energy dependences of longitudinal gradient-curvature drift speeds relative to the icy moons are likely responsible for hemispheric differences (e.g., Mimas, Tethys) in composition and thermal properties as at least partly produced by radiolytic processes. A continuing mystery is the similar radial profiles of lower energy (belt region. Either the source of these lower energy protons is also neutron decay, but perhaps alternatively from atmospheric albedo, or else all protons from diverse distributed sources are similarly affected by losses at the moon' orbits, e.g. because the proton diffusion rates are extremely low. Enceladus cryovolcanism, and radiolytic processing elsewhere on the icy moon and ring surfaces, are additional

  13. Development of a miniature microwave electron cyclotron resonance plasma ion thruster for exospheric micro-propulsion.

    Science.gov (United States)

    Dey, Indranuj; Toyoda, Yuji; Yamamoto, Naoji; Nakashima, Hideki

    2015-12-01

    A miniature microwave electron cyclotron resonance plasma source [(discharge diameter)/(microwave cutoff diameter) micro-propulsion applications in the exosphere. The discharge source uses both radial and axial magnetostatic field confinement to facilitate electron cyclotron resonance and increase the electron dwell time in the volume, thereby enhancing plasma production efficiency. Performance of the ion thruster is studied at 3 microwave frequencies (1.2 GHz, 1.6 GHz, and 2.45 GHz), for low input powers (<15 W) and small xenon mass flow rates (<40 μg/s), by experimentally measuring the extracted ion beam current through a potential difference of ≅1200 V. The discharge geometry is found to operate most efficiently at an input microwave frequency of 1.6 GHz. At this frequency, for an input power of 8 W, and propellant (xenon) mass flow rate of 21 μg/s, 13.7 mA of ion beam current is obtained, equivalent to an calculated thrust of 0.74 mN.

  14. Observations of the Minor Species Al, Fe and Ca(+) in Mercury's Exosphere

    Science.gov (United States)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report the first detections of Al and Fe, and strict upper limits for Ca(+) in the exosphere of Mercury, using the HIRES spectrometer at the Keck I telescope. We report observed 4-sigma tangent columns of 1.5x10(exp 7) Al atoms per square centimeter at an altitude of 1220 km (1.5 Mercury radii (R(sub M)) from planet center), and that for Fe of 1.6 x 10 per square centimeter at an altitude of 950 km (1.4 R(sub M)). The observed 3-sigma Ca(+) column was 3.9x10(exp 6) ions per square centimeter at an altitude of 1630 km (1.67 R(sub M). A simple model for zenith column abundances of the neutral species were 9.5 x 10(exp 7) Al per square centimeter, and 3.0 x 10(exp 8) Fe per square centimeter. The observations appear to be consistent with production of these species by impact vaporization with a large fraction of the ejecta in molecular form. The scale height of the Al gas is consistent with a kinetic temperature of 3000 - 9000 K while that of Fe is 10500 K. The apparent high temperature of the Fe gas would suggest that it may be produced by dissociation of molecules. A large traction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  15. Structure and Composition of the Distant Lunar Exosphere: Constraints from ARTEMIS Observations of Ion Acceleration in Time-Varying Fields

    Science.gov (United States)

    Halekas, J. S.; Poppe, A. R.; Farrell, W. M.; McFadden, J. P.

    2016-01-01

    By analyzing the trajectories of ionized constituents of the lunar exosphere in time-varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two-probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time-dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes 3000-5000 km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40 amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

  16. A dynamo theory prediction for solar cycle 22 - Sunspot number, radio flux, exospheric temperature, and total density at 400 km

    Science.gov (United States)

    Schatten, K. H.; Hedin, A. E.

    1984-01-01

    Using the 'dynamo theory' method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent.

  17. A dynamo theory prediction for solar cycle 22: Sunspot number, radio flux, exospheric temperature, and total density at 400 km

    Science.gov (United States)

    Schatten, K. H.; Hedin, A. E.

    1986-01-01

    Using the dynamo theory method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent.

  18. LADEE UVS (UltraViolet Visible Spectrometer) and the Search for Lunar Exospheric Dust: A Detailed Spectral Analysis

    Science.gov (United States)

    Wooden, D. H.; Cook, A.; Colaprete, A.; Shirley, M.; Vargo, K.; Elphic, R. C.; Hermalyn, B.; Stubbs, T. J.; Glenar, D. A.

    2014-12-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) executed science observations in lunar orbit spanning 2013-Oct-16- 2014-04-18 UT. LADEE's Ultraviolet/Visible Spectrometer (UVS) studies the composition and temporal variations of the tenuous lunar exosphere and dust environment, utilizing two sets of optics: a limb-viewing telescope, and a solar-viewer. The limb-viewing telescope observes illuminated dust and emitting gas species while the Sun is just behind the lunar limb. The solar viewer, with its diffuser, allows UVS to also stare directly at the solar disk as it approaches the limb, sampling progressively lower exosphere altitudes. Solar viewer "Occultation" activities occur at the lunar sunrise limb, as the LADEE spacecraft passes into the lunar night side, facing the Sun (the spacecraft orbit is near-equatorial retrograde). A loss of transmission of sunlight occurs by the occultation of dust grains along the line-of-sight [1, 2]. So-called "Inertial Limb" activities have the limb-viewing telescope pointed at the lit exosphere just after the Sun has set. Inertial Limb activities follow a similar progression of diminishing sampling altitudes but hold the solar elongation angle constant so the zodiacal light contribution remains constant while seeking to observe the weak lunar horizon glow [2,3,4]. On the dark side of the moon, "Sodium Tail" activities pointed the limb-viewing telescope in the direction of the Moon's sodium tail (~anti-sunward), during different lunar phases. Of the UVS data sets, these show the largest excess of scattered blue light, indicative of the presence of small (~100 nm) dust grains in the tail. Correlations are sought between dust in the sodium tail and meteor streams [5] and magnetotail [3] crossings to investigate impact- versus electrostatic-lofting [6]. Once lofted, nanoparticles can become charged and picked up by the solar wind [7,8]. The LADEE UVS Occultation, Inertial Limb, and Sodium Tail spectral datasets provide

  19. Space Weathering of Super-Earths: Model Simulations of Exospheric Sodium Escape from 61 Virgo b

    Energy Technology Data Exchange (ETDEWEB)

    Yoneda, M.; Berdyugina, S.; Kuhn, J. [Kiepenheuer Institute for Solar Physics, Schöneckstraße 6, 79104 Freiburg im Breisgau (Germany)

    2017-10-01

    Rocky exoplanets are expected to be eroded by space weather in a similar way as in the solar system. In particular, Mercury is one of the dramatically eroded planets whose material continuously escapes into its exosphere and further into space. This escape is well traced by sodium atoms scattering sunlight. Due to solar wind impact, micrometeorite impacts, photo-stimulated desorption and thermal desorption, sodium atoms are released from surface regolith. Some of these released sodium atoms are escaping from Mercury’s gravitational-sphere. They are dragged anti-Sun-ward and form a tail structure. We expect similar phenomena on exoplanets. The hot super-Earth 61 Vir b orbiting a G3V star at only 0.05 au may show a similar structure. Because of its small separation from the star, the sodium release mechanisms may be working more efficiently on hot super-Earths than on Mercury, although the strong gravitational force of Earth-sized or even more massive planets may be keeping sodium atoms from escaping from the planet. Here, we performed model simulations for Mercury (to verify our model) and 61 Vir b as a representative super-Earth. We have found that sodium atoms can escape from this exoplanet due to stellar wind sputtering and micrometeorite impacts, to form a sodium tail. However, in contrast to Mercury, the tail on this hot super-Earth is strongly aligned with the anti-starward direction because of higher light pressure. Our model suggests that 61 Vir b seems to have an exo-base atmosphere like that of Mercury.

  20. A Concept for Small, Remotely Operated, Coronagraph located at Small Observatory to Obtain Frequent Low-cost Remote Observations of the Lunar Exosphere and the Mercurian Tail

    Science.gov (United States)

    Morgan, T. H.; Plymate, C.; Potter, A. E.; Killen, R. M.

    2011-01-01

    The sodium in the lunar exosphere is a marker species for studying the lunar exosphere because the element possesses two strong resonance transitions from the ground state whose wavelengths fall in the visible spectrum near 590 nm. Emissions at these wavelengths are thus, observable from Earth. Observations have shown that the exosphere responds in a complex way to the external processes (impact vaporization, sputtering, and photon stimulated desorption) that weather the lunar regolith to produce the sodium. Unraveling the sodium production allows us to study the processes that weather the regolith. Obtaining the extensive time sequence of observations required to unravel the sources of sodium using conventional observatories is impractical, and too expensive. Effectively imaging the lunar sodium exosphere dose to the Moon requires an off-axis rejection of scattered light that can only be obtained with a coronagraph. A related problem. the observation of the sodium tail of Mercury, can be addressed as well only by coronagraphic observations. We present here a concept for a small, rugged coronagraph sited at an observatory dedicated to remote robotic observing (the Winer Observatory in Sonoita Arizona) that can obtain the quality and quantity of lunar sodium observations needed to answer these questions. The design uses Commercial Off the Shelf Technology (COTS). If this facility is operational by 2013. the observations will be concurrent with the Lunar Atmosphere and Dust Environment Explorer (LADEE) mission.

  1. No hydrogen exosphere detected around the super-Earth HD 97658 b

    Science.gov (United States)

    Bourrier, V.; Ehrenreich, D.; King, G.; Lecavelier des Etangs, A.; Wheatley, P. J.; Vidal-Madjar, A.; Pepe, F.; Udry, S.

    2017-01-01

    The exoplanet HD 97658 b provides a rare opportunity to probe the atmospheric composition and evolution of moderately irradiated super-Earths. It transits a bright K star at a moderate orbital distance of 0.08 au. Its low density is compatible with a massive steam envelope that could photodissociate at high altitudes and become observable as escaping neutral hydrogen. Our analysis of three transits with HST/STIS at Lyman-α reveals no such signature, suggesting that the thermosphere of HD 97658 b is not hydrodynamically expanding and is subjected to a low escape of neutral hydrogen (<108 g s-1 at 3σ). Using HST/STIS Lyman-α observations and Chandra/ACIS-S and XMM-Newton/EPIC X-ray observations at different epochs, we find that HD 97658 is in fact a weak and soft X-ray source with signs of chromospheric variability in the Lyman-α line core. We determine an average reference for the intrinsic Lyman-α line and X-EUV (XUV) spectrum of the star, and show that HD 97658 b is in mild conditions of irradiation compared to other known evaporating exoplanets with an XUV irradiation about three times lower than the evaporating warm Neptune GJ436 b. This could be the reason why the thermosphere of HD 97658 b is not expanding: the low XUV irradiation prevents an efficient photodissociation of any putative steam envelope. Alternatively, it could be linked to a low hydrogen content or inefficient conversion of the stellar energy input. The HD 97658 system provides clues for understanding the stability of low-mass planet atmospheres in terms of composition, planetary density, and irradiation. Our study of HD 97658 b can be seen as a control experiment of our methodology, confirming that it does not bias detections of atmospheric escape and underlining its strength and reliability. Our results show that stellar activity can be efficiently discriminated from absorption signatures by a transiting exospheric cloud. They also highlight the potential of observing the upper atmosphere

  2. Two-dimensional description of surface-bounded exospheres with application to the migration of water molecules on the Moon

    Science.gov (United States)

    Schorghofer, Norbert

    2015-05-01

    On the Moon, water molecules and other volatiles are thought to migrate along ballistic trajectories. Here, this migration process is described in terms of a two-dimensional partial differential equation for the surface concentration, based on the probability distribution of thermal ballistic hops. A random-walk model, a corresponding diffusion coefficient, and a continuum description are provided. In other words, a surface-bounded exosphere is described purely in terms of quantities on the surface, which can provide computational and conceptual advantages. The derived continuum equation can be used to calculate the steady-state distribution of the surface concentration of volatile water molecules. An analytic steady-state solution is obtained for an equatorial ring; it reveals the width and mass of the pileup of molecules at the morning terminator.

  3. Development of a mass spectrometer for planetary exosphere exploration: from simulations to a flight like design

    Science.gov (United States)

    Meyer, Stefan; Tulej, Marek; Wurz, Peter

    2017-04-01

    The exploration of habitable environments around the gas giants in the Solar System is of major interest in upcoming planetary missions. Exactly this theme is addressed by the Jupiter Icy Moons Explorer (JUICE) mission of ESA, which will characterise Ganymede, Europa and Callisto as planetary objects and potential habitats [1], [2]. We developed a prototype of the Neutral gas and Ion Mass spectrometer (NIM) of the Particle Environment Package (PEP) for the JUICE mission intended for composition measurements of neutral gas and thermal plasma [3]. NIM/PEP will be used to measure the chemical composition of the exospheres of the icy Jovian moons. Besides direct ion measurement, the NIM instrument is able to measure the inflowing neutral gas in two different modes: in neutral mode the gas enters directly the ion source (open source) and in thermal mode, the gas gets thermally accommodated to wall temperature by several collisions inside an equilibrium sphere before entering the ion source (closed source). We started the development of NIM with detailed ion-optical simulations and optimisations using SIMION software. Based on the ion-optical design we developed a prototype of NIM with several iterations. We tested the prototype NIM under realistic mission conditions and thereby successfully verified its required functionality. We will present the development process from ion-optical simulation up to NIM prototype test results and the concluded flight like design. Furthermore, we will provide an insight into the working principle of NIM and its performance, based on measurement data. References: 1) ESA, "JUICE assessment study report (Yellow Book)", ESA/SRE(2011)18, 2012. 2) O. Grasset, M.K. Dougherty, A. Coustenis, E.J. Bunce, C. Erd, D. Titov, M. Blanc, A. Coates, P. Drossart, L.N. Fletcher, H. Hussmann, R. Jaumann, N. Krupp, J.-P. Lebreton, O. Prieto-Ballesteros, P. Tortora, F. Tosi, T. Van Hoolst, "JUpiter Icy moons Explorer (JUICE): An ESA mission to orbit Ganymede

  4. Upper limit of helium-4 in the sunlit lunar exosphere during magnetotail passage under low solar wind condition: Result from CHACE aboard MIP in Chandrayaan-1

    Science.gov (United States)

    Das, Tirtha Pratim; Thampi, Smitha V.; Dhanya, M. B.; Bhardwaj, Anil; Ahmed, S. M.; Sridharan, R.

    2017-11-01

    The outcome of efforts to detect He-4 in the sunlit lunar exosphere as evinced by the CHACE mass spectrometer aboard the Moon Impact Probe in Chandrayaan-1 is reported. The in situ observations by CHACE were carried out in the lunar dayside, covering a broad range of lunar latitudes, when the Moon was on the verge of exiting the Earth's magnetotail. A combination of daytime He depletion and decrease during magnetotail passage of the Moon, along with low flux of alpha particles in the solar wind at the time of CHACE observations present a case when the He abundance in the Moon had hit one of its lowest values. CHACE, thus had the opportunity to explore the lunar exosphere in an extreme combination of the factors that control the lunar He abundance. Based on the observations and instrument sensitivity, an upper limit of ∼ 8.0 × 102 cm-3 for the surface density of lunar He-4 in the sunlit hemisphere is proposed. This result is expected to provide realistic constraints to the lunar He exosphere models under similar extreme conditions.

  5. On lunar exospheric column densities and solar wind access beyond the terminator from ROSAT soft X-ray observations of solar wind charge exchange

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T. E.; Farrell, W. M.; Fatemi, S.; Hills, H. Kent; Hodges, R. R.; Holmström, M.; Kuntz, K. D.; Porter, F. Scott; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P.; Walsh, B. M.

    2014-07-01

    We analyze the Röntgen satellite (ROSAT) position sensitive proportional counter soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges: two 19° wedges (one north and one south) 13-32° off the terminator toward the dark side and one wedge 38° wide centered on the antisolar direction. The radial profiles of both the north and the south wedges show significant limb brightening that is absent in the 38° wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears to be dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now, along with Mars, Venus, and Earth, the Moon represents another solar system body at which SWCX has been observed.

  6. On Lunar Exospheric Column Densities and Solar Wind Access Beyond the Terminator from ROSAT Soft X-ray Observations of Solar Wind Charge Exchange (SWCX)

    Science.gov (United States)

    Collier, M. R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T.; Farrell, W. M.; Fatemi, S.; Hills, H. K.; Hodges, R. R.; Holmstrom, M.; Kuntz, K. D.; Porter, F. S.; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P. M.

    2013-12-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the antisolar point. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears dominated by exospheric species arising from solar wind implantation, this technique can also monitor how the exosphere varies with solar wind conditions. Now along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed.

  7. Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading

    Directory of Open Access Journals (Sweden)

    Eojin Kim

    2011-03-01

    Full Text Available Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.

  8. Long-Term Periodicity of the Mars Exospheric Density from MRO and Mars Odyssey Radio Tracking Data

    Science.gov (United States)

    Genova, A.; Goossens, S. J.; Lemoine, F. G.; Mazarico, E.; Smith, D. E.; Zuber, M. T.

    2014-12-01

    The Mars Odyssey and Mars Reconnaissance Orbiter (MRO) missions have collected more than 11 years of continuous tracking data of spacecraft in orbit around Mars. The radio science data are generally used to determine the static and seasonal gravity field of the central body. However, these two spacecraft are in different sun-synchronous orbits that cover a wide range of altitudes (250-410 km) where investigation of the atmosphere and climate of Mars so far have not been supported by in situ and remote sensing measurements. The drag perturbation acting on the probes provides indirect measurements of the Martian atmospheric density. Therefore, we focused our work on the determination of the long-term periodicity of the atmospheric constituents in the Mars exosphere with Mars Odyssey and MRO radio tracking data. We implemented the Drag Temperature Model (DTM) -Mars model into our Precise Orbit Determination (POD) program GEODYN-II to adequately reproduce variations in temperature and (partial) density along ODY and MRO trajectories. The recovery of Mars' atmospheric dynamics using Doppler tracking data requires the accurate modeling of all forces acting on the spacecraft. The main non-conservative force, apart from drag, is solar radiation pressure. Spacecraft panel reflectivities and the radiation pressure-scaling factor are not estimated, but we adjusted empirical once-per-revolution along-track periodic accelerations (cosine and sine) over each orbital arc to mitigate solar radiation pressure mismodeling. After converging the orbital data arcs, and editing out all the data during superior conjunctions, we combined the MRO and Mars Odyssey arcs in a global solution where we estimated spacecraft initial states, time-correlated drag scale factors, and annual and semi-annual variability of the major constituents in the Mars upper atmosphere. We will show that the updated DTM-Mars model provides a better prediction of the long-term variability of the dominant species

  9. Migration calculations for water in the exosphere of the Moon: Dusk-dawn asymmetry, heterogeneous trapping, and D/H fractionation

    Science.gov (United States)

    Schorghofer, Norbert

    2014-07-01

    Water ice is trapped in permanently shadowed craters near the lunar poles, where it is thought to have arrived from an exogenic or endogenic source via ballistic hops. We use a model of the migration of water molecules in the lunar exosphere to investigate three problems: (1) A strong continuous source would lead to an enhanced concentration of H2O at the morning terminator but not at the evening terminator. Hence, spectral features observed at both terminators do not suggest that there is diurnal migration of volatiles. (2) Cold trapping after a comet impact leads to an unequal partitioning between the two hemispheres depending on the latitude of the impact but to nearly equal partitioning with respect to longitude. (3) The D/H fractionation as the water molecules migrate toward the poles is small. Hence, the isotopic composition of ice deposits in the cold traps can be related to that of the source.

  10. Simulated solar wind plasma interaction with the Martian exosphere: influence of the solar EUV flux on the bow shock and the magnetic pile-up boundary

    Directory of Open Access Journals (Sweden)

    R. Modolo

    2006-12-01

    Full Text Available The solar wind plasma interaction with the Martian exosphere is investigated by means of 3-D multi-species hybrid simulations. The influence of the solar EUV flux on the bow shock and the magnetic pile-up boundary is examined by comparing two simulations describing the two extreme states of the solar cycle. The hybrid formalism allows a kinetic description of each ions species and a fluid description of electrons. The ionization processes (photoionization, electron impact and charge exchange are included self-consistently in the model where the production rate is computed locally, separately for each ionization act and for each neutral species. The results of simulations are in a reasonable agreement with the observations made by Phobos 2 and Mars Global Surveyor spacecraft. The position of the bow shock and the magnetic pile-up boundary is weakly dependent of the solar EUV flux. The motional electric field creates strong asymmetries for the two plasma boundaries.

  11. The meteoroid stream of comet Encke at Mercury: Implications for MErcury Surface, Space ENvironment, GEochemistry, and Ranging observations of the exosphere

    Science.gov (United States)

    Christou, Apostolos A.; Killen, Rosemary M.; Burger, Matthew H.

    2015-09-01

    We test the hypothesis that an annually repeatable Ca emission excess in Mercury's exosphere at a True Anomaly Angle (TAA) of 25° ± 5° is due to particles from comet 2P/Encke impacting the surface. By simulating the dynamical evolution of Encke particles under planetary perturbations and Poynting-Robertson drag, we find that millimeter-sized grains ejected 1-2 ×104 years ago encounter Mercury at TAA = 350°-30°. The timing of the excess emission is consistent with a major dust release episode ≲20 kyr ago, possibly due to Encke progenitor breakup. The emission mechanism is likely the direct injection of impact-liberated Ca into sunlight rather than nightside surface adsorption for subsequent release at dawn. The timing of dust release from the comet depends on this mechanism; a 10 kyr age is implied by the direct-injection scenario.

  12. Sources of Sodium in the Lunar Exosphere: Modeling Using Ground-Based Observations of Sodium Emission and Spacecraft Data of the Plasma

    Science.gov (United States)

    Sarantos, Menelaos; Killen, Rosemary M.; Sharma, A. Surjalal; Slavin, James A.

    2009-01-01

    Observations of the equatorial lunar sodium emission are examined to quantify the effect of precipitating ions on source rates for the Moon's exospheric volatile species. Using a model of exospheric sodium transport under lunar gravity forces, the measured emission intensity is normalized to a constant lunar phase angle to minimize the effect of different viewing geometries. Daily averages of the solar Lyman alpha flux and ion flux are used as the input variables for photon-stimulated desorption (PSD) and ion sputtering, respectively, while impact vaporization due to the micrometeoritic influx is assumed constant. Additionally, a proxy term proportional to both the Lyman alpha and to the ion flux is introduced to assess the importance of ion-enhanced diffusion and/or chemical sputtering. The combination of particle transport and constrained regression models demonstrates that, assuming sputtering yields that are typical of protons incident on lunar soils, the primary effect of ion impact on the surface of the Moon is not direct sputtering but rather an enhancement of the PSD efficiency. It is inferred that the ion-induced effects must double the PSD efficiency for flux typical of the solar wind at 1 AU. The enhancement in relative efficiency of PSD due to the bombardment of the lunar surface by the plasma sheet ions during passages through the Earth's magnetotail is shown to be approximately two times higher than when it is due to solar wind ions. This leads to the conclusion that the priming of the surface is more efficiently carried out by the energetic plasma sheet ions.

  13. Theoretical predictions of source rates for exospheric CO 2 on icy satellites of the outer planets due to sublimation of deep subsurface CO 2 ice

    Science.gov (United States)

    Wood, Stephen E.

    2016-10-01

    The abundances of CO2 observed in the exospheres of Callisto and, more recently, Rhea and Dione are difficult to explain. The previously proposed sources for the CO2 either have production rates well below the expected rates of escape/destruction or should produce other species (e.g. CO) that are not observed.We consider a potential source that has not been previously investigated - CO2 vapor originating from crustal CO2 ice and driven upward by the endogenic heat flux - and have developed a model to make quantitative estimates of the corresponding global subsurface vapor flux.Our model is based on previous theoretical work by Clifford (1993) and Mellon et al. (1997) for equatorial ground ice on Mars, who showed that in times or places where subsurface pore ice is undergoing long-term sublimation and diffusive loss, the ice table (the shallowest depth where any pore ice exists) will not continue to recede indefinitely. Beyond a certain, predictable depth, the linear diffusive profile of vapor density between the ice table and the surface will become supersaturated with respect to the local temperature and recondense as pore ice. This is true for any planetary body with a non-negligible interior heat source (e.g. radiogenic, tidal, etc) and is due to the fact that, while the ice temperature increases ~linearly with depth, the corresponding equilibrium vapor density increases exponentially.Once this occurs, a steady-state profile of ice volume fraction, f_ice(z), develops, with net mass loss only occurring from the retreating pore-filling ice layer. The rate of vapor flux to the surface is then determined only by the vapor density and temperature gradient at the ice table depth. We use a 1-D thermal model coupled with an analytic physical model for regolith thermal conductivity (including its depth- and T-dependence), to calculate the zonally-integrated global CO2 vapor flux corresponding to the range of expected heat flow values. Our preliminary results show

  14. Corrigendum to "Observation of Neon at mid and high latitudes in the sunlit Lunar Exosphere: Results from CHACE aboard MIP/Chandrayaan-1", Vol. 272 (2016), pp 206-211, doi 10.1016/j.icarus.2016.02.030

    Science.gov (United States)

    Pratim Das, Tirtha; Thampi, Smitha V.; Bhardwaj, Anil; Ahmed, S. M.; Sridharan, R.

    2017-03-01

    Our paper titled "Observation of Neon at mid and high latitudes in the sunlit Lunar Exosphere: Results from CHACE aboard MIP/Chandrayaan-1" (Icarus 272 (2016) 206-211) presents the results of the observations on the distribution of neutral Neon in the mid and high lunar latitudes by the CHACE instrument aboard Moon Impact Probe (MIP) in Chandrayaan-1. The authors recently noticed two errors in the representation of the results in two figures, although there is no change in the reported number densities and the other interpretations of the results.

  15. Sodium Exosphere of Planet Mercury: Particle Tracing

    Science.gov (United States)

    Paral, J.; Travnicek, P.; Kabin, K.; Rankin, R.

    2007-12-01

    We will present the results of particle tracing simulations of heavy ions in magnetosphere of Mercury. In our study we use electric and magnetic fields from self-consistent hybrid simulations of Hermean environment. We consider three major release processes, namely photon stimulated description, solar wind sputtering, and micro-meteoroid vaporization to study distribution of energy and other characteristics in space and time. The released neutral atoms are ionized through photoionization processes after the sputtering. Part of our work will be focused on the possible measurements during three initial flybys of the MESSENGER spacecraft scheduled for 2008 and 2009.

  16. ROSAT Observations of Solar Wind Charge Exchange with the Lunar Exosphere

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Benna, M.; Carter, J. A.; Cravens, T. E.; Hills, H. Kent; Hodges, R. R.; Kuntz, K. D.; Porter, F. Scott; Read, A.; hide

    2012-01-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the anti-solar direction. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the count rate increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere. Along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed. This technique can be used to explore the solar wind-lunar interaction.

  17. On lunar exospheric column densities and solar wind access beyond the terminator from ROSAT soft X-ray observations of solar wind charge exchange

    Czech Academy of Sciences Publication Activity Database

    Collier, M. R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T. E.; Farrell, W.M.; Fatemi, S.; Hills, H. K.; Hodges, R. R.; Holmstrom, M.; Kuntz, K. D.; Porter, F. S.; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Trávníček, Pavel; Walsh, B. M.

    2014-01-01

    Roč. 119, č. 7 (2014), s. 1459-1478 ISSN 2169-9097 Institutional support: RVO:68378289 Keywords : HPC2N * Moon * PSPC * ROSAT * SWCX Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 3.440, year: 2013 http://onlinelibrary.wiley.com/doi/10.1002/2014JE004628/epdf

  18. 3-D Hybrid Kinetic Modeling of the Interaction Between the Solar Wind and Lunar-like Exospheric Pickup Ions in Case of Oblique/ Quasi-Parallel/Parallel Upstream Magnetic Field

    Science.gov (United States)

    Lipatov, A. S.; Farrell, W. M.; Cooper, J. F.; Sittler, E. C., Jr.; Hartle, R. E.

    2015-01-01

    The interactions between the solar wind and Moon-sized objects are determined by a set of the solar wind parameters and plasma environment of the space objects. The orientation of upstream magnetic field is one of the key factors which determines the formation and structure of bow shock wave/Mach cone or Alfven wing near the obstacle. The study of effects of the direction of the upstream magnetic field on lunar-like plasma environment is the main subject of our investigation in this paper. Photoionization, electron-impact ionization and charge exchange are included in our hybrid model. The computational model includes the self-consistent dynamics of the light (hydrogen (+), helium (+)) and heavy (sodium (+)) pickup ions. The lunar interior is considered as a weakly conducting body. Our previous 2013 lunar work, as reported in this journal, found formation of a triple structure of the Mach cone near the Moon in the case of perpendicular upstream magnetic field. Further advances in modeling now reveal the presence of strong wave activity in the upstream solar wind and plasma wake in the cases of quasiparallel and parallel upstream magnetic fields. However, little wave activity is found for the opposite case with a perpendicular upstream magnetic field. The modeling does not show a formation of the Mach cone in the case of theta(Sub B,U) approximately equal to 0 degrees.

  19. PVO VENUS ONMS BROWSE NEUTRAL DENSITY 12 SECOND V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set was designed to determine the composition of the neutral thermosphere/exosphere of Venus. The term composition includes both the type of neutral gases...

  20. Direct Observations of Lunar Pickup Ions in the Magnetosphere Tail-Lobes by ARTEMIS

    Science.gov (United States)

    Samad, R. L.; Poppe, A. R.; Halekas, J. S.; Delory, G. T.; Angelopoulos, V.; Farrell, W. M.

    2012-03-01

    We present ARTEMIS observations of pickup ions on the dayside of the Moon in the terrestrial magnetotail lobes. We attempt to determine the composition of these ions, presumably from either the surface or the exosphere, via ion tracing simulations.

  1. The geocoronal responses to the geomagnetic disturbances

    Science.gov (United States)

    Kuwabara, M.; Yoshioka, K.; Murakami, G.; Tsuchiya, F.; Kimura, T.; Yamazaki, A.; Yoshikawa, I.

    2017-01-01

    Atomic hydrogen atoms in the terrestrial exosphere resonantly scatter solar Lyman alpha (121.6 nm) radiation, observed as the hydrogen geocorona. Measurements of scattered solar photons allow us to probe time-varying distributions of exospheric hydrogen atoms. The Hisaki satellite with the extreme ultraviolet spectrometer (EXtreme ultraviolet spectrosCope for ExosphEric Dynamics: EXCEED) was launched in September 2013. EXCEED acquires spectral images (52-148 nm) of the atmospheres/magnetospheres of planets from Earth orbit. Due to its low orbital altitude ( 1000 km), the images taken by the instrument also contain the geocoronal emissions. In this context, EXCEED has provided quasi-continuous remote sensing observations of the geocorona with high temporal resolution ( 1 min) since 2013. These observations provide a unique database to determine the long-term behavior of the exospheric density structure. In this paper, we report exospheric structural responses observed by EXCEED to geomagnetic disturbances. Several geomagnetic storms with decreases of Dst index occurred in February 2014 and the Lyman alpha column brightness on the night side of the Earth increased abruptly and temporarily by approximately 10%. Hisaki reveal that the time lag between the peaks of the magnetic activity and the changes in the Lyman alpha column brightness is found to be about 2 to 6 h during storms. In order to interpret the observational results, we evaluate quantitatively the factors causing the increase. On the basis of these results, a coupling effect via charge exchange between the exosphere and plasmasphere causes variations of the exospheric density structure.

  2. What Will LADEE Tell Us About the Lunar Atmosphere?

    Science.gov (United States)

    Srantos, M.; Killen, R. M.; Glenar, D.; Benna, M.; Stubbs, T.

    2011-01-01

    The only species that have been confirmed in the lunar exosphere are Na, K, Ar, and He. However, models for the production and loss of lunar regolith-derived exospheric species from source processes including micrometeoroid impact vaporization, sputtering, and, for Na and K, photon-stimulated desorption, predict a host of other species should exist in the lunar exosphere. Assuming that loss processes are limited to ballistic escape, photoionization, and recycling to the surface, we have computed column abundances and compared them to published upper limits from the Moon and to detected abundances from Mercury. Our results suggest that available measurements often do not constrain models, and underline the need for improved spectroscopic measurements of the lunar exosphere. Such investigations are planned by the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft. Our calculations indicate that LADEE measurements promise to make definitive observations or set stringent upper limits for all regolith-driven exospheric species because of their favorable signal to noise ratio. Our models, along with LADEE observations, will constrain assumed model parameters for the Moon, such as sticking coefficients, source processes, and velocity distributions.

  3. Mercury's Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroid Space Weathering Studies

    Science.gov (United States)

    Dominque, Deborah L.; Chapman, Clark R.; Killen, Rosemary M.; Zurbuchen, Thomas H.; Gilbert, Jason A.; Sarantos, Menelaos; Benna, Mehdi; Slavin, James A.; Orlando, Thomas M.; Schriver, David; hide

    2011-01-01

    Understanding the composition of Mercury's crust is key to comprehending the formation of the planet. The regolith, derived from the crustal bedrock, has been altered via a set of space weathering processes. These processes are the same set of mechanisms that work to form Mercury's exosphere, and are moderated by the local space environment and the presence of an intrinsic planetary magnetic field. The alterations need to be understood in order to determine the initial crustal compositions. The complex interrelationships between Mercury's exospheric processes, the space environment, and surface composition are examined and reviewed. The processes are examined in the context of our understanding of these same processes on the lunar and asteroid regoliths. Keywords: Mercury (planet) Space weathering Surface processes Exosphere Surface composition Space environment 3

  4. Chemistry of impact events on Mercury

    Science.gov (United States)

    Berezhnoy, Alexey A.

    2018-01-01

    Based on the equilibrium thermochemical approach and quenching theory, formation of molecules and dust grains in impact-produced clouds formed after collisions between meteoroids and Mercury is considered. Based on observations of Al, Fe, and Mn atoms in the exosphere of Mercury and new results of studies of the elemental composition of the surface of Mercury, quenching temperatures and pressures of main chemical reactions and condensation of dust particles were estimated. The behavior of the main Na-, K-, Ca-, Fe-, Al-, Mn-, Mg-, Si-, Ti, Ni-, Cr-, Co, Zn-, O-, H-, S-, C-, Cl-, N-, and P-containing species delivered to the Hermean exosphere during meteoroid impacts was studied. The importance of meteoroid bombardment as a source of Na, K, Ca, Fe, Al, Mn, Mg, and O atoms in the exosphere of Mercury is discussed.

  5. Production of sodium vapor from exposed regolith in the inner solar system

    Science.gov (United States)

    Morgan, T. H.; Zook, H. A.; Potter, A. E.

    1989-01-01

    The likely supply of sodium to the lunar exosphere by impact vaporization, by charged particle sputtering, and by photon stimulated desorption has been calculated. These were each compared to the supply of sodium needed to maintain the observed sodium exosphere about the Moon. The two processes already known to act on the lunar regolith, impact vaporization and charged particle sputtering, appear to be sufficient to explain the observed column density of sodium in the lunar atmosphere. Photon-stimulated desorption, given the estimates for the yield of sodium due to this process available in the literature, would produce 100 to 1000 times more sodium than is observed. If impact vaporization is the main source of sodium to the atmosphere of Mercury, then sodium photo-ions in the exosphere of Mercury are efficiently recycled to the planet.

  6. Theoretical time variability of mobile water on the Moon and its geographic pattern

    Science.gov (United States)

    Schorghofer, Norbert; Lucey, Paul; Williams, Jean-Pierre

    2017-12-01

    A lunar water exosphere, if it currently exists, would lead to diurnal variations in surface water concentration. Here we present model calculations that reveal the specific geographic pattern of such diurnal variations as well as the amplitude of these variations relative to an assumed supply rate. Surface temperatures are derived from Diviner data and hence include topographic temperature heterogeneity. In the polar regions, diurnal variation can be one order of magnitude larger than at the equator and two hundred times larger than the monthly globally average water production density. Even so, the absolute size of any diurnal changes in surface concentration is likely too small to be measurable. An episodic source, that delivers the same mass over a sol (lunation) as a steady source, leads to comparable surface concentrations, but to a much denser exosphere with a half-life of a few Earth hours. Such a transient exosphere may already have been detected.

  7. The Gas-Surface Interaction of a Human-Occupied Spacecraft with a Near-Earth Object

    Science.gov (United States)

    Farrell, W. M.; Hurley, D. M.; Poston, M. J.; Zimmerman, M. I.; Orlando, T. M.; Hibbitts, C. A.; Killen, R. M.

    2016-01-01

    NASA's asteroid redirect mission (ARM) will feature an encounter of the human-occupied Orion spacecraft with a portion of a near- Earth asteroid (NEA) previously placed in orbit about the Moon by a capture spacecraft. Applying a shuttle analog, we suggest that the Orion spacecraft should have a dominant local water exosphere, and that molecules from this exosphere can adsorb onto the NEA. The amount of adsorbed water is a function of the defect content of the NEA surface, with retention of shuttle-like water levels on the asteroid at 10(exp 15) H2O's/m2 for space weathered regolith at T approximately 300 K.

  8. Investigation of the atmospheres of Europa, Ganymede, and Callisto with PEP/JUICE

    Science.gov (United States)

    Wurz, Peter; Tulej, Marek; Vorburger, Audrey; Thomas, Nicolas; Barabash, Stas; Wieser, Martin; Lammer, Helmut

    2013-04-01

    The Particle Environment Package (PEP) suite of instruments has been proposed for the JUICE mission, which contains sensors for the comprehensive measurements of electrons, ions and neutrals. One of the instruments for neutral particles is the Neutral and Ion Mass spectrometer instrument (NIM). NIM is a time-of-flight neutral gas and thermal ion mass spectrometer and is optimised for exospheric investigations. Full mass spectra (1 - 1000 amu, m/Δm = 1100) are recorded with high cadence, typically every 100 s, and during flybys even at 1 s cadence. In a 5-s spectrum the detection threshold is 10-16 mbar (about 1 cm-3). Various physical processes are acting on the surfaces of Jupiter's icy moons (Europa, Ganymede, Callisto) to promote material from the surface into the exosphere. These are thermal desorption (sublimation), photon stimulated desorption, ion-induced sputtering, and micro-meteorite impact vaporisation (Wurz and Lammer, 2003; Wurz et al., 2010). At Europa, sputtering is the most important surface release process (Johnson et al., 2009), which releases all species present on the surface more or less stoichiometrically into the exosphere, allowing to derive the chemical composition of the surface from the exospheric measurements. However, the chemical composition of the surface is modified by the bombardment of energetic electrons and ions, and the ultraviolet radiation. For example, species like H2, O2, H2O2 or O3 begin to be produced in the top surface layer and are later released into the exosphere by various means. Also, the co-rotation plasma's electrons and to a smaller extent the UV photons cause fragmentation and ionisation of molecules at some locations in these exospheres. We calculated the expected densities for established and expected species in Jupiter's icy moons exospheres. We find that for the planned JUICE trajectories near these moons that NIM will record most known species because of NIM's high sensitivity, even in the presence of the

  9. Early Results from the Lunar Atmosphere and Dust Environment Explorer (LADEE)

    Science.gov (United States)

    Elphic, Richard C.; Hine, Butler; Delory, Gregory T.; Mahaffy, Paul; Benna, Mehdi; Horanyi, Mihaly; Colaprete, Anthony; Noble, Sarah

    2014-05-01

    On 6 September, 2013, a near-perfect launch of the first Minotaur V rocket success-fully carried NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) into a high-eccentricity geocentric orbit. After 30 days of phasing, LADEE arrived at the Moon on 6 October, 2013. LADEE's science objectives are twofold: (1) Determine the composition of the lunar atmosphere, investigate processes controlling its distribution and variability, including sources, sinks, and surface interactions; (2) Characterize the lunar exospheric dust environment, measure its spatial and temporal variability, and effects on the lunar atmosphere, if any. After a successful commissioning phase, the three science instruments have made systematic observations of the lunar dust and exospheric environment. These include initial observations of argon, neon and helium exospheres, and their diurnal variations; the lunar micrometeoroid impact ejecta cloud and its variations; spatial and temporal variations of the sodium exosphere; and the search for sunlight extinction caused by dust. LADEE also made observations of the effects of the Chang'e 3 landing on 14 December 2013.

  10. Results from the Lunar Atmosphere and Dust Environment Explorer (LADEE)

    Science.gov (United States)

    Elphic, Richard; Stubbs, Timothy

    On 6 September, 2013, a near-perfect launch of the first Minotaur V rocket successfully carried NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) into a high-eccentricity geocentric orbit. After 30 days of phasing, LADEE arrived at the Moon on 6 October, 2013. LADEE’s science objectives are twofold: (1) Determine the composition of the lunar atmosphere, investigate processes controlling its distribution and variability, including sources, sinks, and surface interactions; (2) Characterize the lunar exospheric dust environment, measure its spatial and temporal variability, and effects on the lunar atmosphere, if any. After a successful commissioning phase, the three science instruments have made systematic observations of the lunar dust and exospheric environment. These include initial observations of argon, neon and helium exospheres, and their diurnal variations; the lunar micrometeoroid impact ejecta cloud and its variations; spatial and temporal variations of the sodium and potassium exospheres; and the search for sunlight extinction caused by dust. LADEE also made observations of the effects of the Chang’e 3 landing on 14 December 2013, and the Geminid meteor shower.

  11. Modeling of lunar pickup ion trajectories in the magnetosphere tail-lobes and comparisons with ARTEMIS observations

    Science.gov (United States)

    Samad, R.; Poppe, A.; Halekas, J. S.; Delory, G. T.; Angelopoulos, V.; Farrell, W. M.

    2012-12-01

    Due to its tenuous nature, direct measurements of the lunar surface-bounded exosphere (SBE) are difficult; however, measurement of ionized exospheric constituents as pickup ions represents an indirect method of observing the SBE. The ARTEMIS mission, currently in orbit around the Moon, has observed ions originating from the lunar exosphere in the terrestrial magnetosphere tail-lobes. These ions exhibit cycloidal motion perpendicular to the magnetic field lines, which is characteristic of pickup ions; however, they also frequently possess parallel velocities. The presence of both parallel and perpendicular velocities is attributed to the combination of the magnetotail convection electric field and the lunar near-surface photoelectron sheath field. Using an ion particle-tracing model, we will predict pickup ion density, energy, and pitch angle distributions under a variety of conditions in the terrestrial magnetotail lobes. Parameters studied in the model will include magnetotail lobe convection velocity, ion mass, photoelectron sheath strength, and the exospheric neutral distributions. Our goal is to constrain both the masses and source regions of the ions by comparing the model results to recent ARTEMIS observations.

  12. Maspex Europa

    Science.gov (United States)

    Waite, J. H., Jr.; Brockwell, T.; McGrath, M. A.; McKinnon, W. B.; Shock, E.; Bolton, S. J.; Wyrick, D. Y.; Teolis, B. D.; Sephton, M. A.; Mousis, O.; Zolotov, M. Y.; Lewis, W. S.

    2015-12-01

    MASPEX Europa is a space borne mass spectrometer that will use unprecedented sensitivity and mass resolution to measure and characterize the exosphere of Europa. This talk will demonstrate how MASPEX plans to use this information to study the composition of the surface, near surface, and interior ocean of Europa.

  13. Science from the Lunar Atmosphere and Dust Environment Explorer Mission

    Science.gov (United States)

    Elphic, Richard; Delory, Gregory; Noble, Sarah; Colaprete, Anthony; Horanyi, Mihaly; Mahaffy, Paul; Benna, Mehdi

    2014-11-01

    On September 6, 2013, a near-perfect launch of the first Minotaur V rocket successfully carried NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) into a high-eccentricity geocentric orbit. LADEE arrived at the Moon on October 6, 2013, during the government shutdown. The spacecraft impacted the lunar surface on April 18, 2014, following a completely successful mission. LADEE’s science objectives were twofold: (1) Determine the composition and variability of the lunar atmosphere; (2) Characterize the lunar exospheric dust environment, and its variability. The LADEE science payload consisted of the Lunar Dust Experiment (LDEX), which sensed dust impacts in situ, for particles between 100 nm and 5 micrometers; a neutral mass spectrometer (NMS), which sampled lunar exospheric gases in situ, over the 2-150 Dalton mass range; an ultraviolet/visible spectrometer (UVS) acquired spectra of atmospheric emissions and scattered light from tenuous dust, spanning a 250-800 nm wavelength range. UVS also performed dust extinction measurements via a separate solar viewer optic. Among the preliminary results for the lunar exosphere: (1) The helium exosphere of the Moon, first observed during Apollo, is clearly dominated by the delivery of solar wind He++. (2) Neon 20 is clearly seen as an important constituent of the exosphere. (3) Argon 40, also observed during Apollo and arising from interior outgassing, exhibits variations related to surface temperature-driven condensation and release, and is also enhanced over specific selenographic longitudes. (4) The sodium abundance varies with both lunar phase and with meteoroid influx, implicating both solar wind sputtering and impact vaporization processes. (5) Potassium was also routinely monitored and exhibits some of the same properties as sodium. (6) Other candidate species were seen by both NMS and UVS, and await confirmation. Dust measurements have revealed a persistent “shroud” of small dust particles between 0

  14. ARTEMIS Science Objectives

    Science.gov (United States)

    Sibeck, D. G.; Angelopoulos, V.; Brain, D. A.; Delory, G. T.; Eastwood, J. P.; Farrell, W. M.; Grimm, R. E.; Halekas, J. S.; Hasegawa, H.; Hellinger, P.; hide

    2011-01-01

    NASA's two spacecraft ARTEMIS mission will address both heliospheric and planetary research questions, first while in orbit about the Earth with the Moon and subsequently while in orbit about the Moon. Heliospheric topics include the structure of the Earth's magnetotail; reconnection, particle acceleration, and turbulence in the Earth's magnetosphere, at the bow shock, and in the solar wind; and the formation and structure of the lunar wake. Planetary topics include the lunar exosphere and its relationship to the composition of the lunar surface, the effects of electric fields on dust in the exosphere, internal structure of the Moon, and the lunar crustal magnetic field. This paper describes the expected contributions of ARTEMIS to these baseline scientific objectives.

