WorldWideScience
 
 
1

Life after Venus Express: Science goals for a European Venus radar orbiter  

Science.gov (United States)

ESA’s Venus Express mission has led to a renaissance of Venus science, following a dearth of Venus missions in the previous 15 years. Venus Express has made many discoveries in atmospheric science, for which its payload was optimised; however it has also provided tantalising hints about the geological activity of the planet. Mesospheric sulphur dioxide abundances vary by 1000% on decadal timescales, in a pattern which suggests episodic volcanic injections [Marcq et al. Nature Geosci 2013; Esposito, Science 1984]; anomalous emissivity near suggest volcanic hotspots implies geologically recent, as-yet-unweathered lava flows [Smrekar et al., Science 2010]; and recent results, if confirmed, show temporal evolution of thermal emission from some regions of the surface may be direct evidence of volcanic activity during the duration of the VEx mission [Shalygin et al., LPSC 2014]. While there are more results to be obtained yet from the Venus Express dataset, further investigation of these phenomena will require a new Venus mission. We therefore propose an orbiter mission focussed on characterising the geological activity of Venus. The key instrument would be a Synthetic Aperture Radar (SAR). Why a radar mission following NASA’s Magellan mission? Radar capabilities are vastly improved in the last 30 years and a modern radar would be capable of spatial resolution approaching two orders of magnitude better than that from Magellan; this enables a wide range of investigations, from detailed study of tectonic, volcanic and Aeolian features, to stratigraphy for better reconstruction of geological epochs. Interferometric SAR could also be used to study the centimetre-scale surface deformations due to current volcanic or tectonic activity. Constraints on interior structure can be obtained not only from improved gravity mapping (from spacecraft tracking) but also by studying the spin state of Venus from high-resolution radar measurements. The radar measurements will be complemented by a further suite of instruments which may include a dedicated surface emission mapper using near-infrared spectral windows; a spectrometer suite to map sulphur dioxide and other possibly volcanic gases; and possibly a subsurface sounding radar to reveal the structure of lava flows and other surface structures. This mission, following on from the 2007 EVE [Chassefière et al., Exp. Astron 2009] and 2010 Envision [Ghail et al., Exp. Astron 2012] proposals, is being developed for proposal to ESA as a “Medium-class” mission in late 2014.

Wilson, Colin; Ghail, Richard

2

Venus express: Highlights of the nominal mission  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Venus Express is the first European (ESA) mission to the planet Venus. Its main science goal is to carry out a global survey of the atmosphere, the plasma environment, and the surface of Venus from orbit. The payload consists of seven experiments. It includes a powerful suite of remote sensing imagers and spectrometers, instruments for in-situ investigation of the circumplanetary plasma and magnetic field, and a radio science experiment. The spacecraft, based on the Mars Express bus modified ...

Titov, Dv; Svedhem, H.; Taylor, Fw; Barabash, S.; Bertaux, J-l; Drossart, P.; Formisano, V.; Haeusler, B.; Korablev, O.; Markiewicz, Wj; Nevejans, D.; Paetzold, M.; Piccioni, G.; Sauvaud, J-a; Zhang, Tl

2009-01-01

3

Venus atmosphere from Venus Express  

Science.gov (United States)

Since April 2006 Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. A consistent picture of the climate on Venus is emerging on the basis of the new data on the global temperature structure, the com-position and its variations, the cloud morphology at various levels, the atmospheric dynamics and general circulation, and near-infrared emissions from trace species such as oxygen in the mesosphere. Vertical profiles of atmospheric temperature in the mesosphere and upper tropo-sphere show strong variability correlated with changes in the cloud top structure and many fine details indicating dynamical processes. Temperature sounding also shows that the main cloud deck at 50-60 km is convectively unstable over large portion of the planet, in agreement with the analysis of UV images. Imaging also reveals strong latitudinal variations and significant temporal changes in the global cloud top morphology, which will inevitably modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from 72 km in the low and middle latitudes to 64 km in the polar region, marking vast polar depressions that form as a re-sult of the Hadley-type meridional circulation. Stellar and solar occultation measurements have revealed an extended upper haze of submicron particles and provided information on its optical properties. Solar occultation observations and deep atmosphere spectroscopy have quantified the distribution of the major trace gases H2O, SO2, CO, COS above and below the clouds, and so provided important input and validation for models of chemical cycles and dynamical trans-port. Cloud motion monitoring has characterised the mean state of the atmospheric circulation as well as its variability. Low and middle latitudes show an almost constant zonal wind speed of 100+/-20 m/s at the cloud tops and vertical wind shear of 2-3 m/s/km. Towards the pole, the wind speed drops quickly and the vertical shear vanishes. The meridional poleward wind ranges from 0 to about 15 m/s and there is some indication that it may change its direction at high latitudes. Comparison of the thermal wind field derived from temperature sounding to the cloud tracked winds confirms the approximate validity of cyclostrophic balance, at least in the latitude range from 30 S to 70 S. Maps of the non-LTE infrared emissions in the lines of O2, NO, CO2, OH originating near the mesopause at 95-105 km altitude show that the airglow peak intensity occurs close to the anti-solar point and its location depends on species. These observations promise significant improvement of thermospheric circulation models.

Titov, Dmitri; Taylor, Fredric W.; Svedhem, Håkan; Titov, D.; Svedhem, H.; Taylor, F. W.; Bertaux, J.-L.; Drossart, P.; Haeusler, B.; Korablev, O. I.; Markiewicz, W. J.; Paetzold, M.; Piccioni, G.; Vandaele, A.-C.

4

Waves in the Mesosphere of Venus as seen by the Venus Express Radio Science Experiment VeRa  

Science.gov (United States)

The Venus Express Radio Science Experiment (VeRa) has retrieved more than 700 profiles of the mesosphere and troposphere of Venus. These profiles cover a wide range of latitudes and local times, enabling study of atmospheric wave phenomena over a range spatial scales at altitudes of 40-90 km. In addition to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves, and turbulence play a significant role in the development and maintenance of atmospheric super-rotation. Small-scale temperature variations with vertical wavelengths of 4 km or less have wave amplitudes reaching TBD km in the stable atmosphere above the tropopause, in contrast with much weaker temperature perturbations observed in the middle cloud layer below. The strength of gravity waves increases with latitude in both hemispheres. The results suggest that convection at low latitudes and topographical forcing at high northern latitudes—possibly in combination with convection and/or Kelvin-Helmholtz instabilities—play key roles in the genesis of gravity waves. Further, thermal tides also play an important role in the mesosphere. Diurnal and semi-diurnal wave modes are observed at different latitudes and altitudes. The latitudinal and height dependence of the thermal tide modes will be investigated.

Tellmann, Silvia; Häusler, B.; Hinson, D. P.; Tyler, G.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-10-01

5

Radio science investigations by VeRa onboard the Venus Express spacecraft  

Science.gov (United States)

The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13 cm ("X"- and "S"-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time, and polarization of the received signals. Simultaneous, coherent measurements at the two wavelengths allow separation of dispersive media effects from classical Doppler shift. VeRa science objectives include the following: Determination of neutral atmospheric structure from the cloud deck (approximately 40 km altitude) to 100 km altitude from vertical profiles of neutral mass density, temperature, and pressure as a function of local time and season. Within the atmospheric structure, search for, and if detected, study of the vertical structure of localized buoyancy waves, and the presence and properties of planetary waves. Study of the H 2SO 4 vapor absorbing layer in the atmosphere by variations in signal intensity and application of this information to tracing atmospheric motions. Scintillation effects caused by radio wave diffraction within the atmosphere can also provide information on small-scale atmospheric turbulence. Investigation of ionospheric structure from approximately 80 km to the ionopause (Venus atmosphere. Observation of forward-scattered surface echoes obliquely reflected from selected high-elevation targets with anomalous radar properties (such as Maxwell Montes). More generally, such bistatic radar measurements provide information on the roughness and density of the surface material on scales of centimeters to meters. Detection of gravity anomalies, thereby providing insight into the properties of the Venus crust and lithosphere. Measurement of the Doppler shift, propagation time, and frequency fluctuations along the interplanetary ray path, especially during periods of superior conjunction, thus enabling investigation of dynamical processes in the solar corona.

Häusler, B.; Pätzold, M.; Tyler, G. L.; Simpson, R. A.; Bird, M. K.; Dehant, V.; Barriot, J.-P.; Eidel, W.; Mattei, R.; Remus, S.; Selle, J.; Tellmann, S.; Imamura, T.

2006-11-01

6

Sulfuric acid vapor (H2SO4) abundance as a trace gas for atmospheric dynamics in the atmosphere of Venus derived from Venus Express Radio Science Experiment VeRa  

Science.gov (United States)

A roughly 20 km thick cloud layer, mostly consisting of liquid sulfuric acid, embraces the entire planet Venus between ca. 50 and 70 km altitude. A haze layer consisting of sulfuric acid vapor exists below ca. 50 km. A decrease in the Radio signal intensity caused by defocusing and absorption is observed by radio occultation experiments within the cloud and the sub - cloud region. The Venus Express spacecraft is orbiting Venus since 2006. The Radio Science Experiment VeRa probes the atmosphere with radio signals at 3.6 cm (X-Band) and 13 cm (S-Band) wavelengths. The absorption of the radio signal power is used to determine the abundance and the global distribution of H2SO4 in the Venus atmosphere down to an altitude of ca. 40 km. Vertical absorptivity profiles and resulting sulfuric acid vapor profiles are presented and compared with previous missions and other experiments on Venus Express. A distinct latitudinal dependence and a north/south symmetry are clearly visible. The global distribution of H2SO4 reflects the dynamics in the Venus atmosphere. The results are used to derive information on the transport processes in the lower and middle atmosphere.

Oschlisnoik, J.; Pätzold, M.; Tellmann, S.; Häusler, B.; Bird, M.; Andert, T.; Remus, S.

2013-09-01

7

Tracking Clouds on Venus using Venus Express Data  

Science.gov (United States)

In the US, a growing emphasis has been placed on the development of inclusive and authentic educational experiences which promote active participation by the K-12 learning community as well as the general public in NASA's earth and space science research activities. In the face of growing national and international budgetary constraints which present major challenges across all scientific research organizations around the world, the need for scientific communities to dramatically improve strategies for effective public engagement experiences, demonstrating the relevance of earth and space science research contributions to the citizenry, have become paramount. This presentation will provide an introduction to the online Venus Express Cloud tracking applet, an overview of feedback from educational users based on classroom/pilot implementation efforts, as well as the concept's potential viability for the promotion of expanded public participation in the analysis of data in future planetary exploration and research activities, nationally and internationally. Acknowledgements: We wish to acknowledge the contributions of Mr. Nishant Udgaonkar, a summer intern with the S.N. Bose Scholars Program, sponsored by the Science and Engineering Board, Department of Science and Technology, Government of India, the Indo-U.S. Science and Technology Forum, and the University of Wisconsin-Madison. We also wish to acknowledge the Space Science and Engineering Center as well as NASA for supporting this project.

Pertzborn, Rosalyn; Limaye, Sanjay; Markiewicz, Wojciech; Jasmin, Tommy; Udgaonkar, Nishant

2014-05-01

8

The global distribution of H2SO4 in the atmosphere of Venus as a trace gas for atmospheric dynamics derived from Venus Express Radio Science Experiment VeRa  

Science.gov (United States)

The entire planet Venus is covered by a roughly 20 km thick cloud layer, consisting of liquid and gaseous sulfuric acid between ca. 50 and 70 km altitude. The density of the gaseous part increases and forms a ca. 15 km thick haze layer below ca. 50 km. The haze layer is responsible for the absorption of radio signals during radio occultation experiments. The absorption of the radio signal is a tool to derive the amount of H2SO4 as a function of altitude and latitude. The Radio Science Experiment VeRa sounds the Venus atmosphere with radio signals at 3.6 cm (X-Band) and 13 cm (S-Band) wavelengths. The derived atmospheric absorption profiles show the global H2SO4 distribution as a tracer of the predominant transport processes in the atmosphere of Venus. Vertical sulfuric acid vapor profiles are presented and compared with previous missions and other experiments on Venus Express. A distinct latitudinal H2SO4 gradient and a southern northern symmetry are clearly visible. Furthermore indications for temporal H2SO4 variations were found, at least at higher latitudes. The observed global H2SO4 distribution is used to derive information on the transport processes in the lower and middle atmosphere with respect to a 2D transport model.

Oschlisniok, J.; Pätzold, M.; Tellmann, S.; Häusler, B.; Bird, M.; Andert, T.; Remus, S.; Herrmann, M.

2014-04-01

9

Post-Venus Express exploration of Venus : the Venus Entry Probe Initiative  

Science.gov (United States)

The planet Venus -- our neighbour in the solar system and twin sister of the Earth -was once expected to be very similar to the Earth However the space missions to the planet discovered a world completely different from ours The fundamental mysteries in the physics of Venus are related to the composition and dynamics of the atmosphere physics of the cloud layer and greenhouse effect surface mineralogy evolution of the surface and volatile inventory Despite the fact that both Earth and Venus were formed in the same region of the solar system the planets followed dramatically different evolutionary paths Understanding the reasons for this divergence would shed a light on the processes of origin and evolution of all terrestrial planets including Earth Early missions to Venus in 1960-90 included a great variety of robotic spacecraft fly-bys orbiters landers and balloons They established basic understanding of the conditions prevailing in the atmosphere and on the surface of Venus In the same time they raised a number of fundamental questions concerning the mechanisms and processes that formed and are maintaining these conditions The new era of Venus exploration began with the launch of the ESA Venus Express spacecraft in November 2005 The spacecraft will deliver a powerful suite of remote sensing instruments into orbit around the planet The mission will perform a global survey of the Venus atmosphere and plasma environment The Japanese Planet-C mission scheduled for launch in 2010 will focus on meteorological monitoring from orbit These

Chassefière, E.; Roos-Serote, M.; Titov, D.; Wilson, C.; Witasse, O.; Vepi Team

10

Venus  

Science.gov (United States)

Venus is Earth's nearest planetary neighbor and has fascinated mankind since the dawn of history. Venus' clouds reflect most of the sunlight shining on the planet and make it the brightest object in the sky after the Sun and Moon. Venus is visible with the naked eye as an evening star until a few hours after sunset or as a morning star shortly before sunrise. Many ancient civilizations observed and worshipped Venus, which had a different name in each society, for example, Ishtar to the Babylonians, Aphrodite to the Greeks, Tai'pei to the Chinese, and Venus to the Romans. Venus has continued to play an important role in myth, literature, and science throughout history.

Fegley, B., Jr.

11

A New Method for the Detection of Small-scale Wave-like Features in the Venusian Atmosphere with the Venus Express Radio Science Experiment VeRa  

Science.gov (United States)

Wave structures are common phenomena in planetary atmospheres. Different kind of waves were observed in the thick Venus atmosphere[1,2,3]. Measurements at high temporal and spatial resolution are needed to identify such structures. The Venus Express Radio Science Experiment VeRa observed about 700 vertical profiles of temperature, pressure and neutral number density in the Venus atmosphere. The profiles cover the altitude range between 40km and 90-100km. Variations in the temperature profiles were interpreted as wave structures down to 60km[1]. One kind of waves are gravity waves which propagate vertically in the Venusian atmosphere. One open question is the contribution of topographical features to their formation. VeRa data may clarify wave formation mechanisms for associated altitude regions in particular using occultation open-loop data. The processing of the open-loop data may reveal a spectrum of wave frequencies with the prospect to detect small-scale atmospheric phenomena. Multipath effects remain still a problem in particular within the cloud layer which can only be addressed with open-loop data.

Herrmann, M.; Häusler, B.; Pätzold, M.; Tellmann, S.; Oschlisniok, J.

2014-04-01

12

Large scale atmospheric waves in the Venus mesosphere as seen by the VeRa Radio Science instrument on Venus Express  

Science.gov (United States)

Atmospheric waves on almost all spatial scales have been observed in the Venus atmosphere in various atmospheric regions. They play a crucial role in the redistribution of energy, momentum, and atmospheric constituent and are thought to be involved in the development and maintenance of the atmospheric superrotation.

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2014-04-01

13

O+ pickup ions outside of Venus' bow shock: Venus Express observations  

Science.gov (United States)

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. In addition, Galileo also did not capture O+ outside bowshock during its 1-hour Venus flyby though its plasma instrument had ability to cover the energy band of O+ pickup ions [4]. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We have examined the IMA data during the solar minimum period 2006-2010, and identified 80 cases with clear signature of O+ pickup ion. With these observations, we can determine the location and the scale height of the source region of O+ pickup ions and describe the relationship between the behavior of these O+ and the upstream solar wind condition. The results would provide new information for numerical simulation of plasma environment near Venus and contribute to estimation of total O+ ion loss from Venus. Reference: [1] Dubinin, E., M. Fränz, J. Woch, E. Roussos, S. Barabash, R. Lundin, J. D. Winningham, R. A. Frahm, and M. Acuña (2006a), Plasma morphology at Mars: Aspera-3 observations, Space Sci. Rev., 126, 209-238, doi:10.1007/s11214-006-9039-4. [2] Cravens, T. E., A. Hoppe, S. A. Ledvina, and S. McKenna-Lawlor (2002), Pickup ions near Mars associated with escaping oxygen atoms, J. Geophys. Res., 107, 1170, doi:10.1029/2001JA000125. [3] Luhmann, J. G., S. A. Ledvina, J. G. Lyon, and C. T. Russell (2006), Venus O+ pickup ions: Collected PVO results and expectations for Venus Express, Planet. Space Sci., 54, 1457-1471, doi:10.1016/j.pss.2005.10.009. [4] Williams, D. J. et al.(1991), Energetic Particles at Venus: Galileo Results. Science 253, 1525-1528.

Wei, Yong; Fraenz, Markus; Dubinin, Eduard; Zhang, Tielong; Jarvinen, Riku; Wan, Weixing; Kallio, Esa; Collinson, Glyn; Barabash, Stars; Norbert, Krupp; Woch, Joachim; Lundin, Rickard; delva, Magda

2013-04-01

14

Venus  

Science.gov (United States)

Venus is Earth's nearest planetary neighbor, and has fascinated mankind since the dawn of history. Venus' clouds reflect most of the sunlight shining on the planet and make it the brightest object in the sky after the Sun and Moon. Venus is visible with the naked eye as an evening star until a few hours after sunset, or as a morning star shortly before sunrise. Many ancient civilizations observed and worshipped Venus, which had a different name in each society, e.g., Ishtar to the Babylonians, Aphrodite to the Greeks, Tai'pei to the Chinese, and Venus to the Romans (Hunt and Moore, 1982). Venus has continued to play an important role in myth, literature, and science throughout history. In the early seventeenth century, Galileo's observations of the phases of Venus showed that the geocentric (Ptolemaic) model of the solar system was wrong and that the heliocentric (Copernican) model was correct. About a century later, Edmund Halley proposed that the distance from the Earth to the Sun (which was then unknown and is defined as one astronomical unit, AU) could be measured by observing transits of Venus across the Sun. These transits occur in pairs separated by eight years at intervals of 105.5 yr and 121.5 yr in an overall cycle of 243 yr, e.g., June 6, 1761, June 3, 1769; December 9, 1874, December 6, 1882, June 8, 2004, June 6, 2012, December 11, 2117, and December 8, 2125. The first attempted measurements of the astronomical unit during the 1761 transit were unsuccessful. However, several observers reported a halo around Venus as it entered and exited the Sun's disk. Thomas Bergman in Uppsala and Mikhail Lomonosov in St. Petersburg, independently speculated that the halo was due to an atmosphere on Venus. Eight years later observations of the 1769 solar transit (including those made by Captain Cook's expedition to Tahiti) gave a value of 1 AU=153 million kilometers, ~2.3% larger than the actual size (149.6 million kilometers) of the astronomical unit (Woolf, 1959; Maor, 2000).

Fegley, B., Jr.

2003-12-01

15

MESSENGER and Venus Express Observations of the Solar Wind Interaction with Venus  

Science.gov (United States)

At 23:08 UTC on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude of 338 kin during its final flyby of Venus en route to its 2011 orbit insertion at Mercury. The availability of the simultaneous Venus Express solar wind and interplanetary magnetic field measurements provides a rare opportunity to examine the influence of upstream conditions on this planet's solar wind interaction. We present MESSENGER observations of new features of the Venus - solar wind interaction including hot flow anomalies upstream of the bow shock, a flux rope in the near-tail and a two-point determination of the timescale for magnetic flux transport through this induced magnetosphere. Citation: Stavin, J. A., et al. (2009), MESSENGER and Venus Express observations of the solar wind interaction with Venus,

Slavin, James A.; Acuna, Mario H.; Anderson, Brian J.; Barabash, Stas; Benna, Mehdi; Boardsen, Scott A.; Fraenz, Markus; Gloeckler, George; Gold, Robert E.; Ho,George C.; Korth, Haje; Krimigis, Stamatios M.; McNutt, Ralph L., Jr.; Raines, Jim M.; Sarantos, Menelaos; Solomon, Sean C.; Zhang, Tielong; Zurbuchen, Thomas H.

2009-01-01

16

Venus Express uurib Maa kurja kaksikut / ref. Triin Thalheim  

Index Scriptorium Estoniae

9. novembril startis Baikonuri kosmodroomilt Veenusele Euroopa Kosmoseagentuuri sond Venus Express, mis peaks planeedi atmosfääri sisenema aprillis. Teadlaste sõnul peab sondi saadetav info aitama mõista naaberplaneedi kliimat ja atmosfääri ning tooma selgust, kas Maa võib kunagi Veenuse sarnaseks muutuda. Lisaks joonis: Venus Express

2005-01-01

17

Venus Express: five years of atmospheric observations  

Science.gov (United States)

Since April 2006 Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. More than 300 radio-occultation experiments covering all latitudes and local times on had been acquired so far. They reveal highly variable temperature structure in the mesosphere and within the clouds. Joint analysis of several experiments indicated coordinated latitudinal changes of the cloud top structure with high dispersed cloud tops in the low latitudes and relatively low dense clouds in the cold collar and the polar region. UV imaging monitors strongly variable cloud patterns showing for the first time middle latitudes and polar regions in unprecedented detail. Tracking cloud features at both UV and thermal infrared wavelengths characterizes the global wind field and its variations, including pioneering reconstruction of the velocity patterns inside the polar eye of the hemispheric vortex. The observations are supported by development of General Circulation Models. Spectroscopic observations in both nadir and occultation geometries continuously sound composition of the mesosphere and discover significant latitudinal variations of water vapour and sulphur dioxide that form cloud particles. Contrary to expectations the observations indicate no apparent correlations with UV brightness patterns. Non-LTE infrared emissions in the lines of O2, NO, CO2, OH originating near the mesopause at 95-105 km altitude are being mapped on the night side. The data show that the airglow peak intensity occurs close to the anti-solar point and its location depends on particular specie. A consistent picture of the climate on the neighbouring planet is emerging from the Venus Express observations supported by extensive modelling efforts. The results of the studies will be published in about 40 original papers in the special issue of Icarus to appear in 2011.

Titov, D. V.; Svedhem, H.; Wilson, C.

2011-10-01

18

The dayside ionospheres of Mars and Venus: Comparing a one-dimensional photochemical model with MaRS (Mars Express) and VeRa (Venus Express) observations  

Science.gov (United States)

The electron density distributions of the lower ionospheres of Mars and Venus are mainly dependent on the solar X-ray and EUV flux and the solar zenith angle. The influence of an increasing solar flux is clearly seen in the increase of the observed peak electron density and total electron content (TEC) of the main ionospheric layers. The model “Ionization in Atmospheres” (IonA) was developed to compare ionospheric radio sounding observations, which were performed with the radio science experiments MaRS on Mars Express and VeRa on Venus Express, with simulated electron density profiles of the Mars and Venus ionospheres. This was done for actual observation conditions (solar flux, solar zenith angle, planetary coordinates) from the bases of the ionospheres to ?160 km altitude. IonA uses models of the neutral atmospheres at ionospheric altitudes (Mars Climate Database (MCD) v4.3 for Mars; VenusGRAM/VIRA for Venus) and solar flux information in the 0.5-95 nm wavelength range (X-ray to EUV) from the SOLAR2000 data base. The comparison between the observed electron density profiles and the IonA profiles for Mars, simulated for a selected MCD scenario (background atmosphere), shows that the general behavior of the Mars ionosphere is reproduced by all scenarios. The MCD “low solar flux/clear atmosphere” and “low solar flux/MY24” scenarios agree best (on average) with the MaRS set of observations, although the actual Mars atmosphere seemed to be still slightly colder at ionospheric altitudes. For Venus, the VenusGRAM model, based on VIRA, is too limited to be used for the IonA simulation of electron density profiles. The behavior of the V2 peak electron density and TEC as a function of solar zenith angle are in general reproduced, but the peak densities and the TEC are either over- or underestimated for low or high solar EUV fluxes, respectively. The simulated V2 peak altitudes are systematically underestimated by 5 km on average for solar zenith angles less than 45° and the peak altitudes rise for zenith angles larger than 60°. The latter is the opposite of the observed behavior. The explanation is that VIRA and VenusGRAM are valid only for high solar activity, although there is also very poor agreement with VeRa observations from the recent solar cycle, in which the solar activity increases to high values. The disagreement between the observation and simulation of the Venus electron density profiles proves, that the true encountered Venus atmosphere at ionospheric altitudes was denser but locally cooler than predicted by VIRA.

Peter, Kerstin; Pätzold, Martin; Molina-Cuberos, Gregorio; Witasse, Olivier; González-Galindo, F.; Withers, Paul; Bird, Michael K.; Häusler, Bernd; Hinson, David P.; Tellmann, Silvia; Tyler, G. Leonard

2014-05-01

19

Post-Venus Express exploration of Venus : an in-situ mission to characterize Venus climate evolution  

Science.gov (United States)

The planet Venus - our neighbour in the solar system and twin sister of the Earth - was once expected to be very similar to the Earth. However the space missions to the planet discovered a world completely different from ours. The fundamental mysteries in the physics of Venus are related to the composition and dynamics of the atmosphere, physics of the cloud layer and greenhouse effect, surface mineralogy, evolution of the surface and volatile inventory. Despite the fact that both Earth and Venus were formed in the same region of the solar system, the planets followed dramatically different evolutionary paths. Understanding the reasons for this divergence would shed a light on the processes of origin and evolution of all terrestrial planets including Earth. A new mission to Venus is under study. It consists of a set of probes (balloon probe, descent probes) devoted to the characterization of atmospheric chemical cycles, atmospheric electrical/ electromagnetic activity, low atmosphere dynamics, surface/ atmosphere thermo-chemical interactions, surface mineralogy and geology, with an emphasis on past climate evolution (noble gas/ isotope composition of the atmosphere). Some orbital science is planned, in complement to in-situ science. An atmosphere sample return is also considered. Information about current activity may be found at http://www.aero.jussieu.fr/VEP/, together with documents describing the present state of thoughts about scientific priorities and possible mission scenarios.

Chassefiere, E.; Aplin, K.; Ferencz, C.; Lopez-Moreno, J.; Leitner, J.; Marty, B.; Roos-Serote, M.; Titov, D.; Wilson, C.; Witasse, O.; Vep Team

20

The search for active volcanism on Venus with Venus Express/VIRTIS data  

Science.gov (United States)

The composition of the lower atmosphere of Venus is of primary importance in understanding the past and indeed current evolution of climatology on this most enigmatic of planets In discovering the near infrared windows centered at 2 3 1 7 and 1 18 microns Allen and Crawford 1 in 1983 paved the way for the lower 40km of the atmosphere to be probed remotely from space This has led Venus Express to carry imaging spectrometers such as VIRTIS to make full use of this phenomenon Some fundamental questions concerning the exact makeup of the atmosphere will be answered by analyzing VIRTIS data Data collected from past observations indicate the possibility of current volcanic activity on the surface of Venus The monitoring of SO 2 at the cloud tops indicate a steady drop in concentration suggesting a possible source of SO 2 is due to volcanism 2 whilst deep atmospheric values below the clouds suggest a uniform mixing ratio 3 The analysis VIRTIS data at 2 48 micron window will no doubt shed light on this matter Analysis of the micro-window complex at 1 18 microns shows that we can image the surface of the planet in the infrared whilst negating most of the effects of the atmosphere 4 We can monitor the surface brightness temperatures to look for hot spots indicative of volcanic plumes another key goal of Venus Express and VIRTIS We have developed a radiative transfer model to analyse Venus Express VIRTIS data in the near infrared windows The retrieval model uses the correlated-k distribution method which incorporates the use

Tsang, C. C. C.; Virtis Team

 
 
 
 
21

Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but reveal at the same time that wave sources may not only exist at the bow shock, but also in the magnetosheath.

L. Guicking

2010-04-01

22

Composition and chemistry of the Venusian atmosphere after Venus Express  

Science.gov (United States)

The ESA/Venus Express orbiter mission is expected to end before the end of this year (2014), and time has come to summarize its results and examine how they changed our view of this planet. Venus Express instruments (especially the spectrometers VIRTIS and SPICAV/SOIR) have been addressing numerous scientific issues since 2006, among which remote sensing of many minor species from the lower troposphere up to the mesosphere at various latitudes and local solar time, often evidencing spatial or temporal variability. In preparation of a new synthesis of our current knowledge about Venusian atmospheric chemistry and composition to be included in the Venus III book (expected to be published in 2015), we shall present an overview of the most significant updates in this domain. A non-exhaustive list of the sub-topics we would like to address is; (1) Lower tropospheric measurements: Venus Express has been able to study in detail most of the thermal infrared windows, yielding extensive night side measurements of some key minor species (CO, OCS, H_2O, HDO, SO_2) (2) Profiles at an unparalleled vertical resolution of many minor species in the lower mesosphere thanks to stellar and solar occultation techniques. (3) Spatial and temporal variability of minor species at various scales, the most striking example being SO_2 above cloud top. (4) New theoretical understanding and modeling of the interplay between the various chemical cycles (carbon, sulfur, halogens) and the condensed phase particulate matter from the clouds and hazes, based on the newest available observational constraints from Venus Express and ground-based telescopes.

Marcq, Emmanuel

23

Magnetic fields in the Venus ionosphere: Dependence on the IMF direction—Venus express observations  

Science.gov (United States)

The structure of the magnetized ionosphere of Venus is investigated using the magnetometer and plasma (Analyzer of Space Plasmas and Energetic Atoms 4) data from the Venus Express spacecraft. Observations surveying the low-altitude (h ? 250 km) ionosphere were made at solar zenith angles ? 75°. The magnetic field permeating the Venus ionosphere at solar minimum conditions increases at low altitudes and reaches a maximum at an altitude of ˜200 km. The orientation of the magnetic field in the peak is almost insensible to the magnetic field direction in the solar wind. For both sector polarities of the IMF, the magnetic field vector has a dominant dawn-dusk component. The topology of the magnetic field also occurs different for different signs of the cross-flow component of the IMF revealing either a sudden straightening with liberation of the magnetic field stresses or a closing into a loop. We discuss different mechanisms of the peak formation including local magnetization, a weak intrinsic planetary field, a dipole field induced by eddy currents, a remnant origin, or giant flux ropes. All of them fail to explain most of the observed features. We suggest that a decoupling of ion and electron motion at low altitudes due to ion-neutral collisions results in currents which produce different field configurations depending on the IMF orientation.

Dubinin, E.; Fraenz, M.; Zhang, T. L.; Woch, J.; Wei, Y.

2014-09-01

24

Venus Express Contributions to the Study of Planetary Lightning  

Science.gov (United States)

Jupiter, and Saturn are expected to generate the electrical potential differences in their clouds sufficient to cause a breakdown in the atmosphere,creating a conducting path for the electric potential to discharge. This high-energy phenomenon creates a hot, high-pressure channel that enables chemical reactions not possible under usual local thermodynamic conditions. Thus it is of some interest to determine if lightning occurs in an atmosphere. While Venus is not usually considered one of the wet planets, lightning has been an object of interest since the Venera landers. It was observed with electromagnetic coils on Venera 11, 12, 13, 14 landers [2]. It was observed with a visible spectrometer on the Venera 9 orbits [1]. It was mapped during solar occultations by the electric antenna on the Pioneer Venus Orbiter [4]. These measurements revealed extensive lightning activity with an electromagnetic energy flux similar to that on Earth. However, the observations were limited in number in the atmosphere and to the nightside from orbit. In order to improve the understanding of Venus lightning, the Venus Express magnetometer was given a 128-Hz sampling rate that could cover much of the ELF frequencies at which lightning could be observed in the weak magnetic fields of the Venus ionosphere [5]. This investigation was immediately successful [3], but mastering the cleaning of the broadband data took several years to accomplish. Furthermore, the high polar latitudes of VEX periapsis were not the ideal locations to conduct the more global survey that was desired. Fortunately, after precessing poleward over the first few years the latitude of periapsis has returned to lower latitudes(Figures 1 and 2) and active electrical storms are now being studied. The charged constituent of the Venus atmosphere need not be water. In fact, we believe it is H2SO4 which polarizes much as water does and which freezes and melts at similar temperatures. If it is H2SO4, we would expect the constituent to be sensitive to the rate of Venus volcanism releasing sulfur and sulfur dioxide into the atmosphere. This is one correlation we are anxious to pursue on future missions.

Russell, C. T.; Hart, R. A.; Zhang, T. L.

2014-04-01

25

Future Exploration of Venus  

Science.gov (United States)

Venus has been the target of exploration for half a century, before the successful Mariner 2 fly-by in December 1962. The decade after that was marked by growing sophistication in the instruments and spacecraft. During the second decade of Venus exploration (1972 - 1981) the instruments and spacecraft had advanced to make the first detailed survey of the planet and image the surface. During the third decade Venus was explored with more advanced instruments such as synthetic aperture radar and by balloons - the only balloons in another atmosphere ever flown till present. Then came a long pause until 2005 when ESA launched Venus Express, which is still orbiting the planet and returning data. The nearly two-dozen missions flown to Venus have painted a puzzling picture of Venus - we still do not have answers to some key questions. The foremost is why did Venus evolve so differently from Earth? International space agencies and scientists have been considering various approaches to exploring Venus through small and large missions. The Venus Exploration Analysis Group (NASA) has developed a Venus Exploration Roadmap and a comprehensive list of goals, objectives and investigations (www.lpi.usra.edu/vexag), but an international coordinated, comprehensive plan to explore Venus is needed. To fill this void, the COSPAR International Venus Exploration Working Group (IVEWG) has been active in fostering dialog and discussions among the space faring agencies. One small step in the future exploration of Venus is the formation of a joint Science Definition Team (SDT) (NASA and Roscosmos/IKI) for Russia’s Venera-D mission in early 2014. The team is expected to submit a report to respective agencies in early 2015. Towards identifying key surface regions and atmospheric regions of Venus, a workshop is being held in May 2014 by VEXAG to seek community input. It is likely that calls for proposals for missions will also be announced under the M class by ESA and under the Discovery Program by NASA during 2014. Given that the science questions about Venus are many - ranging from the surface and interior and extending into the atmosphere to 120 km and beyond, it is likely that there will be opportunities for other efforts to contribute to the comprehensive exploration of Venus. If undertaken in a coordinated and collaborative manner, we may make substantial progress in understanding Venus, why and/or how it evolved differently from Earth. This knowledge will help us understand Earth-like rocky planets around other stars that are being discovered at a rapid pace now.

Limaye, Sanjay

26

First results of an Investigation of Sulfur Dioxide in the Ultraviolet from Pioneer Venus through Venus Express  

Science.gov (United States)

The Laboratory for Atmospheric and Space Physics is carrying on a project to restore and preserve data products from several past missions for archival and use by the scientific community. This project includes the restoration of data from Mariner 6/7, Pioneer Venus, Voyager 1/2, and Galileo. Here, we present initial results of this project that involve Pioneer Venus Orbiter Ultraviolet Spectrometer (PVO UVS) data. Using the Discrete Ordinate Method for Radiative Transfer (DISORT), we generate a suite of models for the three free parameters in the upper atmosphere of Venus in which we are interested: sulfur dioxide abundance at 40mb, scale height of sulfur dioxide, and the typical radius of the upper haze particles (assumed to be composed of 84.5% sulfuric acid). We calculate best fits to our radiative transfer model results for multi-spectral images taken with PVO UVS, as well as the 'visible' channel (includes wavelengths from 290nm to about 1000nm) of the mapping mode of the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS-M-Vis) on the Venus Express spacecraft, currently orbiting Venus. This work is funded though the NASA Planetary Mission Data Analysis Program, NNH08ZDA001N.

McGouldrick, Kevin; Molaverdikhani, K.; Esposito, L. W.; Pankratz, C. K.

2010-10-01

27

Europe Scores New Planetary Success: Venus Express Enters Orbit around the Hothouse Planet  

Science.gov (United States)

During the next four weeks, the Venus Express probe will perform a series of manoeuvres to reach the scheduled operational orbit for its scientific mission. It will move from its current highly elongated 9-day orbit to a 24-hour polar orbit, culminating at 66,000 km. From this vantage point, the orbiter will conduct an in-depth observation of the structure, chemistry and dynamics of the atmosphere of Venus for at least two Venusian days (486 Earth days). Enigmatic atmosphere From previous missions to Venus as well as observations directly from Earth, we already know that our neighbouring planet is shrouded in a thick atmosphere where extremes of temperature and pressure conditions are common. This atmosphere creates a greenhouse effect of tremendous proportions as it spins around the planet in four days in an unexplained “super-rotation” phenomenon. The mission of Venus Express will be to carry out a detailed characterisation of this atmosphere, using state-of-the-art sensors in order to answer the questions and solve the mysteries left behind by the first wave of explorers. It will also be the first Venus orbiter to conduct optical observations of the surface through “visibility windows” discovered in the infrared spectrum.V The commissioning of the onboard scientific instruments will begin shortly and the first raw data are expected within days. The overall science payload is planned to be fully operational within two months. Europe explores the Solar System With this latest success, ESA is adding another celestial body to its range of solar system studies. ESA also operates Mars Express around Mars, SMART-1 around the Moon and is NASA’s partner on the Cassini orbiter around Saturn. In addition, ESA is also operating the Rosetta probe en route to comet 67P/Churyumov-Gerasimenko. It should reach its target and become the first spacecraft ever to enter orbit around a comet nucleus by 2014. Meanwhile, ESA also plans to complete the survey of our celestial neighbours with the launch of the BepiColombo mission to Mercury in 2013. “With the arrival of Venus Express, ESA is the only space agency to have science operations under way around four planets: Venus, the Moon, Mars and Saturn” underlines Professor David Southwood, the Director of ESA’s science programmes. “We are really proud to deliver such a capability to the international science community.” “To better understand our own planet, we need to explore other worlds in particular those with an atmosphere,” said Jean-Jacques Dordain, ESA Director General. “We’ve been on Titan and we already are around Mars. By observing Venus and its complex atmospheric system, we will be able to better understand the mechanisms that steers the evolution of a large planetary atmosphere and the change of climates. In the end, it will help us to get better models of what is actually going on in our own atmosphere, for the benefit of all Earth citizens.” State-of-the-art science package Venus Express was developed for ESA by a European industrial team led by EADS Astrium incorporating 25 main contractors from 14 European countries. Its design is derived from that of its highly successful predecessor, Mars Express, and its payload accommodates seven instruments including upgraded versions of three instruments developed for Mars Express and two for Rosetta. The PFS spectrometer will determine the temperature and composition profile of the atmosphere at very high resolution. It will also monitor the surface temperature and search for hot spots from possible volcanic activity. The UV/infrared SpicaV/SOIR spectrometer and the VeRa radioscience experiment will probe the atmosphere by observing the occultation of distant starts or the fading of radio signals on the planetary limb. SpicaV/SOIR will be particularly looking for traces of water molecules, molecular oxygen and sulphur compounds, which are suspected to exist in the atmosphere of Venus. The Virtis spectrometer will map the different layers of the atmosphere and provide imagery of the cloud systems at multipl

2006-04-01

28

VENUS EXPRESS: a four-year survey of the atmosphere of Venus  

Science.gov (United States)

Since April 2006 Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. A consistent picture of the climate on Venus is emerging on the basis of the new data, which enables us to provide an overview of the global temperature structure, the composition and its variations, the cloud morphology at various levels, the atmospheric dynamics and general circulation, and near-infrared emissions from trace species such as oxygen in the mesosphere. Vertical profiles of atmospheric temperature in the mesosphere and upper troposphere show strong variability correlated with changes in the cloud top structure and many fine details indicating dynamical processes. Temperature sounding also shows that the main cloud deck at 50-60 km is convectively unstable over large portion of the planet, in agreement with the analysis of UV images. Imaging also reveals strong latitudinal variations and significant temporal changes in the global cloud top morphology, which will inevitably modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from ~72 km in the low and middle latitudes to ~64 km in the polar region, marking vast polar depressions that form as a result of the Hadley-type meridional circulation. Stellar and solar occultation measurements have revealed an extended upper haze of submicron particles and provided information on its optical properties. Solar occultation observations and deep atmosphere spectroscopy in several spectral transparency windows have quantified the distribution of the major trace gases H2O, SO2, CO, COS and their variations above and below the clouds, and so provided important input and validation for models of chemical cycles and dynamical transport. Cloud motion monitoring has characterised the mean state of the atmospheric circulation as well as its variability. Low and middle latitudes show an almost constant zonal wind speed of 100+/-20 m/s at the cloud tops and vertical wind shear of 2-3 m/s/km. Towards the pole, the wind speed drops quickly and the vertical shear vanishes. The meridional poleward wind ranges from 0 to about 15 m/s and there is some indication that it may change its direction at high latitudes. Comparison of the thermal wind field derived from temperature sounding to the cloud tracked winds confirms the approximate validity of cyclostrophic balance, at least in the latitude range from 30 S to 70 S. Non-LTE infrared emissions in the lines of O2, NO, CO2, OH originating near the mesopause at 95-105 km altitude were detected and mapped on the night side. The data show that the airglow peak intensity occurs close to the anti-solar point and its location depends on particular specie. These observations result in significant improvement of thermospheric circulation models.

Titov, Dmitriy; Svedhem, Hakan; Taylor, Fredric W.

2010-05-01

29

Limb Darkening study using Venus nightside infrared spectra from VIRTIS-Venus Express data  

Science.gov (United States)

The Limb Darkening (LD) effect consists in an attenuation of the measured radiance at increasing emergence angles, due to the larger portion of the atmosphere traversed by the radiation observed at higher emergence angles. The behaviour of radiance emerging with atmosphere as function of the emergence angle (i.e., the Limb Darkening Function) is related to several atmosphere and cloud properties, e.g., atmospheric opacity, temperature lapse rate, aerosol single scattering albedo, optical depth, cloud particles size, cloud scale height. In addition, the retrieval of the Limb Darkening Function allows the computation of radiances as they would be acquired in Nadir observations, which is an important process of data reduction. In this work Limb Darkening is studied on infrared images of the Venus nightside. The images are provided by the VIRTIS instrument (Visible and InfraRed Thermal Imaging Spectrometer) onboard the Venus Express mission. Analysis is performed at wavelengths characterised by emission coming from below the clouds (i.e., 1.03 ?m, 1.31 ?m, 1.74 ?m, 2.30 ?m) and from upper clouds (i.e., 3.72 ?m, 4.00 ?m), respectively. In the first case, the Limb Darkening Function is retrieved at different latitude ranges (-40° to 0°, -50° to -40°, -60° to -50°, -70° to -60°) and different optical depths. To this end, a novel approach is developed, based on a statistical analysis of observed data. This statistical analysis is possible thanks to the very extended dataset provided by the VIRTIS instrument. These empirical Limb Darkening Functions are then compared and interpreted with the aid of radiative transfer models. An agreement between our results and results of synthetic models is found between -60° and 0°, allowing us to consider our approach well validated. Furthermore, by means of a detailed analysis of the LDFs obtained at different latitudes, it is possible to infer a slight increase of the mode3/mode2 density ratio between -60° and -50°, that becomes larger between -70° and -60°: the mode3/mode2 ratio inferred at these latitudes is about two times its equatorial value. The study of Limb Darkening from upper clouds region allows to obtain the upper cloud scale height, its variation with the atmospheric height, and the brightness temperature at different latitudes (the latitude intervals used are the same of the low atmosphere study). All the latitudes are characterised by a thin layer at the upper clouds base having a short scale height (i.e., interval. Between -50° and 0°, the retrieved scale height is about 4 km (i.e., 3.7±0.3 km between -40° and 0° and 4.5±0.8 km between -50° and -40°) and is constant with the height. Between -60° and -50°, a scale height of 4-5 km is found at low temperatures (226-231 K), whereas at higher temperature, we are able to give a lower (2-3 km) and an upper (7-9 km) limit. Between -70° and -60° no Limb Darkening is observed, suggesting a low scale height (i.e., <1 km), as well as a low lapse rate.

Longobardo, Andrea; Palomba, Ernesto; Zinzi, Angelo; Piccioni, Giuseppe; Tsang, Constantine C. C.; Drossart, Pierre

2012-08-01

30

Investigation of winds in Venus mesosphere by digital method using UV images from VMC aboard Venus Express.  

Science.gov (United States)

Investigation of winds at the top cloud layer is important for understanding the global circulation of the Venus atmosphere. The Venus Monitoring Camera (VMC) aboard Venus Express has acquired a huge number of UV (365 nm) images. UV images of top cloud layer are customary to obtain the wind velocity due to their high contrast. Visual estimation of wind velocities is a labor intensive procedure. Authors have developed a digital method to estimate velocities of shifts of cloud details. The method is based on analysis of correlations between two UV images acquired at different moments. The method takes into account the change of a correlation function due to latitudinal peculiarities of cloud morphology and eliminates image regions which are far from the sub-spacecraft point. The digital method provides with good vector coverage of the Venus day side (9-16 local time) from the equator to high latitudes. The best agreement between the digital and visual methods is observed at low latitudes (below 35S). The discrepancy at higher latitudes is related to complicated cloud morphology, namely domination of streaks, which increases errors in the zonal wind speed. The method is productive for long-scale circulation at the top cloud layer. Sizes of regions for correlation were chosen empirically as a trade-off of sensitivity against noise immunity and varies from 10x7.5 ° to 20x10 ° depending on grid step. 580 orbits covering ten Venus years have been processed by using the digital method. The database of shift vectors counts about 400000 records. The mean wind speed at low latitudes is about 100 m/s. Wind vector fields were obtained for every orbit. The zonal wind speed in the equatorial region exhibits short-period (about 4.8 days) and long-period variations (long-term trend). Vector field averaged by all orbits show deviations of the main stream up to 5 degrees poleward in the early afternoon (12.5-14.5h) at 45-55S. The mean absolute value of the wind speed increases from 59.38 m/s at 10-12h to 76.46 m/s at 12.5-14.5h at the same latitude interval.

Patsaeva, Marina; Khatuntsev, Igor; Ignatiev, Nikolai

2013-04-01

31

The latest results on the energetic neutral atoms and plasma of Venus from the ASPERA-4 instrument of Venus Express  

Science.gov (United States)

The Venus Express mission carries the instrument ASPERA-4 Analyzer of Space Plasmas and Energetic Atom to perform for the first time comprehensive plasma measurements at Venus ASPERA-4 is a replica of the instrument ASPERA-3 for the Mars Express mission orbiting Mars for about 2 years The general scientific objective of the ASPERA-4 experiment is to study the solar wind - atmosphere interaction and characterize the plasma atmospheric escape through energetic neutral atom ENA imaging and in-situ ion and electron measurements The ASPERA-4 instrument comprises four sensors two ENA sensors and an electron and ion spectrometer The Neutral Particle Imager NPI provides measurements of the integral ENA flux in the energy range 0 1 - 60 keV with no mass and energy resolution but comparatively high angular resolution 4 6 deg x 11 5 deg The Neutral Particle Detector NPD provides measurements of the ENA flux in the energy range 0 1 - 10 keV resolving velocity and mass H and O with a coarse angular resolution The Electron Spectrometer ELS is a standard top-hat electrostatic analyzer in a very compact design with the high 8 energy resolution to perform photoelectron spectroscopy These three sensors are located on a scanning platform to cover ideally the full sphere Ion Mass Analyzer IMA provides ion measurements in the energy range 0 01 - 30 keV q for the main ion components 1 2 4 16 amu q and the group of molecular ions 20 - 80 amu q The instantaneous field of view is 4 6 deg x 360 deg Electrostatic sweeping performs the elevation 90 deg

Barabash, S.; Sauvaud, J.-A.; Aspera-4

32

A global comparison between MaRS/VeRa radio science observations of the Mars and Venus dayside ionospheres and the IonA model  

Science.gov (United States)

The radio science experiments MaRS on Mars Express and VeRa on Venus Express are sounding the atmosphere and ionosphere of Venus since 2004 and 2006, respectively. To date, more than 600 complete vertical electron density profiles have been recorded with each experiment for a large variety of observational parameters (solar zenith angle, latitude, local time, season, solar activity cycle). IonA (Ionization in Atmospheres) is a fast and flexible software package for the 1D photochemical modeling of lower planetary ionospheres of Mars and Venus on the basis of the Mars Climate Database/VenusGRAM neutral atmospheres and SOLAR2000 solar flux. The underlying databases allow the direct modeling of the Mars/Venus ionospheres for the given MaRS and VeRa observational parameters (planetary longitude/latitude, zenith angle, solar activity etc.) and therefore a direct comparison between the observation and the IonA model. This presentation will show a general comparison between the observed and modeled lower ionospheric features: the altitude, electron density and width of the main peak and the electron content from the bottom of the ionosphere up to 250 km altitude.

Peter, K.; Pätzold, M.; Molina-Cuberos, G.; Witasse, O.; Tellmann, S.; Häusler, B.; Bird, M. K.

2013-09-01

33

The Surface of Venus and Implications for its Geological and Geodynamical Evolution: The View Before Venus Express and Outstanding Questions for the Future  

Science.gov (United States)

Prior to the Venera 15/16 and the Magellan missions to Venus, a wide range of ideas existed concerning the nature of the surface of Venus, the geological processes currently operating there, their link to interior processes, the implied geological and geodynamical history of the planet, and how all this compared with the nature and history of other terrestrial planetary bodies. The history of exploration of the surface of Venus represents the acquisition of data with increasing spatial and areal coverage, culminating in the near-global high-resolution image, altimetry, physical property and gravity data obtained by the Magellan mission. Among the most fundamental findings of the global Magellan image data are: 1) that volcanism and tectonism represent the most abundant geological processes operating on the observed surface, 2) that the styles and abundance of volcanism and tectonism combine attributes of both the Earth (e.g., very heavily tectonically deformed regions such as tessera) and the smaller terrestrial planetary bodies (e.g., vast volcanic plains deformed by wrinkle ridges), 3) that the distribution and nature of impact craters precludes active plate tectonics despite many Earth-like tectonic features (e.g., folded mountain belts), 4) that some features (e.g., coronae) are somewhat unique to Venus and may provide important information on mantle convection and lithospheric evolution processes, 5) that the number of impact craters is very small, indicating that the surface geological record is very young, less than 20% of the history of the planet itself, 6) that 80% of the geological record of Venus is no longer obviously preserved in the surface morphology, but may be preserved in the surface rocks, 7) that the distribution and state of preservation of existing impact craters may be consistent with a range of catastrophic resurfacing models, and 8) that the geological record and sequence of events can be correlated with geophysical data to assess crustal thickness variations and mantle convection patterns. The relationships of major elements of global topography and the sequence of events in the observed geological history (as recorded by major geologic units and structures) suggest that much of the current long-wavelength topography of Venus (tessera highlands and lowlands with regional plains) may have formed prior to emplacement of regional plains and been preserved since that time. These observations may favor evolutionary geodynamic models that are characterized by changes in geological style and rates, and may involve non-linear heat loss mechanisms that could have profound influence on the atmosphere. Although the observed surface of Venus dates from relatively recent planetary history, comparative planetology permits inferences to be made about the major stages in the earlier history of Venus. The evolution of the understanding of the surface from early speculations to present observations and interpretations provides an important context for: 1) establishing the relationships of the surface of Venus to the nature of the atmosphere and its evolution as assessed by Venus Express, 2) the comparison of the geological features and history of Venus relative to the Moon, Mars, Mercury and the Earth, and 3) defining the major outstanding problems and questions to be addressed by future experiments and missions to Venus.

Head, J. W.; Ivanov, M. A.; Basilevsky, A. T.

2008-12-01

34

Ionospheric inversion of the Venus Express radio occultation data observed by Shanghai 25 m and New Norcia 35 m antennas  

CERN Document Server

Electron density profiles of the Venus' ionosphere are inverted from the Venus Express (VEX) one-way open-loop radio occultation experiments carried out by Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile (from 110 km to 400 km) retrieved from the X-band egress observation at Shanghai station, shows a single peak near 147 km with a peak density of about $2 \\times 10^4 \\rm{cm}^{-3}$ at a solar zenith angle of 94$^{\\circ}$. As a comparison, the VEX radio science (VeRa) observations at New Norcia station were also examined, including S-, X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, w...

Zhang, Su-jun; Li, Jin-ling; Ping, Jin-song; Chen, Cong-yan; Zhang, Ke-fei

2015-01-01

35

The Scientific Exploration of Venus  

Science.gov (United States)

Part I. Views of Venus, from the Beginning to the Present Day: 1. The dawn of Venus exploration; 2. Mariner and Venera; 3. Pioneer Venus and Vega: orbiters, balloons and multi-probes; 4. Images of the surface; 5. The forgotten world; 6. Earth-based astronomy delivers a breakthrough; 7. Can't stop now; 8. Europe and Japan join in: Venus Express and Akatsuki; Part II. The Motivation to Continue the Quest: 9. Origin and evolution: the solid planet; 10. Atmosphere and ocean; 11. A volcanic world; 12. The mysterious clouds; 13. Superwinds and polar vortices; 14. The climate on Venus, past, present and future; 15. Could there be life on Venus?; Part III. Plans and Visions for the Future: 16. Solar system exploration; 17. Coming soon to a planet near you: planned Venus missions; 18. Towards the horizon: advanced technology; 19. Beyond the horizon: human expeditions; Epilogue; Appendix A. Chronology of space missions to Venus; Appendix B. Data about Venus.

Taylor, Fredric W.

2014-12-01

36

The first results from the ASPERA-4 instrument of Venus Express  

Science.gov (United States)

The Venus Express mission carries the instrument ASPERA-4 Analyzer of Space Plasmas and Energetic Atom to perform for the first time comprehensive plasma measurements at Venus ASPERA-4 is a replica of the instrument ASPERA-3 for the Mars Express mission orbiting Mars for about 2 years The general scientific objective of the ASPERA-4 experiment is to study the solar wind - atmosphere interaction and characterize the plasma atmospheric escape through energetic neutral atom ENA imaging and in-situ ion and electron measurements The ASPERA-4 instrument comprises four sensors two ENA sensors and an electron and ion spectrometer The Neutral Particle Imager NPI provides measurements of the integral ENA flux in the energy range 0 1 - 60 keV with no mass and energy resolution but comparatively high angular resolution 4 6 deg x 11 5 deg The Neutral Particle Detector NPD provides measurements of the ENA flux in the energy range 0 1 - 10 keV resolving velocity and mass H and O with a coarse angular resolution The Electron Spectrometer ELS is a standard top-hat electrostatic analyzer in a very compact design with the high 8 energy resolution to perform photoelectron spectroscopy These three sensors are located on a scanning platform to cover ideally the full sphere Ion Mass Analyzer IMA provides ion measurements in the energy range 0 01 - 30 keV q for the main ion components 1 2 4 16 amu q and the group of molecular ions 20 - 80 amu q The instantaneous field of view is 4 6 deg x 360 deg Electrostatic sweeping performs the elevation 90 deg

Barabash, S.; Sauvaud, J.-A.; Fedorov, A.; Aspera-4

37

Transformative ocean science through the VENUS and NEPTUNE Canada ocean observing systems  

Science.gov (United States)

The health of the world's oceans and their impact on global environmental and climate change make the development of cabled observing systems vital and timely as a data source and archive of unparalleled importance for new discoveries. The VENUS and NEPTUNE Canada observatories are on the forefront of a new generation of ocean science and technology. Funding of over $100M, principally from the Governments of Canada and BC, for these two observatories supports integrated ocean systems science at a regional scale enabled by new developments in powered sub-sea cable technology and in cyber-infrastructure that streams continuous real-time data to Internet-based web platforms. VENUS is a coastal observatory supporting two instrumented arrays in the Saanich Inlet, near Victoria, and in the Strait of Georgia, off Vancouver. NEPTUNE Canada is an 800 km system on the Juan de Fuca Plate off the west coast of British Columbia, which will have five instrumented nodes in operation over the next 18 months. This paper describes the development and management of these two observatories, the principal research themes, and the applications of the research to public policy, economic development, and public education and outreach. Both observatories depend on partnerships with universities, government agencies, private sector companies, and NGOs. International collaboration is central to the development of the research programs, including partnerships with initiatives in the EU, US, Japan, Taiwan and China.

Martin Taylor, S.

2009-04-01

38

The Venus ground-based image Active Archive: a database of amateur observations of Venus in ultraviolet and infrared light  

CERN Document Server

The Venus ground-based image Active Archive is an online database designed to collect ground-based images of Venus in such a way that they are optimally useful for science. The Archive was built to support ESA's Venus Amateur Observing Project, which utilises the capabilities of advanced amateur astronomers to collect filtered images of Venus in ultraviolet, visible and near-infrared light. These images complement the observations of the Venus Express spacecraft, which cannot continuously monitor the northern hemisphere of the planet due to its elliptical orbit with apocentre above the south pole. We present the first set of observations available in the Archive and assess the usability of the dataset for scientific purposes.

Barentsen, Geert

2013-01-01

39

A new view of Earth's sister: Insights following nine years of Venus Express observations  

Science.gov (United States)

Since April 2006 ESA’s Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. The mission delivers comprehensive data on the temperature structure, the atmospheric composition, the cloud morphology, the atmospheric dynamics, the solar wind interaction and the escape processes. Vertical profiles of the atmospheric temperature show strong latitudinal trend in the mesosphere and upper troposphere correlated with changes in the cloud top structure and indicate convective instability in the main cloud deck at 50-60 km. Observations reveal significant latitudinal variations and temporal changes in the global cloud top morphology, which modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from 72 km in the low and middle latitudes to 64 km in the polar region, correlated with decrease of the aerosol scale height from 4±1.6 km to 1.7±2.4 km, marking vast polar depression. UV imaging shows for the first time the middle latitudes and polar regions in unprecedented detail. The eye of the Southern polar vortex was found to be a strongly variable feature with complex dynamics. Solar occultation observations and deep atmosphere spectroscopy in spectral transparency windows mapped the distribution of the major trace gases H _{2}O, SO _{2}, CO, COS and their variations above and below the clouds, revealing key features of the dynamical and chemical processes at work. Tracking motions of cloud features provided the most complete characterization of the mean atmospheric circulation as well as its variability. Low and middle latitudes show an almost constant zonal wind speed at the cloud tops and vertical wind shear of 2-3 m/s/km. The zonal wind speed increased from 84±20 m/s to 110±16 m/s over the course of the mission. Towards the pole, the wind speed drops quickly and the vertical shear vanishes. The meridional poleward wind ranges from 0 at equator to about 15 m/s in the middle latitudes. Comparison of the thermal wind field derived from temperature sounding to the cloud-tracked winds confirms the validity of cyclostrophic balance, at least in the latitude range from 30S to 70S. The observations are supported by development of General Circulation Models. Non-LTE infrared emissions in the lines of O _{2}, NO, CO _{2}, OH originating near the mesopause at 95-105 km were detected and mapped. The data show that the peak intensity occurs in average close to the anti-solar point for O _{2} emission, which is consistent with current models of the thermospheric circulation. For almost complete solar cycle the Venus Express instruments continuously monitoring the induced magnetic field and plasma environment established the global escape rates being 3•10 (24) s (-1) , 7•10 (24) s (-1) , 8•10 (22) s (-1) for O (+) , H (+) , and He (+) ions and identified the main acceleration process. For the first time it was shown that the reconnection process takes place in the tail of a non-magnetized body. It was confirmed that the lightning tentatively detected by PVO indeed occurs on Venus. The thermal mapping of the surface in the near-IR spectral “windows” on the night side indicated the presence of recent volcanism on the planet, as do the high and variable SO _{2} abundances.

Titov, Dmitrij; Svedhem, Håkan; Drossart, Pierre; Taylor, Fredric W.; Zhang, Tielong; Barabash, Stas; Paetzold, Martin; Piccioni, Giuseppe; Markiewicz, Wojciech; Vandaele, Ann C.; Wilson, Colin; Bertaux, Jean-Loup

40

Venus Express: highlights of a four-year survey of our planet-neighbour  

Science.gov (United States)

Since April 2006 Venus Express has been performing a global survey of the remarkably dense, cloudy, and dynamic atmosphere of our near neighbour. A consistent picture of the climate on Venus is emerging on the basis of the new data, which enables us to provide an overview of the global temperature structure, the composition and its variations, the cloud morphology at various levels, the atmospheric dynamics and general circulation, and near-infrared emissions from trace species such as oxygen in the mesosphere. Vertical profiles of atmospheric tempera-ture in the mesosphere and upper troposphere show strong variability correlated with changes in the cloud top structure and many fine details indicating dynamical processes. Temperature sounding also shows that the cloud deck at 50-60 km is convectively unstable, in agreement with the analysis of UV images. Imaging also reveals strong latitudinal variations and significant temporal changes in the global cloud top morphology, which will inevitably modulate the solar energy deposited in the atmosphere. The cloud top altitude varies from ˜72 km in the low and middle latitudes to ˜64 km in the polar region, marking vast polar depressions that form as a result of the Hadley-type meridional circulation. Stellar and solar occultation measurements have revealed an extended upper haze of submicron particles and provided information on its optical properties. Solar occultation observations and deep atmosphere spectroscopy in several spectral transparency windows have quantified the distribution of the major trace gases H2O, SO2, CO, COS and their variations above and below the clouds, and so provided important input and validation for models of chemical cycles and dynamical transport. Cloud motion monitoring has characterised the mean state of the atmospheric circulation as well as its vari-ability. Low and middle latitudes show an almost constant zonal wind speed of 100+/-20 m/s at the cloud tops and vertical wind sheer of 2-3 m/s/km. Towards the pole, the wind speed drops quickly and the vertical shear vanishes. The meridional poleward wind ranges from 0 to about 15 m/s and there is some indication that it may change its direction at high latitudes. Comparison of the thermal wind field derived from temperature sounding to the cloud tracked winds confirms the approximate validity of cyclostrophic balance, at least in the latitude range from 30 S to 70S. Non-LTE infrared emissions in the lines of O2, NO, CO2, OH originating near the mesopause at 95-105 km altitude were detected and mapped. The data show that the peak intensity occurs close to the anti-solar point, which is consistent with current models of the thermospheric circulation.

Titov, Dmitri; Svedhem, Håkan; Barabash, S.; Bertaux, J.-L.; Drossart, P.; Haeusler, B.; Korablev, O. I.; Markiewicz, W. J.; Paetzold, M.; Piccioni, G.; Taylor, F. W.; Vandaele, A.-C.; Zhang, T.

 
 
 
 
41

Scientists are from Mars, educators are from Venus: Relationships in the ecosystem of science teacher preparation  

Science.gov (United States)

Great problems exist in science teaching from kindergarten through the college level (NRC, 1996; NSF, 1996). The problem may be attributed to the failure of teachers to integrate their own understanding of science content with appropriate pedagogy (Shulman, 1986, 1987). All teachers were trained by college faculty and therefore some of the blame for these problems rests on those faculty. This dissertation presents three models for describing secondary science teacher preparation. Two Programs, Two Cultures adapts C. P. Snow's classic work (1959) to describe the work of a science teacher candidate as that of an individual who navigates between two discrete programs: one in college science and the second in teacher education. The second model, Scientists Are from Mars, Educators Are from Venus adapts the popular work of John Gray to describe the system of science teacher education as hobbled by the dysfunctional relationships among the major players and describes the teacher as progeny from this relationship. The third model, The Ecosystem of Science Teacher Preparation reveals some of the deeper complexities of science teacher education and posits that the traditional college science approach treats students as a monoculture when great diversity in fact exists. The three models are described in the context of a large Midwestern university's teacher education program as that program is construed for future biology teachers. Four undergraduate courses typically taken by future biology teachers were observed and described: an introductory biology course; an introductory teacher education course; an upper division course in biochemistry and a senior level science teaching methods course. Seven second semester seniors who were biological Science majors were interviewed. All seven students had taken all of the courses observed. An organization of scientists and educators working together to improve science teaching from kindergarten through graduate school is also described in a case study. The three models described in the dissertation build upon one another and the third model, that of the ecosystem is recognized as both the most accurate portrayal and most complex and therefore most difficult to apply. The system of science teacher preparation is in many ways a system under stress and that stress will result in system evolution. Through better understanding Complex Adaptive Systems and applying that understanding to the system of science teacher education, individuals may be able to influence the nature of system evolution.

Duggan-Haas, Don Andrew

2000-10-01

42

Atmospheric waves on Venus as seen by the Venus Express Radio Science Experiment VeRa  

Science.gov (United States)

Next to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves and turbulence play a significant role in the development and maintenance of atmospheric super rotation.

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-09-01

43

Towards Understanding the Climate of Venus Applications of Terrestrial Models to Our Sister Planet  

CERN Document Server

ESA’s Venus Express Mission has monitored Venus since April 2006, and scientists worldwide have used mathematical models to investigate its atmosphere and model its circulation. This book summarizes recent work to explore and understand the climate of the planet through a research program under the auspices of the International Space Science Institute (ISSI) in Bern, Switzerland. Some of the unique elements that are discussed are the anomalies with Venus’ surface temperature (the huge greenhouse effect causes the surface to rise to 460°C, without which would plummet as low as -40°C), its unusual lack of solar radiation (despite being closer to the Sun, Venus receives less solar radiation than Earth due to its dense cloud cover reflecting 76% back) and the juxtaposition of its atmosphere and planetary rotation (wind speeds can climb up to 200 m/s, much faster than Venus’ sidereal day of 243 Earth-days).

Bonnet, Roger-Maurice; Grinspoon, David; Koumoutsaris, Symeon; Lebonnois, Sebastien; Titov, Dmitri

2013-01-01

44

Venus Atmospheric Maneuverable Platform (VAMP)  

Science.gov (United States)

We have explored a possible new approach to Venus upper atmosphere exploration by applying recent Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (temperature, control, and entry into level flight 3. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance (aerodynamics, power required vs. power available, propulsion, speed, percent buoyancy), performance sensitivity to payload weight 4. Science payload accommodation, constraints, and opportunities We will discuss interdependencies of the above factors and the manner in which the VAMP strawman's characteristics affect the CONOPs and the science objectives. We will show how the these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals 2 and 3. We will also discuss how the VAMP platform itself can facilitate some of these science measurements.

Griffin, K.; Sokol, D.; Lee, G.; Dailey, D.; Polidan, R.

2013-12-01

45

Venus within ESA probe reach  

Science.gov (United States)

Venus Express mission controllers at the ESA Space Operations Centre (ESOC) in Darmstadt, Germany are making intensive preparations for orbit insertion. This comprises a series of telecommands, engine burns and manoeuvres designed to slow the spacecraft down from a velocity of 29000 km per hour relative to Venus, just before the first burn, to an entry velocity some 15% slower, allowing the probe to be captured into orbit around the planet. The spacecraft will have to ignite its main engine for 50 minutes in order to achieve deceleration and place itself into a highly elliptical orbit around the planet. Most of its 570 kg of onboard propellant will be used for this manoeuvre. The spacecraft’s solar arrays will be positioned so as to reduce the possibility of excessive mechanical load during engine ignition. Over the subsequent days, a series of additional burns will be done to lower the orbit apocentre and to control the pericentre. The aim is to end up in a 24-hour orbit around Venus early in May. The Venus orbit injection operations can be followed live at ESA establishments, with ESOC acting as focal point of interest (see attached programme). In all establishments, ESA specialists will be on hand for interviews. ESA TV will cover this event live from ESOC in Darmstadt. The live transmission will be carried free-to-air. For broadcasters, complete details of the various satellite feeds are listed at http://television.esa.int. The event will be covered on the web at venus.esa.int. The website will feature regular updates, including video coverage of the press conference and podcast from the control room at ESA’s Operations Centre. Media representatives wishing to follow the event at one of the ESA establishments listed below are requested to fill in the attached registration form and fax it back to the place of their choice. For further information, please contact: ESA Media Relations Division Tel : +33(0)1.53.69.7155 Fax: +33(0)1.53.69.7690 Venus Express Orbit Insertion - Tuesday 11 April 2006 ESA/ESOC, Robert Bosch Strasse, 5 - Darmstadt (Germany) PROGRAMME 07:30 - Doors open 08:45 - Start of local event, welcome addresses 09:10 - ESA TV live from Mission Control Room (MCR) starts 09:17 - Engine burn sequence starts 09:45 - Occultation of spacecraft by Venus starts 09:55 - Occultation ends 10:07 - Main engine burn ends 10:20 - Address by Jean-Jacques Dordain, ESA’s Director General, and other officials Break and buffet Interview opportunities 11:30-12:15 - Press Conference Jean-Jacques Dordain, Director General, ESA Prof. David Southwood, Director of Science, ESA Gaele Winters, Director of Operations and Infrastructure, ESA Manfred Warhaut, Flight Operations Director, ESA Håkan Svedhem, Venus Express Project Scientist, ESA Don McCoy, Venus Express Project Manager, ESA 13:15 - End of event at ESOC ACCREDITATION REQUEST FORM Venus Express Orbit Insertion - ESA/ESOC Darmstadt - 11 April 2006 First name:___________________ Surname:_____________________ Media:______________________________________________________ Address: ___________________________________________________ ____________________________________________________________ Tel:_______________________ Fax: ___________________________ Mobile :___________________ E-mail: ________________________ I will be attending the Venus Express Orbit Insertion event at the following site: [ ] Germany Location: ESA/ESOC Address: Robert Bosch Strasse 5, Darmstadt, Germany Opening hours: 07:30 - 13:00 Contact: Jocelyne Landeau-Constantin, Tel: +49.6151.902.696 - Fax: +49.6151.902.961 [ ] France Location: ESA HQ Address: 8/10, rue Mario Nikis - Paris 15, France Opening hours: 08:00 - 13:00 Contact: Anne-Marie Remondin - Tel: +33(0)1.53.69.7155 - fax: +33(0)1.53.69.7690 [ ] The Netherlands Location: Newton Room, ESA/ESTEC Address: Keplerlaan 1, Noordwijk, The Netherlands Opening hours: 08:30 - 12:30 Contact: Michel van Baal, tel. + 31 71 565 3006, fax + 31 71 565 5728 [ ] Italy Location: ESA/ESRIN Address: Via Galileo Galilei, Frascati (Rome), Italy Opening hours: 07:00 - 14:

2006-03-01

46

Lower atmosphere minor gas abundances as retrieved from Venus Express VIRTIS-M-IR data at 2.3 ?m  

Science.gov (United States)

Minor gas abundances in the lower atmosphere of Venus' southern hemisphere are investigated using spectroscopic nightside measurements recorded by the Visible and InfraRed Thermal Imaging Spectrometer aboard ESA's Venus Express mission in the moderate spectral resolution infrared mapping channel (VIRTIS-M-IR, 1-5 ?m, FWHM=17 nm). The entire usable data archive is utilized including only radiation spectra sampled at long detector exposure times (?3.3 s) during eight Venus solar days between April 2006 and October 2008. Combined radiative transfer and retrieval techniques (Haus et al., 2013; Haus et al., 2014) are applied for a simultaneous determination of total cloud opacity and H2O, CO, and OCS abundances from the 2.3 ?m atmospheric transparency window that sounds the altitude range between about 30 and 45 km. A wavelength-dependent CO2 opacity correction is considered. Zonal averages of CO abundances at 35 km increase by about 35% from (22.9±0.8) ppmv at equatorial latitudes to (31.0±2.1) ppmv at 65 °S and then decrease to (29.4±2.4) ppmv at 80 °S The±figures refer to the statistical variability of retrieved abundances. In accordance with earlier results, the observed latitudinal variation of tropospheric CO is consistent with a Hadley cell-like circulation. Dawn side CO abundances at high latitudes are slightly smaller than dusk side values by about 7%. The latitudinal distribution of OCS at 35 km is anticorrelated with that of CO, ranging from about (1.15±0.2) ppmv at 65 °S to (1.60±0.2) ppmv at low latitudes (poleward decrease of 28%). Zonal averages of H2O abundances near 35 km slightly decrease toward the South Pole by about 10%, and the hemispheric average is (32.0±1.3) ppmv. A significant local time dependence of OCS and H2O is not observed. Detailed analyses of individual spectrum retrieval errors for different atmospheric models reveal that CO abundance results are reliable (error 4-7%), while H2O and OCS results have lower confidence (errors 30-47% and 41-86%, respectively). SO2 abundances cannot reliably be retrieved from VIRTIS-M-IR spectra.

Haus, Rainer; Kappel, David; Arnold, Gabriele

2015-01-01

47

Venus Atmospheric Maneuverable Platform (VAMP)  

Science.gov (United States)

Over the past years we have explored a possible new approach to Venus upper atmosphere exploration by applying recent Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (vehicle capable of carrying science payloads to explore the Venus upper atmosphere. VAMP targets the global Venus atmosphere between 55 and 70 km altitude and would be a platform to address VEXAG goals I.A, I.B, and I.C. We will discuss the overall mission architecture and concept of operations from launch through Venus arrival, orbit, entry, and atmospheric science operations. We will present a strawman concept of VAMP, including ballistic coefficient, planform area, percent buoyancy, inflation gas, wing span, vehicle mass, power supply, propulsion, materials considerations, structural elements, subsystems, and packaging. The interaction between the VAMP vehicle and the supporting orbiter will also be discussed. In this context, we will specifically focus upon four key factors impacting the design and performance of VAMP: 1. Science payload accommodation, constraints, and opportunities 2. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance, performance sensitivity to payload weight 3. Feasibility of and options for the deployment of the vehicle in space 4. Entry into the Venus atmosphere, including descent profile, heat rate, total heat load, stagnation temperature, control, and entry into level flight We will discuss interdependencies of the above factors and the manner in which the VAMP strawman's characteristics affect the CONOPs and the science objectives. We will show how the these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals I.A, I.B, and I.C.. We will also discuss how the VAMP platform itself can facilitate some of these science measurements.

Polidan, R.; Lee, G.; Sokol, D.; Griffin, K.; Bolisay, L.; Barnes, N.

2014-04-01

48

Ice On Venus  

Science.gov (United States)

This resource is part of the Science Education Gateway (SEGway) project, funded by NASA, which is a national consortium of scientists, museums, and educators working together to bring the latest science to students, teachers, and the general public. Is there ice on Venus? If so, what kind of ice is it? In this activity, students find the answers to these questions by using internet resources. The teacher's page contains teaching strategies, vocabulary, homework ideas, and assessment possibilities.

49

Sampling the Cloudtop Region on Venus  

Science.gov (United States)

The details of the cloud structure on Venus continue to be elusive. One of the main questions is the nature and identity of the ultraviolet absorber(s). Remote sensing observations from Venus Express have provided much more information about the ubiquitous cloud cover on Venus from both reflected and emitted radiation from Venus Monitoring Camera (VMC) and Visible InfraRed Imaging Spectrometer (VIRTIS) observations. Previously, only the Pioneer Venus Large Probe has measured the size distribution of the cloud particles, and other probes have measured the bulk optical properties of the cloud cover. However, the direct sampling of the clouds has been possible only below about 62 km, whereas the recent Venus Express observations indicate that the cloud tops extend from about 75 km in equatorial region to about 67 km in polar regions. To sample the cloud top region of Venus, other platforms are required. An unmanned aerial vehicle (UAV) has been proposed previously (Landis et al., 2002). Another that is being looked into, is a semi-buoyant aerial vehicle that can be powered using solar cells and equipped with instruments to not only sample the cloud particles, but also to make key atmospheric measurements - e.g. atmospheric composition including isotopic abundances of noble and other gases, winds and turbulence, deposition of solar and infrared radiation, electrical activity. The conceptual design of such a vehicle can carry a much more massive payload than any other platform, and can be controlled to sample different altitudes and day and night hemispheres. Thus, detailed observations of the surface using a miniature Synthetic Aperture Radar are possible. Data relay to Earth will need an orbiter, preferably in a low inclination orbit, depending on the latitude region selected for emphasis. Since the vehicle has a large surface area, thermal loads on entry are low, enabling deployment without the use of an aeroshell. Flight characteristics of such a vehicle have been studied (Alam et al., 2014; Kumar et al., 2014) Acknowledgements Mr. Ashish Kumar and Mr. Mofeez Alam were supported by the Indo US Forum for Science and Technology (IUSSTF) as S.N. Bose Scholars at the University of Wisconsin, Madison as Summer interns. We are grateful for the guidance support provided by Dr. Kristen Griffin and Dr. Daniel Sokol, Northrop Grumman Aerospace Corporation. References Alam, M., K. Ashish, and S.S. Limaye. Aerodynamic Analysis of BlimPlane- a Conceptual Hybrid UAV for Venus Exploration. Accepted for publication, 2014 IEEE Aerospace Conference, Big Sky, Montana, 1-8 March 2014. Ashish, K., M. Alam, and S.S. Limaye, Flight Analysis of a Venus Atmospheric Mobile Platform. Accepted for publication, 2014 IEEE Aerospace Conference, Big Sky, Montana, 1-8 March 2014. Landis, G.A., A. Colozza, C.M. LaMarre, Atmospheric flight on Venus. NASA/TM—2002-211467, AIAA-2001-0819, June 2002

Limaye, Sanjay; Ashish, Kumar; Alam, Mofeez; Landis, Geoffrey; Widemann, Thomas; Kremic, Tibor

2014-05-01

50

Chemical reactions between Venus' surface and atmosphere - An update. (Invited)  

Science.gov (United States)

The surface of Venus, at ~740K, is hot enough to allow relatively rapid chemical reactions between it and the atmosphere, i.e. weathering. Venus chemical weathering has been explored in detail [1], to the limits of available data. New data from Venus Express (VEx) and new ideas from exoplanets have sparked a modest renewal of interest in Venus weathering. Venus' surface cannot be observed in visible light, but there are several NIR ';windows' through its atmosphere that allow surface imaging. The VIRTIS spectrometer on VEx viewed the surface through one window [2]; emissivity variations among lava flows on Imdr and Themis Regios have been explained as varying degrees of weathering, and thus age [3]. The VMC camera on VEx also provides images through a NIR window, which suggest variable degrees of weathering on some basaltic plains [4]. Indirect evidence for weathering may come from varying SO2 abundance at Venus' cloud tops; repeated rapid increases and gradual declines may represent volcanic eruptions followed by weathering to form sulfate minerals [5]. Continued geochemical modeling relevant to Venus weathering is motivated by expolanet studies [6]. Models have been extended to hypothetical exo-Venuses of different temperatures and surface compositions [7]. The idea that Venus' atmosphere composition can be buffered by reaction with its surface was explored in detail, and the derived constraint extended to other types of planets [8]. Several laboratories are investigating Venus weathering, motivated in part by the hope that they can provide real constraints on timescales of Venus volcanism [3]. Aveline et al. [9] are extending early studies [10] by reacting rocks and minerals with concentrated SO2 (to accelerate reaction rates to allow detectability of products). Kohler et al. [11] are investigating the stability of metals and chalcogenides as possible causes of the low-emissivity surfaces at high elevations. Berger and Aigouy [12] studied rock alteration on a hypothetical early Venus with a water-rich atmosphere. Martin et al. [13] investigated the fate of weathered rock when heated (by igneous or impact events). Our understanding of Venus' geological history is stymied by a lack of data - spacecraft observations of and/or at its surface. VMC on VEx may continue to provide new data on surface emissivity, but their interpretation is inherently ambiguous. Laboratory experiments seem the most promising approach - attempting to quantify rates of weathering and thus volcanism [3], and (with luck) framing significant problems that can be directly answered by spacecraft observations. [1] Fegley B.Jr. et al. (1997) In Venus II. U. Ariz. Press. p. 591. [2] Helbert J. et al. (2008) GRL 35, L11201. [3] Smrekar S.E et al. (2010) Science 328, 605-608. [4] Basilevsky A.T. et al. (2012) Icarus 217, 434-450. [5] Marcq E. et al. (2013) Nature Geoscience 6, 25-28. [6] Kane S.R. et al. (2013) Astrophysical J. 770, L20. [7] Schaefer L. & Fegley B.Jr. (2011) Astrophysical J. 729, 6. [8] Treiman A.H. & Bullock M.A. (2012) Icarus 217, 534-541. [9] Aveline D.C. et al. (2011) Lunar Planet. Sci. Conf. 42, Abstr. #2165. [10] Fegley B.Jr. & Prinn R.G. (1989) Nature 337, 55-58. [11] Kohler E. et al. (2012) Lunar Planet. Sci. Conf. 43, Abstr. #2749. [12] Berger G. & Aigouy T. (2011) Lunar Planet. Sci. Conf. 42, Abstr. #1660. [13] Martin A.M. et al. (2012) Earth Planet. Sci. Lett. 331-332, 291-304.

Treiman, A. H.

2013-12-01

51

Dynamics and chemistry of Venus' large and complex cloud system : a science case for an in-situ long-term chemical laboratory  

Science.gov (United States)

The planet Venus is the closest to the planet Earth both geographically and geometrically, with an average solar distance only 0.3AU smaller than that of Earth and an equatorial radius that is only 5% smaller than Earth's. But the similarities appear to end there. How did the environments of Venus and Earth become so divergent? The answer to this question relies upon an understanding of Venus' origins, the nature of its present atmosphere, and the role that the clouds have played in evolution and current state of Venus. Venus' clouds are composed of highly concentrated solutions of sulfuric acid and water. The sulfuric acid is produced photochemically from reactions involving water vapor and various sulfur species such as SO2 in the upper atmosphere around 62 km. The region from 50-60 km altitude is convectively unstable, suggesting that most of the cloud formation here is convectively driven, as are cumulus clouds on Earth but with sulfuric acid taking the place of water as the main condensable species. The clouds of Venus are ubiquitous, play a significant role in the radiative balance of the planet, are used as tracers to probe the atmospheric circulation, and are a key part of a global sulfurohydrological cycle that redistributes key greenhouse gasses such as SO2 and H2O. Thus understanding the clouds of Venus holds the key to understanding how Venus itself came to be the world of extremes that it is today. ESA's Venus Express mission, launched in Nov. 2005, has significantly improved our knowledge about the atmosphere of Venus by providing global long-term remote sensing observations with complete coverage in latitude and local solar time. However major questions remain about key minor species and how they vary throughout the major atmospheric regimes in the upper atmosphere, near the cloud tops where photolysis and condensation processes occur, near the surface where coupling and interchange with the atmosphere occurs, and in the middle atmosphere where they combine through meso-scale convection. In situ sampling of these aerosols represents a key measurement for constraining their properties, and identifying their role in the sulfurohydrological cycle by means of microphysical models of steadily increasing complexity. A probe/lander making a single descent will lack the spatial, temporal and local time coverage to address the coupling of compositional variations with radiative and dynamical properties of the atmosphere at cloud level, requiring a long duration flight. Establishing a long-term chemical laboratory in the cloud layer which would measure the detailed composition of both gas and liquid phases, and their latitudinal, diurnal and vertical variability using a combination of mass spectrometry, gas chromatography, tunable laser transmission spectrometry, and polar nephelometry would significantly address all of these objectives. It would allow the determination of the size distribution, shape, and real and imaginary refractive indices of the cloud particles, and the measurement of intensity and polarization phase functions. Our target species would include those known to be associated with cloud formation (e.g. H2SO4, SO3, SO2, H2O), as well as species important in stratospheric chemistry (e.g. CO, ClCOx, Ox, HCl, HF) and surface-atmosphere buffering (e.g. CO, OCS, SOx, Ox, H2S).

Widemann, Thomas; Määttänen, Anni; Wilquet, Valérie; McGouldrick, Kevin; Jessup, Kandis Lea; Wilson, Colin; Limaye, Sanjay; EuroVenus Consortium, the

2014-05-01

52

Venus Atmosphere and Surface Explorer  

Science.gov (United States)

ContextVenus is Earth’s twin planet, but it is an evil twin! To understand how Venus went wrong, to understand the terrestrial planets in our Solar System, those around other stars, and the future of the Earth… we must understand Venus history, evolution and current processes. This requires entering the Venus atmosphere and examining its surface. Future missions will land on Venus, but they need better characterization of its atmosphere and of possible landing sites. VASE can build on discoveries from previous missions, on technical advances in the last decades and on improved balloon technology. The hybrid mission links together a single vertical profile with two weeks of temporal and longitudinal data on a global scale. We can investigate the linked surface and atmosphere processes. We will measure the noble gases which retain indicators of Venus formation; clouds, winds, and chemistry that drive the current Venus processes; and take descent images that extend the Magellan RADAR results to sub-1m resolution, providing ground truth for Magellan’s global mapping and to characterize possible future landing sites.Science Objectives VASE will measure the complete inventory of atmospheric noble gas and light stable isotopes to constrain theories of planetary formation and evolution. It will take nested surface images on descent. It will provide the first complete atmospheric structure profile from clouds to surface of temperature, pressure and wind. VASE will measure with critical accuracy the trace and reactive gas composition profile from clouds to surface. VASE will map the surface emissivity along the surface below two balloon circumnavigations of Venus.Mission VASE is a hybrid Venus mission consisting of a large balloon and a small probe. It reaches Venus after a 4 month trip from Earth. The probe deploys from the entry vehicle and falls to surface in 1.5 hours. The balloon mission lasts 2 weeks, flying in the clouds at 55 km and circumnavigating Venus twice. The balloon communicates directly to Earth and serves as the telecom relay for the probe.

Esposito, Larry W.; Hall, Jeff; Schofield, Tim

2014-11-01

53

Venus mapping  

Science.gov (United States)

Semicontrolled image mosaics of Venus, based on Magellan data, are being compiled at 1:50,000,000, 1:10,000,000, 1:5,000,000, and 1:1,000,000 scales to support the Magellan Radar Investigator (RADIG) team. The mosaics are semicontrolled in the sense that data gaps were not filled and significant cosmetic inconsistencies exist. Contours are based on preliminary radar altimetry data that is subjected to revision and improvement. Final maps to support geologic mapping and other scientific investigations, to be compiled as the dataset becomes complete, will be sponsored by the Planetary Geology and Geophysics Program and/or the Venus Data Analysis Program. All maps, both semicontrolled and final, will be published as I-maps by the United States Geological Survey. All of the mapping is based on existing knowledge of the spacecraft orbit; photogrammetric triangulation, a traditional basis for geodetic control on planets where framing cameras were used, is not feasible with the radar images of Venus, although an eventual shift of coordinate system to a revised spin-axis location is anticipated. This is expected to be small enough that it will affect only large-scale maps.

Batson, R. M.; Morgan, H. F.; Sucharski, Robert

1991-01-01

54

Hot Flow Anomalies at Venus  

Science.gov (United States)

We present a multi-instrument study of a hot flow anomaly (HFA) observed by the Venus Express spacecraft in the Venusian foreshock, on 22 March 2008, incorporating both Venus Express Magnetometer and Analyzer of Space Plasmas and Energetic Atoms (ASPERA) plasma observations. Centered on an interplanetary magnetic field discontinuity with inward convective motional electric fields on both sides, with a decreased core field strength, ion observations consistent with a flow deflection, and bounded by compressive heated edges, the properties of this event are consistent with those of HFAs observed at other planets within the solar system.

Collinson, G. A.; Sibeck, David Gary; Boardsen, Scott A.; Moore, Tom; Barabash, S.; Masters, A.; Shane, N.; Slavin, J.A.; Coates, A.J.; Zhang, T. L.; Sarantos, M.

2012-01-01

55

Robotic Technology for Exploration of Venus  

Science.gov (United States)

Venus, the "greenhouse planet", is a scientifically fascinating place. A huge number of important scientific questions remain to be answered. Venus is sometimes called Earth's "sister planet" due to the fact that it is closest to the Earth in distance and similar to Earth in size. Despite its similarity to Earth, however, the climate of Venus is vastly different from Earth's. Understanding the atmosphere, climate, geology, and history of Venus could shed considerable light on our understanding of our own home planet. The surface of Venus is a hostile environment, with an atmosperic pressure of over 90 bar of carbon dioxide, temperature of 450 C, and shrouded in sulphuric-acid clouds. Venus has been explored by a number of missions from Earth, including the Russian Venera missions which landed probes on the surface, the American Pioneer missions which flew both orbiters and atmospheric probes to Venus, the Russian "Vega" mission, which floated balloons in the atmosphere of Venus, and most recently the American Magellan mission which mapped the surface by radar imaging. While these missions have answered basic questions about Venus, telling us the surface temperature and pressure, the elevations and topography of the continents, and the composition of the atmosphere and clouds, scientific mysteries still abound. Venus is of considerable interest to terrestrial atmospheric science, since of all the planets in the solar system, it is the closest analogue to the Earth in terms of atmosphere. Yet Venus' atmosphere is an example of "runaway greenhouse effect." Understanding the history and the dynamics of Venus' atmosphere could tell us considerable insight about the workings of the atmosphere of the Earth. It also has some interest to astrobiology-- could life have existed on Venus in an earlier, pre-greenhouse-effect phase? Could life still be possible in the temperate middle-atmosphere of Venus? The geology of Venus also has interest in the study of Earth. surface robot will require new technologies; specifically, it will require electronics, scientific instruments, power supplies, and mechanical linkages designed to operate at a temperature above 450 C-hot enough to melt the solder on a standard electronic circuit board. This will require devices made from advanced semiconductor materials, such as silicon carbide, or even new approaches, such as micro-vacuum tube electronics. Such materials are now being developed in the laboratory.

Landis, Geoffrey A.

2003-01-01

56

Pioneer Venus Orbiter Ultraviolet Spectrometer: Operations and Data Analysis  

Science.gov (United States)

The Pioneer Venus spacecraft orbited Venus 5,055 times between 4th December 1978 and 6th October 1992, before entering Venus' atmosphere and burning up on the latter date. On 255 of these orbits, science operations were suspended because of superior conjunction (Venus' proximity to the Sun as seen from Earth). Of the remaining 4800 orbits, about 85% yielded good-quality OUVS science data; 15% were lost to various problems, including loss of uplink (commands) to and downlink (data) from the spacecraft, errors in commanding OUVS, and one or other of the two instrument anomalies mentioned below.

Stewart, A. I. F.

1997-01-01

57

Updating the Venus International Reference Atmosphere (VIRA)  

Science.gov (United States)

The compilation of the Venus International Reference Atmosphere was completed in 1985 through the initiative of A.J. Kliore, V.I. Moroz, and G.M. Keating. Consisting of seven chapters, it presented a synthesis of the best available data at that time on the neutral atmosphere and ionosphere of Venus.This model consist of seven chapters: (1 ) Models of the structure of the atmosphere of Venus from the surface to 100 km altitude,(2) Circulation of the atmosphere from surface to 100 km, (3) Particulate matter in the Venus atmosphere, (4) Models of Venus neutral upper atmosphere: structure and composition, (5) Composition of the atmosphere below 100 km altitude, (6) Solar and thermal radiation in the Venus atmosphere, and (7) The Venus ionosphere. VIRA provides tables and figures as well as description of how the models were synthesized from the available data and references. VIRA has helped many studies of Venus since its publication and in fact has proved invaluable in comparing and contrasting many studies by providing a common standard for atmospheric data.The organizers of VIRA had anticipated updating the model soon after publication as newer data were becoming available from Pioneer and Venera missions.Since then many other missions have yielded valuable data and newer findings. In particular the Venus Express mission is currently providing many new details of the atmospheric structure and radiation balance from its instruments, so an effort to update VIRA is timely. The Venus community continues to consider new missions to address the unanswered questions about Venus and hence updating the Reference Model in the near future will help both future studies and understanding the available observations through models that need the information. The Venus Exploration Analysis Group (VEXAG) sponsored by NASA provides an international forum to carry out the required effort and invites Venus scientists to propose models and participate in working group to update the model. The EGU meeting provides an opportunity to plan the update by considering gaps in the models, examine defects, review newer data and a proposed schedule for the final adoption. VEXAG meetings and other meetings of opportunity such as COSPAR, EPSC/DPS and others may be useful occasions for splinter meetings for the working groups.