  15. ARTEMIS observations of lunar pick-up ions in the terrestrial magnetotail lobes

    Science.gov (United States)

    Poppe, A. R.; Samad, R.; Halekas, J. S.; Sarantos, M.; Delory, G. T.; Farrell, W. M.; Angelopoulos, V.; McFadden, J. P.

    2012-09-01

    We report observations by the twin-probe mission ARTEMIS of pick-up ions of lunar origin obtained during times when the Moon was within the terrestrial magnetotail lobes. These ions were detected as two separate focused beams above the dayside lunar surface. Analysis of these beams has shown that they possess both field-aligned and field-perpendicular velocities, implying the presence of electric fields both parallel and perpendicular to the magnetotail lobe magnetic field. We suggest that the sources of these two electric fields are (a) the near-surface electric field due to the lunar photoelectron sheath and (b) the electric field generated by the magnetotail lobe convection velocity. We use the energy and pitch angle spectra to constrain the source locations and compositions of these ions, and conclude that exospheric ionization of the neutral exosphere is the dominant lunar pick-up ion production mechanism in the tail lobes.

  16. Theory, measurements, and models of the upper atmosphere and ionosphere of Saturn

    Science.gov (United States)

    Atreya, S. K.; Donahue, T. M.; Nagy, A. F.; Waite, J. H., Jr.; Mcconnell, J. C.

    1984-01-01

    The structure and composition of the thermosphere, exosphere, and ionosphere of saturn have been determined from observations at optical and radio wavelengths mainly by instruments aboard Voyager spacecraft. Techniques for determining the vertical profiles of temperature and density and the atmospheric vertical mixing in the upper Saturn atmosphere are discussed. Radio occultation measurements and theoretical models of Saturn's ionosphere are reviewed, and attempts to interpret the measurements using the models are discussed. Finally, mechanisms of thermospheric heating are examined.

  17. The Prospect of Responsive Spacecraft Using Aeroassisted, Trans-Atmospheric Maneuvers

    Science.gov (United States)

    2014-06-19

    composition – in the upper atmosphere has been demonstrated to deteriorate the ozone layer and chemically contaminate the water cycle.179 Not...at least a mono- layer ” of atomic oxygen on its surface either by mechanisms of chemisorption or physisorption. With this layer present on the TAV... layer of atomic oxygen and enters the exosphere, atmospheric species predominance shifts from oxygen to helium, and then to hydrogen. King-Hele explains

  18. The influence of surface roughness on volatile transport on the Moon

    Science.gov (United States)

    Prem, P.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.

    2018-01-01

    The Moon and other virtually airless bodies provide distinctive environments for the transport and sequestration of water and other volatiles delivered to their surfaces by various sources. In this work, we conduct Monte Carlo simulations of water vapor transport on the Moon to investigate the role of small-scale roughness (unresolved by orbital measurements) in the migration and cold-trapping of volatiles. Observations indicate that surface roughness, combined with the insulating nature of lunar regolith and the absence of significant exospheric heat flow, can cause large variations in temperature over very small scales. Surface temperature has a strong influence on the residence time of migrating water molecules on the lunar surface, which in turn affects the rate and magnitude of volatile transport to permanently shadowed craters (cold traps) near the lunar poles, as well as exospheric structure and the susceptibility of migrating molecules to photodestruction. Here, we develop a stochastic rough surface temperature model suitable for simulations of volatile transport on a global scale, and compare the results of Monte Carlo simulations of volatile transport with and without the surface roughness model. We find that including small-scale temperature variations and shadowing leads to a slight increase in cold-trapping at the lunar poles, accompanied by a slight decrease in photodestruction. Exospheric structure is altered only slightly, primarily at the dawn terminator. We also examine the sensitivity of our results to the temperature of small-scale shadows, and the energetics of water molecule desorption from the lunar regolith - two factors that remain to be definitively constrained by other methods - and find that both these factors affect the rate at which cold trap capture and photodissociation occur, as well as exospheric density and longevity.

  19. Kinetic and Potential Sputtering of Lunar Regolith: The Contribution of the Heavy Highly Charged (Minority) Solar Wind Ions

    Science.gov (United States)

    Meyer, F. W.; Barghouty, A. F.

    2012-01-01

    Solar wind sputtering of the lunar surface helps determine the composition of the lunar exosphere and contributes to surface weathering. To date, only the effects of the two dominant solar wind constituents, H+ and He+, have been considered. The heavier, less abundant solar wind constituents have much larger sputtering yields because they have greater mass (kinetic sputtering) and they are highly charged (potential sputtering) Their contribution to total sputtering can therefore be orders of magnitude larger than their relative abundances would suggest

  20. Thermosphere-Ionosphere-Mesosphere Modeling Using the TIME-GCM

    Science.gov (United States)

    2014-09-30

    nitric oxide observations from the UARS Halogen Occultation Experiment indicate that the observed diurnal variations in mesospheric nitric oxide... Science Across the Stratopause,” Geophysical Monograph, 123, American Geophysical Union, 83-100, 2000. Roble, R. G., On the feasibility of developing a...global atmospheric model extending from the ground to the exosphere, “Atmospheric Science Across the Stratopause,” Geophysical Monograph, 123

  1. SERENA: A Neutral Atoms Detector to be proposed for the ESA's BepiColombo Planetary Orbiter

    Science.gov (United States)

    di Lellis, A.; Orsini, S.; Livi, S.; Wurz, P.; Milillo, A.; Barabash, S.

    2003-04-01

    A comprehensive suite for the neutral particles detection in the Mercury environment is under development and it will be proposed in the frame of the ESA cornerstone’s BepiColombo mission. The package, namely NPA - SERENA (Neutral Particle Analyser - Searching for Exospheric Refilling and Emitted Neutral Abundances), consists of three dedicated spectrometers (MAIA, ELENA, and M/H-ENA) identifying and measuring the particles and their energies, namely from fraction of eV to tens of keV. The proposed sensors will observe and analyse the bulk of the sub-thermal / thermal exospheric (0-50 eV) gas along the ram direction (MAIA), the sputtering emission (E min 1 keV) within 1-D (2 deg x 60 deg) nadir cross track slices from the planet surface (ELENA), and the charge exchange between ions and exospheric gas (E min 30 keV) in order to monitor the Mercury’s magnetosphere dynamics (M/H-ENA). The paper describes the progress achieved in the system and sensor level design and provides a summary report on the laboratory test of the investigated techniques and of the expected performances of the ELENA detector head.

  2. New Applications for the Jacchia 77 Model

    Science.gov (United States)

    Wise, J. O.; Burke, W. J.

    2008-12-01

    We examine the Jacchia 77 model and compare model densities to the 2001-2005 densities derived from the CHAMP and GRACE accelerometer data. Of particular interest is the model's unique formulation of exospheric temperature directly from the solar flux (F10) as opposed to a nighttime minimum temperature in the earlier Jacchia 70 and Jacchia 71 models. We compare this calculation directly to average global exospheric temperatures derived from the CHAMP and GRACE accelerometer neutral density data using the hydrostatic equation. The average global exospheric temperature is important because the model density profiles are all derived from this quantity. The Jacchia 77 model includes a special 81-day weight averaged F10 as a model proxy. This approach uses the F10 from the last three solar rotations instead of a centered F81 index, which means the model can be used in real time by using an 81-day weighted "boxcar" index. With new solar proxies for EUV and Mg recently introduced, we discuss the possibility of incorporating these indices in a similar manner. Because the drivers of thermospheric density-- the semiannual variation, solar EUV and solar wind are treated as separate modules in the model-- we examine the strengths and weaknesses of each one as consideration for future model upgrades.

  3. ARTEMIS Observations of Pickup Ions Around the Moon

    Science.gov (United States)

    Halekas, J. S.; Delory, G. T.; Poppe, A.; Farrell, W. M.; Sarantos, M.

    2012-12-01

    ARTEMIS regularly observes pickup ions produced from the lunar surface and/or exosphere. The ARTEMIS orbit provides a unique view of pickup ions in their first gyration, where they form a narrow plume (or plumes) in the plane perpendicular to the magnetic field. Though ARTEMIS has no mass composition sensor, we can still derive constraints on the species of the observed ions, by comparing the location and velocity of the ions to the ideal cycloidal trajectories expected given the measured plasma velocity and magnetic field. Previously, we have derived constraints on pickup ion composition using only the phase space location of the peak flux. Now, we present a new method utilizing the entire energy-angle distribution of pickup ions to derive constraints on composition and source characteristics. ARTEMIS observations allow us to connect space observations to the surface and the largely surface-derived exosphere, providing a new constraint on the interaction of the lunar surface with the space environment. ARTEMIS also measures the solar wind drivers, allowing us to connect inputs and outputs. Once LADEE launches, ARTEMIS and LADEE together hold great promise for measuring the entire coupled plasma/exosphere system around the Moon.

  4. Elemental Mercury Diffusion Processes and Concentration at the Lunar Poles

    Science.gov (United States)

    Moxley, Frederick; Killen, Rosemary M.; Hurley, Dana M.

    2011-01-01

    In 2009, the Lyman Alpha Mapping Project (LAMP) spectrograph onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft made the first detection of element mercury (Hg) vapor in the lunar exosphere after the Lunar Crater Observing and Sensing Satellite (LCROSS) Centaur rocket impacted into the Cabeus crater in the southern polar region of the Moon. The lunar regolith core samples from the Apollo missions determined that Hg had a devolatilized pattern with a concentration gradient increasing with depth, in addition to a layered pattern suggesting multiple episodes of burial and volatile loss. Hg migration on the lunar surface resulted in cold trapping at the poles. We have modeled the rate at which indigenous Hg is lost from the regolith through diffusion out of lunar grains. We secondly modeled the migration of Hg vapor in the exosphere and estimated the rate of cold-trapping at the poles using a Monte Carlo technique. The Hg vapor may be lost from the exosphere via ionization, Jeans escape, or re-impact into the surface causing reabsorption.

  5. Sputtering of sodium and potassium from nepheline: Secondary ion yields and velocity spectra

    Science.gov (United States)

    Martinez, R.; Langlinay, Th.; Ponciano, C. R.; da Silveira, E. F.; Palumbo, M. E.; Strazzulla, G.; Brucato, J. R.; Hijazi, H.; Agnihotri, A. N.; Boduch, P.; Cassimi, A.; Domaracka, A.; Ropars, F.; Rothard, H.

    2017-09-01

    Silicates are the dominant surface material of many Solar System objects, which are exposed to ion bombardment by solar wind ions and cosmic rays. Induced physico-chemical processes include sputtering which can contribute to the formation of an exosphere. We have measured sputtering yields and velocity spectra of secondary ions ejected from nepheline, an aluminosilicate thought to be a good analogue for Mercury's surface, as a laboratory approach to understand the evolution of silicate surfaces and the presence of Na and K vapor in the exosphere. Experiments were performed with highly charged ion beams (keV/u-MeV/u) delivered by GANIL using an imaging XY-TOF-SIMS device under UHV conditions. The fluence dependence of sputtering yields gives information about the evolution of surface stoichiometry during irradiation. From the energy distributions N(E) of sputtered particles, the fraction of particles which could escape from the gravitational field of Mercury, and of those falling back and possibly contributing to populate the exosphere can be roughly estimated.

  6. Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones.

    Science.gov (United States)

    Lammer, Helmut; Lichtenegger, Herbert I M; Kulikov, Yuri N; Griessmeier, Jean-Mathias; Terada, N; Erkaev, Nikolai V; Biernat, Helfried K; Khodachenko, Maxim L; Ribas, Ignasi; Penz, Thomas; Selsis, Franck

    2007-02-01

    Atmospheric erosion of CO2-rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for simulating the thermospheric heating by photodissociation and ionization processes due to exothermic chemical reactions and cooling by the CO2 infrared radiation in the 15 microm band. Our study shows that intense XUV radiation of active M stars results in atmospheric expansion and extended exospheres. Using thermospheric neutral and ion densities calculated for various XUV fluxes, we applied a numerical test particle model for simulation of atmospheric ion pick up loss from an extended exosphere arising from its interaction with expected minimum and maximum CME plasma flows. Our results indicate that the Earth-like exoplanets that have no, or weak, magnetic moments may lose tens to hundreds of bars of atmospheric pressure, or even their whole atmospheres due to the CME-induced O ion pick up at orbital distances exoplanet is protected by a "magnetic shield" with its boundary located at 1 Earth radius above the surface. Furthermore, our study indicates that magnetic moments of tidally locked Earth-like exoplanets are essential for protecting their expanded upper atmospheres because of intense XUV radiation against CME plasma erosion. Therefore, we suggest that larger and more massive terrestrial-type exoplanets may better protect their atmospheres against CMEs, because the larger cores of such exoplanets would generate stronger magnetic moments and their higher gravitational acceleration would constrain the expansion of their thermosphere-exosphere regions and reduce atmospheric escape.

  7. Collecting the Puzzle Pieces: Completing HST's UV+NIR Survey of the TRAPPIST-1 System ahead of JWST

    Science.gov (United States)

    de Wit, Julien

    2017-08-01

    Using the Spitzer Space Telescope, our team has discovered 7 Earth-sized planets around the nearby Ultra-cool dwarf star TRAPPIST-1. These planets are the first to be simultaneously Earth-sized, temperate, and amenable for in-depth atmospheric studies with space-based observatories (notably, JWST). TRAPPIST-1's system thus provides us with the first opportunity to probe the atmospheres of Earth-sized exoplanets and search for signs of habitability beyond our solar system, which will require spectral information from the UV to the IR to complete their atmospheric puzzles.We request 114 HST orbits to complete the UV+NIR survey of the 7 planets in preparation for their in-depth followup with JWST. The suggested low-density of the planets combined with their complex orbital resonance chain indicate that they migrated inward to their current positions and may harbor large water rich reservoir or leftover primordial H2 atmospheres. We have already ruled out the presence of clear H2 atmospheres for the 5 innermost planets using WFC3 and are requesting 16 WFC3 orbits to complete the TRAPPIST-1 NIR reconnaissance survey. Our primary request consists in 98 STIS orbits to complete the survey for extended H-exospheres around each of the planets. H-exospheres are the most accessible observables for volatile reservoirs, which have not been ruled out by our WFC3 observations. Exosphere detection is only amenable using HST unique capabilities in the UV and are pivotal to guide JWST's in-depth followup. The combined information from HST's UV and NIR observations will allow us put the first critical pieces of the atmospheric puzzle in place for these temperate earth-sized worlds.

  8. Oxygen isotopes in the Martian atmosphere - Implications for the evolution of volatiles

    Science.gov (United States)

    Mcelroy, M. B.; Yung, Y. L.

    1976-01-01

    Nonthermal escape of oxygen by recombination of exospheric O2(+) combined with diffusive separation of gases at lower altitude provides a mechanism through which the Martian atmosphere may be enriched in O-18 relative to O-16. Measurement of the abundance of O-18 relative to O-16 together with a determination of the turbopause may be used to develop important constraints on the history of Martian volatiles. Models for the interpretation of these data are developed and discussed in light of present information.

  9. On Mars' atmospheric sputtering after MAVEN first two years

    Science.gov (United States)

    Leblanc, F.; Modolo, R.; Curry, S.; Luhmann, J. G.; Lillis, R.; Chaufray, J. Y.; Hara, T.; McFadden, J.; Halekas, J.; Eparvier, F.; Larson, D.; Connerney, J.; Jakosky, B.

    2017-09-01

    Mars may have lost a significant part of its atmosphere into space along its history, in particular since the end of its internal dynamo, 4.1 Gyr ago. The sputtering of the atmosphere by precipitating planetary picked up ions accelerated by the solar wind is one of the processes that could have significantly contributed to this atmospheric escape. We here present a two years base analysis of MAVEN observation of the precipitating flux, in particular the dependency of the precipitating intensity with solar zenith angle and used this measurement to model the expected escape rate and exosphere induced by this precipitation.

  10. Joint Europa Mission (JEM). A Multiscale Study of Europa to Characterize its Habitability and Search for Extant Life

    Science.gov (United States)

    Blanc, M.; Prieto-Ballesteros, O.; André, N.; Gomez-Elvira, J.; T. JEM Team

    2017-09-01

    We propose that ESA works with NASA, which presently leads the way towards in situ exploration of Europa, to design and fly jointly an ambitious and exciting planetary mission to characterize biosignatures in the environment of Europa (surface, subsurface and exosphere), while we also want to address a more general question: how does life develop in a specific habitable environment, and what are the evolutional properties of a habitable planet or satellite and of its host planetary/satellite system which make the development of life possible. The Joint Europa Mission was proposed to ESA's Cosmic Vision call for M5 missions in October 2016.

  11. Dynamic Planet Mercury in the Context of Its Environment

    CERN Document Server

    Clark, Pamela Elizabeth

    2007-01-01

    We are in a time of transition in our understanding of Mercury. Of particular interest here is the emerging picture of the planet as a system, with interactions between interior, surface, exosphere, and magnetosphere that have influenced and constrained the evolution of each part of the system. Previous books have emphasized the results of Mariner 10 and current ground-based measurements, with very little discussion of the nature and influence of the magnetosphere. This book will present the planet in the context of its surroundings, thus providing a foundation for the next major influx of information from Mercury and contributing to the planning for future missions.

  12. On magnetospheric electron impact ionisation and dynamics in Titan's ram-side and polar ionosphere – a Cassini case study

    Directory of Open Access Journals (Sweden)

    K. Agren

    2007-11-01

    Full Text Available We present data from the sixth Cassini flyby of Titan (T5, showing that the magnetosphere of Saturn strongly interacts with the moon's ionosphere and exo-ionosphere. A simple electron ionisation model provides a reasonable agreement with the altitude structure of the ionosphere. Furthermore, we suggest that the dense and cold exo-ionosphere (from the exobase at 1430 km and outward to several Titan radii from the surface can be explained by magnetospheric forcing and other transport processes whereas exospheric ionisation by impacting low energy electrons seems to play a minor role.

  13. Marshall Engineering Thermosphere Model, Version MET-2007

    Science.gov (United States)

    Suggs, R. J.; Suggs, R. M.

    2017-01-01

    The region of the Earth's atmosphere between about 90 and 500 km altitude is known as the thermosphere, while the region above about 500 km is known as the exosphere. For space vehicle operations, the neutral atmosphere in these regions is significant. Even at its low density, it produces torques and drags on vehicles and affects orbital lifetimes. The thermosphere density above 100 km altitude also modulates the flux of trapped radiation and orbital debris. Atomic oxygen at orbital altitudes is important because it can erode and chemically change exposed vehicle surfaces.

  14. MESSENGER Observations of the Spatial Distribution of Planetary Ions Near Mercury

    Science.gov (United States)

    Zurbuchen, Thomas H.; Raines, Jim M.; Slavin, James A.; Gershman, Daniel J.; Gilbert, Jason A.; Gloeckler, George; Anderson, Brian J.; Baker, Daniel N.; Korth, Haje; Krimigis, Stamatios M.; hide

    2011-01-01

    Global measurements by MESSENGER of the fluxes of heavy ions at Mercury, particularly sodium (Na(+)) and oxygen (O(+)), exhibit distinct maxima in the northern magnetic-cusp region, indicating that polar regions are important sources of Mercury's ionized exosphere, presumably through solar-wind sputtering near the poles. The observed fluxes of helium (He(+)) are more evenly distributed, indicating a more uniform source such as that expected from evaporation from a helium-saturated surface. In some regions near Mercury, especially the nightside equatorial region, the Na(+) pressure can be a substantial fraction of the proton pressure.

  15. Isotopic composition of nitrogen - Implications for the past history of Mars' atmosphere

    Science.gov (United States)

    Mcelroy, M. B.; Yung, Y. L.; Nier, A. O.

    1976-01-01

    Models are presented for the past history of nitrogen on Mars, based on Viking measurements showing that the atmosphere is enriched in N-15. The enrichment is attributed to selective escape, with fast atoms formed in the exosphere by electron impact dissociation of N2 and by dissociative recombination of N2(+). The initial partial pressure of N2 should have been at least as large as several millibars and could have been as large as 30 millibars if surface processes were to represent an important sink for atmospheric HNO2 and HNO3.

  16. Positive and negative ion outflow at Rhea as observed by Cassini

    Science.gov (United States)

    Desai, Ravindra; Jones, Geraint; Regoli, Leonardo; Cowee, Misa; Coates, Andrew; Kataria, Dhiren

    2017-04-01

    Rhea is Saturn's largest icy moon and hosts an ethereal oxygen and carbon-dioxide atmosphere as was detected when Cassini observed positive and negative pickup ions outflowing from the moon and an extended neutral exosphere. These pickup ions can form current systems which, with the resulting jxB force, act to slow-down the incident magneto-plasma and cause field-line draping. As well as impacting the plasma interaction, the composition and density of picked up ions provide key diagnostics of the moon's sputter-induced atmosphere and surface. During the first Cassini-Rhea encounter (R1), the Cassini Plasma Spectrometer (CAPS) observed positively and negatively charged pickup ions before and after passing through the moon's plasma wake respectively, in agreement with their anticipated cycloidal trajectories. On the subsequent more distant wake encounter (R1.5) however, only positively charged pickup ions were observed, indicating high loss rates of the negative ions in Saturn's magnetosphere. Here, using an updated model of Cassini's Electron Spectrometer response function, we are able to estimate the outward flux of negatively charged pickup ions, the first time such a plasma population has been constrained. Using test-particle simulations we trace both the positive and negative particles back to Rhea's exobase to better understand their production and loss processes and the implications for Rhea's sputter-induced exosphere. We also look to examine whether the calculated ion densities could generate ion cyclotron wave activity.

  17. Soft X-ray and ENA imaging of the Earth's dayside magnetosphere : OpenGGCM modeling results

    Science.gov (United States)

    Connor, H. K.; Sibeck, D. G.; Collier, M. R.; Kuntz, K. D.; Raeder, J.

    2014-12-01

    Charged ions and neutral atoms exchange electrons in many space plasma venues. Soft X-rays are emitted when highly charged solar wind ions, such as C6+, O7+, and Fe13+, interact with Hydrogen and Helium atoms. Energetic Neutral Atoms (ENAs) are produced when solar wind protons encounter neutral atoms. Consequently ENA and soft x-ray images can be a powerful technique to probe remotely the plasma and neutral density structures created when the solar wind interacts with planetary exospheres, such as those at the Earth, Moon, Mars, Venus, and comets. Here, we use the OpenGGCM global magnetosphere-ionosphere MHD model and the Hodges model for the Earth's exosphere to simulate both soft X-ray and ENA images of Earth's dayside cusps and magnetosheath in preparation for future mission planning. We consider several solar wind and IMF scenarios, such as a sudden increase in the solar wind dynamic pressure and southward IMF turning. We then predict the time-dependent variations in X-Ray and ENA images that would be observed by spacecraft far outside the magnetosphere. As expected, strong signals appear near to and define the positions of the bow shock, magnetopause, and cusps. The soft X-ray imager observes changes in the dayside system nearly instantaneously, while the ENA imager measures the changes later due to the finite travel time of ENAs from the dayside systems to the spacecraft location.

  18. The Venus flybys opportunity with BEPICOLOMBO

    Science.gov (United States)

    Mangano, Valeria; de la Fuente, Sara; Montagnon, Elsa; Benkhoff, Johannes; Zender, Joe; Orsini, Stefano

    2017-04-01

    BepiColombo is a dual spacecraft mission to Mercury to be launched in October 2018 and carried out jointly between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). The Mercury Planetary Orbiter (MPO) payload comprises eleven experiments and instrument suites. It will focus on a global characterization of Mercury through the investigation of its interior, surface, exosphere and magnetosphere. In addition, it will test Einstein's theory of general relativity. The second spacecraft, the Mercury Magnetosphere Orbiter (MMO), will carry five experiments or instrument suites to study the environment around the planet including the planet's exosphere and magnetosphere, and their interaction processes with the solar wind. The composite spacecraft made of MPO, MMO, a transfer module (MTM) and a sunshield (MOSIF) will be launched on an escape trajectory that will bring it into heliocentric orbit on its way to Mercury. During the cruise of 7.2 years toward the inner part of the Solar System, BepiColombo will make 1 flyby to the Earth, 2 to Venus, and 6 to Mercury. Only part of its payload will be obstructed by the sunshield and the cruise spacecraft configuration, so that the two flybys to Venus will allow operations of many instruments, like: spectrometers at many wavelengths, accelerometer, radiometer, ion and electron detectors. A scientific working group has recently formed from the BepiColombo community to identify potentially interesting scientific cases and to analyse operation timelines. Preliminary outputs will be presented and discussed.

  19. 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

  20. Atmospheric Bulges on Tidally-Locked Satellites

    Science.gov (United States)

    Oza, Apurva V.; Johnson, Robert E.; Leblanc, Francois

    2017-10-01

    We use a simple analytic model to examine the spatial distribution of a volatile species in a surface-bounded atmosphere on a rotating object that is tidally-locked to its parent body. Spatial asymmetries in such atmospheres have recently been observed via ultraviolet auroral emissions from the exospheres of the icy satellites Europa and Ganymede. The Hubble Space Telescope observations indicate that these satellites host unique, surface-bounded O2 exospheres which bulge towards dusk. Using a simple 1-D mass conservation balance we examine the nature of the volatile source, the surface temperature profile, the spatial morphology of the loss process, and the adsorption and desorption properties of the surfaces to understand the spatial distribution of the surface-bounded atmosphere for a number of objects. Since the ballistic hop distances are much smaller than the satellite radii, we show that the observed asymmetries at Europa and Ganymede can be simply due to a strongly thermally-dependent source, although asymmetries in the plasma-induced loss could contribute. A key condition for these atmospheric bulges that are shifted towards dusk is the relationship between the rotation rate and the atmospheric loss rate.

  1. Short-term variations of Mercury's cusps Na emission

    Science.gov (United States)

    Massetti, S.; Mangano, V.; Milillo, A.; Mura, A.; Orsini, S.; Plainaki, C.

    2017-09-01

    We illustrate the analysis of short-term ground-based observations of the exospheric Na emission (D1 and D2 lines) from Mercury, which was characterized by two high-latitude peaks confined near the magnetospheric cusp footprints. During a series of scheduled observations from THEMIS solar telescope, achieved by scanning the whole planet, we implemented a series of extra measurements by recording the Na emission from a narrow north-south strip only, centered above the two emission peaks. Our aim was to inspect the existence of short-term variations, which were never analyzed before from ground-based observations, and their possible correlation with interplanetary magnetic field variations. Though Mercury possesses a miniature magnetosphere, characterized by fast reconnection events that develop on a timescale of few minutes, ground-based observations show that the exospheric Na emission pattern can be globally stable for a prolonged period (some days) and can exhibits fluctuations in the time range of tens of minutes.

  2. Solar-Storm/Lunar Atmosphere Model (SSLAM): An Overview of the Effort and Description of the Driving Storm Environment

    Science.gov (United States)

    Farrell, W. M.; Halekas, J. S.; Killen, R. M.; Delroy, G. T.; Gross, N.; Bleacher, V; Krauss-Varben, D.; Hurley, D; Zimmerman, M. I.

    2012-01-01

    On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact on bodies located at 1 AU. The terrestrial magnetosphere did indeed become more electrically active during the storm passage but an obvious question is the effect of such a storm on an exposed rocky body like our Moon. The solar-storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver - the solar storm and CME passage occurring from 1-4 May 1998. We present herein an expanded discussion on the solar driver during the 1-4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had> 10 times the solar wind density and had a compositional component of He++ that exceeded 20%. We also provide a very brief overview oflhe SSLAM system layout and overarching results. One primary result is that the CME driver plasma can greatly increase the exospheric content via sputtering, with total mass loss rates that approach 1 kg/s during the 2-day CME passage. By analogy, we suggest that CME-related sputtering increases might also be expected during a CME passage by a near-earth asteroid or at the Mars exobase, resulting in an enhanced loss of material.

  3. Environments in the Outer Solar System

    Science.gov (United States)

    Krupp, N.; Khurana, K. K.; Iess, L.; Lainey, V.; Cassidy, T. A.; Burger, M.; Sotin, C.; Neubauer, F.

    2010-06-01

    The outer planets of our solar system Jupiter, Saturn, Uranus, and Neptune are fascinating objects on their own. Their intrinsic magnetic fields form magnetic environments (so called magnetospheres) in which charged and neutral particles and dust are produced, lost or being transported through the system. These magnetic environments of the gas giants can be envisaged as huge plasma laboratories in space in which electromagnetic waves, current systems, particle transport mechanisms, acceleration processes and other phenomena act and interact with the large number of moons in orbit around those massive planets. In general it is necessary to describe and study the global environments (magnetospheres) of the gas giants, its global configuration with its large-scale transport processes; and, in combination, to study the local environments of the moons as well, e.g. the interaction processes between the magnetospheric plasma and the exosphere/atmosphere/magnetosphere of the moon acting on time scales of seconds to days. These local exchange processes include also the gravity, shape, rotation, astrometric observations and orbital parameters of the icy moons in those huge systems. It is the purpose of this chapter of the book to describe the variety of the magnetic environments of the outer planets in a broad overview, globally and locally, and to show that those exchange processes can dramatically influence the surfaces and exospheres/atmospheres of the moons and they can also be used as a tool to study the overall physics of systems as a whole.

  4. Detection of Mercury's Potassium Tail

    Science.gov (United States)

    Schmidt, Carl; Leblanc, Francois; Moore, Luke; Bida, Thomas A.

    2017-10-01

    Ground-based observations of Mercury's exosphere bridge the gap between the MESSENGER and BepiColombo missions and provide a broad counterpart to their in situ measurements. Here we report the first detection of Mercury's potassium tail in both emission lines of the D doublet. The sodium to potassium abundance ratio at 5 planetary radii down-tail is approximately 95, near the mid-point of a wide range of values that have been quoted over the planet's disk. This is several times the Na/K present in atmospheres of the Galilean satellites and more than an order of magnitude above Mercury's usual analogue, the Moon. The observations confirm that Mercury's anomalously high Na/K ratios cannot be explained by differences in neutral loss rates. The width and structure of the Na and K tails is comparable and both exhibit a persistent enhancement in their northern lobe. We interpret this as a signature of Mercury's offset magnetosphere; the exosphere's source rates are locally enhanced at the southern surface, and sloshing from radiation pressure and gravity guides this population into the northern region of the tail.

  5. Redistribution of Lunar Polar Water to Mid-latitudes and its Role in Forming an OH veneer - Revisited

    Science.gov (United States)

    Farrell, W. M.; Killen, R. M.; Hurley, D. M.; Hodges, R. R.; Halekas, J. S.; Delory, G. T.

    2012-01-01

    We suggest that energization processes like ion sputtering and impact vaporization can eject/release polar water molecules residing within lunar cold trapped regions with sufficient velocity to allow their redistribution to mid-latitudes. We consider the possibility that these polar-ejected molecules can be an additional (but not dominant) contribution to the water/OH veneer observed as a 3 micron absorption feature at mid-latitudes by Chandrayaan-I, Cassini, and EPOXI. Taking the conservative case that polar water is ejected only from the floor of polar craters with an 0.1 % icy regolith then overall source rates are near 10(exp 18) H20s/s. This outflow amounts to approx 10(exp -7) kg/s of water to be ejected from each pole and is a water source rate that is 10(exp .5 lower than the overall exospheric source rate for all species. Hence, the out-flowing polar water is a perturbation in the overall exosphere composition & dynamics. This polar water 'fountain' model may not fully account for the relatively high concentrations in the mid-latitude water veneer observed in the IR (approx 10-1000 ppm). However, it may account for some part of the veneer. We note that the polar water fountain source rates scale linearly with ice concentration, and larger mass fractions of polar crater water should provide correspondingly larger fractions of water emission out of the poles which then 'spills' on to mid-latitude surfaces.

  6. ARTEMIS observations of lunar pick-up ions in the terrestrial magnetotail

    Science.gov (United States)

    Poppe, A.; Samad, R.; Halekas, J. S.; Sarantos, M.; Delory, G. T.; Farrell, W. M.; Angelopoulos, V.

    2012-12-01

    Since lunar orbit insertion in the summer of 2011, the two ARTEMIS spacecraft have made repeated measurements of lunar-based pick-up ions within the terrestrial magnetotail lobes. These ions are often detected as two separate focused beams above the dayside lunar surface, although they can sometimes be detected farther from the Moon. Analysis of these beams has shown that they possess both field-aligned and field-perpendicular velocities, implying the presence of electric fields both parallel and perpendicular to the magnetotail lobe magnetic field. We use the energy and pitch angle spectra to constrain the source locations and compositions of these ions, and conclude that exospheric ionization of the neutral exosphere is the dominant lunar pick-up ion production mechanism in the tail lobes. We also present evidence that one sub-population of these ions are coming from a discrete source on the lunar surface, possible a geologic vent. Finally, we present preliminary results from particle-tracing models of pick-up ion dynamics in the terrestrial magnetotail in order to help constrain the neutral source distribution(s) for these pick-up ions.

  7. An assessment of the conditions for critical velocity ionization at the weakly magnetized planets

    Science.gov (United States)

    Luhmann, J. G.; Russell, C. T.

    1990-01-01

    It has been proposed that critical velocity ionization (CVI) may occur in the magnetosheaths of weakly magnetized planets where the solar wind flows through the planets' upper atmospheres. One can examine this possibility for Venus and Mars by using magnetosheath flow and exosphere models to determine whether the criteria for CVI are met. These criteria include Brenning's empirical condition on the cross-field flow velocity (it must not exceed the local magnetosonic velocity) and the 'Townsend condition' requiring that the integrated probability of impact ionization by a hot electron be greater than 1 along a streamline past the planet. Application of the Spreiter-Stahara gas dynamic flow model and the Nagy and coworkers' models for the exospheres lead to the conclusion that the conditions can be met in a limited region near Venus. However, evidence for CVI has not been identified in in-situ data. Since key details of the planet-solar wind interaction can be explained in terms of photoionization alone, other signatures of the process must be sought in the observations if the presence of CVI is to be positively inferred.

  8. The Solar Wind as a Magnetofluid Turbulence Laboratory

    Science.gov (United States)

    Goldstein, Melvyn L.

    2011-01-01

    The solar wind is the Sun's exosphere. As the solar atmosphere expands into interplanetary space, it is accelerated and heated. Data from spacecraft located throughout the heliosphere have revealed that this exosphere has velocities of several hundred kilometers/sec, densities at Earth orbit of about 5 particles/cu cm, and an entrained magnetic field that at Earth orbit that is about 5 10-5 Gauss. A fascinating feature of the solar wind is that the magnetic field fluctuates in a way that is highly reminiscent of "Alfven waves, i.e., the fluctuating magnetic fields are more-or-less aligned with fluctuations in the velocity of the plasma and, with proper normalization, have approximately equal magnitudes. The imperfect (observed) alignment leads to a variety of complex interactions. In many respects, the flow patterns appear to be an example of fully developed magneto fluid turbulence. Recently, the dissipation range of this turbulence has been studied using search coil magnetometer data from the STAFF instrument on the four Cluster spacecraft. I will attempt to give an overview of selected properties of this large-scale and small-scale turbulence.

  9. The Solar Wind as a Laboratory for the Study of Magnetofluid Turbulence

    Science.gov (United States)

    Goldstein, Melvyn L.

    2011-01-01

    The solar wind is the Sun's exosphere. As the solar atmosphere expands into interplanetary space, it is accelerated and heated. Data from spacecraft located throughout the heliosphere have revealed that this exosphere has velocities of several hundred kilometers/sec, densities at Earth orbit of about 5 particles/cm(exp 3), and an entrained magnetic field that at Earth orbit that is about 5 X 10(exp 5) Gauss. A fascinating feature of this magnetized plasma, which is a gas containing both charged particles and magnetic field, is that the magnetic field fluctuates in a way that is highly reminiscent of "Alfven waves", first defined by Hannes Alfven in 1942. Such waves have the defining property that the fluctuating magnetic fields are aligned with fluctuations in the velocity of the plasma and that, when properly normalized, the fluctuations have equal magnitudes. The observed alignment is not perfect and the resulting mismatch leads to a variety of complex interactions. In many respects, the flow patterns appear to be an example of fully developed magnetofluid turbulence. Recently, the dissipation range of this turbulence has been revealed by Search Coil magnetometer data from the four Cluster spacecraft. This tutorial will describe some of the properties of the large-scale and small-scale turbulence.

  10. Theoretical UV absorption spectra of hydrodynamically escaping O{sub 2}/CO{sub 2}-rich exoplanetary atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Gronoff, G.; Mertens, C. J.; Norman, R. B. [NASA LaRC, Hampton, VA (United States); Maggiolo, R. [BIRA-IASB, Avenue Circulaire 3, 1180 Brussels (Belgium); Wedlund, C. Simon [Aalto University School of Electrical Engineering Department of Radio Science and Engineering, P.O. Box 13000, FI-00076 Aalto (Finland); Bell, J. [National Institute of Aerospace, Hampton, VA (United States); Bernard, D. [IPAG, Grenoble (France); Parkinson, C. J. [University of Michigan, MI (United States); Vidal-Madjar, A., E-mail: Guillaume.P.Gronoff@nasa.gov [Observatoire de Paris, Paris (France)

    2014-06-20

    Characterizing Earth- and Venus-like exoplanets' atmospheres to determine if they are habitable and how they are evolving (e.g., equilibrium or strong erosion) is a challenge. For that endeavor, a key element is the retrieval of the exospheric temperature, which is a marker of some of the processes occurring in the lower layers and controls a large part of the atmospheric escape. We describe a method to determine the exospheric temperature of an O{sub 2}- and/or CO{sub 2}-rich transiting exoplanet, and we simulate the respective spectra of such a planet in hydrostatic equilibrium and hydrodynamic escape. The observation of hydrodynamically escaping atmospheres in young planets may help constrain and improve our understanding of the evolution of the solar system's terrestrial planets' atmospheres. We use the dependency of the absorption spectra of the O{sub 2} and CO{sub 2} molecules on the temperature to estimate the temperature independently of the total absorption of the planet. Combining two observables (two parts of the UV spectra that have a different temperature dependency) with the model, we are able to determine the thermospheric density profile and temperature. If the slope of the density profile is inconsistent with the temperature, then we infer the hydrodynamic escape. We address the question of the possible biases in the application of the method to future observations, and we show that the flare activity should be cautiously monitored to avoid large biases.

  11. Suprathermal oxygen atoms in the Martian upper atmosphere: Contribution of the proton and hydrogen atom precipitation

    Science.gov (United States)

    Shematovich, V. I.

    2017-07-01

    This is a study of the kinetics and transport of hot oxygen atoms in the transition region (from the thermosphere to the exosphere) of the Martian upper atmosphere. It is assumed that the source of the hot oxygen atoms is the transfer of momentum and energy in elastic collisions between thermal atmospheric oxygen atoms and the high-energy protons and hydrogen atoms precipitating onto the Martian upper atmosphere from the solar-wind plasma. The distribution functions of suprathermal oxygen atoms by the kinetic energy are calculated. It is shown that the exosphere is populated by a large number of suprathermal oxygen atoms with kinetic energies up to the escape energy 2 eV; i.e., a hot oxygen corona is formed around Mars. The transfer of energy from the precipitating solar-wind plasma protons and hydrogen atoms to the thermal oxygen atoms leads to the formation of an additional nonthermal escape flux of atomic oxygen from the Martian atmosphere. The precipitation-induced escape flux of hot oxygen atoms may become dominant under the conditions of extreme solar events, such as solar flares and coronal mass ejections, as shown by recent observations onboard NASA's MAVEN spacecraft (Jakosky et al., 2015).

  12. A new model of the lunar ejecta cloud

    Science.gov (United States)

    Christou, A. A.

    2014-04-01

    Every airless body in the solar system is surrounded by a cloud of ejecta produced by the impact of interplanetary meteoroids on its surface [1]. Such "dust exospheres" have been observed around the Galilean satellites of Jupiter [2, 3]. The prospect of long-term robotic and human operations on the Moon by the US and other countries has rekindled interest on the subject [4]. This interest has culminated with the recent investigation of the Moon's dust exosphere by the LADEE spacecraft [5]. Here a model is presented of a ballistic, collisionless, steady state population of ejecta launched vertically at randomly distributed times and velocities. Assuming a uniform distribution of launch times I derive closed form solutions for the probability density functions (pdfs) of the height distribution of particles and the distribution of their speeds in a rest frame both at the surface and at altitude. The treatment is then extended to particle motion with respect to a moving platform such as an orbiting spacecraft. These expressions are compared with numerical simulations under lunar surface gravity where the underlying ejection speed distribution is (a) uniform (b) a power law. I discuss the predictions of the model, its limitations, and how it can be validated against near-surface and orbital measurements.

  13. Lunar Solar Origins Exploration (LunaSOX)

    Science.gov (United States)

    Cooper, John F.; King, Joseph H.; Papitashvili, Natasha; Lipatov, Alexander S.; Sittler, Edward C.; Hartle, Richard E.

    2011-01-01

    The Moon offers a unique vantage point from which to investigate the Sun and its interaction via the solar wind magnetic fields, plasma, and energetic particles with the geospace system including the Moon itself. The lunar surface and exosphere provide in part a record of solar coronal plasma material input and resultant space weathering over billions of years. The structure and dynamics of solar wind interactions with the Moon provide an accessible near-Earth laboratory environment for study of general solar wind interactions with the vast multitude of airless asteroidal bodies of the inner solar system. Spacecraft in lunar orbit have the often simultaneous opportunity, except when in the Earth's magnetosphere, to make in-situ compositional measurements of the solar wind plasma and to carry out remote observations from the Moon of the solar corona, potentially enabled by lunar limb occultation of the solar disk. The LunaSOX project at NASA Goddard Space Flight Center is addressing these heliophysical science objectives from and of the Moon with support from NASA's Lunar Advanced Science and Exploration Research (LASER) program: (1) specify history of solar wind parameters at and sunward of the Moon through enhanced access (http://lunasox.gsfc.nasa.gov/) to legacy and operational mission data products from the Apollo era to the present, (2) model field and plasma interactions with the lunar surface, exosphere, and wake, as constrained by the available data, through hybrid kinetic code simulations, and (3) advance mission concepts for heliophysics from and of the Moon.

  14. Solar Wind Interaction with the Martian Upper Atmosphere at Early Mars/Extreme Solar Conditions

    Science.gov (United States)

    Dong, C.; Bougher, S. W.; Ma, Y.; Toth, G.; Lee, Y.; Nagy, A. F.; Tenishev, V.; Pawlowski, D. J.; Combi, M. R.

    2014-12-01

    The investigation of ion escape fluxes from Mars, resulting from the solar wind interaction with its upper atmosphere/ionosphere, is important due to its potential impact on the long-term evolution of Mars atmosphere (e.g., loss of water) over its history. In the present work, we adopt the 3-D Mars cold neutral atmosphere profiles (0 ~ 300 km) from the newly developed and validated Mars Global Ionosphere Thermosphere Model (M-GITM) and the 3-D hot oxygen profiles (100 km ~ 5 RM) from the exosphere Monte Carlo model Adaptive Mesh Particle Simulator (AMPS). We apply these 3-D model output fields into the 3-D BATS-R-US Mars multi-fluid MHD (MF-MHD) model (100 km ~ 20 RM) that can simulate the interplay between Mars upper atmosphere and solar wind by considering the dynamics of individual ion species. The multi-fluid MHD model solves separate continuity, momentum and energy equations for each ion species (H+, O+, O2+, CO2+). The M-GITM model together with the AMPS exosphere model take into account the effects of solar cycle and seasonal variations on both cold and hot neutral atmospheres. This feature allows us to investigate the corresponding effects on the Mars upper atmosphere ion escape by using a one-way coupling approach, i.e., both the M-GITM and AMPS model output fields are used as the input for the multi-fluid MHD model and the M-GITM is used as input into the AMPS exosphere model. In this study, we present M-GITM, AMPS, and MF-MHD calculations (1-way coupled) for 2.5 GYA conditions and/or extreme solar conditions for present day Mars (high solar wind velocities, high solar wind dynamic pressure, and high solar irradiance conditions, etc.). Present day extreme conditions may result in MF-MHD outputs that are similar to 2.5 GYA cases. The crustal field orientations are also considered in this study. By comparing estimates of past ion escape rates with the current ion loss rates to be returned by the MAVEN spacecraft (2013-2016), we can better constrain the

  15. Searching for Lunar Horizon Glow with the LRO Star Tracker Cameras

    Science.gov (United States)

    Stubbs, T. J.; Wang, Y.; Glenar, D. A.; McClanahan, T. P.; Myers, D. C.; Keller, J. W.

    2015-12-01

    Apollo-era observations of "lunar horizon glow" phenomena have been interpreted as being due to the forward scattering of sunlight by very small dust grains above the lunar surface. High altitude lunar horizon glow (LHG) seen in coronal photographs taken above orbital sunset during Apollo 15 is consistent with a population of exospheric dust grains with radii of ≈0.1 μm extending to altitudes of ≈10 km; while near-surface LHG observed by the TV cameras aboard a few of the Surveyor landers is consistent with dust grains with radii of ≈5 μm within about a meter of the surface. More recent searches have been undertaken for high altitude LHG, or the associated dust population, using the Clementine star tracker cameras (sensitive to visible and near-IR), the Lyman Alpha Mapping Project (LAMP) far-UV spectrograph on the Lunar Reconnaissance Orbiter (LRO), and the Lunar Dust Experiment (LDEX) on the Lunar Atmosphere and Dust Environment Explorer (LADEE). These searches have only produced upper limits for these exospheric dust abundances, as opposed to a clear detection. This motivated a search for LHG with the LRO star tracker cameras. Despite being designed for spacecraft navigation, the images these cameras produce are very suitable for scientific use. They also offer benefits over instruments previously used in terms of spatial resolution and ability to probe to low altitudes (both are of order a few hundred meters at the limb), as well as sensitivity to a similar wavelength range as the Apollo-era observations. Interestingly, the initial series of searches have resulted in some images that show bright patches at the limb that could be possible evidence for LHG. However, since these patches appear to typically extend only ~1000 m horizontally and just a few hundred meters vertically, this raises the possibility that they are simply due to sunlight reflected off surface topography along the limb. Initial simulations using a 64 pixel/degree digital elevation

  16. The Exploration of Mercury by MESSENGER: Looking Ahead to Orbital Observations

    Science.gov (United States)

    Solomon, S. C.; McNutt, R. L.; Bedini, P. D.; Anderson, B. J.; Prockter, L. M.; Blewett, D. T.; Evans, L. G.; Gold, R. E.; Krimigis, S. M.; Murchie, S. L.; Nittler, L. R.; Phillips, R. J.; Slavin, J. A.; Zuber, M. T.

    2010-12-01

    NASA's MESSENGER spacecraft flew by Mercury three times in 2008-09 en route to insertion into orbit about the planet in March 2011. The flybys confirmed that the planet's internal magnetic field is dominantly dipolar, with a vector moment closely aligned with the spin axis. MESSENGER detected Mg and Ca+ in Mercury’s exosphere, demonstrated that Mercury's anti-sunward neutral tail contains multiple species, and revealed that exospheric Na, Ca, and Mg vary differently with space and time, signatures of multiple source processes. MESSENGER's laser altimeter showed that the equatorial topographic relief of Mercury exceeds 5 km, revealed an equatorial ellipticity aligned with the ellipticity in Mercury's gravitational potential, and profiled numerous impact craters and fault scarps. MESSENGER images provided evidence for widespread volcanism, and candidate sites for volcanic centers were identified. Newly imaged lobate scarps and other tectonic landforms support the hypothesis that Mercury contracted globally in response to interior cooling. The ˜1500-km-diameter Caloris basin was a focus for volcanic centers, some with evidence of pyroclastic deposits, and widespread contractional and extensional deformation; smooth plains interior and exterior to the basin postdate the basin-forming event. The interior plains of the ˜290-km-diameter Rachmaninoff basin are among the youngest volcanic material on the planet. Mercury surface units are distinguishable by color and composition; smooth plains occupy ˜40% of the surface area, and low-reflectance material occupies ˜15% of the surface area and is primarily seen in deposits excavated by impact. Reflectance spectra show no evidence for FeO in surface silicates, and reflectance and color imaging observations support the view that Mercury's surface material consists dominantly of Fe-poor, Ca-Mg silicates with an admixture of spectrally neutral opaque minerals. In support of the hypothesis that those opaque minerals are Fe

  17. A 2016 Ganymede stellar occultation event

    Science.gov (United States)

    D'Aversa, Emiliano; Oliva, Fabrizio; Sindoni, Giuseppe; Hinse, Tobias Cornelius; Plainaki, Christina; Aoki, Shohei; Person, Michael J.; Carlson, Robert W.; Orton, Glenn S.

    2017-04-01

    On 2016 April,13th the Jovian satellite Ganymede occulted a 7th magnitude star. The predicted occultation track crossed the Northern Pacific Ocean, Japan, and South Korea. Hence, it was a very favorable event due to the star brightness and to the visibility from the large aperture telescopes at Hawaii. While no other similar event is expected for the next 10 years, only two occultation events are reported in literature in the past, from Earth in 1972 [1] and from Voyager [2], in large disagreement in respect to the atmosphere detection. However, evidence of an exosphere around Ganymede was inferred by [3], through H Lyman alpha emission detected by Galileo UVS, and by [4], through HST/GHRS detection of far-UV atomic O airglow emissions, signature of dissociated molecular oxygen ([5],[6]). Later, the HST/STIS observations by [7] provided further evidence for exospheric neutral hydrogen. Since Ganymede is known to have an intrinsic magnetic field ([8]) reconnecting with the Jovian magnetic field and (partially) shielding the surface equatorial latitudes from the electron impact, the UV emissions have been so far attributed to auroral processes ([6]). Nevertheless, the physical mechanisms governing these processes are not known with certainty (e.g. whether the emissions morphology is determined by the spatial distribution of magnetospheric electrons or by an uneven O2 exosphere or both, see e.g.[9]). We took advantage of this event in order to search for a signature of Ganymede's exosphere in the occultation light curve, by using facilities on Mauna Kea at Hawaii (NASA-IRTF observatory) and at Sobaeksan Optical Astronomy Observatory (SOAO) in South Korea. At IRTF, both MORIS [10] and SpeX [11] instruments have been used, fed by the same optical entrance through a dichroic beam splitter at 0.95 micron. MORIS acquired a high-rate sequence of images about 0.25 sec apart in the visible range, while SpeX acquired a sequence of spectra at a bit lower rate, covering the 0

  18. Transport, charge exchange and loss of energetic heavy ions in the earth's radiation belts - Applicability and limitations of theory

    Science.gov (United States)

    Spjeldvik, W. N.

    1981-01-01

    Computer simulations of processes which control the relative abundances of ions in the trapping regions of geospace are compared with observations from discriminating ion detectors. Energy losses due to Coulomb collisions between ions and exospheric neutrals are considered, along with charge exchange losses and internal charge exchanges. The time evolution of energetic ion fluxes of equatorially mirroring ions under radial diffusion is modelled to include geomagnetic and geoelectric fluctutations. Limits to the validity of diffusion transport theory are discussed, and the simulation is noted to contain provisions for six ionic charge states and the source effect on the radiation belt oxygen ion distributions. Comparisons are made with ion flux data gathered on Explorer 45 and ISEE-1 spacecraft and results indicate that internal charge exchanges cause the radiation belt ion charge state to be independent of source charge rate characteristics, and relative charge state distribution is independent of the radially diffusive transport rate below the charge state redistribution zone.

  19. Magnetic moment and plasma environment of HD 209458b as determined from Ly$\\alpha$ observations

    CERN Document Server

    Kislyakova, K G; Lammer, H; Odert, P; Khodachenko, M L

    2014-01-01

    Transit observations of HD 209458b in the stellar Lyman-$\\alpha$ (Ly$\\alpha$) line revealed strong absorption in both blue and red wings of the line interpreted as hydrogen atoms escaping from the planet's exosphere at high velocities. The following sources for the absorption were suggested: acceleration by the stellar radiation pressure, natural spectral line broadening, charge exchange with stellar wind. We reproduce the observation by means of modelling that includes all aforementioned processes. Our results support a stellar wind with a velocity of $\\approx400$ km$\\times$s$^{-1}$ at the time of the observation and a planetary magnetic moment of $\\approx 1.6 \\times 10^{26}$ A$\\times$m$^2$.

  20. Microchannel plate life testing for UV spectroscopy instruments

    Science.gov (United States)

    Darling, N. T.; Siegmund, O. H. W.; Curtis, T.; McPhate, J.; Tedesco, J.; Courtade, S.; Holsclaw, G.; Hoskins, A.; Al Dhafri, S.

    2017-08-01

    The Emirates Mars Mission (EMM) UV Spectrograph (EMUS) is a far ultraviolet (102 nm to 170 nm) imaging spectrograph for characterization of the Martian exosphere and thermosphere. Imaging is accomplished by a photon counting open-face microchannel plate (MCP) detector using a cross delay line (XDL) readout. An MCP gain stabilization ("scrub") followed by lifetime spectral line burn-in simulation has been completed on a bare MCP detector at SSL. Gain and sensitivity stability of better than 7% has been demonstrated for total dose of 2.5 × 1012 photons cm-2 (2 C · cm-2 ) at 5.5 kHz mm-2 counting rates, validating the efficacy of an initial low gain full-field scrub.

  1. HAZE AT OCCATOR CRATER ON DWARF PLANET CERES

    Energy Technology Data Exchange (ETDEWEB)

    Thangjam, G.; Hoffmann, M.; Nathues, A.; Platz, T. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Goettingen (Germany); Li, J.-Y., E-mail: thangjam@mps.mpg.de, E-mail: hoffmann@mps.mpg.de, E-mail: nathues@mps.mpg.de, E-mail: platz@mps.mpg.de, E-mail: jyli@psi.edu [Planetary Science Institute, 1700 East Fort Lowell Rd., Suite 106, Tucson, AZ 85719-2395 (United States)

    2016-12-20

    A diurnal varying haze layer at the bright spots of Occator on dwarf planet Ceres has been reported from images of the Dawn Framing Camera. This finding is supported by ground-based observations revealing diurnal albedo changes at Occator’s longitude. In the present work, we further investigate the previously reported haze phenomenon in more detail using additional Framing Camera images. We demonstrate that the light scattering behavior at the central floor of Occator is different compared to a typical cerean surface and is likely inconsistent with a pure solid surface scatterer. The identified deviation is best explained by an additional component to the scattered light of the surface, i.e., a haze layer. Our results support the water vapor detection by Herschel observations though the existence of a tenuous cerean exosphere is not yet confirmed.

  2. Return to Mercury: a global perspective on MESSENGER's first Mercury flyby.

    Science.gov (United States)

    Solomon, Sean C; McNutt, Ralph L; Watters, Thomas R; Lawrence, David J; Feldman, William C; Head, James W; Krimigis, Stamatios M; Murchie, Scott L; Phillips, Roger J; Slavin, James A; Zuber, Maria T

    2008-07-04

    In January 2008, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft became the first probe to fly past the planet Mercury in 33 years. The encounter revealed that Mercury is a dynamic system; its liquid iron-rich outer core is coupled through a dominantly dipolar magnetic field to the surface, exosphere, and magnetosphere, all of which interact with the solar wind. MESSENGER images confirm that lobate scarps are the dominant tectonic landform and record global contraction associated with cooling of the planet. The history of contraction can be related to the history of volcanism and cratering, and the total contractional strain is at least one-third greater than inferred from Mariner 10 images. On the basis of measurements of thermal neutrons made during the flyby, the average abundance of iron in Mercury's surface material is less than 6% by weight.

  3. Imaging the Sources and Full Extent of the Sodium Tail of the Planet Mercury

    Science.gov (United States)

    Baumgardner, Jeffrey; Wilson, Jody; Mendillo, Michael

    2008-01-01

    Observations of sodium emission from Mercury can be used to describe the spatial and temporal patterns of sources and sinks in the planet s surface-boundary-exosphere. We report on new data sets that provide the highest spatial resolution of source regions at polar latitudes, as well as the extraordinary length of a tail of escaping Na atoms. The tail s extent of approx.1.5 degrees (nearly 1400 Mercury radii) is driven by radiation pressure effects upon Na atoms sputtered from the surface in the previous approx.5 hours. Wide-angle filtered-imaging instruments are thus capable of studying the time history of sputtering processes of sodium and other species at Mercury from ground-based observatories in concert with upcoming satellite missions to the planet. Plasma tails produced by photo-ionization of Na and other gases in Mercury s neutral tails may be observable by in-situ instruments.

  4. Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

    Science.gov (United States)

    Collier, Michael R.; Newheart, Anastasia; Poppe, Andrew R.; Hills, H. Kent; Farrell, William M.

    2016-01-01

    We present examples of unusual "stair-step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface-based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote-sensing orbiter observations on the Moon's exospheric and electrostatic properties.

  5. A new view on the solar wind interaction with the Moon

    CERN Document Server

    Bhardwaj, Anil; Alok, Abhinaw; Barabash, Stas; Wieser, Martin; Futaana, Yoshifumi; Wurz, Peter; Vorburger, Audrey; Holmström, Mats; Lue, Charles; Harada, Yuki; Asamura, Kazushi

    2015-01-01

    Characterised by a surface bound exosphere and localised crustal magnetic fields, the Moon was considered as a passive object when solar wind interacts with it. However, the neutral particle and plasma measurements around the Moon by recent dedicated lunar missions, such as Chandrayaan-1, Kaguya, Chang'E-1, LRO, and ARTEMIS, as well as IBEX have revealed a variety of phenomena around the Moon which results from the interaction with solar wind, such as backscattering of solar wind protons as energetic neutral atoms (ENA) from lunar surface, sputtering of atoms from the lunar surface, formation of a "mini-magnetosphere" around lunar magnetic anomaly regions, as well as several plasma populations around the Moon, including solar wind protons scattered from the lunar surface, from the magnetic anomalies, pick-up ions, protons in lunar wake and more. This paper provides a review of these recent findings and presents the interaction of solar wind with the Moon in a new perspective.

  6. A theory of local and global processes which affect solar wind electrons. 1: The origin of typical 1 AU velocity distribution functions: Steady state theory

    Science.gov (United States)

    Scudder, J. D.

    1978-01-01

    A detailed first principle kinetic theory for electrons which is neither a classical fluid treatment nor an exospheric calculation is presented. This theory illustrates the global and local properties of the solar wind expansion that shape the observed features of the electron distribution function, such as its bifurcation, its skewness and the differential temperatures of the thermal and suprathermal subpopulations. Coulomb collisions are substantial mediators of the interplanetary electron velocity distribution function and they place a zone for a bifurcation of the electron distribution function deep in the corona. The local cause and effect precept which permeates the physics of denser media is modified for electrons in the solar wind. The local form of transport laws and equations of state which apply to collision dominated plasmas are replaced with global relations that explicitly depend on the relative position of the observer to the boundaries of the system.

  7. Kinematics effects of atmospheric friction in spacecraft flybys

    Science.gov (United States)

    Acedo, L.

    2017-04-01

    Gravity assist manoeuvres are one of the most successful techniques in astrodynamics. In these trajectories the spacecraft comes very close to the surface of the Earth, or other Solar system planets or moons, and, as a consequence, it experiences the effect of atmospheric friction by the outer layers of the Earth's atmosphere or ionosphere. In this paper we analyze a standard atmospheric model to estimate the density profile during the two Galileo flybys, the NEAR and the Juno flyby. We show that, even allowing for a margin of uncertainty in the spacecraft cross-section and the drag coefficient, the observed - 8 mm/s anomalous velocity decrease during the second Galileo flyby of December 8th 1992 cannot be attributed only to atmospheric friction. On the other hand, for perigees on the border between the thermosphere and the exosphere the friction only accounts for a fraction of a millimeter per second in the final asymptotic velocity.

  8. Mars atmospheric losses induced by the solar wind: current knowledge and perspective

    Science.gov (United States)

    Ermakov, Vladimir; Zelenyi, Lev; Vaisberg, Oleg; Sementsov, Egor; Dubinin, Eduard

    2017-04-01

    Solar wind induced atmospheric losses have been studied since earlier 1970th. Several loss channels have been identified including pick-up of exospheric photo-ions and ionospheric ions escape. Measurements performed during several solar cycles showed variation of these losses by about factor of 10, being largest at maximum solar activity. MAVEN spacecraft equipped with comprehensive set of instruments with high temporal and mass resolution operating at Mars since fall 2014 ensures much better investigation of solar wind enforcing Martian environment, Mars atmospheric losses processes and mass loss rate. These issues are very important for understanding of Martian atmospheric evolution including water loss during cosmogonic time. Simultaneous observations by MAVEN and MEX spacecraft open the new perspective in study of Martian environment. In this report we discuss results of past and current missions and preliminary analysis of heavy ions escape using simultaneous measurements of MEX and MAVEN spacecraft.

  9. Venus: The Atmosphere, Climate, Surface, Interior and Near-Space Environment of an Earth-Like Planet

    Science.gov (United States)

    Taylor, Fredric W.; Svedhem, Håkan; Head, James W.

    2018-02-01

    This is a review of current knowledge about Earth's nearest planetary neighbour and near twin, Venus. Such knowledge has recently been extended by the European Venus Express and the Japanese Akatsuki spacecraft in orbit around the planet; these missions and their achievements are concisely described in the first part of the review, along with a summary of previous Venus observations. The scientific discussions which follow are divided into three main sections: on the surface and interior; the atmosphere and climate; and the thermosphere, exosphere and magnetosphere. These reports are intended to provide an overview for the general reader, and also an introduction to the more detailed topical surveys in the following articles in this issue, where full references to original material may be found.

  10. A 3D Multi-fluid MHD Study of the Interaction of the Solar Wind with the Ionosphere/Atmosphere System of Mars.

    Science.gov (United States)

    Najib, Dalal; Nagy, Andrew; Toth, Gabor; Ma, Yingjuan

    We use our new four species multi-fluid model to study the interaction of the solar wind with Mars. The lower boundary of our model is at 100 km, below the main ionospheric peak, and the radial resolution is about 10 km in the ionosphere, thus the model does a very good job in reproducing the ionosphere and the associated processes. We carry out calculations for high and low solar activity conditions and establish the importance of mass loading by the extended exosphere of Mars. We also calculate the atmospheric escape of the ionospheric species, including pick up ions. Finally, we compare our model results with the Viking, MGS and Mars Express observations.

  11. A 3D Multi-fluid MHD Study of the Interaction of the Solar Wind with the Ionosphere/Atmosphere System of Venus.

    Science.gov (United States)

    Najib, D.; Nagy, A.; Toth, G.; Ma, Y.-J.

    2011-10-01

    We use the latest version of our four species multifluid model to study the interaction of the solar wind with Venus. The model solves simultaneously the continuity, momentum and energy equations of the different ions. The lower boundary of our model is at 100 km, below the main ionospheric peak, and the radial resolution is about 10 km in the ionosphere, thus the model does a very good job in reproducing the ionosphere and the associated processes. We carry out calculations for high and low solar activity conditions and establish the importance of mass loading by the extended exosphere of Venus. We demonstrate the importance of using the multi-fluid rather than a single fluid model. We also calculate the atmospheric escape of the ionospheric species and compare our model results with the observed parameters from Pioneer Venus and Venus Express.

  12. Venus Interior Probe Using In-Situ Power and Propulsion (VIP-INSPR)

    Science.gov (United States)

    Bugga, Ratnakumar V.

    2016-01-01

    Venus, despite being our closest neighboring planet, is under-explored due to its hostile and extreme environment, with a 92 bar pressure and 467 C temperature at the surface. The temperature decreases at higher altitudes, almost at the rate of 7.9 C/km, reaching the Earth surface conditions at 65 km. Due to the less extreme conditions, balloon missions could survive as long as 46 h at an altitude of 54 km. However, because of the opacity of the Venus atmosphere filled with clouds of sulfuric acid and CO2, orbiter or balloon missions are not as revealing and informative in characterizing the surface, as similar missions on Moon and Mars. To understand the evolutionary paths of Venus in relation to Earth, it is imperative to gather basic information on the crust, mantle, core, atmosphere/exosphere and bulk composition of Venus, through in-situ investigations using landers, probes and variable altitude areal platforms.

  13. SELMA: a mission to study lunar environment and surface interaction

    Science.gov (United States)

    Barabash, Stas; Futaana, Yoshifumi

    2017-04-01

    SELMA (Surface, Environment, and Lunar Magnetic Anomalies) proposed for the ESA M5 mission opportunity is a mission to study how the Moon environment and surface interact. SELMA addresses four overarching science questions: (1) What is the origin of water on the Moon? (2) How do the "volatile cycles" on the Moon work? (3) How do the lunar mini-magnetospheres work? (4) What is the influence of dust on the lunar environment and surface? SELMA uses a unique combination of remote sensing via UV, IR, and energetic neutral atoms and local measurements of plasma, fields, waves, exospheric gasses, and dust. It will also conduct an impact experiment to investigate volatile content in the soil of the permanently shadowed area of the Shakleton crater. SELMA carries an impact probe to sound the Reiner-Gamma mini-magnetosphere and its interaction with the lunar regolith from the SELMA orbit down to the surface. The SELMA science objectives include: - Establish the role of the solar wind and exosphere in the formation of the water bearing materials; - Determine the water content in the regolith of the permanently shadowed region and its isotope composition; - Establish variability, sources and sinks of the lunar exosphere and its relations to impact events; - Investigate a mini-magnetosphere interaction with the solar wind; - Investigate the long-term effects of mini-magnetospheres on the local surface; - Investigate how the impact events affect the lunar dust environments; - Investigate how the plasma effects result in lofting the lunar dust; SELMA is a flexible and short (15 months) mission including the following elements SELMA orbiter, SELMA Impact Probe for Magnetic Anomalies (SIP-MA), passive Impactor, and Relaying CubeSat (RCS). SELMA is placed on quasi-frozen polar orbit 30 km x 200 km with the pericenter over the South Pole. Approximately 9 months after the launch SELMA releases SIP-MA to sound the Reiner-Gamma magnetic anomaly with very high time resolution 10 sec

  14. Remote Observations of the Lunar Sodium Corona

    Science.gov (United States)

    Killen, Rosemary M.; Morgan, Thomas H.; Potter, Andrew; SSERVI DREAM2

    2017-10-01

    We have designed, built and installed a small robotic coronagraph at the Winer Observatory in Sonoita, Arizona, in order to observe the sodium exosphere out to one-half degree around the Moon. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Center. Our data encompass lunations in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images. We employ an Andover temperature-controlled 1.5 Å wide narrow-band filter centered on the sodium D2 line, and a similar 1.5 Å filter centered blueward of the D2 line by 5 Å. Exposures of 10 minutes are required to image the sodium corona at good signal to noise. Autoguiding is performed locking onto a small bright crater each night. Following each onband-offband exposure pair, on- and off-band images of the lunar surface are collected by taking a 0.1- 0.5 second exposures with the open filter. The sodium is calibrated using the counts in the open Moon images and the Hapke function. We use both dark and bright Hapke parameters for comparison check using Mare and highlands, respectively. In order to obtain the sodium profile around the entire limb, the images are transformed using a polar transform and the profiles are extracted automatically. Example of our resulting images of the sodium corona will be shown, with the image of the moon's disk (taken subsequently to the occulted coronal image) superimposed on the occulting disk, thus showing the position and phase of the moon under the disk. We compare our lunar model derived from these observations with the data from the UV spectrograph onboard the LADEE spacecraft.

  15. LADEE UVS Observations of Atoms and Dust in the Lunar Tail

    Science.gov (United States)

    Wooden, Diane H.; Colaprete, Anthony; Cook, Amanda M.; Shirley, Mark H.; Vargo, Kara E.; Elphic, Richard C.; Stubbs, Timothy J.; Glenar, David A.

    2014-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) was a lunar orbiter launched in September 2013 that investigated the composition and temporal variation of the tenuous lunar exosphere and dust environment. A major goal of the mission was to characterize the dust exosphere prior to future lunar exploration activities, which may alter the lunar environment. The Ultraviolet/Visible Spectrometer (UVS) onboard LADEE addresses this goal, utilizing two sets of optics: a limbviewing telescope, and a solar-viewing telescope. We report on spectroscopic (approximately 280 - 820 nm) observations viewing down the lunar wake or along the 'lunar tail' from lunar orbit. Prior groundbased studies have observed the emission from neutral sodium atoms extended along the lunar tail, so often this region is referred to as the lunar sodium tail. UVS measurements were made on the dark side of the moon, with the UVS limb-viewing telescope pointed outward in the direction of the Moon's wake (almost anti-sun), during different lunar phases. These UVS observation activities sample a long column and allow the characterization of scattered light from dust and emission lines from atoms in the lunar tail. Observations in this UVS configuration show the largest excess of scattered blue light in our data set, indicative of the presence of small dust grains in the tail. Once lofted, nanoparticles may become charged and picked up by the solar wind, similar to the phenomena witnessed above Enceladus's northern hemisphere or by the STEREO/WAVES instrument while close to Earth's orbit. The UVS data show that small dust grains as well as atoms become entrained in the lunar tail.

  16. Calibrating ACS-SBC Using STIS at Lyman Alpha (121.567 nm)

    Science.gov (United States)

    Bhattacharyya, Dolon

    2017-08-01

    This short calibration program is needed to correctly interpret existing STIS and ACS data on the exospheres of several solar system objects. It will allow us to calibrate observations of planetary exospheres, and to quantitatively determine the atmospheric escape flux, from Mars, Uranus, Titan and other solar system objects, and to contribute to the calibration of the MAVEN IUVS instrument. The need for added calibration is driven by the large uncertainty in the sensitivity of ACS/SBC images at H Lyman alpha (121.6 nm) and also by the lack of a Lyman alpha flat field for STIS G140L long aperture spectra, in both cases for diffuse emissions. The STIS instrument sensitivity is well calibrated at Lyman alpha in the G140L mode through calibration star observations, but there is no flat field specifically at Lyman alpha for diffuse emissions filling the aperture. The ACS/SBC F115 mode is calibrated for a mean wavelength in the bandpass, but as an imaging instrument the specific sensitivity at Lyman alpha has not been measured. These calibrations could be obtained through observations of the geocoronal Lyman alpha emission, comparing the count rates of STIS G140L and ACS/SBC for the same diffuse source brightness, and obtaining the STIS Lyman alpha flat field from the observations of diffuse emission. This study will be beneficial for both the planetary and the astrophysics community as hydrogen is the most abundant element in our universe and Lyman alpha is the most probable transition in H atoms. The flat field for STIS in Lyman alpha will benefit the analysis of past and future GO program data and will be delivered to STScI for use by the observational community.

  17. Towards a Carbon Nanotube Ionization Source for Planetary Atmosphere Exploration

    Science.gov (United States)

    Oza, A. V.; Leblanc, F.; Berthelier, J. J.; Becker, J.; Coulomb, R.; Gilbert, P.; Hong, N. T.; Lee, S.; Vettier, L.

    2015-12-01

    The characterization of planetary exospheres today, relies on the development of a highly efficient ionization source, due to the scant neutral molecules (n < 108 cm -3) present in diffuse planetary coronae. These tenuous atmospheres provide insight on to physical processes known to occur such as: space weathering, magneto-atmosphere interactions, as well as atmospheric escape mechanisms, all of which are being heavily investigated via current 3D Monte Carlo simulations (Turc et al. 2014, Leblanc et al. 2016 in prep) at LATMOS. Validation of these studies will rely on in-situ observations in the coming decades. Neutral detection strongly depends on electron-impact ionization which via conventional cathode-sources, such as thermal filaments (heated up to 2000 K), may only produce the target ionization essential for energy-measurements with large power consumption. Carbon nanotubes (CNTs) however are ideal low-power, cold cathodes, when subject to moderate electric fields (E ~ 1 MV / m). We present our current device, a small CNT chip, of emission area 15 mm2, emitting electrons that pass through an anode grid and subsequent electrostatic analyzer. The device currently extracts hundreds of µAmperes with applied external voltages ~ -150 Volts, approaching minimum power consumption < 0.1 Watts. The 3D modeling of field effect electrons ionizing a standard influx of neutrals is shown, using the multiphysics suite COMSOL. To better anticipate the species an ideal in-situ spacecraft equipped with such an ionization source would observe, we discuss Europa's exosphere. Europa's environment is largely shaped by the Jovian plasma sputtering the icy regolith with heavy ions and electrons (keV < E < MeV), producing predominately molecular oxygen (Johnson et al. 2002).

  18. Radar signal propagation through the ionosphere of Europa

    Science.gov (United States)

    Grima, Cyril; Blankenship, Donald D.; Schroeder, Dustin M.

    2015-11-01

    We review the current state of knowledge of the Europan plasma environment, its effects on radio wave propagation, and its impact on the performance and design of future radar sounders for the exploration of Europa's ice crust. The Europan ionosphere is produced in two independently-rotating hemispheres by photo-ionization of the neutral exosphere and interaction with the Io plasma torus, respectively. This combination is responsible for temporal and longitudinal ionospheric heterogeneities not well constrained by observations. When Europa's ionosphere is active, the maximum cut-off frequency is 1 MHz at the surface. The main impacts on radar signal propagation are dispersive phase shift and Faraday rotation, both a function of the total electron content (up to 4×1015 m-2) and the Jovian magnetic field strength at Europa (~420 nT). The severity of these impacts decrease with increasing center frequency and increase with altitude, latitude, and bandwidth. The 9 MHz channels on the Radar for Icy Moons Exploration (RIME) and proposed Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) will be sensitive to the Europan ionosphere. For these or similar radar sounders, the ionospheric signal distortion from dispersive phase shift can be corrected with existing techniques, which would also enable the estimation of the total electron content below the spacecraft. At 9 MHz, the Faraday fading is not expected to exceed 6 dB under the worst conditions. At lower frequencies, any active or passive radio probing of the ice shell exploration would be limited to frequencies above 1-8 MHz (depending on survey configuration) below which Faraday rotation angle would lead to signal fading and detection ambiguity. Radar instruments could be sensitive to neutrals and electrons added in the exosphere from any plume activity if present.

  19. Looking Forward to Cassini's Proximal Orbits: the Innermost Radiation Belt of Saturn

    Science.gov (United States)

    Cooper, John F.; Kollmann, P.; Paranicas, C.; Mitchell, D. G.; Hedman, M. M.; Edgington, S. G.; Sittler, E. C.; Hartle, R. E.; Johnson, R. E.; Sturner, S. J.; Cassini Proximal Hazard Working Group

    2013-10-01

    The Cassini mission to Saturn will conclude with over twenty flybys of the equatorial gap region between Saturn's upper atmosphere and the inner D ring. This region at 62,000 - 65,000 kilometers from the center of Saturn is of comparable width to the inner Van Allen radiation belt of Earth and could contain Saturn's innermost belt of presently uncertain intensity and impact on the Cassini spacecraft. As first proposed by Cooper [BAAS 40(3), 460, 2008] this innermost belt could be populated to potentially very high intensities by protons and electrons from cosmic ray albedo neutron decay. The primary neutron source at high energies above 10 MeV would be from galactic cosmic ray interactions with the main rings of Saturn, but more recent work suggests a secondary source at lower energies from similar interactions with Saturn's upper atmosphere. At keV energies a third source from magnetospheric energetic neutral atom interactions with the exospheric gas extending through the gap region could be effective as observed earlier by Cassini. A fourth source includes eV - keV ions from low-energy neutral atom ejection out of the ring atmosphere. Ions from the ring ionosphere were also observed by Cassini. Since trapping lifetimes of keV - GeV protons due to radial diffusion in the gap region are projected to be extremely long, correspondingly high intensities could arise unless there was sufficient exospheric gas and ring material to reduce lifetimes far below the diffusion limit. Limits from new modeling are presented for the potential range of trapped particle intensities at MeV - GeV energies. Apart from the potential radiation and other hazards, this first exploration of the gap region will provide a fascinating conclusion to the Cassini mission.

  20. Titan's plasma environment during a magnetosheath excursion: Real-time scenarios for Cassini's T32 flyby from a hybrid simulation

    Directory of Open Access Journals (Sweden)

    S. Simon

    2009-02-01

    Full Text Available With a Saturnian magnetopause average stand-off distance of about 21 planetary radii, Titan spends most of its time inside the rotating magnetosphere of its parent planet. However, when Saturn's magnetosphere is compressed due to high solar wind dynamic pressure, Titan can cross Saturn's magnetopause in the subsolar region of its orbit and therefore to interact with the shocked solar wind plasma in Saturn's magnetosheath. This situation has been observed during the T32 flyby of the Cassini spacecraft on 13 June 2007. Until a few minutes before closest approach, Titan had been located inside the Saturnian magnetosphere. During the flyby, Titan encountered a sudden change in the direction and magnitude of the ambient magnetic field. The density of the ambient plasma also increased dramatically during the pass. Thus, the moon's exosphere and ionosphere were exposed to a sudden change in the upstream plasma conditions. The resulting reconfiguration of Titan's plasma tail has been studied in real-time by using a three-dimensional, multi-species hybrid simulation model. The hybrid approximation treats the electrons of the plasma as a massless, charge-neutralizing fluid, while ion dynamics are described by a kinetic approach. In the simulations, the magnetopause crossing is modeled by a sudden change of the upstream magnetic field vector as well as a modification of the upstream plasma composition. We present real-time simulation results, illustrating how Titan's induced magnetotail is reconfigured due to magnetic reconnection. The simulations allow to determine a characteristic time scale for the erosion of the original magnetic draping pattern that commences after Titan has crossed Saturn's magnetopause. Besides, the influence of the plasma composition in the magnetosheath on the reconfiguration process is discussed in detail. The question of whether the magnetopause crossing is likely to yield a detachment of Titan's exospheric tail from the

  1. Emirates Mars Ultraviolet Spectrometer (EMUS) Overview from the Emirates Mars Mission

    Science.gov (United States)

    Almatroushi, Hessa; Lootah, Fatma; Holsclaw, Greg; Deighan, Justin; Chaffin, Michael; Lillis, Robert; Fillingim, Matthew; England, Scott; AlMheiri, Suhail; Reed, Heather

    2017-04-01

    The Emirates Mars Ultraviolet Spectrometer (EMUS) instrument is one of three science instruments to be carried on board the Emirate Mars Mission (EMM), the "Hope Probe". EMM is a United Arab Emirates' (UAE) mission to Mars launching in 2020 to explore the dynamics in the Martian atmosphere globally, while sampling on both diurnal and seasonal timescales. The EMUS instrument is a far-ultraviolet imaging spectrograph that measures emissions in the spectral range 100-170 nm. Using spacecraft motion, it will build up two-dimensional far-ultraviolet images of the Martian disk and near-space environment at several important wavelengths: Lyman beta atomic hydrogen emission (102.6 nm), Lyman alpha atomic hydrogen emission (121.6 nm), atomic oxygen emission (130.4 nm and 135.6 nm), and carbon monoxide fourth positive group band emission (140 nm-170 nm). Radiances at these wavelengths will be used to derive the column abundance of atomic oxygen, and carbon monoxide in the Martian thermosphere, and the density of atomic oxygen and atomic hydrogen in the Martian exosphere both with spatial and sub-seasonal variability. EMUS consists of a single telescope mirror feeding a Rowland circle imaging spectrograph capable of selectable spectral resolution (1.3 nm, 1.8 nm, or 5 nm) with a photon-counting and locating detector (provided by the Space Sciences Laboratory at the University of California, Berkeley). The EMUS spatial resolution of less than 300km on the disk is sufficient to characterize spatial variability in the Martian thermosphere (100-200 km altitude) and exosphere (>200 km altitude). The instrument is jointly developed by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and Mohammed Bin Rashid Space Centre (MBRSC) in Dubai, UAE

  2. SPICAM on Mars Express: A 10 year in-depth survey of the Martian atmosphere

    Science.gov (United States)

    Montmessin, F.; Korablev, O.; Lefèvre, F.; Bertaux, J.-L.; Fedorova, A.; Trokhimovskiy, A.; Chaufray, J. Y.; Lacombe, G.; Reberac, A.; Maltagliati, L.; Willame, Y.; Guslyakova, S.; Gérard, J.-C.; Stiepen, A.; Fussen, D.; Mateshvili, N.; Määttänen, A.; Forget, F.; Witasse, O.; Leblanc, F.; Vandaele, A. C.; Marcq, E.; Sandel, B.; Gondet, B.; Schneider, N.; Chaffin, M.; Chapron, N.

    2017-11-01

    The SPICAM experiment onboard Mars Express has accumulated during the last decade a wealth of observations that has permitted a detailed characterization of the atmospheric composition and activity from the near-surface up to above the exosphere. The SPICAM climatology is one of the longest assembled to date by an instrument in orbit around Mars, offering the opportunity to study the fate of major volatile species in the Martian atmosphere over a multi-(Mars)year timeframe. With his dual ultraviolet (UV)-near Infrared channels, SPICAM observes spectral ranges encompassing signatures created by a variety atmospheric gases, from major (CO2) to trace species (H2O, O3). Here, we present a synthesis of the observations collected for water vapor, ozone, clouds and dust, carbon dioxide, exospheric hydrogen and airglows. The assembled climatology covers the MY 27-MY 31 period. However, the monitoring of UV-derived species was interrupted at the end of 2014 (MY30) due to failure of the UV channel. A SO2 detection attempt was undertaken, but proved unsuccessful from regional to global scales (with upper limit greater than already published ones). One particular conclusion that stands out from this overview work concerns the way the Martian atmosphere organizes an efficient mass transfer between the lower and the upper atmospheric reservoirs. This highway to space, as we name it, is best illustrated by water and hydrogen, both species having been monitored by SPICAM in their respective atmospheric reservoir. Coupling between the two appear to occur on seasonal timescales, much shorter than theoretical predictions.

  3. A steady-state model of the lunar ejecta cloud

    Science.gov (United States)

    Christou, Apostolos

    2014-05-01

    Every airless body in the solar system is surrounded by a cloud of ejecta produced by the impact of interplanetary meteoroids on its surface [1]. Such ``dust exospheres'' have been observed around the Galilean satellites of Jupiter [2,3]. The prospect of long-term robotic and human operations on the Moon by the US and other countries has rekindled interest on the subject [4]. This interest has culminated with the - currently ongoing - investigation of the Moon's dust exosphere by the LADEE spacecraft [5]. Here a model is presented of a ballistic, collisionless, steady state population of ejecta launched vertically at randomly distributed times and velocities and moving under constant gravity. Assuming a uniform distribution of launch times I derive closed form solutions for the probability density functions (pdfs) of the height distribution of particles and the distribution of their speeds in a rest frame both at the surface and at altitude. The treatment is then extended to particle motion with respect to a moving platform such as an orbiting spacecraft. These expressions are compared with numerical simulations under lunar surface gravity where the underlying ejection speed distribution is (a) uniform (b) a power law. I discuss the predictions of the model, its limitations, and how it can be validated against near-surface and orbital measurements.[1] Gault, D. Shoemaker, E.M., Moore, H.J., 1963, NASA TN-D 1767. [2] Kruger, H., Krivov, A.V., Hamilton, D. P., Grun, E., 1999, Nature, 399, 558. [3] Kruger, H., Krivov, A.V., Sremcevic, M., Grun, E., 2003, Icarus, 164, 170. [4] Grun, E., Horanyi, M., Sternovsky, Z., 2011, Planetary and Space Science, 59, 1672. [5] Elphic, R.C., Hine, B., Delory, G.T., Salute, J.S., Noble, S., Colaprete, A., Horanyi, M., Mahaffy, P., and the LADEE Science Team, 2014, LPSC XLV, LPI Contr. 1777, 2677.

  4. Influence of the solar EUV flux on the Martian plasma environment

    Directory of Open Access Journals (Sweden)

    R. Modolo

    2005-02-01

    Full Text Available The interaction of the solar wind with the Martian atmosphere and ionosphere is investigated by using three-dimensional, global and multi-species hybrid simulations. In the present work we focus on the influence of the solar EUV flux on the Martian plasma environment by comparing simulations done for conditions representative of the extrema of the solar cycle. The dynamics of four ionic species (H+, He++, O+, O2+, originating either from the solar wind or from the planetary plasma, is treated fully kinetically in the simulation model in order to characterize the distribution of each component of the plasma, both at solar maximum and at solar minimum. The solar EUV flux controls the ionization frequencies of the exospheric species, atomic hydrogen and oxygen, as well as the density, the temperature, and thus the extension of the exosphere. Ionization by photons and by electron impacts, and the main charge exchange reactions are self-consistently included in the simulation model. Simulation results are in reasonable agreement with the observations made by Phobos-2 and Mars Global Surveyor (MGS spacecraft: 1 the interaction creates a cavity, void of solar wind ions (H+, He++, which depends weakly upon the phase of the solar cycle, 2 the motional electric field of the solar wind flow creates strong asymmetries in the Martian environment, 3 the spatial distribution of the different components of the planetary plasma depends strongly upon the phase of the solar cycle. The fluxes of the escaping planetary ions are computed from the simulated data and results for solar maximum are compared with estimates based on the measurements made by experiments ASPERA and TAUS on board Phobos-2.

  5. Search for an evaporating ocean on the super-Earth HIP 116454b

    Science.gov (United States)

    Bourrier, Vincent

    2017-08-01

    The super-Earth HIP116454b was the first exoplanet detected by the K2 mission, in transit across a bright and nearby K1 dwarf (V=10.2, d=55 pc). The low density of the planet suggests it must have at least 30% water or a 0.5% H-He envelope. Given the strong XUV irradiation from the young (2 Gyr) host star, this H-He envelope should have been lost through evaporation in a few hundred millions year, suggesting that HIP 116454b likely contains a large mass fraction of water. The shallow transit depth makes difficult the search for water vapor in the lower atmosphere with HST/WFC3. The moderate orbital distance of this warm ( 700 K) planet favors the formation of a super-critical steam envelope, which should be promptly dissociated at high altitude by the XUV irradiation and become observable as hydrogen flowing within and beyond the Roche lobe. The host star is similar to HD 189733, host to an evaporating hot Jupiter, and numerical simulations of HIP116454b show that the hydrogen exosphere resulting from the dissociation of water is observable with HST/STIS at Ly-alpha. The detection of this exosphere would be the first signature of an evolved evaporating ocean on an extrasolar planet, as well as the first validation of internal structure models of exoplanets in this mass regime. It would also determine how to best search for water in the lower atmosphere of HIP116454b with the JWST. A non-detection of escaping hydrogen, as with 55 Cnc e and HD 97658b, would bring useful constraints on the nature of the planetary atmosphere, the evolutionary path of close-in super-Earths, and the progenitors of the rocky evaporation remnants detected by Kepler.

  6. How Tiny Collisions Shape Mercury

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    If space rocks are unpleasant to encounter, space dust isnt much better. Mercurys cratered surface tells of billions of years of meteoroid impacts but its thin atmosphere is what reveals its collisional history with smaller impactors. Now new research is providing a better understanding of what were seeing.Micrometeoroids Ho!The inner solar system is bombarded by micrometeoroids, tiny particles of dust (on the scale of a tenth of a millimeter) emitted by asteroids and comets as they make their closest approach to the Sun. This dust doesnt penetrateEarths layers of atmosphere, but the innermost planet of our solar system, Mercury, doesnt have this convenient cushioning.Just as Mercury is affected by the impacts of large meteoroids, its also shaped by the many smaller-scale impacts it experiences. These tiny collisions are thought to vaporize atoms and molecules from the planets surface, which quickly dissociate. This process adds metals to Mercurys exosphere, the planets extremely tenuous atmosphere.Modeling PopulationsDistribution of the directions from which meteoroids originate before impacting Mercurys surface, as averaged over its entire orbit. Local time of 12 hr corresponds to the Sun-facing side. A significant asymmetry is seen between the dawn (6 hrs) and dusk (18 hrs) rates. [Pokorn et al. 2017]The metal distribution in the exosphere provides a way for us to measure the effect of micrometeoroid impacts on Mercury but this only works if we have accurate models of the process. A team of scientists led by Petr Pokorn (The Catholic University of America and NASA Goddard SFC) has now worked to improve our picture of micrometeoroid impact vaporization on Mercury.Pokorn and collaborators argue that two meteoroid populations Jupiter-family comets (short-period) and Halley-type comets (long-period) contribute the dust for the majority of micrometeoroid impacts on Mercury. The authors model the dynamics and evolution of these two populations, reproducing the

  7. MESSENGER: Exploring the Innermost Planet

    Science.gov (United States)

    Solomon, S. C.

    2011-12-01

    One of Earth's closest planetary neighbors, Mercury remained comparatively unexplored for the more than three decades that followed the three flybys of the innermost planet by the Mariner 10 spacecraft in 1974-75. Mariner 10 imaged 45% of Mercury's surface at about 1 km/pixel average resolution, confirmed Mercury's anomalously high bulk density and implied large fractional core size, discovered Mercury's internal magnetic field, documented that H and He are present in the planet's tenuous exosphere, and made the first exploration of Mercury's magnetosphere and solar wind environment. Ground-based astronomers later reported Na, K, and Ca in Mercury's exosphere; the presence of deposits in the floors of polar craters having radar characteristics best matched by water ice; and strong evidence from the planet's forced libration amplitude that Mercury has a fluid outer core. Spacecraft exploration of Mercury resumed with the selection for flight, under NASA's Discovery Program, of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. Launched in 2004, MESSENGER flew by the innermost planet three times in 2008-2009 en route to becoming the first spacecraft to orbit Mercury in March of this year. MESSENGER's first chemical remote sensing measurements of Mercury's surface indicate that the planet's bulk silicate fraction differs from those of the other inner planets, with a low-Fe surface composition intermediate between basalts and ultramafic rocks and best matched among terrestrial rocks by komatiites. Moreover, surface materials are richer in the volatile constituents S and K than predicted by most planetary formation models. Global image mosaics and targeted high-resolution images (to resolutions of 10 m/pixel) reveal that Mercury experienced globally extensive volcanism, including large expanses of plains emplaced as flood lavas and widespread examples of pyroclastic deposits likely emplaced during explosive eruptions of volatile

  8. Plasma IMS Composition Measurements for Europa and the Other Galilean Moons

    Science.gov (United States)

    Sittler, Edward; Cooper, John; Hartle, Richard; Lipatov, Alexander; Mahaffy, Paul; Paterson, William; Pachalidis, Nick; Coplan, Mike; Cassidy, Tim

    2010-01-01

    sputtering of the surfaces of Europa and Ganymede has been shown to be representative of the surface composition. Level 2 science on surface geology and composition can then be further enhanced by addition of the following: 3D Ion Neutral Mass Spectrometer (INNS), 3D plasma electron spectrometer (ELS), and hot plasma energetic particle instrument. The measurement approach is to alternate between times measuring pickup ions and times measuring plasma and magnetic field parameters along the spacecraft trajectory. By measuring the pickup ion energy, arrival direction and mass-per-charge, the ion can be traced back along the ejection trajectory to the approximate area of origin if the 3-D electric field and magnetic field are known. In situ observations of plasma flow velocities and vector magnetic fields can be used to determine the local convective electric field (E = -VXB) along the spacecraft trajectory. By combining this information with models of the magnetospheric interaction with Europa, one can generate 3D maps of the electric and magnetic field and compute the trajectories of the pickup ions back to the surface or exospheric points of origin. In the case of Ganymede there is the additional complexity of its own internal dipole magnetic field, while Io's volcanic activity introduces the complexity of a highly structured denser atmosphere. Callisto with its less globally extended exosphere will have a simpler interaction than for Europa (i.e., more like our moon). We will discuss these differences in light of the above proposed technique. Finally, the INNS observations and neutral exosphere models are needed to estimate production rates of pickup ions. The hot plasma measurements are needed to correct for sputtering rates which can be time dependent and electron plasma observations for electron impact ionization rates. Instrument characteristics, field-of-view requirements, modes of operation and effects of radiation on instrument functionality will be discussed.