Limaye, S.; Svedhem, H.; Titov, D.; Markiewicz, W.; Wilson, C.; Zasova, L.

2012-04-01

58

Studying Venus' atmosphere and ionosphere with Planetary Radio Interferometry and Doppler Experiment (PRIDE)  

Science.gov (United States)

The Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a technique that can provide a multi-disciplinary enhancement of the science return of planetary missions. By performing precise Doppler tracking of a spacecraft carrier radio signal, at Earth-based radio telescopes, and VLBI-style processing of these signals in phase-referencing mode, the technique allows the determination of the radial velocity and lateral coordinates of the spacecraft with very high accuracy[1]. Because of the accurate examination of the changes in phase and amplitude of the radio signal propagating from the spacecraft to the multiple stations on Earth, the PRIDE technique can be used for several fields of planetary research. The application of this technique for atmospheric studies has been assessed by observing ESA's Venus Express (VEX) during Venus occultation events in 2012 and 2014, and by participating in one of the Venus Express Atmospheric Drag Experiment (VExADE) campaigns in 2012. Both studies are contributing to the characterization efforts of the atmosphere and ionosphere of Venus. During the Venus Express Atmospheric Drag Experiment (VExADE) campaigns VEX's orbit pericenter was lowered into an altitude range of approximately 165 to 175 km in order to probe Venus upper atmosphere above its north pole. The first VExADE campaigns were carried out between 2009-2010 using Doppler tracking data acquired by the VEX radio science experiment (VeRa), which provided the first in situ measurements of the density of Venus' polar thermosphere at solar minimum conditions [2]. In the December 2012 campaign the PRIDE-team participated by tracking VEX with several radio telescopes from the European VLBI Network (EVN) during pericenter passage. A Doppler frequency drop of 40 mHz was detected as VEX reached the lowest altitudes at around 170 km. The tracking data for each pericenter pass is fitted for precise orbit determination, from which drag acceleration estimates and the corresponding atmospheric mass density estimates are derived. Next to that, the PRIDE-team was involved in the tracking of VEX during ingress and egress occultation events. During two sessions of radio occultation experiments in April 2012 and March 2014, VEX was tracked with several telescopes from the European VLBI Network (EVN) at X-band. From these experiments, radio occultation profiles of neutral density and electron density of the dayside upper atmosphere and ionosphere of Venus were obtained from ingress and egress occultation tracking. These activities serve as demonstration of the applicability of the PRIDE technique for radio occultation studies, and provides a benchmark against the traditional Doppler tracking, for the same purposes.

Bocanegra-Bahamon, T. M.; Cimo, G.; Duev, D. A.; Gurvits, L. I.; Marty, J. Ch.; Pogrebenko, S. V.; Rosenblatt, P.

2014-04-01

59

Mirror mode structures near Venus and Comet P/Halley  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we study where mirror mode structures are generated near unmagnetized solar system bodies (Venus and comet P/Halley measured in situ by Venus Express and Giotto). To estimate the location of the mirror mode source region at Venus, we apply a turbulent diffusion model of mirror mode structures, which has already been successfully tested in planetary magnetosheaths (Earth, Jupiter, Saturn). It enables us to estimate the distance between the measured location of ...

Schmid, D.; Volwerk, M.; Plaschke, F.; Vo?ro?s, Z.; Zhang, T. L.; Baumjohann, W.; Narita, Y.

2014-01-01

60

Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements  

Science.gov (United States)

We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from 106 km was characterised using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCATter (EISCAT) radar system. Simultaneously, the global structure and evolution of these features was characterised by the Heliospheric Imagers (HI) on the Solar TERrestrial RElations Observatory (STEREO) spacecraft, placing the IPS observations in context. Of particular interest was the observation of one transient in the slow wind, apparently being swept up and entrained by a Stream Interaction Region (SIR). The SIR itself was later detected in-situ at Venus by the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express (VEX) spacecraft. The availability of such diverse data sources over a range of different time resolutions enables us to develop a global picture of these complex events that would not have been possible if these instruments were used in isolation. We suggest that the range of solar-wind transients discussed here may be the interplanetary counterparts of transient structures previously reported from coronagraph observations and are likely to correspond to transient magnetic structures reported in in-situ measurements in interplanetary space. The results reported here also provide the first indication of heliocentric distances at which transients become entrained.

Dorrian, G. D.; Breen, A. R.; Davies, J. A.; Rouillard, A. P.; Fallows, R. A.; Whittaker, I. C.; Brown, D. S.; Harrison, R. A.; Davis, C. J.; Grande, M.

2010-08-01

 
 
 
 
61

Venus: Mysteries Of The "forgotten Planet"  

Science.gov (United States)

The first phase of Venus spacecraft exploration by the Venera, Pioneer Venus, Vega and Magellan missions and later Galileo and Cassini fly-bys established a basic de- scription of the physical and chemical conditions prevailing in the atmosphere and near-planetary environment. It also expanded considerably our knowledge of VenusS geology and geophysics. At the same time, these studies raised many questions on the physical processes on the planet, most of which remain as of today unsolved. The fundamental mysteries of Venus are related to the global atmospheric circulation, the atmospheric chemical composition and its variations, the surface-atmosphere physical and chemical interactions including volcanism, the physics and chemistry of the cloud layer, the thermal balance and role of trace gases in the greenhouse effect, the origin and evolution of the atmosphere, and the plasma environment and its interaction with the solar wind. Besides, the key issues of the history of Venusian volcanism, the global tectonic structure of Venus, and important characteristics of the planetSs surface are still unresolved. Beyond the specific case of Venus, resolving these issues is of cru- cial importance in a comparative planetology context and notably for understanding the long-term climatic evolution processes on Earth. The above problems can be effi- ciently addressed by an orbiter equipped with a suite of adequate remote sensing and in situ instruments. A combination of spectrometers, spectro-imagers, and imagers covering the UV to thermal IR range, along with other instruments such as a radar and a plasma and neutral atoms analyzer, is able to sound the entire Venus atmosphere from the surface to 200 km, and to address specific questions on the surface. Future in situ investigations by descent probes, balloons, and sample return missions will be required to provide a more detailed insight in the Venus mysteries. For more than 10 years Venus has remained the Sforgotten planetT: none of the worldSs space agencies & cedil; has considered it as a primary target. However, a great number of unsolved funda- mental problems in VenusS physics and availability of observational tools encourages the scientific community to propose missions to the planet. Venus Express in Europe and a set of Discovery missions in USA are being currently considered for inclusion in the programmes of space agencies. The Venus Orbiter mission has been recently approved in Japan.

Titov, D. V.

62

Hypothetical flora and fauna of Venus  

Science.gov (United States)

Hypothetical habitability of some of extrasolar planets is a fundamental question of science. Some of exoplanets possess physical conditions close to those of Venus. Therefore, the planet Venus, with its dense and hot (735 K) oxygen-free atmosphere of CO2, having a high pressure of 9.2 MPa at the surface, can be a natural laboratory for this kind of studies. The only existing data on the planet's surface are still the results obtained by the Soviet VENERA landers in the 1970s and 1980s. The TV experiments of Venera-9 and 10 (October, 1975) and Venera-13 and 14 (March, 1982) delivered 41 panoramas of Venus surface (or their fragments). There have not been any similar missions to Venus in the subsequent 39 and 32 years. In the absence of new landing missions to Venus, the VENERA panoramas have been re-processed. The results of these missions are studied anew. A dozen of relatively large objects, from a decimeter to half a meter in size, with an unusual morphology have been found which moved very slowly or changed slightly their shape. Their emergence by chance could hardly be explained by noise. Certain unusual findings that have similar structure were found in different areas of the planet. This paper presents the last results obtained of a search for hypothetical flora and fauna of Venus.

Ksanfomality, L. V.

2014-12-01

63

Venus: discoveries and problems  

International Nuclear Information System (INIS)

Modern state of studies on the question of the Venus origin is discussed. It is indicated that calculations of the planet thermal evolution model pointed up the Venus and Earth resemblance not only from the viewpoint of external parameters but also on the subject of their interior. The Venus probably has an iron core (about 7000 km in diameter), a layer with decreased viscosity which approximately begins from the depth of 200 km and a several dozens kilometers thick crust. The unique peculiarity of the Venus atmosphere is the existence of extended rarefied clouds which occupy a vast region of the atmosphere on a height of 48-65 km. The steam content in the Venus atmosphere is by three orders of magnitude less than in the Earth atmosphere; but there is no water on the Venus surface due to very high temperature. But much water may be in a gaseous state deep in the planet at temperatures higher than the critical one (374 deg C). In the originally rarefied Venus atmosphere water had to boil away promoting the development of a heavy ''hotbed'' effect and further growth of surface temperature. The above model of the Venus thermal evolution is one of probable hypotheses

64

Venus - Ishtar gravity anomaly  

Science.gov (United States)

The gravity anomaly associated with Ishtar Terra on Venus is characterized, comparing line-of-sight acceleration profiles derived by differentiating Pioneer Venus Orbiter Doppler residual profiles with an Airy-compensated topographic model. The results are presented in graphs and maps, confirming the preliminary findings of Phillips et al. (1979). The isostatic compensation depth is found to be 150 + or - 30 km.

Sjogren, W. L.; Bills, B. G.; Mottinger, N. A.

1984-01-01

65

Venus Aerobot Multisonde Mission  

Science.gov (United States)

Robotic exploration of Venus presents many challenges because of the thick atmosphere and the high surface temperatures. The Venus Aerobot Multisonde mission concept addresses these challenges by using a robotic balloon or aerobot to deploy a number of short lifetime probes or sondes to acquire images of the surface. A Venus aerobot is not only a good platform for precision deployment of sondes but is very effective at recovering high rate data. This paper describes the Venus Aerobot Multisonde concept and discusses a proposal to NASA's Discovery program using the concept for a Venus Exploration of Volcanoes and Atmosphere (VEVA). The status of the balloon deployment and inflation, balloon envelope, communications, thermal control and sonde deployment technologies are also reviewed.

Cutts, James A.; Kerzhanovich, Viktor; Balaram, J. Bob; Campbell, Bruce; Gershaman, Robert; Greeley, Ronald; Hall, Jeffery L.; Cameron, Jonathan; Klaasen, Kenneth; Hansen, David M.

1999-01-01

66

High Temperature Mechanisms for Venus Exploration  

Science.gov (United States)

Future Venus missions, including New Frontiers Venus In-Situ Explorer and three Flagship Missions - Venus Geophysical Network, Venus Mobile Explorer and Venus Surface Sample Return all focus on searching for evidence of past climate change both on the surface and in the atmospheric composition as well as in the interior dynamics of the planet. In order to achieve these goals and objectives, many key technologies need to be developed for the Venus extreme environment. These key technologies include sample acquisition systems and other high-temperature mechanisms and mobility systems capable of extended operation when directly exposed to the Venus surface or lower atmosphere environment. Honeybee Robotics has developed two types of high temperature motors, the materials and components in both motors were selected based on the requirement to survive temperatures above a minimum of 460° C, at earth atmosphere. The prototype Switched Reluctance Motor (SRM) has been operated non-continuously for over 20 hours at Venus-like conditions (460° C temperature, mostly CO2 gas environment) and it remains functional. A drilling system, actuated by two SRMs was tested in Venus-like conditions, 460° C temperature and mostly CO2 gas environment, for more than 15 hours. The drill successfully completed three tests by drilling into chalk up to 6 inches deep in each test. A first generation Brushless DC (BLDC) Motor and high temperature resolver were also tested and the feasibility of the designs was demonstrated by the extended operation of both devices under Venus-like condition. Further development of the BLDC motor and resolver continues and these devices will, ultimately, be integrated into the development of a high temperature sample acquisition scoop and high temperature joint (awarded SBIR Phase II in October, 2007). Both the SR and BLDC motors will undergo extensive testing at Venus temperature and pressure (TRL6) and are expected to be mission ready before the next New Frontiers AO release. Scalable high temperature motor, resolver and bearing developments allow for creation of long lasting sample acquisition systems, booms, robot arms and even mobility systems that operate outside of an environment-controlled landed platform on the surface of Venus. The SR and BLDC motors are no longer expected to limit the life of Venus surface operations. With the accompanying high temperature bearing and other mechanisms development, surface operations will be limited only by available power. Therefore, the motor and resolver's capability to survive for hours (and potentially longer) in the environment is a major benefit to future Venus science missions and they also allow time for communication ground loops to optimize sample target selection and the possibility for acquiring multiple samples from the surface. The extreme temperature motors, resolver and other high temperature mechanisms therefore revolutionize the exploration of Venus.

Ji, Jerri; Narine, Roop; Kumar, Nishant; Singh, Sase; Gorevan, Steven

67

Understanding divergent evolution of Earth-like planets: The case for a Venus exploration program  

Science.gov (United States)

The planet Venus is our most Earth-like neighbor in size, mass, and solar distance. In spite of these similarities, the Venus surface and atmosphere are characterized by some of the most enigmatic features seen anywhere in the solar system. Here, we propose a Venus exploration program designed to explain the origin and divergent evolution of the interiors, surfaces, and atmospheres of the terrestrial planets in our solar system, and provide greater insight into the conditions that may affect the habitability of terrestrial planets in other solar systems. This program includes: - The Noble Gas and Trace Gas Explorer is the highest priority mission because itsdata are vital to our understanding of the origin of Venus. This Discovery classmission requires a single entry probe that will carry the state-of-the-art instrumentsneeded to complete the noble gas and trace gas inventories between the cloud topsand the surface. - The Global Geological Process Mapping Orbiter is a Discovery class mission. Itwill carry a C- and/or X-band radar designed for stereo or interferometric imaging,to provide global maps of the surface at horizontal resolutions of 25 to 50 metersto identify and characterize the geologic processes that have shaped the Venussurface. - The Atmospheric Composition Orbiter is a Discovery class mission that will carryremote sensing instruments for characterizing clouds and trace gas variationsthroughout the atmosphere. This mission will collect the data needed tocharacterize the radiative, chemical, and dynamical processes that are maintainingthe thermal structure and composition of the present atmosphere. - The Atmospheric Dynamics Explorer is a New Frontiers class mission that willdeploy 12 to 24 long-lived balloons over a range of latitudes and altitudes toidentify the mechanisms responsible for maintaining the atmosphericsuperrotation. - The Surface and Interior Explorer is a New Frontiers class mission that will deploythree or more long-lived landers on the Venus surface. Each lander will carry aseismometer for studies of the interior structure, as well as in situ instruments forcharacterizing the surface mineralogy and elemental composition. This missionrequires significant technology development. - A Sample Return mission will eventually be needed to conduct investigations ofthe Venus surface and atmosphere that cannot be conducted by instruments onremote sensing platforms or on entry probes. This will probably require a largemission and significant technology development. This series of missions will complement and expand on the science objectives of the proposed ESA Venus Express Mission and the ISAS Venus Climate Orbiter.

Crisp, D.

68

Salt tectonics on Venus?  

International Nuclear Information System (INIS)

The discovery of a surprisingly high deuterium/hydrogen ratio on Venus immediately led to the speculation that Venus may have once had a volume of surface water comparable to that of the terrestrial oceans. The authors propose that the evaporation of this putative ocean may have yielded residual salt deposits that formed various terrain features depicted in Venera 15 and 16 radar images. By analogy with models for the total evaporation of the terrestrial oceans, evaporite deposits on Venus should be at least tens to hundreds of meters thick. From photogeologic evidence and in-situ chemical analyses, it appears that the salt plains were later buried by lava flows. On Earth, salt diapirism leads to the formation of salt domes, anticlines, and elongated salt intrusions - features having dimensions of roughly 1 to 100 km. Due to the rapid erosion of salt by water, surface evaporite landforms are only common in dry regions such as the Zagros Mountains of Iran, where salt plugs and glaciers exist. Venus is far drier than Iran; extruded salt should be preserved, although the high surface temperature (4700C) would probably stimulate rapid salt flow. Venus possesses a variety of circular landforms, tens to hundreds of kilometers wide, which could be either megasalt domes or salt intrusions colonizing impact craters. Additionally, arcurate bands seen in the Maxwell area of Venus could be salt intrusions formed in a region of tectonic stress. These large structures may not be salt features; nonetheless, salt features should exist on Venus

69

Gallium Nitride high temperature electronics for Venus 90-day Lander  

Science.gov (United States)

NASA Science exploration Roadmap includes a "Venus Mobile Lander" mission to operate on the surface of Venus for at least 90 days. Venus Mobile Lander will explore Venus surface as either an aerial vehicle or rover for several months. Previous missions to Venus operated for less than 2 hours. Electronics available today is not capable of supporting design of spacecraft avionics, power systems, or science instruments to operate in the Venus surface environment for 90 days. Thus this long duration mission will spawn a technology development program that can support science instrument and spacecraft design to meet mission requirements. Boeing, together with HRL Laboratory, is developing high temperature electronics for the Venus environment (480 Celsius, 90 bars carbon dioxide atmosphere) using the gallium nitride technology. Examples from our recent validation tests in harsh environments illustrate the performance of the electronic components and modules. In addition to the GaN-based semiconductor material, the characteristics, reliability and viability of the electronics is affected by constituent materials (metallization, dielectric layers) and by the packaging (die attach, wire bonding).

Frampton, Robert; Peltz, Leora; Rubin, Seymour

2008-09-01

70

Transits of Venus and Mercury as muses  

Science.gov (United States)

Transits of Venus and Mercury have inspired artistic creation of all kinds. After having been the first to witness a Venusian transit, in 1639, Jeremiah Horrocks expressed his feelings in poetry. Production has subsequently widened to include songs, short stories, novels, novellas, sermons, theatre, film, engravings, paintings, photography, medals, sculpture, stained glass, cartoons, stamps, music, opera, flower arrangements, and food and drink. Transit creations are reviewed, with emphasis on the English- and French-speaking worlds. It is found that transits of Mercury inspire much less creation than those of Venus, despite being much more frequent, and arguably of no less astronomical significance. It is suggested that this is primarily due to the mythological associations of Venus with sex and love, which are more powerful and gripping than Mercury's mythological role as a messenger and protector of traders and thieves. The lesson for those presenting the night sky to the public is that sex sells.

Tobin, William

2013-11-01

71

Plate tectonics on Venus  

Science.gov (United States)

The high surface temperature of Venus implies a permanently buoyant lithosphere and a thick basaltic crust. Terrestrial-style tectonics with deep subduction and crustal recycling is not possible. Overthickened basaltic crust partially melts instead of converting to eclogite. Because mantle magmas do not have convenient access to the surface the Ar-40 abundance in the atmosphere should be low. Venus may provide an analog to Archean tectonics on the earth.

Anderson, D. L.

1981-01-01

72

Chandra Captures Venus In A Whole New Light  

Science.gov (United States)

Scientists have captured the first X-ray view of Venus using NASA's Chandra X-ray Observatory. The observations provide new information about the atmosphere of Venus and open a new window for examining Earth's sister planet. Venus in X-rays looks similar to Venus in visible light, but there are important differences. The optically visible Venus is due to the reflection of sunlight and, for the relative positions of Venus, Earth and Sun during these observations, shows a uniform half-crescent that is brightest toward the middle. The X-ray Venus is slightly less than a half-crescent and brighter on the limbs. The differences are due to the processes by which Venus shines in visible and X-ray light. The X-rays from Venus are produced by fluorescence, rather than reflection. Solar X-rays bombard the atmosphere of Venus, knock electrons out of the inner parts of the atoms, and excite the atoms to a higher energy level. The atoms almost immediately return to their lower energy state with the emission of a fluorescent X-ray. A similar process involving ultraviolet light produces the visible light from fluorescent lamps. For Venus, most of the fluorescent X-rays come from oxygen and carbon atoms between 120 and 140 kilometers (74 to 87 miles) above the planet's surface. In contrast, the optical light is reflected from clouds at a height of 50 to 70 kilometers (31 to 43 miles). As a result, Venus' Sun-lit hemisphere appears surrounded by an almost-transparent luminous shell in X-rays. Venus looks brightest at the limb since more luminous material is there. Venus X-ray/Optical Composite of Venus Credit: Xray: NASA/CXC/MPE/K.Dennerl et al., Optical: Konrad Dennerl "This opens up the exciting possibility of using X-ray observations to study regions of the atmosphere of Venus that are difficult to investigate by other means," said Konrad Dennerl of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, leader of an international team of scientists that conducted the research. The Chandra observation of Venus was also a technological tour de force. The angular separation of Venus from the Sun, as seen from Earth, never exceeds 48 degrees. This relative proximity has prevented star trackers and cameras on other X-ray astronomy satellites from locking onto guide stars and pointing steadily in the direction of Venus to perform such an observation. Venus was observed on Jan. 10, 2001, with the Advanced CCD Imaging Spectrometer (ACIS) detector plus the Low Energy Transmission Grating and on Jan. 13, 2001, with the ACIS alone. Other members of the team were Vadim Burwitz and Jakob Engelhauser, Max Planck Institute; Carey Lisse, University of Maryland, College Park; and Scott Wolk, Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. These results were presented at this week's "New Visions of X-ray universe in the XMM-Newton and Chandra Era" symposium in Noordwijk, Netherlands. The Low Energy Transmission Grating was built by the Space Research Organization of the Netherlands and the Max Planck Institute, and the ACIS instrument was developed for NASA by The Pennsylvania State University, University Park, and the Massachusetts Institute of Technology (MIT), Cambridge. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass.

2001-11-01

73

Sox10-Venus mice: a new tool for real-time labeling of neural crest lineage cells and oligodendrocytes  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background While several mouse strains have recently been developed for tracing neural crest or oligodendrocyte lineages, each strain has inherent limitations. The connection between human SOX10 mutations and neural crest cell pathogenesis led us to focus on the Sox10 gene, which is critical for neural crest development. We generated Sox10-Venus BAC transgenic mice to monitor Sox10 expression in both normal development and in pathological processes. Results Tissue fluorescence distinguished neural crest progeny cells and oligodendrocytes in the Sox10-Venus mouse embryo. Immunohistochemical analysis confirmed that Venus expression was restricted to cells expressing endogenous Sox10. Time-lapse imaging of various tissues in Sox10-Venus mice demonstrated that Venus expression could be visualized at the single-cell level in vivo due to the intense, focused Venus fluorescence. In the adult Sox10-Venus mouse, several types of mature and immature oligodendrocytes along with Schwann cells were clearly labeled with Venus, both before and after spinal cord injury. Conclusions In the newly-developed Sox10-Venus transgenic mouse, Venus fluorescence faithfully mirrors endogenous Sox10 expression and allows for in vivo imaging of live cells at the single-cell level. This Sox10-Venus mouse will thus be a useful tool for studying neural crest cells or oligodendrocytes, both in development and in pathological processes.

Shibata Shinsuke

2010-10-01

74

About the various contributions in Venus rotation rate and LOD  

CERN Document Server

% context heading (optional) {Thanks to the Venus Express Mission, new data on the properties of Venus could be obtained in particular concerning its rotation.} % aims heading (mandatory) {In view of these upcoming results, the purpose of this paper is to determine and compare the major physical processes influencing the rotation of Venus, and more particularly the angular rotation rate.} % methods heading (mandatory) {Applying models already used for the Earth, the effect of the triaxiality of a rigid Venus on its period of rotation are computed. Then the variations of Venus rotation caused by the elasticity, the atmosphere and the core of the planet are evaluated.} % results heading (mandatory) {Although the largest irregularities of the rotation rate of the Earth at short time scales are caused by its atmosphere and elastic deformations, we show that the Venus ones are dominated by the tidal torque exerted by the Sun on its solid body. Indeed, as Venus has a slow rotation, these effects have a large amplit...

Cottereau, L; Lebonnois, S; Souchay, J

2011-01-01

75

Gravity anomalies on Venus  

Science.gov (United States)

Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.

Sjogren, W. L.; Phillips, R. J.; Birkeland, P. W.; Wimberly, R. N.

1980-01-01

76

A Unique Approach for Studying Venus’s Atmosphere: Technology Development for the Venus Atmospheric Maneuverable Platform (VAMP)  

Science.gov (United States)

We are investigating a novel, reduced-risk approach to long-duration upper atmosphere exploration of Venus. The Venus Atmospheric Maneuverable Platform (VAMP) concept is a semi-buoyant plane with a science payload that can perform in situ measurements of Venus’s atmosphere. VAMP is also capable of revisiting scientifically interesting locations. Designed with a low ballistic coefficient, VAMP deploys in space and enters Venus’s atmosphere without an aeroshell. Once in the atmosphere, it can engage in a variety of science campaigns while varying its altitude between 50 and 68 km as it circumnavigates Venus. During daytime, VAMP will be able to make continuous science measurements at a range of latitudes, longitudes, and altitudes, while at night the vehicle will descend to a fully-buoyant, lower-power state, capable of performing modest science measurements at the float altitude. Near the end of VAMP’s mission life, the vehicle may attempt an end-of-life trajectory into higher latitudes or descend to lower altitudes. This presentation focuses on the technology roadmap that will allow the vehicle to accomplish these science measurements. The roadmap is driven by high priority science measurements and the technology needed to implement VAMP’s main mission phases: deployment, entry into Venus’s atmosphere, and the transition to flight and science flight performance. The roadmap includes materials tests, planform aerodynamic characterization, various subscale and full-scale packaging and deployment tests, and a full-scale suborbital flight and is being produced with extensive science community interaction to define the science measurements that would be uniquely possible with this new science platform.

Samuele, Rocco; Lee, Greg; Sokol, Daniel; Polidan, Ron; Griffin, Kristen; Bolisay, Linden; Michi, Yuki; Barnes, Nathan

2014-11-01

77

Variability of the Venus Oxygen Airglow  

Science.gov (United States)

We have obtained spatially resolved near-IR spectroscopic observations of the night-side of Venus through the last three inferior conjunctions using IRIS2 on the Anglo-Australian 3.9m telescope and CASPIR on the 2.3m ANU telescope. The data are used to investigate the extreme variability of the spatial distribution and intensity of the O2 airglow emission feature at 1.27 microns. The airglow emission was very strong in September 2002, and much weaker in July 2004. Substantial night-to-night variations are also seen in both the intensity and spatial distribution of the emission. The emission is typically brightest near the anti-solar point, consistent with an upper atmosphere circulation in the form of a tidal flow from day-side to night-side. However, there are substantial variations from this typical pattern, with plumes of emission sometimes extending over long distances, and reaching regions close to the terminator. The Venus O2 airglow provides a probe of the chemistry and dynamics of the Venus upper atmosphere. These and earlier ground-based observations help to provide context for the more detailed studies that will be possible by the Venus Express spacecraft.

Bailey, Jeremy A.; Meadows, V. S.; Chamberlain, S.; Simpson, A.; Crisp, D.

2006-09-01

78

Systems Analysis for a Venus Aerocapture Mission  

Science.gov (United States)

Previous high level analysis has indicated that significant mass savings may be possible for planetary science missions if aerocapture is employed to place a spacecraft in orbit. In 2001 the In-Space Propulsion program identified aerocapture as one of the top three propulsion technologies for planetary exploration but that higher fidelity analysis was required to verify the favorable results and to determine if any supporting technology gaps exist that would enable or enhance aerocapture missions. A series of three studies has been conducted to assess, from an overall system point of view, the merit of using aerocapture at Titan, Neptune and Venus. These were chosen as representative of a moon with an atmosphere, an outer giant gas planet and an inner planet. The Venus mission, based on desirable science from plans for Solar System Exploration and Principal Investigator proposals, to place a spacecraft in a 300km polar orbit was examined and the details of the study are presented in this paper.

Lockwood, Mary Kae; Starr, Brett R.; Paulson, John W., Jr.; Kontinos, Dean A.; Chen, Y. K.; Laub, Bernard; Olejniczak, Joseph; Wright, Michael J.; Takashima, Naruhisa; Justus, Carl G.

2006-01-01

79

From CERN to VENUS Express  

CERN Multimedia

Participants in the 'Schweizer Jugendforscht' projects at CERN under the supervision of Günther Dissertori, professor at the Swiss Federal Institute of Technology (ETH Zürich) and other members of ETH Zürich, Werner Lustermann and Michael Dittmar. In Switzerland, as in many other countries, this year has seen a long list of activities, celebrating the centenary of Einstein's 'Annus mirabilis'. Having formerly employed Einstein, the Swiss Federal Institute of Intellectual Property in Bern made its contribution by sponsoring a special 'study week' for young high-school students, under the tutorship of 'Schweizer Jugendforscht', an organisation which supports the scientific activities of very talented young people. The organisers chose 'Mission to Jupiter's Moon, Europa' as the general theme for this study week. From 2 to 8 October 2005 several groups of students (between 16 and 19 years old) had to investigate some mission-related questions, ranging from the choice of the orbit and different ways of explor...

2005-01-01

80

The Pioneer Venus program  

Science.gov (United States)

The major aspects of the Pioneer Venus orbiter and multiprobe missions are documented. Specific topics covered include a program history, the scientific payloads, spacecraft descriptions, launch and interplanetary cruise features, encounter features, nominal mission descriptions, instrument anomalies, and the orbiter extended mission. The key scientific questions addressed by the missions are listed.

Colin, L.

1980-01-01

 
 
 
 
81

Mercury and Venus  

Science.gov (United States)

Students explore Mercury and Venus, the first and second planets nearest the Sun. They learn about the planets' characteristics, including their differences from Earth. Students also learn how engineers are involved in the study of planets by designing equipment and spacecraft to go where it is too dangerous for humans.

Integrated Teaching And Learning Program

82

Plains Tectonics on Venus  

Science.gov (United States)

Tectonic deformation in the plains of Venus is pervasive, with virtually every area of the planet showing evidence for faulting or fracturing. This deformation can be classified into three general categories, defined by the intensity and areal extent of the surface deformation: distributed deformation, concentrated deformation, and local fracture patterns.

Banerdt, W. B.; McGill, G. E.; Zuber, M. T.

1996-01-01

83

Storms On Venus: Lightning-induced Chemistry And Predicted Products  

Science.gov (United States)

Observations by many spacecraft that have visited Venus over the last 40 years appear to confirm the presence of lightning storms in the Venus atmosphere. Recent observations by Venus Express indicate that lightning frequency and power is similar to that on Earth. While storms are occurring, energy deposition by lightning into Venus atmospheric constituents will immediately dissociate molecules into atoms, ions and plasma from the high temperatures in the lightning column (>30,000 K) and the associated shock waves and heating, after which these atom and ion fragments will recombine during cooldown to form new sets of molecules. Lightning will re-sort the atoms of C,O,S,N,H to create highly energetic new products. Spark and discharge experiments in the literature suggest that lightning effects on the main atmospheric molecules CO2, N2, SO2, H2SO4 and H2O will yield new molecules such as mixed carbon oxides (CnOm), mixed sulfur oxides (SnOm), oxygen (O2), elemental sulfur (Sn), nitrogen oxides (NO, N2O, NO2, NO3), sulfuric acid clusters (HnSmOx-.aHnSmOx e.g. HSO4-.mH2SO4), polysulfur oxides, carbon soot, and also halogen oxides from HCl or HF and other exotic species. Many of these molecular species may be detectable by instruments onboard Venus Express. We explore the diversity of new products likely created in the storm clouds on Venus.

Delitsky, M. L.; Baines, K. H.

2012-10-01

84

Transit Observations of Venus's Atmosphere in 2012 from Terrestrial and Space Telescopes as Exoplanet Analogs  

Science.gov (United States)

We extensively observed the 8 June 2012 transit of Venus from several sites on Earth; we provide this interim status report about this and about two subsequent ToVs observed from space. From Haleakala Obs., we observed the entire June transit over almost 7 h with a coronagraph of the Venus Twilight Experiment B filter) and with a RED Epic camera to compare with simultaneous data from ESA's Venus Express, to study the Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry at 1.6 µm from the aureole and during the disk crossing that compare well with carbon dioxide spectral models; from Sac Peak/IBIS we have high-resolution imaging of the Cytherean aureole for 22 min, starting even before 1st contact; from Big Bear, we have high-resolution imaging of Venus's atmosphere and the black-drop effect through 2nd contact; and we had 8 other coronagraphs around the world. For the Sept 21 ToV as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds as a reflecting surface to search for an 0.01% diminution in light and a differential drop that would result from Venus's atmosphere by observing in both IR/UV, for which we have 170 HST exposures. As of this writing, preliminary data reduction indicates that variations in Jovian clouds and the two periods of Jupiter's rotation will be too great to allow extraction of the transit signal. For the December 20 ToV as seen from Saturn, we had 22 hours of observing time with VIMS on Cassini, for which we are looking for a signal of the 10-hr transit in total solar irradiance and of Venus's atmosphere in IR as an exoplanet-transit analog. Our Maui & Sac Peak expedition was sponsored by National Geographic Society's Committee for Research and Exploration; HST data reduction by NASA: HST-GO-13067. Some of the funds for the carbon dioxide filter for Sac Peak provided by NASA through AAS's Small Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur Astronomers; Rob Lucas, Aram Friedman, Eric Pilger, Stan Truitt, and Steve Bisque/Software Bisque for Haleakala support/operations; Vasyl Yurchyshyn and Joseph Gangestad '06 of The Aerospace Corp. at Big Bear Solar Obs; LMSAL and Hinode science/operations team.

Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann, T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.; Dantowitz, R.

2013-06-01

85

Cosmic Art: Artistic Expressions of the Universe in Science  

Science.gov (United States)

Students in some of the science classes at Columbia College Chicago are encouraged to use their artistic talents to express their fascination with, understanding of, or sense of mystery about the cosmos. These creative expressions have numerous educational benefits that reinforce the learning process. Furthermore, this type of assignment often improves the students' attitude towards science, instilling in them a life-long interest for learning. These projects also break down barriers between the disciplines, particularly those of science and art. In this paper, I describe the pedagogy and benefits of the art/science partnership in my science classes with examples of student artworks that depict cosmic phenomena.

Papacosta, P.

2013-04-01

86

On the Frequency of Potential Venus Analogs from Kepler Data  

Science.gov (United States)

The field of exoplanetary science has seen a dramatic improvement in sensitivity to terrestrial planets over recent years. Such discoveries have been a key feature of results from the Kepler mission which utilizes the transit method to determine the size of the planet. These discoveries have resulted in a corresponding interest in the topic of the Habitable Zone and the search for potential Earth analogs. Within the solar system, there is a clear dichotomy between Venus and Earth in terms of atmospheric evolution, likely the result of the large difference (approximately a factor of two) in incident flux from the Sun. Since Venus is 95% of the Earth's radius in size, it is impossible to distinguish between these two planets based only on size. In this Letter we discuss planetary insolation in the context of atmospheric erosion and runaway greenhouse limits for planets similar to Venus. We define a "Venus Zone" in which the planet is more likely to be a Venus analog rather than an Earth analog. We identify 43 potential Venus analogs with an occurrence rate (??) of 0.32^{+0.05}_{-0.07} and 0.45^{+0.06}_{-0.09} for M dwarfs and GK dwarfs, respectively.

Kane, Stephen R.; Kopparapu, Ravi Kumar; Domagal-Goldman, Shawn D.

2014-10-01

87

Computer science reconsidered the invocation model of process expression  

CERN Document Server

The Invocation Model of Process Expression argues that mathematics does not provide the most appropriate conceptual foundations for computer science, but, rather, that these foundations are a primary source of unnecessary complexity and confusion.  It supports that there is a more appropriate conceptual model that unifies forms of expression considered quite disparate and simplifies issues considered complex and intractable.  This book presents that this model of process expression is alternative theory of computer science that is both valid and practical.

Fant, Karl M

2007-01-01

88

Digital workstation for Venus topographic mapping  

Science.gov (United States)

A digital workstation was developed and is currently at the U.S. Geological Survey (USGS) in Flagstaff, Arizona to be used for Venus topographic mapping. The system is based on a mapping and geocoding image correlation (GIS MAGIC) system developed by Science Applications International Corporation (SAIC) for the creation of precisely geocoded imagery data bases for both optical and synthetic aperture radar (SAR) imagery. A multitude of data from various sources has been processed, including conventional aerial photographs, airborne and orbital SAR, and Spot. This paper covers the GIS MAGIC development history, hardware/software features and capabilities. Also covered are the types of modifications required to accommodate Venus radar data and results which can be achieved using the GIS MAGIC System.

Poehler, Paul; Haag, Nils N.; Maupin, Jerry A.; Howington-Kraus, Annie E.; Wu, Sherman S.

1993-10-01

89

Perspectives of the bistatic radar and occultation studying of the Venus atmosphere and surface  

Science.gov (United States)

Studying the physical properties of Venus surface and subsurface structures is an important direction in the space research. The first aim of this contribution is to present some results of reanalysis of the bistatic radar and occultation experiments provided using Venera-9, 10 and 15, 16 satellites. Comparison is made with Magellan and Venus Express bistatic radar missions. Bistatic radio images of the Venus surface is compared with monostatic radio images obtained by the Soviet and USA orbiters. The second aim consists in introducing new methods for investigation of the layered structure of the Venus atmosphere and measuring parameters of Venus surface and subsurface structures using the bistatic radar technology. The first bistatic radar measurements with spatial resolution ~ 10-20 km have been carried out during autumn of 1975 year in the five Venus equatorial regions using the Venera-9 and 10 satellites. Small roughness and, in general, plain character of relief in the investigated regions have been revealed. In 1983, the satellites Venera 15 and 16 have carried out new bistatic radar experiments with spatial resolution in the interval 5 - 10 km. New information on the large-scale topography and roughness of small-scale relief has been obtained in Northern polar areas of the planet. Some features have been detected. 1. The significant variations of the reflectivity ~ 2-4 times were found in the first region. The second area of reflectivity magnitude was far below (by three - four times) the previously measured values in the equatorial regions of Venus. These significant reflectivity variations may be related to changes in the conductivity of the ground. 2. Extremely small values roughness with rms of slopes ~ 0.20 were recorded in the northern area. 3. Both the bending angle and the reflection coefficient were determined in the experiment from the measured frequency difference between the direct and the reflected signals as a function of time, using the orbital data. New methods developed by analysis of the experimental data obtained using high-stability radio fields of the Earth's navigational satellites are introduced. For investigations of the layered structures of the Venus atmosphere a new eikonal acceleration/intensity technique is proposed. This technique allows: (1) one frequency high-precision measuring the total absorption of radio waves in the atmosphere; (2) estimating vertical gradients of the refractivity, and determining the height, slope, and horizontal displacement of the atmospheric and ionospheric layers; (3) a criterion is introduced for identification of the internal waves in the Venus atmosphere. To obtain the information on the planetary subsurface structure up to depth 1 km it is necessary to use radio waves in the Low Frequency (LF), Medium Frequency (MF), or High Frequency (HF) bands with wavelength from 1 m up 300 m. The depth of radio sounding is proportional to the wavelength, the intensity of the radio-emission source, and depends on the conductivity of the ground. The bistatic subsurface remote sensing of the planet can be achieved using powerful Earth based transmitters, and/or sporadic radio emission of the Sun and other space radio sources. The work was partly supported by Program 22 of Presidium of Russian Academy of Sciences.

Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Yakovlev, Oleg

2013-04-01

90

The various contributions in Venus rotation rate and LOD  

Science.gov (United States)

Context. Thanks to the Venus Express Mission, new data on the properties of Venus could be obtained, in particular concerning its rotation. Aims: In view of these upcoming results, the purpose of this paper is to determine and compare the major physical processes influencing the rotation of Venus and, more particularly, the angular rotation rate. Methods: Applying models already used for Earth, the effect of the triaxiality of a rigid Venus on its period of rotation are computed. Then the variations of Venus rotation caused by the elasticity, the atmosphere, and the core of the planet are evaluated. Results: Although the largest irregularities in the rotation rate of the Earth on short time scales are caused by its atmosphere and elastic deformations, we show that the irregularities for Venus are dominated by the tidal torque exerted by the Sun on its solid body. Indeed, as Venus has a slow rotation, these effects have a large amplitude of two minutes of time (mn). These variations in the rotation rate are greater than the one induced by atmospheric wind variations that can reach 25-50 s of time (s), depending on the simulation used. The variations due to the core effects that vary with its size between 3 and 20 s are smaller. Compared to these effects, the influence of the elastic deformation caused by the zonal tidal potential is negligible. Conclusions: As the variations in the rotation of Venus reported here are close to 3 mn peak to peak, they should influence past, present, and future observations, thereby providing further constraints on the planet's internal structure and atmosphere.

Cottereau, L.; Rambaux, N.; Lebonnois, S.; Souchay, J.

2011-07-01

91

Venus gravity fields  

Science.gov (United States)

Results of Pioneer Venus Orbiter observations concerning the gravity field of Venus are presented. The gravitational data was obtained from reductions of Doppler radio tracking data for the Orbiter, which is in a highly eccentric orbit with periapsis altitude varying from 145 to 180 km and nearly fixed periapsis latitude of 15 deg N. The global gravity field was obtained through the simultaneous estimation of the orbit state parameters and gravity coefficients from long-period variations in orbital element rates. The global field has been described with sixth degree and order spherical harmonic coefficients, which are capable of resolving the three major topographical features on Venus. Local anomalies have been mapped using line-of-sight accelerations derived from the Doppler residuals between 40 deg N and 10 deg S latitude at approximately 300 km spatial resolution. Gravitational data is observed to correspond to topographical data obtained by radar altimeter, with most of the gravitational anomalies about 20-30 milligals. Simulations evaluating the isostatic states of two topographic features indicate that at least partial isostasy prevails, with the possibility of complete compensation.

Sjogren, W. L.; Ananda, M.; Williams, B. G.; Birkeland, P. W.; Esposito, P. S.; Wimberly, R. N.; Ritke, S. J.

1981-01-01

92

The VENUS detector at TRISTAN  

International Nuclear Information System (INIS)

The design of the VENUS detector is described. In this paper, emphasis is placed on the central tracking chamber and the electromagnetic shower calorimeters. Referring to computer simulations and test measurements with prototypes, the expected performance of our detector system is discussed. The contents are, for the most part, taken from the VENUS proposal /2/. (author)

93

Spectral analysis of the solar wind turbulence in the vicinity of Venus  

Science.gov (United States)

In this study we analyze magnetic field data provided by Venus Express (VEX) between 2007 and 2008. During each of the probe's eccentric polar orbit around Venus, VEX performs plasma and magnetic field measurements in the environment around the planet both in Venus induced magnetosphere and in the solar wind at several tens of thousands of kilometers away from the magnetosphere. This latter data set has a unique scientific value as it provides observations of magnetic turbulence in the solar wind around 0.72 AU, in the vicinity of Venus. We discuss a semi-automated method to select solar wind magnetic field data at 1 Hz from Venus Express Magnetometer (MAG) data by using plasma data from the Analyser of Space Plasma and Energetic Atoms (ASPERA). The time intervals when VEX is in the solar wind are automatically determined for 2007 and 2008. We apply a Fourier transform on the selected data and calculate the power spectral densities (PSD) of the turbulent magnetic field through Welch's algorithm. We compute the PSD of the three components of the magnetic field for the time intervals when both MAG and ASPERA were operating in the solar wind, for each VEX orbit between 1st of January 2007 and 31st of December 2008. The data base includes a number of 374 individual spectra. We discuss the spectral properties of turbulence and illustrate similarities between fast and slow wind during the minimum phase of the solar cycle for each of VEX's orbit which satisfies the selection criteria for a period of two years. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418. Data analysis was done with the AMDA science analysis system provided by the Centre de Données de la Physique des Plasmas (IRAP, Université Paul Sabatier, Toulouse) supported by CNRS and CNES.

Teodorescu, Eliza; Echim, Marius; Munteanu, Costel; Voitcu, Gabriel; Zhang, Tielong; Barabash, Stanislav; Budnik, Elena; Fedorov, Andrei

2014-05-01

94

Venus-intercepting meteoroid streams  

Science.gov (United States)

This study is motivated by the possibility of determining the large-body meteoroid flux at the orbit of Venus. Towards this end, we attempt to estimate the times at which enhanced meteoric activity might be observed in the planet's atmosphere. While a number of meteoroid streams are identified as satisfying common Earth and Venus intercept conditions, it is not clear from the Earth-observed data if these streams contain large-body meteoroids. A subset of the Taurid Complex objects may produce fireball-rich meteor showers on Venus. A total of 11 short-period, periodic comets and 46 near-Earth asteroids approach the orbit of Venus to within 0.1 au, and these objects may have associated meteoroid streams. Comets 27P/Crommelin and 7P/Pons-Winnecke are identified as candidate parents to possible periodic meteor showers at the orbit of Venus.

Beech, Martin

1998-02-01

95

Solar Wind Driven Plasma Fluxes from the Venus Ionosphere  

Science.gov (United States)

SOLAR WIND DRIVEN PLASMA FLUXES FROM THE VENUS IONOSPHERE H. Pérez-de-Tejada (1), R. Lundin (2), H. Durand-Manterola (1), S. Barabash (2), T. L. Zhang (3), J. A., Sauvaud (4), and M. Reyes-Ruiz (5) 1 - Institute of Geophysics, UNAM, México, D. F. 2 - Swedish Institute of Space Physics, Kiruna, Sweden 3 - Space Research Institute, Graz, Austria 4 - CESR, Toulouse, France 5 - Institute of Astronomy, UNAM, Ensenada, México Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the kinetic pressure of planetary O+ ion fluxes measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. The momentum flux of the O+ ions leads to superalfvenic flow conditions. It is suggested that such O+ ion beams are produced in the vicinity of the magnetic polar regions of the Venus ionosphere where the solar wind erodes the local plasma leading to plasma channels that extend downstream from those regions.