  9. Mercury after three MESSENGER flybys

    Science.gov (United States)

    Solomon, Sean C.; Bedini, Peter D.; Anderson, Brian J.; Prockter, Louise M.; Blewett, David T.; Evans, Larry G.; Gold, Robert E.; Murchie, Scott L.; Nittler, Larry R.; Phillips, Roger J.; Zuber, Maria T.

    The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) space-craft, developed under NASA's Discovery Program, is the first space probe to visit the planet Mercury in more than 30 years. MESSENGER flew by the innermost planet twice in 2008 and once last fall. The flybys confirmed that Mercury's internal magnetic field is dominantly dipolar, with a vector moment closely aligned with the spin axis. MESSENGER detected mag-nesium in Mercury's exosphere, demonstrated that Mercury's anti-sunward neutral tail contains multiple species, and revealed that the distributions of sodium, calcium, and magnesium in the exosphere and tail vary differently with latitude, time of day, and Mercury's position in or-bit, signatures of multiple source processes. MESSENGER's laser altimeter showed that the equatorial topographic relief of Mercury exceeds 5 km, revealed an equatorial ellipticity aligned with the ellipticity in Mercury's gravitational potential, and documented the form of numer-ous impact craters and fault scarps. MESSENGER images provided evidence for widespread volcanism, and candidate sites for volcanic centers were identified. In addition, newly imaged lobate scarps and other tectonic landforms support the hypothesis that Mercury contracted globally in response to interior cooling. The ˜1500-km-diameter Caloris basin, viewed in its entirety for the first time by MESSENGER, was the focus for concentrations of volcanic cen-ters, some with evidence of pyroclastic deposits, and widespread contractional and extensional deformation; smooth plains interior and exterior to the basin are demonstrably younger than the basin-forming event. The ˜700-km-diameter Rembrandt basin, less volcanically infilled than Caloris, was likewise a focus for concentrated magmatic and deformational activity. A ˜290-km-diameter basin contains interior plains that are among the youngest volcanic material on the planet. The nearly global observations of Mercury surface units

  10. Mpo - the Bepicolombo Mercury Planetary Orbiter.

    Science.gov (United States)

    Benkhoff, J.

    2008-09-01

    Introduction: BepiColombo is an interdisciplinary mission to explore the planet Mercury through a partnership between ESA and Japan's Aerospace Exploration Agency (JAXA). From their dedicated orbits two spacecrafts, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), will be studying the planet and its environment Both orbiter will be launched together on an ARIANE 5. The launch is foreseen for Summer 2014 with arrival in Summer 2020. Solar electric propulsion will be used for the journey to Mercury. In November 2004, the BepiColombo scientific payload has been officially approved. Payload of BepiColombo: The MPO scientific payload comprises eleven instruments/instrument packages; the MMO scientific payload consists of five instruments/instrument packages. Together, the scientific payload of both spacecraft will provide the detailed information necessary to understand Mercury and its magnetospheric environment and to find clues to the origin and evolution of a planet close to its parent star. The MPO will focus on a global characterization of Mercury through the investigation of its interior, surface, exosphere and magnetosphere. In addition, it will be testing Einstein's theory of general relativity. Major effort was put into optimizing the scientific return by defining the payload complement such that individual measurements can be interrelated and complement each other. A detailed overview of the status of BepiColombo will be given with special emphasis on the MPO and its payload complement. BepiColombo factsheet BepiColombo is Europe's first mission to Mercury, the innermost planet of the Solar System, and ESA's first science mission in collaboration with Japan. A satellite 'duo' - consisting of an orbiter for planetary investigation and one for magnetospheric studies - Bepi- Colombo will reach Mercury after a six-year journey towards the inner Solar System, to make the most extensive and detailed study of the planet ever performed

  11. Emirates Mars Mission (EMM) Overview

    Science.gov (United States)

    Sharaf, Omran; Amiri, Sarah; AlMheiri, Suhail; Alrais, Adnan; Wali, Mohammad; AlShamsi, Zakareyya; AlQasim, Ibrahim; AlHarmoodi, Khuloud; AlTeneiji, Nour; Almatroushi, Hessa; AlShamsi, Maryam; AlAwadhi, Mohsen; McGrath, Michael; Withnell, Pete; Ferrington, Nicolas; Reed, Heather; Landin, Brett; Ryan, Sean; Pramann, Brian

    2017-04-01

    United Arab Emirates (UAE) has entered the space exploration race with the announcement of Emirates Mars Mission (EMM), the first Arab Islamic mission to another planet, in 2014. Through this mission, UAE is to send an unmanned probe, called Hope probe, to be launched in summer 2020 and reach Mars by 2021 to coincide with UAE's 50th anniversary. Through a sequence of subsequent maneuvers, the spacecraft will enter a large science orbit that has a periapsis altitude of 20,000 km, an apoapsis altitude of 43,000 km, and an inclination of 25 degrees. The mission is designed to (1) characterize the state of the Martian lower atmosphere on global scales and its geographic, diurnal and seasonal variability, (2) correlate rates of thermal and photochemical atmospheric escape with conditions in the collisional Martian atmosphere, and (3) characterize the spatial structure and variability of key constituents in the Martian exosphere. These objectives will be met by four investigations with diurnal variability on sub-seasonal timescales which are (1) determining the three-dimensional thermal state of the lower atmosphere, (2) determining the geographic and diurnal distribution of key constituents in the lower atmosphere, (3) determining the abundance and spatial variability of key neutral species in the thermosphere, and (4) determining the three-dimensional structure and variability of key species in the exosphere. EMM will collect these information about the Mars atmospheric circulation and connections through a combination of three distinct instruments that image Mars in the visible, thermal infrared and ultraviolet wavelengths and they are the Emirates eXploration Imager (EXI), the Emirates Mars InfraRed Spectrometer (EMIRS), and the EMM Mars Ultraviolet Spectrometer (EMUS). EMM has passed its Mission Concept Review (MCR), System Requirements Review (SRR), System Design Review (SDR), and Preliminary Design Review (PDR) phases. The mission is led by Emiratis from Mohammed

  12. X-Ray Emission in the Heliosphere: Ion-Neutral Collisions as a Plasma Diagnostic

    Science.gov (United States)

    Cravens, Tom; Sibeck, David; Collier, MIchael

    2015-04-01

    The solar corona is the most powerful source of x-rays in the solar system but x-ray emission has also been observed from planets, including the Earth and Jupiter, from the Moon, from comets, and from interstellar gas entering the heliosphere. Astrophysical x-ray emission primarily comes from hot plasmas, such as in the million degree solar corona. The gas and plasma in planetary atmospheres are rather cold and the x-ray emission is driven by solar radiation and/or the solar wind. For example, x-rays from Venus come from the scattering and K-shell fluorescence of solar x-rays from the neutral atmosphere. Auroral x-ray emission at Earth and Jupiter is produced by energetic electron and ion precipitation from the magnetospheres into the atmospheres. Cometary and heliospheric x-ray emission is caused by charge transfer of high charge state solar wind ions (e.g., O7+, C6+,…) with neutral hydrogen and helium.An important source of solar system x-rays is the solar wind charge exchange (SWCX) mechanism. The solar wind originates in the hot solar corona and species heavier than helium (comprising about 0.1% of the gas) are highly-charged (e.g., O7+, C6+, Fe12+,….). Such ions undergo charge transfer collisions when they encounter neutral gas (e.g., cometary or interstellar gas or the Earth’s geocoronal hydrogen). The product ions are in highly-excited states and, subsequently, emit soft x-ray photons. The SWCX mechanism can explain the observed cometary x-ray emission and can also explain part of the soft x-ray background (the other part of which originates in the hot interstellar medium).The Earth has an extensive hot hydrogen exosphere, or geocorona, that is visible in scattered solar Lyman alpha. X-ray emission is produced in the magnetosheath due to the SWCX mechanism as the solar wind interacts with the exospheric gas. The most intense x-ray emission comes from the subsolar sheath region and from the cusp regions. Imaging of this emission by a spacecraft located

  13. Cassini's Grand Finale and Recent Science Highlights

    Science.gov (United States)

    Spilker, Linda J.

    2017-06-01

    After almost 13 years in Saturn orbit, the Cassini-Huygens mission has entered its final year of data collection. Cassini will return its final bits of unique data on 15 September 2017 as it plunges into Saturn’s atmosphere, vaporizing and satisfying planetary protection requirements.Since early 2016 Cassini’s orbital inclination was slowly increased towards its final inclination. In November Cassini transitioned to a series of 20 orbits with periapses just outside Saturn's F ring that included some of the closest flybys of the tiny ring moons and excellent views of the F ring and outer A ring.Cassini's final close flyby of Titan in April 2017 propelled it across Saturn’s main rings and into its final orbits. Cassini's Grand Finale began in April 2017 and is comprised of 22 orbits at an inclination of 63 degrees. Cassini is repeatedly diving between the innermost ring and Saturn's upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. It is the first spacecraft to explore this region.These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in situ sampling of the ring particles' composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on Saturn's interior structure and mass distribution in the rings. Probing the magnetic field will give insight into the nature of the magnetic dynamo and the true rotation rate of Saturn's interior. The ion and neutral mass spectrometer will sniff the exosphere and upper atmosphere and examine water-based molecules originating from the rings. The cosmic dust analyzer will sample particle composition from different parts of the main rings.Recent science highlights and science objectives from Cassini’s final orbits will be discussed.This work was carried out in part at the Jet Propulsion Laboratory, California

  14. Observing Planets and Small Bodies in Sputtered High Energy Atom (SHEA) Fluxes

    Science.gov (United States)

    Milillo, A.; Orsini, S.; Hsieh, K. C.; Baragiola, R.; Fama, M.; Johnson, R.; Mura, A.; Plainaki, Ch.; Sarantos, M.; Cassidy, T. A.; hide

    2012-01-01

    The evolution of the surfaces of bodies unprotected by either strong magnetic fields or thick atmospheres in the Solar System is caused by various processes, induced by photons, energetic ions and micrometeoroids. Among these processes, the continuous bombardment of the solar wind or energetic magnetospheric ions onto the bodies may significantly affect their surfaces, with implications for their evolution. Ion precipitation produces neutral atom releases into the exosphere through ion sputtering, with velocity distribution extending well above the particle escape limits. We refer to this component of the surface ejecta as sputtered high-energy atoms (SHEA). The use of ion sputtering emission for studying the interaction of exposed bodies (EB) with ion environments is described here. Remote sensing in SHEA in the vicinity of EB can provide mapping of the bodies exposed to ion sputtering action with temporal and mass resolution. This paper speculates on the possibility of performing remote sensing of exposed bodies using SHEA The evolution of the surfaces of bodies unprotected by either strong magnetic fields or thick atmospheres in the Solar System is caused by various processes, induced by photons, energetic ions and micrometeoroids. Among these processes, the continuous bombardment of the solar wind or energetic magnetospheric ions onto the bodies may significantly affect their surfaces, with implications for their evolution. Ion precipitation produces neutral atom releases into the exosphere through ion sputtering, with velocity distribution extending well above the particle escape limits. We refer to this component of the surface ejecta as sputtered high-energy atoms (SHEA). The use of ion sputtering emission for studying the interaction of exposed bodies (EB) with ion environments is described here. Remote sensing in SHEA in the vicinity of EB can provide mapping of the bodies exposed to ion sputtering action with temporal and mass resolution. This paper

  15. Titan's plasma environment during a magnetosheath excursion: Real-time scenarios for Cassini's T32 flyby from a hybrid simulation

    Directory of Open Access Journals (Sweden)

    S. Simon

    2009-02-01

    Full Text Available With a Saturnian magnetopause average stand-off distance of about 21 planetary radii, Titan spends most of its time inside the rotating magnetosphere of its parent planet. However, when Saturn's magnetosphere is compressed due to high solar wind dynamic pressure, Titan can cross Saturn's magnetopause in the subsolar region of its orbit and therefore to interact with the shocked solar wind plasma in Saturn's magnetosheath. This situation has been observed during the T32 flyby of the Cassini spacecraft on 13 June 2007. Until a few minutes before closest approach, Titan had been located inside the Saturnian magnetosphere. During the flyby, Titan encountered a sudden change in the direction and magnitude of the ambient magnetic field. The density of the ambient plasma also increased dramatically during the pass. Thus, the moon's exosphere and ionosphere were exposed to a sudden change in the upstream plasma conditions. The resulting reconfiguration of Titan's plasma tail has been studied in real-time by using a three-dimensional, multi-species hybrid simulation model. The hybrid approximation treats the electrons of the plasma as a massless, charge-neutralizing fluid, while ion dynamics are described by a kinetic approach. In the simulations, the magnetopause crossing is modeled by a sudden change of the upstream magnetic field vector as well as a modification of the upstream plasma composition. We present real-time simulation results, illustrating how Titan's induced magnetotail is reconfigured due to magnetic reconnection. The simulations allow to determine a characteristic time scale for the erosion of the original magnetic draping pattern that commences after Titan has crossed Saturn's magnetopause. Besides, the influence of the plasma composition in the magnetosheath on the reconfiguration process is discussed in detail. The question of whether the magnetopause crossing is likely to yield a detachment of Titan

  16. Joint Europa Mission (JEM) : A multi-scale study of Europa to characterize its habitability and search for life.

    Science.gov (United States)

    Blanc, Michel; Prieto Ballesteros, Olga; Andre, Nicolas; Cooper, John F.

    2017-04-01

    Europa is the closest and probably the most promising target to perform a comprehensive characterization of habitability and search for extant life. We propose that NASA and ESA join forces to design an ambitious planetary mission we call JEM (for Joint Europa Mission) to reach this objective. JEM will be assigned the following overarching goal: Understand Europa as a complex system responding to Jupiter system forcing, characterize the habitability of its potential biosphere, and search for life in its surface, sub-surface and exosphere. Our observation strategy to address these goals will combine three scientific measurement sequences: measurements on a high-latitude, low-latitude Europan orbit providing a continuous and global mapping of planetary fields (magnetic and gravity) and of the neutral and charged environment during a period of three months; in-situ measurements at the surface, using a soft lander operating during 35 days, to search for bio-signatures at the surface and sub-surface and operate a geophysical station; measurements of the chemical composition of the very low exosphere and plumes in search for biomolecules. The implementation of these three observation sequences will rest on the combination of two science platforms equipped with the most advanced instrumentation: a soft lander to perform all scientific measurements at the surface and sub-surface at a selected landing site, and a carrier/relay/orbiter to perform the orbital survey and descent sequences. In this concept, the orbiter will perform science operations during the relay phase on a carefully optimized halo orbit of the Europa-Jupiter system before moving to its final Europan orbit. The design of both orbiter and lander instruments will have to accommodate the very challenging radiation mitigation and Planetary Protection issues. The proposed lander science platform is composed of a geophysical station and of two complementary astrobiology facilities dedicated to bio

  17. Mercury after the Third MESSENGER Flyby

    Science.gov (United States)

    Solomon, S. C.; McNutt, R. L.; Bedini, P. D.; Anderson, B. J.; Evans, L. G.; Gold, R. E.; Head, J. W.; Krimigis, S. M.; Murchie, S. L.; Nittler, L.; Phillips, R. J.; Slavin, J. A.; Zuber, M. T.

    2009-12-01

    MESSENGER is the first spacecraft to visit the planet Mercury in more than 30 years. Images from MESSENGER’s first Mercury flyby, in January 2008, provided evidence for widespread volcanism, and candidate sites for volcanic centers were identified. Newly imaged lobate scarps and other tectonic landforms confirmed that Mercury contracted globally in response to interior cooling. The ~1500-km-diameter Caloris basin, viewed in its entirety for the first time by MESSENGER, was the focus for concentrations of volcanic centers, some with evidence of pyroclastic deposits, and widespread contractional and extensional deformation. Smooth plains interior and exterior to the basin are demonstrably younger than the basin-forming event. Reflectance spectra of Mercury’s surface showed no evidence for FeO in surface silicates. Reflectance and color imaging observations provided fresh support for earlier inferences that Mercury’s surface material consists dominantly of iron-poor, calcium-magnesium silicates with an admixture of spectrally neutral opaque minerals. MESSENGER’s second flyby, in October 2008, revealed the presence of neutral Mg and Ca in Mercury’s anti-sunward tail and documented strongly differing distributions of Mg, Ca, and Na in the nightside exosphere, the result of different combinations of time-variable source, transfer, and loss processes. A southward interplanetary magnetic field (IMF) was accompanied by multiple indications of magnetic reconnection at rates ~10 times typical at Earth; in combination with the more quiescent conditions under northward IMF seen during the first flyby, the results indicate that Mercury’s magnetosphere is more responsive to IMF direction than those of other planets. The internal magnetic field is dominantly dipolar with a vector moment closely aligned with the spin axis. The nearly global observations of Mercury surface units distinguishable by color and composition enforce the importance of the largely volcanic

  18. Ion cyclotron waves at unmagnetized bodies: a comparison of Mars, Venus and Titan

    Science.gov (United States)

    Wei, H.; Russell, C. T.; Cowee, M.; Blanco-Cano, X.; Zhang, T.; Dougherty, M. K.

    2009-12-01

    Mars, Venus and Titan do not have appreciable global magnetic fields. Their high-altitude neutral atmospheres are not shielded from being lost to the solar wind and the Saturnian magnetosphere. When the atmospheric hydrogen atoms of Mars and Venus are ionized and picked up by the solar wind, proton cyclotron waves are created from the free energy of the ring-beam distribution of the pick-up ions. At Mars, proton cyclotron waves observed by Mars Global Surveyor extend from the magnetosheath to over 12 Mars radii, with intermittent occurrence and amplitudes slowly varying with distance. The wave occurrence pattern indicates a disk-shaped hydrogen exosphere of Mars with asymmetry in the direction of the interplanetary electric field. Fast neutrals produced by neutralization of the pickup ions can travel across fieldlines to distant regions where they get re-ionized and produce waves far downstream. Thus the top of Mars exosphere extends in a disk to high altitude, with its orientation controlled by the interplanetary magnetic field. At Venus, plasma waves having properties similar to ion cyclotron waves are observed in the solar wind around the planet by Venus Express, with wave frequencies that range from 0.2 to 5.9 times of the proton gyrofrequency. Statistical study shows that the waves with frequency higher than 1.5 times the proton gyrofrequency are not generated locally and are similar to the waves observed at 0.3 AU and 1 AU which appear to be created near the Sun and convected outward with the solar wind. The rest of the waves are mostly magnetically connected to the bow shock, so they are probably generated by particles backstreaming from the shock and propagate out further from the foreshock. At Titan, ion cyclotron waves are not observed although wave generation is expected due to the large pickup rate of hydrocarbon ions at high altitude of Titan. We attempt to understand the lack of ion cyclotron waves at Titan using hybrid simulations. Studying and

  19. 3-D-geocoronal hydrogen density derived from TWINS Ly-α-data

    Directory of Open Access Journals (Sweden)

    J. H. Zoennchen

    2010-06-01

    Full Text Available Based on Ly-α-line-of-sight measurements taken with two Ly-α detectors onboard of the satellite TWINS1 (Two Wide-angle Imaging Neutral-atom Spectrometers density profiles of the exospheric, neutral geocoronal hydrogen were derived for the time period between summer solstice and fall equinox 2008. With the help of specifically developed inversion programs from Ly-α line of sight intensities the three-dimensional density structure of the geocoronal hydrogen at geocentric distances r>3 RE could be derived for the period mentioned characterized by very low solar 10.7 cm radiofluxes of ≈65–70 [10−22 W m−2 Hz−1]. The time-variable, solar "line-centered"-Ly-α-flux was extracted on the basis of daily (terrestrial NGDC 10.7 cm radioflux data using the models from Barth et al. (1990 and Vidal-Madjar (1975. The results for the geocoronal H-densities are compared here both with theoretical calculations based on a Monte-Carlo model by Hodges (1994 and with density profiles obtained with the Geocoronal Imager (GEO by Østgaard and Mende (2003. In our results we find a remarkably more pronounced day-/night-side asymmetry which clearly hints to the existence of a hydrogen geotail (i.e. a tail structure with comparatively higher hydrogen densities on the night side of the earth for geocenctric distances >4 RE, and a only weakly pronounced polar depletion. These unexpected features we try to explain by new models in the near future. The derived 3-D-H-density structures are able to explain the line-of-sight (LOS dependent Ly-α intensity variations for all LOS seen up to now with TWINS-LAD. The presented results are valid for the region with geocentric distances 3 REexosphere with respect to resonant Ly-α-scattering allowing the use of single scattering calculations.

  20. Strong H I Lyman-α variations from an 11 Gyr-old host star: a planetary origin?

    Science.gov (United States)

    Bourrier, V.; Ehrenreich, D.; Allart, R.; Wyttenbach, A.; Semaan, T.; Astudillo-Defru, N.; Gracia-Berná, A.; Lovis, C.; Pepe, F.; Thomas, N.; Udry, S.

    2017-06-01

    Kepler-444 provides a unique opportunity to probe the atmospheric composition and evolution of a compact system of exoplanets smaller than the Earth. Five planets transit this bright K star at close orbital distances, but they are too small for their putative lower atmosphere to be probed at optical/infrared wavelengths. We used the Space Telescope Imaging Spectrograph instrument on board the Hubble Space Telescope to search for the signature of the planet's upper atmospheres at six independent epochs in the Lyman-α line. We detect significant flux variations during the transits of both Kepler-444 e and f ( 20%), and also at a time when none of the known planets was transiting ( 40%). Variability in the transition region and corona of the host star might be the source of these variations. Yet, their amplitude over short timescales ( 2-3 h) is surprisingly strong for this old (11.2 ± 1.0 Gyr) and apparently quiet main-sequence star. Alternatively, we show that the in-transit variations could be explained by absorption from neutral hydrogen exospheres trailing the two outer planets (Kepler-444 e and f). They would have to contain substantial amounts of water to replenish hydrogen exospheres such as these, which would reveal them to be the first confirmed ocean planets. The out-of-transit variations, however, would require the presence of an as-yet-undetected Kepler-444 g at larger orbital distance, casting doubt on the planetary origin scenario. Using HARPS-N observations in the sodium doublet, we derived the properties of two interstellar medium clouds along the line of sight toward Kepler-444. This allowed us to reconstruct the stellar Lyman-α line profile and to estimate the extreme-UV (XUV) irradiation from the star, which would still allow for a moderate mass loss from the outer planets after 11.2 Gyr. Follow-up of the system at XUV wavelengths will be required to assess this tantalizing possibility.

  1. LADEE UVS Observations of Atoms and Dust in the Lunar Tail

    Science.gov (United States)

    Wooden, Diane H.; Colaprete, Anthony; Cook, Amanda M.; Shirley, Mark H.; Vargo, Kara E.; Elphic, Richard C.; Stubbs, Timothy J.; Glenar, David A.

    2014-11-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) was a lunar orbiter launched in September 2013 that investigated the composition and temporal variation of the tenuous lunar exosphere and dust environment. A major goal of the mission was to characterize the dust exosphere prior to future lunar exploration activities, which may alter the lunar environment. The Ultraviolet/Visible Spectrometer (UVS) onboard LADEE addresses this goal, utilizing two sets of optics: a limb-viewing telescope, and a solar-viewing telescope (Colaprete et al. 2014a). We report on spectroscopic 280-820 nm) observations viewing down the lunar wake or along the ‘lunar tail’ from lunar orbit. Prior ground-based studies have observed the emission from neutral sodium atoms extended along the lunar tail, so often this region is referred to as the lunar sodium tail (e.g., Smith et al. 1999, Wilson et al. 1999).UVS measurements were made on the dark side of the moon, with the UVS limb-viewing telescope pointed outward in the direction of the Moon’s wake (almost anti-sun), during different lunar phases. These UVS observation activities sample a long column and allow the characterization of scattered light from dust and emission lines from atoms in the lunar tail (Colaprete et al. 2014b). Observations in this UVS configuration show the largest excess of scattered blue light in our data set, indicative of the presence of small dust grains in the tail. Once lofted (e.g., Stubbs et al. 2006), nanoparticles may become charged and picked up by the solar wind, similar to the phenomena witnessed above Enceladus’s northern hemisphere (Farrell et al. 2012) or by the STEREO/WAVES instrument while close to Earth’s orbit (Meyer-Vernet et al 2009). The UVS data show that small dust grains as well as atoms become entrained in the lunar tail. References:Colaprete, A. et al. (2014a), Space Sci. Rev., submittedColaprete, A. et al. (2014b), SSERVI Exploration Forum, http://nesf2014.arc

  2. Exoplanets as probes of the winds of host stars: the case of the M dwarf GJ 436

    Science.gov (United States)

    Vidotto, A. A.; Bourrier, V.

    2017-10-01

    Winds of cool dwarfs are difficult to observe, with only a few M dwarfs presenting observationally derived mass-loss rates (\\dot{M}), which span several orders of magnitude. Close-in exoplanets are conveniently positioned in the inner regions of stellar winds and can, thus, be used to probe the otherwise-unobservable local properties of their host-stars' winds. Here, we use local stellar wind characteristics observationally derived in the studies of atmospheric evaporation of the warm-neptune GJ 436b to derive the global characteristics of the wind of its M-dwarf host. Using an isothermal wind model, we constrain the stellar wind temperature to be in the range (0.36-0.43) MK, with \\dot{M}=(0.5-2.5) × 10^{-15} M_{⊙} yr^{-1}. By computing the pressure balance between the stellar wind and the interstellar medium, we derive the size of the astrophere of GJ 436 to be around 25 au, significantly more compact than the heliosphere. We demonstrate in this paper that transmission spectroscopy, coupled to planetary atmospheric evaporation and stellar wind models, can be a useful tool for constraining the large-scale wind structure of planet-hosting stars. Extending our approach to future planetary systems discoveries will open new perspectives for the combined characterization of planetary exospheres and winds of cool dwarf stars.

  3. Overview of the LADEE Ultraviolet-visible Spectrometer: Design, Performance and Planned Operations

    Science.gov (United States)

    Colaprete, A.; Elphic, R. C.; Landis, D.; Karcz, J.; Osetinsky, L.; Shirley, M.; Vargo, K.; Wooden, D.

    2013-01-01

    The Lunar Atmosphere and Dust Environment Explorer (LADEE) is an orbital lunar science mission currently under development to address the goals of the 2003 National Research Council decadal survey, the Lunar Exploration Analysis Group Roadmap, and the "Scientific Context for Exploration of the Moon" (SCEM) report, and has been recommended for execution by the 2011 Planetary Missions Decadal Survey. The mission s focus is to study the pristine state of the lunar atmosphere and dust environment prior to possible lunar exploration activities by countries, including the United States, China, India, and Japan, among others. Activity on the lunar surface has the potential of altering the tenuous lunar atmosphere, but changing the type and concentration of gases in the atmosphere. Before these activities occur it is important to make measurements of the current lunar atmosphere in its unmodified state. LADEE will determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. It will monitor variations in known gases, such as sodium, potassium, argon and helium, and will search for other, as-yet-undetected gases of both lunar and extra-lunar origin. LADEE will also determine whether dust is present in the lunar exosphere, and reveal the processes that contribute to its sources and variability. Launch is planned for August, 2013.

  4. Quantitative understanding of the cycles of oxidized and reduced sulfur on Venus

    Science.gov (United States)

    Yung, Yuk L.

    1994-01-01

    The evolution of the Venus atmosphere is determined by the supply of gases from the interior of the planet and outer space, and by the loss of particles to space over time. In particular, questions pertaining to the initial inventory of water and the current and past rates of outgassing can be addressed by studying the loss rates of H, D, He3 and He4. The photochemistry of the H2SO4 clouds may also have played an important role in regulating the amount of water above the cloud tops, and hence limit the rate of escape of hydrogen from the planet. Thus the problems of evolution and chemistry are intimately related. In our proposal the principal tasks we undertook to advance our understanding of the origin and evolution of water on Venus included: (1) escape of light atoms from Venus and (2) develop a photochemical model of sulfate formation. In the last two years we have made progress on Task 1 regarding how light atoms can escape from the exosphere of Venus with the development of a Monte Carlo program and in Task 2 have developed a thorough update on the SO2 photochemistry that had been previously carried out.

  5. Solar-Storm/Lunar Atmosphere Model (SSLAM): An overview of the effort and description of the driving storm environment

    Science.gov (United States)

    Farrell, W. M.; Halekas, J. S.; Killen, R. M.; Delory, G. T.; Gross, N.; Bleacher, L. V.; Krauss-Varben, D.; Travnicek, P.; Hurley, D.; Stubbs, T. J.; Zimmerman, M. I.; Jackson, T. L.

    2012-10-01

    On 29 April 1998, a coronal mass ejection (CME) was emitted from the Sun that had a significant impact at Earth. The terrestrial magnetosphere became more electrically active during the storm passage. Less explored is the effect of such a storm on an exposed rocky body like our Moon. The solar-storm/lunar atmosphere modeling effort (SSLAM) brings together surface interactions, exosphere, plasma, and surface charging models all run with a common driver - the solar storm and CME passage occurring from 1 to 4 May 1998. We present herein an expanded discussion on the solar driver during the 1-4 May 1998 period that included the passage of an intense coronal mass ejection (CME) that had >10 times the solar wind density and had a compositional component of He++ that exceeded 20%. During this time, the plasma mass flux to the exposed lunar surface increased by over 20 times compared to the nominal solar wind, to a value near 10-13 kg/m2-s. Over a two day CME passage by the Moon, this amount approaches 300 tons of added mass to the Moon in the form of individual proton and helium ions. Such an increase in ion flux should have a profound impact on sputtering loss rates from the surface, since this process scales as the mass, energy, and charge state of the incident ion. Associated loss processes were addressed by SSLAM and will be discussed herein.

  6. Helium Production of Prompt Neutrinos on the Moon

    Science.gov (United States)

    Andersen, V.; Wilson, T. L.; Pinsky, L. S.

    2004-01-01

    The subject of conducting fundamental physics and astronomy experiments on the lunar surface continues to be of interest in the planetary science community. Such an inquiry necessarily requires an analysis of the backscatter albedos produced by Galactic cosmic rays (GCRs) when they directly impact the lunar regolith. Unlike the Earth, this happens because the Moon has only a tenuous exosphere. Such secondary radiation constitutes a background that obscures and interferes with measurements conducted in the normal sense of laboratory physics on Earth. Our previous investigations using recent enhancements in the Monte Carlo program known as FLUKA included the production of charged particles, neutrons, photons, and neutrinos by the impact of Galactic protons. That investigation is extended here to include the effect of ionized helium, He-4, or a particles. Because high-energy GCRs excite planetary regoliths into giving rise to charmed mesons, neutrinos are produced. Thus a connection is established for the GCR helium production of prompt neutrinos on the Moon using the physics of charm.

  7. Detection efficiency of microchannel plates for e(-) and π(-) in the momentum range from 17.5 to 345 MeV/c.

    Science.gov (United States)

    Tulej, M; Meyer, S; Lüthi, M; Lasi, D; Galli, A; Desorgher, L; Hajdas, W; Karlsson, S; Kalla, L; Wurz, P

    2015-08-01

    High-energy e(-) and π(-) were measured by the multichannel plate (MCP) detector at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The measurements provide the absolute detection efficiencies for these particles: 5.8% ± 0.5% for electrons in the beam momenta range 17.5-300 MeV/c and 6.0% ± 1.3% for pions in the beam momenta range 172-345 MeV/c. The pulse height distribution determined from the measurements is close to an exponential function with negative exponent, indicating that the particles penetrated the MCP material before producing the signal somewhere inside the channel. Low charge extraction and nominal gains of the MCP detector observed in this study are consistent with the proposed mechanism of the signal formation by penetrating radiation. A very similar MCP ion detector will be used in the Neutral Ion Mass (NIM) spectrometer designed for the JUICE mission of European Space Agency (ESA) to the Jupiter system, to perform measurements of the chemical composition of the Galilean moon exospheres. The detection efficiency for penetrating radiation determined in the present studies is important for the optimisation of the radiation shielding of the NIM detector against the high-rate and high-energy electrons trapped in Jupiter's magnetic field. Furthermore, the current studies indicate that MCP detectors can be useful to measure high-energy particle beams at high temporal resolution.

  8. The lunar atmosphere and dust environment explorer mission (LADEE)

    CERN Document Server

    Russell, Christopher

    2015-01-01

    This volume contains five articles describing the mission and its instruments.  The first paper, by the project scientist Richard C. Elphic and his colleagues, describes the mission objectives, the launch vehicle, spacecraft and the mission itself.  This is followed by a description of LADEE’s Neutral Mass Spectrometer by Paul Mahaffy and company.  This paper describes the investigation that directly targets the lunar exosphere, which can also be explored optically in the ultraviolet.  In the following article Anthony Colaprete describes LADEE’s Ultraviolet and Visible Spectrometer that operated from 230 nm to 810 nm scanning the atmosphere just above the surface.  Not only is there atmosphere but there is also dust that putatively can be levitated above the surface, possibly by electric fields on the Moon’s surface.  Mihaly Horanyi leads this investigation, called the Lunar Dust Experiment, aimed at understanding the purported observations of levitated dust.  This experiment was also very succes...

  9. First direct evidence of sedimentary carbonate recycling in subduction-related xenoliths.

    Science.gov (United States)

    Liu, Yongsheng; He, Detao; Gao, Changgui; Foley, Stephen; Gao, Shan; Hu, Zhaochu; Zong, Keqing; Chen, Haihong

    2015-06-23

    Carbon in rocks and its rate of exchange with the exosphere is the least understood part of the carbon cycle. The amount of carbonate subducted as sediments and ocean crust is poorly known, but essential to mass balance the cycle. We describe carbonatite melt pockets in mantle peridotite xenoliths from Dalihu (northern China), which provide firsthand evidence for the recycling of carbonate sediments within the subduction system. These pockets retain the low trace element contents and δ(18)OSMOW = 21.1 ± 0.3 of argillaceous carbonate sediments, representing wholesale melting of carbonates instead of filtered recycling of carbon by redox freezing and melting. They also contain microscopic diamonds, partly transformed to graphite, indicating that depths >120 km were reached, as well as a bizarre mixture of carbides and metal alloys indicative of extremely reducing conditions. Subducted carbonates form diapirs that move rapidly upwards through the mantle wedge, reacting with peridotite, assimilating silicate minerals and releasing CO2, thus promoting their rapid emplacement. The assimilation process produces very local disequilibrium and divergent redox conditions that result in carbides and metal alloys, which help to interpret other occurrences of rock exhumed from ultra-deep conditions.

  10. Non-LTE models of Titan's upper atmosphere

    Science.gov (United States)

    Yelle, Roger V.

    1991-01-01

    Models for the thermal structure of Titan's upper atmosphere, between 0.1 mbar and 0.01 nbar are presented. The calculations include non-LTE heating/cooling in the rotation-vibration bands of CH4, C2H2, and C2H6, absorption of solar IR radiation in the near-IR bands of CH4 and subsequent cascading to the nu-4 band of CH4, absorption of solar EUV and UV radiation, thermal conduction and cooling by HCN rotational lines. Unlike earlier models, the calculated exospheric temperature agrees well with observations, because of the importance of HCN cooling. The calculations predict a well-developed mesopause with a temperature of 135-140 K at an altitude of approximately 600 km and pressure of about 0.1 microbar. The mesopause is at a higher pressure than predicted by earlier calculations because non-LTE radiative transfer in the rotation-vibration bands of CH4, C2H2, and C2H6 is treated in an accurate manner. The accuracy of the LTE approximation for source functions and heating rates is discussed.

  11. An extremely high altitude plume seen at Mars morning terminator

    Science.gov (United States)

    Sanchez-Lavega, Agustin; Garcia-Muñoz, Antonio; Garcia-Melendo, Enrique; Perez-Hoyos, Santiago; Gomez-Forrellad, Josep M.; Pellier, Christophe; Delcroix, Marc; Lopez-Valverde, Miguel Angel; Gonzalez-Galindo, Francisco; Jaeschke, Wayne; Parker, Donald C.; Phillips, James H.; Peach, Damian

    2014-11-01

    We report the occurrence in March and April 2012 of two bright very high altitude plumes at the Martian terminator at 250 km or more above the surface, thus well into the ionosphere and bordering on the exosphere. They were located at about 195 deg West longitude and -45 deg latitude (at Terra Cimmeria) and lasted for about 10 days. The features showed day-to-day variability, and were seen at the morning terminator but not at the evening limb, which indicates rapid evolution in less than 10 hours and a cyclic behavior. Photometric measurements are used to explore two possible scenarios to explain their nature. If the phenomenon is due to suspended particles (dust, CO2 or H2O ice clouds) reflecting solar radiation, the mean size is about 0.1 microns with a nadir optical depth > 0.06. Alternatively, the plume could be auroral emission above a region with a strong magnetic anomaly and where aurora has previously been detected. Importantly, both explanations defy our current understanding of the Mars upper atmosphere.AcknowledgementsThis work was supported by the Spanish MINECO projects AYA2012-36666 with FEDER support, CONSOLIDER program ASTROMOL CSD2009-00038 and AYA2011-30613-CO2-1. Grupos Gobierno Vasco IT765-13 and UPV/EHU UFI11/55.

  12. The Sodium Tail of the Moon

    Science.gov (United States)

    Matta, M.; Smith, S.; Baumgardner, J.; Wilson, J.; Martinis, C.; Mendillo, M.

    2009-01-01

    During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping "hot" component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes.

  13. Sodium Atoms in the Lunar Exotail: Observed Velocity and Spatial Distributions

    Science.gov (United States)

    Line, Michael R.; Mierkiewicz, E. J.; Oliversen, R. J.; Wilson, J. K.; Haffner, L. M.; Roesler, F. L.

    2011-01-01

    The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations determined the average radial velocity of sodium atoms moving down the lunar tail beyond Earth along the Sun-Moon-Earth line (i.e., the anti-lunar point) to be 12.4 km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a 15 x times 15 deg region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights around new moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting 3 degrees east along the ecliptic per night. Preliminary modeling results suggest that the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution and that observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days.

  14. The velocity dependence of X-ray emission due to Charge Exchange: Applications in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-04-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate high-energy astrophysical environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities. Collisions of bare and H-like C to Al ions with H, He, and H2 are considered. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31

  15. The velocity dependence of X-ray emission due to Charge Exchange in the Cygnus Loop

    Science.gov (United States)

    Cumbee, Renata; Lyons, David; Mullen, Patrick Dean; Shelton, Robin L.; Stancil, Phillip C.; Schultz, David R.

    2016-01-01

    The fundamental collisional process of charge exchange (CX) has been been established as a primary source of X-ray emission from the heliosphere [1], planetary exospheres [2], and supernova remnants [3,4]. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly-excited, high charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays.To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross-sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, and classical-trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics for collisions of bare and H-like C to Al ions with H, He, and H2. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant will be shown as an example with ion velocity dependence.[1] Henley, D. B. & Shelton, R. L. 2010, ApJSS, 187, 388[2] Dennerl, K. et al. 2002, A&A 386, 319[3] Katsuda, S. et al. 2011, ApJ 730 24[4] Cumbee, R. S. et al. 2014, ApJ 787 L31This work was partially supported by NASA grant NNX09AC46G.

  16. Modeling Broadband X-Ray Absorption of Massive Star Winds

    Science.gov (United States)

    Leutenegger, Maurice A.; Cohen,David H.; Zsargo, Janos; Martell, Erin M.; MacArthur, James P.; Owocki, Stanley P.; Gagne, Marc; Hillier, D. John

    2010-01-01

    We present a method for computing the net transition of X-rays emitted by shock-heated plasma distributed throughout a partially optically thick stellar wind from a massive star. We find the transmission by an exact integration of the formal solution, assuming the emitting plasma and absorbing plasma are mixed at a constant mass ratio above some minimum radius, below which there is assumed to be no emission. This model is more realistic than either the slab absorption associated with a corona at the base of the wind or the exospheric approximation that assumes all observed X-rays are emitted without attenuation from above the radius of optical depth unity. Our model is implemented in XSPEC as a pre-calculated table that can be coupled to a user-defined table of the wavelength dependent wind opacity. We provide a default wind opacity model that is more representative of real wind opacities than the commonly used neutral ISM tabulation. Preliminary modeling of Chandra grating data indicates that the X-ray hardness trend of OB stars with spectral subtype cars largely be understood as a wind absorption effect.

  17. Hydrosphere, Atmosphere, Lithosphere, Biosphere: A Global Geophysical Union

    Science.gov (United States)

    Milly, P.

    2009-05-01

    Water moves freely among the major spheres of the earth system, and, in so doing, it unites them. The atmosphere is driven, moistened and clouded by water in its changing phases, with ubiquitous climatic consequences. The biosphere's organisms depend on the "universal solvent" for access to and internal transport of nutrients, so much so that water availability defines the very geography of photosynthesis and life. The lithosphere is variously loaded, inflated, lubricated and eroded by water, with geodynamic consequences of all sorts. The ever-changing gravitational pull of earth's wandering waters is felt even in the exosphere. The movement of water among the spheres is partially regulated by, and has enormous consequences for, the anthroposphere. The influence of the hydrosphere on the other spheres creates interesting opportunities (indeed, necessities) for hydrologists to play with puzzles and problems beyond their own traditional sphere. In the experience of the speaker, the American Geophysical Union has been a playground that promotes such play, and the future promises more interdisciplinary fun; we have nothing to fear but spheres by themselves.

  18. The STORM and CuPID soft X-ray cameras on the DXL sounding rocket mission: Employment of slumped micropore optics to image solar wind charge exchange X-ray emission in the magnetosheath.

    Science.gov (United States)

    Thomas, N.

    2016-12-01

    The Sheath Transport Observer for the Redistribution of Mass (STORM) and the Cusp Plasma Imaging Detector (CuPID) instruments are soft X-ray cameras the utilize slumped micropore ('lobster-eye') optics. These lobster-eye optics, developed by the University of Leicester and the Photonis Corporation, provide for wide field-of-view imaging of X-ray line emission produced via charge exchange between hydrogen in the Earth's exosphere and heavy ions in the solar wind. Both instruments have position sensitize, chevron configuration, microchannel plate detectors in their respective focal planes. STORM possess two, 4 cm by 4 cm, lobster-eye optics, each with a focal length of 37.5 cm. It flew as a piggy back payload on the Diffuse X-ray emission from the Local galaxy (DXL) sounding rocket mission which was launched in December of 2012 from White Sands Missile Range, New Mexico. STORM operated successfully during this mission and represents the first use of lobster-eye optics in space. A future version of STORM, in high orbit, could image a significant portion of the magnetosheath to infer the locations of the magnetopause and the bow shock. CuPID is a 3U CubeSat variant of STORM that uses a single optic with a 27.5 cm focal length. A sounding rocket borne CuPID flew as a science payload with DXL from White Sands in December of 2015 with results forthcoming.

  19. Distribution and escape of the major neutral species from Titan's atmosphere

    Science.gov (United States)

    Tenishev, Valeriy; Tucker, Orenthal; Borovikov, Dmitry; Combi, Michael R.

    2016-10-01

    Titan possesses the most significant atmosphere among all satellites in the Solar system, and is an important source of material for the Saturn's magnetosphere. Understanding of the neutral species distribution and escape is important for further understanding of the Titan's atmosphere evolution and loss.The first in situ observations of the Titan's atmosphere were performed by Voyager and continued by Cassini, which measured the atmospheric composition, velocity and temperature, as well as the energy spectra of neutral species, ions and electrons. Analysis and interpretation of the acquired data involves coupled modeling of the Saturn magnetosphere and Titan's atmosphere.Having that in mind we have undertaken numerical modeling of the major neutral species (N2 and CH4) in Titan's upper atmosphere to investigate the effect of the solar EUV and magnetospheric ion energy deposition on the neutral species atmospheric distribution and escape. This modeling combines MHD simulation of the Saturn's magnetosphere plasma interacting with Titan's atmosphere, fluid type simulation of the neutral species in Titan's lower atmosphere, and kinetic modeling of the upper atmosphere and exosphere. Here we present estimations of the neutral species escape rate, and discuss the effect of the magnetospheric ion energy deposition on the atmospheric escape concluded from the results of our modeling.This work was supported by NASA Outer Planet Research grant NNX13AL04G.

  20. Gone with the Wind: Three Years of MAVEN Measurements of Atmospheric Loss at Mars

    Science.gov (United States)

    Brain, David; MAVEN Team

    2017-10-01

    The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission is making measurements of the Martian upper atmosphere and near space environment, and their interactions with energy inputs from the Sun. A major goal of the mission is to evaluate the loss of atmospheric gases to space in the present epoch, and over Martian history. MAVEN is equipped with instruments that measure both the neutral and charged upper atmospheric system (thermosphere, ionosphere, exosphere, and magnetosphere), inputs from the Sun (extreme ultraviolet flux, solar wind and solar energetic particles, and interplanetary magnetic field), and escaping atmospheric particles. The MAVEN instruments, coupled with models, allow us to more completely understand the physical processes that control atmospheric loss and the particle reservoirs for loss.Here, we provide an overview of the significant results from MAVEN over approximately 1.5 Mars years (nearly three Earth years) of observation, from November 2014 to present. We argue that the MAVEN measurements tell us that the loss of atmospheric gases to space was significant over Martian history, and present the seasonal behavior of the upper atmosphere and magnetosphere. We also discuss the influence of extreme events such as solar storms, and a variety of new discoveries and observations of the Martian system made by MAVEN.

  1. Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star

    Science.gov (United States)

    Bourrier, Vincent; Lovis, Christophe; Beust, Hervé; Ehrenreich, David; Henry, Gregory W.; Astudillo-Defru, Nicola; Allart, Romain; Bonfils, Xavier; Ségransan, Damien; Delfosse, Xavier; Cegla, Heather M.; Wyttenbach, Aurélien; Heng, Kevin; Lavie, Baptiste; Pepe, Francesco

    2018-01-01

    The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin–orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere.