Perez De Tejada, H. A.; Lundin, R. N.; Zhang, T.; Sauvaud, J. A.; Reyes-Ruiz, M.

2012-12-01

96

Venus cloud microphysics  

Science.gov (United States)

Because sulfuric acid does not wet sulfur, composite drops in the atmosphere of Venus cannot have sulfur 'cores', but must instead have sulfur coats. Both components then communicate with the vapor phase. Drops that are fully coated with sulfur are immune to coalescence; this sets a limit to growth that may explain 'Mode 3' particles. The sulfur coating is probably responsible for the anomalously low refractive indices derived from entry-probe nephelometer data. There appears to be about an order of magnitude less elemental sulfur than sulfuric acid in the clouds.

Young, A. T.

1983-01-01

97

Tectonics and evolution of Venus  

Science.gov (United States)

Earlier data synthesized with data recently obtained by the Pioneer Venus Orbiter are analyzed with regard to general tectonics, interior, and long-term evolution of Venus. Comprehensive topographic maps, global properties of Venus, and variations in its gravity field are investigated, and bulk properties of Venus, earth, Mars, the sun, and chondritic meteorites relevant to planetary internal structure and evolution are studied. Although Venus was found to differ less than 30% from earth in comparing all important bulk properties, it appears to have evolved differently. It is noted that a slow rotation rate, the absence of a satellite, the virtual absence of a magnetic field, the dearth of water in the atmosphere, the abundance of primordial argon, and the high surface temperature, are properties in which Venus differs most from the earth. Further results showing the positive correlation of gravity and topography at all wavelengths and the apparent absence of any feature like an ocean indicate that Venus is a one-plate planet and its evolution apparently resembles that of Mars more than that of the earth.

Phillips, R. J.; Kaula, W. M.; Mcgill, G. E.; Malin, M. C.

1981-01-01

98

SurVenTIS - Surface of Venus Thermal Imaging System  

Science.gov (United States)

VIRTIS on Venus Express will provide us with the first global mapping of surface types on Venus (Helbert et al., this meeting). While correction algorithms can reduce cloud induced contrast variations, the scattering in the clouds will always result in blurring. This limits the achievable spatial resolution from orbit to about 50km. A balloon or descent probe which would allow taking a thermal imaging system below the main cloud deck would reduce this problem significantly. The technical limitation of such platforms would not allow carrying any instrument like VIRTIS. Therefore we propose SurVenTIS, a miniaturized instrument specifically designed for studying the surface composition of Venus on spatial scales intermediated between orbital and in-situ data. Depending on the mission profile a surveyor of geological interesting regions can be performed as well as investigations on the local heterogeneity in the surface composition and its link to recent volcanism. In combination with other instrumentation the interaction between surface and atmosphere and especially the question of chemical erosion can be addressed. Finally a search for thermal anomalies indicating volcanic activity can be performed with high spatial resolution. SurVenTIS is a near-IR imager with 6 filters taking advantage of the spectral windows in the atmosphere of Venus. The filters are selected to study albedo variations, oxidation state of the surface and derive compositional information. At least one filter will allow imaging from high altitudes and overlaps with the spectral coverage of VIRTIS on Venus Express. Due to the inherent blurring by cloud and haze particles a 256*256 CCD/CMOS pixel array with FOV of 10°/15° is sufficient and greatly simplifies the design. It is a simplified and miniaturized instrument concept based on proven technology. It benefits from extensive heritage in IR technology and camera development at DLR as well as from the heritage for the data analysis directly derived from VIRTIS on Venus Express.

Helbert, J.; Muller, N.; Michaelis, H.; Breuer, D.

99

On the Frequency of Potential Venus Analogs from Kepler Data  

CERN Document Server

The field of exoplanetary science has seen a dramatic improvement in sensitivity to terrestrial planets over recent years. Such discoveries have been a key feature of results from the {\\it Kepler} mission which utilizes the transit method to determine the size of the planet. These discoveries have resulted in a corresponding interest in the topic of the Habitable Zone (HZ) and the search for potential Earth analogs. Within the Solar System, there is a clear dichotomy between Venus and Earth in terms of atmospheric evolution, likely the result of the large difference ($\\sim$ factor of two) in incident flux from the Sun. Since Venus is 95\\% of the Earth's radius in size, it is impossible to distinguish between these two planets based only on size. In this paper we discuss planetary insolation in the context of atmospheric erosion and runaway greenhouse limits for planets similar to Venus. We define a ``Venus Zone'' (VZ) in which the planet is more likely to be a Venus analog rather than an Earth analog. We iden...

Kane, Stephen R; Domagal-Goldman, Shawn D

2014-01-01

100

The Venus Zone: Seeking the Twin of Earth's Twin  

Science.gov (United States)

The field of exoplanetary science has seen a dramatic improvement in sensitivity to terrestrial planets over recent years. Such discoveries have been a key feature of results from the Kepler mission which utilizes the transit method to determine the size of the planet. These discoveries have resulted in a corresponding interest in the topic of the Habitable Zone (HZ) and the search for potential Earth analogs. Within the Solar System, there is a clear dichotomy between Venus and Earth in terms of atmospheric evolution, likely the result of the large difference in incident flux from the Sun. Since Venus is 95% of the Earth's radius in size, it is impossible to distinguish between these two planets based only on size. In this talk I will discuss planetary insolation in the context of atmospheric erosion and runaway greenhouse limits for planets similar to Venus. Using the ``Venus Zone'' (VZ), I will present identified potential Venus analogs from Kepler data and subsequent occurance rates of such planets.

Kane, Stephen R.; Kopparapu, Ravi Kumar; Domagal-Goldman, Shawn

2015-01-01

 
 
 
 
101

Astronomical Heritages: Astronomical Archives and Historic Transits of Venus  

Science.gov (United States)

These Proceedings contain a selection of presentations and research papers emanating from meetings of the Astronomical Archives and Transits of Venus Working Groups of Commission 41, and from presentations at the last three IAU General Assemblies. Some additional reports related to the topic of this book have also been added. The first part of the book deals with archives, the second part with facts related to historical transits of Venus - although there is substantial overlap since some archive papers deal with Transits of Venus as well. The compilation deals with many wonderful and even rare sources of information, such as official documents and reports, private letters, astronomical instruments and telescopes, national inventories, photographic plates, etc. A lot of documentation described in this book is available only on national level, and the combination of this material in one single volume looks like a cross-cultural study dealing with art and science, and almost can serve as a travel guide in time and space.

Sterken, C.; Duerbeck, H. W.

2005-03-01

102

The 2010 European Venus Explorer (EVE) mission proposal  

Science.gov (United States)

The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an `M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (˜25°C and ˜0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond.

Wilson, Colin Frank; Chassefière, Eric; Hinglais, Emmanuel; Baines, Kevin H.; Balint, Tibor S.; Berthelier, Jean-Jacques; Blamont, Jacques; Durry, Georges; Ferencz, Csaba S.; Grimm, Robert E.; Imamura, Takeshi; Josset, Jean-Luc; Leblanc, François; Lebonnois, Sebastien; Leitner, Johannes J.; Limaye, Sanjay S.; Marty, Bernard; Palomba, Ernesto; Pogrebenko, Sergei V.; Rafkin, Scot C. R.; Talboys, Dean L.; Wieler, Rainer; Zasova, Liudmila V.; Szopa, Cyrill

2012-04-01

103

Stagnation Point Radiative Heating Relations for Venus Entry  

Science.gov (United States)

Improved analytic expressions for calculating the stagnation point radiative heating during entry into the atmosphere of Venus have been developed. These analytic expressions can be incorporated into entry trajectory simulation codes. Together with analytical expressions for convective heating at the stagnation point, the time-integrated total heat load at the stagnation point is used in determining the thickness of protective material required, and hence the mass of the fore body heatshield of uniform thickness.

Tauber, Michael E.; Palmer, Grant E.; Prabhu, Dinesh K.

2012-01-01

104

HST Observations of Mars and Venus Supra-thermal Thermospheric Oxygen  

Science.gov (United States)

The loss of water from Venus and Mars is an ongoing topic of study in planetary astronomy. One method for considering this loss is to examine the loss of volatiles, specifically hydrogen and oxygen, from the thermospheres of the two planets. One process by which oxygen atoms escape the Mars atmosphere is by a creation of a suprathermal population of oxygen from the dissociative recombination of O2+, the dominant ion in the Mars and Venus ionospheres. On Venus, the same process occurs, but due to the larger planetary mass the suprathermal corona has not been observed as an escape mechanism by itself. Observations of hot oxygen in the Venus atmosphere date back as far as 1978 (Bertaux et al.), though observational confirmation of the hot population of Mars was only published as recently as 2011 (Feldman et al.) Re-analysis of the understanding of the Venus thermosphere has been performed after Venus Express results seemed to contrast to the Pioneer Venus observations (Lichtenegger et al., 2009). The observations presented in this work were taken of Mars using HST STIS and a low-resolution grating in 2007 and of Venus using HST STIS and an echelle grating in November 2013. The UV spectroscopic observations of resonantly-scattered sunlight from the 1304 Å oxygen emission are compared with modeled thermospheric populations.Comparisons are made with previous data sets and modeled populations, in order to better describe the temporal variation of the suprathermal neutral oxygen populations.

Carveth, Carol; Clarke, John T.; Chaufray, Jean-Yves; Bertaux, Jean-Loup

2014-06-01

105

Recent hotspot volcanism on Venus from VIRTIS emissivity data.  

Science.gov (United States)

The questions of whether Venus is geologically active and how the planet has resurfaced over the past billion years have major implications for interior dynamics and climate change. Nine "hotspots"--areas analogous to Hawaii, with volcanism, broad topographic rises, and large positive gravity anomalies suggesting mantle plumes at depth--have been identified as possibly active. This study used variations in the thermal emissivity of the surface observed by the Visible and Infrared Thermal Imaging Spectrometer on the European Space Agency's Venus Express spacecraft to identify compositional differences in lava flows at three hotspots. The anomalies are interpreted as a lack of surface weathering. We estimate the flows to be younger than 2.5 million years and probably much younger, about 250,000 years or less, indicating that Venus is actively resurfacing. PMID:20378775

Smrekar, Suzanne E; Stofan, Ellen R; Mueller, Nils; Treiman, Allan; Elkins-Tanton, Linda; Helbert, Joern; Piccioni, Giuseppe; Drossart, Pierre

2010-04-30

106

The Venus nighttime green line  

Science.gov (United States)

The oxygen green line [O(1S - 1D)] at 557.7 nm in the Venus nightglow was first observed with the Keck I telescope in November 1999 [Slanger et al., 2001]. Until 2012 numerous attempts to observe it showed either much lower intensities or complete absence of the emission. In July 2012 the green line again appeared, in observations from the Apache Point Observatory, with an intensity similar to that in 1999 [Gray et al., 2014]. The oxygen red lines at 630/636.4 nm are always much weaker than the green line, and only upper limits can be set. The physical phenomenon most closely correlated to the green line appearance is the occurrence of coronal mass ejections (CMEs), so solar particle precipitation is likely to be the main initiating contributor to green line production. If the nighttime source is dissociative recombination of O2+, then the green/red intensity ratio provides some indication of the emission altitude. Gray, C. et al., Icarus (in press), 2014. Slanger et al., Science, 291, 463-465, 2001.

Slanger, Tom; Gray, Candace

107

Interpretation of Venus gravitational anomalies  

International Nuclear Information System (INIS)

The Venus gravity field anomalies are interpreted from three harmonics of potential expansion. Masses and depths of the anomaly centers in three regions: the Aphrodita land, the Ishtar land and in the South of the planet, are defined from the Venus geoid height, pure anomaly of attractive force, and plumb deviation. These depths are determined to be 930-1140 km. Analogous Earth anomalies in the field smoothing from 16 to 3 harmonics are characterized by depth overestimation. 1.4-times. Because of this, depths of the Venus anomaly sources reduced to 16 harmonics lie approximately in the range of 700-800 km, that is they correspond to the depth of bedding of the Venus mantle second phase boundary

108

Venus wind-altitude radar  

Science.gov (United States)

A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.

Levanon, N.

1974-01-01

109

Mantle plumes on Venus revisited  

Science.gov (United States)

The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not examine either the geoid and topography amplitudes separately or the shapes of anomalies.

Kiefer, Walter S.

1992-12-01

110

Clouds and aerosols on Venus: an overview  

Science.gov (United States)

The past decade demonstrated significant progress in understanding of the Venus cloud system. This paper gives a summary of new observations and modelling efforts that will form the basis for a relevant chapter in the Venus III book. Venus Express observations reveal significant latitudinal variations and temporal changes in the global cloud top morphology [1]. The cloud top altitude varies from ~72 km in the low and middle latitudes to ~64 km in the polar region, correlated with decrease of the aerosol scale height from 4 ± 1.6 km to 1.7 ± 2.4 km marking a vast polar depression [2, 3]. UV imaging shows the middle latitudes and polar regions in unprecedented detail. The eye of the Southern polar vortex was found to be a strongly variable feature with complex morphology and dynamics [4]. Solar and stellar occultations give access to a vertical profiling of the light absorption by the aerosols in the upper haze. The aerosol loading in the mesosphere of Venus investigated by SPICAV experiment onboard Venus Express between 2006 and 2010 was highly variable on both short and long time scales. The extinction at a given altitude can vary with a factor of 10 for occultations separated by a few Earth days. The extinction at a given altitude is also significantly lower towards the poles (by a factor 10 at least) compared to the values around the equator, while there is apparently no correlation between the extinction and the latitude in the region comprised between ±40° around the equator [5]. Based on Mie theory and on the observed spectral dependence of light extinction in spectra recorded simultaneously in the UV (SPICAV-UV), in the near IR (SPICAV-IR), and in the short-and midwavelength IR (SPICAV-SOIR), the size distribution of aerosols in the upper haze of Venus was retrieved, assuming H2SO4/water composition of the droplets [6]. The optical model includes H2SO4 concentrations from 60 to 85%. A number of results are strikingly new: (1) an increase of the H2SO4 concentration with a decreasing altitude (from 70-75% at about 90 km to 85% at 70 km of altitude) and (2) Many SOIR/SPICAV data cannot be fitted when using size distributions found in the literature, with an effective radius below 0.3 ?m and a variance of about 2. The scale height of the upper haze is found to be 6.9 ± 5.1 km. The lower & middle cloud layers - those at 48 - 60 km altitudes - are difficult to observe, as they are hidden by upper clouds. Nevertheless, both nightside near-IR sounding and radio occultation has provided valuable insight into cloud processes in this region. Near IR sounding reveals the morphology of the lower/middle clouds 'backlit' by thermally emitted photons from the lower atmosphere. The morphology of these clouds changes on timescales of order of 24 hours [7]. The vertically integrated cloud optical depth is twice as great in the polar collar (at 75 degrees latitude) compared to low latitudes. Spectral band ratio analysis, if interpreted strictly in terms of Mode 1 / 2 / 2' / 3 particles of H2SO4:H2O mixtures, the acidity of the cloud particles is found to be higher near the polar collar and in regions of optically thick cloud [8]. Particles in the centre of the polar vortex exhibit anomalously high band ratios so are significantly larger and/or of different composition than those at low latitudes [9]. Radio occultation from Venus Express confirms that the atmosphere is in convective equilibrium from 50-60 km [10]. Sulphuric acid vapour profiles calculated from the absorption of the radio signals show an atmosphere saturated with sulphuric acid in the cloud layer [11]. Both of these results are consistent with the understanding of convective condensational cloud at altitudes of 50-60 km. Microphysical simulations of the aerosol populations in the atmosphere of Venus have received a boost from the recent exploration of particle properties carried out by various teams using Venus Express over the last decade or so. Numerous groups are applying separate models to the coupled problems of the Venus clouds. Quasi-periodic variabilit

Titov, D. V.; Ignatiev, N. I.; McGouldrick, K.; Wilquet, V.; Wilson, C. F.

2014-04-01

111

Crustal deformation: Earth vs Venus  

International Nuclear Information System (INIS)

It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning

112

Venus: A World of Water and Life  

Science.gov (United States)

Author: John Ditkof Institution: University Wisconsin-Madison Amphiboles that contain the hydroxide ion form only in the presence of water and this fact has become the way for scientists to prove that Venus was once a water world. Though, Tremolite is considered the main mineral to look for, it requires life that is analogous to the ancient life here on Earth for it to form. Dolomite is the main ingredient for the formation of this low grade metamorphic mineral and without it would be very difficult for Tremolite to form, unless there is another process that is unknown to science. Venus is known to have extensive volcanic features (over 1600 confirmed shield volcanoes dot its surface) and with little erosion taking place; a mineral that is associated with volcanism and forms only in the presence of water should be regarded as the main goal. Hornblende can form via volcanism or a metamorphic process but requires water for initial formation. The European Space Agency is currently trying to determine whether or not the continents on Venus' surface are made of granite, as they argue granite requires water for formation. Either way, computer models suggest that any oceans that formed on the surface would have lasted at best 2 billion years, as the surface is estimated to be only 800 million years old, any hornblende that would have formed is more than likely going to be deep underground. To find this mineral, as well as others, it would require a mission that has the ability to drill into the surface, as the easiest place to do this would be on the mountain peaks in the Northern Hemisphere on the Ishtar Terra continent. Through the process of uplift, any remaining hornblende may have been exposed or very near exposed to the surface. Do to the amount of fluorine in the atmosphere and the interaction between this and the lithosphere, the hydroxyl ions may have been replaced with fluorine turning the hornblende into the more stable fluoro-hornblende. To further add to the mystery of Venus is the unusual atmospheric composition. The presence of both sulfur dioxide and hydrogen sulfide demand further research as these gases are not being replenished by any geologic activity. Both of these compounds are found is sufficient quantity in the cloud decks, but are almost nonexistent at the surface, further supporting the idea of a chemical reaction/process in the atmosphere. There are particles that have been detected in the atmosphere that seem to be absorbing UV radiation is also located at these same altitudes. Finding tremolite on Venus would only further excite the possibility that we are not alone in the universe. Could life on Venus be related to life here on Earth? Where in the Solar System did life originate? These are questions that would need serious thought if such an event took place. Finding hornblende on Venus would give further support to several theories, but finding tremolite would change everything.

Ditkof, J. F.

2012-12-01

113

Identification of Postclassic Maya Constellations from the Venus Pages of the Dresden Codex  

Directory of Open Access Journals (Sweden)

Full Text Available Ancient Mayan civilization, flourished from 1200 B.C. to 1500 A.D., has left numerous hieroglyphic texts on astronomical observations and calendar. In particular, the Dresden Codex contains the most details of such ancient Mayan heritage. Page 24 and those from 46 to 50 of the Dresden Codex describe the Mayan Venus calendar along with the augural descriptions. We note that the calendar in Dresden Codex is Venus-solar calendar. Our work focuses on the possibility that the calendar was made to work in conjunction with the periodic appearance of constellations on the sky. By analyzing the descriptions in the Venus pages, we propose that the columns in each page describe the motion of Venus with respect to major constellations at dates corresponding to special events while the calendar dates increase horizontally in the synodic period of Venus. We present twenty Mayan constellations identified from the Venus pages assuming that the first date of page 46 is February 6, 1228. We also report our understanding of verb expressions about the relative movement of constellations and Venus.La civilización maya, que floreció del 1200 a.C. a 1500 d.C., dejó numerosos textos jeroglíficos sobre el calendario y observaciones astronómicos. El Códice de Dresde, en particular, contiene el más detallado de dichos antiguos legados mayas. Las páginas 24 y 46 a 50 de dicho códice describen el calendario de Venus con los augurios correspondientes. Nosotros hemos notado que éste es un calendario Venus-Solar, y nuestro trabajo se enfoca sobre la posibilidad de que estuviera hecho para trabajar en conjunción con la aparición de determinadas constelaciones en el cielo. Es a través del análisis y descripción de las páginas de Venus que proponemos que las columnas en cada página describen el movimiento de Venus respecto de constelaciones mayores, en fechas que corresponden a eventos especiales, mientras que las fechas calendáricas se incrementan horizontalmente dentro del periodo sinódico de Venus. Aquí presentamos veinte constelaciones mayas identificadas desde las páginas de Venus asumiendo que la primera fecha, en la página 46, fue febrero 6 de 1228. También reportamos, como entendemos, las expresiones verbales sobre el movimiento de Venus y las constelaciones.

Changbom Park

2010-01-01

114

Identification of Postclassic Maya Constellations from the Venus Pages of the Dresden Codex  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish La civilización maya, que floreció del 1200 a.C. a 1500 d.C., dejó numerosos textos jeroglíficos sobre el calendario y observaciones astronómicos. El Códice de Dresde, en particular, contiene el más detallado de dichos antiguos legados mayas. Las páginas 24 y 46 a 50 de dicho códice describen el cal [...] endario de Venus con los augurios correspondientes. Nosotros hemos notado que éste es un calendario Venus-Solar, y nuestro trabajo se enfoca sobre la posibilidad de que estuviera hecho para trabajar en conjunción con la aparición de determinadas constelaciones en el cielo. Es a través del análisis y descripción de las páginas de Venus que proponemos que las columnas en cada página describen el movimiento de Venus respecto de constelaciones mayores, en fechas que corresponden a eventos especiales, mientras que las fechas calendáricas se incrementan horizontalmente dentro del periodo sinódico de Venus. Aquí presentamos veinte constelaciones mayas identificadas desde las páginas de Venus asumiendo que la primera fecha, en la página 46, fue febrero 6 de 1228. También reportamos, como entendemos, las expresiones verbales sobre el movimiento de Venus y las constelaciones. Abstract in english Ancient Mayan civilization, flourished from 1200 B.C. to 1500 A.D., has left numerous hieroglyphic texts on astronomical observations and calendar. In particular, the Dresden Codex contains the most details of such ancient Mayan heritage. Page 24 and those from 46 to 50 of the Dresden Codex describe [...] the Mayan Venus calendar along with the augural descriptions. We note that the calendar in Dresden Codex is Venus-solar calendar. Our work focuses on the possibility that the calendar was made to work in conjunction with the periodic appearance of constellations on the sky. By analyzing the descriptions in the Venus pages, we propose that the columns in each page describe the motion of Venus with respect to major constellations at dates corresponding to special events while the calendar dates increase horizontally in the synodic period of Venus. We present twenty Mayan constellations identified from the Venus pages assuming that the first date of page 46 is February 6, 1228. We also report our understanding of verb expressions about the relative movement of constellations and Venus.

Changbom, Park; Heajoo, Chung.

115

A Conceptual Venus Rover Mission Using Advanced Radioisotope Power Systems  

Science.gov (United States)

This concept study demonstrates that a long lived Venus rover mission could be enabled by a novel application of advanced RPS technology. General Purpose Heat Source (GPHS) modules would be employed to drive an advanced thermoacoustic Stirling engine, pulse tube cooler and linear alternator that provides electric power and cooling for the rover. The Thermoacoustic Stirling Heat Engine (TASHE) is a system for converting high-temperature heat into acoustic power which then drives linear alternators and a pulse tube cooler to provide both electric power and coolin6g for the rover. A small design team examined this mission concept focusing on the feasibility of using the TASHE system in this hostile environment. A rover design is described that would provide a mobile platform for science measurements on the Venus surface for 60 days, with the potential of operating well beyond that. A suite of science instruments is described that collects data on atmospheric and surface composition, surface stratigraphy, and subsurface structure. An Earth-Venus-Venus trajectory would be used to deliver the rover to a low entry angle allowing an inflated ballute to provide a low deceleration and low heat descent to the surface. All rover systems would be housed in a pressure vessel in vacuum with the internal temperature maintained by the TASHE at under 50 °C.

Evans, Michael; Shirley, James H.; Abelson, Robert Dean

2006-01-01

116

Hot-spot tectonics of Eistla Regio, Venus: Results from Magellan images and Pioneer Venus gravity  

Science.gov (United States)

Eistla Regio (ER) is a broad, low, discontinuous topographic rise striking roughly EW at low northern latitudes of Venus. Some 2000 x 7000 km in dimensions, it is the third largest rise in planform on Venus after Aphrodite Terra and Beta Phoebe Regiones. These rises are the key physiographic elements in a hot spot model of global tectonics including transient plume behavior. Since ER is the first such rise viewed by Magellan and the latitude is very favorable for Pioneer Venus gravity studies, some of the predictions of a time dependent hot spot model are tested. Western ER is defined as the rise including Gula and Sif Mons and central ER as that including Sappho Patera. Superior conjunction prevented Magellan from returning data on eastern ER (Pavlova) during the first mapping cycle. It is concluded that the western and central portions of ER, while part of the same broad topographic rise and tectonic framework, have distinctly different surface ages and gravity signatures. The western rise, including Gula and Sif Mons, is the expression of deep seated uplift with volcanism limited to the individual large shields. The eastern portion has been widely resurfaced more recently by thermal anomalies in the mantle.

Grimm, Robert E.; Phillips, Roger J.

1991-06-01

117

Hot-spot tectonics of Eistla Regio, Venus: Results from Magellan images and Pioneer Venus gravity  

Science.gov (United States)

Eistla Regio (ER) is a broad, low, discontinuous topographic rise striking roughly EW at low northern latitudes of Venus. Some 2000 x 7000 km in dimensions, it is the third largest rise in planform on Venus after Aphrodite Terra and Beta Phoebe Regiones. These rises are the key physiographic elements in a hot spot model of global tectonics including transient plume behavior. Since ER is the first such rise viewed by Magellan and the latitude is very favorable for Pioneer Venus gravity studies, some of the predictions of a time dependent hot spot model are tested. Western ER is defined as the rise including Gula and Sif Mons and central ER as that including Sappho Patera. Superior conjunction prevented Magellan from returning data on eastern ER (Pavlova) during the first mapping cycle. It is concluded that the western and central portions of ER, while part of the same broad topographic rise and tectonic framework, have distinctly different surface ages and gravity signatures. The western rise, including Gula and Sif Mons, is the expression of deep seated uplift with volcanism limited to the individual large shields. The eastern portion has been widely resurfaced more recently by thermal anomalies in the mantle.

Grimm, Robert E.; Phillips, Roger J.

1991-01-01

118

The 2004 Transit of Venus -- Halley's Method of Deriving the AU  

Science.gov (United States)

This series of three web pages gives information about the usage of the transit of Venus to measure distances in the solar system. The site also contains a large collection of links related to the Venus transit, a math refresher, and a photo archive of the transit. It is part of the extensive web site "From Stargazers to Starships", which uses space exploration and space science to introduce concepts in physics and astronomy. Translations in Spanish and French are available.

Stern, David

2006-07-16

119

The 2012 Transit of Venus for Cytherean Atmospheric Studies and as an Exoplanet Analog  

Science.gov (United States)

We worked to assemble as complete a dataset as possible for the Cytherean atmosphere in collaboration with Venus Express in situ and to provide an analog of spectral and total irradiance exoplanet measurements. From Haleakala, the whole transit was visible in coronal skies; our B images showed the evolution of the visibility of Venus's atmosphere and of the black-drop effect, as part of the Venus Twilight Experiment's 9 coronagraphs distributed worldwide with BVRI. We imaged the Cytherean atmosphere over two minutes before first contact, with subarcsecond resolution, with the coronagraph and a separate refractor. The IBIS imaging spectrometer at Sacramento Peak Observatory at H-alpha and carbon-dioxide also provided us high-resolution imaging. The NST of Big Bear Solar Observatory also provided high-resolution vacuum observations of the Cytherean atmosphere and black drop evolution. Our liaison with UH's Mees Solar Observatory scientists provided magneto-optical imaging at calcium and potassium. Spaceborne observations included the Solar Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope (SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance measurements with ACRIMSAT and SORCE/TIM, to characterize the event as an exoplanet-transit analog. Our expedition was sponsored by the Committee for Research and Exploration/National Geographic Society. Some of the funds for the carbon-dioxide filter for IBIS were provided by NASA through AAS's Small Research Grant Program. We thank Rob Lucas, Aram Friedman, and Eric Pilger '82 for assistance with Haleakala observing, Rob Ratkowski of Haleakala Amateur Astronomers for assistance with equipment and with the site, Stan Truitt for the loan of his Paramount ME, and Steve Bisque/Software Bisque for TheSky X controller. We thank Joseph Gangestad '06 of Aerospace Corp., a veteran of our 2004 expedition, for assistance at Big Bear. We thank the Lockheed Martin Solar and Astrophysics Laboratory and Hinode science and operations teams for planning and support.

Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.; Reardon, K. P.; Widemann, T.; Tanga, P.; Dantowitz, R.; Willson, R.; Kopp, G.; Yurchyshyn, V.; Sterling, A.; Scherrer, P.; Schou, J.; Golub, L.; Reeves, K.

2012-10-01

120

Venus-13, Venus-14: mass-spectrometry of the atmosphere  

International Nuclear Information System (INIS)

Mass spectrometric measurements of the Venus atmosphere composition are carried out using the radio-frequency mass-spectrometer installed on ''Venera-13'' and ''Venera-14'' apparatusus. Isotopic composition of neon (20Ne/22Ne) in Venus atmosphere differs from neon composition in the Earth atmosphere and in solar wind. Measurements carried out using ''Venera-13'' and ''Venera-14'' give magnitudes of nitrogen concentration which are in agreement with known measurements. The total concentration of three argon concentration with mass numbers of 36, 38 and 40 are in good agreement with the data obtained on ''Venera-11'' and ''Venera-12'' satellites. A magnitude of carbon isotopic ratio 13C/12C comes to agreement with a magnitude of isotopic ratio for the Earth atmosphere. Preliminary data on krypton 84, xenon 131, and xenon 132 concentrations in Venus atmosphere are presented

 
 
 
 
121

Episodic plate tectonics on Venus  

Science.gov (United States)

Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

Turcotte, Donald

1992-01-01

122

Results from VENUS  

International Nuclear Information System (INIS)

Recent results from VENUS experiments on e+e- reactions at energies between 52 and 60.8 GeV are presented. The R-values, the ratio of the total hadronic cross section to that of ? pair production, look slightly high within the present energy region. To understand this observation, a detailed study was carried out on the production of a heavy quark with |Q|=e/3. By using a next-to-leading log. approximation, the QCD cut-off parameter, ?MS, was obtained as being ?MS=208 MeV(+80MeV, -62MeV). The differential cross sections for e+e- ? e+e-, ??, ?+?-, and ?+?- were found to be consistent with predictions of the standard model. The average charge asymmetry for e+e- ? qq-bar was also measured and found to be consistent with the prediction of the standard model. No evidence was observed indicating new particle production. No single photon production was observed and the upper limit of the number of light neutrino types was set to be N? < 17.8 (90 % CL). (author)

123

Lada Terra: A 'new' hotspot on Venus  

Science.gov (United States)

On Earth, areas called 'hotspots' form above mantle plumes and are defined by their topographic swells, volcanism, and large positive gravity anomalies. Hawaii is a classic example. Venus has ~10 such highland regions that are analogous to terrestrial hotspots and are approximately 2000 km in diameter. Modeling of their gravity and topography provides evidence for compensation beneath the thermal lithosphere, which is interpreted to indicate the presence of a hot mantle plume. Analysis of data from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS, see Drossart et al. 2007) on the Venus Express mission reveals surface thermal emissivity anomalies in the southern hemisphere that are interpreted as compositional variations (Helbert et al., 2008; Mueller et al., 2008). Most high emissivity anomalies occur in regions previously interpreted as hotspots: Imdr, Themis, and Dione Regiones. The evidence for plumes at depth, the correlation of high emissivity anomalies to stratigraphically young volcanic flows, and analysis of the likely emissivity of weathered and unweathered basalt on Venus lead Smrekar et al. (2010) to interpret the high emissivity flows as evidence of geologically recent, relatively unweathered volcanic flows. Lada Terra also contains volcanic flows with high emissivity anomalies. This region had not been studied using gravity data previously due to the locally low resolution (65-70 spherical harmonic degree and order). Further, the radar data have a high look angle, making it harder to interpret. The high emissivity anomalies inspired Ivanov and Head (2010) to reexamine this region. Their analysis of the geologic setting along with the high emissivity anomalies and the positive gravity anomaly provide evidence that Lada Terra is likely to be recently active. Here we use the spherical harmonic gravity and topography data from Magellan to calculate a geoid-to-topography ratio (GTR) of 23.5±1.6 m/km. This value is in the range of the GTRs previously found for highlands interpreted as hotspots on Venus and provides evidence of a mantle plume at depth. This brings the number of likely hotspots in the southern hemisphere to 4. Although VIRITS did not acquire 1 micron data in the northern hemisphere, the gravity and topography data for the 7 northern hemisphere hotspots indicate active plumes. The similarity of geologic and gravity signatures between northern and southern hemisphere hotspots suggests that all of them may be sites of currently or recently active volcanism. This brings the hotspot count on Venus to 11. Such hotspots could be plausible sources of lower atmospheric water (Smrekar and Sotin, 2012). The presence of ~10 plumes from the core-mantle-boundary on Venus suggests that the mantle may be heating up (Sotin and Smrekar, 2012 - this meeting). (Drossart et al., PSS, 2007; Helbert et al., GRL, 2008; Mueller et al., JGR-P, 2008; Smrekar et al., Sci., 2010; Ivanov and Head, PSS, 2010; Smrekar and Sotin, Icarus, 2012) This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Smrekar, S. E.; Brown, N.

2012-12-01

124

Near infrared imaging of the surface of Venus and implications for crustal composition  

Science.gov (United States)

Venus Express is an ESA spacecraft orbiting Venus since April 2006. The instrument VIRTIS acquires multispectral images in the range from 0.2 to 5 m wavelength. An analysis of VIRTIS images at the wavelengths of the atmospheric window at 1.02 m shows evidence for variation of surface emissivity on the southern hemisphere [Mueller et al. 2008]. Inferred surface emissivity is correlated to some extend with morphological units identified from radar images of the NASA/JPL Magellan mission [Tanaka et al. 1997]. Alpha and Phoebe Regios are highlands mostly composed of tessera terrain, which is defined as a region strongly deformed by compressive and extensional tectonism in at least two directions. In comparison to lowland plains and other less tectonized highlands, these regions generally emit less thermal radiation, which implies lower emissivity. A recent analysis of NIR data from the Galileo fly-by in 1990 finds, that highland regions on Venus on average have a lower emissivity than lowlands [Hashimoto et al. 2008]. As a significant part of Venus highlands in the area observed by Galileo is composed of tessera, this observation is consistent with the observation of Mueller et al. [2008]. In situ measurements by the Venera and Vega landers are at most places consistent with basaltic surface composition. The hypsometry of Venus is unimodal. Inferred lava viscosity of most volcanic features is low, consistent with basaltic composition. All these observations hint towards a crust mostly composed of basalt [Basilevsky et al 1997]. However, no landing site was on tessera terrain, tessera are hypsometrically elevated and the morphology is dominated by tectonic deformation. Among other arguments this leads to the hypothesis that tessera highlands crust is more abundant in feldspar and silica, comparable to lunar highlands or continents on Earth [Nikolaeva et al., 1992]. NIR mapping supports this hypothesis, although other interpretations of the NIR data can not be ruled out. Generation of felsic crust is unlikely under the current climatic and tectonic regime on Venus. The lunar highland crust is believed to be a remnant of an magma ocean [Taylor 1974]. Enrichment in silica as in the continental crust of Earth requires recycling of water into the mantle [Campbell and Taylor 1984]. The surface of Venus is extremely dry and Venus and crustal recycling by plate tectonics does not operate at present. Any crust with felsic bulk composition had to be created during the early history of the planet. In a stratigraphic analysis tessera terrain predates all units it is in contact with [Ivanov and Head 1996]. Tessera terrain is defined by an extensive history of tectonic deformation. Assuming that tessera highlands indeed represent less dense crustal blocks created early in the history of Venus, implications arise from their persistence on the surface of Venus regarding resurfacing mechanism, crustal recycling and thermal evolution. If tessera highlands are enriched in silica relative to basalt this implies existence of a primordial ocean on Venus [Hashimoto et al. 2008]. In either case Venus would even more closely resemble the Earth-Moon system than previously assumed, making Venus an excellent subject for general studies of earth-like planets. Basilevsky, A. T.,et al. (1997), The Resurfacing History of Venus, in Venus II, pp. 1047-1084. Hashimoto, et al. (2008), Galileo Near Infrared Mapping Spectrometer (NIMS) Data Suggests Felsic Highland Crust on Venus, JGR, in press. Ivanov, M. A., et al. (1996), Tessera terrain on Venus: A survey of the global distribution, characteristics, and relation to surrounding units from Magellan data, JGR, 101, 14,861-14,908. Mueller, N., et al. (2008), Venus surface thermal emission at one micrometer in VIRTIS imaging observations - evidence for variation of crust and mantle differentiation conditions, JGR , in press. Nikolaeva, O. V., et al. (1992), Evidence on the crustal dichotomy, pp. 129-139, Venus Geology, Geochemistry, and Geophysics - Research results from the USSR. Tanaka, K. L., et al. (1997), Phy

Müller, N.; Helbert, J.

2009-04-01

125

Undercloud aerosol in Venus 'atmosphere  

International Nuclear Information System (INIS)

Parameters of finely dispersed undercloud aerosol detected from the results of spectrophotometric measurements at descent capsules of Venus - 9, 10, 11 and 12 have been considered. The aerosol is mainly at heights H > or approximately 30 km but sometimes it is also observed at lower heights. Particle size r amounts to 0.05-0.1 ?m. Particles of large sizes (r=0.1+-0.3 ?m) were discovered in the place of Venus 12 landing. Particle concentration and relative-in-mass aerosol content have been evaluated, identification of aerosol particle substance was attemped. Altitudinal dependences of the extinction coefficient have been obtained. The aerosol parameters obtained for the places of Venus 9, 10, 11 and 12 landings agree well between themselves

126

Spaceborne radar studies of Venus  

International Nuclear Information System (INIS)

Data obtained from the Pioneer Venus radar mapper experiment are discussed. The mission was primarily developed to study the atmosphere of Venus. A highly eccentric orbit (eccentricity of 0.84, period of 24 h) was selected. The instrumentation has two operating modes: altimetry and imaging. Three parameters were measured for every radar spot size: altitude, surface roughness and radar reflectivity at a normal incidence. The measurements have been extended to a topographic map. The results suggest that the Beta region consists of two large shields and that the equatorial region is dominated by Aphrodite Terra. It also appears that the surface of Venus is very smooth and that it lacks great basins and the global plate tectonics present on earth

127

The Magellan Venus mapping mission  

Science.gov (United States)

The April 1989 Magellan (MGN) Mission to Venus will initiate a new phase in the exploration of the solar system. In addition to being the first U.S. planetary mission in 10.5 years, it will also be the first such mission to use the Space Shuttle and IUS 2-Stage as launch vehicles. Upon arrival at Venus the spacecraft will begin a systematic mapping of the surface of that planet using side-looking SAR. This paper discusses some of the interesting trade-offs in mission design for this mission in the areas of launch and injection, interplanetary cruise, Venus Orbit insertion, and mapping. The Magellan mapping strategy is discussed briefly along with a few special experiments being considered for the MGN extended mission.

Cutting, E.; Fordyce, J.; Licata, S.; Lyons, D.

1989-01-01

128

Venus project : experimentation at ENEA's pilot site  

International Nuclear Information System (INIS)

The document describes the ENEA's (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III 6398). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry databases. VENUS interfaces to ENEA's databases: cometa materials Module, Cometa Laboratories Module and European Programs. This report contents the results of the experimentation and of the validation carried out in ENEA's related to the Venus generations. Moreover, the description of the architecture, the user requirements syntesis and the validation methodology of the VENUS systems have been included

129

Commissioning of the superconducting ECR ion source VENUS  

International Nuclear Information System (INIS)

VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end. The magnetic confinement configuration consists of three superconducting axial coils and six superconducting radial coils in a sextupole configuration. The nominal design fields of the axial magnets are 4T at injection and 3T at extraction; the nominal radial design field strength at the plasma chamber wall is 2T, making VENUS the world most powerful ECR plasma confinement structure. The magnetic field strength has been designed for optimum operation at 28 GHz. The four-year VENUS project has recently achieved two major milestones: The first plasma was ignited in June, the first mass-analyzed high charge state ion beam was extracted in September of 2002. The pa per describes the ongoing commissioning. Initial results including first emittance measurements are presented

130

Venus Lightning Characteristics and Polar Vortex Correlation  

Science.gov (United States)

Venus Express started taking magnetic field measurements at periapsis in 2006. Since then it has consistently detected whistler-mode signals attributed to lightning. Most, if not all, of these are thought to be intercloud, intracloud, or upward-going lightning; the cloud deck on Venus is at an altitude of about 60 km and thus cloud-to-ground strikes are extremely unlikely. These bursts have peak-to-peak amplitudes of up to1.5 nT in the frequency range 42-60 Hz. They are transverse and right-hand circularly polarized with respect to the background magnetic field. When this field is close to 0 nT, the occurrence rate is very low; it rises sharply at 15-20 nT, then gradually dies off as the field strength further increases. There are very few bursts observed below 200 km; the occurrence rate peaks sharply around 215 km then slowly decreases with increasing altitudes. Burst amplitude distributions and averages are also in agreement with these findings. Between 80 and 90 degrees north latitude, the burst rate with respect to local time maximizes over the terminators. It has been suggested that a burst rate local maximum around 83 degrees north latitude can be attributed to the approximate edge of the polar vortex. We further examine this possibility within this study.

Daniels, J. T. M.; Russell, C. T.; Strangeway, R. J.; Zhang, T. L.

2011-10-01

131

Venus Atmospheric Exploration by Solar Aircraft  

Science.gov (United States)

The Venus atmosphere is a favorable environment for flying powered aircraft. The atmospheric pressure makes flight much easier than on planets such as Mars. Above the clouds, solar energy is available in abundance on Venus, and the slow rotation of Venus allows a solar airplane to be designed for flight within continuous sunlight. The atmosphere between 50 km and 75 km on Venus is one of the most dynamic and interesting regions of the planet. The challenge for a Venus aircraft will be the fierce winds and caustic atmosphere. In order to remain on the sunlit side of Venus, an exploration aircraft will have to be capable of sustained flight at or above the wind speed. An aircraft would be a powerful tool for exploration. By learning how Venus can be so similar to Earth, and yet so different, we will learn to better understand the climate and geological history of the Earth.

Landis, Geoffrey A.; LaMarre, C.; Colozza, A.

2002-01-01

132

A survey of hot flow anomalies at Venus  

Science.gov (United States)

We present the first survey of hot flow anomalies (HFAs) at the bow shock of Venus, expanding on our recent initial case study. A 3.06 sol (774 Earth day) survey of Venus Express magnetometer, ion spectrometer, and electron spectrometer data was undertaken in order to identify Cytherian HFAs. Seven events were discovered, corresponding to a statistical frequency ?1.2±0.8 per day, approximately the same rate as at the Earth. All seven HFAs were centered on a discontinuity in the solar wind, with inward pointing motional electric fields on at least one side, and exhibited electron and ion perturbations consistent with heating. For one event the calculation of continuous electron moments is possible, revealing that electron temperature increased from ?2×105 K to 8×105 K in the HFA core (comparable to terrestrial and Kronian HFA observations), and density increased from ?1 cm-3 to ~2?2.5 cm-3 in the bounding compression regions. Cytherian HFAs were found to be physically smaller (0.4?1.7 Venus radii (RV)) than their terrestrial or Kronian counterparts, although are much larger when compared to the overall size of the system (?130% of the subsolar bow shock distance), and occur very close (1.5?3.0RV) to the planet. Thus, we hypothesize that HFAs have a much more dominant role in the dynamics of the induced magnetosphere of Venus relative to the magnetospheres of magnetized planets.

Collinson, G. A.; Sibeck, D. G.; Masters, A.; Shane, N.; Zhang, T. L.; Fedorov, A.; Barabash, S.; Coates, A. J.; Moore, T. E.; Slavin, J. A.; Uritsky, V. M.; Boardsen, S.; Sarantos, M.

2014-02-01

133

Transmission spectrum of Venus as a transiting exoplanet  

CERN Document Server

On 5-6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus' atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1-5 {\\mu}m and probes the limb between 70 and 150 km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20 ppm as seen from Earth, and from 0.2 to 2.7 {\\mu}m by Mie extinction (~5 ppm at 0.8 {\\mu}m) caused by droplets of sulfuric acid composing an upper haze layer above th...

Ehrenreich, David; Widemann, Thomas; Gronoff, Guillaume; Tanga, Paolo; Barthélemy, Mathieu; Lilensten, Jean; Etangs, Alain Lecavelier des; Arnold, Luc

2011-01-01

134

Characterization of SO2 abundance in Venus' night-side mesosphere from SPICAV/VEX observations  

Science.gov (United States)

Sulfur dioxide (SO _{2}) is a key component of Venus’ atmosphere since the planet is totally covered by H _{2}SO _{4} droplets clouds at altitudes 50-70 km. Any significant change in the SO _{x} oxides above and within the clouds affects the photochemistry in the mesosphere (70-120 km). Recent continuous observations from the Venus Express orbiter (Belyaev et al., 2012; Marcq et al., 2013) and ground-based telescopes (Sandor et al., 2010; Krasnopolsky, 2010; Encrenaz et al., 2012) showed high variability of SO _{2} abundance with years, diurnal time and latitude on the day-side and terminators (commonly from 20 to 500 ppbv above the clouds). In the night-side mesosphere SO _{2} is not photo dissociative but, so far, its behavior has never been explored in details. In this paper we present first results from sulfur dioxide observations made by SPICAV UV spectrometer onboard Venus Express orbiter in regime of stellar occultation (Bertaux et al., 2007). In this mode the instrument observes night-side mesosphere and can register SO _{2} absorption bands in 190-220 nm and CO _{2} bands in 120-200 nm at altitudes from 85 to 110 km (spectral resolution is ˜2 nm). As a result, vertical distribution of SO _{2} and CO _{2} concentrations has been retrieved in observation period from June 2006 to April 2012, at latitude range 60(°) S-60(°) N and Venus local time 20:00-04:00. On the average, mixing ratio of sulfur dioxide fluctuates around ˜100 ppbv along altitude range 90-100 km. Our work is supported by the Program ?22 of RAS and grant of the Russian Government to MIPT. References: Belyaev D. et al., 2012. Vertical profiling of SO _{2} and SO above Venus' clouds by SPICAV/SOIR solar occultations. Icarus 217, 740-751. Bertaux J.-L. et al., 2007. SPICAV on Venus Express: three spectrometers to study the global structure and composition of Venus atmosphere. Planet. Space Sci. 55, 1673-1700. Encrenaz T. et al., 2012. HDO and SO _{2} thermal mapping on Venus: evidence for strong SO _{2} variability. A&A 543, A153. Krasnopolsky V.A., 2010. Spatially-resolved high-resolution spectroscopy of Venus. 2. Variations of HDO, OCS, and SO _{2} at the cloud tops. Icarus 209, 314-322. Marcq E. et al., 2013. Variations of sulphur dioxide at the cloud top of Venus’s dynamic atmosphere. Nature Geoscience, vol. 6, 25-28. DOI: 10.1038/NGEO1650. Sandor B.J. et al., 2010. Sulfur chemistry in the Venus mesosphere from SO _{2} and SO microwave spectra. Icarus 208, 49-60.

Belyaev, Denis; Fedorova, Anna; Piccialli, Arianna; Marcq, Emmanuel; Montmessin, Franck; Bertaux, Jean-Loup; Evdokimova, Daria

135

Ion heating near the ion composition boundary at Venus  

Science.gov (United States)

In this study we focus on the boundary layer above the ionopause of Venus. The first measurements which demonstrated the existence of such a boundary layer were those of the electron energy spectra obtained by the Pioneer Venus Orbiter Retarding Potential Analyser (ORPA) [Spenner et al., 1980, JGR]. The measurements of the ASPERA-4 electron spectrometer on board Venus Express (VEX) confirmed the existence of such a layer [Coates et al. 2008, Planetary and Space Sci.]. The upper end of the interaction layer, where planetary ions disappear, is called ion composition boundary (ICB). Due to the interaction of the two plasma populations near the ICB - the shocked solar wind and planetary ions - instabilities are excited. Significant collisionless momentum and energy exchange takes place because of wave-particle interaction, creating a highly turbulent layer. In earlier works we proposed that modified two stream instabilities (MTSI) excited there (see e.g. Dobe et al., 1999, Phys. Rev. Lett., 83, pp. 260-263) might explain the 100-Hz waves observed by the electric field detector (OEFD) on board PVO in the dayside of Venus. The instability also heats the ions. PVO data covered only partially the energy range of the particles in question. Using the much better 3-D energy and spatial coverage of the Analyser of Space Plasmas and Energetic Atoms (ASPERA-4) instrument suite on board VEX, we compare here with data the charged particle heating due to the MTSI. The first data set is for average solar wind conditions, the second one is for a case when a strong solar storm hit Venus. This analysis will be expanded in the future to have a broader picture on planetary space weather effects. After having summarised the properties of the modified two stream instability, and the ion heating and ion acceleration mechanism in the framework of a numerical hybrid model which retains electron inertia, we show that MTSI works effectively. We also discuss the limits of this approach.

Szegö, Karoly; Dobe, Zoltan; Bebesi, Zsofia; Coates, Andrew; Foldy, Lajos; Fraenz, Markus; Opitz, Andrea; Vech, Daniel

2014-05-01

136

Volcanism of Venus: Insights from the VMC data analysis  

Science.gov (United States)

The analysis of the Venera 15/16 and Magellan data led to an understanding of Venus geology which may be described as a time sequence of material and structural units and features [e.g., (Basilevsky and Head, 1995, 2000; Ivanov and Head, 2011]. Dominant among them are various volcanic plains and volcanic constructs whose morphologies indicate a low viscosity for the lavas composing them suggesting mostly basaltic composition [e.g., Head et al., 1992; Crumpler et al., 1997]. This is supported by the analyses of surface composition at the Venera-Vega sites [e.g., Surkov, 1986]. However, some volcanic features of Venus could be composed of nonbasaltic lavas [e.g., Pavri et al., 1992; Crumpler et al., 1997; Ivanov and Head, 1999] but this suggestion needs more study. Based on the analysis of the characteristics of impact crater populations on Venus [e.g., McKinnon et al., 1997] as well as on the analysis of the unit superposition/embayment relations [Basilevsky and Head, 1996, 2000, 2006; Collins et al., 1999] it was shown that the widespread regional volcanic plains formed close to the beginning of morphologically visible history of this planet that is 0.5-1 b.y. ago. Later in time, volcanic activity on Venus continued in different areas at different times, including very close to the present. No conclusive evidence of ongoing volcanic activity has yet been found, although some indications of very recent volcanic events have been published [Bondarenko et al., 2010; Smrekar et al., 2010]. Analysis of the data taken by the Venus Monitoring Camera (VMC) onboard of Venus Express, which has two NIR, one visible and one UV channels, allowed to revealed some promising results on the questions of nonbasaltic volcanism [e.g., Basilevsky et al., 2012] and the ongoing volcanic activity on Venus [e.g., Shalygin et al., 2014]. The VMC results presented in the context of characteristics of Venusi volcanism will be the main emphasis of the talk.

Bazilevskiy, Alexander; Ignatiev, Nikolay; Markiewicz, Wojciech; Head, James; Titov, Dmitrij; Shalygin, Eugene V.

137

Mars is close to venus--female reproductive proteins are expressed in the fat body and reproductive tract of honey bee (Apis mellifera L.) drones.  

Science.gov (United States)

Vitellogenin (Vg) and lipophorin (Lp) are lipoproteins which play important roles in female reproductive physiology of insects. Both are actively taken up by growing oocytes and especially Vg and its receptor are considered as female-specifically expressed. The finding that the fat body of in honey bee (Apis mellifera) drones synthesizes Vg and is present in hemolymph has long been viewed as a curiosity. The recent paradigm change concerning the role played by Vg in honey bee life history, especially social division of labor, has now led us to investigate whether a physiological constellation similar to that seen in female reproduction may also be represented in the male sex. By means of Western blot analysis we could show that both Vg and Lp are present in the reproductive tract of adult drones, including the accessory (mucus) glands, but apparently are not secreted. Furthermore, we analyzed the transcript levels of the genes encoding these proteins (vg and lp), as well as their putative receptors (Amvgr and Amlpr) in fat body and accessory glands. Whereas lp, vg and Amlpr transcript levels decreased with age in both tissues, Amvgr mRNA levels increased with age in fat body. To our knowledge this is the first report that vitellogenin and its receptor are co-expressed in the reproductive system of a male insect. We interpret these findings as a cross-sexual transfer of a social physiological trait, associated with the rewiring of the juvenile hormone/vitellogenin circuitry that occurred in the female sex of honey bees. PMID:20600084

Colonello-Frattini, Nínive Aguiar; Guidugli-Lazzarini, Karina Rosa; Simões, Zilá Luz Paulino; Hartfelder, Klaus

2010-11-01

138

Models of the internal structure of Venus  

International Nuclear Information System (INIS)

A survey is made of the physics of the interiors of Venus. The introduction explains the main concepts used in the construction of models of Venus and the history of the question; observational data are gathered and analyzed. The method of constructing the models of the planet is explained and earth-like models of Venus and parametrically simple PVM models are discussed. Within the compass of a physical model of Venus, the thermodynamics of the mantle and core is constructed and questions are discussed concerning the heat conduction, temperature distribution in the lithosphere and the thermal flux from the interior of Venus, the electrical conduction and mechanical quality, and large-scale steady stresses in the mantle of Venus. A rheological model of the crust and mantle is constructed. In conclusion, the question as to the distribution of radioactivity and convection in the interior of the planet is discussed. (Auth.)

139

Models of the internal structure of Venus  

Science.gov (United States)

A survey is made of the physics of the interior of Venus. The introduction explains the main concepts used in the construction of models of Venus and the history of the question; observational data are gathered and analyzed. The method of constructing the models of the planet is explained, and earth-like and parametrically simple models of Venus are discussed. Within the compass of a physical model of Venus, the thermodynamics of the mantle and core is constructed; and questions are discussed concerning the heat conduction, temperature distribution in the lithosphere and the thermal flux from the interior of Venus, the electrical conduction and mechanical quality, and large-scale steady stresses in the mantle of Venus. A rheological model of the crust and mantle is constructed. In conclusion, the question as to the distribution of radioactivity and convection in the interior of the planet is discussed.

Zharkov, V. N.

1983-10-01

140

Abstracts for the venus geoscience tutorial and venus geologic mapping workshop  

International Nuclear Information System (INIS)

Abstracts and tutorial are presented from the workshop. Representative titles are: Geology of Southern Guinevere Planitia, Venus, Based on Analyses of Goldstone Radar Data; Tessera Terrain: Characteristics and Models of Origin; Venus Volcanism; Rate Estimates from Laboratory Studies of Sulfur Gas-Solid Reactions; and A Morphologic Study of Venus Ridge Belts

 
 
 
 
141

A Venus Rover Capable of Long Life Surface Operations  

Science.gov (United States)

Access to the surface of Venus would allow planetary scientists to address a number of currently open questions. Among these are the elemental and mineralogical composition of the surface; the interaction of the surface with the atmosphere; the atmospheric composition, especially isotope ratios of key species; the nature of the planetary volcanism (present activity, emissions to the atmosphere, and composition); planetary seismicity; the local surface meteorology (winds and pressure variability); and the surface geology and morphology at particular locations on the surface. A long lived Venus rover mission could be enabled by utilizing a novel Stirling engine system for both cooling and electric power. Previous missions to the Venus surface, including the Pioneer Venus and Venera missions, survived for only a few hours. The rover concept described in the present study is designed for a surface lifetime of 60 days, with the potential of operating well beyond that. A Thermo-Acoustic Stirling Heat Engine (TASHE) would convert the high-temperature (~1200 °C) heat from General Purpose Heat Source (GPHS) modules into acoustic power which then drives a linear alternator and a pulse tube cooler to provide electric power and remove the large environmental heat load. The "cold" side of the engine would be furnished by the ambient atmosphere at 460 °C. This short study focused on the feasibility of using the TASHE system in this hostile environment to power a ~650 kg rover that would provide a mobile platform for science measurements. The instrument suite would collect data on atmospheric and surface composition, surface stratigraphy, and subsurface structure. An Earth-Venus-Venus trajectory would be used to deliver the rover to a low entry angle allowing an inflated ballute to provide a low deceleration and low heat descent to the surface. All rover systems would be housed in a pressure vessel in vacuum with the internal temperature maintained by the TASHE below 50 °C. No externally deployed or articulated components would be used and penetrations through the pressure vessel are minimized. Science data would be returned direct to Earth using S-Band to minimize atmospheric attenuation.

Evans, M.; Shirley, J. H.; Abelson, R. D.

2005-12-01

142

The Transit of Venus: an Opportunity to Promote Astronomy  

Science.gov (United States)

The transit of Venus was an excellent opportunity to promote Astronomy to everybody. In particular this occasion was used to encourage interest in Astronomy in schools. In our society, which has a good quality of life, interest in science has decreased. Every year the number of students interested in studying science degrees at university is smaller than in previous years. Our new generations do not seem to be motivated to study in the field of science. Probably this situation is a consequence of the lack of understanding of the true meaning of science. Of course, it is not possible that a student would decide to study a topic that they do not know about. In the media science appears less than sports, cinema, or business! In consequence, the general public is more concerned about items other than science. On June 8th we took advantage of an opportunity to introduce science and Astronomy into the lives of everybody, but especially in schools. This paper will show two projects related to the transit in schools: ”Pilla el Tránsito de Venus” and ”VT-2004” and a short appendix to another project for schools ”ALMA-ITP”

Ros, R. M.

143

Mid-day naked-eye Venus  

Science.gov (United States)

It is generally believed that Venus may be seen with the naked eye in daylight at any time of the day. However, I could not actually find any documents indicating that Venus had been seen in the middle of the day! We now wish to correct that omission: my 4th-year students and I, on Wednesday 2004 April 28, succeeded in observing Venus at noon with the naked eye. It happened in Sana'a the capital city of Yemen.

Sultan, A. H.

2004-10-01

144

Next generation ECR ion sources: First results of the superconducting 28 GHz ECRIS - VENUS  

International Nuclear Information System (INIS)

VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (rare isotope accelerator) front end. The goal of the VENUS ECR ion source project as the RIA R and D injector is the production of 200 e?A of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 e?A of U48+, a low current, very high charge state beam. To achieve those ambitious goals, the VENUS ECR ion source has been designed for optimum operation at 28 GHz. The nominal design fields of the axial magnets are 4 T at injection and 3 T at extraction; the nominal radial design field strength at the plasma chamber wall is 2 T, making VENUS currently the world's most powerful ECR plasma confinement structure. Recently, the six year project has made significant progress. In June 2002, the first plasma was ignited at 18 GHz. During 2003, the VENUS ECR ion source was commissioned at 18 GHz, while preparations for 28 GHz operation were being conducted. In May 2004 28 GHz microwave power has been coupled into the VENUS ECR ion source for the first time. Preliminary performance-tests with oxygen, xenon and bismuth at 18 GHz and 28 GHz have shown promising resuGHz and 28 GHz have shown promising results. Intensities close to or exceeding the RIA requirements have been produced for those few test beams. The paper will briefly describe the design of the VENUS source and its beam analyzing system. Results at 18 GHz and 28 GHz including first emittance measurements will be described

145

Hotspots on Venus: Possible recent activity at Themis Regio  

Science.gov (United States)

Themis Regio, Venus is a 2300 x 1700 km topographic rise, with an average height of about 0.5 km. It is one of the ~10 hotspots on Venus, thought to be underlain by a mantle plume (e.g., Stofan and Smrekar, 2005). Thirteen coronae are located on the rise, with an additional six in the surrounding region (Stofan and Brian, 2012). In addition, six volcanoes with diameters > 100 km are found on and near the rise, along with numerous intermediate and smaller volcanoes. The Themis rise lies at the western end of the Parga Chasma rift system. Flows associated with Themis coronae, volcanoes and plains both superpose and are cut by Parga fractures and graben. Recent mapping of Themis Regio reveals a complex history of corona, volcano and rift formation that has overlapped in time and space (Stofan and Brian, 2012). Smrekar and Stofan (1999) found that gravity data for Themis was best fit by a bottom-loading model with an elastic thickness estimate of 22 km, a crustal thickness of 10 km, and an apparent depth of compensation of 80-110 km. The observed range in morphologies of the Themis coronae indicating a range in stages of evolution, along with the delamination signal seen in the gravity data, and the broad topographic swell indicate that Themis is likely to be underlain by an active plume with ongoing surface deformation due to delamination. In addition, the complex sequence of corona formation observed at Themis suggests that a series of small-scale upwellings over time are responsible for corona formation, rather than nearly simultaneously from the break-up of a single large-scale mantle plume (Stofan and Smrekar, 2005). VIRTIS data from the Venus Express mission has provided evidence that relatively recent volcanic activity may have occurred in the region (Smrekar et al., 2010). Fifteen locations on or near the Themis rise have elevated values of emissivity in the VIRTIS data. We investigate all of these regions, and find them to be correlated with areas of volcanic activity, associated with either coronae or volcanoes. While a few of the high emissivity spots are associated with steep-sided domes, most are associated with flows that are likely to be basaltic in origin. The anomalies occur on both topographically elevated terrain as well as on relatively low-lying plains. Based on their morphology and stratigraphic relations with surrounding units, we interpret all of the features to provide evidence of volcanic activity that likely occurred within the last 250,000 years (e.g., Smrekar et al., 2010). References: Smrekar, S.E. and E.R. Stofan, Icarus 139, 100, 1999; Smrekar, S.E. et al., Science 328, 305, 2010; Stofan, E.R. and A.W. Brian, U.S.G.S. SIM- 3165, 2012; Stofan, E.R. and S.E. Smrekar, GSA Spec. Paper 388, 841, 2005.

Stofan, E. R.; Smrekar, S. E.; Helbert, J.; Mueller, N. T.

2012-12-01

146

Radar observation of Venus' terrestrial analogues using TecSAR X-band SAR  

Science.gov (United States)

Venus is shrouded in a dense CO2 atmosphere that prevents us from viewing the surface in visible light or with optronic sensors. Long wavelengths are required to 'see' through the dense atmosphere. In the early 1990s, the S-band synthetic aperture radar of the Magellan spacecraft acquired images of a variety of surface features on Venus, including morphologies attributed to wind processes. These include sand dunes, wind-sculpted hills (yardangs), and almost 6000 wind streaks. These aeolian landscapes were formed and shaped by near surface atmospheric circulation and local winds. These can serve as local markers, each providing an integrated wind direction. Since the Magellan mission, there were no missions to Venus until the Venus Express Mission of 2005 to examine the upper atmosphere. The future will probably include high-resolution SAR images of Venus. This poster will demonstrate high resolution SAR images in X-band from the TecSAR sensor launched by Israel in 2008. Observations of wind streaks, dunes and impact craters in desert areas will show the wealth of information that is extracted from high-res X-band data. Detailed images of Aurounga impact crater in Chad, Kelso dunes, California and Pisgah lava flow show immense detail of the morphologies associated with these features. These are compared with Magellan images of sites on Venus and SRL data in C and L-bands. The X-band provides extremely high resolution and resembles optical data much more than the longer wavelengths.

Blumberg, D. G.

2012-04-01

147

Magellan at Venus - First results  

International Nuclear Information System (INIS)

First results of mapping the Venusian surface on the basis of data from the Magellan spacecraft are presented, together with the description of the Magellan measurement instruments. These consist of a SAR, which bounces short pulses of radio energy off the planet's surface for 37 min of each orbit, when it is closest to Venus, and a radar altimeter, which repeatedly determines the height of the landscape directly below it. The paper describes key features of several impact craters mapped by Magellan, including the Crater Golubkina, the crater farm and the Gumby feature near the Lavinia Planitia region, a 9 x 12-km kidney-shaped crater, and a radar-bright feature considered to be an evidence of explosive volcanism on Venus

148

How the Venus Flytrap Snaps  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100 ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as "one of the most wonderful in the world". The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of the trigger hairs to stimuli and quantified the propagation of action potentials in the leaves. Here we complement these studies by consideri...

Forterre, Yoel; Skotheim, Jan M.; Dumais, Jacques; Mahadevan, Lakshminarayanan

2005-01-01

149

Substorm activity in Venus's magnetotail  

Directory of Open Access Journals (Sweden)

Full Text Available The magnetotail of the induced magnetosphere of Venus is investigated through the magnetic field and plasma data of Venus Express. A comparison is made between two neutral sheet crossings. One crossing shows the magnetic field is rather quiet and the plasma instrument indicates a change from energetic (few 100 eV to low energy (few 10 eV ions. The other crossing shows more dynamics in the magnetic field, including signatures that are interpreted as characteristic of a reconnection site, and the plasma instrument indicates ions that are energized to 1500 to 2000 eV, in the same magnetospheric region where in the first crossing only low energy ions showed up.

M. Volwerk

2009-06-01

150

Memristors in the Venus flytrap.  

Science.gov (United States)

A memristor is a nonlinear element because its current-voltage characteristic is similar to that of a Lissajous pattern for nonlinear systems. We investigated the possible presence of memristors in the electrical circuitry of the Venus flytrap's upper and lower leaves. The electrostimulation of this plant by bipolar sinusoidal or triangle periodic waves induces electrical responses in the upper and lower leaves of the Venus flytrap with fingerprints of memristors. The analysis was based on cyclic voltammetric characteristics where the memristor, a resistor with memory, should manifest itself. Tetraethylammonium chloride, an inhibitor of voltage gated K(+) channels, or NPPB, a blocker of voltage gated Cl(-) and K(+) channels, transform a memristor to a resistor in plant tissue. Uncouplers carbonylcyanide-3-chlorophenylhydrazone (CCCP) and carbonylcyanide-4-trifluoromethoxy-phenyl hydrazone (FCCP) decrease the amplitude of electrical responses at low and high frequencies of bipolar periodic electrostimulating waves. Our results demonstrate that voltage gated K(+) channels in the Venus flytrap have properties of memristors of type 1 and type 2. The discovery of memristors in plants creates a new direction in the modeling and understanding of electrical phenomena in plants. PMID:24837439

Volkov, Alexander G; Forde-Tuckett, Victoria; Reedus, Jada; Mitchell, Colee M; Volkova, Maya I; Markin, Vladislav S; Chua, Leon

2014-05-16

151

Lunar & Planetary Science Conference.  

Science.gov (United States)

Summaries of different topics discussed at the Lunar and Planetary Science Conference are presented to provide updated information to nonplanetologists. Some topics include Venus, isotopes, chondrites, creation science, cosmic dust, cratering, moons and rings, igneous rocks, and lunar soil. (DC)

Warner, Jeffrey L.; And Others

1982-01-01

152

ESA `Huygens and Mars Express' science highlights - call to press  

Science.gov (United States)

Almost one year has passed since ESA’s Huygens probe landed on Saturn’s largest moon, Titan. Today, a set of new wide-ranging results from the probe’s two-and-a-half hour descent and landing, part of the extraordinary NASA/ESA/ASI Cassini-Huygens mission to Saturn and its moons, is ready for release. At the same time, ESA’s Mars Express mission is continuing its investigations of Mars, painting a new picture of the 'red planet'. This includes the first ever probing below the surface of Mars, new geological clues with implications for the climate, newly-discovered surface and atmospheric features and, above all, traces of the presence of water on this world. These and other exciting findings from just one year of observations and data analysis - in the context of ESA’s overall scientific achievements - will be the focus of a press conference to be held at ESA Headquarters in Paris at 16:00 on 30 November 2005. Media interested in attending are invited to complete the following registration form. Press conference programme Space Science Highlights 2005 From Huygens to Mars Express 30 November 2005, 16:00 hrs Room 137, European Space Agency Headquarters 8-10 Rue Mario-Nikis, F-75738 Paris Cedex, France 15:30 - Registration 16:00 - A Year of European Space Science Successes Prof. David Southwood, ESA Director of Science Programme 16:10 - Highlights of the Huygens Mission Results Jean-Pierre Lebreton, ESA Huygens Project Scientist 16:15 - Robin Duttaroy, Co-Investigator, Doppler Wind Experiment, University of Bonn, Germany 16:20 - Marcello Fulchignoni , Principal Investigator, Huygens Atmospheric Structure Instrument, Université de Paris 7, France 16:25 - John Zarnecki, Principal Investigator, Surface Science Package, Open University, UK 16:30 - François Raulin, Co-Investigator, Gas Chromatograph Mass Spectrometer, Université de Paris 12 - Créteil, France 16:35 - Guy Israel, Principal Investigator, Aerosol Collector and Pyrolyser, Service d'Aéronomie/CNRS, France 16:40 - Bruno Bezard, Co-Investigator, Descent Imager/Spectral Radiometer, Laboratoire d'études spatiales et d'instrumentation en astrophysique, Observatoire de Paris, France 16:45 - Jonathan Lunine, Interdisciplinary Scientist, Titan surface-atmosphere interactions, LPL/U, Arizona (USA) and INAF/IFSI, Rome (Italy) 16:55 - Questions and AnswersV 17:05 - Coffee break 17:10 - Mars Express: results in the overall context of Martian science, Agustin Chicarro, ESA Mars Express Project Scientist 17:15 - Giovanni Picardi, MARSIS Radar Principal Investigator, University of Rome La Sapienza, Italy Jeffrey Plaut, MARSIS Co-Principal Investigator, NASA/JPL, USA 17:25 - Martin Pätzold, Mars Radio Science Experiment, Principal Investigator, Universität Koln, Cologne, Germany 17:30 - Jean-Pierre Bibring, OMEGA Principal Investigator, Institut d’Astrophysique spatiale, Orsay, France 17:40 - Gerhard Neukum, HRSC Camera Principal Investigator, Freie Universität Berlin, Germany 17:45 - Questions and Answers 17:55 - Interview opportunities

2005-11-01

153

Pioneer Venus Orbiter (PVO) Ionosphere Evidence for Atmospheric Escape  

Science.gov (United States)

An early estimate of escape of H2O from Venus [McElroy et al., 1982] using observed hot oxygen densities inferred by Nagy et al. [1981] from PVO OUVS 1304 Å dayglow and using ionization rates from photoionization and electron impact. This resulted in an estimated oxygen ionization rate planet-wide above the plasmapause of 3x1025 atoms/s. Based on the energetic O+ being swept up and removed by solar wind, McElroy et al. [1982] gave an estimate of a loss rate for O of 6x106 atoms/cm2/s. Using a different method of estimating escape based data in the ionotail of Venus, Brace et al. [1987] estimated a total planetary O+ escape rate of 5x1025 ions/s. Their estimate was based on PVO measurements of superthermal O+ (energy range 9-16 eV) in the tail ray plasma between 2000 and 3000 km. Their estimated global mean flux was 107 atoms/cm2/s. The two escape rates are remarkably close considering all the errors involved in such estimates of escape. A study of escape by Luhmann et al. [2008] using VEX observations at low solar activity finds modest escape rates, prompting the authors to reconsider the evidence from both PVO and VEX of the possibility of enhanced escape during extreme interplanetary conditions. We reexamine the variation of escape under different solar wind conditions using ion densities and plasma content in the dayside and nightside of Venus using PVO ionosphere density during times of high solar activity. Citations: Brace, L.H., W. T. Kasprzak, H.A. Taylor, R. F. Theis, C. T. Russess, A. Barnes, J. D. Mihalov, and D. M. Hunten, "The Ionotail of Venus: Its Configuration and Evidence for Ion Escape", J. Geophys. Res. 92, 15-26, 1987. Luhmann, J.G., A. Fedorov, S. Barabash, E. Carlsson, Y. Futaana, T.L. Zhang, C.T. Russell, J.G. Lyon, S.A. Ledvina, and D.A. Brain, “Venus Express observations of atmospheric oxygen escape during the passage of several coronal mass ejections”, J. Geophys. Res., 113, 2008. McElroy, M. B., M. J. Prather, J. M. Rodiquez, " Loss of Oxygen from Venus", Geophys. Res. Lett., 9, 649-651, 1982.

Grebowsky, J. M.; Hoegy, W. R.

2009-12-01

154

Mission and System Design of a Venus Entry Probe and Aerobot  

Science.gov (United States)

The Venus Entry Probe study is one of the European Space Agency's (ESA) technology reference studies. It aims to identify; the technologies required to develop a low-cost, science-driven mission for in-situ exploration of the atmosphere of Venus, and the philosophy that can be adopted. The mission includes a science gathering spacecraft in an elliptical polar Venus orbit, a relay satellite in highly elliptical Venus orbit, and an atmospheric entry probe delivering a long duration aerobot (aerial robot) which will drop several microprobes during its operational phase. The atmospheric entry sequence is initiated at 120 km altitude and an entry velocity of 9.8 km s-1. Once the velocity has reduced to 15 m s-1 the aerobot is deployed. This consists of a gondola and balloon and has a floating mass of 32 kg (which includes 8 kg of science instruments and microprobes). To avoid Venus' crushing surface pressure and high temperature an equilibrium float altitude of around 55 km has been baselined. The aerobot will circumnavigate Venus several times over a 15-22 lifetime analysing the Venusian middle cloud layer. Science data will be returned at 2.5 kbps over the mission duration. At scientifically interesting locations 15 drop-sondes will be released. This paper focuses on the final mission design with particular emphasis on system level trade-offs including the balloon and pressurisation system, communications architecture, power system, design for mission lifetime in a hostile and acidic environment. It discusses the system design, design drivers and presents an overview of the innovative mission- enabling and mission-enhancing technologies.

Phipps, A.; Woodroffe, A.; Gibbon, D.; Alcindor, P.; Joshi, M.; da Silva Curiel, A.; Ward, J.; Sweeting, M.; Underwood, J.; Lingard, S.; van den Berg, M.; Falkner, P.

155

Recent progress on the superconducting ion source VENUS  

Energy Technology Data Exchange (ETDEWEB)

The 28 GHz Ion Source VENUS (versatile ECR for nuclear science) is back in operation after the superconducting sextupole leads were repaired and a fourth cryocooler was added. VENUS serves as an R and D device to explore the limits of electron cyclotron resonance source performance at 28 GHz with its 10 kW gryotron and optimum magnetic fields and as an ion source to increase the capabilities of the 88-Inch Cyclotron both for nuclear physics research and applications. The development and testing of ovens and sputtering techniques cover a wide range of applications. Recent experiments on bismuth demonstrated stable operation at 300 e{mu}A of Bi{sup 31+}, which is in the intensity range of interest for high performance heavy-ion drivers such as FRIB (Facility for Rare Isotope Beams). In addition, the space radiation effects testing program at the cyclotron relies on the production of a cocktail beam with many species produced simultaneously in the ion source and this can be done with a combination of gases, sputter probes, and an oven. These capabilities are being developed with VENUS by adding a low temperature oven, sputter probes, as well as studying the RF coupling into the source.

Benitez, J. Y.; Franzen, K. Y.; Hodgkinson, A.; Loew, T.; Lyneis, C. M.; Phair, L.; Saba, J.; Strohmeier, M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Tarvainen, O. [Accelerator Laboratory, Department of Physics, University of Jyvaeskylae, FIN-40014 (Finland)

2012-02-15

156

Magma vesiculation and pyroclastic volcanism on Venus  

Science.gov (United States)

Theoretical consideration of the magma vesiculation process under observed and inferred venusian surface conditions suggests that vesicles should form in basaltic melts, especially if CO2 is the primary magmatic volatile. However, the high surface atmospheric pressure (about 90 bars) and density on Venus retard bubble coalescence and disruption sufficiently to make explosive volcanism unlikely. The products of explosive volcanism (fire fountains, convecting eruption clouds, pyroclastic flows, and topography-mantling deposits of ash, spatter, and scoria) should be rare on Venus, and effusive eruptions should dominate. The volume fraction of vesicles in basaltic rocks on Venus are predicted to be less than in chemically similar rocks on earth. Detection of pyroclastic landforms or eruption products on Venus would indicate either abnormally high volatile contents of Venus magmas (2.5-4 wt%) or different environmental conditions (e.g., lower atmospheric pressure) in previous geologic history.

Garvin, J. B.; Head, J. W.; Wilson, L.

1982-01-01

157

Venus Atmospheric Circulation from Digital Tracking of VMC Images  

Science.gov (United States)

The Venus Monitoring Camera on Venus Express has been returning images of Venus in four filters since April 2006 on almost every orbit. These images portray the southern hemisphere of Venus at spatial resolutions ranging from ~ 50 km per pixel to better than ~ 10 km per pixel depending on when the planet was imaged from orbit. Images covering a substantial portion of the planet and separated by ~ 45 min to one hour have been mapped into rectilinear projection to enable use of digital tracking technique for the measurement of cloud motions on an orbit by orbit basis. The aggregate results are in good agreement with visual tracking results as well as from the previous missions [1] and show evidence of temporal variations, large scale waves and solar thermal tides in low and mid latitudes. The digital tracking results for the meridional component confirm the poleward flow increasing from low latitudes to mid-latitudes and then showing a tendency to weaken. However, the confidence in high latitude measurements is lower due to the peculiar nature of the cloud morphology that is generally streaky and quite different from the low latitudes. The meridional profile of the average zonal wind at higher latitudes is of considerable interest. At high and polar latitudes, a vortex organization is evident in the data consistently, with the core region centered over the pole. The images show variability in structure of the ultraviolet signature of the "S" shaped feature seen in the VIRTIS data on the capture orbit [2]. However, the cloud morphologies seen poleward of ~ 50 degrees latitude also makes digital tracking less reliable due to absence of discrete features at the spatial resolution of the VMC images acquired in the apoapsis portion of the Venus Express orbit. It is expected that images obtained closer to the planet will enable a determination of the zonal wind profile with better confidence which will be useful in elucidating the nature of the transient features seen in the core region of the Venus vortex. References [1] Limaye, S. S. Venus atmospheric circulation: Known and unknown, J. Geophys. Res., 112, E04S09, doi:10.1029/2006JE002814 (2007). [2] Piccioni, G, Drossart, P., Sanchez-Lavega, A., Hueso, R., Taylor, F., Wilson, C., Grassi, D., Zasova, L., Moriconi, M., Adriani, A., Lebonnois, S., Coradini, A., Bézard, B., Angrilli, F., Arnold, G., Baines, K. H., Bellucci, G., Benkhoff, J., Bibring, J. P., Blanco, A., Blecka, M. I., Carlson, R. W., Di Lellis, A., Encrenaz, T., Erard, S., Fonti1, S., Formisano, V., Fouchet, T., Garcia1, R., Haus, R., J. Helbert, J., Ignatiev, N. I., Irwin, P., Langevin,Y.,Lopez-Valverde, M. A., Luz, D., Marinangeli, L., Orofino, V., Rodin, A. V., Roos-Serote, M. C., Saggin, B., ,Stam, D. M., Titov, D., Visconti, G., and Zambelli M. South-polar features on Venus similar to those near the north, Nature, 450, 637-640, doi:10.1038/nature06209 (2007).

Limaye, S.; Moissl, R.; Markiewicz, W.; Titov, D.

2008-09-01

158

Magnetic energy density and plasma energy density in the Venus wake  

Science.gov (United States)

Magnetic energy density and plasma energy density in the Venus wake H. Pérez-de-Tejada1, H. Durand-Manterola1, R. Lundin2, S. Barabash2, T. L. Zhang3, A. Sauvaud4, M. Reyes-Ruiz5. 1 - Institute of Geophysics, UNAM, México, D. F. 2 - Swedish Institute of Space Physics, Umea, Sweden 3 - Space Research Institute, Graz, Austria 4 - CESR, Toulouse, France 5 - Institute of Astronomy, UNAM, Ensenada, México Measurements conducted in the Venus wake with the magnetometer and the Aspera-4 plasma instrument of the Venus Express spacecraft show that average values of the kinetic energy density of the plasma in that region are comparable to average local values of the magnetic energy density. Observations were carried out in several orbits of the Venus Express near the midnight plane and suggest that the total energy content in the Venus wake is distributed with nearly comparable values between the plasma and the magnetic field. Processes associated with the solar wind erosion of planetary ions from the polar magnetic regions of the ionosphere are involved in the comparable distribution of both energy components.

Perez De Tejada, H. A.; Durand-Manterola, H. J.; Lundin, R.; Barabash, S.; Zhang, T.; Reyes-Ruiz, M.; Sauvaud, J.

2013-05-01

159

Venus atmospheric platform options revisited  

Science.gov (United States)

Various balloon systems intended as scientific platforms to float in the atmosphere of Venus at altitudes between about 35 and 65 km are briefly reviewed. Previous predictions of the altitude oscillations of balloons filled with helium gas and water vapor are largely confirmed through numerical simulation and analysis. The need for refined thermal modelling is emphasised. Several novel technical concepts are introduced. It is concluded that phase change balloons would be more suitable than non-condensing super pressure gas balloons when repeated altitude excursions are a mission requirement.

Dorrington, G. E.

2010-08-01

160

Distant interplanetary wake of Venus: plasma observations from pioneer Venus  

International Nuclear Information System (INIS)

In June 1979 the Pioneer Venus orbiter made its first series of passes through the distant solar wind wake of Venus at distances of 8--12 R/sub V/ behind the planet. During this period the plasma analyzer aboard the spacecraft detected disturbed magnetosheath plasma that intermittently disappeared and reappeared, suggesting a tattered, filamentary cavity trailing behind the planet. The magnetosheath dropouts almost always occurred inside the region of 'magnetotail' observed by Russell et al. Sporadic bursts of energetic ions (E/q> or approx. =4kV) are detected inside and, occasionally, outside the magnetotail; all such bursts are consistent with identification of the ion as O+ of planetary origin moving at the local magnetosheath flow speed. The morphology of the plasma dropouts and of the O+ bursts is analyzed in detail. The cavity appears to contract at times of high solar wind dynamic pressure. The intensity of the O+ component is highly variable, and appears not to be strongly correlated with solar wind dynamic pressure. The most intense bursts correspond to a flux 7 ions cm-2 s-1. This maximum flux, if steady and filling a cylinder 1 R/sub V/ in radius would correspond to a mass loss rate of 25 ions s-1; the intermittency and variability of the flux suggest that the true mean loss rate is very much lower. The kinmean loss rate is very much lower. The kinetic temperature of the O+ component is estimated as 105--106 K in order of magnitude

 
 
 
 
161

Quantitative tests for plate tectonics on Venus  

Science.gov (United States)

Quantitative comparisons are made between the characteristics of plate tectonics on the earth and those which are possible on Venus. Considerations of the factors influencing rise height and relating the decrease in rise height to plate velocity indicate that the rate of topographic dropoff from spreading centers should be about half that on earth due to greater rock-fluid density contrast and lower temperature differential between the surface and interior. Statistical analyses of Pioneer Venus radar altimetry data and global earth elevation data is used to identify 21,000 km of ridge on Venus and 33,000 km on earth, and reveal Venus ridges to have a less well-defined mode in crest heights and a greater concavity than earth ridges. Comparison of the Venus results with the spreading rates and associated heat flow on earth reveals plate creation rates on Venus to be 0.7 sq km/year or less and indicates that not more than 15% of Venus's energy is delivered to the surface by plate tectonics, in contrast to values of 2.9 sq km a year and 70% for earth.

Kaula, W. M.; Phillips, R. J.

1981-01-01

162

Summing Up the Unique Venus Transit 2004 (VT-2004) Programme  

Science.gov (United States)

On June 8, 2004, Venus - the Earth's sister planet - passed in front of the Sun. This rare event - the last one occurred in 1882 - attracted the attention of millions of people all over the world. In a few days' time, on November 5-7, 2004, about 150 educators, media representatives, as well as amateur and professional astronomers will gather in Paris (France) at the international conference "The Venus Transit Experience" to discuss the outcome of the related Venus Transit 2004 (VT-2004) public education programme. This unique project was set up by the European Southern Observatory (ESO), together with the European Association for Astronomy Education (EAAE), the Institut de Mécanique Céleste et de Calcul des Éphémérides (IMCCE) and the Observatoire de Paris in France, as well as the Astronomical Institute of the Academy of Sciences of the Czech Republic. It was also supported by the European Commission in the framework of the European Science and Technology Week, cf. ESO PR 03/04. The VT-2004 programme successfully exposed the broad public to a number of fundamental issues at the crucial interface between society and basic science. It ensured the most comprehensive real-time coverage of the event via an extremely dynamic Central Display that was updated a short intervals. Thanks to the prior establishment of hundreds of mirror sites, the VT-2004 website was easily accessible all through the transit, even though it experienced about 55 million webhits during a period of 8 hours. The VT-2004 programme established a wide international network of individuals (including school teachers and their students, amateur astronomers, interested laypeople, etc.) and educational institutions (astronomical observatories, planetaria, science centres, etc.), as well as 25 National Nodes with their own websites about the Venus Transit in as many local languages. It collected a large number of photos and drawings. It also included an international Video Contest, inviting all interested parties to expose a theme around the transit, e.g., preparations for the event and the actual observations, as well as conveying the personal impressions. A professional jury has now selected among the many excellent entries the laureates (see the list below) who will present their videos at the Paris conference this week, competing for one of the top prizes, including a trip by the winning team to the ESO Paranal Observatory (Chile), home of the Very Large Telescope. The "Venus Transit Experience" Conference The Venus Transit Experience conference will take place at "Le Carré des Sciences" at the French Ministry of Research in Paris. It brings together the main participants in this project from many different European countries. A main aim is to discuss the impact of the project, identifying possible differences from country to country and showing how to share good practices in the future. The VT-2004 programme provided an exciting field test for the execution of large-scale public activities relating to a particular, scientific event with strong operational constraints, including the requirement to act in real-time as this event progressed. Much valuable experience was gathered for future continent-wide activities involving the same mechanisms and carried out under similar conditions. Thus, the overall outcome of this unique public education project is clearly of very wide interest, not just in the field of astronomy. The Distance to the Sun Remeasured A central feature of the VT-2004 programme was the VT-2004 Observing Campaign, aimed at re-enacting the historical determination of the distance to the Sun (the "Astronomical Unit") by collecting timings of the four contacts made by participating observers and combining them in a calculation of the AU. A large number of groups of observers registered; at the end, there were 2763 all over the world. Among these were almost 1000 school classes, demonstrating the large interest among students and teachers to participate actively in this unique celestial event. As exp

2004-11-01

163

Venus gravity - A harmonic analysis  

Science.gov (United States)

An improved model of Venusian global gravity has been obtained by fitting an eighteenth-degree and eighteenth-order spherical harmonic series to 78 orbital arcs of high altitude (950-1350 km at periapsis) tracking data and 351 orbital arcs of lower-altitude (150-200 km at periapsis) data from the Pioneer Venus Orbiter (PVO). Compared to a recently published tenth-degree model of Mottinger et al. (1985), which is based on the 78 high-altitude arcs only, the current model provides a significant improvement in resolution and fidelity. As a measure of this improvement, it is noted that for the low-altitude arcs alone, the variance of the residuals for the present model is reduced to 19 percent of the data variance, compared to 51 percent for the tenth-degree model. Venus differs significantly from the earth in that it exhibits a significant correlation between long-wavelength topography and gravity. The gravity/topography spectral admittances are inconsistent with either Airy or Pratt isostasy, but are consistent with dynamic support by mantle convection.

Bills, Bruce G.; Jones, Robert L.; Kiefer, Walter S.

1987-01-01

164

In-situ magnetic field observations of co-rotating interaction regions and coronal mass ejections at Venus  

Science.gov (United States)

Previous work by Whittaker et. al. combined remote sensing observations from Interplanetary Scintillation observations (IPS) with in-situ ion data collected by the Ion Mass Analyser (IMA) onboard Venus Express to study solar wind interactions with Venus. In-situ magnetic field observations from the Venus Express magnetometer will now be applied as a complimentary tool in identifying different cases of these interactions. Three case studies are undertaken; a co-rotating interaction region (CIR) arriving on ~30th April 2007, a coronal mass ejection (CME), arriving on ~25th and 26th May 2007 and mass loading of the solar wind coinciding with Venus moving into the tail disconnection event of comet 2P/Encke on ~22nd April 2007.We are interested both in making in situ measurements of heliospheric structures previously remote sensed by IPS, and also in understanding the response of the Venus magnetosphere to their passage. Ref: I.C. Whittaker, G.D. Dorrian, A. Breen, M. Grande. In-Situ observations of a co-rotating interaction region at Venus identified by IPS and STEREO ( submitted to Solar Physics topical issue: Remote sensing of the heliosphere 2009)

Guymer, G.; Whittaker, I.; Grande, M.; Barabash, S.; Zhang, T. L.

2010-05-01

165

Dielectric surface properties of Venus  

Science.gov (United States)

It has been known for over a decade that certain high-altitude regions on Venus exhibit bizarre radar-scattering and radiothermal-emission behavior. For example, observed values for normal-incidence power reflection coefficients in these areas can exceed 0.5; enhanced back scatter in some mountainous areas in the Magellan SAR images creates a bright surface with the appearance of snow; and reduced thermal emission in the anomalous areas makes the surface there appear hundreds of degrees cooler than the corresponding physical surface temperatures. The inferred radio emissivity in several of these regions falls to 0.3 for horizontal linear polarization at viewing angles in the range 20 deg - 40 deg. Several explanations have been offered for these linked phenomena. One involves single-surface reflection from a sharp discontinuity separating two media that have extremely disparate values of electromagnetic propagation. The mismatch may occur in either or both the real (associated with propagation velocity) or imaginary (associated with absorption) components of the relevant indices of refraction, and the discontinuity must take place over a distance appreciably shorter than a wavelength. An example of such an interaction of Earth would occur at the surface of a body of water. At radio wavelengths, water has an index of refraction of 9 (dielectric permittivity of about 80), and an associated loss factor that varies strongly with the amount of dissolved salts, but is generally significant. Its single-surface radar reflectivity at normal incidence is about 0.65, and the corresponding emissivity (viewed at the same angle) is therefore 0.35. Both these values are similar to the extremes found on Venus, but in the absence of liquid water, the process on Venus requires a different explanation. Two of the present authors (Pettengill and Ford) have suggested that scattering from a single surface possessing a very high effective dielectric permittivity could explain many of the unusual characteristics displayed by the Venus surface. A second explantion relates to the volume scattering that results from successive interactions with one or more interfaces interior to the planetary surface. If the near-surface material has a moderately low index of refraction (to ensure that a substantial fraction of the radiation incident from outside is not reflected, but rather penetrates into the surface), and a very low internal propagation loss, successive internal reflections can eventually redirect much of the energy back through the surface toward the viewer. The necessary conditions for this process to be effective are a low internal propagation loss coupled with efficient internal reflection. At sufficiently low temperatures, fractured water ice displays both the necessary low loss and near-total internal reflection. The possibility that this mechanism might be acting on Venus has recently been put forward.

Pettengill, G. H.; Wilt, R. J.; Ford, P. G.

1992-01-01

166

Preliminary results of the Pioneer Venus nephelometer experiment. [Venus clouds observations  

Science.gov (United States)

Preliminary results of the nephelometer experiments conducted aboard the large sounder, day, north, and night probes of the Pioneer Venus mission are presented. The vertical structures of the Venus clouds observed simultaneously at each of the four locations from altitudes of from 63 kilometers to the surface are compared, and similarities and differences are noted. Tentative results from attempting to use the data from the nephelometer and cloud particle size spectrometer on the sounder probe to identify the indices of refraction of cloud particles in various regions of the Venus clouds are reported. Finally the nephelometer readings for the day probe during impact on the surface of Venus are presented.

Ragent, B.; Blamont, J.