  2. Charge Exchange X-Ray Emission due to Highly Charged Ion Collisions with H, He, and H2: Line Ratios for Heliospheric and Interstellar Applications

    Science.gov (United States)

    Cumbee, R. S.; Mullen, P. D.; Lyons, D.; Shelton, R. L.; Fogle, M.; Schultz, D. R.; Stancil, P. C.

    2018-01-01

    The fundamental collisional process of charge exchange (CX) has been established as a primary source of X-ray emission from the heliosphere, planetary exospheres, and supernova remnants. In this process, X-ray emission results from the capture of an electron by a highly charged ion from a neutral atom or molecule, to form a highly excited, high-charge state ion. As the captured electron cascades down to the lowest energy level, photons are emitted, including X-rays. To provide reliable CX-induced X-ray spectral models to realistically simulate these environments, line ratios and spectra are computed using theoretical CX cross sections obtained with the multi-channel Landau-Zener, atomic-orbital close-coupling, molecular-orbital close-coupling, and classical trajectory Monte Carlo methods for various collisional velocities relevant to astrophysics. X-ray spectra were computed for collisions of bare and H-like C to Al ions with H, He, and H2 with results compared to available experimental data. Using these line ratios, XSPEC models of CX emission in the northeast rim of the Cygnus Loop supernova remnant and the heliosphere are shown as examples with ion velocity dependence.

  3. Sodium Ion Dynamics in the Magnetospheric Flanks of Mercury

    Science.gov (United States)

    Aizawa, Sae; Delcourt, Dominique; Terada, Naoki

    2018-01-01

    We investigate the transport of planetary ions in the magnetospheric flanks of Mercury. In situ measurements from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft show evidences of Kelvin-Helmholtz instability development in this region of space, due to the velocity shear between the downtail streaming flow of solar wind originating protons in the magnetosheath and the magnetospheric populations. Ions that originate from the planet exosphere and that gain access to this region of space may be transported across the magnetopause along meandering orbits. We examine this transport using single-particle trajectory calculations in model Magnetohydrodynamics simulations of the Kelvin-Helmholtz instability. We show that heavy ions of planetary origin such as Na+ may experience prominent nonadiabatic energization as they E × B drift across large-scale rolled up vortices. This energization is controlled by the characteristics of the electric field burst encountered along the particle path, the net energy change realized corresponding to the maximum E × B drift energy. This nonadiabatic energization also is responsible for prominent scattering of the particles toward the direction perpendicular to the magnetic field.

  4. An Impacting Descent Probe for Europa and the Other Galilean Moons of Jupiter

    Science.gov (United States)

    Wurz, P.; Lasi, D.; Thomas, N.; Piazza, D.; Galli, A.; Jutzi, M.; Barabash, S.; Wieser, M.; Magnes, W.; Lammer, H.; Auster, U.; Gurvits, L. I.; Hajdas, W.

    2017-08-01

    We present a study of an impacting descent probe that increases the science return of spacecraft orbiting or passing an atmosphere-less planetary bodies of the solar system, such as the Galilean moons of Jupiter. The descent probe is a carry-on small spacecraft (<100 kg), to be deployed by the mother spacecraft, that brings itself onto a collisional trajectory with the targeted planetary body in a simple manner. A possible science payload includes instruments for surface imaging, characterisation of the neutral exosphere, and magnetic field and plasma measurement near the target body down to very low-altitudes ( 1 km), during the probe's fast ( km/s) descent to the surface until impact. The science goals and the concept of operation are discussed with particular reference to Europa, including options for flying through water plumes and after-impact retrieval of very-low altitude science data. All in all, it is demonstrated how the descent probe has the potential to provide a high science return to a mission at a low extra level of complexity, engineering effort, and risk. This study builds upon earlier studies for a Callisto Descent Probe for the former Europa-Jupiter System Mission of ESA and NASA, and extends them with a detailed assessment of a descent probe designed to be an additional science payload for the NASA Europa Mission.

  5. Lunar volcanism produced a transient atmosphere around the ancient Moon

    Science.gov (United States)

    Needham, Debra H.; Kring, David A.

    2017-11-01

    Studies of the lunar atmosphere have shown it to be a stable, low-density surface boundary exosphere for the last 3 billion years. However, substantial volcanic activity on the Moon prior to 3 Ga may have released sufficient volatiles to form a transient, more prominent atmosphere. Here, we calculate the volume of mare basalt emplaced as a function of time, then estimate the corresponding production of volatiles released during the mare basalt-forming eruptions. Results indicate that during peak mare emplacement and volatile release ∼3.5 Ga, the maximum atmospheric pressure at the lunar surface could have reached ∼1 kPa, or ∼1.5 times higher than Mars' current atmospheric surface pressure. This lunar atmosphere may have taken ∼70 million years to fully dissipate. Most of the volatiles released by mare basalts would have been lost to space, but some may have been sequestered in permanently shadowed regions on the lunar surface. If only 0.1% of the mare water vented during these eruptions remains in the polar regions of the Moon, volcanically-derived volatiles could account for all hydrogen deposits - suspected to be water - currently observed in the Moon's permanently shadowed regions. Future missions to such locations may encounter evidence of not only asteroidal, cometary, and solar wind-derived volatiles, but also volatiles vented from the interior of the Moon.

  6. How Well Does the Present Surface Inventory of Water on Mars Constrain the Past?

    Science.gov (United States)

    Clifford, S. M.; McCubbin, F. M.

    2016-01-01

    Over the past 40 years, estimates of the total outgassed inventory of water on Mars have ranged from a global equivalent layer (GEL) approximately 7-1000 m deep. However, Carr and Head have recently argued that it is not the total inventory of outgassed water that is important, but the amount that exists in climatically exchangeable surface and near surface reservoirs - suggesting that any exchange with water in the deep subsurface is precluded by the existence of a thick cryosphere, at least during the Amazonian and Hesperian. Based on this assumption and their estimate of the present day near-surface inventory of H2O (approximately 34 m GEL, stored as ice in the polar layered deposits (PLD), lobate debris aprons, ice-rich latitude dependent mantles, and as shallow ground ice), they extrapolate the evolution of this inventory backward in time, taking into account the introduction of new water by volcanism, outflow channel activity, and the loss of water by exospheric escape. They conclude that, at the end of the Noachian, Mars had a near-surface water inventory of approximately 24 m and approximately 62 m by the end of the Hesperian - inventories that Carr and Head argue were incompatible with the existence of a former ocean.

  7. SWCX Emission from the Helium Focusing Cone - Preliminary Results

    Science.gov (United States)

    Snowden, S. L.; Kuntz, K. D.; Collier, M. R.

    2008-01-01

    Preliminary results from an XMM-Newton campaign to study solar wind charge exchange (SWCX) emission from the heliospheric focusing cone of interstellar helium are presented. The detections of enhanced O VII and O VIII emission from the cone are at the 2(sigma) and 4(sigma) levels. The solar wind charge exchange (SWCX) emission in the heliosphere not associated with distinct objects (e.g., comets and planets including exospheric material in and near Earth s magnetosheath) is proportional to the flux of the solar wind and the space density of neutral material. The neutral material originates in the interstellar medium (ISM) and passes through the solar system due to the relative motion of the Sun and the ISM. The flow of the neutral material through the solar system is strongly perturbed by the Sun both by gravity and by radiation pressure. Because of the relative radiative scattering cross sections and the effect of solar gravitation the density of interstellar hydrogen near the Sun is reduced while interstellar helium is gravitationally focused. This creates a helium focusing cone downstream of the Sun [e.g., 1, and references therein].

  8. Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star.

    Science.gov (United States)

    Bourrier, Vincent; Lovis, Christophe; Beust, Hervé; Ehrenreich, David; Henry, Gregory W; Astudillo-Defru, Nicola; Allart, Romain; Bonfils, Xavier; Ségransan, Damien; Delfosse, Xavier; Cegla, Heather M; Wyttenbach, Aurélien; Heng, Kevin; Lavie, Baptiste; Pepe, Francesco

    2017-12-18

    The angle between the spin of a star and the orbital planes of its planets traces the history of the planetary system. Exoplanets orbiting close to cool stars are expected to be on circular, aligned orbits because of strong tidal interactions with the stellar convective envelope. Spin-orbit alignment can be measured when the planet transits its star, but such ground-based spectroscopic measurements are challenging for cool, slowly rotating stars. Here we report the three-dimensional characterization of the trajectory of an exoplanet around an M dwarf star, derived by mapping the spectrum of the stellar photosphere along the chord transited by the planet. We find that the eccentric orbit of the Neptune-mass exoplanet GJ 436b is nearly perpendicular to the stellar equator. Both eccentricity and misalignment, surprising around a cool star, can result from dynamical interactions (via Kozai migration) with a yet-undetected outer companion. This inward migration of GJ 436b could have triggered the atmospheric escape that now sustains its giant exosphere.

  9. Using Dawn to Observe SEP Events Past 2 AU

    Science.gov (United States)

    Villarreal, Michaela; Russell, Christopher T.; Prettyman, Thomas H.

    2017-10-01

    The launch of the STEREO spacecraft provided much insight into the longitudinal and radial distribution of solar energetic particles (SEPs) relative to their origin site. However, almost all of the observations of SEP events have been made exclusively near 1 AU. The Dawn mission, which orbited around Vesta before arriving at Ceres, provides an opportunity to analyze these events at much further distances. Although Dawn's Gamma Ray and Neutron Detector (GRaND) is not optimized for SEP characterization, it is sensitive to protons greater than 4 MeV, making it capable of detecting a solar energetic particle event in its vicinity. Solar energetic particles in this area of the solar system are important as they are believed to cause sputtering at bodies such as Ceres and comets (Villarreal et al., 2017; Wurz et al., 2015). In this study, we use Dawn’s GRaND data from 2011-2015 when Dawn was at distances between 2-3 AU. We compare the SEP events seen by Dawn with particle measurements at 1 AU using STEREO, Wind, and ACE to understand how the SEP events evolved past 1 AU.References: Villarreal, M. N., et al. (2017), The dependence of the Cerean exosphere on solar energetic particle events, Astrophys. J. Lett., 838, L8.Wurz, P. et al. (2015), Solar wind sputtering of dust on the surface of 67P/Churyumov-Gerasimenko, A&A, 583, A22.

  10. A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b.

    Science.gov (United States)

    Ehrenreich, David; Bourrier, Vincent; Wheatley, Peter J; des Etangs, Alain Lecavelier; Hébrard, Guillaume; Udry, Stéphane; Bonfils, Xavier; Delfosse, Xavier; Désert, Jean-Michel; Sing, David K; Vidal-Madjar, Alfred

    2015-06-25

    Exoplanets orbiting close to their parent stars may lose some fraction of their atmospheres because of the extreme irradiation. Atmospheric mass loss primarily affects low-mass exoplanets, leading to the suggestion that hot rocky planets might have begun as Neptune-like, but subsequently lost all of their atmospheres; however, no confident measurements have hitherto been available. The signature of this loss could be observed in the ultraviolet spectrum, when the planet and its escaping atmosphere transit the star, giving rise to deeper and longer transit signatures than in the optical spectrum. Here we report that in the ultraviolet the Neptune-mass exoplanet GJ 436b (also known as Gliese 436b) has transit depths of 56.3 ± 3.5% (1σ), far beyond the 0.69% optical transit depth. The ultraviolet transits repeatedly start about two hours before, and end more than three hours after the approximately one hour optical transit, which is substantially different from one previous claim (based on an inaccurate ephemeris). We infer from this that the planet is surrounded and trailed by a large exospheric cloud composed mainly of hydrogen atoms. We estimate a mass-loss rate in the range of about 10(8)-10(9) grams per second, which is far too small to deplete the atmosphere of a Neptune-like planet in the lifetime of the parent star, but would have been much greater in the past.

  11. The GOLD Science Data Center - Algorithm Heritage, Data Product Descriptions and User Services

    Science.gov (United States)

    Lumpe, J. D.; Foroosh, H.; Eastes, R.; Krywonos, A.; Evans, J. S.; Burns, A. G.; Strickland, D. J.; Daniell, R. E.; England, S.; Solomon, S. C.; McClintock, W. E.; Anderson, D. N.

    2013-12-01

    The Global-scale Observations of the Limb and Disk (GOLD) instrument is an imaging spectrograph to be launched onboard a commercial communications satellite in 2017. From its vantage point in geosynchronous orbit GOLD will image the Earth in the far-ultraviolet from 132 to 162 nm. The instrument consists of two independent optical channels, allowing for simultaneous implementation of multiple measurement sequences with different temporal sampling and spectral resolution. In addition to continuously scanning the disk of the Earth, GOLD will also perform routine limb scan and stellar occultation measurements. These measurements will be used to retrieve a variety of data products characterizing the temperature and composition of the thermosphere-ionosphere, and their response to geomagnetic storms and solar forcing. Primary data products include: daytime neutral temperatures near 160 km altitude; daytime O/N2 column density ratios; nighttime peak electron density; thermospheric O2 density profiles (day and night); daytime exospheric neutral temperature on the limb; atmospheric tides from temperature perturbations; and the location and evolution of ionospheric bubbles. GOLD data will be processed at the Science Data Center (SDC) located at the University of Central Florida. The SDC will also serve as the primary gateway for distribution of GOLD data products to end-users. In this talk we summarize the heritage and theoretical basis of the GOLD retrieval algorithms and describe the full range of GOLD data products that will be available at the SDC, including estimates of data latency and quality.

  12. Dynamics of the low altitude secondary proton radiation belt.

    Science.gov (United States)

    Gusev, A A; Kohno, T; Spjeldvik, W N; Martin, I M; Pugacheva, G I; Turtelli, A

    1998-01-01

    At the interface between the upper atmosphere and the radiation belt region, there exists a secondary radiation belt consisting mainly of energetic ions that have become neutralized in the ring current and the main radiation belt and then re-ionized by collisions in the inner exosphere. The time history of the proton fluxes in the 0.64-35 MeV energy range was traced in the equatorial region beneath the main radiation belts during the three year period from 21 February 1984 to 26 March 1987 using data obtained with the HEP experiment on board the Japanese OHZORA satellite. During most of this period a fairly small proton flux of -1.2 cm-2 S-1 sr-1 was detected on geomagnetic field lines in the range 1.05 < L < 1.15. We report a few surprisingly deep and rapid flux decreases (flux reduction by typically two orders of magnitude). These flux decreases were also long in duration (lasting up to three months). We also registered abrupt flux increases where the magnitude of the proton flux enhancements could reach three orders of magnitude with an enhancement duration of 1-3 days. Possible reasons for these unexpected phenomena are discussed.

  13. A Microchannel Inlet to Reduce High-Velocity Impact Fragmentation of Molecules in Orbital and Fly-by Mass Spectrometers

    Science.gov (United States)

    Turner, Brandon; Anupriya, Anupriya; Sevy, Eric; Austin, Daniel E.

    2017-10-01

    Closed source neutral mass spectrometers are often used on flyby missions to characterize the molecular components of planetary exospheres. In a typical closed source, neutrals are thermalized as they deflect off the walls within a spherical antechamber prior to ionization and mass analysis. However, the high kinetic energy of each molecule as it impacts the chamber can lead to fragmentation before the ionization region is reached. Due to this fragmentation, the original composition of the molecule can be altered, leading to ambiguous identification.Even knowing the fragmentation pathways that occur may not allow deconvolution of data to give the correct composition. Only stable, volatile fragments will be observed in the subsequent mass spectrometer and different organic compounds likely give similar fragmentation products. Simply detecting these products will not lead to unambiguous identication of the precursor molecules. Here, we present a hardware solution to this problem—an inlet that reduces the fragmentation of molecules that impact at high velocities.We present a microchannel inlet that reduces the impact fragmentation by allowing the molecules to dissipate kinetic energy faster than their respective dissociation lifetimes. Preliminary calculations indicate that impact-induced fragmentation will be reduced up to three orders of magnitude compared with conventional closed sources by using this inlet. The benefits of such an inlet apply to any orbital or flyby velocity. The microchannel inlet enables detection of semi-volatile molecules that were previously undetectable due to impact fragmentation.

  14. Mars: a small terrestrial planet

    Science.gov (United States)

    Mangold, N.; Baratoux, D.; Witasse, O.; Encrenaz, T.; Sotin, C.

    2016-11-01

    Mars is characterized by geological landforms familiar to terrestrial geologists. It has a tenuous atmosphere that evolved differently from that of Earth and Venus and a differentiated inner structure. Our knowledge of the structure and evolution of Mars has strongly improved thanks to a huge amount of data of various types (visible and infrared imagery, altimetry, radar, chemistry, etc) acquired by a dozen of missions over the last two decades. In situ data have provided ground truth for remote-sensing data and have opened a new era in the study of Mars geology. While large sections of Mars science have made progress and new topics have emerged, a major question in Mars exploration—the possibility of past or present life—is still unsolved. Without entering into the debate around the presence of life traces, our review develops various topics of Mars science to help the search of life on Mars, building on the most recent discoveries, going from the exosphere to the interior structure, from the magmatic evolution to the currently active processes, including the fate of volatiles and especially liquid water.

  15. Recent advances in understanding lunar surface charging: modeling, theory and spacecraft observations

    Science.gov (United States)

    Poppe, A.; Halekas, J. S.; Delory, G. T.; Horanyi, M.; Angelopoulos, V.; Farrell, W. M.

    2012-12-01

    As an airless body in space, the Moon is exposed to a combination of ambient plasma and solar ultraviolet radiation that cause the lunar surface to electrostatically charge in response to these currents. Our understanding of lunar surface charging typically holds that the dayside surface reaches equilibrium potentials of a few volts positive, with a generally smooth transition to larger, negative potentials near the terminators and on the nightside. While much of this picture may hold true, there are several situations in which the lunar surface charge and the associated electrostatic potential do not conform to this picture. These instances include areas in and around surface craters, which can locally shadow the lunar surface, and times when the Moon is within the terrestrial plasma sheet and magnetotail lobes. We present a combination of results regarding lunar surface charging from recent three-dimensional plasma modeling, theoretical charging calculations, and analysis of in-situ measurements by the Lunar Prospector and ARTEMIS missions. We discuss the implications of these findings for other geophysical investigations, including measurements of pick-up ions from the surface and exosphere, the behavior of electrostatically charged dust, and the possible charging environments of other airless bodies throughout the solar system.

  16. Lunar pickup ions observed by ARTEMIS: Spatial and temporal distribution and constraints on species and source locations

    Science.gov (United States)

    Halekas, J. S.; Poppe, A. R.; Delory, G. T.; Sarantos, M.; Farrell, W. M.; Angelopoulos, V.; McFadden, J. P.

    2012-06-01

    ARTEMIS observes pickup ions around the Moon, at distances of up to 20,000 km from the surface. The observed ions form a plume with a narrow spatial and angular extent, generally seen in a single energy/angle bin of the ESA instrument. Though ARTEMIS has no mass resolution capability, we can utilize the analytically describable characteristics of pickup ion trajectories to constrain the possible ion masses that can reach the spacecraft at the observation location in the correct energy/angle bin. We find that most of the observations are consistent with a mass range of ˜20-45 amu, with a smaller fraction consistent with higher masses, and very few consistent with masses below ˜15 amu. With the assumption that the highest fluxes of pickup ions come from near the surface, the observations favor mass ranges of ˜20-24 and ˜36-40 amu. Although many of the observations have properties consistent with a surface or near-surface release of ions, some do not, suggesting that at least some of the observed ions have an exospheric source. Of all the proposed sources for ions and neutrals about the Moon, the pickup ion flux measured by ARTEMIS correlates best with the solar wind proton flux, indicating that sputtering plays a key role in either directly producing ions from the surface, or producing neutrals that subsequently become ionized.

  17. Optimising the science orbits for the Joint Europa Mission (JEM).

    Science.gov (United States)

    Desprats, William; Balmino, Georges; Laurent-Varin, Julien; Russell, Ryan

    2017-04-01

    JEM (a proposed NASA-ESA Joint Europa Mission) will be assigned the following overarching goal: Understand Europa as a complex system responding to Jupiter system forcing, characterize the habitability of its potential biosphere, and search for life in its surface, sub-surface and exosphere. The JEM observation strategy to address these goals will include measurements on a high-latitude, low-latitude Europan orbit providing a continuous and global mapping of planetary fields (magnetic and gravity) and of the neutral and charged environment during a period of three months, which will itself follow a sequence of science operations in halo orbit around the L1 Lagrangian point of the Europa-Jupiter system which will also be used to relay the data from the JEM lander. We will present a detailed mission analysis study by which the two successive sequences of science orbits have been optimized to best cover the JEM scientific objectives while satisfactorily fulfilling the mission constraints related to the lander delivery and relay functions.

  18. Role of the ionosphere for the atmospheric evolution of planets.

    Science.gov (United States)

    Yamauchi, Masatoshi; Wahlund, Jan-Erik

    2007-10-01

    We have synthesized current understanding, mainly observations, with regard to ion escape mechanisms to space from the ionosphere and exosphere of Titan and Earth-type planets, with the intent to provide an improved input for models of atmospheric evolution on early Earth and Earth-type planets and exoplanets. We focus on the role of the ionosphere and its non-linear response to solar parameters, all of which have been underestimated in current models of ancient atmospheric escape (4 billion years ago). Factors that have been overlooked include the following: (1) Much larger variation of O(+) outflow than H(+) outflow from the terrestrial ionosphere, depending on solar and geomagnetic activities (an important consideration when attempting to determine the oxidized state of the atmosphere of early Earth); (2) magnetization of the ionopause, which keeps ionospheric ions from escaping and controls many other escape processes; (3) extra ionization by, for example, the critical ionization velocity mechanism, which expands the ionosphere to greater altitudes than current models predict; and (4) the large escape of cold ions from the dense, expanded ionosphere of Titan. Here we offer, as a guideline for quantitative simulations, a qualitative diagnosis of increases or decreases of non-thermal escape related to the ionosphere for magnetized and unmagnetized planets in response to changes in solar parameters (i.e., solar EUV/FUV flux, solar wind dynamic pressure, and interplanetary magnetic field).

  19. Survey of pickup ion signatures in the vicinity of Titan using CAPS/IMS

    Science.gov (United States)

    Regoli, L. H.; Coates, A. J.; Thomsen, M. F.; Jones, G. H.; Roussos, E.; Waite, J. H.; Krupp, N.; Cox, G.

    2016-09-01

    Pickup ion detection at Titan is challenging because ion cyclotron waves are rarely detected in the vicinity of the moon. In this work, signatures left by freshly produced pickup heavy ions (m/q ˜ 16 to m/q ˜ 28) as detected in the plasma data by the Cassini Plasma Spectrometer/Ion Mass Spectrometer (CAPS/IMS) instrument on board Cassini are analyzed. In order to discern whether these correspond to ions of exospheric origin, one of the flybys during which the reported signatures were observed is investigated in detail. For this purpose, ion composition data from time-of-flight measurements and test particle simulations to constrain the ions' origin are used. After being validated, the detection method is applied to all the flybys for which the CAPS/IMS instrument gathered valid data, constraining the region around the moon where the signatures are observed. The results reveal an escape region located in the anti-Saturn direction as expected from the nominal corotation electric field direction. These findings provide new constraints for the area of freshly produced pickup ion escape, giving an approximate escape rate of 3.3-2+3×1023 ions· s-1.

  20. Applications of High Etendue Line-Profile Spectro-Polarimetry to the Study of the Atmospheric and Magnetospheric Environments of the Jovian Icy Moons

    Science.gov (United States)

    Harris, Walter M.; Roesler, Fred L.; Jaffel, Lotfi Ben; Ballester, Gilda E.; Oliversen, Ronald J.; Morgenthaler, Jeffrey P.; Mierkiewicz, Edwin

    2003-01-01

    Electrodynamic effects play a significant, global role in the state and energization of the Earth's ionosphere/magnetosphere, but even more so on Jupiter, where the auroral energy input is four orders of magnitude greater than on Earth. The Jovian magnetosphere is distinguished from Earth's by its rapid rotation rate and contributions from satellite atmospheres and internal plasma sources. The electrodynamic effects of these factors have a key role in the state and energization of the ionosphere-corona- plasmasphere system of the planet and its interaction with Io and the icy satellites. Several large scale interacting processes determine conditions near the icy moons beginning with their tenuous atmospheres produced from sputtering, evaporative, and tectonic/volcanic sources, extending out to exospheres that merge with ions and neutrals in the Jovian magnetosphere. This dynamic environment is dependent on a complex network of magnetospheric currents that act on global scales. Field aligned currents connect the satellites and the middle and tail magnetospheric regions to the Jupiter's poles via flux tubes that produce as bright auroral and satellite footprint emissions in the upper atmosphere. This large scale transfer of mass, momentum, and energy (e.g. waves, currents) means that a combination of complementary diagnostics of the plasma, neutral, and and field network must be obtained near simultaneously to correctly interpret the results. This presentation discusses the applicability of UV spatial heterodyne spectroscopy (SHS) to the broad study of this system on scales from satellite surfaces to Jupiter's aurora and corona.

  1. MESSENGER, MErcury: Surface, Space ENvironment, GEochemistry, and Ranging; A Mission to Orbit and Explore the Planet Mercury

    Science.gov (United States)

    1999-01-01

    MESSENGER is a scientific mission to Mercury. Understanding this extraordinary planet and the forces that have shaped it is fundamental to understanding the processes that have governed the formation, evolution, and dynamics of the terrestrial planets. MESSENGER is a MErcury Surface, Space ENvironment, GEochemistry and Ranging mission to orbit Mercury for one Earth year after completing two flybys of that planet following two flybys of Venus. The necessary flybys return significant new data early in the mission, while the orbital phase, guided by the flyby data, enables a focused scientific investigation of this least-studied terrestrial planet. Answers to key questions about Mercury's high density, crustal composition and structure, volcanic history, core structure, magnetic field generation, polar deposits, exosphere, overall volatile inventory, and magnetosphere are provided by an optimized set of miniaturized space instruments. Our goal is to gain new insight into the formation and evolution of the solar system, including Earth. By traveling to the inner edge of the solar system and exploring a poorly known world, MESSENGER fulfills this quest.

  2. Preshock region acceleration of implanted cometary H(+) and O(+)

    Science.gov (United States)

    Gombosi, Tamas I.

    1988-01-01

    A self-consistent, three-fluid model of plasma transport and implanted ion acceleration in the unshocked solar wind is presented. The solar wind plasma is depleted by charge exchange with the expanding cometary exosphere, while implanted protons and heavy ions are produced by photoionization and charge transfer and lost by charge exchange. A generalized transport equation describing convection, adiabatic and diffusive velocity change, and the appropriate production terms is used to describe the evolution of the two cometary ion components, while the moments of the Boltzmann equation are used to calculate the solar wind density and pressure. The flow velocity is obtained self-consistently by combining the conservation equations of the three ion species. The results imply that second-order Fermi acceleration can explain the implanted spectra observed in the unshocked solar wind. Comparison of measured and calculated distribution indicates that spatial diffusion of implanted ions probably plays an important role in forming the energetic particle environment in the shock vicinity.

  3. The Plasma Wave Investigation (PWI) onboard the BepiColombo/MMO: First measurement of electric fields, electromagnetic waves, and radio waves around Mercury

    Science.gov (United States)

    Kasaba, Y.; Bougeret, J.-L.; Blomberg, L. G.; Kojima, H.; Yagitani, S.; Moncuquet, M.; Trotignon, J.-G.; Chanteur, G.; Kumamoto, A.; Kasahara, Y.; Lichtenberger, J.; Omura, Y.; Ishisaka, K.; Matsumoto, H.

    2010-01-01

    The BepiColombo Mercury Magnetospheric Orbiter (MMO) spacecraft includes the plasma and radio wave observation system called Plasma Wave Investigation (PWI). Since the receivers for electric field, plasma waves, and radio waves are not installed in any of the preceding spacecraft to Mercury, the PWI will provide the first opportunity for conducting in-situ and remote-sensing observations of electric fields, plasma waves, and radio waves in the Hermean magnetosphere and exosphere. These observations are valuable in studying structure, dynamics, and energy exchange processes in the unique magnetosphere of Mercury. They are characterized by the key words of the non-MHD environment and the peculiar interaction between the relatively large planet without ionosphere and the solar wind with high dynamic pressure. The PWI consists of three sets of receivers (EWO, SORBET, and AM 2P), connected to two sets of electric field sensors (MEFISTO and WPT) and two kinds of magnetic field sensors (LF-SC and DB-SC). The PWI will observe both waveforms and frequency spectra in the frequency range from DC to 10 MHz for the electric field and from 0.3 Hz to 640 kHz for the magnetic field. From 2008, we will start the development of the engineering model, which is conceptually consistent with the flight model design. The present paper discusses the significance and objectives of plasma/radio wave observations in the Hermean magnetosphere, and describes the PWI sensors, receivers and their performance as well as the onboard data processing.

  4. Nature of the Venus thermosphere derived from satellite drag measurements (solicited paper)

    Science.gov (United States)

    Keating, G.; Theriot, M.; Bougher, S.

    2008-09-01

    From drag measurements obtained by Pioneer Venus and Magellan, the Venus upper atmosphere was discovered to be much colder than Earth's, even though Venus is much closer to the Sun than the Earth. On the dayside, exospheric temperatures are near 300K compared to Earth's of near 1200K [1]. This is thought to result principally from 15 micron excitation of carbon dioxide by atomic oxygen resulting in very strong 15 micron emission to space, cooling off the upper atmosphere [2]. On the nightside the Venus upper atmosphere is near 100K [3], compared to Earth where temperatures are near 900K. The nightside Venus temperatures drop with altitude contrary to a thermosphere where temperatures rise with altitude. As a result, the very cold nightside is called a "cryosphere" rather than a thermosphere. This is the first cryosphere discovered in the solar system [1]. Temperatures sharply drop near the terminator. Apparently, heat is somehow blocked near the terminator from being significantly transported to the nightside [4]. Recently, drag studies were performed on a number of Earth satellites to establish whether the rise of carbon dioxide on Earth was cooling the Earth's thermosphere similar to the dayside of Venus. Keating et al. [5] discovered that a 10 percent drop in density near 350km at solar minimum occurred globally over a period of 20 years with a 10 per cent rise in carbon dioxide. This should result in about a factor of 2 decline in density from 1976 values, by the end of the 21st century brought on by thermospheric cooling. Subsequent studies have confirmed these results. Thus we are beginning to see the cooling of Earth's upper atmosphere apparently from the same process cooling the Venus thermosphere. Fig. 1 VIRA Exospheric Temperatures Atmospheric drag data from the Pioneer Venus Orbiter and Magellan were combined to generate an improved version of the Venus International Reference Atmosphere (VIRA) [6], [7]. A "fountain effect" was discovered where the

  5. Cassini's Ring Grazing and Grand Finale Orbits: Topping Off an Awesome Mission

    Science.gov (United States)

    Edgington, Scott; Spilker, Linda; Coustenis, Athena

    2017-04-01

    The Cassini-Huygens mission, a joint collaboration between NASA, ESA, and the Italian Space Agency, is in its last year of operations after nearly 13 years in orbit around Saturn. Cassini will send back its final bits of unique data on September 15th, 2017 as it plunges into Saturn's atmosphere, vaporizing and satisfying planetary protection requirements. Before that time Cassini will continue its legacy of exploration and discovery in 2017 and return unique science data provided by orbits taking the spacecraft into unexplored regions near Saturn and its rings. From the new vantage points, Cassini will continue to study seasonal and temporal changes in the system as northern summer solstice approaches. With the exception of one remaining targeted Titan flyby, all of Cassini's close icy satellite flybys, including those of Enceladus, are now completed. In November 2016, Cassini transitioned to a series of orbits with peripases just outside Saturn's F ring. These 20 orbits include close flybys of some tiny ring moons and excellent views of the F ring and Saturn's outer A ring. The 126th and final close flyby of Titan will propel Cassini across Saturn's main rings and into its Grand Finale series of orbits. Cassini's Grand Finale, starting in April 2017, is comprised of 22 orbits at an inclination of 63 degrees. Cassini will repeatedly dive between Saturn's innermost rings and upper atmosphere providing insights into fundamental questions unattainable during the rest of the mission. Cassini will be the first spacecraft to explore this region. These close orbits provide the highest resolution observations of both the rings and Saturn, and direct in-situ sampling of the ring particles, composition, plasma, Saturn's exosphere and the innermost radiation belts. Saturn's gravitational field will be measured to unprecedented accuracy, providing information on the interior structure of the planet, winds in the outer layers of Saturn's atmosphere, and the mass distribution in

  6. SIMBIO-SYS for BepiColombo: status and issues.

    Science.gov (United States)

    Flamini, E.; Capaccioni, F.; Cremonese, G.; Palumbo, P.; Formaro, R.; Mugnuolo, R.; Debei, S.; Ficai Veltroni, I.; Dami, M.; Tommasi, L.; SIMBIO-SYS Team

    the type and distribution of mineral species Reconstruction of the surface geology and stratigraphic history: based on the combination of stereo and high- resolution imaging along with compositional information coming from the spectrometer Relative surface age by impact craters population density and distribution: based on the global imaging including the high-resolution mode Surface degradation processes and global resurfacing: derived from the erosional status of the impact crater and ejecta Identification of volcanic landforms and style: using the morphological and compositional information Crustal dynamics and mechanical properties of the lithosphere: based on the identification and classification of tectonic structures from visible images and detailed DTM Surface composition and crustal differentiation: based on the identification and distribution of mineral species as seen by the NIR hyperspectral imager Soil maturity and alteration processes: based on the measure of the spectral slope derived by the hyperspectral imager and the colour capabilities of the stereo camera Determination of moment of inertia of the planet: the high-resolution imaging channel as landmark pairs of surface features that can be observed on the periside as support for the libration experiment Surface-Atmosphere interaction processes and origin of the exosphere: knowledge of the surface composition is also crucial to unambiguously identify the source minerals for each of the constituents of the Mercury.s exosphere The instrument has been realized by Selex-ES under the contract and management of the Italian Space Agency (ASI) that have signed an MoU with CNES for the development of VIHI Proximity Electronics, the Main Electronics, and the instrument final calibration . All the realization and calibration has been carried on under the scientific supervision of the SIMBIO-SYS science team SIMBIOSYS has been delivered to ESA on April 2015 for the final integration on the BepiColombo MPO

  7. Facts and Suggestions from a Brief History of the Galilean Moons and Space Weathering

    Science.gov (United States)

    Cooper, John

    2010-05-01

    energetic enough to change isotopic ratios in the affected surface materials. The sputtered materials partially escape either directly to the magnetosphere or indirectly through exospheric losses, so these additionally contribute at trace levels to the magnetospheric interconnections of surface composition for all the moons. In order to determine the intrinsic composition of the moons from EJSM surface and exospheric measurements, we must first peel back the surficial patina of space weathering products. Conversely, future measurements of the magnetospheric ion composition at high resolution in elemental and significant isotopic abundances, including as products of space weathering on the moon surfaces, can be projected back to the Io source for huge advancements of our knowledge on the origins of Io volcanism and more generally of the Jupiter system. These are some of the relevant facts for space weathering from 400 years of Jupiter system exploration, the main suggestion is that one the highest returns on international investments in the EJSM mission would be from advancement of capabilities for in-situ sample analysis in the magnetosphere and from moon surfaces to cover the full range of elements and key isotopes. Modest investments in appropriate technologies for ion and neutral gas measurements to this level would be insignificant in cost as compared to Earth sample return. This suggestion was submitted by Cooper et al. [4] to the ongoing decadal survey of planetary science and mission priorities in the United States. References: [1] Stebbins, J., Publ. Astron. Soc. Pacific 38 (225), 321-322, 1926; [2] Burke, B.F., and K. L. Franklin, J. Geophys. Res. 60, 213-217, 1955. [3] Morabito, L. A., et al., Science 204, 972, 1979; [4] Cooper, J. F., and 21 Co-authors, Space Weathering Impact on Solar System Surfaces and Mission Science, Community White Paper submitted to Planetary Science Decadal Survey, 2013--2022. National Research Council, Washington, D.C., Sept. 15, 2009.

  8. Investigation of dust particles with future Russian lunar missions: achievements of further development of PmL instrument.

    Science.gov (United States)

    Kuznetsov, Ilya; Zakharov, Alexander; Afonin, Valeri; Seran, Elena; Godefroy, Michel; Shashkova, Inna; Lyash, Andrey; Dolnikov, Gennady; Popel, Sergey; Lisin, Evgeny

    2016-07-01

    One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Meteorites bombardment has accompanied by shock-explosive phenomena, disintegration and mix of the lunar soil in depth and on area simultaneously. As a consequence, the lunar soil has undergone melting, physical and chemical transformations. Recently we have the some reemergence for interest of Moon investigation. The prospects in current century declare USA, China, India, and European Union. In Russia also prepare two missions: Luna-Glob and Luna-Resource. Not last part of investigation of Moon surface is reviewing the dust condition near the ground of landers. Studying the properties of lunar dust is important both for scientific purposes to investigation the lunar exosphere component and for the technical safety of lunar robotic and manned missions. The absence of an atmosphere on the Moon's surface is leading to greater compaction and sintering. Properties of regolith and dust particles (density, temperature, composition, etc.) as well as near-surface lunar exosphere depend on solar activity, lunar local time and position of the Moon relative to the Earth's magneto tail. Upper layers of regolith are an insulator, which is charging as a result of solar UV radiation and the constant bombardment of charged particles, creates a charge distribution on the surface of the moon: positive on the illuminated side and negative on the night side. Charge distribution depends on the local lunar time, latitude and the electrical properties of the regolith (the presence of water in the regolith can influence the local distribution of charge). On the day side of Moon near surface layer there exists possibility formation dusty plasma system. Altitude of levitation is depending from size of dust particle and Moon latitude. The distribution of dust particles by size and altitude has estimated with taking into account photoelectrons, electrons and ions of solar wind

  9. A Dynamic Fountain Model for Lunar Dust

    Science.gov (United States)

    Stubbs, T. J.; Vondrak, R. R.; Farrell, W. M.

    2005-01-01

    During the Apollo era of exploration it was discovered that sunlight was scattered at the terminators giving rise to horizon glow and streamers above the lunar surface. This was observed from the dark side of the Moon during sunset and sunrise by both surface landers and astronauts in orbit. These observations were quite unexpected, as the Moon was thought to be a pristine environment with a negligible atmosphere or exosphere. Subsequent investigations have shown that the sunlight was most likely scattered by electrostatically charged dust grains originating from the surface. It has since been demonstrated that this dust population could have serious implications for astronomical observations from the lunar surface. The lunar surface is electrostatically charged by the Moon s large-scale interaction with the local plasma environment and the photoemission of electrons due to solar ultra-violet (UV) light and X-rays. The like-charged surface and dust grains then act to repel each other, such that under certain conditions the dust grains are lifted above the surface. We present a dynamic fountain model which can explain how sub-micron dust is able to reach altitudes of up to approximately 100 km above the lunar surface. Previous static dust levitation models are most applicable to the heavier micron-sized grains in close proximity proximity to the surface, but they cannot explain the presence of extremely light grains at high altitudes. If we relax the static constraint applied to previous models, and instead assume that the grains are in constant motion (under the action of dynamic forces), a new picture emerges for the behavior of sub-micron lunar dust.

  10. Experimental Hypervelocity Dust Impact in Olivine: FIB/TEM Characterization of Micron-Scale Craters with Comparison to Natural and Laser-Simulated Small-Scale Impact Effects

    Science.gov (United States)

    Christoffersen, R.; Loeffler, M. J.; Rahman, Z.; Dukes, C.; IMPACT Team

    2017-01-01

    The space weathering of regoliths on airless bodies and the formation of their exospheres is driven to a large extent by hypervelocity impacts from the high relative flux of micron to sub-micron meteoroids that comprise approximately 90 percent of the solar system meteoroid population. Laboratory hypervelocity impact experiments are crucial for quantifying how these small impact events drive space weathering through target shock, melting and vaporization. Simulating these small scale impacts experimentally is challenging because the natural impactors are both very small and many have velocities above the approximately 8 kilometers-per-second limit attainable by conventional chemical/light gas accelerator technology. Electrostatic "dust" accelerators, such as the one recently developed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS), allow the experimental velocity regime to be extended up to tens of kilometers-per-second. Even at these velocities the region of latent target damage created by each impact, in the form of microcraters or pits, is still only about 0.1 to 10 micrometers in size. Both field-emission analytical scanning electron microscopy (FE-SEM) and advanced field-emission scanning transmission electron microscopy (FE-STEM) are uniquely suited for characterizing the individual dust impact sites in these experiments. In this study, we have used both techniques, along with focused ion beam (FIB) sample preparation, to characterize the micrometer to nanometer scale effects created by accelerated dust impacts into olivine single crystals. To our knowledge this work presents the first TEM-scale characterization of dust impacts into a key solar system silicate mineral using the CCLDAS facility. Our overarching goal for this work is to establish a basis to compare with our previous results on natural dust-impacted lunar olivine and laser-irradiated olivine.

  11. Trends in Mars Thermospheric Density and Temperature Structure Obtained from MAVEN In-situ Datasets: Interpretation Using Global Models

    Science.gov (United States)

    Bougher, Stephen W.; Tolson, Robert H.; Mahaffy, Paul R.; Johnston, Timothy E.; Olsen, Kirk; Bell, Jared M.

    2015-04-01

    The Mars thermosphere-ionosphere-exosphere (TIE) system constitutes the atmospheric reservoir (i.e. available cold and hot planetary neutral and thermal ion species) that regulates present day escape processes from the planet. Without knowledge of the physics and chemistry creating this TIE region and driving its variations (e.g., solar cycle, seasonal), it is not possible to constrain either the short-term or long-term histories of atmosphere escape. The characterization of this upper atmosphere reservoir is one of the major science objectives of the MAVEN mission.We investigate both in-situ Neutral Gas and Ion Mass Spectrometer (NGIMS) neutral densities/temperatures and Accelerometer Experiment (ACC) reaction wheel (RW) derived mass densities/temperatures obtained over the first ~400 orbits. This sampling occurs when periapsis latitudes ranged from about 32° to 74°N periapsis local mean solar times (LMST) ranged from about 15:00 to 06:00; and corresponding periapsis altitudes ranged from ~200 km down to ~150 km. This dayside in-situ sampling lasted until about 17-December-2014, after which the periapsis began moving Southward toward nightside Northern mid-latitudes. During this dayside period, monthly mean solar EUV-UV fluxes corresponded to F10.7 ~ 150-160 at Earth (solar moderate conditions) and the Martian season was approaching perihelion (Ls ~ 205 to 254°).Thermospheric trends (e.g. latitude, local time, diurnal) of extracted densities and inferred temperatures will be compared with corresponding 3-D Mars Global Ionosphere-Thermosphere Model (M-GITM) simulated outputs in order to understand the variations observed, and probe the underlying physical processes responsible. Solar rotation variations in EUV fluxes and their impacts on dayside temperatures will also be examined.

  12. Saturn's Magnetosphere Interaction with Titan for T9 Encounter: 3D Hybrid Modeling and Comparison with CAPS Observations

    Science.gov (United States)

    Lipatov, A. S.; Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Simpson, D. G.

    2011-01-01

    Global dynamics of ionized and neutral gases in the environment of Titan plays an important role in the interaction of Saturn s magnetosphere with Titan. Several hybrid simulations of this problem have already been done (Brecht et al., 2000; Kallio et al., 2004; Modolo et al., 2007a; Simon et al., 2007a, 2007b; Modolo and Chanteur, 2008). Observational data from CAPS for the T9 encounter (Sittler et al., 2009) indicates an absence of O(+) heavy ions in the upstream that change the models of interaction which were discussed in current publications (Kallio et al., 2004; Modolo et al., 2007a; Simon et al., 2007a, 2007b; Ma et al., 2007; Szego et al., 2007). Further analysis of the CAPS data shows very low density or even an absence of H(+) ions in upstream. In this paper we discuss two models of the interaction of Saturn s magnetosphere with Titan: (A) high density of H(+) ions in the upstream flow (0.1/cu cm), and (B) low density of H(+) ions in the upstream flow (0.02/cu cm). The hybrid model employs a fluid description for electrons and neutrals, whereas a particle approach is used for ions. We also take into account charge-exchange and photoionization processes and solve self-consistently for electric and magnetic fields. The model atmosphere includes exospheric H(+), H(2+), N(2+)and CH(4+) pickup ion production as well as an immobile background ionosphere and a shell distribution for active ionospheric ions (M(sub i)=28 amu). The hybrid model allows us to account for the realistic anisotropic ion velocity distribution that cannot be done in fluid simulations with isotropic temperatures. Our simulation shows an asymmetry of the ion density distribution and the magnetic field, including the formation of Alfven wing-like structures. The results of the ion dynamics in Titan s environment are compared with Cassini T9 encounter data (CAPS).

  13. Low Energy Electrons in the Mars Plasma Environment

    Science.gov (United States)

    Link, Richard

    2001-05-01

    The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (< 4 keV) electrons will be modeled using the two-stream electron transport code of Link. The code models both external (solar wind) and internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

  14. High Resolution X-ray Views of Solar System Objects

    Science.gov (United States)

    Branduardi-Raymont, Graziella

    2011-05-01

    Over the last decade Chandra, and XMM-Newton, have revealed the beauty and multiplicity of X-ray emissions in our solar system: high resolution data, in both spectral and spatial domains, have been crucial in disentangling the physical processes at work. The talk will review the main findings in this area at the boundary between astrophysics and planetary science, and will show how the solar system offers `next door’ examples of widespread astrophysical phenomena. Jupiter shows bright X-ray aurorae, arising from the interactions of local and/or solar wind ions, and electrons, with its powerful magnetic environment: the ions undergo charge exchange with atmospheric neutrals and generate soft X-ray line emission, and the electrons give rise to bremsstrahlung X-rays. Chandra's unparalleled spatial resolution has shown how the X-ray footprints of the electrons in the aurorae coincide with the bright FUV auroral oval, indicating that the same electron population is likely to be at the origin of both emissions. Moreover, Jupiter's disk scatters solar X-rays, displaying a spectrum that closely resembles that of solar flares. Saturn has not revealed X-ray aurorae (yet), but its disk X-ray brightness, like Jupiter's, is strictly correlated with the Sun's X-ray output. A bright X-ray spot has also been resolved by Chandra on the eastern ansa of Saturn's rings, and its spectrum suggests an origin in the fluorescent scattering of solar X-rays on the rings icy particles. Both Mars and Venus have X-ray emitting disks and exospheres, which can be clearly resolved at high spectral and spatial resolution. And the Earth has bright X-ray aurorae that have been targets of Chandra observations. Finally, comets, with their extended neutral comae and extremely line-rich X-ray spectra, are spectacular X-ray sources, and ideal probes of the conditions of the solar wind in the Sun's proximity.