1979-01-01

167

On the Decadal Variation of Sulphur Dioxide at the Cloud Top of Venus  

Science.gov (United States)

Venus atmosphere is a natural laboratory of sulphur chemistry. As one of the parent species of sulphur, sulphur dioxide (SO2) is generated in the lower atmosphere and transported upward to the middle atmosphere, where it is further oxidized and eventually produces sulphuric acid cloud. The 30-year observations from the Pioneer Venus (Esposito et al., 1988) to the Venus Express (Marcq et al., 2012) show a decadal variation of total column abundance of SO2 above the cloud top. The amplitude varies in orders of magnitude and therefore poses a question on what causes such a dramatic change on the sulphur budget. Previous interpretations include episodic volcanic eruption (Esposito 1984) and longtime dynamical oscillation (Marcq et al., 2012) that is supported by a recent general circulation model on Venus (Parish et al., 2011), but no chemical modelling work has yet investigated those mechanisms. Here I use a time-evolving photochemistry-diffusion model (Zhang et al., 2010;2012) to understand the decadal variation. Specifically for this study, I perturb the mean steady state of the middle atmosphere of Venus by adding forcing in the upper cloud layer (58-70 km). Important parameters such as the amplitude and timescale of the forcing are constrained by the observed secular patterns. Possible consequences are discussed and the variations for other species are predicted to guide the future observations.

Zhang, X.

2014-04-01

168

Novel Architecture for a Long-Life, Lightweight Venus Lander  

Science.gov (United States)

This paper describes a novel concept for an extended lifetime, lightweight Venus lander. Historically, to operate in the 480° C, 90 atm, corrosive, mostly CO2 Venus surface environment, previous landers have relied on thick Ti spherical outer shells and thick layers of internal insulation. But even the most resilient of these landers operated for only about 2 hours before succumbing to the environment. The goal on this project is to develop an architecture that extends lander lifetime to 20-25 hours and also reduces mass compared to the Pioneer Venus mission architecture. The idea for reducing mass is to: (a) contain the science instruments within a spherical high strength lightweight polymer matrix composite (PMC) tank; (b) surround the PMC tank with an annular shell of high performance insulation pre-pressurized to a level that (after landing) will exceed the external Venus surface pressure; and (c) surround the insulation with a thin Ti outer shell that contains only a net internal pressure, eliminating buckling overdesign mass. The combination of the PMC inner tank and thin Ti outer shell is lighter than a single thick Ti outer shell. The idea for extending lifetime is to add the following three features: (i) an expendable water supply that is placed within the insulation or is contained in an additional vessel within the PMC tank; (ii) a thin spherical evaporator shell placed within the insulation a short radial distance from the outer shell; and (iii) a thin heat-intercepting liquid cooled shield placed inboard of the evaporator shell. These features lower the temperature of the insulation below what it would have been with the insulation alone, reducing the internal heat leak and lengthening lifetime. The use of phase change materials (PCMs) inside the PMC tank is also analyzed as a lifetime-extending design option. The paper describes: (1) analytical modeling to demonstrate reduced mass and extended life; (2) thermal conductivity testing of high performance insulation as a function of temperature and pressure; (3) a bench-top ambient pressure thermal test of the evaporation system; and (4) a higher fidelity test, to be conducted in a high pressure, high temperature inert gas test chamber, of a small-scale Venus lander prototype (made from two hemispherical interconnecting halves) that includes all of the aforesaid features. 22 CFR 125.4(b)(13) applicable

Bugby, D.; Seghi, S.; Kroliczek, E.; Pauken, M.

2009-03-01

169

Near-infrared Ground-based Observations Of Venus: Technique And Observations Of H2O Variations In The Lower Atmosphere.  

Science.gov (United States)

Ground-based spatially resolved near-infrared spectroscopic observations of the Venusian night-side have been obtained prior or post inferior conjunctions in September 2002, July 2004 and December 2005. Observations have been made using IRIS2 on the Anglo-Australian Telescope and CASPIR on the 2.3m ANU Telescope. We are analysing this data to obtain temporal variations, gradients and spatial distributions of H2O in the Venusian lower atmosphere. Thermal emission can be observed through near infrared atmospheric windows discovered in 1984. Windows at 1.74 µm and 2.3 µm probe just below the base of the clouds, whereas near infrared windows short-ward of 1.31 µm show radiation from the lowest 25 km of the atmosphere with an increasing fraction of the emission originating from the surface. Images obtained at 1.31 µm are dominated by contrasts due to cloud opacities and these contrasts are present at similar strengths in images obtained at 1.18 µm. However at the shorter wavelength, contrasts due to surface features are stronger. By ratioing these images, features corresponding to the overlying clouds can be removed, revealing the surface topography of Venus (Meadows, PhD thesis, 1994). By using water vapour absorption lines in the 1.18 µm atmospheric window and comparing paths over topography of different heights it is possible to study the water vapour content of the lower atmosphere (Meadows and Crisp 1996). New instruments such as IRIS2 have provided a substantial improvement in the spectral and spatial resolutions that can be used for such studies. The European Space Agency Venus Express mission has based much of their science on the infrared techniques discussed. Our long term ground-based data on the properties of the Venusian near surface environment will help to provide a scientific context for the Venus Express results.

Chamberlain, Sarah; Bailey, J. A.; Meadows, V. S.; Simpson, A.; Crisp, D.

2006-09-01

170

Energetic Neutral Atom Emissions From Venus: VEX Observations and Theoretical Modeling  

Science.gov (United States)

Venus has almost no intrinsic magnetic field to shield itself from its surrounding environment. The solar wind thus directly interacts with the planetary ionosphere and atmosphere. One of the by-products of this close encounter is the production of energetic neutral atom (ENA) emissions. Theoretical studies have shown that significant amount of ENAs are emanated from the planet. The launch of the Venus Express (VEX) in 2005 provided the first light ever of the Venus ENA emissions. The observed ENA flux level and structure are in pretty good agreement with the theoretical studies. In this paper, we present VEX ENA data and the comparison with numerical simulations. We seek to understand the solar wind interaction with the planet and the impacts on its atmospheres.

Fok, M.-C.; Galli, A.; Tanaka, T.; Moore, T. E.; Wurz, P.; Holmstrom, M.

2007-01-01

171

High Temperature, Wireless Seismometer Sensor for Venus  

Science.gov (United States)

Space agency mission plans state the need to measure the seismic activity on Venus. Because of the high temperature on Venus (462? C average surface temperature) and the difficulty in placing and wiring multiple sensors using robots, a high temperature, wireless sensor using a wide bandgap semiconductor is an attractive option. This paper presents the description and proof of concept measurements of a high temperature, wireless seismometer sensor for Venus. A variation in inductance of a coil caused by the movement of an aluminum probe held in the coil and attached to a balanced leaf-spring seismometer causes a variation of 700 Hz in the transmitted signal from the oscillator/sensor system at 426? C. This result indicates that the concept may be used on Venus.

Ponchak, George E.; Scardelletti, Maximilian C.; Taylor, Brandt; Beard, Steve; Meredith, Roger D.; Beheim, Glenn M.; Hunter Gary W.; Kiefer, Walter S.

2012-01-01

172

Heart Attack Difference: Mars and Venus  

Science.gov (United States)

... Body Basics ACEP in Social Media Body Basics Heart Attack Difference: Mars and Venus You probably know that ... may not know is, when it comes to heart attacks, the common symptoms for men and women are ...

173

The development of studies of Venus  

Science.gov (United States)

An historical account is given of the major figures, observational techniques and theories involved in Venus studies prior to space probe-based researches. Those who followed Galileo Galilei (1610) with the simple telescopes of the 17th and early 18th centuries confirmed the phases of the illuminated face of Venus. Lomonosov (1761) noted a gray halo surrounding the planet as it was partially silhouetted against the sun, and correctly inferred that Venus has an atmosphere. The brightness and nearly featureless appearance of the planet, together with the halo effect, led to the early conclusion that the atmosphere is cloudy. While visual and photographic spectroscopy had been applied to Venus many times, the first indication of spectral features different from the solar spectrum was found in 1932 with the high dispersion spectrograph on the Mt. Wilson 2.5-m telescope.

Cruikshank, D. P.

1983-01-01

174

Tremolite Decomposition and Water on Venus  

Science.gov (United States)

We present experimental data showing that the decomposition rate of tremolite, a hydrous mineral, is sufficiently slow that it can survive thermal decomposition on Venus over geologic timescales at current and higher surface temperatures.

Johnson, N. M.; Fegley, B., Jr.

2000-01-01

175

Remote sensing of planetary atmospheres: Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

More than any other planet except the Earth, Venus has been the subject of a variety of remote sensing investigations over a wide range of wavelengths. Since Venus has complete cloud cover, with a complex composition and layering, the retrieval of the information from these measurements is particularly challenging. The problem is further complicated by the high temperatures and pressures found in the deep atmosphere, resulting in a novel and interesting radiative transfer problem even before ...

Taylor, Fw

1998-01-01

176

Venus: detailed mapping of maxwell montes region.  

Science.gov (United States)

From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled. PMID:17839563

Alexandrov, Y N; Crymov, A A; Kotelnikov, V A; Petrov, G M; Rzhiga, O N; Sidorenko, A I; Sinilo, V P; Zakharov, A I; Akim, E L; Basilevski, A T; Kadnichanski, S A; Tjuflin, Y S

1986-03-14

177

A dynamic model of Venus's gravity field  

Science.gov (United States)

Unlike Earth, long wavelength gravity anomalies and topography correlate well on Venus. Venus's admittance curve from spherical harmonic degree 2 to 18 is inconsistent with either Airy or Pratt isostasy, but is consistent with dynamic support from mantle convection. A model using whole mantle flow and a high viscosity near surface layer overlying a constant viscosity mantle reproduces this admittance curve. On Earth, the effective viscosity deduced from geoid modeling increases by a factor of 300 from the asthenosphere to the lower mantle. These viscosity estimates may be biased by the neglect of lateral variations in mantle viscosity associated with hot plumes and cold subducted slabs. The different effective viscosity profiles for Earth and Venus may reflect their convective styles, with tectonism and mantle heat transport dominated by hot plumes on Venus and by subducted slabs on Earth. Convection at degree 2 appears much stronger on Earth than on Venus. A degree 2 convective structure may be unstable on Venus, but may have been stabilized on Earth by the insulating effects of the Pangean supercontinental assemblage.

Kiefer, W. S.; Richards, M. A.; Hager, B. H.; Bills, B. G.

1984-01-01

178

A dynamic model of Venus's gravity field  

Science.gov (United States)

Unlike Earth, long wavelength gravity anomalies and topography correlate well on Venus. Venus's admittance curve from spherical harmonic degree 2 to 18 is inconsistent with either Airy or Pratt isostasy, but is consistent with dynamic support from mantle convection. A model using whole mantle flow and a high viscosity near surface layer overlying a constant viscosity mantle reproduces this admittance curve. On Earth, the effective viscosity deduced from geoid modeling increases by a factor of 300 from the asthenosphere to the lower mantle. These viscosity estimates may be biased by the neglect of lateral variations in mantle viscosity associated with hot plumes and cold subducted slabs. The different effective viscosity profiles for Earth and Venus may reflect their convective styles, with tectonism and mantle heat transport dominated by hot plumes on Venus and by subducted slabs on Earth. Convection at degree 2 appears much stronger on Earth than on Venus. A degree 2 convective structure may be unstable on Venus, but may have been stabilized on Earth by the insulating effects of the Pangean supercontinental assemblage.

Kiefer, W. S.; Richards, M. A.; Hager, B. H.; Bills, B. G.

1986-01-01

179

Dynamic model of Venus's gravity field  

International Nuclear Information System (INIS)

Unlike Earth, long wavelength gravity anomalies and topography correlate well on Venus. Venus's admittance curve from spherical harmonic degree 2 to 18 is inconsistent with either Airy or Pratt isostasy, but is consistent with dynamic support from mantle convection. A model using whole mantle flow and a high viscosity near surface layer overlying a constant viscosity mantle reproduces this admittance curve. On Earth, the effective viscosity deduced from geoid modeling increases by a factor of 300 from the asthenosphere to the lower mantle. These viscosity estimates may be biased by the neglect of lateral variations in mantle viscosity associated with hot plumes and cold subducted slabs. The different effective viscosity profiles for Earth and Venus may reflect their convective styles, with tectonism and mantle heat transport dominated by hot plumes on Venus and by subducted slabs on Earth. Convection at degree 2 appears much stronger on Earth than on Venus. A degree 2 convective structure may be unstable on Venus, but may have been stabilized on Earth by the insulating effects of the Pangean supercontinental assemblage

180

The Mars Express Orbiter Radio Science Experiment (MaRS)  

Science.gov (United States)

The Mars Express Orbiter Radio Science experiment (MaRS) will employ radio occultation (i) to sound the neutral Martian atmosphere to derive vertical density, pressure and temperature profiles as a function of height to better than 100 meter), and (ii) the ionosphere to derive vertical ionospheric electron density profiles and a description of the Martian ionosphere through its diurnal and seasonal variations depending also on solar wind conditions, (iii) to determine the dielectric and scattering properties of the Martian surface in specific target areas by a bistatic radar experiment, (iv) to determine gravity anomalies for the investigation of the structure and evolution of the Martian crust and lithosphere in conjunction with observations of the High Resolution Stereo Camera (HRSC) as a base for three dimensional (3D) topography, and (v) to sound the solar corona during the superior conjunction of the planet Mars with the Sun. The radio carrier links of the spacecraft Telemetry, Tracking and Command (TTC) subsystem between the orbiter and the Earth will be used for these investigations. Simultaneous and coherent dual-frequency downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) via the High Gain Antenna (HGA) permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively. The investigation relies on the observation of the phase, amplitude, polarization and propagation times of radio signals transmitted from the spacecraft and received with ground station antennas on Earth. The radio signals are affected by the medium through which the signals propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and finally by the performance of the various systems involved both on the spacecraft and on ground.

Paetzold, M.

 
 
 
 
181

The Mars Express Radio Science Experiment (MaRS)  

Science.gov (United States)

The Mars Express Orbiter Radio Science experiment (MaRS) will employ radio occultation (i) to sound the neutral Martian atmosphere to derive vertical density, pressure and temperature profiles as a function of height to better than 100 meter, and (ii) sound the the ionosphere to derive vertical ionospheric electron density profiles and a description of the Martian ionosphere through its diurnal and seasonal variations depending also on solar wind conditions. MaRS will also (iii) determine the dielectric and scattering properties of the Martian surface in specific target areas by a bistatic radar experiment, (iv) determine gravity anomalies for the investigation of the structure and evolution of the Martian crust and lithosphere in conjunction with observations of the High Resolution Stereo Camera (HRSC) as a base for three dimensional (3D) topography, and (v) sound the solar corona during the superior conjunction of the planet Mars with the Sun. The radio carrier links of the spacecraft Telemetry, Tracking and Command (TT&C) subsystem between the orbiter and the Earth will be used for these investigations. Simultaneous and coherent dual-frequency downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) via the High Gain Antenna (HGA) permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively. The investigation relies on the observation of the phase, amplitude, polarization and propagation times of radio signals transmitted from the spacecraft and received with ground station antennas on Earth. The radio signals are affected by the medium through which the signals propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and finally by the performance of the various systems involved both on the spacecraft and on ground.

Pätzold, M.; Mars Team

2003-04-01

182

Geologic map of the Artemis Chasma quadrangle (V-48), Venus  

Science.gov (United States)

Artemis, named for the Greek goddess of the hunt, represents an approximately 2,600 km diameter circular feature on Venus, and it may represent the largest circular structure in our solar system. Artemis, which lies between the rugged highlands of Aphrodite Terra to the north and relatively smooth lowlands to the south, includes an interior topographic high surrounded by the 2,100-km-diameter, 25- to 200-km-wide, 1- to 2-km-deep circular trough, called Artemis Chasma, and an outer rise that grades outward into the surrounding lowland. Although several other chasmata exist in the area and globally, other chasmata have generally linear trends that lack the distinctive circular pattern of Artemis Chasma. The enigmatic nature of Artemis has perplexed researchers since Artemis Chasma was first identified in Pioneer Venus data. Although Venus' surface abounds with circular to quasi-circular features at a variety of scales, including from smallest to largest diameter features: small shield edifices (>1 km), large volcanic edifices (100-1,000 km), impact craters (1-270 km), coronae (60-1,010 km), volcanic rises and crustal plateaus (~1,500-2,500 km), Artemis defies classification into any of these groups. Artemis dwarfs Venus' largest impact crater, Mead (~280 km diameter); Artemis also lacks the basin topography, multiple ring structures, and central peak expected for large impact basins. Topographically, Artemis resembles some Venusian coronae; however Artemis is an order of magnitude larger than the average corona (200 km) and about twice the size of Heng-O Corona (which is 1,010 km in diameter), the largest of Venusian coronae. In map view Artemis' size and shape resemble volcanic rises and crustal plateaus; however, both of these classes of features differ topographically from Artemis. Volcanic rises and crustal plateaus form broad domical regions, and steep-sided regions with flat tops, respectively; furthermore, neither rises nor plateaus include circular troughs. So although it seems clear what Artemis is not, there is little consensus about what Artemis is, much less how Artemis formed. Debate during the past decade has resulted in the proposal of at least four hypotheses for Artemis' formation. The first (herein referred to as H1) is that Artemis Chasma represents a zone of northwest-directed convergence and subduction. The second hypothesis (herein referred to as H2) is that Artemis consists of a composite structure with a part of its interior region marking the exposure of deformed ductile deep-crustal rocks analogous to a terrestrial metamorphic core complex. The third (herein referred to as H3) is that Artemis reflects the surface expression of an ancient (>3.5 Ga) huge bolide impact event on cold strong lithosphere. The fourth hypothesis (herein referred to as H4) is that Artemis marks the surface expression of a deep mantle plume. Each of these hypotheses holds different implications for Venus geodynamics and evolution processes, and for terrestrial planet processes in general. Viability of H1 would provide support that terrestrial-like plate-tectonic processes once occurred on Earth's sister planet. The feasibility of H2 would require high values of crustal extension and therefore imply that significant horizontal displacements occurred on Venus-displacement that may or may not be related to terrestrial-like plate-tectonic processes. The possibility of H3 would suggest that Venus' surface is extremely old, and that Venus has experienced very little dynamic activity for the last 3.5 billion years or more; this would further imply that Venus is essentially tectonically dead, and has been for most of its history. This view contrasts strongly with studies that highlight a rich history of Venus including activity at least as young as 750 million years ago, and quite likely up to the present. If H4 has credibility, then Artemis could provide clues to cooling mechanisms of Earth's sister planet. Each of these hypotheses

Bannister, Roger A.; Hansen, Vicki L.

2010-01-01

183

Atmosphere/mantle coupling and feedbacks on Venus  

Science.gov (United States)

investigate the coupled evolution of the atmosphere and mantle on Venus. Here we focus on mechanisms that deplete or replenish the atmosphere: atmospheric escape to space and volcanic degassing of the mantle. These processes are linked to obtain a coupled model of mantle convection and atmospheric evolution, including feedback of the atmosphere on the mantle via the surface temperature. During early atmospheric evolution, hydrodynamic escape is dominant, while for later evolution we focus on nonthermal escape, as observed by the Analyzer of Space Plasma and Energetic Atoms instrument on the Venus Express Mission. The atmosphere is replenished by volcanic degassing from the mantle, using mantle convection simulations based on those of Armann and Tackley [2012], and include episodic lithospheric overturn. The evolving surface temperature is calculated from the amount of CO2 and water in the atmosphere using a gray radiative-convective atmosphere model. This surface temperature in turn acts as a boundary condition for the mantle convection model. We obtain a Venus-like behavior (episodic lid) for the solid planet and an atmospheric evolution leading to the present conditions. CO2 pressure is unlikely to vary much over the history of the planet, with only a 0.25-20% postmagma-ocean buildup. In contrast, atmospheric water vapor pressure is strongly sensitive to volcanic activity, leading to variations in surface temperatures of up to 200 K, which have an effect on volcanic activity and mantle convection. Low surface temperatures trigger a mobile lid regime that stops once surface temperatures rise again, making way to stagnant lid convection that insulates the mantle.

Gillmann, Cedric; Tackley, Paul

2014-06-01

184

Aerial electromagnetic sounding of the lithosphere of Venus  

Science.gov (United States)

Electromagnetic (EM) investigation depths are larger on Venus than Earth due to the dearth of water in rocks, in spite of higher temperatures. Whistlers detected by Venus Express proved that lightning is present, so the Schumann resonances ˜10-40 Hz may provide a global source of electromagnetic energy that penetrates ˜10-100 km. Electrical conductivity will be sensitive at these depths to temperature structure and hence thermal lithospheric thickness. Using 1D analytic and 2D numerical models, we demonstrate that the Schumann resonances—transverse EM waves in the ground-ionosphere waveguide—remain sensitive at all altitudes to the properties of the boundaries. This is in marked contrast to other EM methods in which sensitivity to the ground falls off sharply with altitude. We develop a 1D analytical model for aerial EM sounding that treats the electrical properties of the subsurface (thermal gradient, water content, and presence of conductive crust) and ionosphere, and the effects of both random errors and biases that can influence the measurements. We initially consider specified 1D lithospheric thicknesses 100-500 km, but we turn to 2D convection models with Newtonian temperature-dependent viscosity to provide representative vertical and lateral temperature variations. We invert for the conductivity-depth structure and then temperature gradient. For a dry Venus, we find that the error on temperature gradient obtained from any single local measurement is ˜100%—perhaps enough to distinguish "thick" vs. "thin" lithospheres. When averaging over thousands of kilometers, however, the standard deviation of the recovered thermal gradient is within the natural variability of the convection models, temperature-sensitive structure is screened, but the "wet" nature of the upper mantle, as well as structure of the upper crust, is revealed.

Grimm, Robert E.; Barr, Amy C.; Harrison, Keith P.; Stillman, David E.; Neal, Kerry L.; Vincent, Michael A.; Delory, Gregory T.

2012-02-01

185

Deformation Sequence, Bereghinya Planitia, Venus  

Science.gov (United States)

The plains region Bereghinya Planitia lies north of central Eistla Regio in the Bereghinya Planitia (V-8) and Sappho Patera (V-20) quadrangles, and is bounded approximately by 15 and 50 degrees north, 0 and 30 degrees east. Most of this area is underlain by plains of presumably volcanic origin ("regional plains") with no apparent sources, but significant plains areas are surfaced by flows derived from coronae, central volcanoes, long lava channels, and clusters of small edifices ("shield fields"). Many areas of Venus have similar appearing, but not necessarily coeval, regional plains. A number of outstanding issues of Venus crustal history involve the ages of structures and other units relative to the regional plains - the regional plains commonly are used as a chronologic marker even though they clearly formed over a finite period of time of unknown length, both in years and relative to the ages of other materials. Older than regional plains in Bereghinya Planitia are scattered inliers of radar bright materials and materials of a ridge belt. Structures affecting regional plains include early extensional lineaments, graben swarms, wrinkle ridges, ridges of a ridge belt, belts of closely spaced wrinkle ridges connecting coronae, and ridges and fractures defining coronae. The wrinkle ridges reflect progressive deformation because they occur on almost all units, but with abundances that are proportional to unit ages. Post regional plains strain patterns evolved from areally extensive east-west extension and north-south contraction to an almost chaotic pattern of much more local orientations. The emplacement of volcanic units is interleaved with the deformation history; flows from coronae are mostly, but not entirely, the same age or younger than regional plains, flows from shield fields are mostly, but not entirely, younger than regional plains and younger than corona structures, and flows from large lava channels are younger than regional plains. All 28 impact craters are younger than regional plains and almost all are younger than wrinkle ridges. These relationships imply a relatively fast structural and volcanic evolution following emplacement of regional plains. The crustal history of Bereghinya Planitia reflects a complex of processes that overlapped in time and space, and thus this history cannot easily be fit into a simple evolutionary scheme.

McGill, G. E.

2001-12-01

186

Understanding Venus to understand the Earth  

Science.gov (United States)

Despite having almost the same size and bulk composition as the Earth, Venus possesses an extreme climate with a surface pressure of 90 bars and temperatures of 740 K. At visible wavelengths the Venus disk appears covered by thick clouds.The core atmospheric processes of Venus and the Earth are similar, despite the different, extraordinary paths they took since their simultaneous formation in the solar system's habitable zone. There are several indications that the composition of the Venus atmosphere has undergone large changes, such as an early runaway climate, and it is likely that the planet has lost a large amount of water through dissociation in the upper atmosphere due to ultraviolet radiation and the subsequent escape of hydrogen. SO2 is thought to originate from volcanism. H2O and SO2 react to form H2SO4 which condenses to form clouds. In past centuries, astronomers and explorers including Captain James Cook observed transits to measure the scale of the solar system. On 5-6 June 2012 we observed the last transit of Venus in this century. Close to the ingress and egress phases, the fraction of Venus disk outside the solar photosphere appears outlined by a thin arc of light, called the aureole. We have shown that the deviation due to refraction and the luminosity of the aureole are related to the local density scale height and the altitude of the refraction layer. As different portions of the arc can yield different values of these parameters, the rare transit event thus provides a unique insight of the Venus mesosphere. The polar region, significantly brighter in initial phases due to larger scale height of the polar mesosphere, appears consistently offset toward morning terminator by about 15deg. latitude, peaking at 75N at 6:00 local time. This result reflects local latitudinal structure in the polar mesosphere, either in temperature or aerosol altitude distribution. Detailed comparative climatology of Venus, an Earth-size planet and understanding why it evolved so differently in its history is crucial to assert the long term evolution of our own planet. Exploring Venus' atmosphere also helps characterize the variety of Earth-size planets near their habitable zone to be discovered around other stars.he atmospheric arc, or aureole, seen from the DST/Interferometric BIdimensional Spectrometer (IBIS) at ~8.5 minutes prior to first contact (NSO/Arcetri)

Widemann, T.; Tanga, P.

2012-12-01

187

Change over a service learning experience in science undergraduates' beliefs expressed about elementary school students' ability to learn science  

Science.gov (United States)

This longitudinal investigation explores the change in four (3 female, 1 male) science undergraduates' beliefs expressed about low-income elementary school students' ability to learn science. The study sought to identify how the undergraduates in year-long public school science-teaching partnerships perceived the social, cultural, and economic factors affecting student learning. Previous service-learning research infrequently focused on science undergraduates relative to science and society or detailed expressions of their beliefs and field practices over the experience. Qualitative methodology was used to guide the implementation and analysis of this study. A sample of an additional 20 science undergraduates likewise involved in intensive reflection in the service learning in science teaching (SLST) course called Elementary Science Education Partners (ESEP) was used to examine the typicality of the case participants. The findings show two major changes in science undergraduates' belief expressions: (1) a reduction in statements of beliefs from a deficit thinking perspective about the elementary school students' ability to learn science, and (2) a shift in the attribution of students, underlying problems in science learning from individual-oriented to systemic-oriented influences. Additional findings reveal that the science undergraduates perceived they had personally and profoundly changed as a result of the SLST experience. Changes include: (1) the gain of a new understanding of others' situations different from their own; (2) the realization of and appreciation for their relative positions of privilege due to their educational background and family support; (3) the gain in ability to communicate, teach, and work with others; (4) the idea that they were more socially and culturally connected to their community outside the university and their college classrooms; and (5) a broadening of the way they understood or thought about science. Women participants stated that the experience validated their science and science-related career choices. Results imply that these changes have the potential to strengthen the undergraduate pursuit of science-related careers and will contribute positive influences to our education system and society at large.

Goebel, Camille A.

188

Remote Raman - LIBS Geochemical Investigation under Venus Atmospheric Conditions  

Science.gov (United States)

The extreme Venus surface temperature (740K) and atmospheric pressure (93 atm) creates a challenging environment for future lander missions. The scientific investigations capable of Venus geochemical observations must be completed within several hours of the landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Raman and LIBS are highly complementary analytical techniques where Raman spectroscopy is used to determine the sample molecular structure and LIBS is employed to quantitatively determine the elemental composition. Wiens et al. (2005) and Sharma et al. (2006) demonstrated that one can integrate both analytical techniques into a single instrument capable of planetary missions. Here, we will present data that demonstrates the utility of both Raman spectroscopy and LIBS under Venus conditions using separate instruments. All of the samples in these experiments were placed in a pressure vessel containing 93 atm of CO2 at 150°C and the vessel was placed 1.6m from the telescope. The elemental analysis was completed with a dual pulsed (DP) LIBS instrument employing two Nd:YAG lasers operating at 1064nm. These lasers were focused onto the sample surface and the emission was collected with a Catalina Scientific Echelle Spectrometer connected to an intensified charge coupled device (ICCD). These experiments involved probing several rock powder standards and minerals. The LIBS elemental analysis involved generating a partial least squares (PLS) model with the rock powder standards to quantitatively determine the major elemental abundance. The Raman spectra of minerals were collected up to 970 K at 9 m with a frequency doubled Nd:YAG laser operating at 532nm and the backscattered light was collected with a transmission spectrometer connected to another ICCD with 2 ?s gate during daytime. A comparison of Raman spectra of gypsum (CaSO4.2H2O), dolomite (CaMg(CO3))2), olivine (Mg2Fe2-xSiO4) as a function of temperature shows that the Raman lines remains sharp and well defined even in the high temperature spectra. These time-resolved Raman measurements show that high temperature of minerals will not be a limitation and remote Raman spectroscopy would be a potential tool for rapidly exploring Venus surface mineralogy and surface processes.

Clegg, S. M.; Barefield, J. E.; Wiens, R. C.; Misra, A. K.; Sharma, S. K.

2008-12-01

189

Venus - Sag Caldera 'Sachs Patera  

Science.gov (United States)

This image of Sachs Patera on Venus is centered at 49 degrees north, 334 degrees east. Defined as a sag-caldera, Sachs is an elliptical depression 130 meters (81 feet) in depth, spanning 40 kilometers (25 miles) in width along its longest axis. The morphology implies that a chamber of molten material drained and collapsed, forming a depression surrounded by concentric scarps spaced 2-to-5 kilometers (1.2- to-3 miles) apart. The arc-shaped set of scarps, extending out to the north from the prominent ellipse, is evidence for a separate episode of withdrawal; the small lobe-shaped extension to the southwest may represent an additional event. Solidified lava flows 10-to-25 kilometers (6-to-16 miles) long, give the caldera its flower-like appearance. The flows are a lighter tone of gray in the radar data because the lava is blockier in texture and consequently returns more radar waves. Much of the lava, which was evacuated from the chamber, probably traveled to other locations underground, while some of it may have surfaced further south. This is unlike calderas on Earth, where a rim of lava builds up in the immediate vicinity of the caldera.

1991-01-01

190

VENUS superconducting thin solenoid magnet  

International Nuclear Information System (INIS)

The VENUS solenoid magnet was constructed, and tested successfully at KEK on February 1986. The magnet has a warm bore diameter of 3.4 m, an outer diameter of the cryostat of 3.8 m, and a total length of the cryostat of 5.6 m. It is the largest one at present of several thin solenoid magnets for colliding beam detectors, and furthermore it has a very short radiation thickness of 0.52. For the purpose of better cooling, Kapton insulators between the coil-case and the winding were cured under expansion pressure, and the helium shield of 2 mm thick aluminum cylinder was set up inside the coll. The conductor jointing method without extra space in the winding was invented to obtain a uniform magnetic field distribution, and an aluminum stabilized NbTi-Cu conductor of 10 km unit length was fabricated. The magnet was first cooled and excited to 2000 A without an iron yoke at the factory. It was assembled with the iron yoke at KEK, and cooled to 4.6 K in 14 days. The first excitation to the rated current of 3978 A was performed without quench. The magnetic field was 0.75 T. Several forced quench tests were made to investigate the stability of the magnet and to check the safety of operation

191

High-resolution gravity model of Venus  

Science.gov (United States)

The anomalous gravity field of Venus shows high correlation with surface features revealed by radar. We extract gravity models from the Doppler tracking data from the Pioneer Venus Orbiter by means of a two-step process. In the first step, we solve the nonlinear spacecraft state estimation problem using a Kalman filter-smoother. The Kalman filter has been evaluated through simulations. This evaluation and some unusual features of the filter are discussed. In the second step, we perform a geophysical inversion using a linear Bayesian estimator. To allow an unbiased comparison between gravity and topography, we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps. The maps presented cover 2/3 of the surface of Venus and display the strong topography-gravity correlation previously reported. The topography-gravity scatter plots show two distinct trends.

Reasenberg, R. D.; Goldberg, Z. M.

1992-01-01

192

Sapphire Viewports for a Venus Probe  

Science.gov (United States)

A document discusses the creation of a viewport suitable for use on the surface of Venus. These viewports are rated for 500 C and 100 atm pressure with appropriate safety factors and reliability required for incorporation into a Venus Lander. Sapphire windows should easily withstand the chemical, pressure, and temperatures of the Venus surface. Novel fixture designs and seals appropriate to the environment are incorporated, as are materials compatible with exploration vessels. A test cell was fabricated, tested, and leak rate measured. The window features polish specification of the sides and corners, soft metal padding of the sapphire, and a metal C-ring seal. The system safety factor is greater than 2, and standard mechanical design theory was used to size the window, flange, and attachment bolts using available material property data. Maintenance involves simple cleaning of the window aperture surfaces. The only weakness of the system is its moderate rather than low leak rate for vacuum applications.

Bates, Stephen

2012-01-01

193

Venus project : experimentation at ENEA`s pilot site  

Energy Technology Data Exchange (ETDEWEB)

The document describes the ENEA`s (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III ). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry databases. VENUS interfaces to ENEA`s databases: cometa materials Module, Cometa Laboratories Module and European Programs. This report contents the results of the experimentation and of the validation carried out in ENEA`s related to the Venus generations. Moreover, the description of the architecture, the user requirements syntesis and the validation methodology of the VENUS systems have been included.

Bargellini, M.L.; Fontana, F. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dip. Innovazione; Bucci, C.; Ferrara, F.; Sottile, P.A. [GESI s.r.l., Rome (Italy); Niccolai, L.; Scavino, G. [Rome Univ. Sacro Cuore (Italy); Mancini, R.; Levialdi, S. [Rome Univ. La Sapienza (Italy). Dip. di Scienze dell`Informazione

1996-12-01

194

Isostatic compensation of equatorial highlands on Venus  

Science.gov (United States)

Spherical harmonic models for Venus' global topography and gravity incorporating Magellan data are used to test isostatic compensation models in five 30 deg x 30 deg regions representative of the main classes of equatorial highlands. The power spectral density for the harmonic models obeys a power-law scaling with spectral slope Beta approximately 2 (Brown noise) for the topography and Beta approximately 3 (Kaula's law) for the geoid, similar to what is observed for Earth. The Venus topography spectrum has lower amplitudes than Earth's which reflects the dominant lowland topography on Venus. Observed degree geoid to topography ratios (GTRs) on Venus are significantly smaller than degree GTRs for uncompensated topography, indicative of substantial compensation. Assuming a global Airy compensation, most of the topography is compensated at depths greater than 100 km, suggesting a thick lithosphere on Venus. For each region considered we obtain a regional degree of compensation C from a linear regression of Bouguer anomaly versus Bouguer gravity data. Geoid anomaly (N) versus topography variation (h) data for each sample were compared, in the least-squares sense, to theoretical correlations for Pratt, Airy, and thermal thinning isostasy models yielding regional GTR, zero-elevation crustal thickness (H), and zero elevation thermal lithosphere thickness (y(sub L(sub 0)), respectively. We find the regional compensation to be substantial (C approximately 52-80%), and the h, N data correlations in the chosen areas can be explained by isostasy models applicable on the Earth and involving variations in crustal thickness (Airy) and/or lithospheric (thermal thinning) thickness. However, a thick crust and lithosphere (y(sub L(sub 0)) approximately 300 km) must be assumed for Venus.

Kucinskas, Algis B.; Turcotte, Donald L.

1994-01-01

195

Convection-driven tectonics on Venus  

Science.gov (United States)

An analysis is presented of convective stress coupling to an elastic lithosphere as applied to Venus. Theoretical solutions are introduced for the response of a mathematically thick elastic plate overlying a Newtonian viscous medium with an exponential depth dependence of viscosity, and a Green's function solution is obtained for the viscous flow driven by a harmonic density distribution at a specified depth. An elastic-plastic analysis is carried out for the deformation of a model Venus lithosphere. The results predict that dynamic uplift of Venusian topography must be accompanied by extensive brittle failure and viscous flow in the lithosphere.

Phillips, R. J.

1990-02-01

196

The Tectonics and Evolution of Venus  

Science.gov (United States)

This shift corresponded to a focusing of research on Venus. Some work included comparison with other planets. Venus research is being continued. The research can be summarized under five headings: (1) Planet formation; (2) Thermal and Compositional Evolution; (3) Tectonic structures and processes; (4) Determination and interpretation of gravity; and (5) Analyses of Ishtar Terra. Thirty-four publications were produced. References to publications supporting the summary are by year and letter: e.g., (1990 c,d) for the emphasis on the terminal phases in formation studies.

Kaula, William M.

1997-01-01

197

Venus: Mantle convection, hotspots, and tectonics  

International Nuclear Information System (INIS)

The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined

198

Secreted major Venus flytrap chitinase enables digestion of Arthropod prey  

DEFF Research Database (Denmark)

Predation plays a major role in energy and nutrient flow in the biological food chain. Plant carnivory has attracted much interest since Darwin's time, but many fundamental properties of the carnivorous lifestyle are largely unexplored. In particular, the chain of events leading from prey perception to its digestive utilization remains to be elucidated. One of the first steps after the capture of animal prey, i.e. the enzymatic breakup of the insects' chitin-based shell, is reflected by considerable chitinase activity in the secreted digestive fluid in the carnivorous plant Venus flytrap. This study addresses the molecular nature, function, and regulation of the underlying enzyme, VF chitinase I. Using mass spectrometry based de novo sequencing, VF chitinase I was identified in the secreted fluid. As anticipated for one of the most prominent proteins in the flytrap's "green stomach" during prey digestion, transcription of VF chitinase I is restricted to glands and enhanced by secretion-inducing stimuli. In their natural habitat, Venus flytrap is exposed to high temperatures. We expressed and purified recombinant VF chitinase I and show that the enzyme exhibits the hallmark properties expected from an enzyme active in the hot and acidic digestive fluid of Dionaea muscipula. Structural modeling revealed a relative compact globular form of VF chitinase I, which might contribute to its overall stability and resistance to proteolysis. These peculiar characteristics could well serve industrial purposes, especially because of the ability to hydrolyze both soluble and crystalline chitin substrates including the commercially important cleavage of ?-chitin.

Paszota, Paulina; Escalante-Perez, Maria

2014-01-01

199

Characterization of the lower layer in the dayside Venus ionosphere  

Science.gov (United States)

The dayside Venus ionosphere consists of two layers: the V2 layer at 141 km, produced by solar extreme ultraviolet (EUV) photons, and the V1 layer at 127 km, produced by solar soft X-rays. The influence of solar zenith angle (SZA) and solar irradiance has been well characterized for the V2 layer, but not the V1 layer, where previous efforts were limited by data scarcity and incomplete SZA coverage. Here we use over 200 radio occultation profiles from Venus Express to characterize how the V1 peak altitude, peak density, and morphology respond to changes in SZA and solar activity. The V1 and V2 peak altitudes do not vary with SZA, and both peak electron densities vary with SZA in a Chapman-like manner. These results imply that the thermal structures of the atmosphere and ionosphere between 141 km and 127 km vary little with SZA. Also, the V1 peak density increases more with solar activity than the V2 peak density and the V1 morphology can change much more than the V2 morphology. These results are due to the soft X-ray flux increasing relative to the EUV flux as solar activity increases.

Girazian, Zachary; Withers, Paul; Paetzold, Martin; Tellmann, Silvia; Peter, Kerstin

2014-11-01

200

Impact-generated winds on Venus: Causes and effects  

Science.gov (United States)

The pressure of the dense atmosphere of Venus significantly changes the appearance of ejecta deposits relative to craters on the Moon and Mercury. Conversely, specific styles and sequences of ejecta emplacement can be inferred to represent different intensities of atmospheric response winds acting over different timescales. Three characteristic timescales can be inferred from the geologic record: surface scouring and impactor-controlled (angle and direction) initiation of the long fluidized run-out flows; nonballistic emplacement of inner, radar-bright ejecta facies and radar-dark outer facies; and very late reworking of surface materials. These three timescales roughly correspond to processes observed in laboratory experiments that can be scaled to conditions on Venus (with appropriate assumptions): coupling between the atmosphere and earlytime vapor/melt (target and impactor) that produces an intense shock that subsequently evolves into blast/response winds; less energetic dynamic response of the atmosphere to the outward-moving ballistic ejecta curtain that generates nonthermal turbulent eddies; and late recovery of the atmosphere to impact-generated thermal and pressure gradients expressed as low-energy but long-lived winds. These different timescales and processes can be viewed as the atmosphere equivalent of shock melting, material motion, and far-field seismic response in the target. The three processes (early Processes, Atmospheric Processes, and Late Recovery Winds) are discussed at length.

Schultz, Pater H.

1992-01-01

 
 
 
 
201

Chemistry of the surface and lower atmosphere of Venus  

Science.gov (United States)

A comprehensive overview of the chemical interactions between the atmosphere and surface of Venus is presented. Earth-based, earth-orbital, and spacecraft data on the composition of the atmosphere and surface of Venus are presented and applied to quantitative evaluations of the chemical interactions between carbon, hydrogen, sulfur, chlorine, fluorine, and nitrogen-containing gases and possible minerals on the Venus surface. The calculation results are used to predict stable minerals and mineral assemblages on the Venus surface to determine which, if any, atmospheric gases are buffered by mineral assemblages on the surface, and to critically review and assess prior work on atmosphere-surface chemistry on Venus. It is concluded that the CO2 pressure on Venus is comparable to the CO2 equilibrium partial pressure developed by the calcite + wollastonite + quartz assemblage at the mean Venus surface temperature of 740 K.

Fegley, B., Jr.; Treiman, A.

1992-01-01

202

Oxygen ion escape from Venus in a global hybrid simulation: role of the ionospheric O+ ions  

Directory of Open Access Journals (Sweden)

Full Text Available We study the solar wind induced oxygen ion escape from Venus' upper atmosphere and the Venus Express observations of the Venus-solar wind interaction by the HYB-Venus hybrid simulation code. We compare the simulation to the magnetic field and ion observations during an orbit of nominal upstream conditions. Further, we study the response of the induced magnetosphere to the emission of planetary ions. The hybrid simulation is found to be able to reproduce the main observed regions of the Venusian plasma environment: the bow shock (both perpendicular and parallel regions, the magnetic barrier, the central tail current sheet, the magnetic tail lobes, the magnetosheath and the planetary wake. The simulation is found to best fit the observations when the planetary oxy~escape rate is in the range from 3×1024 s?1 to 1.5×1025 s?1. This range was also found to be a limit for a test particle-like behaviour of the planetary ions: the higher escape rates manifest themselves in a different global configuration of the Venusian induced magnetosphere.

T. L. Zhang

2009-11-01

203

The temperature of the Venus mesosphere from O 2 ( a?g1) airglow observations  

Science.gov (United States)

We have used near-infrared spectroscopic observations of the Venus nightside taken with the Infrared Imager and Spectrograph 2 (IRIS2) on the Anglo-Australian Telescope to derive temperature maps for the Venus mesosphere at an altitude of ˜95 km. The temperatures are derived from the distribution of rotational line intensities in the O 2 ( a?g1) airglow band at 1.27 ?m. To obtain reliable temperatures at the relatively low spectral resolution of IRIS2, we have developed a forward modeling approach to handle the blending of individual O 2 lines and the telluric absorption in the same O 2 band. The technique provides temperature retrievals with accuracy comparable to, or better than that of previous high-spectral resolution determinations. The resulting temperature maps show spatial temperature structure that varies from night to night, as does the intensity distribution. Intensity weighted mean temperatures range from about 181 to 196 K. The temperatures are typically 15-30 K higher than those expected from the Venus International Reference Atmosphere (VIRA) profile. The temperatures fall in regions of low O 2 emission rate to values closer to the VIRA levels. Our temperatures are similar to, but slightly lower than those obtained from stellar occultation measurements with SPICAV on Venus Express. We suggest that we are seeing a region of locally enhanced temperature caused by compressional heating in the downwelling gas around the antisolar point.

Bailey, Jeremy; Meadows, V. S.; Chamberlain, S.; Crisp, D.

2008-09-01

204

HST/STIS Observations of Venus’ Dayside Atmosphere, from morning to noon  

Science.gov (United States)

170-310 nm, high spectral (0.3 nm) and spatial (40-60 km/pixel) resolution observations of Venus’ low latitude dayside atmosphere were obtained using Hubble’s Space Telescope Imaging Spectrograph (HST/STIS), in order to measure the SO and SO2 gas column density on Venus’ morning quadrant between 20N and 40S latitude at an altitude of ~ 75±2 km, on three dates between late December 2010 and February 2011. These data provide the first direct and simultaneous measure of the SO and SO2 gas column density variability within Venus’ mesosphere as a function of both latitude and time of day. Our analysis indicates the cloud top gas densities vary strongly with latitude. On two of the 3 days of observing the gas densities are observed to peak at the equator, while the opposite trend is observed on the remaining date. On all dates, independent of the slope of the latitudinal gradient, a factor of ~ 1.7±0.5 enhancement in the SO2 gas density near the terminator (i.e., at SZA ~ 65±5°) is observed relative to the gas density detected at an equivalent latitude but smaller SZA. Using contemporaneously obtained Venus Express Monitoring Camera images, the significance of the HST inferred SO2 and SO gas density latitudinal variability relative to the observed cloud top characteristics will be discussed. Likewise, how the HST results relate to the near terminator and average dayside the SO2 and SO vertical volume mixing ratio (VMR) profiles inferred, respectively, from contemporaneously obtained Venus Express (VEx) Solar Occultation in the Infrared and sub-mm ground-based observations of Venus’s dayside atmosphere will be discussed. Lastly, the significance of the HST results relative to SPICAV observations obtained throughout the lifetime of the VEx mission will be summarized. E.g., the average dayside SO2 VMR inferred from the HST data is in the range of 42+/- 36 ppb, matching the average dayside VMR range derived from the SPICAV-UV data obtained during the entirety of 2011 (Jessup et al. 2014). These results suggest that HST data can be used to accurately document Venus’ average dayside behavior within a single year, and may be used to monitor the average SO2 gas density cloud top variance on a multi-year basis.

Jessup, Kandis-Lea; Marcq, Emmanuel; Mills, Frank; Yung, Yuk; Roman, Tony; Berteaux, Jean Loup; Mahieux, Arnaud; Wilquet, Valerie; Vandaele, Ann Carine; Wilson, Colin; Limaye, Sanjay; Markiewicz, Wojtek

2014-11-01

205

Venus - Volcano With Massive Landslides  

Science.gov (United States)

This Magellan full-resolution mosaic which covers an area 143 by 146 kilometers (89 by 91 miles) is centered at 55 degrees north latitude, 266 degrees east longitude. The bright feature, slightly south of center is interpreted to be a volcano, 15-20 kilometers (9.3 to 12.4 miles) in diameter with a large apron of blocky debris to its right and some smaller aprons to its left. A preferred explanation is that several massive catastrophic landslides dropped down steep slopes and were carried by their momentum out into the smooth, dark lava plains. At the base of the east-facing or largest scallop on the volcano is what appears to be a large block of coherent rock, 8 to 10 kilometers (5 to 6 miles) in length. The similar margin of both the scallop and block and the shape in general is typical of terrestrial slumped blocks (masses of rock which slide and rotate down a slope instead of breaking apart and tumbling). The bright lobe to the south of the volcano may either be a lava flow or finer debris from other landslides. This volcanic feature, characterized by its scalloped flanks is part of a class of volcanoes called scalloped or collapsed domes of which there are more than 80 on Venus. Based on the chute-like shapes of the scallops and the existence of a spectrum of intermediate to well defined examples, it is hypothesized that all of the scallops are remnants of landslides even though the landslide debris is often not visible. Possible explanations for the missing debris are that it may have been covered by lava flows, the debris may have weathered or that the radar may not be recognizing it because the individual blocks are too small

1992-01-01

206

The polar ionosphere of Venus near the terminator from early Pioneer Venus orbiter radio occultations  

Science.gov (United States)

Fourteen profiles of electron density in the ionosphere of Venus were obtained by the dual-frequency radio occultation method with the Pioneer Venus orbiter between 5 and 30 December 1978. A region of almost constant electron density above approximately 250 km was detected. The ionopause height is found to vary from about 300 to 700 km. The structures of the profiles are consistent with models in which O2(+) dominates near the ionization peak and is replaced by O(+) at higher altitudes.

Kliore, A. J.; Woo, R.; Armstrong, J. W.; Patel, I. R.; Croft, T. A.

1979-01-01

207

A Cubesat Mission to Venus: A Low-Cost Approach to the Investigation of Venus Lightning  

Science.gov (United States)

The occurrence of Venus lightning has been detected by atmospheric probes and landers on Venus; by ionospheric satellites; by an orbiting visible spectrometer; at radio frequencies by the Galileo spacecraft while flying by Venus; and by an Earth-based telescope. However, none of these detectors has enabled us to determine the global occurrence rate of lightning in the atmosphere of Venus, nor the altitude at which this lightning is generated. Such measurements are needed in order to determine the processes that generate Venus lightning and to establish the importance of Venus lightning in controlling the chemical composition of the Venus atmosphere. A simple and affordable mission to perform this mapping could be achieved with CubeSat technology. A mother spacecraft with at least three CubeSat partners using RF detection could map the occurrence of lightning globally and determine its altitude of origin, with triangulation of precisely timed RF event arrivals. Such a mission would provide space for complementary investigations and be affordable under the Discovery mission program. We are embarking on a program to develop CubeSat-based instrumentation for such a mission. The initial task is to develop a lightning detector in a CubeSat development kit using a software defined radio (SDR) operating at decameter wavelengths (5-50 MHz). This involves algorithm development as well as selecting or developing radio hardware for a CubeSat. Two units will be tested on the ground in a lightning zone such as New Mexico, where the Long Wavelength Array operates in the same frequency range. When the concept has been proven, flight subsystems such as solar panels, attitude sensing and communication radios will be added to the CubeSats to test performance in low Earth orbit. Experience gained from flight would enable a cluster of sensors to be proposed for a future Venus mission.

Majid, W.; Duncan, C.; Kuiper, T.; Russell, C. T.; Hart, R. A.; Lightsey, E.

2013-12-01

208

ASTRONOMICAL HERITAGES: ASTRONOMICAL ARCHIVES AND HISTORIC TRANSITS OF VENUS A Selection of Papers prepared by Working Groups Astronomical Archives and Transits of Venus of Commission 41 of the International Astronomical Union  

Science.gov (United States)

These Proceedings contain a selection of presentations and research papers emanating from meetings of the Astronomical Archives and Transits of Venus Working Groups of Commission 41, and from presentations at the last three IAU General Assemblies. Some additional reports related to the topic of this book have also been added. The first part of the book deals with archives, the second part with facts related to historical transits of Venus - although there is substantial overlap since some archive papers deal with Transits of Venus as well. The compilation deals with many wonderful and even rare sources of information, such as official documents and reports, private letters, astronomical instruments and telescopes, national inventories, photographic plates, etc. A lot of documentation described in this book is available only on national level, and the combination of this material in one single volume looks like a cross-cultural study dealing with art and science, and almost can serve as a travel guide in time and space.

Sterken, C.; Duerbeck, H. W.

2004-12-01

209

ESA's Planetary Science Archive: Status, activities and strategy  

Science.gov (United States)

The European Space Agency's Planetary Science Archive (PSA) is the central repository for all scientific and engineering data returned by ESA's planetary missions, making them accessible to the world-wide scientific community. The PSA currently holds data from Mars Express, Venus Express, SMART-1, Huygens, Rosetta and Giotto, as well as several ground-based observations of comets. It will be used for archiving on ExoMars, BepiColombo and for the European contributions to Chandrayaan-1. The PSA team is currently working on transferring to a new archiving standard for our future missions, and is developing a strategy that will greatly improve the service provided to our user community.

Heather, D.; Barthelemy, M.; Manaud, N.; Martinez, S.; Szumlas, M.; Vazquez, J. L.; Osuna, P.; PSA Development Team

2014-04-01

210

Vesper - Venus Chemistry and Dynamics Orbiter - A NASA Discovery Mission Proposal: Submillimeter Investigation of Atmospheric Chemistry and Dynamics  

Science.gov (United States)

Vesper conducts a focused investigation of the chemistry and dynamics of the middle atmosphere of our sister planet- from the base of the global cloud cover to the lower thermosphere. The middle atmosphere controls the stability of the Venus climate system. Vesper determines what processes maintain the atmospheric chemical stability, cause observed variability of chemical composition, control the escape of water, and drive the extreme super-rotation. The Vesper science investigation provides a unique perspective on the Earth environment due to the similarities in the middle atmosphere processes of both Venus and the Earth. Understanding key distinctions and similarities between Venus and Earth will increase our knowledge of how terrestrial planets evolve along different paths from nearly identical initial conditions.

Chin, Gordon

2011-01-01

211

Venus radar brightness and altitude images  

Science.gov (United States)

Seven radar-brightness and altitude images are presented. They are each of a small circular region within the equatorial belt of Venus. Resolution is, typically, 10 by 10 km; altitude contour spacing is 500 m. In addition, an image of the large rough feature, beta, is presented with 25 by 25 km resolution.

Goldstein, R. M.; Green, R. R.; Rumsey, H. C.

1978-01-01

212

Solar Airplane Concept Developed for Venus Exploration  

Science.gov (United States)

An airplane is the ideal vehicle for gathering atmospheric data over a wide range of locations and altitudes, while having the freedom to maneuver to regions of scientific interest. Solar energy is available in abundance on Venus. Venus has an exoatmospheric solar flux of 2600 W/m2, compared with Earth's 1370 W/m2. The solar intensity is 20 to 50 percent of the exoatmospheric intensity at the bottom of the cloud layer, and it increases to nearly 95 percent of the exoatmospheric intensity at 65 km. At these altitudes, the temperature of the atmosphere is moderate, in the range of 0 to 100 degrees Celsius, depending on the altitude. A Venus exploration aircraft, sized to fit in a small aeroshell for a "Discovery" class scientific mission, has been designed and analyzed at the NASA Glenn Research Center. For an exploratory aircraft to remain continually illuminated by sunlight, it would have to be capable of sustained flight at or above the wind speed, about 95 m/sec at the cloud-top level. The analysis concluded that, at typical flight altitudes above the cloud layer (65 to 75 km above the surface), a small aircraft powered by solar energy could fly continuously in the atmosphere of Venus. At this altitude, the atmospheric pressure is similar to pressure at terrestrial flight altitudes.

Landis, Geoffrey A.

2004-01-01

213

Dynamics of planetary ions at Mars and Venus in a global hybrid simulation  

Science.gov (United States)

We discuss the solar wind induced ion escape from Mars and Venus in a global hybrid simulation. Using the HYB hybrid model for planetary-solar wind interactions we analyze the dynamics of planetary ions in plasma environments of these planets. Especially, we study planetary ions with different mass-to-charge ratios ranging from hydrogen to oxygen. We analyze the trajectories and escape channels of the planetary ions under different solar wind and interplanetary magnetic field conditions and quantify how different conditions affect the ion dynamics. We consider the physics of the ion dynamics in a hybrid model and discuss the importance for in situ plasma measurements such as those made by Mars Express and Venus Express as well as the forthcoming MAVEN observations.

Jarvinen, Riku; Luhmann, Janet; Brain, Dave; Kallio, Esa

2014-05-01

214

ANALYSIS OF X-RAY SPECTRA EMITTED FROM THE VENUS ECR ION SOURCE  

Energy Technology Data Exchange (ETDEWEB)

The Versatile Electron Cyclotron resonance ion source for Nuclear Science (VENUS), located at Lawrence Berkeley National Lab’s 88-inch cyclotron, extracts ion beams from a plasma created by ionizing a gas with energetic electrons. Liquid-helium cooled superconducting coils produce magnetic fi elds that confi ne the plasma and high microwave frequencies heat the electrons enough to allow for successive ionizations of the neutral gas atoms. The combination of strong plasma confi nement and high microwave frequencies results in VENUS’ production of record breaking ion beam currents and high charge state distributions. While in operation, VENUS produces signifi cant quantities of bremsstrahlung, in the form of x-rays, primarily through two processes: 1) electron-ion collisions within the plasma, and 2) electrons are lost from the plasma, collide with the plasma chamber wall, and radiate bremsstrahlung due to their sudden deceleration. The bremsstrahlung deposited into the plasma chamber wall is absorbed by the cold mass used to maintain superconductivity in the magnets and poses an additional heat load on the cryostat. In order for VENUS to reach its maximum operating potential of 10 kW of 28 GHz microwave heating frequency, the heat load posed by the emitted bremsstrahlung must be understood. In addition, studying the bremsstrahlung under various conditions will help further our understanding of the dynamics within the plasma. A code has been written, using the Python programming language, to analyze the recorded bremsstrahlung spectra emitted from the extraction end of VENUS. The code outputs a spectral temperature, which is relatively indicative of the temperature of the hot electrons, and total integrated count number corresponding to each spectra. Bremsstrahlung spectra are analyzed and compared by varying two parameters: 1) the heating frequency, 18 GHz and 28 GHz, and 2) the ratio between the minimum magnetic fi eld and the resonant magnetic fi eld, .44 and .70, at the electron resonant zone.

Benitez, J.; Leitner, D.

2008-01-01

215

Analysis of thermal emission from the nightside of Venus at 1.51 and 1.55 mu m  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present radiative transfer modelling of thermal emission from the nightside of Venus in two 'spectral window' regions at 1.51 and 1.55 ?m. The first discovery of these windows, reported by Erard et al. [Erard, S., Drossart, P., Piccioni, G., 2009. J. Geophys. Res. Planets 114, doi:10.1029/2008JE003116. E00B27], was achieved using a principal component analysis of data from the VIRTIS instrument on Venus Express. These windows are spectrally narrow, with a full-width at half-maximum of ?...

Wilson, Cf; Tsang, Ccc; Irwin, Pgj; Taylor, Fw; Bezard, B.; Erard, S.; Carlson, Rw; Drossart, P.; Piccioni, G.; Holmes, Rc

2009-01-01

216

Remote Raman - laser induced breakdown spectroscopy (LIBS) geochemical investigation under Venus atmospheric conditions  

Energy Technology Data Exchange (ETDEWEB)

The extreme Venus surface temperatures ({approx}740 K) and atmospheric pressures ({approx}93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. and Sharma et al. demonstrated that both analytical techniques can be integrated into a single instrument capable of planetary missions. The focus of this paper is to explore the capability to probe geologic samples with Raman - LIBS and demonstrate quantitative analysis under Venus surface conditions. Raman and LIBS are highly complementary analytical techniques capable of detecting both the mineralogical and geochemical composition of Venus surface materials. These techniques have the potential to profoundly increase our knowledge of the Venus surface composition, which is currently limited to geochemical data from Soviet Venera and VEGA landers that collectively suggest a surface composition that is primarily tholeiitic basaltic with some potentially more evolved compositions and, in some locations, K-rich trachyandesite. These landers were not equipped to probe the surface mineralogy as can be accomplished with Raman spectroscopy. Based on the observed compositional differences and recognizing the imprecise nature of the existing data, 15 samples were chosen to constitute a Venus-analog suite for this study, including five basalts, two each of andesites, dacites, and sulfates, and single samples of a foidite, trachyandesite, rhyolite, and basaltic trachyandesite under Venus conditions. LIBS data reduction involved generating a partial least squares (PLS) model with a subset of the rock powder standards to quantitatively determine the major elemental abundance of the remaining samples. PLS analysis suggests that the major element compositions can be determined with root mean square errors ca. 5% (absolute) for SiO{sub 2}, Al{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}(total), MgO, and CaO, and ca. 2% or less for TiO{sub 2}, Cr{sub 2}O{sub 3}, MnO, K{sub 2}O, and Na{sub 2}O. Finally, the Raman experiments have been conducted under supercritical CO{sub 2} involving single-mineral and mixed-mineral samples containing talc, olivine, pyroxenes, feldspars, anhydrite, barite, and siderite. The Raman data have shown that the individual minerals can easily be identified individually or in mixtures.

Clegg, Sanuel M [Los Alamos National Laboratory; Barefield, James E [Los Alamos National Laboratory; Humphries, Seth D [Los Alamos National Laboratory; Wiens, Roger C [Los Alamos National Laboratory; Vaniman, D. T. [Los Alamos National Laboratory; Sharma, S. K. [UNIV OF HAWAII; Misra, A. K. [UNIV OF HAWAII; Dyar, M. D. [MT. HOLYOKE COLLEGE; Smrekar, S. E. [JET PROPULSION LAB.

2010-12-13

217

On the Decadal Variation of sulfur dioxide at the Cloud Top of Venus  

Science.gov (United States)

Venus atmosphere is a natural laboratory of sulfur chemistry. As one of the parent species of sulfur, sulfur dioxide (SO_2) is generated in the lower atmosphere and transported upward to the middle atmosphere, where it is further oxidized and eventually produces sulfuric acid cloud. The 30-year observations from the Pioneer Venus (Esposito et al., 1988) and the Venus Express (Marcq et al., 2012) show a decadal variation of total column abundance of SO_2 above the cloud top. The amplitude varies in about two orders of magnitude and therefore poses a question on what causes such a dramatic change on the sulfur budget. Previous interpretations include episodic volcanic eruption (Esposito 1984) and long-time dynamical oscillations (Marcq et al., 2012) that supported by a recent general circulation model on Venus (Parish et al., 2011). Here we attempt to understand the secular variation of SO_2 using a one-dimensional (1D) time-evolving photochemistry-diffusion model which includes about 50 species and about 350 reactions (Zhang et al., 2010; 2011). Specifically for this study, we perturb the mean steady state of the middle atmosphere of Venus by adding forcings at the bottom layer (at about 58 km). Two types of forcing are considered here: (1) the volcanic eruption is simulated by a mass flux injected from the bottom layer; and (2) a wavy structure is provided on the eddy diffusion profile to approximate the dynamical perturbations. Important parameters such as the amplitude and timescale of the forcings are constrained by the observation secular patterns. Possible consequences are discussed and the variations for other species are predicted to guide the future observations. This research was supported by the Bisgrove scholar Program in the University of Arizona.

Zhang, Xi

218

The Venus environment; Proceedings of the International Conference, Palo Alto, CA, November 1-6, 1981  

Science.gov (United States)

Attention is given to noble gases in planetary atmospheres, the photochemistry of the stratosphere of Venus, the chemistry of metastable species in the Venusian ionosphere, the Venus ionosphere at grazing incidence of solar radiation, disappearing ionospheres on the nightside of Venus, and the observed composition of the ionosphere of Venus. Other investigations considered are concerned with the predicted electrical conductivity between 0 and 80 km in the Venusian atmosphere, sulfuric acid vapor and other cloud-related gases in the Venus atmosphere, the composition and vertical structure of the lower cloud deck on Venus, amorphous sulfur as the ultraviolet absorber on Venus, and polarization studies of the Venus UV contrasts. A description is provided of topics related to temporal variability of ultraviolet cloud features in the Venus stratosphere, zonal mean circulation at the cloud level on Venus, the influence of thermospheric winds on exospheric hydrogen on Venus, and an analysis of Venus gravity data.

1982-01-01

219

Venus In Situ Explorer Mission design using a mechanically deployed aerodynamic decelerator  

Science.gov (United States)

The Venus In Situ Explorer (VISE) Mission addresses the highest priority science questions within the Venus community outlined in the National Research Council's Decadal Survey. The heritage Venus atmospheric entry system architecture, a 45° sphere-cone rigid aeroshell with a carbon phenolic thermal protection system, may no longer be the preferred entry system architecture compared to other viable alternatives being explored at NASA. A mechanically-deployed aerodynamic decelerator, known as the Adaptive Deployable Entry and Placement Technology (ADEPT), is an entry system alternative that can provide key operational benefits and risk reduction compared to a rigid aeroshell. This paper describes a mission feasibility study performed with the objectives of identifying potential adverse interactions with other mission elements and establishing requirements on decelerator performance. Feasibility is assessed through a launch-to-landing mission design study where the Venus Intrepid Tessera Lander (VITaL), a VISE science payload designed to inform the Decadal Survey results, is repackaged from a rigid aeroshell into the ADEPT decelerator. It is shown that ADEPT reduces the deceleration load on VITaL by an order of magnitude relative to a rigid aeroshell. The more benign entry environment opens up the VISE mission design environment for increased science return, reduced risk, and reduced cost. The ADEPT-VITAL mission concept of operations is presented and details of the entry vehicle structures and mechanisms are given. Finally, entry aerothermal analysis is presented that defines the operational requirements for a revolutionary structural-TPS material employed by ADEPT: three-dimensionally woven carbon cloth. Ongoing work to mitigate key risks identified in this feasibility study is presented.

Smith, B.; Venkatapathy, E.; Wercinski, P.; Yount, B.; Prabhu, D.; Gage, P.; Glaze, L.; Baker, C.

220

Communications Transceivers for Venus Surface Missions  

Science.gov (United States)

The high temperature of the surface of Venus poses many difficulties. Previous Venus landers have only operated for short durations before succumbing to the heat. NASA Glenn Research Center conducted a study on communications for long duration Venus surface missions. I report the findings in this presentation. Current technology allows production of communications transceivers that can operate on the surface of Venus, at temperatures above 450 C and pressures of over 90 atmospheres. While these transceivers would have to be relatively simple, without much of the advanced signal processing often used in modern transceivers, since current and near future integrated circuits cannot operate at such high temperatures, the transceivers will be able to meet the requirements of proposed Venus Surface mission. The communication bands of interest are High Frequency or Very High Frequency (HFNHF) for communication between Venus surface and airborne probes (including surface to surface and air to air), and Ultra High Frequency (UHF) to Microwave bands for communication to orbiters. For HFNHF, transceivers could use existing vacuum tube technology. The packaging of the vacuum tubes may need modification, but the internal operating structure already operates at high temperatures. Using metal vacuum structures instead of glass, allows operation at high pressure. Wide bandgap transistors and diodes may be able to replace some of the thermionic components. VHF communications would be useful for line-of- sight operations, while HF would be useful for short-wave type communications using the Venusian ionosphere. UHF and microwave communications use magnetically focused thermionic devices, such as traveling wave tubes (TWTs), magnetron (M-type) amplifiers, and klystrons for high power amplifiers, and backward wave oscillators (BWOs) and reflex klystrons for oscillators. Permanent magnets are already in use in industry that can operate at 500 C. These magnets could focus electron beam tubes on the surface of Venus. While microwave windows will need to be designed for the high pressure, diamond windows have already been demonstrated, so high-pressure microwave windows can be designed and built. Thus, all of these devices could be useful for Venus surface missions. Current electronic power conditioners to supply the high voltages used in these microwave devices cannot operate at high temperatures, but earlier electronic power conditioners that used vacuum tubes can be modified to work at high temperature. Evaluating the various devices in this study, the M-type traveling wave tube (where a traveling wave structure is used in a crossed-field device, similar to the Amplitron used on the Apollo missions) stood out for the high power amplifier since it requires a single high voltage, simplifying the power supply design. Since the receiver amplifier is a low power amplifier, the loss of efficiency in linear beam devices without a depressed collector (and thus needing a single high voltage) is not important; a low noise TWT is a possible solution. Before solid-state microwave amplifiers were available, such TWTs were built with a 1-2 dB noise figure. A microwave triode or transistor made from a wide bandgap material may be preferable, if available. Much of the development work needed for Venusian communication devices will need to focus on the packaging of the devices, and their connections, but the technology is available to build transceivers that can operate on the surface of Venus indefinitely.

Force, Dale A.

2004-01-01

 
 
 
 
221

Dynamic compensation of Venus's geoid: A comparison with Earth  

Science.gov (United States)

Unlike Earth, on Venus long wavelength geoid anomalies correlate well with topography. Venus's admittance curve between harmonic degrees 3 and 18 is inconsistent with Airy isostasy but is consistent with dynamic support from convection being the dominant mechanism of compensation on Venus. We model dynamic compensation on Venus using simple flow models which assume a spherically symmetric Newtonian mantle viscosity profile. Preliminary models parameterize the viscosity variation with depth as a 2 layer model with a boundary at 720 km depth. A model in which viscosity in the lower mantle is a factor of 10 lower than in the upper mantle can explain Venus's observed admittance curve for degrees 3 through 18. Dynamic models which include a chemical boundary between the upper and lower mantle do not successfully explain the observed admittance curve, indicating that Venus does not have a chemically layered mantle.

Kiefer, W. S.; Hager, B. H.; Richards, M. A.

1985-01-01

222

First stage of cosmic expedition Vega: Venus investigations  

International Nuclear Information System (INIS)

Main results of the first (Venus) stage of the international complex program ''Venus - Halley'' (''Vega'' for short) are presented. The program is aimed at transporting descent space vehicles to the Venus to explore its atmosphere and surface. Then automatic interplanetary stations (AIS) will be directed to the Halley's comet. In June 1985 the descent space vehicles AIS ''Vega-1'' and ''Vega-2'' have landed softly on the Venus surface, aerostat probes have been launched to the planet atmosphere. The design of the descent space vehicle, structure and chemical composition of the atmosphere, ground composition are briefly outlined

223

Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars  

Directory of Open Access Journals (Sweden)

Full Text Available Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow shock. The observed ions have a large field-aligned velocity compared to the perpendicular velocity in the solar wind frame, and are similar to the field-aligned beams and intermediate gyrating component of the foreshock ions in the terrestrial upstream region. Mars Express does not observe similar foreshock ions as does Venus Express, indicating that the Martian foreshock does not possess the intermediate gyrating component in the upstream region on the dayside of the planet. Instead, two types of gyrating protons in the solar wind frame are observed very close to the Martian quasi-perpendicular bow shock within a proton gyroradius distance. The first type is observed only within the region which is about 400 km from the bow shock and flows tailward nearly along the bow shock with a similar velocity as the solar wind. The second type is observed up to about 700 km from the bow shock and has a bundled structure in the energy domain. A traversal on 12 July 2005, in which the energy-bunching came from bundling in the magnetic field direction, is further examined. The observed velocities of the latter population are consistent with multiple specular reflections of the solar wind at the bow shock, and the ions after the second reflection have a field-aligned velocity larger than that of the de Hoffman-Teller velocity frame, i.e., their guiding center has moved toward interplanetary space out from the bow shock. To account for the observed peculiarity of the Martian upstream region, finite gyroradius effects of the solar wind protons compared to the radius of the bow shock curvature and effects of cold ion abundance in the bow shock are discussed.

M. Yamauchi

2011-03-01

224

Hybrid Particle Code Simulations of Venus  

Science.gov (United States)

This paper will present the latest results of high resolution 3-D hybrid particle code simulations of Venus. The research is focused on understanding the solar wind interaction with Venus and the subsequent ionospheric losses that occur as a consequence of this loss. In addition, the simulations focus on structures caused by the interaction particularly on the pole of the planet where the convection electric field points. A variety of simulation results will be presented each with varying solar wind parameters. The hybrid particle code HALFSHEL contains a variety of physical and chemical models which will also be discussed. These include a chemistry package that produces the ionosphere on grid resolution of 10 km altitude, as well as the Hall and Pedersen conductivities associated with plasma neutral collisions. The specific simulations to be presented trace solar wind protons, and ionospheric O+ and O2+.

Brecht, Stephen; Ledvina, S.

225

The change of resurfacing regimes on Venus  

Science.gov (United States)

The change of volcanic resurfacing regimes on Venus is discussed. The frequency-size distribution of the regional and lobate plains fields suggest that regional plains had likely been formed due to lava flooding. The geological ratios of impact craters with plains units of different ages are analyzed. Only 3% of the craters located on the older regional plains are found to be embayed by plains material. About 50% of the craters located on the younger lobate plains are found to be embayed by plains lavas. Both the frequency-size distribution of the regional plains fields and the number of embayed craters indicate their catastrophic formation. For lobate plains, these parameters indicate a gradual and time-stretched accumulation of their material. Thus, the volcanic resurfacing regimes must have been changing radically throughout the observable portion of the geological history of Venus.

Ivanov, M. A.

2015-01-01

226

La Hieroglyphica y el Nacimiento de Venus  

Directory of Open Access Journals (Sweden)

Full Text Available Sin duda a Botticelli se le debe el honor de ser el primero en pintar cuadros mitológicos monumentales que en tamaño competían con el arte religioso de la época. Entre sus argumentos, los más afamados vienen a ser las dos pinturas (hacia 1478 hoy custodiadas en los Uffizi y que conocemos como La Primavera y el Nacimiento de Venus, fábulas que proceden muy probablemente de la Villa di Castello de la que era propietario Lorenzo de Pierfrancesco, primo de Lorenzo de Médici y mecenas del maestro pintor. Las dos pinturas, como analizan importantes historiadores como Gombrich y Panofsky parecen responder a un concreto programa argumentai de claro sentido platónico y que explican la idea del Amor a través de la Venus Humanitas y la Celestis, es decir, el sentimiento humano y el contemplativo, comportamientos generados por Dios y por lo tanto, buenos en sí mismos…

González de Zarate, Jesús maría

2003-09-01

227

Plasma channels in the Venus upper ionosphere  

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Full Text Available The structure of the Venus nightside ionosphere is modeled in terms of a flow configuration derived from the position of the intermediate transition along the flanks of the ionosheath downstream from the magnetic polar regions. It is suggested that the shocked solar wind erodes more strongly the polar ionosphere producing plasma channels that extend downstream from the magnetic polar regions. Such features represent the main source of mass loss along the plasma tail and imply a small overall solar wind-induced depletion of the planetary ionosphere. The plasma channels can account for the observation of ionospheric holes in PVO passes through the Venus wake. The expected flow distribution within the wake is consistent with the entry of plasma fluxes from the magnetic polar regions that was suggested earlier to account for geometry of the nightside ionopause (Pérez de Tejada, 1980.

H. Pérez de Tejada

2001-05-01

228

Venus y el fin del mundo  

Directory of Open Access Journals (Sweden)

Full Text Available Este artículo busca demostrar que los argumentos generales acerca de la exploración científica valen también para las ciencias espaciales. El trabajo se basa en el ejemplo de la exploración de Venus y lo que esta nos dice acerca de nuestro propio planeta. Argumenta que el concepto de la probabilidad de Leslie es incorrecto, como también lo son las dudas sobre la evidencia Venusiana. Así mismo, concluye que no se puede rechazar la importancia que tienen los descubrimientos inesperados que han resultado de la exploración de Venus para ayudarnos a comprender nuestro propio planeta. Y que si van a ser rechazados estos descubrimientos debe ser por razones científicas, no por intuiciones acerca de la probabilidad.

Gonzalo Munévar

2006-01-01

229

Linelist of HD16O for study of atmosphere of terrestrial planets (Earth, Venus and Mars)  

Science.gov (United States)

Studies of water vapor in the atmospheres of Venus, Mars and Earth by spectroscopic techniques are being made routinely with different instruments on board of interplanetary missions like Mars-Express, Venus-Express and many others as well as with a lot of spacecrafts on the Earth’ orbit. Accessibility of detailed spectroscopic information in a wide range is then of crucial importance to retrieve reliable results with these instruments. Unlike Earth, Mars and Venus have the CO2-rich planetary atmospheres that require line shape parameters for HDO-CO2 broadening. In this paper a new linelist for HD16O is presented. This linelist covers the range of 0.00065-25,660 cm-1 and is significantly more complete than other databases presently available. All lines with intensities (for 100% abundance) greater than 10-30 cm/molecule at 296 K are included. Wavenumbers for 43% (about 300,000) of all lines were evaluated at a level of the best experimental accuracy. For each transition the line shape parameters such as halfwidth and temperature exponent are provided for the case of HDO-air, HDO-HDO, and HDO-CO2 broadening. The final linelist contains more than 700,000 HD16O lines and is presented in HITRAN-compatible format.

Lavrentieva, N. N.; Voronin, B. A.; Naumenko, O. V.; Bykov, A. D.; Fedorova, A. A.

2014-07-01

230

Vertical structure of the atmosphere of Venus from Pioneer Venus orbiter radio occultations  

Science.gov (United States)

Between December 1978 and February 1979 the Pioneer Venus orbiter spacecraft returned some 140 S band and X band radio occultation measurements of the Venus atmosphere. Results from 13 measurements, covering diverse latitudes from near equatorial to polar, are presented in this paper in the form of vertical profiles of temperature. The temperature profiles show a pronounced inversion at the tropopause for latitudes higher than about 50 deg, with the deepest inversions occurring between the latitudes of 60 deg and 70 deg, the latitudes at which the cold collar cloud feature was observed by the Pioneer Venus Vortex instrument. A comparison of the temperature profiles derived from radio occultation measurements with the stratospheric infrared temperature soundings of the Vortex instrument and the in situ measurements of tropospheric temperature and pressure by the North, Sounder, and Day probes indicates excellent agreement.

Kliore, A. J.; Patel, I. R.

1980-01-01

231

Observations of Venus at 1-meter wavelength  

Science.gov (United States)

Radio wavelength observations of Venus (including from the Magellan spacecraft) have been a powerful method of probing its surface and atmosphere since the 1950's. The emission is generally understood to come from a combination of emission and absorption in the subsurface, surface, and atmosphere at cm and shorter wavelengths [1]. There is, however, a long-standing mystery regarding the long wavelength emission from Venus. First discovered at wavelengths of 50 cm and greater [2], the effect was later confirmed to extend to wavelengths as short as 13 cm [1,3]. The brightness temperatures are depressed significantly 50 K around 10-20 cm, increasing to as much as 200 K around 1 m) from what one would expect from a "normal" surface (e.g., similar to the Moon or Earth) [1-3].No simple surface and subsurface model of Venus can reproduce these large depressions in the long wavelength emission [1-3]. Simple atmospheric and ionospheric models fail similarly. In an attempt to constrain the brightness temperature spectrum more fully, new observations have been made at wavelengths that cover the range 60 cm to 1.3 m at the Very Large Array, using the newly available low-band receiving systems there [4]. The new observations were made over a very wide wavelength range and at several Venus phases, with that wide parameter space coverage potentially allowing us to pinpoint the cause of the phenomenon. The observations and potential interpretations will be presented and discussed.[1] Butler et al. 2001, Icarus, 154, 226. [2] Schloerb et al. 1976, Icarus, 29, 329; Muhleman et al. 1973, ApJ, 183, 1081; Condon et al. 1973, ApJ, 183, 1075; Kuzmin 1965, Radiophysics. [3] Butler & Sault 2003, IAUSS, 1E, 17B. [4] Intema et al. 2014, BASI, 1.

Butler, Bryan J.

2014-11-01

232

Atmospheric Chemistry of Venus-like Exoplanets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough for chemical equilibira between the atmosphere and lithosphere, as on Venus. The results of our calculations place constraints on abundances of spectroscopically observable gases, the surface temperature and pressure, and the mineralogy of the surface. These results will be useful in planning future observations of the atmospheres of terrestrial-sized exoplanets by ...

Schaefer, Laura; Fegley Jr, Bruce

2010-01-01

233

Solar diameter with 2012 Venus transit  

CERN Document Server

The role of Venus and Mercury transits is crucial to know the past history of the solar diameter. Through the W parameter, the logarithmic derivative of the radius with respect to the luminosity, the past values of the solar luminosity can be recovered. The black drop phenomenon affects the evaluation of the instants of internal and external contacts between the planetary disk and the solar limb. With these observed instants compared with the ephemerides the value of the solar diameter is recovered. The black drop and seeing effects are overcome with two fitting circles, to Venus and to the Sun, drawn in the undistorted part of the image. The corrections of ephemerides due to the atmospheric refraction will also be taken into account. The forthcoming transit of Venus will allow an accuracy on the diameter of the Sun better than 0.01 arcsec, with good images of the ingress and of the egress taken each second. Chinese solar observatories are in the optimal conditions to obtain valuable data for the measurement ...

Sigismondi, Costantino

2012-01-01

234

Pioneer Venus Sounder Probe Solar Flux Radiometer  

Science.gov (United States)

The Solar Flux Radiometer aboard the Pioneer Venus Sounder Probe operated successfully during its descent through the atmosphere of Venus. The instrument measured atmospheric radiance over the spectral range from 400 to 1800 nm as a function of altitude. Elevation and azimuthal measurements on the radiation field were made with five optical channels. Twelve filtered Si and Ge photovoltaic detectors were maintained near 30 C with a phase-change material. The detector output currents were processed with logarithmic transimpedance converters and digitized with an 11-bit A/D converter. Atmospheric sampling in both elevation and azimuth was done according to a Gaussian integration scheme. The serial output data averaged 20 bits/sec, including housekeeping (sync, spin period, sample timing and mode). The data were used to determine the deposition of solar energy in the atmosphere of Venus between 67 km and the surface along with upward and downward fluxes and radiances with an altitude resolution of several hundred meters. The results allow for more accurate modeling of the radiation balance of the atmosphere than previously possible.

Tomasko, M. G.; Doose, L. R.; Palmer, J. M.; Holmes, A.; Wolfe, W. L.; Debell, A. G.; Brod, L. G.; Sholes, R. R.

1980-01-01

235

Average configuration of the induced venus magnetotail  

International Nuclear Information System (INIS)

In this paper we discuss the interaction of the solar wind flow with Venus and describe the morphology of magnetic field line draping in the Venus magnetotail. In particular, we describe the importance of the interplanetary magnetic field (IMF) X-component in controlling the configuration of field draping in this induced magnetotail, and using the results of a recently developed technique, we examine the average magnetic configuration of this magnetotail. The derived J x B forces must balance the average, steady state acceleration of, and pressure gradients in, the tail plasma. From this relation the average tail plasma velocity, lobe and current sheet densities, and average ion temperature have been derived. In this study we extend these results by making a connection between the derived consistent plasma flow speed and density, and the observational energy/charge range and sensitivity of the Pioneer Venus Orbiter (PVO) plasma analyzer, and demonstrate that if the tail is principally composed of O+, the bulk of the plasma should not be observable much of the time that the PVO is within the tail. Finally, we examine the importance of solar wind slowing upstream of the obstacle and its implications for the temperature of pick-up planetary ions, compare the derived ion temperatures with their theoretical maximum values, and discuss the implications of this process for comets and AMPTE-type releases

236

Venus tectonics - Initial analysis from Magellan  

Science.gov (United States)

The styles of lithospheric deformation, the inferred mechanical properties of the lithosphere, and their implications for the tectonic history of Venus are discussed on the basis of radar imaging and altimetry data from Magellan. Observations of the planet plains reveal a superposition of different episodes of deformation and volcanism, strain both distributed and concentrated into zones of extension and shortening, and features reflecting a crustal response to mantle dynamic processes. Lithospheric shortening and crustal thickening are represented by ridge belts and mountain belts. The latter show the evidence for extension and collapse both during and following crustal compression. Venus displays quasi-circular coronae and broad rises with linear rift zones, associated with significant volcanism. Large-offset strike-slip faults have not been observed, although horizontal shear is accommodated across broad zones of crustal shortening. On Venus strain is distributed across zones that are one to a few hundred kilometers wide, and separated by stronger and less deformed blocks hundreds of kilometers in width, as in actively deforming continental regions on earth.

Solomon, S. C.; Head, J. W.; Kaula, W. M.; McKenzie, D.; Parsons, B.; Phillips, R. J.; Schubert, G.; Talwani, M.

1991-04-01

237

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

Science.gov (United States)

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 atmosphere rises on the dayside producing adiabatic cooling and drops on the nightside producing some adiabatic heating. (See figure 1). The thermosphere was discovered from drag measurements to respond to the near 27-day period of the rotating Sun, for which regions of maximum solar activity reappear every 27 days. The increased euv emission from active regions increased temperatures and thermospheric density, (See Figure 2). Fig. 2 Exospheric Temperatures Compared to 10.7cm Solar Index Second diurnal survey (12/5/79 - 3/6/80) Pioneer Venus Orbiter measurements (OAD) 11 day running means [2] Estimates were also made of the response to the 11- year Solar Cycle by combining the Pioneer Venus and Magellan data. Dayside exospheric temperatures changed about 80K over the solar cycle, [8]. Earlier estimates of temperature change gave 70K based on Lyman alpha measurements. The responses to solar variability were much weaker than on Earth due apparently to the much stronger O/CO2 cooling on Venus which tended to act as a thermostat on thermospheric temperatures. Another discovery from drag measurements was the 4 to 5 day oscillation of the Venus thermosphere [3], (See figure 3). These oscillations are interpreted as resulting from the 4-day super-rotation of the atmosphere near the cloud tops. Other indications of the super-rotation of the thermosphere come from displacement of the helium bulge and atomic hydrogen bulge from midnight to near 4AM. Fig. 3 Four to Five Day Oscillations in Thermospheric Densities Magellan 1992. During 2008, the Venus Express periapsis will be dropped from 250km down to approximately 180km to allow drag measurements to be made in the North Polar Region, [9]. Drag measurements above 200km have already been obtained from both Pioneer Venus and Magellan so measurements near 180km should be accurate. In 2009, the periapsis may be decreased to a lower altitude allowing accelerometer measurements to be obtained of drag as a function of altitude, to determine density, scale height, inferred temperature, pressure, and other paramete

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

2008-09-01

238

Assignment and rotational analysis of new absorption bands of carbon dioxide isotopologues in Venus spectra  

International Nuclear Information System (INIS)

We present absorption bands of carbon dioxide isotopologues, detected by the Solar Occultation for the Infrared Range (SOIR) instrument on board the Venus Express Satellite. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter (AOTF) for order selection. It performs solar occultation measurements in the Venus atmosphere in the IR region (2.2–4.3 ?m), at a resolution of 0.12–0.18 cm?1. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65–150 km) to be made with emphasis on the vertical distributions of gases. Thanks to the SOIR spectral resolution, a new CO2 absorption band was identified: the 21101–01101 band of 16O12C18O with R branch up to J=31. Two other previously reported bands were observed dispelling any doubts about their identifications: the 20001–00001 band of 16O13C18O [Villanueva G, et al. J Quant Spectrosc Radiat Transfer 2008;109:883–894] and the 01111–00001 band of 16O12C18O [Villanueva G, et al. J Quant Spectrosc Radiat Transfer 2008;109:883–894 and Wilquet V, et al. J Quant Spectrosc Radiat Transfer 2008;109:895–905]. These bands were analyzed, and spectroscopic constants characterizing them were obtained. The rotational assignment of the 20001–00001 band was corrected. The present measurements are compared with data available in the HITRAN database. -- Highlights: ? The spectra recorded by the SOIR instrument onboard Venus Express are analyzed. ? One new band of 16O12C18O was identified for the first time. ? Two other bands 16O13C18O and 16O12C18O were reanalyzed. ? Spectroscopic constants have been obtained for the three bands.

239

Composition of the Venus mesosphere: a synthesis of SOIR/VEX observations  

Science.gov (United States)

The SOIR instrument on-board Venus Express performs solar occultation measurements in the IR region (2.2 - 4.3 mum or 3800 to 4000 cm (-1) ) at a resolution of 0.12 cm (-1) , the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. Several trace gases are measured together with CO _{2} in the SOIR wavelength range. This allows the derivation of their vertical density profiles together with the temperature and total density profiles obtained from the CO _{2} measurements, which finally result in VMR profiles. The measurements all occur at the Venus terminator, both the morning and evening side, covering all latitudes from the North Pole to the South Pole. The vertical resolution is very good from the North Pole to 40° North (resolution of 500 m), and is poorer in the Southern hemisphere (resolution between 1 and 2.5 km). The maximum extent of the vertical profiles is from 70 to 120 km, with variations from orbit to orbit. The region of the atmosphere of Venus probed by the SOIR instrument encompasses thus the mesosphere and the lower thermosphere of the planet. We will present results from the measurements of trace gases, such as H2O and its isotopologue HDO, HF, HCl, CO, or SO _{2}. We will analyze time as well as latitudinal variations. We will also present the SOIR Terminator Model which is being compiled based on these observations. For the moment the model contains information on the CO _{2} and total densities, CO _{2} vmr, and temperature, but it will be extended to trace gases.

Vandaele, Ann C.; Mahieux, Arnaud; Belyaev, Denis; Bertaux, Jean-Loup; Fedorova, Anna; Piccialli, Arianna; Drummond, Rachel; Robert, Severine; Montmessin, Franck; Korablev, Oleg; Wilquet, Valérie; Thomas, Ian

240

Reassessment of planetary protection requirements for Venus missions  

Science.gov (United States)

In 2005 the US Space Studies Board SSB was asked by NASA to reexamine the planetary protection requirements for spacecraft missions to Venus In particular the SSB was tasked to 1 Assess the surface and atmospheric environments of Venus with respect to their ability to support the survival and growth of Earth-origin microbial contamination by future spacecraft missions and 2 Provide recommendations related to planetary protection issues associated with the return to Earth of samples from Venus The task group established by the SSB to address these issues assessed the known aspects of the present-day environment of Venus and the ability of Earth organisms to survive in the physical and chemical conditions found on the planet s surface or in the clouds in the planet s atmosphere As a result of its deliberations the task group found compelling evidence against there being significant dangers of forward or reverse biological contamination as a result of contact between a spacecraft and the surface of Venus or the clouds in the atmosphere of Venus regardless of the current unknowns The task group did however conclude that Venus is a body of interest relative to the process of chemical evolution and the origin of life As a result the task group endorses NASA s current policy of subjecting missions to Venus to the requirements imposed by planetary protection Category II rather than the less restrictive Category I recommended by COSPAR

Szostak, J.; Riemer, R.; Smith, D.; Rummel, J.

 
 
 
 
241

Helium on Venus - Implications for uranium and thorium  

Science.gov (United States)

Helium is removed at an average rate of 10 to the 6th atoms per square centimeter per second from Venus's atmosphere by the solar wind following ionization above the plasmapause. The surface source of helium-4 on Venus is similar to that on earth, suggesting comparable abundances of crustal uranium and thorium.

Prather, M. J.; Mcelroy, M. B.

1983-01-01

242

Infrared radiometer for the Pioneer Venus orbiter. 1: Instrument description  

International Nuclear Information System (INIS)

An IR remote sensing instrument, similar in principle to some of those on terrestrial meteorological satellites, was flown to Venus on board the Pioneer Venus orbiter. Observations of the atmosphere were made from 5 December 1978 until 14 February 1979, during seventy-two orbits of the planet. The optical techniques employed and the design and implementation of the instrument are described

243

VERITAS: A Mission Concept for the High Resolution Topographic Mapping and Imaging of Venus  

Science.gov (United States)

Magellan, a NASA mission to Venus in the early 1990's, mapped nearly the entire surface of Venus with an S-band (12 cm) synthetic aperture radar and microwave radiometer and made radar altimeter measurements of the topography. These measurements revolutionized our understanding of the geomorphology, geology and geophysical processes that have shaped the evolution of the surface of Venus. The Magellan spacecraft had an elliptical orbit with an apoapsis of approximately 8000 km and a periapsis of 257 km and an orbital inclination of 86°. In this way the radar was able to collect long strips of data approximately 10000 km in length running north to south with altitudes varying from 3000 km to 257 km. During the remainder of the orbit the collected data was down linked to earth. The SAR mode operated in burst mode fashion whereby it transmitted a small string of pulses up to a couple of hundred pulses in length followed by a quiescent period when the radar ceased transmission and allowed interleaved operation of the altimeter and radiometer modes. This mode of operation allowed for a significant reduction in downlinked SAR imaging data at the expense of azimuth (i.e. along-track) resolution. However, the lack of finer resolution imagery and topography of the surface than that obtained by the Magellan mission has hampered the definitive answer to key questions concerning the processes and evolution of the surface of Venus. The Venus Emissivity, Radio Science, InSAR Topography And Spectroscopy (VERITAS) Mission is a proposed mission to Venus designed to obtain high resolution imagery and topography of the surface using an X-band radar configured as a single pass radar interferometer coupled with a multispectral NIR emissivity mapping capability. VERITAS would map surface topography with a spatial resolution of 250 m and 5 m vertical accuracy and generate radar imagery with 30 m spatial resolution. These capabilities represent an order of magnitude or better improvement of the Magellan system and are expected to reveal definitive information on processes not possible with the Magellan data. The combination of surface topography and image data provide unprecedented knowledge of Venus' tectonic and impact history, the timing and mechanisms of volcanic resurfacing, and the mantle processes responsible for them. The combination of instruments on VERITAS, and in particular the InSAR instrument, is designed to address a series of focused hypothesis driven questions left unresolved by the Magellan mission for example: 1) Is there evidence for a past tectonic or cratered surface beneath the plains? and 2) How and when did Venus resurface? This talk will present an overview of the proposed VERITAS mission, the radar instrument design and trade options and the projected performance as well as a brief overview of some of the major science objectives. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Hensley, S.; Smrekar, S. E.; Pollard, B.