  15. A radiative transfer model to treat infrared molecular excitation in cometary atmospheres

    Science.gov (United States)

    Debout, V.; Bockelée-Morvan, D.; Zakharov, V.

    2016-02-01

    The exospheres of small Solar System bodies are now observed with high spatial resolution from space missions. Interpreting infrared spectra of cometary gases obtained with the VIRTIS experiment onboard the Rosetta cometary mission requires detailed modeling of infrared fluorescence emission in optically thick conditions. Efficient computing methods are required since numerous ro-vibrational lines excited by the Sun need to be considered. We propose a new model working in a 3-D environment to compute numerically the local incoming radiation. It uses a new algorithm using pre-defined directions of ray propagation and ray grids to reduce the CPU cost in time with respect to Monte Carlo methods and to treat correctly the sunlight direction. The model is applied to the ν3 bands of CO2 and H2O at 4.3 μ m and 2.7 μ m respectively, and to the CO ∨ (1 → 0) band at 4.7 μ m. The results are compared to the ones obtained by a 1-D algorithm which uses the Escape Probability (EP) method, and by a 3-D ;Coupled Escape Probability; (CEP) model, for different levels of optical thickness. Our results suggest that the total band flux may vary strongly with azimuth for optically thick cases whereas the azimuth average total band flux computed is close to the one obtained with EP. Our model globally predicts less intensity reduction from opacity than the CEP model of Gersch and A'Hearn (Gersch, A.M., A'Hearn, M.F. [2014]. Astrophys. J. 787, 36-56). An application of the model to the observation of CO2, CO and H2O bands in 67/P atmosphere with VIRTIS is presented to predict the evolution of band optical thickness along the mission.

  16. Color variations on Victoria quadrangle: support for the geological mapping

    Science.gov (United States)

    Zambon, F.; Galluzzi, V.; Carli, C.; Giacomini, L.; Massironi, M.; Palumbo, P.; Guzzetta, L.; Mancinelli, P.; Vivaldi, V.; Ferranti, L.; Pauselli, C.; Frigeri, A.; Zusi, M.; Pozzobon, R.; Cremonese, G.; Ferrari, S.; Capaccioni, F.

    2015-10-01

    Mercury is the closest planet to the Sun. Its extreme thermal environment makes it difficult to explore onsite. In 1974, Mariner 10, the first mission dedicated to Mercury, covered 45% of the surface during of the three Hermean flybys [1]. For about 30 years after Mariner 10, no other mission has flownto Mercury. Many unresolved issues need an answer, and in recent years the interest about Mercury has increased. MESSENGER mission contributed to understand Mercury's origin, its surface structure, and the nature of its magnetic field, exosphere, and magnetosphere [1]. The Mercury Dual Imaging System (MDIS) provided a global coverage of Mercury surface with variable spatial resolution. MDIS is equipped with a narrow angle camera (NAC), dedicated to the study of the geology and a wide angle camera (WAC) with 12 filters useful to investigate the surface composition[2]. Mercury has been divided into 15 quadrangles for mapping purposes [3]. The mapping process permits integration of different geological surface information to better understand the planet crust formation and evolution. Merging spectroscopically data is a poorly followed approach in planetary mapping, but it gives additional information about lithological composition, contributing to the construction of a more complete geological map [e.g. 4]. Recently, [5] proposed a first detailed map of all the Victoria quadrangle (H2). Victoria quadrangle is located in a longitude range between 270°E and 360°E and a latitude range of 22.5°N and 65°N,and itwas only partially mapped by Mariner 10 data[3]. Here we investigate the lithological variation by using the MDIS-WAC data to produce a set of color map products which could be asupport to the geological mapping [5]. The future ESA-JAXA mission to Mercury, BepiColombo, will soon contribute to improve the knowledge of Mercury surface composition and geology thanks to the Spectrometer and Imagers for MPO BepiColombo-Integrated Observatory SYStem (SIMBIO-SYS)[6].

  17. Emirates Mars Infrared Spectrometer (EMIRS) Overview from the Emirates Mars Mission

    Science.gov (United States)

    Altunaiji, Eman; Edwards, Christopher; Smith, Michael; Christensen, Philip; AlMheiri, Suhail; Reed, Heather

    2017-04-01

    Emirates Mars Infrared Spectrometer (EMIRS) instrument is one of three scientific instruments aboard the Emirate Mars Mission (EMM), with the name of "Hope". EMM is United Arab Emirates' (UAE) mission to be launched in 2020, with the aim of exploring the dynamics of the atmosphere of Mars on a global scale with sampling on a diurnal and sub-seasonal time-scales. EMM has three scientific instruments selected to provide an improved understanding of circulation and weather in the Martian lower atmosphere as well as the thermosphere and exosphere. The EMIRS instrument is an interferometric thermal infrared spectrometer that is jointly developed by Arizona State University (ASU) and Mohammed Bin Rashid Space Centre (MBRSC), Dubai, UAE. It builds on a long heritage of thermal infrared spectrometers designed, built, and managed, by ASU's Mars Space Flight Facility, including the Thermal Emission Spectrometer (TES), Miniature Thermal Emission Spectrometer (Mini-TES), and the OSIRIS-REx Thermal Emission Spectrometer (OTES). EMIRS operates in the 6-40+ μm range with 5 cm-1 spectral sampling, enabled by a Chemical Vapor-Deposited (CVD) diamond beam splitter and state of the art electronics. This instrument utilizes a 3×3 line array detector and a scan mirror to make high-precision infrared radiance measurements over most of the Martian hemisphere. The EMIRS instrument is optimized to capture the integrated, lower-middle atmosphere dynamics over a Martian hemisphere, using a scan-mirror to make 60 global images per week ( 20 images per orbit) at a resolution of 100-300 km/pixel while requiring no special spacecraft maneuvers.

  18. Reflectance and Emissivity Spectra of Graphite as Potential Darkening Agent for Mercury from the UV to the TIR and its Comparison to Remote Sensing Measurements from MESSENGER and MERTIS on BepiColombo

    Science.gov (United States)

    Maturilli, A.; Helbert, J.; D'Amore, M.; Ferrari, S.; Hiesinger, H.

    2016-12-01

    For long time Mercury was considered a planet very similar to the Moon. Both are small rocky bodies in the inner solar system with thin exospheres and no large scale traces of recent geological activity. However Mercury's surface reflects much less sunlight than the Moon. Trying to explain the reasons for this difference, significant abundances of iron and titanium (and their oxides) were proposed for the Hermean surface. But the NASA MESSENGER instruments found only small abundances of iron, confirming earlier ground-based spectroscopy observations, and virtually no titanium. Therefore neither of the elements can account for this diversity. New analysis of MESSENGER data acquired for the darkest regions of Mercury's surface suggest that the unknown darkening material could be carbon, in particular as the mineral graphite (Peplowski et al., 2016) whose abundance in the darker regions is predicted to be 1 to 3 wt% higher than the surroundings. At the Planetary Spectroscopy Laboratory (PSL) of the Institute of Planetary Research (DLR, Berlin) we measured reflectance spectra for several phase angles of graphite, from UV to TIR spectral range (0.2 to 20 µm). Samples have been measured fresh and then after successive steps of heating at 400°C in vacuum for 8 hours. Following the same procedure, reflectance spectra of Komatiite (chosen as Mercury surface simulant, after Maturilli et al., 2014) was measured alone and mixed with few % of graphite to reproduce the results from Peplowski et al (2016). The results from this experiment can be compared to the data acquired from the MDIS and the MASCS instrument onboard the NASA MESSENGER mission. The same set of samples has been measured in emissivity, in vacuum (board of the ESA BepiColombo Mercury Planetary Orbiter (MPO) scheduled for 2018.

  19. Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

    Science.gov (United States)

    Jasinski, Jamie M.; Slavin, James A.; Raines, Jim M.; DiBraccio, Gina A.

    2017-12-01

    We analyze 94 traversals of Mercury's southern magnetospheric plasma mantle using data from the MESSENGER spacecraft. The mean and median proton number densities in the mantle are 1.5 and 1.3 cm-3, respectively. For sodium number density these values are 0.004 and 0.002 cm-3. Moderately higher densities are observed on the magnetospheric dusk side. The mantle supplies up to 1.5 × 108 cm-2 s-1 and 0.8 × 108 cm-2 s-1 of proton and sodium flux to the plasma sheet, respectively. We estimate the cross-electric magnetospheric potential from each observation and find a mean of 19 kV (standard deviation of 16 kV) and a median of 13 kV. This is an important result as it is lower than previous estimations and shows that Mercury's magnetosphere is at times not as highly driven by the solar wind as previously thought. Our values are comparable to the estimations for the ice giant planets, Uranus and Neptune, but lower than Earth. The estimated potentials do have a very large range of values (1-74 kV), showing that Mercury's magnetosphere is highly dynamic. A correlation of the potential is found to the interplanetary magnetic field (IMF) magnitude, supporting evidence that dayside magnetic reconnection can occur at all shear angles at Mercury. But we also see that Mercury has an Earth-like magnetospheric response, favoring -BZ IMF orientation. We find evidence that -BX orientations in the IMF favor the southern cusp and southern mantle. This is in agreement with telescopic observations of exospheric emission, but in disagreement with modeling.

  20. Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets

    Energy Technology Data Exchange (ETDEWEB)

    Bourrier, V.; Ehrenreich, D. [Observatoire de l’Université de Genève, 51 chemin des Maillettes, 1290 Sauverny (Switzerland); Wit, J. de [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bolmont, E. [Laboratoire AIM Paris-Saclay, CEA/DRF—CNRS—Univ. Paris Diderot—IRFU/SAp, Centre de Saclay, F-91191 Gif-sur-Yvette Cedex (France); Stamenković, V. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Wheatley, P. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Burgasser, A. J [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Delrez, L. [Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE (United Kingdom); Demory, B.-O. [University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012, Bern (Switzerland); Gillon, M.; Jehin, E.; Grootel, V. Van [Institut dAstrophysique et de Géophysique, Université de Liège, Allée du 6 Aout 19C, B-4000 Liège (Belgium); Leconte, J. [Laboratoire dAstrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, F-33615 Pessac (France); Lederer, S. M. [NASA Johnson Space Center, 2101 NASA Parkway, Houston, Texas, 77058 (United States); Lewis, N. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 (United States); Triaud, A. H. M. J. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2017-09-01

    The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could harbor liquid water on their surfaces. Ultraviolet observations are essential to measuring their high-energy irradiation and searching for photodissociated water escaping from their putative atmospheres. Our new observations of the TRAPPIST-1 Ly α line during the transit of TRAPPIST-1c show an evolution of the star emission over three months, preventing us from assessing the presence of an extended hydrogen exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape. However, TRAPPIST-1e to h might have lost less than three Earth oceans if hydrodynamic escape stopped once they entered the habitable zone (HZ). We caution that these estimates remain limited by the large uncertainty on the planet masses. They likely represent upper limits on the actual water loss because our assumptions maximize the X-rays to ultraviolet-driven escape, while photodissociation in the upper atmospheres should be the limiting process. Late-stage outgassing could also have contributed significant amounts of water for the outer, more massive planets after they entered the HZ. While our results suggest that the outer planets are the best candidates to search for water with the JWST , they also highlight the need for theoretical studies and complementary observations in all wavelength domains to determine the nature of the TRAPPIST-1 planets and their potential habitability.

  1. Two Azimuthally Separated Regions of Cusp Ion Injection Observed via Energetic Neutral Atoms

    Science.gov (United States)

    Abe, M.; Taguchi, S.; Collier, M. R.; Moore, T. E.

    2011-01-01

    The low-energy neutral atom (LENA) imager on the IMAGE spacecraft can detect energetic neutral atoms produced by ion injection into the cusp through a charge exchange with the Earth's hydrogen exosphere. We examined the occurrence of the LENA cusp signal during positive IMF B(sub z) in terms of the arrival direction and the IMF clock angle theta(sub CA). Results of statistical analyses show that the occurrence frequency is high on the postnoon side when theta(sub CA) is between approximately 20 degrees and approximately 50 degrees. This is ascribed to ion injection caused by cusp reconnection typical of positive IMF B(sub z). Our results also show that there is another situation of high occurrence frequency, which can be identified with theta(sub CA) of approximately 30 degrees to approximately 80 degrees. When theta(sub CA) is relatively large (60 degrees - 80 degrees), occurrence frequencies are high at relatively low latitudes over a wide extent spanning both prenoon and postnoon sectors. This feature suggests that the ion injection is caused by reconnection at the dayside magnetopause. Its postnoon side boundary shifts toward the prenoon as theta(sub CA) decreases. When theta(sub CA) is less than approximately 50 degrees, the high occurrence frequency exists well inside the prenoon sector, which is azimuthally separated from the postnoon region ascribed to cusp reconnection. The prenoon region, which is thought due to ion injection caused by dayside reconnection, may explain the recent report that proton aurora brightening occurs in the unanticipated prenoon sector of the northern high-latitude ionosphere for IMF B(sub y) greater than 0 and B(sub z) greater than 0.

  2. Astrobiological Journeys to and from the South Polar Sea of Enceladus - Bidirectional Interactions with the Saturn Magmetosphere

    Science.gov (United States)

    Cooper, J. F.; Sittler, E. C.; Lipatov, A. S.; Sturner, S. J.

    2011-12-01

    The spectacularly cryovolcanic moon Enceladus is a major source of plasma for the Saturn magnetosphere via ionization of the ejected molecular species and ice grains. Field-aligned plasma flows from the Enceladus environment visibly impact the moon's magnetic footpoint in Saturn's polar auroral region, while water group and other ions from the moon emissions diffuse radially throughout the magnetosphere and may be the dominant source of oxygen for Titan's oxygen-poor upper atmosphere. But the moon-magnetosphere interaction is bidirectional in the sense that the moon surface is globally exposed to constant irradiation by the returning magnetospheric ions and by energetic electrons from the field-aligned and radially diffusing populations. The returning ion source operates both on global scales of the magnetosphere and locally for highly reactive species produced in the ejecta plume. All of these sources likely combine to produce a highly oxidized global surface layer. Since plasma electrons and ions are cooled by interaction with neutral gas and E-ring ice grains from Enceladus, the moon emissions have a governing effect on the seed populations of energetic particles that irradiate the surface. The proposed subsurface polar sea and transient crustal overturn in the south polar region could bring the polar surface oxidants into contact with hydrocarbons and ammonia to make oxidation product gases contributing to the cryovolcanic jets, a process first proposed by Cooper et al. (Plan. Sp. Sci., 2009). As has been previously suggested for Europa, the oxidants could contribute to enhanced astrobiological potential of Enceladus, perhaps even higher than for Europa where organic hydrocarbons have not yet been directly detected. Unlike Europa, Enceladus shows no sign of an oxygen-dominated exosphere that could otherwise be indicative of extreme surface and interior oxidation inhibiting the detectable survival and evolution of complex organics.

  3. Detectability of molecular gas signatures on Jupiter’s moon Europa from ground and space-based facilities

    Science.gov (United States)

    Paganini, Lucas; Villanueva, Geronimo Luis; Hurford, Terry; Mandell, Avi; Roth, Lorenz; Mumma, Michael J.

    2017-10-01

    Plumes and their effluent material could provide insights into Europa’s subsurface chemistry and relevant information about the prospect that life could exist, or now exists, within the ocean. In 2016, we initiated a strong observational campaign to characterize the chemical composition of Europa’s surface and exosphere using high-resolution infrared spectroscopy. While several studies have focused on the detection of water, or its dissociation products, there could be a myriad of complex molecules released by erupting plumes. Our IR survey has provided a serendipitous search for several key molecular species, allowing a chemical characterization that can aid the investigation of physical processes underlying its surface. Since our tentative water detection, presented at the 2016 DPS meeting, we have continued the observations of Europa during 2017 covering a significant extent of the moon’s terrain and orbital position (true anomaly), accounting for over 50 hr on source. Current analyses of these data are showing spectral features that grant further investigation. In addition to analysis algorithms tailored to the examination of Europan data, we have developed simulation tools to predict the possible detection of molecular species using ground-based facilities like the Keck Observatory, NASA’s Infrared Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA). In this presentation we will discuss the detectability of key molecular species with these remote sensing facilities, as well as expected challenges and future strategies with upcoming spacecrafts such as the James Webb Space Telescope (JWST), the Large UV/Optical/Infrared Surveyor (LUVOIR), and a possible gas spectrometer onboard an orbiter.This work is supported by NASA’s Keck PI Data Award (PI L.P.) and Solar System Observation Program (PI L.P.), and by the NASA Astrobiology Institute through funding awarded to the Goddard Center for Astrobiology (PI M.J.M.).

  4. Observational Constraints on a Pluto Torus of Circumsolar Neutral Gas

    Science.gov (United States)

    Hill, M. E.; Kollmann, P.; McNutt, R. L., Jr.; Smith, H. T.; Bagenal, F.; Brown, L. E.; Elliott, H. A.; Haggerty, D. K.; Horanyi, M.; Krimigis, S. M.; Kusterer, M. B.; Lisse, C. M.; McComas, D. J.; Piquette, M. R.; Sidrow, E. J.; Strobel, D. F.; Szalay, J.; Vandegriff, J. D.; Zirnstein, E.; Ennico Smith, K.; Olkin, C.; Weaver, H. A., Jr.; Young, L. A.; Stern, S. A.

    2015-12-01

    We present the concept of a neutral gas torus surrounding the Sun, aligned with Pluto's orbit, and place observational constraints based primarily on comparison of New Horizons (NH) measurements with a 3-D Monte Carlo model adapted from analogous satellite tori surrounding Saturn and Jupiter. Such a torus, or perhaps partial torus, should result from neutral N2 escaping from Pluto's exosphere. Unlike other more massive planets closer to the Sun, neutrals escape Pluto readily owing, e.g., to the high thermal speed relative to the escape velocity. Importantly, escaped neutrals have a long lifetime due to the great distance from the Sun, ~100 years for photoionization of N2 and ~180 years for photoionization of N, which results from disassociated N2. Despite the lengthy 248-year orbit, these long e-folding lifetimes may allow an enhanced neutral population to form an extended gas cloud that modifies the N2 spatial profile near Pluto. These neutrals are not directly observable by NH but once ionized N2+ or N+ are picked up by the solar wind, reaching ~50 keV, making these pickup ions (PUIs) detectable by NH's Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument. PEPSSI observations analyzed to date may constrain the N2 density; the remaining ~95% of the encounter data, scheduled for downlink in August along with similarly anticipated data from the Solar Wind Around Pluto (SWAP) experiment, should help determine the Pluto outgassing rates. Measurements from SWAP include the solar wind speed, a quantity that greatly enhances PUI studies by enabling us to directly account for the PUI distribution's sensitive dependence on plasma speed. Note that anomalous cosmic ray Si observed at Voyager is overabundant by a factor of ~3000 relative to interstellar composition. This might be related to "outer source" PUIs, but the fact that N2 and Si are indistinguishable in many instruments could mean that N2 is actually driving this apparent Si discrepancy.

  5. The Plasma Environment at Mercury

    Science.gov (United States)

    Raines, James M.; Gershman, Daniel J.; Zurbuchen, Thomas H.; Gloeckler, George; Slavin, James A.; Anderson, Brian J.; Korth, Haje; Krimigis, Stamatios M.; Killen, Rosemary M.; Sarantos, Menalos; hide

    2011-01-01

    Mercury is the least explored terrestrial planet, and the one subjected to the highest flux of solar radiation in the heliosphere. Its highly dynamic, miniature magnetosphere contains ions from the exosphere and solar wind, and at times may allow solar wind ions to directly impact the planet's surface. Together these features create a plasma environment that shares many features with, but is nonetheless very different from, that of Earth. The first in situ measurements of plasma ions in the Mercury space environment were made only recently, by the Fast Imaging Plasma Spectrometer (FIPS) during the MESSENGER spacecraft's three flybys of the planet in 2008-2009 as the probe was en route to insertion into orbit about Mercury earlier this year. Here. we present analysis of flyby and early orbital mission data with novel techniques that address the particular challenges inherent in these measurements. First. spacecraft structures and sensor orientation limit the FIPS field of view and allow only partial sampling of velocity distribution functions. We use a software model of FIPS sampling in velocity space to explore these effects and recover bulk parameters under certain assumptions. Second, the low densities found in the Mercury magnetosphere result in a relatively low signal-to-noise ratio for many ions. To address this issue, we apply a kernel density spread function to guide removal of background counts according to a background-signature probability map. We then assign individual counts to particular ion species with a time-of-flight forward model, taking into account energy losses in the carbon foil and other physical behavior of ions within the instrument. Using these methods, we have derived bulk plasma properties and heavy ion composition and evaluated them in the context of the Mercury magnetosphere.

  6. Detection efficiency of microchannel plates for e{sup −} and π{sup −} in the momentum range from 17.5 to 345 MeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Tulej, M., E-mail: marek.tulej@space.unibe.ch; Meyer, S.; Lüthi, M.; Lasi, D.; Galli, A.; Wurz, P. [Space Research and Planetary Sciences, Physics Institute, University of Bern, CH-3012 Bern (Switzerland); Desorgher, L.; Hajdas, W. [Laboratory of Particle Physics, Paul Scherrer Institute, CH-5232 Villigen (Switzerland); Karlsson, S.; Kalla, L. [Swedish Institute of Space Physics, Space Kampus 1, Kiruna (Sweden)

    2015-08-15

    High-energy e{sup –} and π{sup –} were measured by the multichannel plate (MCP) detector at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The measurements provide the absolute detection efficiencies for these particles: 5.8% ± 0.5% for electrons in the beam momenta range 17.5–300 MeV/c and 6.0% ± 1.3% for pions in the beam momenta range 172–345 MeV/c. The pulse height distribution determined from the measurements is close to an exponential function with negative exponent, indicating that the particles penetrated the MCP material before producing the signal somewhere inside the channel. Low charge extraction and nominal gains of the MCP detector observed in this study are consistent with the proposed mechanism of the signal formation by penetrating radiation. A very similar MCP ion detector will be used in the Neutral Ion Mass (NIM) spectrometer designed for the JUICE mission of European Space Agency (ESA) to the Jupiter system, to perform measurements of the chemical composition of the Galilean moon exospheres. The detection efficiency for penetrating radiation determined in the present studies is important for the optimisation of the radiation shielding of the NIM detector against the high-rate and high-energy electrons trapped in Jupiter’s magnetic field. Furthermore, the current studies indicate that MCP detectors can be useful to measure high-energy particle beams at high temporal resolution.

  7. Mars Planetary Ion Escape: Assessing Transitional Trajectories

    Science.gov (United States)

    Johnson, B. C.

    2016-12-01

    The availability of in situ observations of ions escaping from Mars' atmosphere is vital to descriptions of atmospheric loss, but such point measurements taken by orbiting spacecraft cannot easily differentiate between spatial changes along the spacecraft trajectory and temporal changes, nor can they directly provide information about atmospheric loss rates during Mars' long history. Numerical models are therefore crucial to crystalizing understanding of ion escape processes. One such category are test particle models that release non-interacting ions into background electric and magnetic fields and then calculate ion trajectories and loss rates. To date, such models have focused on the collisionless regime. Another approach is to include collisions between the particles, the Direct Simulation Monte Carlo (DSMC) approach. We present the results of the first fully three dimensional collisional Mars ion DSMC model capable of peering deep into the collionsional atmosphere, beneath the ionospheric peak, i.e., the ion version of the Adaptive Mesh Particle Simulator (AMPS) configured for Mars. Multiple model runs are performed, each with a different cutoff altitude below which collisions are included. Escape rates of O+ are calculated for each run, providing both the asymptotic escape rate as the cutoff altitude extends into the exosphere and also an idea of the altitude range for which collisions must be included for the results to reasonably converge to this value. In other words, how low can a collisionless model go? Furthermore, these results can be used to interpret satellite data of planetary ions, helping to determine if the spacecraft is in the upflow or outflow regime. In other words, how low can observations be used for measuring the loss of planetary ions to deep space? This entire process is repeated a second time, with the first set of runs corresponding to solar minimum input parameters, and the second set of runs corresponding to solar maximum parameters.

  8. Aeronomy, a 20th Century emergent science: the role of solar Lyman series

    Directory of Open Access Journals (Sweden)

    G. Kockarts

    Full Text Available Aeronomy is, by definition, a multidisciplinary science which can be used to study the terrestrial atmosphere, as well as any planetary atmosphere and even the interplanetary space. It was officially recognized in 1954 by the International Union of Geodesy and Geophysics. The major objective of the present paper is to show how aeronomy developed since its infancy. The subject is so large that a guide-line has been chosen to see how aeronomy affects our atmospheric knowledge. This guideline is the solar Lyman alpha radiation which has different effects in the solar system. After a short description of the origins of aeronomy the first observations of this line are summarized since the beginning of the space age. Then the consequences of these observations are analyzed for the physics and chemistry of the neutral terrestrial atmosphere. New chemical processes had to be introduced, as well as new transport phenomena. Solar Lyman alpha also influences the structure of the Earth’s ionosphere, particularly the D-region. In the terrestrial exosphere, solar Lyman alpha scattered resonantly by atomic hydrogen is at present the only way to estimate this constituent in an almost collisionless medium. Since planetary atmospheres also contain atomic hydrogen, the Lyman alpha line has been used to deduce the abundance of this constituent. The same is true for the interplanetary space where Lyman alpha observations can be a good tool to determine the concentration. The last section of the paper presents a question which is intended to stimulate further research in aeronomy.

    Key words. Atmospheric composition and structure (middle atmosphere – composition and chemistry; thermosphere – composition and chemistry – history of geophysics (atmospheric sciences

  9. The DTM-2013 thermosphere model

    Directory of Open Access Journals (Sweden)

    Bruinsma Sean

    2015-01-01

    Full Text Available Aims – The Drag Temperature Model (DTM is a semi-empirical model describing the temperature, density, and composition of the Earth’s thermosphere. DTM2013 was developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction project (ATMOP. It is evaluated and compared with DTM2009, the pre-ATMOP benchmark, and the Committe on Space Research (COSPAR reference model for atmospheric drag JB2008. Methods – The total density data used in this study, including the high-resolution CHAMP, GRACE and GOCE data, cover the 200–900 km altitude range and all solar activities. DTM2013 was constructed with the data assimilated in DTM2009, but with more GRACE data, and low-altitude GOCE data in particular. The solar activity proxy, F10.7 in DTM2009, has been replaced with F30. The bias and precision of the models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors. Results – This evaluation shows that DTM2013 is the least biased and most precise model for the data that were assimilated. Comparison to independent density data shows that it is also the most accurate model overall. It is a significant improvement over DTM2009 under all conditions and at all altitudes, but the largest improvements are obtained at low altitude thanks to GOCE data. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents.

  10. Evaluation of the DTM-2009 thermosphere model for benchmarking purposes

    Directory of Open Access Journals (Sweden)

    Guijarro Nuria

    2012-06-01

    Full Text Available Aims: The Drag Temperature Model (DTM is a semi-empirical model describing the temperature, density, and composition of the Earth’s thermosphere. DTM2009 and DTM2000, and the COSPAR reference models NRLMSISE-00 and JB2008, are evaluated in order to establish benchmark values for new DTM models that will be developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction (ATMOP project. Methods: The total density data used in this study, including the high-resolution CHAMP and GRACE data, cover the 200–1000 km altitude range and all solar activities. DTM2009, using an improved DTM2000 algorithm, was constructed with most data assimilated in DTM2000, but also with CHAMP and GRACE data. The bias and precision of the four models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors. Results: This evaluation shows that DTM2009 is the most precise model for the data that were assimilated. Comparison to independent density data shows that it is also the most accurate model overall and a significant improvement over DTM2000 under all conditions. JB2008 is the most accurate model below 300 km, JB2008 and DTM2009 perform best in the 300–500 km altitude range, whereas above 500 km NRLMSISE-00 and DTM2009 are most accurate. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents. Specific errors in DTM2009, for example related to the employed solar activity proxy, will be fixed in the next model release, DTM2012. A specific analysis under geomagnetic storm conditions is outside the scope of the present paper.

  11. The Plasma Environment at Enceladus and Europa Compared

    Science.gov (United States)

    Rymer, Abigail; Persoon, Ann; Morooka, Michiko; Heuer, Steven; Westlake, Joseph H.

    2017-10-01

    The plasma environment near Enceladus is complex, as revealed during 16 encounters of the Cassini spacecraft. The well documented Enceladus plumes create a dusty, asymmetric exosphere in which electrons can attach to small ice particles - forming anions, and negatively charged nanograins and dust - to the extent that cations can be the lightest charged particles present and, as a result, the dominant current carriers. Several instruments on the Cassini spacecraft are able to measure this environment in both expected and unexpected ways. Cassini Plasma Spectrometer (CAPS) is designed and calibrated to measure the thermal plasma ions and electrons and also measures the energy/charge of charged nanograins when present. Cassini Radio Plasma Wave Sensor (RPWS) measures electron density as derived from the ‘upper hybrid frequency’ which is a function of the total free electron density and magnetic field strength and provides a vital ground truth measurement for Cassini calibration when the density is sufficiently high for it to be well measured. Cassini Langmuir Probe (LP) measures the electron density and temperature via direct current measurement, and both CAPS and LP can provide estimates for the spacecraft potential which we compare. The plasma environment near Europa is similarly complex and, although not so comprehensively equipped and hampered by the non-deployment of its high gain antenna, the Galileo spacecraft made similar measurements during 9 Europa flybys and recent observations have suggested that, like Enceladus, Europa might have active plume activity. We present a detailed comparison of data from the Cassini and Galileo sensors in order to assess the plasma environment observed by the different instruments, discuss what is consistent and otherwise, and the implications for the plasma environment at Enceladus and Europa in the context of work to date as well as implications for future studies.

  12. Water Ice Radiolytic O2, H2, and H2O2 Yields for Any Projectile Species, Energy, or Temperature: A Model for Icy Astrophysical Bodies

    Science.gov (United States)

    Teolis, B. D.; Plainaki, C.; Cassidy, T. A.; Raut, U.

    2017-10-01

    O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self-consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major challenge is the wide variation of O2 radiolysis yields between laboratory experiments, ranging over 4 orders of magnitude from 5 × 10-7 to 5 × 10-3 molecules/eV for different particles and energies. We revisit decades of laboratory data to solve this long-standing puzzle, finding an inverse projectile range dependence in the O2 yields, due to preferential O2 formation from an 30 Å thick oxygenated surface layer. Highly penetrating projectile ions and electrons with ranges ≳30 Å are therefore less efficient at producing O2 than slow/heavy ions and low-energy electrons (≲ 400 eV) which deposit most energy near the surface. Unlike O2, the H2O2 yields from penetrating projectiles fall within a comparatively narrow range of (0.1-6) × 10-3 molecules/eV and do not depend on range, suggesting that H2O2 forms deep in the ice uniformly along the projectile track, e.g., by reactions of OH radicals. We develop an analytical model for O2, H2, and H2O2 yields from pure water ice for electrons and singly charged ions of any mass and energy and apply the model to estimate possible O2 source rates on several icy satellites. The yields are upper limits for icy bodies on which surface impurities may be present.

  13. 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.

  14. Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets

    Science.gov (United States)

    Bourrier, V.; de Wit, J.; Bolmont, E.; Stamenković, V.; Wheatley, P. J.; Burgasser, A. J.; Delrez, L.; Demory, B.-O.; Ehrenreich, D.; Gillon, M.; Jehin, E.; Leconte, J.; Lederer, S. M.; Lewis, N.; Triaud, A. H. M. J.; Van Grootel, V.

    2017-09-01

    The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could harbor liquid water on their surfaces. Ultraviolet observations are essential to measuring their high-energy irradiation and searching for photodissociated water escaping from their putative atmospheres. Our new observations of the TRAPPIST-1 Lyα line during the transit of TRAPPIST-1c show an evolution of the star emission over three months, preventing us from assessing the presence of an extended hydrogen exosphere. Based on the current knowledge of the stellar irradiation, we investigated the likely history of water loss in the system. Planets b to d might still be in a runaway phase, and planets within the orbit of TRAPPIST-1g could have lost more than 20 Earth oceans after 8 Gyr of hydrodynamic escape. However, TRAPPIST-1e to h might have lost less than three Earth oceans if hydrodynamic escape stopped once they entered the habitable zone (HZ). We caution that these estimates remain limited by the large uncertainty on the planet masses. They likely represent upper limits on the actual water loss because our assumptions maximize the X-rays to ultraviolet-driven escape, while photodissociation in the upper atmospheres should be the limiting process. Late-stage outgassing could also have contributed significant amounts of water for the outer, more massive planets after they entered the HZ. While our results suggest that the outer planets are the best candidates to search for water with the JWST, they also highlight the need for theoretical studies and complementary observations in all wavelength domains to determine the nature of the TRAPPIST-1 planets and their potential habitability.

  15. Low-Altitude Emission of Energetic Neutral Atoms: Multiple Interactions and Energy Loss

    Science.gov (United States)

    LLera, K.; Goldstein, J.; McComas, D. J.; Valek, P. W.

    2017-10-01

    Low-altitude emissions (LAEs) are the energetic neutral atom (ENA) signature of ring current ions precipitating along the magnetic field to an altitude of 200-800 km. This altitude region is considered to be "optically thick" because ring current ions undergo multiple charge changing interactions (MCCIs) with Earth's dense oxygen exosphere. While each interaction involves an energy loss of 36 eV, no prior study has determined the accumulated energy lost by 1-100 keV H+ emerging as LAEs. We have developed a 2-D model with a geomagnetic dipole that captures the net effects in energy loss and pitch angle evolution as a result of MCCIs without the computational requirements of a full Monte Carlo simulation. Dependent on the amount of latitudinal migration, the energy loss is greater than 20% for ions below 60 keV for equatorward moving particles (30 keV for poleward). Since the ENA travels ballistically across a geomagnetic dipole, upon reionization, ion velocity along the local field increases (antiparallel in the northern hemisphere). Redirecting the particle upward through MCCIs is most effective during poleward ENA motion. The net effect is to redirect precipitating ions (below 2,500 km) to eventually emerge from the optically thick region either as an ion or ENA. Precipitation is a joint ion-neutral process, affecting both the energy and pitch angle distribution through the transverse motion of ENA segments in a converging field. For particles that enter the MCCI regime, the energy loss and evolution of the pitch angle distribution must be considered within a realistic magnetic field.

  16. On the classification of comet plasma tails

    Science.gov (United States)

    Mozhenkov, E. R.; Vaisberg, O. L.

    2017-07-01

    The investigation of plasma tails of comets is an important part of comet research. Different classifications of plasma tails of comets are proposed. Plasma acceleration in the tails is investigated in sufficient detail. Several cometary forms are explained. Plasma tails of Mars and Venus were observed during the first studies of these planets. They are associated with the capture of ionized atoms and exosphere molecules by the solar wind magnetized plasma flow. Distinct plasma tails of Mars and Venus are caused by the mass loading of the solar wind with heavy ions. It was shown that the transverse dimension of the tails of Mars, Venus, and comets can be quite accurately determined by production rate of the obstacle to the solar wind flow. While plasma tails of Mars and Venus are investigated by in situ measurements from spacecraft, observations of comet tails from the Earth make it possible to see the entire object under study and to monitor changes in its structure. A certain similarity of cometary and planetary tails can be explained by the nonmagnetic nature of both types of bodies. Thus, it is reasonable to suppose that investigations of plasma tails of comets can supplement the information obtained by in situ methods of the study of the planets. In this paper, plasma tails of comets, presumably analogous to the plasma tails of Mars and Venus, have been identified on modern photographs of comets (more than 1500 photographs viewed). Only quasi-steady laminar tails are considered. They are divided into two types: double structures and outflows. The paper attempts to define the 3D structure of double structures and to determine certain characteristics of outflows.

  17. Interaction of Solar Wind and Magnetic Anomalies - Modelling from Moon to Mars

    Science.gov (United States)

    Alho, Markku; Kallio, Esa; Wedlund, Cyril Simon; Wurz, Peter

    2015-04-01

    The crustal magnetic anomalies on both the Moon and Mars strongly affect the local plasma environment. On the Moon, the impinging solar wind is decelerated or deflected when interacting with the magnetic field anomaly, visible in the lunar surface as energetic neutral atom (ENA) emissions or as reflected protons, and may play a part in the space weathering of the lunar soil. At Mars, the crustal magnetic fields have been shown to be associated with, e.g., enhanced electron scale heights and modified convection of ionospheric plasma, resulting in the plasma environment being dominated by crustal magnetic fields up to altitudes of 400km. Our previous modelling work suggested that Hall currents are a dominant feature in a Moon-like magnetic anomaly interaction at scales at or below the proton inertial length. In this work we study the solar wind interaction with magnetic anomalies and compare the plasma environments of a Moon-like anomaly with a Mars-like anomaly by introducing an ionosphere and an exosphere to probe the transition from an atmosphere-less anomaly interaction to an ionospheric one. We utilize a 3D hybrid plasma model, in which ions are modelled as particles while electrons form a charge-neutralizing massless fluid. The hybrid model gives a full description of ion kinetics and associated plasma phenomena at the simulation region ranging from instabilities to possible reconnection. The model can thus be used to interpret both in-situ particle and field observations and remotely-sensed ENA emissions. A self-consistent ionosphere package for the model is additionally in development.

  18. The DTM-2013 thermosphere model

    Science.gov (United States)

    Bruinsma, Sean

    2015-02-01

    Aims - The Drag Temperature Model (DTM) is a semi-empirical model describing the temperature, density, and composition of the Earth's thermosphere. DTM2013 was developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction project (ATMOP). It is evaluated and compared with DTM2009, the pre-ATMOP benchmark, and the Committe on Space Research (COSPAR) reference model for atmospheric drag JB2008. Methods - The total density data used in this study, including the high-resolution CHAMP, GRACE and GOCE data, cover the 200-900 km altitude range and all solar activities. DTM2013 was constructed with the data assimilated in DTM2009, but with more GRACE data, and low-altitude GOCE data in particular. The solar activity proxy, F10.7 in DTM2009, has been replaced with F30. The bias and precision of the models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors. Results - This evaluation shows that DTM2013 is the least biased and most precise model for the data that were assimilated. Comparison to independent density data shows that it is also the most accurate model overall. It is a significant improvement over DTM2009 under all conditions and at all altitudes, but the largest improvements are obtained at low altitude thanks to GOCE data. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents.

  19. Evaluation of the DTM-2009 thermosphere model for benchmarking purposes

    Science.gov (United States)

    Bruinsma, Sean L.; Sánchez-Ortiz, Noelia; Olmedo, Estrella; Guijarro, Nuria

    2012-06-01

    Aims: The Drag Temperature Model (DTM) is a semi-empirical model describing the temperature, density, and composition of the Earth's thermosphere. DTM2009 and DTM2000, and the COSPAR reference models NRLMSISE-00 and JB2008, are evaluated in order to establish benchmark values for new DTM models that will be developed in the framework of the Advanced Thermosphere Modelling and Orbit Prediction (ATMOP) project. Methods: The total density data used in this study, including the high-resolution CHAMP and GRACE data, cover the 200-1000 km altitude range and all solar activities. DTM2009, using an improved DTM2000 algorithm, was constructed with most data assimilated in DTM2000, but also with CHAMP and GRACE data. The bias and precision of the four models is evaluated by comparing to the observations according to a metric, which consists of computing mean, RMS, and correlation. Secondly, the residuals are binned, which procedure aids in revealing specific model errors. Results: This evaluation shows that DTM2009 is the most precise model for the data that were assimilated. Comparison to independent density data shows that it is also the most accurate model overall and a significant improvement over DTM2000 under all conditions. JB2008 is the most accurate model below 300 km, JB2008 and DTM2009 perform best in the 300-500 km altitude range, whereas above 500 km NRLMSISE-00 and DTM2009 are most accurate. The precision of JB2008 decreases with altitude, which is due to its modeling of variations in local solar time and seasons in particular of the exospheric temperature rather than modeling these variations for the individual constituents. Specific errors in DTM2009, for example related to the employed solar activity proxy, will be fixed in the next model release, DTM2012. A specific analysis under geomagnetic storm conditions is outside the scope of the present paper.

  20. Solar wind interaction with the Martian upper atmosphere: Crustal field orientation, solar cycle, and seasonal variations

    Science.gov (United States)

    Dong, Chuanfei; Bougher, Stephen W.; Ma, Yingjuan; Toth, Gabor; Lee, Yuni; Nagy, Andrew F.; Tenishev, Valeriy; Pawlowski, Dave J.; Combi, Michael R.; Najib, Dalal

    2015-09-01

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ˜3.3 and ˜1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [(O2+ and/or O2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas O2+ and O2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  1. Ultra low frequency waves at Venus: Observations by the Venus Express spacecraft

    Science.gov (United States)

    Fränz, M.; Echer, E.; Marques de Souza, A.; Dubinin, E.; Zhang, T. L.

    2017-10-01

    The generation of waves with low frequencies (below 100 mHz) has been observed in the environment of most bodies in the solar system and well studied at Earth. These waves can be generated either upstream of the body in the solar wind by ionization of planetary exospheres or ions reflected from a bow shock or in the magnetosheath closer to the magnetic barrier. For Mars and Venus the waves may have special importance since they can contribute to the erosion of the ionopause and by that enhance atmospheric escape. While over the past years many case studies on wave phenomena observed at Venus have been published most statistical studies have been based on magnetic observations only. On the other hand the generation mechanisms and transport of these waves through the magnetosphere can only be quantified using both magnetic and particle observations. We use the long time observations of Venus Express (2006-2014) to determine the predominant processes and transport parameters. First we demonstrate the analysis methods in four case studies, then we present a statistical analysis by determining transport ratios from the complete Venus Express dataset. We find that Alfvenic waves are very dominant (>80%) in the solar wind and in the core magnetosheath. Fast waves are observed mainly at the bow shock (around 40%) but also at the magnetic barrier where they may be most important for the energy transfer into the ionosphere. Their occurrence in the magnetotail may be an artifact of the detection of individual plasma jets in this region. Slow mode waves are rarely dominating but occur with probability of about 10% at the bow shock and in the pile-up-region. Mirror mode waves have probability <20% in the magnetosheath slightly increasing towards the pile-up-boundary.

  2. NASA's Solar System Exploration Research Virtual Institute: Merging Science and Exploration

    Science.gov (United States)

    Pendleton, Y. J.; Schmidt, G. K.; Bailey, B. E.; Minafra, J. A.

    2016-01-01

    NASA's Solar System Exploration Research Virtual Institute (SSERVI) represents a close collaboration between science, technology and exploration, and was created to enable a deeper understanding of the Moon and other airless bodies. SSERVI is supported jointly by NASA's Science Mission Directorate and Human Exploration and Operations Mission Directorate. The institute currently focuses on the scientific aspects of exploration as they pertain to the Moon, Near Earth Asteroids (NEAs) and the moons of Mars, but the institute goals may expand, depending on NASA's needs, in the future. The 9 initial teams, selected in late 2013 and funded from 2014-2019, have expertise across the broad spectrum of lunar, NEA, and Martian moon sciences. Their research includes various aspects of the surface, interior, exosphere, near-space environments, and dynamics of these bodies. NASA anticipates a small number of additional teams to be selected within the next two years, with a Cooperative Agreement Notice (CAN) likely to be released in 2016. Calls for proposals are issued every 2-3 years to allow overlap between generations of institute teams, but the intent for each team is to provide a stable base of funding for a five year period. SSERVI's mission includes acting as a bridge between several groups, joining together researchers from: 1) scientific and exploration communities, 2) multiple disciplines across a wide range of planetary sciences, and 3) domestic and international communities and partnerships. The SSERVI central office is located at NASA Ames Research Center in Mountain View, CA. The administrative staff at the central office forms the organizational hub for the domestic and international teams and enables the virtual collaborative environment. Interactions with geographically dispersed teams across the U.S., and global partners, occur easily and frequently in a collaborative virtual environment. This poster will provide an overview of the 9 current US teams and

  3. Detecting negative ions on board small satellites

    Science.gov (United States)

    Lepri, S. T.; Raines, J. M.; Gilbert, J. A.; Cutler, J.; Panning, M.; Zurbuchen, T. H.

    2017-04-01

    Recent measurements near comets, planets, and their satellites have shown that heavy ions, energetic neutral atoms, molecular ions, and charged dust contain a wealth of information about the origin, evolution, and interaction of celestial bodies with their space environment. Using highly sensitive plasma instruments, positively charged heavy ions have been used to trace exospheric and surface composition of comets, planets, and satellites as well as the composition of interplanetary and interstellar dust. While positive ions dominate throughout the heliosphere, negative ions are also produced from surface interactions. In fact, laboratory experiments have shown that oxygen released from rocky surfaces is mostly negatively charged. Negative ions and negatively charged nanograins have been detected with plasma electron analyzers in several different environments (e.g., by Cassini and Rosetta), though more extensive studies have been challenging without instrumentation dedicated to negative ions. We discuss an adaptation of the Fast Imaging Plasma Spectrometer (FIPS) flown on MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) for the measurement of negatively charged particles. MESSENGER/FIPS successfully measured the plasma environment of Mercury from 2011 until 2015, when the mission ended, and has been used to map multiple ion species (H+ through Na+ and beyond) throughout Mercury's space environment. Modifications to the existing instrument design fits within a 3U CubeSat volume and would provide a low mass, low power instrument, ideal for future CubeSat or distributed sensor missions seeking, for the first time, to characterize the contribution of negative particles in the heliospheric plasmas near the planets, moons, comets, and other sources.

  4. Low Energy Electrons in the Mars Plasma Environment

    Science.gov (United States)

    Link, Richard

    2001-01-01

    The ionosphere of Mars is rather poorly understood. The only direct measurements were performed by the Viking 1 and 2 landers in 1976, both of which carried a Retarding Potential Analyzer. The RPA was designed to measure ion properties during the descent, although electron fluxes were estimated from changes in the ion currents. Using these derived low-energy electron fluxes, Mantas and Hanson studied the photoelectron and the solar wind electron interactions with the atmosphere and ionosphere of Mars. Unanswered questions remain regarding the origin of the low-energy electron fluxes in the vicinity of the Mars plasma boundary. Crider, in an analysis of Mars Global Surveyor Magnetometer/Electron Reflectometer measurements, has attributed the formation of the magnetic pile-up boundary to electron impact ionization of exospheric neutral species by solar wind electrons. However, the role of photoelectrons escaping from the lower ionosphere was not determined. In the proposed work, we will examine the role of solar wind and ionospheric photoelectrons in producing ionization in the upper ionosphere of Mars. Low-energy (electrons will be modeled using the two-stream electron transport code of Link. The code models both external (solar wind) and internal (photoelectron) sources of ionization, and accounts for Auger electron production. The code will be used to analyze Mars Global Surveyor measurements of solar wind and photoelectrons down to altitudes below 200 km in the Mars ionosphere, in order to determine the relative roles of solar wind and escaping photoelectrons in maintaining plasma densities in the region of the Mars plasma boundary.

  5. Astrobiological Journeys to and from the South Polar Sea of Enceladus - Bidirectional Interactions with the Saturn Magnetosphere

    Science.gov (United States)

    Cooper, John F.; Sittler, Edward C.; Lipatov, Alexander S.; Sturner, Steven J.

    2012-01-01

    The spectacularly cryovolcanic moon Enceladus is a major source of plasma for the Saturn magnetosphere via ionization of the ejected molecular species and ice grains. Field-aligned plasma flows from the Enceladus environment visibly impact the moon's magnetic footpoint in Saturn's polar auroral region, while water group and other ions from the moon emissions diffuse radially throughout the magnetosphere and may be the dominant source of oxygen for Titan's oxygen-poor upper atmosphere. But the moon-magnetosphere interaction is bidirectional in the sense that the moon surface is globally exposed to constant irradiation by the returning magnetospheric ions and by energetic electrons from the field-aligned and radially diffusing populations. The returning ion source operates both on global scales of the magnetosphere and locally for highly reactive species produced in the ejecta plume. All of these sources likely combine to produce a highly oxidized global surface layer. Since plasma electrons and ions are cooled by interaction with neutral gas and E-ring ice grains from Enceladus, the moon emissions have a governing effect on the seed populations of energetic particles that irradiate the surface. The proposed subsurface polar sea and transient crustal overturn in the south polar region could bring the polar surface oxidants into contact with hydrocarbons and ammonia to make oxidation product gases contributing to the cryovolcanic jets, a process first proposed by Cooper et al. (Plan. Sp. Sci., 2009). As has been previously suggested for Europa, the 'oxidants could contribute to enhanced astrobiological potential of Enceladus, perhaps even higher than for Europa where organic hydrocarbons have not yet been directly detected. Unlike Europa, Enceladus shows no sign of an oxygen-dominated exosphere that could otherwise be indicative of extreme surface and interior oxidation inhibiting the detectable survival and evolution of complex organics.

  6. Plasma IMS Composition Measurements for Europa and the Other Galilean Moons

    Science.gov (United States)

    Sittler, Edward; Cooper, John; Hartle, Richard; Lipatov, Alexander; Mahaffy, Paul; Paterson, William; Pachalidis, Nick; Coplan, Mike; Cassidy, Tim

    2010-05-01

    sputtering of the surfaces of Europa and Ganymede has been shown to be representative of the surface composition [2,3]. Level 2 science on surface geology and composition can then be further enhanced by addition of the following: 3D Ion Neutral Mass Spectrometer (INMS), 3D plasma electron spectrometer (ELS), and hot plasma energetic particle instrument. The measurement approach is to alternate between times measuring pickup ions and times measuring plasma and magnetic field parameters along the spacecraft trajectory. By measuring the pickup ion energy, arrival direction and mass-per-charge, the ion can be traced back along the ejection trajectory to the approximate area of origin if the 3-D electric field and magnetic field are known. In situ observations of plasma flow velocities and vector magnetic fields can be used to determine the local convective electric field (E = -VXB) along the spacecraft trajectory. By combining this information with models of the magnetospheric interaction with Europa [3,4], one can generate 3D maps of the electric and magnetic field and compute the trajectories of the pickup ions back to the surface or exospheric points of origin. In the case of Ganymede there is the additional complexity of its own internal dipole magnetic field, while Io's volcanic activity introduces the complexity of a highly structured denser atmosphere. Callisto with its less globally extended exosphere will have a simpler interaction than for Europa (i.e., more like our moon). We will discuss these differences in light of the above proposed technique. Finally, the INMS observations and neutral exosphere models are needed to estimate production rates of pickup ions. The hot plasma measurements are needed to correct for sputtering rates which can be time dependent and electron plasma observations for electron impact ionization rates. Instrument characteristics, field-of-view requirements, modes of operation and effects of radiation on instrument functionality will be

  7. Dust particles investigation for future Russian lunar missions.

    Science.gov (United States)

    Dolnikov, Gennady; Horanyi, Mihaly; Esposito, Francesca; Zakharov, Alexander; Popel, Sergey; Afonin, Valeri; Borisov, Nikolay; Seran, Elena; Godefroy, Michel; Shashkova, Inna; Kuznetsov, Ilya; Lyash, Andrey; Vorobyova, Elena; Petrov, Oleg; Lisin, Evgeny

    One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Meteorites bombardment has accompanied by shock-explosive phenomena, disintegration and mix of the lunar soil in depth and on area simultaneously. As a consequence, the lunar soil has undergone melting, physical and chemical transformations. Recently we have the some reemergence for interest of Moon investigation. The prospects in current century declare USA, China, India, and European Union. In Russia also prepare two missions: Luna-Glob and Luna-Resource. Not last part of investigation of Moon surface is reviewing the dust condition near the ground of landers. Studying the properties of lunar dust is important both for scientific purposes to investigation the lunar exosphere component and for the technical safety of lunar robotic and manned missions. The absence of an atmosphere on the Moon's surface is leading to greater compaction and sintering. Properties of regolith and dust particles (density, temperature, composition, etc.) as well as near-surface lunar exosphere depend on solar activity, lunar local time and position of the Moon relative to the Earth's magneto tail. Upper layers of regolith are an insulator, which is charging as a result of solar UV radiation and the constant bombardment of charged particles, creates a charge distribution on the surface of the moon: positive on the illuminated side and negative on the night side. Charge distribution depends on the local lunar time, latitude and the electrical properties of the regolith (the presence of water in the regolith can influence the local distribution of charge). On light side of Moon near surface layer there exists possibility formation dusty plasma system. Altitude of levitation is depending from size of dust particle and Moon latitude. The distribution dust particle by size and altitude has estimated with taking into account photoelectrons, electrons and ions of solar wind, solar

  8. Dynamic Response of the Environment at the Moon (DREAM): Providing Opportunities for Students and Teachers to Learn About the Solar-lunar Environmental Connection

    Science.gov (United States)

    Bleacher, L.; Weir, H. M.; Twu, Y.; Farrell, W. M.; Gross, N. A.

    2009-12-01

    The Dynamic Response of the Environment at the Moon (DREAM) team is one of seven teams comprising the NASA Lunar Science Institute. DREAM’s goal is to reveal, advance, and test the extremes of the solar-lunar environmental connection. DREAM’s education and outreach (E/PO) program is focused on student and teacher participation with scientists. The primary component of the DREAM E/PO program is two Lunar Extreme Workshops (LEWs) and the supporting materials developed for each LEW. The workshops will bring together scientists and modelers from the DREAM team with advanced high school and/or community college students and their teachers. The LEWs will allow student/teacher participants to interact directly with the scientists and to experience the process of science in action. Participation in LEWs and pre-LEW training will expose students to science, technology, engineering, and math (STEM) careers and engage them in learning new STEM content. During the two LEWs, the new, integrated lunar models developed by the DREAM team will be tested using extreme environmental drivers. These extreme events include: 1) solar storms and human excursion into Shackleton Crater and 2) human activity/lunar excavation and impact cratering. Although the LEWs will be complex in nature, the students and teachers will receive extensive pre-LEW training via access to online curricular resources already in development and Webinars with DREAM science team members, during which the students/teachers will get to know the team members and put their new knowledge into context. The curricular materials will include resources and activities pertaining to space weather, plasma, electricity, circuits, magnetism, magnetospheres, exospheres, impact cratering, and modeling. The activities are being mapped to the National Science Education Standards and the American Association for the Advancement of Science’s Benchmarks for Science Literacy. Students will be encouraged to read and review

  9. Nitrates in SNCs: Implications for the nitrogen cycle on Mars

    Science.gov (United States)

    Grady, Monica M.; Wright, I. P.; Franchi, I. A.; Pillinger, C. T.

    1993-01-01

    Nitrogen is the second most abundant constituent of the Martian atmosphere, after CO2, present at a level of ca. 2.7 percent. Several authors have hypothesized that earlier in the planet's history, nitrogen was more abundant, but has been removed by processes such as exospheric loss from the atmosphere. However, an alternative sink for atmospheric nitrogen is the regolith; model calculations have predicted that, via the formation of NOx, HNO2 and HNO3 in the lower layers of the Martian atmosphere, the regolith might trap nitrite and nitrate anions, leading to the build-up of involatile nitrates. Integrated over 4.5 x 10(exp 9) yr, such a mechanism would contribute the equivalent of a layer of nitrates up to 0.3 cm thick distributed across the Martian surface. Features in thermal emission spectra of the surface of Mars have been interpreted tentatively as emanating from various anions (carbonates, bicarbonates, sulphates, etc.), and the presence of nitrates has also been addressed as a possibility. The identification of carbonates in SCN meteorites has allowed inferences to be drawn concerning the composition and evolution of the Martian atmosphere in terms of its carbon isotope systematics; if nitrites, nitrates, or other nitrogen-bearing salts could be isolated from SNC's, similar conclusions might be possible for an analogous nitrogen cycle. Nitrates are unstable, being readily soluble in water, and decomposed at temperatures between 50 C and 600 C, depending on composition. Any nitrates present in SNC's might be removed during ejection from the planet's surface, passage to Earth, or during the sample's terrestrial history, by weathering etc. The same might have been said for carbonates, but pockets of shock-produced glass (lithology C) from within the EET A79001 shergottite and bulk samples of other SNC contain this mineral, which did apparently survive. Nitrates occurring within the glassy melt pockets of lithology C in EET A79001 might likewise be protected

  10. Numerical study of ionospheric response to perturbations and interaction with spacecraft instruments

    Science.gov (United States)

    Imtiaz, Nadia

    This PhD thesis presents numerical studies of the ionosphere dynamics and of the interaction between ionospheric plasma and spacecraft instruments. The main results of my research are the following: A first study presents a simple model to account for magnetic field perturbations in response to geophysical phenomena such as earthquakes. Following an earthquake, large neutral density and velocity perturbations reach altitudes of 150 -- 350 km, where significant coupling between the neutral atmosphere and the ionosphere occurs. Photoionization and collisional friction between plasma and the neutral exosphere then results in a rapid variation in ionospheric plasma parameters. This in turn leads to the generation of two types of waves: shear Alfven and the compressional modes. Variations in the total electron content (TEC) are also computed for the ion acoustic mode and the compressional mode by considering density perturbations along and transverse to the magnetic field. The second part of my work considers the interaction between ionospheric plasma and spacecraft instruments under different plasma conditions. This is achieved by simulating space plasma interaction with two different particle sensors; namely, DEMETER's Segmented Langmuir probe (SLP) and JOULEII Suprathermal Ion imager (SII). The current characteristics of the SLP are computed with particle in cell (PIC) code, under different plasma conditions. The current collected by each segment varies with the orientation of the plasma flow velocity, the plasma composition and with the orientation of the magnetic field. For validation of the simulations, the computed characteristics are compared with DEMETER in situ measurements. Simulation results are found to be in good agreement with measurements. Finally, the impact of plasma flow on ion velocity distributions in the vicinity of the SII sensor aperture is numerically investigated. It is observed that the plasma flow modifies the electrostatic sheath and affects

  11. Io Eclipse/Volcanic Eruption

    Science.gov (United States)

    1997-01-01

    This image was acquired while Io was in eclipse (in Jupiter's shadow) during Galileo's eighth orbit, and reveals several dynamic processes. The most intense features are red, while glows of lesser intensity are yellow or green, and very faint glows appear blue in this color-coded image. The small red or yellow spots mark the sites of high-temperature magma erupting onto the surface in lava flows or lava lakes.This image reveals a field of bright spots near Io's sub-Jupiter point (right-hand side of image). The sub-Jupiter hemisphere always faces Jupiter just as the Moon's nearside always faces Earth. There are extended diffuse glows on the equatorial limbs or edges of the planet (right and left sides). The glow on the left is over the active volcanic plume Prometheus, but whereas Prometheus appears to be 75 kilometers (46.6 miles) high in reflected light, here the diffuse glow extends about 800 kilometers (497 miles) from Io's limb. This extended glow indicates that gas or small particles reach much greater heights than the dense inner plume. The diffuse glow on the right side reaches a height of 400 kilometers (249 miles), and includes a prominence with a plume-like shape. However, no volcanic plume has been seen at this location in reflected light. This type of observation is revealing the relationships between Io's volcanism, atmosphere and exosphere.Taken on May 6, 1997, north is toward the top. The image was taken with the clear filter of the solid state imaging (CCD) system on NASA's Galileo spacecraft at a range of 1.8 million kilometers (1.1 million miles).The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational

  12. The future of VIS-IR hyperspectral remote sensing for the exploration of the solar system

    Science.gov (United States)

    Filacchione, Gianrico

    2017-06-01

    In the last 30 years our understanding of the Solar System has greatly advanced thanks to the introduction of VIS-IR imaging spectrometers which have provided hyperspectral views of planets, satellites, asteroids, comets and rings. By providing moderate resolution images and reflectance spectra for each pixel at the same time, these instruments allow to elaborate spectral-spatial models for very different targets: when used to observe surfaces, hyperspectral methods permit to retrieve endmembers composition (minerals, ices, organics, liquids), mixing state among endmembers (areal, intimate, intraparticle), physical properties (particle size, roughness, temperature) and to correlate these quantities with geological and morphological units. Similarly, morphological, dynamical and compositional studies of gaseous and aerosol species can be retrieved for planetary atmospheres, exospheres and auroras. To achieve these results, very different optical layouts, detectors technologies and observing techniques have been adopted in the last decades, going from very large and complex payloads, like ISM (IR Spectral Mapper) on russian mission Phobos to Mars and NIMS (Near IR Mapping Spectrometer) on US Galileo mission to Jupiter, which were the first hyperspectral imagers to flow aboard planetary missions, to more recent compact and performing experiments. The future of VIS-IR hyperspectral remote sensing is challenging because the complexity of modern planetary missions drives towards the realization of increasingly smaller, lighter and more performing payloads able to survive in harsh radiation and planetary protected environments or to operate from demanding platforms like landers, rovers and cubesats. As a development for future missions, one can foresee that apart instruments designed around well-consolidated optical solutions relying on prisms or gratings as dispersive elements, a new class of innovative hyperspectral imagers will rise: recent developments in

  13. Compact Ion and Neutral Mass Spectrometer with Ion Drifts, Temperatures and Neutral Winds

    Science.gov (United States)

    Paschalidis, Nikolaos

    2016-07-01

    In situ measurements of atmospheric neutral and ion composition and density, temperatures, ion drifts and neutral winds, are in high demand to study the dynamics of the ionosphere-theremosphere-mesosphere system. This paper presents a compact Ion and Neutral Mass Spectrometer (INMS) with impended ion drifts and temperature, and neutral winds capability for in situ measurements of ions and neutrals H, He, N, O, N2, O2. The mass resolution M/dM is approximately 10 at an incoming energy range of 0-20eV. The goal is to resolve ion drifts in the range 0 to 3000m/sec with a resolution better than 50m/sec, and neutral winds in the range of 0 to 1000m/sec with similar resolution. For temperatures the goal is to cover a dynamic range of 0 to 5000K. The INMS is based on front end optics for ions and neutrals, pre acceleration, gated time of flight, top hat ESA, MCP detectors and compact electronics. The instrument is redundant for ions and neutrals with the ion and neutral sensor heads on opposite sides and with full electronics in the middle. The ion front end includes RPA for temperature scanning and neutral front end includes angular modulation and thermionic ionization and ion blocking grids. The electronics include fast electric gating, TOF electronics, TOF binning and C&DH digital electronics. The data package includes 400 mass bins each for ions and neutrals and key housekeeping data for instrument health and calibration. The data sampling can be commanded from 0.1 to 10 sec with 1sec nominal setting. The instrument has significant onboard storage capability and a data compression scheme. The mass spectrometer version of the instrument has been flown on the Exocube mission. The instrument occupied 1.5U volume, weighed only 560 g and required nominal power of 1.6W The ExoCube mission was designed to acquire global knowledge of in-situ densities of [H], [He], [O] and H+, He+, O+ in the upper ionosphere and lower exosphere in combination with incoherent scatter radar and

  14. Earth Observation from Space - The Issue of Environmental Sustainability

    Science.gov (United States)

    Durrieu, Sylvie; Nelson, Ross F.

    2013-01-01

    that they're rare event, space launches may be benign, but study is merited on upper stratospheric and exospheric layers given the chemical activity associated with rocket combustion by-products. (3) Minimization of Type II error should be considered in situations where minimization of Type I error greatly hampers or precludes our ability to correct the environmental condition being studied. (4) In certain situations, airborne collects may be less expensive and more environmentally benign, and comparative studies should be done to determine which path is wisest. (5) International cooperation and data sharing will reduce instrument and launch costs and mission redundancy. Given fiscal concerns of most of the major space agencies e e.g. NASA, ESA, CNES e it seems prudent to combine resources.

  15. History of the Inner Solar System According to the Lunar Cold Traps

    Science.gov (United States)

    Crider, D. H.; Stubbs, T. J.; Vondrak, R. R.

    2006-12-01

    There are regions near the poles of the Moon that are permanently shaded from the Sun's light, are extremely cold (T volatiles over geologic timescales. Thus, the contents of the cold traps act as a record of the history of volatiles in the Solar System in the neighborhood of Earth. By taking core samples within the regions of permanent shadow, one can study the inventory of volatiles on the Moon for as long as that region has been shaded from sunlight, which is typically about 2-3 Gyr. There is no other record currently known to extend as far back in time for determining the volatile inventory in the vicinity of the Earth. There are two potential sources of water on the Moon: (1) episodic cometary impacts; and (2) steady production from chemical interactions between solar wind protons and oxygen in the lunar regolith. Water from these sources can migrate through the lunar exosphere to the cold traps. However, the two sources would produce very different stratigraphy in the cold traps, even after they are modified by space weathering processes. After a cometary impact, there would be a relatively pure water ice deposit in the cold traps. The varying contents and total number of ice layers will be indicative of the composition, size distribution, and impact frequency of comets on the Moon. Since the Moon has neither a significant atmosphere nor a global magnetic field, the solar wind flow is able to impinge directly on the lunar surface. Most of the incident hydrogen is lost from the Moon in steady state; however, the interaction can produce water vapor. The molecules can hop on ballistic trajectories around the Moon before being lost by photodissociation or photoionization. A small fraction of the water (4%) is able to reach the cold trap of the permanently shadowed regions before being lost from the Moon. This water can accumulate and get mixed in with the regolith over geologic timescales, holding information about the migration process and solar wind

  16. BepiColombo: Exploring Mercury

    Science.gov (United States)

    Geelen, K.; Novara, M.; Fugger, S.; Benkhoff, J.

    2014-04-01

    investigation of its interior, surface,exosphere and magnetosphere. In addition, instrumentation onboard BepiColombo will be used to test Einstein's theory of general relativity. Major effort was put into optimizing the scientific return of the mission by defining a payload complement such that individual measurements can be interrelated and complement each other. This paper gives an in-depth overview of BepiColombo spacecraft composite and the mission profile. It describes the suite of scientific instruments on board of the two BepiColombo spacecraft and the science goals of the mission. This paper gives an overview of the mission, describes the science case together with the payload suite as well as the latest status of the spacecraft development.

  17. Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process

    Science.gov (United States)

    Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard

    2014-01-01

    Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may

  18. Radial transport from the Io plasma torus: driven from the inside out or outside in?

    Science.gov (United States)

    Morgenthaler, J. P.; Marconi, M.; Oliversen, R. J.; Woodward, R. C., Jr.

    2016-12-01

    The Io plasma torus (IPT) is much more massive than it should be assuming radial transport was driven by centrifugally driven interchange instability. Two competing hypotheses have been proposed that provide the necessary impounding effect to radial transport of plasma: velocity shear impound and ring current impound. The velocity shear impound hypothesis suggests that the region of subcorotational plasma seen at the outer edge of the IPT impounds the progress of outward-moving flux tubes and processes near the IPT, such as Rayleigh-Taylor instabilities, would govern mass loss from the IPT ("inside out"). The ring current impound mechanism suggests that a population of energetic electrons on the inner edge of the ring current are distributed in energy and density in just the right way to balance the outward pressure of IPT material and processes in the magnetotail, such as reconnection after plasmoid release, would inject energetic particles that would perturb the ring current and let IPT material leak out ("outside in"). In support of the ring current impound mechanism, Louarn et al. (2014) found that roughly half of the time Galileo was sensitive to detecting them, energetic particle injections were coincident with Jovian hectometeric radio radiation (HOM), associated with auroral activity, and new bursts of narrow-band kilometric radiation (nKOM), associated with plasma leaving the vicinity of the IPT. We present new analyses of a large database of ground-based observations of Io's exosphere in [OI] 6300A. Using the IPT model of Smyth & Marconi (1998, 2000), Oliversen et al. (2001) showed the [OI] flux is a reliable proxy for the thermal electron density at Io's position. The Smyth & Marconi model (triangles in Figure) describes Io's [OI] flux well on most nights, except the two for which we have contemporaneous coverage with that of Louarn et al. (2014). These nights show strong evidence of missing mass from the IPT. We suggest that our observations can be used

  19. Cluster and THEMIS observations of the magnetosphere dayside boundaries in preparation for the SMILE mission

    Science.gov (United States)

    Escoubet, C. P.; Dimmock, A. P.; Walsh, B.; Sibeck, D. G.; Berchem, J.; Nykyri, K.; Turc, L.; Read, A.; Branduardi-Raymont, G.; Wang, C.; Sembay, S.; Kuntz, K. D.; Dai, L.; Li, L.; Donovan, E.; Spanswick, E.; Laakso, H. E.; Zheng, J.; Rebuffat, D.

    2016-12-01

    Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a novel self-standing mission, in collaboration between ESA and Chinese Academy of Science. Its objective is to observe the solar wind-magnetosphere coupling via simultaneous in situ solar wind/magnetosheath plasma and magnetic field measurements, soft X-Ray images of the magnetosheath and polar cusps, and UV images of global auroral distributions. The observations of the cusps and magnetosheath with the X-ray imager are possible through the relatively recent discovery of solar wind charge exchange (SWCX) X-ray emission, first observed at comets, and subsequently found to occur in the vicinity of the Earth's magnetosphere. In preparation for the mission, we need to determine the cusp's morphology, motion and in situ properties (density, velocity, temperature) that are expected to be observed by the spacecraft. To do so, we have selected a series of cusp crossings by the Cluster spacecraft that can be used to simulate X-ray emissions across the width of the cusp for different IMF orientations. In view of the well-known cusp ion dispersions, we expect that X ray emissions peak near the equatorial boundary of the cusp for southward IMF Bz, but near the poleward boundary of the cusp for northward IMF Bz. We also employ Cluster cusp observations during storms to predict X-ray emissions to be expected for periods of high solar wind fluxes. In addition, we use THEMIS observations from January 2008 to July 2015 for moderate (nsw*vsw 4.9x10^8 /cm^2s) solar wind fluxes to investigate X-rays emitted by the magnetosheath and to determine their variation as a function of distance from the subsolar point along the Sun-Earth line and along the flanks of the magnetosphere. We will show that high solar wind fluxes greatly enhance soft X-ray emissions, not only because solar wind fluxes increases but also because the emission region moves deeper within the Earth's exosphere.

  20. Serpentine and the chemical evolution of the earth's mantle

    Science.gov (United States)

    Ruepke, L.; Phipps Morgan, J.; Hort, M.; Connolly, J.; Ranero, C.

    2003-04-01

    Hydration and dehydration of oceanic lithosphere play an important role in element recycling at convergent margins. Most studies agree that subduction related recycling is necessary to explain some aspects of the mantle's chemical evolution. However, some of these recycling processes are not yet well understood, for example (1) OIB type lavas sometimes show a radiogenic 206Pb/204Pb component commonly termed HIMU whose origin is yet to be exactly determined. (2) What is the fate of rare gases during subduction? Does a previously proposed 'subduction barrier' exist and prevent deep recycling of all rare gases, so that todays atmosphere's content reflects the total of degassed rare gases? Here we explore the potential impact of slab serpentinization and deserpentinization processes on arc-melting and on water, U, Pb, and noble gas recycling into the deep mantle. We examine the consequences of a scenario in which bend-faulting between the outer rise and trench axis creates the conduits for seawater to reach and react with cold lithospheric mantle to serpentinize it. If this process occurs, then the incoming lithosphere will typically contain ˜500m of altered sediments, ˜6km of partially hydrated oceanic crust, and ˜20-55km of partially serpentinized slab mantle. Our thermomechanical modelling implies strong deep recycling (30-90%) of the slab's chemical water, depending upon slab age and subduction rate. Possible global geochemical consequences of this scenario are: 1) At current subduction rates, 0.5-1.5 oceans of water would be recycled past the arc-melting region into the deeper mantle during the past Ga. ) Since 0.3%, 1%, and 3% of the exosphere's Ne, Ar, and Xe are dissolved in the oceans, this implies that at present rates ˜0.02, ˜0.06, and ˜0.2 'atmospheres' of Ne, Ar, and Xe, respectively, would have been recycled into the mantle during the past 4 Ga. These numbers imply that dissolved rare gases were transported at bulk-seawater concentrations during

  1. MOMA and other next-generation ion trap mass spectrometers for planetary exploration

    Science.gov (United States)

    Arevalo, R. D., Jr.; Brinckerhoff, W. B.; Getty, S.; Mahaffy, P. R.; van Amerom, F. H. W.; Danell, R.; Pinnick, V. T.; Li, X.; Grubisic, A.; Southard, A. E.; Hovmand, L.; Cottin, H.; Makarov, A.

    2016-12-01

    Since the 1970's, quadrupole mass spectrometer (QMS) systems have served as low-risk, cost-efficient means to explore the inner and outer reaches of the solar system. These legacy instruments have interrogated the compositions of the lunar exosphere (LADEE), surface materials on Mars (MSL), and the atmospheres of Venus (Pioneer Venus), Mars (MAVEN) and outer planets (Galileo and Cassini-Huygens). However, the in situ detection of organic compounds on Mars and Titan, coupled with ground-based measurements of amino acids in meteorites and a variety of organics in comets, has underlined the importance of molecular disambiguation in the characterization of high-priority planetary environments. The Mars Organic Molecule Analyzer (MOMA) flight instrument, centered on a linear ion trap, enables the in situ detection of volatile and non-volatile organics, but also the characterization of molecular structures through SWIFT ion isolation/excitation and tandem mass spectrometry (MSn). Like the SAM instrument on MSL, the MOMA investigation also includes a gas chromatograph (GC), thereby enabling the chemical separation of potential isobaric interferences based on retention times. The Linear Ion Trap Mass Spectrometer (LITMS; PI: William Brinckerhoff), developed to TRL 6 via the ROSES MatISSE Program, augments the core MOMA design and adds: expanded mass range (from 20 - 2000 Da); high-temperature evolved gas analysis (up to 1300°C); and, dual polarity detector assemblies (supporting the measurement of negative ions). The LITMS instrument will be tested in the field in 2017 through the Atacama Rover Astrobiology Drilling Studies (ARADS; PI: Brian Glass) ROSES PSTAR award. Following on these advancements, the Advanced Resolution Organic Molecule Analyzer (AROMA; PI: Ricardo Arevalo Jr.), supported through the ROSES PICASSO Program, combines a highly capable MOMA/LITMS-like linear ion trap and the ultrahigh resolution CosmOrbitrap mass analyzer developed by a consortium of five

  2. Multiple Excitation Regimes in Jupiter’s Polar Aurorae

    Science.gov (United States)

    Trafton, Laurence M.

    2017-10-01

    Since the Voyager epoch, it has been known that the thermospheres of all the outer planets are heated to a temperature over 3 times higher than can be explained by solar EUV (Yelle & Miller 2000). The dominant heat source is still an open question. Without this knowledge, one cannot understand the structure, energy balance, and seasonal evolution of outer planet upper atmospheres. Majeed et al. (2009) suggest that the main ionospheric heat source driving the thermospheric flow at high Jovian latitudes is Joule currents resulting from the frictional motion of the ions relative to the neutrals, while particle precipitation dominates the heating of the auroral ovals at exospheric altitudes. However, since the diffuse emission interior to the oval is not directly connected to a source in the magnetosphere, and vice versa, separate processes may drive the heating in the auroral oval and the zone within. Because the latter’s open field lines expose it to “space weather”, it is subject to thermospheric heating by the solar wind, coronal mass ejections, and reconnection in the Jovian magnetotail.H3+ plays an important role in the cooling and stabilizing of hydrogenic planetary thermospheres (Miller et al. 2000). For Jupiter's hot upper atmosphere, above the homopause at ~1 µbar, H3+ appears to be the dominant coolant, so that the local heating rate may be estimated by measuring the H3+ emission flux. Consequently, the morphology and spectrum of the H3+ emission flux should be heavily influenced by, and so provide the clearest signature of, the unknown heating process. A study of Jupiter’s H3+ emission may therefore help to isolate and constrain that dominant process. Towards that end, we surveyed Jupiter's northern and southern auroral zones near pre-opposition quadrature on May 11 and 12, 2009, by obtaining emission line spectra between 3-4 microns at Keck II with NIRSPEC. The southern spectra resolve at least three contrarily excited H3+ emission spectra

  3. Experimental investigation of the radiation shielding efficiency of a MCP detector in the radiation environment near Jupiter's moon Europa

    Science.gov (United States)

    Tulej, M.; Meyer, S.; Lüthi, M.; Lasi, D.; Galli, A.; Piazza, D.; Desorgher, L.; Reggiani, D.; Hajdas, W.; Karlsson, S.; Kalla, L.; Wurz, P.

    2016-09-01

    Neutral Ion Mass spectrometer (NIM) is one of the instruments in the Particle Environmental Package (PEP) designed for the JUICE mission of ESA to the Jupiter system. NIM, equipped with a sensitive MCP ion detector, will conduct detailed measurements of the chemical composition of Jovian icy moons exospheres. To achieve high sensitivity of the instrument, radiation effects due to the high radiation background (high-energy electrons and protons) around Jupiter have to be minimised. We investigate the performance of an Al-Ta-Al composite stack as a potential shielding against high-energy electrons. Experiments were performed at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The facility delivers a particle beam containing e-, μ- and π- with momentum from 17.5 to 345 MeV/c (Hajdas et al., 2014). The measurements of the radiation environment generated during the interaction of primary particles with the Al-Ta-Al material were conducted with dedicated beam diagnostic methods and with the NIM MCP detector. In parallel, modelling studies using GEANT4 and GRAS suites were performed to identify products of the interaction and predict ultimate fluxes and particle rates at the MCP detector. Combination of experiment and modelling studies yields detailed characterisation of the radiation fields produced by the interaction of the incident e- with the shielding material in the range of the beam momentum from 17.5 to 345 MeV/c. We derived the effective MCP detection efficiency to primary and secondary radiation and effective shielding transmission coefficients to incident high-energy electron beam in the range of applied beam momenta. This study shows that the applied shielding attenuates efficiently high-energy electrons. Nevertheless, owing to nearly linear increase of the bremsstrahlung production rate with incident beam energy, above 130 MeV their detection rates measured by the MCP

  4. Deduction of the rates of radial diffusion of protons from the structure of the Earth's radiation belts

    Energy Technology Data Exchange (ETDEWEB)

    Kovtyukh, Alexander S. [Moscow State Univ. (Russian Federation). Skobeltsyn Inst. of Nuclear Physics

    2016-07-01

    From the data on the fluxes and energy spectra of protons with an equatorial pitch angle of α{sub 0} ∼ 90 during quiet and slightly disturbed (Kp≤2) periods, I directly calculated the value D{sub LL}, which is a measure of the rate of radial transport (diffusion) of trapped particles. This is done by successively solving the systems (chains) of integrodifferential equations which describe the balance of radial transport/acceleration and ionization losses of low-energy protons of the stationary belt. This was done for the first time. For these calculations, I used data of International Sun-Earth Explorer 1 (ISEE-1) for protons with an energy of 24 to 2081 keV at L = 2-10 and data of Explorer-45 for protons with an energy of 78.6 to 872 keV at L = 2-5. Ionization losses of protons (Coulomb losses and charge exchange) were calculated on the basis of modern models of the plasmasphere and the exosphere. It is shown that for protons with μ from ∝0.7 to ∝7 keV nT{sup -1} at L ∼ 4.5-10, the functions of D{sub LL} can be approximated by the following equivalent expressions: D{sub LL} ∼ 4.9 x 10{sup -14}μ{sup -4.1}L{sup 8.2} or D{sub LL} ∼ 1.3 x 10{sup 5}(EL){sup -4.1} or D{sub LL} ∼ 1.2 x 10{sup -9}f{sub d}{sup -4.1}, where f{sub d} is the drift frequency of the protons (in mHz), D{sub LL} is measured in s{sup -1}, E is measured in kiloelectronvolt and μ is measured in kiloelectronvolt per nanotesla. These results are consistent with the radial diffusion of particles under the action of the electric field fluctuations (pulsations) in the range of Pc6 and contradict the mechanism of the radial diffusion of particles under the action of sudden impulses (SIs) of the magnetic field and also under the action of substorm impulses of the electric field. During magnetic storms D{sub LL} increases, and the expressions for D{sub LL} obtained here can change completely.

  5. XMM-Newton Observations of Solar Wind Charge Exchange Emission

    Science.gov (United States)

    Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

  6. Experimental investigation of the radiation shielding efficiency of a MCP detector in the radiation environment near Jupiter’s moon Europa

    Energy Technology Data Exchange (ETDEWEB)

    Tulej, M., E-mail: marek.tulej@space.unibe.ch [Space Research and Planetary Sciences, Physics Institute, University of Bern, CH-3012 Bern (Switzerland); Meyer, S.; Lüthi, M.; Lasi, D.; Galli, A.; Piazza, D. [Space Research and Planetary Sciences, Physics Institute, University of Bern, CH-3012 Bern (Switzerland); Desorgher, L.; Reggiani, D.; Hajdas, W. [Laboratory of Particle Physics, Paul Scherrer Institute, CH-5232, Villigen (Switzerland); Karlsson, S.; Kalla, L. [Swedish Institute of Space Physics, Space Kampus 1, Kiruna (Sweden); Wurz, P. [Space Research and Planetary Sciences, Physics Institute, University of Bern, CH-3012 Bern (Switzerland)

    2016-09-15

    Neutral Ion Mass spectrometer (NIM) is one of the instruments in the Particle Environmental Package (PEP) designed for the JUICE mission of ESA to the Jupiter system. NIM, equipped with a sensitive MCP ion detector, will conduct detailed measurements of the chemical composition of Jovian icy moons exospheres. To achieve high sensitivity of the instrument, radiation effects due to the high radiation background (high-energy electrons and protons) around Jupiter have to be minimised. We investigate the performance of an Al–Ta–Al composite stack as a potential shielding against high-energy electrons. Experiments were performed at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute, Villigen, Switzerland. The facility delivers a particle beam containing e{sup −}, μ{sup −} and π{sup −} with momentum from 17.5 to 345 MeV/c (Hajdas et al., 2014). The measurements of the radiation environment generated during the interaction of primary particles with the Al–Ta–Al material were conducted with dedicated beam diagnostic methods and with the NIM MCP detector. In parallel, modelling studies using GEANT4 and GRAS suites were performed to identify products of the interaction and predict ultimate fluxes and particle rates at the MCP detector. Combination of experiment and modelling studies yields detailed characterisation of the radiation fields produced by the interaction of the incident e{sup −} with the shielding material in the range of the beam momentum from 17.5 to 345 MeV/c. We derived the effective MCP detection efficiency to primary and secondary radiation and effective shielding transmission coefficients to incident high-energy electron beam in the range of applied beam momenta. This study shows that the applied shielding attenuates efficiently high-energy electrons. Nevertheless, owing to nearly linear increase of the bremsstrahlung production rate with incident beam energy, above 130 MeV their

  7. Deduction of the rates of radial diffusion of protons from the structure of the Earth's radiation belts

    Directory of Open Access Journals (Sweden)

    A. S. Kovtyukh

    2016-11-01

    Full Text Available From the data on the fluxes and energy spectra of protons with an equatorial pitch angle of α0 ≈ 90° during quiet and slightly disturbed (Kp ≤ 2 periods, I directly calculated the value DLL, which is a measure of the rate of radial transport (diffusion of trapped particles. This is done by successively solving the systems (chains of integrodifferential equations which describe the balance of radial transport/acceleration and ionization losses of low-energy protons of the stationary belt. This was done for the first time. For these calculations, I used data of International Sun–Earth Explorer 1 (ISEE-1 for protons with an energy of 24 to 2081 keV at L = 2–10 and data of Explorer-45 for protons with an energy of 78.6 to 872 keV at L = 2–5. Ionization losses of protons (Coulomb losses and charge exchange were calculated on the basis of modern models of the plasmasphere and the exosphere. It is shown that for protons with μ from  ∼ 0.7 to ∼ 7 keV nT−1 at L ≈ 4.5–10, the functions of DLL can be approximated by the following equivalent expressions: DLL ≈ 4.9 × 10−14μ−4.1L8.2 or DLL ≈ 1.3 × 105(EL−4.1 or DLL ≈ 1.2 × 10−9fd−4.1, where fd is the drift frequency of the protons (in mHz, DLL is measured in s−1, E is measured in kiloelectronvolt and μ is measured in kiloelectronvolt per nanotesla. These results are consistent with the radial diffusion of particles under the action of the electric field fluctuations (pulsations in the range of Pc6 and contradict the mechanism of the radial diffusion of particles under the action of sudden impulses (SIs of the magnetic field and also under the action of substorm impulses of the electric field. During magnetic storms DLL increases, and the expressions for DLL obtained here can change completely.

  8. Investigation of near-surface lunar dust transport in the laboratory

    Science.gov (United States)

    Sternovsky, Zoltan; Horanyi, Mihaly; Gruen, Eberhard; Robertson, Scott; Wang, Xu; Dove, Adrienne; Munsat, Tobin; Poppe, Andrew; Duncan, Nicole; Drake, Keith; Auer, Siegfried

    The lunar surface is a natural dusty plasma laboratory. The solar UV radiation and the solar wind charge the surface and differential charging due to light/shadow boundaries may enhance the electrostatic field intensity locally. The lunar surface is also exposed to the continual bombardment by interplanetary dust particles with an estimated influx of mass at about 5103 kg/day and impact speed ¿ 2 km/s. Besides a small impact plasma cloud, the micrometeoroid impacts also generate secondary ejecta particles with an estimated mass yield of 10e3 that form a permanently present dust exosphere about the Moon. The combination of these processes may be responsible for a mobilization and lofting of small grains from the surface to explain historical data sets from in situ and remote sensing observations that indicate the presence of lofted dust populations, possibly reaching high altitudes over the lunar surface. Our laboratory has over a decade long history of simulating the lunar surface environment and the charging and dynamics of dust. The recent work include: 1) the dust charging and the mobilization of dust pile on negatively biased surface exposed to low density plasma. Individual grains can lift from the surface and move outward from the pile to transform the pile of dust into a ring shape. 2) The development of a strong UV source using Xe excimer lamps that can generate sufficient photoelectron emission to create a photoelectron sheath. 3) Development of a 3 MV dust accelerator facility to study the generation of impact plasmas and the charging of the surface in the vicinity of the impact. The accelerator will be able to provide particles with speeds up to 50 km/s. 4) The development of the Electrostatic Lunar Dust Analyzer instrument to measure the abundance, charge, size and velocity of dust particles mobilized near the lunar surface. The instrument employs an array of wire electrodes, each connected to sensitive electronics to measure the induced charge from a

  9. Superthermal electrons at Mars: Photoelectrons, solar wind electrons, and dust storm influences

    Science.gov (United States)

    Xu, Shaosui

    Mars is unique in the solar system in terms of its interaction with solar wind because it lacks of a significant intrinsic global magnetic field but possesses localized strong crustal fields. This interaction results in a very complex magnetic topology at Mars so that superthermal electrons, mainly including photoelectrons and solar wind electrons, can be distinctively important for such a complicated planetary space environment. These energetic electrons (1-1000 electron volts) can carry and rapidly redistribute energy along the magnetic field lines. They are also a reliable tool to deduce the Martian magnetic topology, which is critical to understand the electromagnetic dynamics of the Martian space environment. The investigation methodology involves both data analysis and modeling. This dissertation mainly investigates three topics of superthermal electrons at Mars. (1) This dissertation confirms that the long-lived influence of Martian low-altitude dust storms on high-altitude photoelectron fluxes is common for a wide range of energy and pitch angles and determines that this effect originates from the thermosphere-ionosphere source region of the photoelectrons, rather than at exospheric altitudes at or above MGS. Through simulations, the results suggest that the global dust storm altered the photoelectron fluxes by causing CO2 to be the dominant species at a much larger altitude range than usual. (2) Because the integral of the production rate above the superthermal electron exobase is about the same for all solar zenith angles, quite counterintuitively, it is found, observationally and numerically/theoretically, that the high-altitude photoelectron fluxes are quite independent of solar zenith angle. (3) Based on the energy spectral (flux against energy) difference between photoelectrons and solar wind electrons, a statistical approach is taken to distinguish the two populations and also allows us to quantify the occurrence rate of solar wind electron

  10. Radio astronomy with the European Lunar Lander: Opening up the last unexplored frequency regime

    Science.gov (United States)

    Klein Wolt, Marc; Aminaei, Amin; Zarka, Philippe; Schrader, Jan-Rutger; Boonstra, Albert-Jan; Falcke, Heino

    2012-12-01

    The Moon is a unique location in our solar system and provides important information regarding the exposure to free space that is essential for future human space exploration to mars and beyond. The active broadband (100 kHz-100 MHz) tripole antenna now envisaged to be placed on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the Moon, that are essential for future lunar human and science exploration. In addition, the Lunar South Pole provides an excellent opportunity for radio astronomy. Placing a single radio antenna in an eternally dark crater or behind a mountain at the South (or North) pole would potentially provide perfect shielding from man-made radio interference (RFI), absence of ionospheric distortions, and high temperature and antenna gain stability that allows detection of the 21 cm wave emission from pristine hydrogen formed after the Big Bang and into the period where the first stars formed. A detection of the 21 cm line from the Moon at these frequencies would allow for the first time a clue on the distribution and evolution on mass in the early universe between the Epoch of Recombination and Epoch of Reionization (EoR). Next to providing a cosmological breakthrough, a single lunar radio antenna would allow for studies of the effect of solar flares and coronal mass ejections (CMEs) on the solar wind at distances close to Earth (space weather) and would open up the study of low frequency radio events (flares and pulses) from planets such as Jupiter and Saturn, which are known to emit bright (kJy-MJy) radio emission below 30 MHz (Jester and Falcke, 2009). Finally, a single radio antenna on the lunar lander would pave the way for a future large lunar radio interferometer; not only will it demonstrate the possibilities for lunar radio science and open up the

  11. [Challenges, knowledge, decisions in the context of sustainable development].

    Science.gov (United States)

    Benachenhou, A

    1992-01-01

    This work explores challenges to sustainable development, identifies various currents of thought in the social sciences that are of potential relevance in the search for strategies to achieve sustainable development, and offers some reflections on the decision processes involved in selecting development strategies. 4 major challenges to sustainable development are identified. In the 1st place, the fundamental equilibrium of the exosphere is menaced by the expansion of industrial activity, with major ecological problem that of nonrecyclable waste which pollute the ecosystem. The concentration of carbon dioxide in the atmosphere is 1 example. The irreversibility of some effects of human activity is becoming clearer with time. A 2nd challenge is the arising from the intrinsic risks of scientific and technological development. The examples of nuclear energy and genetic manipulation demonstrate the dangers and ethical problems of allowing technological progress to occur without adequate societal control. A 3rd challenge is that of mastery of the organization and use of knowledge so that technological progress can be marshalled to reduce poverty and inequality. The 4th challenge is that of demographic growth, which accentuates poverty and inequality and aggravates pressure on resources. 3 recent currents of thought in the social sciences, all stressing interdisciplinarity, may contribute to understanding the long term modifications needed for achieving sustainable development. Among systemic approached, the thermodynamic theory of economic processes attempts to take into account the irreversible character of expenditures of energy and raw materials, while other theories examine the complexity of system interactions and the limitations of a purely quantitative approach. Decision theory may become an essential component of reflection on technological choices because of its demonstration that the criteria of rational choice differ in the cases of risk and of uncertainty

  12. Neutral escape at Mars induced by the precipitation of high-energy protons and hydrogen atoms of the solar wind origin

    Science.gov (United States)

    Shematovich, Valery I.

    2017-04-01

    One of the first surprises of the NASA MAVEN mission was the observation by the SWIA instrument of a tenuous population of protons with solar wind energies travelling anti-sunward near periapsis, at altitudes of 150-250 km (Halekas et al., 2015). While the penetration of solar wind protons to low altitude is not completely unexpected given previous Mars Express results, this population maintains exactly the same velocity as the solar wind observed. From previous studies it was known that some fraction of the solar wind can interact with the extended corona of Mars. By charge exchange with the neutral particles in this corona, some fraction of the incoming solar wind protons can gain an electron and become an energetic neutral hydrogen atom. Once neutral, these particles penetrate through the Martian induced magnetosphere with ease, with free access to the collisional atmosphere/ionosphere. The origin, kinetics and transport of the suprathermal O atoms in the transition region (from thermosphere to exosphere) of the Martian upper atmosphere due to the precipitation of the high-energy protons and hydrogen atoms are discussed. Kinetic energy distribution functions of suprathermal and superthermal (ENA) oxygen atoms formed in the Martian upper atmosphere were calculated using the kinetic Monte Carlo model (Shematovich et al., 2011, Shematovich, 2013) of the high-energy proton and hydrogen atom precipitation into the atmosphere. These functions allowed us: (a) to estimate the non-thermal escape rates of neutral oxygen from the Martian upper atmosphere, and (b) to compare with available MAVEN measurements of oxygen corona. Induced by precipitation the escape of hot oxygen atoms may become dominant under conditions of extreme solar events - solar flares and coronal mass ejections, - as it was shown by recent observations of the NASA MAVEN spacecraft (Jakosky et al., 2015). This work is supported by the RFBR project and by the Basic Research Program of the Praesidium of

  13. Volcanic activity on Io and its influence on the dynamics of the Jovian magnetosphere observed by EXCEED/Hisaki in 2015

    Science.gov (United States)

    Yoshikawa, Ichiro; Suzuki, Fumiharu; Hikida, Reina; Yoshioka, Kazuo; Murakami, Go; Tsuchiya, Fuminori; Tao, Chihiro; Yamazaki, Atsushi; Kimura, Tomoki; Kita, Hajime; Nozawa, Hiromasa; Fujimoto, Masaki

    2017-08-01

    Jupiter's moon Io, which orbits deep inside the magnetosphere, is the most geologically active object in the solar system. Kurdalagon Patera, a volcano on Io, erupted in 2015 and became a substantial source of Jovian magnetospheric plasma. Based on Earth-orbiting spacecraft observations, Io plasma torus (IPT) exhibited the peak intensity (nearly double) of ionic sulfur emissions roughly 2 month later, followed by a decay phase. This environmental change provides a unique opportunity to determine how the more heavily loaded magnetosphere behaves. Indeed, the extreme ultraviolet spectroscope for exospheric dynamics onboard the Earth-orbiting spacecraft Hisaki witnessed the whole interval via aurora and IPT observations. A simple-minded idea would be that the centrifugal force acting on fast co-rotating magnetic flux tubes loaded with heavier contents intensifies their outward transport. At the same time, there must be increased inward convection to conserve the magnetic flux. The latter could be accompanied by (1) increased inward velocity of field lines, (2) increased frequency of inward transport events, (3) increased inward flux carried per event, or (4) combinations of them. The Hisaki observations showed that the densities of major ions in the IPT increased and roughly doubled compared with pre-eruption values. The hot electron fraction, which sustains the EUV radiation from the IPT, gradually increased on a timescale of days. Pairs of intensified aurora and IPT brightening due to the enhanced supply of hot electrons from the mid-magnetosphere to the IPT upon aurora explosions observed during both quiet and active times, enabled the study of the mid-magnetosphere/IPT relationship. Hisaki observations under active Io conditions showed that: (1) the hot electron fraction in the torus gradually increased; (2) brightening pairs were more intense; (3) the energy supplied by the largest event maintained enhanced torus emission for less than a day; (4) the time delay

  14. Mars Dayside Thermospheric Composition and Temperatures from the NGIMS MAVEN Instrument: Implications for Thermal Balances

    Science.gov (United States)

    Bougher, Stephen W.; Sharrar, Ryan; Bell, Jared M.; Mahaffy, Paul R.; Benna, Mehdi; Elrod, Meredith K.; Evans, J. Scott

    2017-10-01

    The Mars upper atmosphere, encompassing the thermosphere, ionosphere, and the lower exosphere (~100 to 500 km), constitutes the reservoir that regulates present day and historical escape processes from the planet. The characterization of this reservoir is therefore one of the major science objectives of the MAVEN mission. Current dayside thermospheric composition and temperatures are the focus of this study. The primary MAVEN instrument for in situ sampling of neutral thermospheric structure is the Neutral Gas and Ion Mass Spectrometer (NGIMS, Mahaffy et al. 2015) instrument. It measures the neutral composition of at least 11 key gas species and their major isotopes, with a vertical resolution of ~5 km for targeted species. Thermospheric temperatures are derived from neutral density vertical structure (Bougher et al., 2017). Four NGIMS dayside sampling periods are chosen, spanning mid-April 2015 to late-November 2016, for which the solar zenith angle is less than 60°. The Martian season advances from Ls ~ 335 to 256, while solar EUV fluxes are declining from solar moderate to minimum conditions. Each sampling period is composed of ~150 to 200 orbits (NGIMS Level 2 V07_R02 files). We focus our study on 5 dayside species: CO2, O, N2, CO, and He. Inbound density profiles (and derived temperatures) are extracted and averaged over various orbital intervals, in order to compute longitude averaged profiles, and to minimize the impact of small scale wave structure. Corresponding Mars Global Ionosphere Thermosphere Model (M-GITM, Bougher et al., 2015) predictions for the same seasonal/solar cycle conditions are compared to NGIMS density measurements along the inbound orbit tracks below ~225 km. This M-GITM model is primarily driven by solar EUV-UV forcing at these altitudes; its simulations are used to provide a first comparison with the climatic trends (and variability) gleaned from these NGIMS datasets. M-GITM underlying dayside thermal balances required to reproduce

  15. NASA's Solar System Exploration Research Virtual Institute: Science and Technology for Lunar Exploration

    Science.gov (United States)

    Schmidt, Greg; Bailey, Brad; Gibbs, Kristina

    2015-01-01

    The NASA Solar System Exploration Research Virtual Institute (SSERVI) is a virtual institute focused on research at the intersection of science and exploration, training the next generation of lunar scientists, and development and support of the international community. As part of its mission, SSERVI acts as a hub for opportunities that engage the larger scientific and exploration communities in order to form new interdisciplinary, research-focused collaborations. The nine domestic SSERVI teams that comprise the U.S. complement of the Institute engage with the international science and exploration communities through workshops, conferences, online seminars and classes, student exchange programs and internships. SSERVI represents a close collaboration between science, technology and exploration enabling a deeper, integrated understanding of the Moon and other airless bodies as human exploration moves beyond low Earth orbit. SSERVI centers on the scientific aspects of exploration as they pertain to the Moon, Near Earth Asteroids (NEAs) and the moons of Mars, with additional aspects of related technology development, including a major focus on human exploration-enabling efforts such as resolving Strategic Knowledge Gaps (SKGs). The Institute focuses on interdisciplinary, exploration-related science focused on airless bodies targeted as potential human destinations. Areas of study represent the broad spectrum of lunar, NEA, and Martian moon sciences encompassing investigations of the surface, interior, exosphere, and near-space environments as well as science uniquely enabled from these bodies. This research profile integrates investigations of plasma physics, geology/geochemistry, technology integration, solar system origins/evolution, regolith geotechnical properties, analogues, volatiles, ISRU and exploration potential of the target bodies. New opportunities for both domestic and international partnerships are continually generated through these research and

  16. THE JOINT ESA-NASA EUROPA JUPITER SYSTEM MISSION (EJSM)

    Science.gov (United States)

    Lebreton, J.; Pappalardo, R. T.; Blanc, M.; Bunce, E. J.; Dougherty, M. K.; Erd, C.; Grasset, O.; Greeley, R.; Johnson, T. V.; Clark, K. B.; Prockter, L. M.; Senske, D. A.

    2009-12-01

    The joint "Europa Jupiter System Mission" (EJSM) is an international mission under study in collaboration between NASA and ESA. Its goal is to study Jupiter and its magnetosphere, the diversity of the Galilean satellites, the physical characteristics, composition and geology of their surfaces. Europa and Ganymede are two primary targets of the mission. The reference mission architecture consists of the NASA-led Jupiter Europa Orbiter (JEO) and the ESA-led Jupiter Ganymede Orbiter (JGO). The two primary goals of the mission are i) to determine whether the Jupiter system harbors habitable worlds and ii) to characterize the processes within the Jupiter system. The science objectives addressing the first goal are to: i) characterize and determine the extent of subsurface oceans and their relations to the deeper interior, ii) characterize the ice shells and any subsurface water, including the heterogeneity of the ice, and the nature of surface-ice-ocean exchange; iii) characterize the deep internal structure, differentiation history, and (for Ganymede) the intrinsic magnetic field; iv) compare the exospheres, plasma environments, and magnetospheric interactions; v) determine global surface composition and chemistry, especially as related to habitability; vi) understand the formation of surface features, including sites of recent or current activity, and identify and characterize candidate sites for future in situ exploration. The science objectives for addressing the second goal are to: i) understand the Jovian satellite system, especially as context for Europa and Ganymede; ii) evaluate the structure and dynamics of the Jovian atmosphere; iii) characterize processes of the Jovian magnetodisk/magnetosphere; iv) determine the interactions occurring in the Jovian system; and v) constrain models for the origin of the Jupiter system. Both spacecraft would carry a complement of 11-12 instruments launch separately in 2020 and use a Venus-Earth-Earth Gravity Assist (VEEGA

  17. Obituary: Joseph Wyan Chamberlain, 1928-2004

    Science.gov (United States)

    Hunten, Donald M.

    2004-12-01

    are glad that his last nineteen active years were spent in that role. In the 1960's the AAS had no Division for Planetary Sciences (DPS), and the group organized an annual series of five Arizona Conferences on Planetary Atmospheres. By 1967 several members of the community felt that a DPS was needed; the AAS Council asked Joe to serve as chair of the organizing committee, and when the Division was formed he became the first Chairman. In 1971, he became Director of the NASA Lunar Science Institute and a few years later Professor of Space Physics and Astronomy at Rice University (Houston). After retirement as Professor Emeritus in 1992, he returned to Tucson where he continued an active interest in golf, opera, chess and satirical humor. Joe's program at Yerkes began with observations of aurora and airglow, making use of the wonderful spectrographs designed and built by Meinel. Among his many contributions was the identification and analysis of a band system in the airglow that now bears his name. His interests shifted toward the theoretical; for example, he applied the radiative-transfer theory of his colleague Chandrasekhar to the sodium twilight airglow. In 1961 he published Theory of the Aurora and Airglow, a book so influential that it was reprinted a few years ago by the American Geophysical Union. In the same period his interest in interplanetary hydrogen led to a low-velocity model that was at odds with Eugene N. Parker's model of the solar wind, and a debate ensued until observations showed Parker to be essentially correct. But the Chamberlain ideas were applied to the structure of the Earth's hydrogen exosphere, and for 40 years this work has been accepted as definitive. Later he studied the reduction of the hydrogen escape rate by the "cooling" that results from the loss of the energy carried by the escaping atoms. Joe was selected to deliver the 1961 Helen Warner lecture and chose the topic "The upper atmospheres of the planets." This paper clearly expounds

  18. Mercury's Crater-Hosted Hollows: Chalcogenide Pryo-Thermokarst, and Permafrost Analogs on Earth, Mars, and Titan

    Science.gov (United States)

    Kargel, Jeffrey

    2013-04-01

    -vapor and liquid-vapor fractionation and recondensation). Key phase transitions can occur in the temperature range of Mercury's surface and upper crust. Vapor-solid, vapor-liquid, and solid-liquid transitions of the heated materials resulted in migration and loss of volatiles and anatectic liquids, causing collapse pits to form. Seasonal heating near perihelion may work together with geothermal flux or early impact heating to drive off volatiles and produce the pits. In some cases, local recondensation of moderately volatile materials may have occurred on the rims of the pits; some volatiles may have been transported to the polar regions or lost by exospheric escape. Impacts by comets may have caused local oxidation and formation of oxygenated salts and other minerals, whose local recondensation from fumarole gases can explain the light-toned layers and light-toned rims of many pits. Plating of native volatile metals and semi-metals may also account for some light-toned deposits. Large contrasts in thermal conductivity as well as local topographic shading and latitude controls may result in large differences in element mobility and mineral assemblages. Pyrothermokarst on Mercury may be more chemically heterogeneous and complex in its development than any other thermokarst in the Solar System. Validation of this model would require a future mission with high-resolution multispectral imaging and neutral/ion detection.

  19. Solar Cycle #24 and the Solar Dynamo

    Science.gov (United States)

    Schatten, Kenneth; Pesnell, W. Dean

    2007-01-01

    We focus on two solar aspects related to flight dynamics. These are the solar dynamo and long-term solar activity predictions. The nature of the solar dynamo is central to solar activity predictions, and these predictions are important for orbital planning of satellites in low earth orbit (LEO). The reason is that the solar ultraviolet (UV) and extreme ultraviolet (EUV) spectral irradiances inflate the upper atmospheric layers of the Earth, forming the thermosphere and exosphere through which these satellites orbit. Concerning the dynamo, we discuss some recent novel approaches towards its understanding. For solar predictions we concentrate on a solar precursor method, in which the Sun's polar field plays a major role in forecasting the next cycle s activity based upon the Babcock-Leighton dynamo. With a current low value for the Sun s polar field, this method predicts that solar cycle #24 will be one of the lowest in recent times, with smoothed F10.7 radio flux values peaking near 130 plus or minus 30 (2 sigma), in the 2013 timeframe. One may have to consider solar activity as far back as the early 20th century to find a cycle of comparable magnitude. Concomitant effects of low solar activity upon satellites in LEO will need to be considered, such as enhancements in orbital debris. Support for our prediction of a low solar cycle #24 is borne out by the lack of new cycle sunspots at least through the first half of 2007. Usually at the present epoch in the solar cycle (approx. 7+ years after the last solar maximum), for a normal size following cycle, new cycle sunspots would be seen. The lack of their appearance at this time is only consistent with a low cycle #24. Polar field observations of a weak magnitude are consistent with unusual structures seen in the Sun s corona. Polar coronal holes are the hallmarks of the Sun's open field structures. At present, it appears that the polar coronal holes are relatively weak, and there have been many equatorial coronal holes

  20. Experimental investigation of the radiation shielding of a MCP detector in the radiation environment near Europa

    Science.gov (United States)

    Tulej, Marek; Wurz, Peter; Meyer, Stefan; Lasi, Davide; Lüthi, Matthias; Galli, André; Piazza, Daniele; Desorgher, Laurent; Hajdas, Wojciech; Reggiani, Davide; Karlsson, Stefan; Kalla, Leif

    2016-04-01

    The Neutral Ion Mass spectrometer (NIM) is one of the six instruments in the Particle Environmental Package (PEP) designed for the JUICE mission of ESA to the Jupiter system. NIM will conduct detailed measurements of chemical composition of Jovian moon exospheres and is equipped with a sensitive MCP ion detector. To maintain high sensitivity of the NIM instrument, background signals arising from the presence of a large background of penetrating radiation (mostly high-energy electrons and protons) in Jupiter's magnetosphere have to be minimised. We investigate the performance of a layered-Z radiation shield, an Al-Ta-Al sandwich, as a potential shielding against high-energy electrons. The experimental investigations were performed at the PiM1 beam line of the High Intensity Proton Accelerator Facilities located at the Paul Scherrer Institute (PSI), Villigen, Switzerland. The facility delivers a particle beam containing e,  and  with an adjustable momentum ranging from 17.5 to 345 MeV/c. The measurements of the induced radiation background generated during the interaction of primary particles with Al-Ta-Al sandwich were conducted by beam diagnostic methods and a MCP detector. Diagnostic methods provided for the characterisation of the beam parameters (beam geometry, flux and intensity) and identification of individual particles in the primary beam and in the flux of secondary particles. The MCP detector measurements provided information on the effects of radiation and the results of these measurements define the performance of the shielding material in reducing the background arising from penetrating radiation. In parallel, we performed modelling studies using GEANT 4 and GRASS methods to identify products of the interaction and predict their fluxes and particle rates at the MCP detector. Combination of the experiment and modelling studies yields detailed characterisation of the radiation effects produced by the interaction of the incident e- in the

  1. Environmental effects of human exploration of the Moon

    Science.gov (United States)

    Mendell, Wendell

    Aerospace engineers use the term Environment to designate a set of externally imposed bound-ary conditions under which a device must operate. Although the parameters may be time-varying, the engineer thinks of the operating environment as being fixed. Any effect the device might have on the environment generally is neglected. In the case where the device is intended to measure the environment, its effect on the measured quantities must be considered. For example, a magnetometer aboard a spacecraft must be extended on a boom to minimize the disturbing influence of the spacecraft on the magnetic field, particularly if the field is weak. In contrast, Environment has taken on political and even ethical connotations in modern Western society, referring to human-induced alterations to those aspects of the terrestrial environment that are required for a healthy and productive life. The so-called Green Movement takes preservation of the environment as its mantra. Scientists are at the center of the debate on environmental issues. However, the concern of scientists over irreversible consequences of hu-man activity extend beyond ecology to preservation of cultural artifacts and to effects that alter the ability to conduct investigations such as light pollution in astronomy. The policy of Planetary Protection applied to science and exploration missions to other bodies in the solar system arises from the concern for deleterious effects in terrestrial ecology from hypothetical extraterrestrial life forms as well as overprints of extraterrestrial environments by terrestrial biology. Some in the scientific community are advocating extension of the planetary protection concept beyond exobiology to include fragile planetary environments by might be permanently altered by human activity e.g., the lunar exosphere. Beyond the scientific community, some environmentalists argue against any changes to the Moon at all, including formation of new craters or the alteration of the natural

  2. The science of the lunar poles

    Science.gov (United States)

    Lucey, P. G.

    2011-12-01

    It was the great geochemist Harold Urey who first called attention to peculiar conditions at the poles of the Moon where the very small inclination of the lunar spin axis with respect to the sun causes craters and other depressions to be permanently shaded from sunlight allowing very low temperatures. Urey suggested that the expected low temperature surfaces could cold trap and collect any vapors that might transiently pass through the lunar environment. Urey's notion has led to studies of the poles as a new research area in lunar science. The conditions and science of the poles are utterly unlike those of the familiar Moon of Neil Armstrong, and the study of the poles is similar to our understanding of the Moon itself at the dawn of the space age, with possibilities outweighing current understanding. Broadly, we can treat the poles as a dynamic system of input, transport, trapping, and loss. Volatile sources range from continuous, including solar wind, the Earth's polar fountain and micrometeorites, to episodic, including comets and wet asteroids, to nearly unique events including late lunar outgassing and passage through giant molecular clouds. The lunar exosphere transports volatiles to the poles, complicated by major perturbances to the atmosphere by volatile-rich sources. Trapping includes cold trapping, but also in situ creation of more refractory species such as organics, clathrates and water-bearing minerals, as well as sequester by regolith overturn or burial by larger impacts. Finally, volatiles are lost to space by ionization and sweeping. Spacecraft results have greatly added to the understanding of the polar system. Temperatures have been precisely measured by LRO, and thermal models now allow determination of temperature over the long evolution of the lunar orbit, and show very significant changes in temperature and temperature distribution with time and depth. Polar topography is revealed in detail by Selene and LRO laser altimeters while direct

  3. Some geophysical and geochemical consequences of slab serpentinization at subduction zones

    Science.gov (United States)

    Phipps Morgan, J.; Ruepke, L. H.; Ranero, C.; Hort, M.

    2002-12-01

    Here we explore the potential impact of slab serpentinization and deserpentinization processes on arc-melting and on water, carbon-dioxide, U, Pb, and noble gas recycling into the deep mantle. We examine the consequences of a scenario in which bend-faulting between the outer rise and trench axis creates the conduits for seawater to reach and react with cold lithospheric mantle to serpentinize it. Water penetration to serpentinize the slab-lithosphere will be inhibited by thick sediments (e.g. Cascades) or thick oceanic crust (subducting oceanic plateaus), while subducting long-offset fracture zones will be especially serpentine-rich because they serpentinized at both the spreading center and subduction zone. If this process occurs, then the incoming lithosphere will typically contain ~500m of altered sediments, ~6 km of partially hydrated oceanic crust, and ~20-55km of partially serpentinized slab mantle. Possible regional geophysical consequences of this scenario are: (1) Fracture Zones preferentially become tears in subducting slabs because they are relatively serpentine rich, thus they deserpentinize more. (2) If so, then their greater deserpentinization should produce greater sub-arc water release which leads to greater arc melting above subducted fracture zones. (3) Regions of little serpentinization will be correlated with flat subduction, lower volumes of slab-water release, and relatively low rates of arc-volcanism. Our thermomechanical modelling implies, depending upon a slab's age and subduction rate, between 30-90% of the slab's chemically bound water is likely to survive sub-arc dehydration to transport its water into the deeper mantle. Possible global geochemical consequences of this scenario are: (1) At current subduction rates, 0.5-1.5 oceans of water would be recycled past the arc-melting region into the deeper mantle during the past Ga. (2) Since 0.3%, 1%, and 3% of the exosphere's Ne, Ar, and Xe are dissolved in the oceans, this implies that at

  4. Mercury's Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroidal Space Weathering Studies

    Science.gov (United States)

    Domingue, Deborah L.; Chapman, Clark. R.; Killen, Rosemary M.; Zurbuchen, Thomas H.; Gilbert, Jason A.; Sarantos, Menelaos; Benna, Mehdi; Slavin, James A.; Schriver, David; Travnicek, Pavel M.; hide

    2014-01-01

    Mercury's regolith, derived from the crustal bedrock, has been altered by a set of space weathering processes. Before we can interpret crustal composition, it is necessary to understand the nature of these surface alterations. The processes that space weather the surface are the same as those that form Mercury's exosphere (micrometeoroid flux and solar wind interactions) and are moderated by the local space environment and the presence of a global magnetic field. To comprehend how space weathering acts on Mercury's regolith, an understanding is needed of how contributing processes act as an interactive system. As no direct information (e.g., from returned samples) is available about how the system of space weathering affects Mercury's regolith, we use as a basis for comparison the current understanding of these same processes on lunar and asteroidal regoliths as well as laboratory simulations. These comparisons suggest that Mercury's regolith is overturned more frequently (though the characteristic surface time for a grain is unknown even relative to the lunar case), more than an order of magnitude more melt and vapor per unit time and unit area is produced by impact processes than on the Moon (creating a higher glass content via grain coatings and agglutinates), the degree of surface irradiation is comparable to or greater than that on the Moon, and photon irradiation is up to an order of magnitude greater (creating amorphous grain rims, chemically reducing the upper layers of grains to produce nanometer scale particles of metallic iron, and depleting surface grains in volatile elements and alkali metals). The processes that chemically reduce the surface and produce nanometer-scale particles on Mercury are suggested to be more effective than similar processes on the Moon. Estimated abundances of nanometer-scale particles can account for Mercury's dark surface relative to that of the Moon without requiring macroscopic grains of opaque minerals. The presence of

  5. Students Engaging the Public in Exciting Discoveries by NASA's MESSENGER Mission

    Science.gov (United States)

    Hallau, K. G.; Morison, J.; Schuele, H.

    2012-12-01

    address topics such as craters with pyroclastic deposits, rayed craters, crater superposition, dark materials on Mercury, smooth plains, and lobate scarps. As MESSENGER continues its orbital study of Mercury, ever more exciting and surprising data are being returned, and from them new MPCs are being produced. Several of these MPCs focus on specific geologic features of Mercury, including the Caloris basin, one of the largest impact basins in the solar system; Pantheon Fossae, a mysterious set of radial troughs; and Raditladi, a comparatively young, double-ringed impact basin. Moreover, discoveries about Mercury extend beyond geologic features. Newly produced MPCs also explain how MESSENGER used gravity assists of Earth, Venus, and Mercury to succeed in its orbit insertion and how the probe's eccentric orbit protects the spacecraft and instruments from heat re-radiated from Mercury's surface. New information regarding Mercury's magnetic field, magnetosphere, and exosphere are also intriguing topics to be presented in future MPCs.

  6. LCROSS Impact Simulations and Predictions

    Science.gov (United States)

    Asphaug, E.; Korycansky, D.; Jutzi, M.; Plesko, C.; Colaprete, A.

    2008-12-01

    The primary objective of the Lunar Crater Observation and Sensing Satellite (LCROSS) is to confirm the presence or absence of water ice that might have trapped out over time from the lunar exosphere into permanently shadowed inter-crater regolith near the lunar poles. It will provide a critical ground-truth for Lunar Prospector and LRO neutron and radar maps, making it possible to assess the total lunar water inventory and to provide significant insight into the processes that delivered hydrogen to the polar regions. Non-detection of water could lead to significant changes in the architecture of lunar operations and settlement. Ong and Asphaug (LPSC 2008) study the fraction of volatile material that remains bound to the Moon and Mars during comet and asteroid impacts and calculate a mass of water retained over the past 2 Ga of order 1E10-1E11 tons, a few times the water ice inferred by Feldman et al. (Science 1998) on the basis of Lunar Prospector neutron detection. This flux includes small contemporary events but is dominated by major discrete contributions in the past. Whatever the mechanism for the delivery and possible retention of lunar water, interest in the possible presence of water ice has both scientific and operational foundations. If water is present in the upper meters to the few percent level, LCROSS will find it by using a 2000 kg kinetic impactor -- the empty Atlas V Centaur upper stage -- to excavate more than 250 metric tons of regolith. The thermal and spectral signature of the impact flash and the crater ejecta that gets launched into sunlight will be studied in detail, and the results transmitted to Earth before the 700 kg shepherding spacecraft also impacts the Moon. These two impact experiments and their aftermaths will also be observed from a number of Lunar-orbital and Earth-based assets. For the purpose of mission planning, asset security, and scientific prediction, we have conducted a variety of calculations based upon several models

  7. Assessing The Anthropocene In The Context Of Comparative Planetology.

    Science.gov (United States)

    Grinspoon, D. H.

    2012-12-01

    How does the Anthropocene Era differ, in essence, from past planetary catastrophes? I suggest that the major environmental transformations of inhabited planets can be classed into four types of changes, each characterized by the roles of life and intelligence. 1. "Natural disasters" in which life plays no role. Examples include climate disruptions from large impact events or periods of heavy bombardment, changes in galactic environment, climate disruptions from formation of large igneous provinces, changes in the Sun, runaway greenhouses, and atmospheric loss due to impact erosion or exospheric escape. 2. "Biologically induced" changes in which life itself causes major global transformations. Examples include the "Oxygen catastrophe" and possibly the global "snowball Earth" glaciations. If there was an origin of life on Mars, then exploration of ancient terrains might uncover similar global environmental consequences of life. 3. "Inadvertent": What we might call the Proto-Anthropocene Era, in which global technological civilization causes accidental changes. Examples include ozone depletion, global warming from fossil fuel consumption, deforestation and desertification. 4. "Intentional": The Anthropocene Era, in which purposeful global changes are caused by intelligent life, acting with forethought, aware of its global role and consequences. Examples include ozone replenishment (already underway), intentional reversal or modulation of industrial global warming (currently under discussion), geoengineering to preventing future ice ages, terraforming of Mars or other planets (currently being modeled) and mitigation of eventual runaway greenhouse due to future solar evolution. Whether the Anthropocene will actually be a sustained geological era or more of an event, such as the K/T boundary, remains to be seen. The natural capriciousness of planetary systems means that long-term survival will require that we learn to enact what here I am here calling "planetary changes

  8. JUICE: a European mission to Jupiter and its icy moons

    Science.gov (United States)

    Titov, D.; Erd, C.; Duvet, L.; Wielders, A.; Torralba-Elipe, I.; Altobelli, N.

    2013-09-01

    JUICE (JUpiter ICy moons Explorer) is the first L-class mission selected for the ESA's Cosmic Vision programme 2015-2025 which has just entered the definition phase. JUICE will perform detailed investigations of Jupiter and its system in all their inter-relations and complexity with particular emphasis on Ganymede as a planetary body and potential habitat. Investigations of Europa and Callisto will complete a comparative picture of the Galilean moons. By performing detailed investigations of Jupiter's system, JUICE will address in depth two key questions of the ESA's Cosmic Vision programme: (1) What are the conditions for planet formation and the emergence of life? and (2) How does the Solar System work? The overarching theme for JUICE has been formulated as: The emergence of habitable worlds around gas giants. At Ganymede the mission will characterize in detail the ocean layers; provide topographical, geological and compositional mapping of the surface; study the physical properties of the icy crusts; characterize the internal mass distribution, investigate the exosphere; study Ganymede's intrinsic magnetic field and its interactions with the Jovian magnetosphere. For Europa, the focus will be on the non-ice chemistry, understanding the formation of surface features and subsurface sounding of the icy crust over recently active regions. Callisto will be explored as a witness of the early solar system. JUICE will perform a comprehensive multidisciplinary investigation of the Jupiter system as an archetype for gas giants including exoplanets. The circulation, meteorology, chemistry and structure of the Jovian atmosphere will be studied from the cloud tops to the thermosphere. The focus in Jupiter's magnetosphere will include an investigation of the three dimensional properties of the magnetodisc and in-depth study of the coupling processes within the magnetosphere, ionosphere and thermosphere. Aurora and radio emissions and their response to the solar wind will be

  9. Science of the Joint ESA-NASA Europa Jupiter System Mission (EJSM)

    Science.gov (United States)

    Blanc, Michel; Greeley, Ron

    2010-05-01

    The Europa Jupiter System Mission (EJSM), an international joint mission under study by NASA and ESA, has the overarching theme to investigate the emergence of habitable worlds around gas giants. Jupiter's diverse Galilean satellites—three of which are believed to harbor internal oceans—are the key to understanding the habitability of icy worlds. To this end, the reference mission architecture consists of the NASA-led Jupiter Europa Orbiter (JEO) and the ESA-led Jupiter Ganymede Orbiter (JGO). JEO and JGO will execute a coordinated exploration of the Jupiter System before settling into orbit around Europa and Ganymede, respectively. JEO and JGO carry sets of complementary instruments, to monitor dynamic phenomena (such as Io's volcanoes and Jupiter's atmosphere), map the Jovian magnetosphere and its interactions with the Galilean satellites, and characterize water oceans beneath the ice shells of Europa and Ganymede. Encompassed within the overall mission theme are two science goals, (1) Determine whether the Jupiter System harbors habitable worlds and (2) Characterize the processes within the Jupiter System. The science objectives addressed by the first goal are to: i) characterize and determine the extent of subsurface oceans and their relations to the deeper interior, ii) characterize the ice shells and any subsurface water, including the heterogeneity of the ice, and the nature of surface-ice-ocean exchange; iii) characterize the deep internal structure, differentiation history, and (for Ganymede) the intrinsic magnetic field; iv) compare the exospheres, plasma environments, and magnetospheric interactions; v) determine global surface composition and chemistry, especially as related to habitability; vi) understand the formation of surface features, including sites of recent or current activity, and identify and characterize candidate sites for future in situ exploration. The science objectives for addressed by the second goal are to: i) understand the

  10. Geobiology of the Critical Zone: the Hierarchies of Process, Form and Life provide an Integrated Ontology

    Science.gov (United States)

    Cotterill, Fenton P. D.

    2016-04-01

    In the framework of Earth System Science, landscapes are the templates structuring the biosphere: the membranes interfacing between exosphere and geosphere. The hosts of earth surface processes, in their dynamics and complexity, landscapes hold a pivotal position in the evolving earth system - not least in their archives of Earth history. Their landforms document impacts of formative events originating in extra-terrestrial, geological and climatic processes. Nevertheless, major challenges to reconstruct dynamics at this interface between geosphere and exosphere hamper research efforts. Events at the mesoscale over evolutionary timescales are an important reason for why the academic schools of mega- versus process geomorphology persist (see Summerfield MA 2005. Trans. Inst. Brit Geogr NS, 30, 402-415). Austere limits on what their respective methods can reveal in mesoscale phenomena face several problems (besides costs of sampling and analyses). One, surviving landforms often lack the requisite minerals (e.g. of volcanic events). Second, the spatial resolution of orthodox methods (e.g. thermochronology) cannot resolve mesoscale patterns. Third, the surface dating tools with superb spatial precision have finitee temporal limits (Luminescence-Dating and Cosmogenic Isotopes). Fourth, and by no means least, the cumulative impact of earth surface processes has overwritten and/or eroded physical evidence of earlier formative events. (This problem is exemplified in tropical landscapes where deep, pervasive bioturbation is the dominant earth surface process!) The cumulative outcome of these inherent turnovers of landscapes has shaped the inherent emptiness of the Rock Record, which sets absolute limits on its archives (Ager D 1993. The Nature of the Stratigraphical Record; Miall AD 2015. in: Strata and Time: Probing the Gaps in Our Understanding. Geological Society, London, Special Publications, 404, http://dx.doi.org/10.1144/SP404.4). These limitations on mesoscale

  11. Conquering the Mesoscale of Africa's Landscapes: deciphering the Genomic Record of Individuating Landforms with Geoecodynamics

    Science.gov (United States)

    Cotterill, Fenton P. D.

    2016-04-01

    In the framework of Earth System Science, landscapes are the templates structuring the biosphere: the membranes interfacing between exosphere and geosphere. The hosts of earth surface processes, in their dynamics and complexity, landscapes hold a pivotal position in the evolving earth system - not least in their archives of Earth history. Their landforms document impacts of formative events originating in extra-terrestrial, geological and climatic processes. Nevertheless, major challenges to reconstruct dynamics at this interface between geosphere and exosphere hamper research efforts. Events at the mesoscale over evolutionary timescales are an important reason for why the academic schools of mega- versus process geomorphology persist (see Summerfield MA 2005. Trans. Inst. Brit Geogr NS, 30, 402-415). Austere limits on what their respective methods can reveal in mesoscale phenomena face several problems (besides costs of sampling and analyses). One, surviving landforms often lack the requisite minerals (e.g. of volcanic events). Second, the spatial resolution of orthodox methods (e.g. thermochronology) cannot resolve mesoscale patterns. Third, the surface dating tools with superb spatial precision have finitee temporal limits (Luminescence-Dating and Cosmogenic Isotopes). Fourth, and by no means least, the cumulative impact of earth surface processes has overwritten and/or eroded physical evidence of earlier formative events. (This problem is exemplified in tropical landscapes where deep, pervasive bioturbation is the dominant earth surface process!) The cumulative outcome of these inherent turnovers of landscapes has shaped the inherent emptiness of the Rock Record, which sets absolute limits on its archives (Ager D 1993. The Nature of the Stratigraphical Record; Miall AD 2015. in: Strata and Time: Probing the Gaps in Our Understanding. Geological Society, London, Special Publications, 404, http://dx.doi.org/10.1144/SP404.4). These limitations on mesoscale

  12. Space-weathering processes and products on volatile-rich asteroids

    Science.gov (United States)

    Britt, D.; Schelling, P.; Consolmagno, G.; Bradley, T.

    2014-07-01

    Space weathering is a generic term for the effects on atmosphereless solid bodies in the solar system from a range of processes associated with direct exposure to the space environment. These include impact processes (shock, vaporization, fragmentation, heating, melting, and ejecta formation), radiation damage (from galactic and solar cosmic rays), solar-wind effects (irradiation, ion implantation, and sputtering), and the chemical reactions driven by these processes. The classic example of space weathering is the formation of the lunar spectral red slope associated with the production of nanophase Fe (npFe0) in the dusty lunar regolith (C.R. Chapman, 2004, Annual Review of Earth & Planet. Sci. 32, C.M. Pieters, 2000, MAPS 35). Similar npFe0 has been recovered from asteroid (25143) Itokawa and some asteroid classes do exhibit modest spectral red slopes (T. Noguchi, 2011, Science 333). Space weathering can be thought of as driven by a combination of the chemical environment of space (hard vacuum, low oxygen fugacity, solar-wind implantation of hydrogen) along with thermal energy supplied by micrometeorite impacts. The forward modeling of space weathering as thermodynamically-driven decomposition of common rock-forming minerals suggests the production of a range of daughter products: (1) The silicate products typically lose oxygen, other volatile elements (i.e., sulfur and sodium), and metallic cations, producing minerals that are typically more disordered and less optically active than the original parent materials. (2) The decomposed metallic cations form in nano-sized blebs including npFe0, on the surfaces or in condensing rims of mineral grains. This creates a powerful optical component as seen in the lunar red slope. Surfaces with exposed npFe0 are an ideal environment for catalyzing further reactions. (3) The liberated volatile elements and gases (O, S, Na) may form an observable exosphere (e.g., Moon and Mercury) and can either escape from the body or

  13. WASP-12b and Its Possible Fiery Demise

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    Spitzer Space Telescope. These two new sets of observations, combined with the decade of previous observations, allowed the authors to fit models to WASP-12bs orbit over time.The results show that a constant period for WASP-12b is firmly ruled out this planets orbit is definitely changing over time. The observations are best fit by a model in which the planets orbit is tidally decaying, but a 14-year apsidal precession cycle cant be definitively ruled out.Future ProspectsPossible futures for WASP-12bs orbit, based on the decay model (red) and the precession model (blue). We should be able to differentiate between these models with a few more years of observations. [Patra et al. 2017]If the planets orbit is decaying, then the authors show that its period will shrink to zero within 3.2 million years, suggesting that were currently witnessing the last 0.2% of the planets lifetime. Supporting the orbital-decay hypothesis are independent observations that suggest WASP-12b is approaching a point of tidal disruption it appears to have an extended and escaping exosphere, for instance.While we cant yet state for certain that WASP-12bs orbit is decaying, the authors argue that we should be able to tell conclusively with a few more years of observations. Either of the two outcomes above orbital decay or apsidal precession would have exciting scientific implications, however: if WASP-12bs orbit is decaying, we can measure the tidal dissipation rate of the star. If its orbit is apsidally precessing, we may be able to measure the tidal deformability of an exoplanet. Future observations of this hot Jupiter should prove interesting!CitationKishore C. Patra et al 2017 AJ 154 4. doi:10.3847/1538-3881/aa6d75

  14. EMAPS: An Efficient Multiscale Approach to Plasma Systems with Non-MHD Scale Effects

    Energy Technology Data Exchange (ETDEWEB)

    Omelchenko, Yuri A. [Trinum Research, Inc., San Diego, CA (United States)

    2016-08-08

    Global interactions of energetic ions with magnetoplasmas and neutral gases lie at the core of many space and laboratory plasma phenomena ranging from solar wind entry into and transport within planetary magnetospheres and exospheres to fast-ion driven instabilities in fusion devices to astrophysics-in-lab experiments. The ability of computational models to properly account for physical effects that underlie such interactions, namely ion kinetic, ion cyclotron, Hall, collisional and ionization processes is important for the success and planning of experimental research in plasma physics. Understanding the physics of energetic ions, in particular their nonlinear resonance interactions with Alfvén waves, is central to improving the heating performance of magnetically confined plasmas for future energy generation. Fluid models are not adequate for high-beta plasmas as they cannot fully capture ion kinetic and cyclotron physics (e.g., ion behavior in the presence of magnetic nulls, shock structures, plasma interpenetration, etc.). Recent results from global reconnection simulations show that even in a MHD-like regime there may be significant differences between kinetic and MHD simulations. Therefore, kinetic modeling becomes essential for meeting modern day challenges in plasma physics. The hybrid approximation is an intermediate approximation between the fluid and fully kinetic approximations. It eliminates light waves, removes the electron inertial temporal and spatial scales from the problem and enables full-orbit ion kinetics. As a result, hybrid codes have become effective tools for exploring ion-scale driven phenomena associated with ion beams, shocks, reconnection and turbulence that control the large-scale behavior of laboratory and space magnetoplasmas. A number of numerical issues, however, make three-dimensional (3D) large-scale hybrid simulations of inhomogeneous magnetized plasmas prohibitively expensive or even impossible. To resolve these difficulties

  15. An Investigation into Establishing a Formation of Small Satellites in a Lunar Flower Constellation

    Science.gov (United States)

    McManus, Lauren

    Lunar science missions such as LADEE and GRAIL achieved unprecedented measurements of the Lunar exosphere and gravity field. These missions were performed with one (LADEE) or two (GRAIL) traditional satellites. The global coverage achieved by these missions could have been greatly enhanced with the use of a constellation of satellites. A constellation of communication satellites at the Moon would also be necessary if a Lunar human base were to be established. Constellations with many satellites are expensive with traditional technology, but have become feasible through the technological advancements and affordability of cubesats. Cubesat constellations allow for full surface coverage in science or communication missions at a reasonable mission cost. Repeat ground track orbits offer interesting options for science or communication constellations, since they provide repeat coverage of the surface at a fixed time between sequential visits. Flower constellations are a family of constellations being studied primarily by Daniele Mortari at Texas A&M; University that make use of repeat ground tracks. Orbital parameters are selected such that the nodal period of the orbit matches the nodal period of the primary body by a factor dependent on the number of days and the number of revolutions to repeat the ground track. All orbits in a flower constellation have identical orbital elements, with the exception of the right ascension of the ascending node (RAAN) and the initial mean anomaly, which are determined based on the desired phasing scheme desired. Flower constellations have thus far primarily been studied at Earth. A flower constellation at the Moon could be quite useful for science or communication purposes. In this scenario, the flower constellation satellites would be small satellites, which introduces many unique challenges. The cubesats would have limited propulsion capability and would need to be deployed from a mothercraft. Orbital maintenance would then be

  16. Chandrayaan-2: India's First Soft-landing Mission to Moon

    Science.gov (United States)

    Mylswamy, Annadurai; Krishnan, A.; Alex, T. K.; Rama Murali, G. K.

    2012-07-01

    The first Indian planetary mission to moon, Chandrayaan-1, launched on 22nd October, 2008 with a suite of Indian and International payloads on board, collected very significant data over its mission duration of close to one year. Important new findings from this mission include, discovery of hydroxyl and water molecule in sunlit lunar surface region around the poles, exposure of large anorthositic blocks confirming the global lunar magma hypothesis, signature of sub surface ice layers in permanently shadowed regions near the lunar north pole, evidence for a new refractory rock type, mapping of reflected lunar neutral atoms and identification of mini-magnetosphere, possible signature of water molecule in lunar exosphere, preserved lava tube that may provide site for future human habitation and radiation dose en-route and around the moon. Chandrayaan-2:, The success of Chandrayaan-1 orbiter mission provided impetus to implement the second approved Indian mission to moon, Chandrayaan-2, with an Orbiter-Lander-Rover configuration. The enhanced capabilities will enable addressing some of the questions raised by the results obtained from the Chandrayaan-1 and other recent lunar missions and also to enhance our understanding of origin and evolution of the moon. The orbiter that will carry payloads to further probe the morphological, mineralogical and chemical properties of the lunar surface material through remote sensing observations in X-ray, visible, infra-red and microwave regions. The Lander-Rover system will enable in-depth studies of a specific lunar location and probe various physical properties of the moon. The Chandrayaan-2 mission will be collaboration between Indian Space Research Organization (ISRO) and the Federal Space Agency of Russia. ISRO will be responsible for the Launch Vehicle, the Orbiter and the Rover while the Lander will be provided by Russia. Initial work to realize the different elements of the mission is currently in progress in both countries

  17. The MESSENGER mission to Mercury: new insights into geological processes and evolution

    Science.gov (United States)

    Head, James W., III; Solomon, Sean C.; McNutt, Ralph L., Jr.; Blewett, David T.; Chapman, Clark R.; Domingue, Deborah L.; Evans, Larry G.; Gillis-Davis, Jeffrey J.; Hawkins, S. Edward, III; Helbert, Jörn; Holsclaw, Gregory M.; Izenberg, Noam R.; McClintock, William E.; McCoy, Timothy J.; Merline, William J.; Murchie, Scott L.; Nittler, Larrz R.; Phillips, Roger J.; Prockter, Louise M.; Robinson, Mark S.; Sprague, Ann L.; Strom, Robert G.; Vilas, Faith; Watters, Thomas R.; Zuber, Maria T.

    2008-09-01

    data from the first MESSENGER flyby of Mercury, and that from subsequent encounters and orbital operations, will enable us to relate global contraction to the history of volcanism and impact crater and basin formation. Through the synergism provided by the instruments on the MESSENGER spacecraft [1], we will be able to infer the nature and history of materials on the surface, and how the geological history fits into the larger context of Mercury's dynamic system: a liquid iron-rich outer core, coupled through a dominantly dipolar magnetic field to the surface, exosphere, and magnetosphere, all of which interact with the solar wind. References: [1] S. C. Solomon et al. (2007) Space Sci. Rev., 131, 3- 39. [2] S. C. Solomon et al. (2007) EPSC 2008, this meeting. [3] S. C. Solomon et al. (2008) Science, in press. [4] B. J. Anderson et al. (2008) Science, in press. [5] J. A. Slavin et al. (2008) Science, in press. [6] T. H. Zurbuchen et al. (2008) Science, in press. [7] W. E. McClintock et al. (2008a) Science, in press. [8] M. S. Robinson et al. (2008) Science, in press. [9] W. E. McClintock et al. (2008b) Science, in press. [10] S. L. Murchie et al. (2008) Science, in press. [11] M. T. Zuber et al. (2008) Science, in press. [12] R. G. Strom et al. (2008) Science, in press. [13] J. W. Head et al. (2008) Science, in press. [14] S. E. Hawkins, III, et al. (2007) Space Sci. Rev., 131, 247-338. [15] W. E. McClintock and M. R. Lankton (2007) Space Sci. Rev., 131, 481-522. [16] J. F. Cavanaugh et al. (2007) Space Sci. Rev., 131, 451-480. [17] J. W. Head et al. (2007) Space Sci. Rev., 131, 41-84. [18] W. V. Boynton et al. (2007) Space Sci. Rev., 131, 85-104. [19] M. T. Zuber et al. (2007) Space Sci. Rev., 131, 105-132. [20] M. S. Robinson and P. G. Lucey (1997) Science, 275, 197-200.