2012-12-01

244

Venus transit 2004: Illustrating the capability of exoplanet transmission spectroscopy  

CERN Document Server

The transit of Venus in 2004 offered the rare possibility to remotely sense a well-known planetary atmosphere using ground-based observations for absorption spectroscopy. Transmission spectra of Venus' atmosphere were obtained in the near infrared using the Vacuum Tower Telescope (VTT) in Tenerife. Since the instrument was designed to measure the very bright photosphere of the Sun, extracting Venus' atmosphere was challenging. CO_2 absorption lines could be identified in the upper Venus atmosphere. Moreover, the relative abundance of the three most abundant CO_2 isotopologues could be determined. The observations resolved Venus' limb, showing Doppler-shifted absorption lines that are probably caused by high-altitude winds. This paper illustrates the ability of ground-based measurements to examine atmospheric constituents of a terrestrial planet atmosphere which might be applied in future to terrestrial extrasolar planets.

Hedelt, P; Brown, T; Vera, M Collados; Rauer, H; Schleicher, H; Schmidt, W; Schreier, F; Titz, R

2011-01-01

245

Venus transit 2004: Illustrating the capability of exoplanet transmission spectroscopy  

Science.gov (United States)

The transit of Venus in 2004 offered the rare possibility to remotely sense a well-known planetary atmosphere using ground-based absorption spectroscopy. Transmission spectra of Venus' atmosphere were obtained in the near infrared using the Vacuum Tower Telescope (VTT) in Tenerife. Since the instrument was designed to measure the very bright photosphere of the Sun, extracting Venus' atmosphere was challenging. We were able to identify CO2 absorption lines in the upper Venus atmosphere. Moreover, the relative abundance of the three most abundant CO2 isotopologues could be determined. The observations resolved Venus' limb, showing Doppler-shifted absorption lines that are probably caused by high-altitude winds. We demonstrate the utility of ground-based measurements in analyzing the atmospheric constituents of a terrestrial planet atmosphere using methods that might be applied in future to terrestrial extrasolar planets.

Hedelt, P.; Alonso, R.; Brown, T.; Collados Vera, M.; Rauer, H.; Schleicher, H.; Schmidt, W.; Schreier, F.; Titz, R.

2011-09-01

246

Initial observations of the nightside ionosphere of Venus from Pioneer Venus Orbiter radio occultations  

Science.gov (United States)

Results of radio occultation measurements of electron density profiles of the nightside ionosphere of Venus at solar zenith angles from 90 to 164 deg, obtained from the Pioneer Venus Orbiter, are reported. Data were derived from closed-loop S- and X-band signals received by the Deep Space Network upon ionospheric entry and exit of the spacecraft. Nightside electron density profiles are found to be rather uniform in the solar zenith angle range of from 95 to 107 deg, with peak electron densities ranging from 23,000 to 40,000/cu cm, while between 110 and 164 deg, profiles exhibit a high degree of variability and peak electron densities vary from 7,600 to 31,800/cu cm. A possible mechanism for the maintenance of the nightside Venus ionosphere during the long Venus night, which is consistent with the observed spatial and temporal variability of deep ionospheric electron density profiles, is proposed to be impact ionization by precipitating particles, although transport processes from the dayside may also be important.

Kliore, A. J.; Patel, I. R.; Nagy, A. F.; Cravens, T. E.; Gombosi, T. I.

1979-01-01

247

The influence of lithospheric flexure on magma ascent at large volcanoes on Venus  

Science.gov (United States)

volcanoes on Venus exert large vertical loads on the lithosphere, which responds by deflecting downward. Stresses induced by this lithospheric flexure can have a strong influence on magma ascent pathways from the mantle source region to the surface. Here we propose that flexural stresses exert control over the shapes of volcanic edifices on Venus, applying criteria for magma ascent expressed in terms of stress orientations (can vertical dikes form?) and gradients (is magma squeezed upward or downward in a vertical dike?) to determine favored magma ascent paths and locations. For conical edifices emplaced on lithosphere with high elastic thickness Te, (e.g., > 40 km) both sets of magma ascent criteria are satisfied over the entire lithosphere, allowing essentially unimpeded ascent of magma to the surface and the formation of relatively steep edifices. However, for lower values of Te, high adverse stress gradients tend to cut off magma ascent beneath the summit, instead favoring lateral transport of magma at depth to distal regions with gentler stress gradients, resulting in domical edifice shapes. At the lowest values of Te (< 10 km), large short-wavelength deflections of the lithosphere tend to produce narrow and widely spaced zones of magma ascent: Such zones may produce annular ridges of volcanic material, thereby generating forms characteristic of a subset of features known as "coronae" on Venus. Another subset of coronae may form by intrusive-based generation of annular fractures at the edge of the summit region of domical edifices, as proposed for Alba Mons on Mars.

McGovern, Patrick J.; Rumpf, M. Elise; Zimbelman, James R.

2013-11-01

248

ATMOSPHERIC CHEMISTRY OF VENUS-LIKE EXOPLANETS  

International Nuclear Information System (INIS)

We use thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough for chemical equilibria between the atmosphere and lithosphere, as on Venus. The results of our calculations place constraints on abundances of spectroscopically observable gases, the surface temperature and pressure, and the mineralogy of the planetary surface. These results will be useful in planning future observations of the atmospheres of terrestrial-sized exoplanets by current and proposed space observatories such as the Hubble Space Telescope, Spitzer, the James Webb Space Telescope, and Darwin.

249

Atmospheric Chemistry of Venus-like Exoplanets  

CERN Document Server

We use thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough for chemical equilibira between the atmosphere and lithosphere, as on Venus. The results of our calculations place constraints on abundances of spectroscopically observable gases, the surface temperature and pressure, and the mineralogy of the surface. These results will be useful in planning future observations of the atmospheres of terrestrial-sized exoplanets by current and proposed space observatories such as the Hubble Space Telescope (HST), Spitzer, James Webb Space Telescope (JWST), Terrestrial Planet Finder, and Darwin.

Schaefer, Laura

2010-01-01

250

Analysis of VENUS-3 benchmark experiment  

International Nuclear Information System (INIS)

The paper presents the revision and the analysis of VENUS-3 benchmark experiment performed at CEN/SCK, Mol (Belgium). This benchmark was found to be particularly suitable for validation of current calculation tools like 3-D neutron transport codes, and in particular of the 3D sensitivity and uncertainty analysis code developed within the EFF project. The compilation of the integral experiment was integrated into the SINBAD electronic data base for storing and retrieving information about the shielding experiments for nuclear systems. SINBAD now includes 33 reviewed benchmark descriptions and several compilations waiting for the review, among them many benchmarks relevant for pressure vessel dosimetry system validation.(author)

251

La Hieroglyphica y el Nacimiento de Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sin duda a Botticelli se le debe el honor de ser el primero en pintar cuadros mitológicos monumentales que en tamaño competían con el arte religioso de la época. Entre sus argumentos, los más afamados vienen a ser las dos pinturas (hacia 1478) hoy custodiadas en los Uffizi y que conocemos como La Primavera y el Nacimiento de Venus, fábulas que proceden muy probablemente de la Villa di Castello de la que era propietario Lorenzo de Pierfrancesco, primo de Lorenzo de Mé...

Gonza?lez Zarate, Jesu?s Mari?a

2003-01-01

252

Venus Length-of-Day Variations  

Science.gov (United States)

Since 2004 we have been monitoring the instantaneous spin state of Venus with the goals of measuring the precession of the rotation axis and of quantifying daily, seasonal, and secular changes in length-of-day. We use the Goldstone and Green Bank Telescopes for these observations. The spin period of Venus is thought to be set by a delicate balance between solid-body tides and atmospheric torques that must vary as insolation and orbital parameters change [Bills 2005]. Our measurements to date reveal length-of-day (LOD) variations of 50 ppm. None of the models can be reconciled with the Magellan 500-day-average spin period of 243.0185 +/- 0.0001 days [Davies et al 1992], nor with a 16-year-average estimate of 243.023 +/- 0.002 days [Mueller et al 2012], nor with any other constant spin period. With our nominal solution we can rule out a constant spin period with over 99.9% confidence. When allowances are made for uncertainties in spin axis orientation and instantaneous spin measurement epochs, the confidence is reduced but remains higher than 99%. We attribute the LOD variations primarily to angular momentum exchange between the atmosphere and solid planet. Because there are so few constraints on the internal dynamical structure of the Venusian atmosphere, a time history of atmospheric angular momentum changes can be used to address questions related to the dynamics of the atmosphere, including its super-rotation, and climatic variations.

Margot, Jean-Luc; Campbell, D. B.; Peale, S. J.; Ghigo, F. D.

2012-10-01

253

Chemistry of atmosphere-surface interactions on Venus and Mars  

Science.gov (United States)

Earth-based, earth-orbital, and spacecraft observational data are used in the present evaluation of Venus atmosphere-surface interactions to quantitatively characterize the reactions between C, H, S, Cl, F, and N gases and plausible surface minerals. Calculation results are used to predict stable minerals and mineral assemblages on the Venus surface, in order to ascertain which (if any) of the atmospheric gases are buffeted by mineral assemblages. Chemical equilibrium calculations using extant thermodynamic data on scapolite minerals predict that carbonate-bearing scapolite and sulfate meionite are unstable on the surface of Venus, while chloride-bearing scapolite is stable.

Fegley, Bruce, Jr.; Treiman, Allan H.

1992-01-01

254

Identification of deuterium ions in the ionosphere of Venus  

Science.gov (United States)

The dominant mass two ion in the ionosphere of Venus is identified as D(+) through analysis of the height variation of (mass two ion)/(H(+)) measured in the chemical equilibrium region by the ion mass spectrometer on the Pioneer Venus Orbiter. This result leads to (D)/(H) = (2.2 + or - 0.6) x 10 to the -2 at the turbopause, which agrees with the ratio measured in the lower atmosphere by the large probe mass spectrometer. The 100-fold deuterium enrichment supports previous suggestions that Venus has lost at least 0.3 percent of a terrestrial ocean.

Hartle, R. E.; Taylor, H. A., Jr.

1983-01-01

255

Microphysical and Radiative Modelling of the Venus Condensational Middle Cloud  

Science.gov (United States)

I am using the CU / NASA Ames CARMA (Community Aerosol and Radiation Model Atmosphere) code to model the microphysical and radiative properties of the Venus middle cloud deck. The current (1-D) model reproduces the globally averaged Venus atmosphere -- as compared with Pioneer Venus LCPS observations -- in particle concentration and optical depth. The current model now conserves particle number, as well as particle mass in the simulation of nucleation, growth and evaporation of two species (sulfuric acid and water). We have coupled a radiation code to the microphysics to investigate the radiative forcings in the cloud. This work is funded through grant NCC2-1052.

McGouldrick, K.; Toon, O. B.

2003-05-01

256

Occultation of a compact radio source by Venus  

Science.gov (United States)

An occultation of the compact radio source P 0507+17 by Venus on 19 July 1988, was observed in Tidbinbilla, Australia at a frequency of 2.3 GHz. The purpose of this observation was to measure the position of Venus in the radio reference frame. When data from both ingress (Venus day side) and egress (Venus nightside) were used to solve for the position of Venus in ecliptic longitude and latitude, the results were consistent with zero offsets from the nominal values, with an uncertainty of approximately 0.2 arcsec in both coordinates. By using the nightside data alone, a value of -0.026+/-0.04 arcsec was obtained for the linear combination delta(lamda) + 0.51delta(beta) where delta(lambda) and delta(beta) were the offsets from their nominal values of the ecliptic longitude and latitude of Venus. Distortion of a vacuum Fresnel fringe pattern by the Venus troposphere, and especially by the Venus ionosphere, was observed. The day side ionosphere of Venus caused very large distortions; the amplitude of the first Fresnel fringe in the ingress data was eight times larger than had been expected for an airless planet. The observed fringe patterns were modeled by using plausible ionospheres (i.e., consistent with spacecraft measurements of the Venus ionosphere and with solar extreme ultraviolet flux and solar wind pressure measurements at the occultation epoch). However, the range of Venus ionospheric profiles (electron density as a function of altitude) allowed by a priori constraints and by the occultation data was large (e.g., the ionopause height on the day side was uncertain by a factor of two). This ionospheric uncertainty (particularly on the day side) translated into a large position uncertainty (0.2 arcsec for the day side and 0.04 arcsec for the nightside). If it had been possible to calibrate the Venus ionosphere by some external means, the accuracy in delta(lambda) and delta(beta) would have been 0.01 arcsec or better.

Linfield, R.

1992-01-01

257

Volcanism and tectonics of Venus - Venera 15/16 results  

Science.gov (United States)

Based on the radar survey of the Venus surface made by Venera 15/16 spacecraft, the volcanic and tectonic features on the Venus surface are described and interpreted in terms of the volcanism and the tectonic history of the planet. The survey included SAR images with 1 to 2 km spatial resolution, and altimetric measurements. The information obtained shows that Venus is much more endogenically dynamic than the moon, Mercury, or Mars but is less endogenically active than the earth. The results also confirm the earlier conclusions concerning the direct dependence of the scale and duration of internal activity of a planet on its size.

Basilevsky, A. T.; Ivanov, M. A.; Kryuchkov, V. P.; Pronin, A. A.; Slyuta, E. N.; Markov, M. S.; Sukhanov, A. L.

258

Line parameters for the 01111-00001 band of 12C16O18O from SOIR measurements of the Venus atmosphere  

International Nuclear Information System (INIS)

CO2 is the major constituent of the atmosphere of Venus. Absorption lines due to its 12C16O18O isotopologue have been observed for the first time in Venus spectra in the 2930-3015 cm-1 spectral region, where the HITRAN database does not contain any line from this isotopologue. The measurements were performed by the SOIR instrument, which is part of the SPICAV/SOIR instrument on board the Venus Express mission of ESA. SOIR measured the atmospheric transmission of the upper atmosphere of Venus (z>70 km) by performing a solar occultation experiment using the atmosphere as a gigantic absorption cell. The identification of this newly observed band was first made recently from Mars atmosphere observations by US colleagues. We have made independent theoretical calculations of the positions of the lines of this new 01111-00001 absorption band, which coincide perfectly with the positions of the observed lines. Assuming an oxygen isotopic ratio similar to the one measured previously in the lower atmosphere of Venus, the line strengths of each observed line are deduced and listed

259

Line parameters for the 01111-00001 band of {sup 12}C{sup 16}O{sup 18}O from SOIR measurements of the Venus atmosphere  

Energy Technology Data Exchange (ETDEWEB)

CO{sub 2} is the major constituent of the atmosphere of Venus. Absorption lines due to its {sup 12}C{sup 16}O{sup 18}O isotopologue have been observed for the first time in Venus spectra in the 2930-3015 cm{sup -1} spectral region, where the HITRAN database does not contain any line from this isotopologue. The measurements were performed by the SOIR instrument, which is part of the SPICAV/SOIR instrument on board the Venus Express mission of ESA. SOIR measured the atmospheric transmission of the upper atmosphere of Venus (z>70 km) by performing a solar occultation experiment using the atmosphere as a gigantic absorption cell. The identification of this newly observed band was first made recently from Mars atmosphere observations by US colleagues. We have made independent theoretical calculations of the positions of the lines of this new 01111-00001 absorption band, which coincide perfectly with the positions of the observed lines. Assuming an oxygen isotopic ratio similar to the one measured previously in the lower atmosphere of Venus, the line strengths of each observed line are deduced and listed.

Wilquet, V. [Belgian Institute for Space Aeronomy, 3 av. Circulaire, B-1180 Brussels (Belgium)], E-mail: valerie.wilquet@aeronomie.be; Mahieux, A.; Vandaele, A.C. [Belgian Institute for Space Aeronomy, 3 av. Circulaire, B-1180 Brussels (Belgium); Perevalov, V.I.; Tashkun, S.A. [Institute of Atmospheric Optics, Akademitcheskii av., 1, 634055 Tomsk (Russian Federation); Fedorova, A.; Korablev, O. [Space Research Institute (IKI), 84/32 Profsoyuznaya, 117810 Moscow (Russian Federation); Montmessin, F.; Dahoo, R.; Bertaux, J.-L. [Service d' Aeronomie du CNRS, BP3, 91371, Verrieres-le-Buisson (France); Universite Pierre et Marie Curie, Paris (France); Institut Pierre Simon Laplace, Universite de Versailles-Saint-Quentin, 78 Saint Quentin en Yvelines (France)

2008-04-15

260

Thermal structure of the atmosphere of Venus from Pioneer Venus radio occultations  

Science.gov (United States)

The processing and analysis results from 87 radio occultation experiments performed with the Pioneer Venus Orbiter are detailed. Atmospheric structure data were obtained with S-band (2293 MHz) and X-band (8407 MHz) signals transmitted through the 40 and 85 km levels of the Venus atmosphere. Latitudes of -68 to 88 deg at solar zenith angles of 8-166 deg were explored. The conversion of the data into acceptable form for the barometric equation to use the perfect gas law to obtain the temperature profiles is described. The temperature structures were more dependent on latitude than solar illumination conditions, with the greatest changes occurring in the circumpolar region. The polar tropopause altitude was about 4.8 km above its value at lower altitudes, with a temperature drop of 60 K and a pressure drop of 240 mb.

Kliore, A. J.; Patel, I. R.

1982-01-01

 
 
 
 
261

Recent results on the Venus atmosphere from Pioneer Venus radio occultations  

Science.gov (United States)

Temperature structure of the Venus atmosphere was derived from radio occultation data collected by the Pioneer Venus spacecraft during seven occultation seasons in the 1978-1983 period. The measurements, which cover latitudes from both poles to the equator from 40 km to 85 km altitudes, show a latitudinal dependence. At latitudes below 45 deg, there is a smooth temperature transition from the troposphere to the mesosphere. Between 60 and 80 deg, in the 'collar cloud' region, a strong temperature inversion (up to 30 K) appears, which disappears again in the polar areas (80-90 deg), where the mesosphere becomes isothermal without inversion. This temperature behavior is related to the persistent circulation pattern, in which a zonal retrograde motion below 45 deg changes gradually to a circumpolar vortex at the 'collar cloud'. A considerable temporal variability was observed in the thermal structure above the tropopause, suggesting a weather-like variability in the persistent circulation pattern.

Kliore, A. J.

1985-01-01

262

Geology of the Venus equatorial region from Pioneer Venus radar imaging  

International Nuclear Information System (INIS)

The surface characteristics and morphology of the equatorial region of Venus were first described by Masursky et al. who showed this part of the planet to be characterized by two topographic provinces, rolling plains and highlands, and more recently by Schaber who described and interpreted tectonic zones in the highlands. Using Pioneer Venus (PV) radar image data (15 deg S to 45 deg N), Senske and Head examined the distribution, characteristics, and deposits of individual volcanic features in the equatorial region, and in addition classified major equatorial physiographic and tectonic units on the basis of morphology, topographic signature, and radar properties derived from the PV data. Included in this classification are: plains (undivided), inter-highland tectonic zones, tectonically segmented linear highlands, upland rises, tectonic junctions, dark halo plains, and upland plateaus. In addition to the physiographic units, features interpreted as coronae and volcanic mountains have also been mapped. The latter four of the physiographic units along with features interpreted to be coronae

263

Experimental reconstruction of Lomonosov's discovery of Venus's atmosphere with antique refractors during the 2012 transit of Venus  

Science.gov (United States)

In 1761, the Russian polymath Mikhail Vasilievich Lomonosov (1711-1765) discovered the atmosphere of Venus during its transit over the Sun's disc. In this paper we report on experimental reenactments of Lomonosov's discovery with antique refractors during the transit of Venus June 5-6, 2012. We conclude that Lomonosov's telescope was fully adequate to the task of detecting the arc of light around Venus off the Sun's disc during ingress or egress provided proper experimental techniques as described by Lomonosov in his 1761 report are employed.

Koukarine, A.; Nesterenko, I.; Petrunin, Yu.; Shiltsev, V.

2013-11-01

264

The structure of the clouds of Venus - Results of the Pioneer Venus nephelometer experiment  

Science.gov (United States)

The nephelometer measurements by the four Pioneer Venus probes reveal an upper haze area in the vertical cloud structure with several less clearly delineated layers in the main cloud bank. Concentrated sulfuric acid is the main component of the majority of the particulate matter in the clouds; the near UV radiation is absorbed by the clouds. The particles ejected from the planet surface are in the 10 to 100 micron range.

Ragent, B.; Blamont, J.

1980-12-01

265

Chinese records of the 1874 transit of Venus  

Science.gov (United States)

Before the advent of radar, transits of Venus were very important for measuring the distance between the Earth and the Sun. A transit occurred in 1874, and was visible from China, other parts of east and southeast Asia and from India, Australia and New Zealand and certain islands in the Indian and Pacific Oceans. As a result, many astronomers from Western countries came to China to observe it. According to traditional Chinese astrology, the Sun represented the Emperor, and if the Sun was invaded by other astronomical bodies it meant that the Emperor and the country faced some ominous disaster. In the late nineteenth century, Western astronomical knowledge was widely translated into Chinese and spread among Chinese intellectuals, so the 1874 transit supposedly was easily understood by Chinese intellectuals. Before the transit took place, various Chinese publications introduced this kind of celestial event as science news, but at the same time other influential newspapers and journals discussed the astrological connection between the transit and the fortunes of the nation. In this paper we review these interesting Chinese records and discuss the different attitudes towards the transit exhibited by Chinese intellectuals and officials, during a period when Western learning was being widely disseminated throughout China.

Lu, Lingfeng; Li, Huifang

2013-03-01

266

VENUS-F: A fast lead critical core for benchmarking  

Energy Technology Data Exchange (ETDEWEB)

The zero-power thermal neutron water-moderated facility VENUS at SCK-CEN has been extensively used for benchmarking in the past. In accordance with GEN-IV design tasks (fast reactor systems and accelerator driven systems), the VENUS facility was modified in 2007-2010 into the fast neutron facility VENUS-F with solid core components. This paper introduces the projects GUINEVERE and FREYA, which are being conducted at the VENUS-F facility, and it presents the measurement results obtained at the first critical core. Throughout the projects other fast lead benchmarks also will be investigated. The measurement results of the different configurations can all be used as fast neutron benchmarks. (authors)

Kochetkov, A.; Wagemans, J.; Vittiglio, G. [SCK.CEN, Boeretang 200, 2400 Mol (Belgium)

2011-07-01

267

Rheology, tectonics, and the structure of the Venus lithosphere  

Science.gov (United States)

Given the absence of ground truth information on seismic structure, heat flow, and rock strength, or short wavelength gravity or magnetic data for Venus, information on the thermal, mechanical and compositional nature of the shallow interior must be obtained by indirect methods. Using pre-Magellan data, theoretical models constrained by the depths of impact craters and the length scales of tectonic features yielded estimates on the thickness of Venus' brittle-elastic lithosphere and the allowable range of crustal thickness and surface thermal gradient. The purpose of this study is to revisit the question of the shallow structure of Venus based on Magellan observations of the surface and recent experiments that address Venus' crustal rheology.

Zuber, M. T.

1994-01-01

268

Global organization of tectonic deformation on Venus  

Science.gov (United States)

The geographic organization of surface deformation on Venus as on Earth is a key to understanding the global tectonic system. To date we have mapped the distribution of three unambiguous tectonic land forms on Venus: (1) linear foldbelts analogous to those at plate margins of the Earth; (2) linear rift zones, analogous to continental rifts on the Earth; and (3) distributed plains deformation in the form of wrinkle ridges and extensional faults and fractures. The linear foldbelts are the dominant structural style in the Northern Hemisphere; ninety percent of the planet's foldbelts lie above the equator. In contrast, compressive deformation in the Southern Hemisphere is dominated by two large, sweeping patterns of wrinkle ridges. The two hemispheres are divided by an equatorial region that is largely covered by rift zones and several large tessera blocks. A tectonic model of generally poleward convergence of the Northern Hemisphere explains the distribution of foldbelts and rift zones. In our model, a northern hemispherical plate (or system of plates) moves poleward and deforms along discrete, predominately longitudinal bands. We recognize four types of foldbelts based on their relationships to other large-scale tectonic features on Venus. There are foldbelts that lie within the low plains, foldbelts associated with coronae, novae and chasmata, foldbelts that lie at the margins of poly-deformed tessera plateaus, and the folded mountain belts around Lakshmi Planum. We see a geometric increase in the area of fold belts when normalized to percent area at a given latitude. This increase is consistent with our model of poleward convergence. Also, the orientations of most foldbelts are either approximately north-south or parallel to lines of latitude in the northern hemisphere. This observation is also consistent with the model in that the longitudinal bands are the result of the decreasing area of the sphere as the plate moves poleward and the latitudinal belts are the direct result of poleward compression. The trends of wrinkle ridges have been mapped over the planet and several large, sweeping patterns evidently reflect long-wavelength topography. Using wrinkle ridges as paleostress indicators, we have developed local and regional stress trajectory maps.

Bilotti, Frank; Connors, Chris; Suppe, John

1993-01-01

269

Is there uniformitarian or catastrophic tectonics on Venus?  

Science.gov (United States)

The distribution and modification of craters on Venus favors a near global, volcanic resurfacing event about 500 Myrs ago. Such an event indicates that the tectonic evolution of Venus was catastrophic rather than uniformitarian. The creation of a global, single-plate lithosphere on Venus about 500 Myrs ago can explain a variety of tectonic features on Venus that are not consistent with the thin lithosphere required by a uniformitarian hypothesis. A lithosphere on Venus that has thickened for 500 Myrs has a present thickness of about 300 km whereas steady-state heat loss from Venus requires a mean lithospheric thickness near 40 km. A thick lithosphere on Venus can support the high plateaus (elevations of 3-4 km) and mountain belts (up to 9 km) using the same isostatic compensation concepts applicable to the earth. If a thick lithosphere is thinned by a mantle plume, elevation is caused by thermal isostasy. The elevation due to the thinning of a 300 km thick lithosphere is about 3 km. Thus the domal elevation of Beta Regio can be explained by the same mechanism responsible for the elevation of the Hawaiian Swell. While the broad highland plateaus on Venus may be associated with thermal isostasy, the mountain belts in Ishtar Terra clearly cannot be. The high topography of Freyja Montes is almost certainly associated with underthrusting and the likely compensation mechanism is Airy isostasy associated with a thickened crust. With a density contrast delta, of 500 kg m(exp -3) an elevation of 9 km requires a crustal thickening of about 70 km. With a thick lithosphere there is no difficulty in supporting such a thick crust.

Turcotte, Donald L.

1993-01-01

270

The evolution of hotspots on Earth and Venus  

International Nuclear Information System (INIS)

Full text: Selected hotspots on Earth and Venus, sister planet to Earth due to similarities in size, gravity and bulk composition, are analyzed. Despite those similarities, several differences, such as the lack of water, the absence of plate tectonics, and a low degree of erosion affect Venusian mantle plumes with respect to their structure and dimension, their surface manifestation and their role in the heat budget of the planet Venus. Special attention will be paid to the magmatic output over the time. (author)

271

Can Venus and Mars Be Made Habitable?  

Science.gov (United States)

This activity is about planetary climate. Once familiar with the factors that determine a planet's surface temperature, learners will use an interactive spreadsheet model of a planet's atmosphere to determine if greenhouse gases, luminosity of the source, the distance of the planet from the source and the albedo of the planet can be manipulated so that the average surface temperature on Mars or Venus could support human life. Learners will then be asked to make some conclusions about these methods and suggest improvements for the spreadsheet model (see related resources for link to this model). The activity requires use of Microsoft Excel software. This is Activity D in the fourth module, titled "How do Atmospheres Affect Planetary Temperatures?," of "Earth Climate Course: What Determines a Planet's Climate?."

272

Waves in a Venus general circulation model  

Science.gov (United States)

in the Venus atmosphere are numerically investigated by extending a work of Sugimoto et al. (2014). Fast superrotating zonal flow of 120 m s-1 at the equator is reproduced and maintained by solar heating for more than 10 Earth years. The meridional distribution of the obtained fast zonal flow is quite consistent with observations at the cloud levels. In the cloud layer, baroclinic waves develop continuously with a life cycle of ~25 Earth days at midlatitudes, using available potential energy derived from a baroclinically unstable basic state. Rossby waves observed at the cloud top are generated by the baroclinic waves and induce spatio-temporal variation of the superrotation with amplitude larger than 25 m s-1. Further, Kelvin waves with a period of ˜ 6.2 days appear in the equatorial region below ~50 km. Momentum and heat transports produced by these waves are discussed.

Sugimoto, Norihiko; Takagi, Masahiro; Matsuda, Yoshihisa

2014-11-01

273

Character of the thermal emission from venus  

International Nuclear Information System (INIS)

Images of the thermal infrared emission from 10.6 to 12.6 mm from the earth-facing hemisphere of Venus were made from earth on each available opportunity over a 26-day period in 1977 and a 106-day period in 1978--1979, using a 1.5 m telescope. Compact, variable thermal features exist at latitudes higher than about 500, some of which repeat at 5-day intervals. No such repeatability is observed for features near the equator. Day-to-day variations in limb darkening and the contrast of high latitude features appear to differ in the conjunction and post-conjunction images. A strong, solar-fixed component of the emission exists and exhibits wave number 1, 2, and 4 components. The thermal tides provide constraints upon the atmosphere structure. The solar-fixed structure shows significant asymmetries with respect to the equator

274

An Encounter between the Sun and Venus  

CERN Multimedia

The astronomical event of the year will take place on Tuesday, 8 June, when Venus transits across the disk of the sun. In the framework of CERN's 50th anniversary celebrations, the CERN Astronomy Club and the Orion Club invite you to attend their observation of the event on the car park of the Val-Thoiry shopping centre (France) between 7.15 a.m. and 1.30 p.m. Various instruments will be set up in a special tent so that the event can be observed without any risk of damage to the eyes. As the observation of this astronomical event will depend on the weather forecast, confirmation of the above arrangements will be given on the 50th anniversary website the day before.

2004-01-01

275

Pioneer Venus Orbiter Electron Temperature Probe  

Science.gov (United States)

The Orbiter Electron Temperature Probe (OETP) instrumentation and measurement technique has been designed to perform in-situ measurements of electron temperature and electron and ion density in the ionosphere of Venus. Adaptive sweep voltage circuitry continuously tracks the changing electron temperature and spacecraft potential while auto-ranging electrometers adjust their gain in response to the changing plasma density. Control signals used in the instrument to achieve this automatic tracking provide a continuous monitor of the ionospheric parameters without telemetering each volt-ampere curve. Internal data storage permits high data rate sampling of selected raw characteristic curves for low rate transmission to earth. These curves are used to verify or correct the inflight processed data. Sample in orbit measurements are presented to demonstrate instrument performance.

Krehbiel, J. P.; Brace, L. H.; Theis, R. F.; Cutler, J. R.; Pinkus, W. H.; Kaplan, R. B.

1980-01-01

276

Impact ionization effects on Pioneer Venus Orbiter  

Science.gov (United States)

Anomalies observed during periapsis passages of the Pioneer Venus Orbiter are discussed. Data from the Langmuir Probe Experiment show a change in the collected current at periapsis which correlates well with the neutral atmospheric density. The data can be qualitatively explained by the secondary emission of electrons from the spacecraft and from the probe caused by the impact of neutral CO2 molecules, the dominant neutral constituent at periapsis altitude of 150 km. Impact energy is 22 eV. The probe showing this effect is mounted on the leading surface of the spacecraft which is exposed to the streaming neutral gas. As the probe voltage is swept, contributions to the current from the ionospheric plasma and from the secondary electrons can be distinguished. The observed current/voltage behavior suggests a probe-barrier interaction.

Whipple, E. C.; Brace, L. H.; Parker, L. W.

1983-01-01

277

Mars, Venus and Gray: Gender Communication  

Directory of Open Access Journals (Sweden)

Full Text Available This research tests the propositions relating to gender communication by Gray (1992 in his book titled “Men are from Mars, Women are from Venus” This book has been the source of gender-related controversy since its publication. The sample consisted of 182 executives and non-executives (73 males and 109 females. T-test results show that out of 23 statements made by Gray (1992, only 8 were supported, 10 were not supported and 5 were actually true for the opposite gender. This research is indeed timely in that it addresses the long disservice to women. So the way forward into the future would be to train people on how to communicate better by making them aware that different people have different preferences and styles of communication, rather than essentializing and gender-stereotyping.

Kamarul Zaman Ahmad

2010-03-01

278

Venus radar mapper attitude reference quaternion  

Science.gov (United States)

Polynomial functions of time are used to specify the components of the quaternion which represents the nominal attitude of the Venus Radar mapper spacecraft during mapping. The following constraints must be satisfied in order to obtain acceptable synthetic array radar data: the nominal attitude function must have a large dynamic range, the sensor orientation must be known very accurately, the attitude reference function must use as little memory as possible, and the spacecraft must operate autonomously. Fitting polynomials to the components of the desired quaternion function is a straightforward method for providing a very dynamic nominal attitude using a minimum amount of on-board computer resources. Although the attitude from the polynomials may not be exactly the one requested by the radar designers, the polynomial coefficients are known, so they do not contribute to the attitude uncertainty. Frequent coefficient updates are not required, so the spacecraft can operate autonomously.

Lyons, D. T.

1986-01-01

279

Nanoscale organization of ?2-adrenergic receptor-Venus fusion protein domains on the surface of mammalian cells  

International Nuclear Information System (INIS)

Adrenergic receptors are a key component of nanoscale multiprotein complexes that are responsible for controlling the beat rate in a mammalian heart. We demonstrate the ability of near-field scanning optical microscopy (NSOM) to visualize ?2-adrenergic receptors (?2AR) fused to the GFP analogue Venus at the nanoscale on HEK293 cells. The expression of the ?2AR-Venus fusion protein was tightly controlled using a tetracycline-induced promoter. Both the size and density of the observed nanoscale domains are dependent on the level of induction and thus the level of protein expression. At concentrations between 100 and 700 ng/ml of inducer doxycycline, the size of domains containing the ?2AR-Venus fusion protein appears to remain roughly constant, but the number of domains per cell increase. At 700 ng/ml doxycycline the functional receptors are organized into domains with an average diameter of 150 nm with a density similar to that observed for the native protein on primary murine cells. By contrast, larger micron-sized domains of ?2AR are observed in the membrane of the HEK293 cells that stably overexpress ?2AR-GFP and ?2AR-eYFP. We conclude that precise chemical control of gene expression is highly advantageous for the use ?2AR-Venus fusion proteins as models for ?2AR function. These observations are critical for designing future cell models and assays based on ?2AR, since the receptor biology is consistent with a relatively low density of nanoscale receptor domains.

280

Transits of Venus and Colonial India  

Science.gov (United States)

Astronomical expeditions during the colonial period had a political and national significance also. Measuring the earth and mapping the sky were activities worthy of powerful and power- seeking nations. Such was the sanctity of global astronomical activity that many other agendas could be hidden under it. An early astronomy-related expedition turned out to be extremely beneficial, to botany. The expedition sent by the French Government in 1735 to South America under the leadership of Charles Marie de la Condamine (1701--1774) ostensibly for the measurement of an arc of the meridian at Quito in Ecuador surreptitiously collected data that enabled Linnaeus to describe the genus cinchona in 1742. When the pair of transits of Venus occurred in 1761 and 1769, France and England were engaged in a bitter rivalry for control of India. The observation of the transits became a part of the rivalry. A telescope presented by the British to a South Indian King as a decorative toy was borrowed back for actual use. Scientifically the transit observations were a wash out, but the exercise introduced Europe to details of living Indian tradition of eclipse calculations. More significantly, it led to the institutionalization of modern astronomy in India under the auspices of the English East India Company (1787). The transits of Venus of 1874 and 1882 were important not so much for the study of the events as for initiating systematic photography of the Sun. By this, Britain owned most of the world's sunshine, and was expected to help European solar physicists get data from its vast Empire on a regular basis. This and the then genuinely held belief that a study of the sun would help predict failure of monsoons led to the institutionalization of solar physics studies in India (1899). Of course, when the solar physicists learnt that solar activity did not quite determine rainfall in India, they forgot to inform the Government.

Kochhar, Rajesh

2012-09-01

 
 
 
 
281

Atmospheric Entry Studies for Venus Missions: 45 Sphere-Cone Rigid Aeroshells and Ballistic Entries  

Science.gov (United States)

The present study considers direct ballistic entries into the atmosphere of Venus using a 45deg sphere-cone rigid aeroshell, a legacy shape that has been used successfully in the past in the Pioneer Venus Multiprobe Mission. For a number of entry mass and heatshield diameter combinations (i.e., various ballistic coefficients) and entry velocities, the trajectory space in terms of entry flight path angles between skip out and -30deg is explored with a 3DoF trajectory code, TRAJ. From these trajectories, the viable entry flight path angle space is determined through the use of mechanical and thermal performance limits on the thermal protection material and science payload; the thermal protection material of choice is entry-grade carbon phenolic, for which a material thermal response model is available. For mechanical performance, a 200 g limit is placed on the peak deceleration load experienced by the science instruments, and 10 bar is assumed as the pressure limit for entry-grade carbon-phenolic material. For thermal performance, inflection points in the total heat load distribution are used as cut off criteria. Analysis of the results shows the existence of a range of critical ballistic coefficients beyond which the steepest possible entries are determined by the pressure limit of the material rather than the deceleration load limit.

Prabhu, Dinesh K.; Spilker, Thomas R.; Allen, Gary A., Jr.; Hwang, Helen H.; Cappuccio, Gelsomina; Moses, Robert W.

2013-01-01

282

76 FR 20802 - Culturally Significant Object Imported for Exhibition Determinations: “The Capitoline Venus  

Science.gov (United States)

...Significant Object Imported for Exhibition Determinations: ``The Capitoline Venus'' SUMMARY: Notice is hereby given of the following...determine that the object to be included in the exhibition ``The Capitoline Venus,'' imported from abroad for temporary...

2011-04-13

283

Topography of Venus and earth - A test for the presence of plate tectonics  

Science.gov (United States)

Comparisons of earth and Venus topography by use of Pioneer/Venus radar altimetry are examined. Approximately 93% of the Venus surface has been mapped with a horizontal resolution of 200 km and a vertical resolution of 200 m. Tectonic troughs have been indicated in plains regions which cover 65% of Venus, and hypsometric comparisons between the two planets' elevation distributions revealed that while the earth has a bimodal height distribution, Venus displays a unimodal configuration, with 60% of the planet surface within 500 m of the modal planet radius. The effects of mapping the earth at the same resolution as the Venus observations were explored. Continents and oceans were apparent, and although folded mountains appeared as high spots, no indications of tectonic activity were discernible. A NASA Venus Orbiting Imaging radar is outlined, which is designed to detect volcanoes, folded mountain ranges, craters, and faults, and thereby allow definition of possible plate-tectonic activity on Venus.

Head, J. W.; Yuter, S. E.; Solomon, S. C.

1981-01-01

284

Three-dimensional thermal structure of the South Polar Vortex of Venus  

Science.gov (United States)

We have analyzed thermal infrared images provided by the VIRTIS-M instrument aboard Venus Express (VEX) to obtain high resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. The maps investigate three different dynamical configurations of the polar vortex including its classical dipolar shape, a regularly oval shape and a transition shape between the different configurations of the vortex. We apply the atmospheric model described by García Muñoz et al. (2013) and a variant of the retrieval algorithm detailed in Grassi et al. (2008) to obtain maps of temperature over the Venus south polar region in the quoted altitude range. These maps are discussed in terms of cloud motions and relative vorticity distribution obtained previously (Garate-Lopez et al. 2013). Temperature maps retrieved at 55 – 63 km show the same structures that are observed in the ~5 µm radiance images. This altitude range coincides with the optimal expected values of the cloud top altitude at polar latitudes and magnitudes derived from the analysis of ~5 µm images are measured at this altitude range. We also study the imprint of the vortex on the thermal field above the cloud level which extends up to 80 km. From the temperature maps, we also study the vertical stability of different atmospheric layers. The cold collar is clearly the most statically stable structure at polar latitudes, while the vortex and subpolar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex at 55-63 km exhibit lower values of static stability than their immediate surroundings.ReferencesGarate-Lopez et al. Nat. Geosci. 6, 254–257 (2013).García Muñoz et al. Planet. Space Sci. 81, 65–73 (2013).Grassi, D. et al. J. Geophys. Res. 113, 1–12 (2008).AcknowledgementsWe thank ESA for supporting Venus Express, ASI, CNES and the other national space agencies supporting VIRTIS on VEX and their principal investigators G. Piccioni and P. Drossart. This work was supported by projects AYA2012-36666 with FEDER support, PRICI-S2009/ESP-1496, Grupos Gobierno Vasco IT-765-13 and by UPV/EHU through program UFI11/55. IGL and AGM acknowledge ESA/RSSD for hospitality and access to ‘The Grid’ computing resources.

Hueso, Ricardo; Garate-Lopez, Itziar; Garcia-Muñoz, Antonio; Sánchez-Lavega, Agustín

2014-11-01

285

Status report of the 28 GHz superconducting electron cyclotron resonance ion source VENUS (invited)  

International Nuclear Information System (INIS)

The superconducting versatile electron cyclotron resonance (ECR) ion source for nuclear science (VENUS) is a next generation superconducting ECR ion source designed to produce high-current, high-charge-state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the rare isotope accelerator (RIA) front end, where the goal is to produce intense beams of medium-charge-state ions. Example beams for the RIA accelerator are 15 p ?A of Kr17+(260 e ?A), 12 p ?A of Xe20+ (240 e ?A of Xe20+), and 8 p ?A of U28+(230 e ?A). To achieve these high currents, VENUS has been optimized for operation at 28 GHz, reaching maximal confinement fields of 4 and 3 T axially and over 2.2 T on the plasma chamber wall radially. After a commissioning phase at 18 GHz, the source started the 28 GHz operation in the summer of 2004. During that ongoing 28 GHz commissioning process, record ion-beam intensities have been extracted. For instance, measured extracted currents for the low to medium charge states were 270 e ?A of Xe27+ and 245 e ?A of Bi29+, while for the higher charge states 15 e ?A of Xe34+, 15 e ?A of Bi41+, and 0.5 e ?A of Bi50+ could be produced. Results from the ongoing 28 GHz commissioning as well as results using double-frequency heating with 18 and 28 GHz for oxygen and xenon are presented. The effect onon are presented. The effect of the minimum B field on the ion source performance has been systematically measured for 18 and 28 GHz. In both cases the performance peaked at a minimum B field of about 80% of the resonance field. In addition, a strong dependence of the x-ray flux and energy on the minimum B field value was found

286

European Venus Explorer (EVE): an in-situ mission to Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The European Venus Explorer (EVE) mission was proposed to the European Space Agency in 2007, as an M-class mission under the Cosmic Vision Programme. Although it has not been chosen in the 2007 selection round for programmatic reasons, the EVE mission may serve as a useful reference point for future missions, so it is described here. It consists of one balloon platform floating at an altitude of 50-60 km, one descent probe provided by Russia, and an orbiter with a polar orbit which will relay...

Chassefiere, E.; Korablev, O.; Imamura, T.; Baines, Kh; Wilson, Cf; Titov, Dv; Aplin, Kl; Balint, T.; Blamont, Je; Cochrane, Cg; Ferencz, C.; Ferri, F.; Gerasimov, M.; Leitner, Jj; Lopez-moreno, J.

2009-01-01

287

Isostasy Models and Correlations of Geoid and Topography Data for Characteristic Highlands on Venus  

Science.gov (United States)

We have used the newest solution for the Venus geopotential, incorporating tracking data from the circularized orbit of Magellan, along with global Venus topography data to study correlations of geoid and topography variations in several regions characteristic of the principal classes of highlands found on Venus.

Kucinskas, A.; Turcotte, D.

1994-01-01

288

Columbus State University Global Observation and Outreach for the 2012 Transit of Venus  

Science.gov (United States)

Faculty, staff and students from Columbus State University’s (CSU’s) Coca-Cola Space Science Center presented a webcast of the 2012 Transit of Venus from three continents to a global audience of 1.4 million unique viewers. Team members imaged the transit with telescopes using white-light, hydrogen-alpha, and calcium filters, from Alice Springs, Australia; the Gobi Desert, Mongolia; Bryce Canyon, UT; and Columbus, GA. Images were webcast live during the transit in partnership with NASA’s Sun-Earth Day program, and Science Center staff members were featured on NASA TV. Local members of the public were brought in for a series of outreach initiatives, in both Georgia and Australia, before and during the transit. The data recorded from the various locations have been archived for use in demonstrating principles such as the historical measurement of the astronomical unit.

Perry, Matthew; McCarty, C.; Bartow, M.; Hood, J. C.; Lodder, K.; Johnson, M.; Cruzen, S. T.; Williams, R. N.

2013-01-01

289

Pioneer Venus data analysis for the retarding potential analyzer  

Science.gov (United States)

This report describes the data analysis and archiving activities, analysis results, and instrument performance of the orbiter retarding potential analyzer (ORPA) flown on the Pioneer Venus Orbiter spacecraft during the period, Aug. 1, 1988 to Sept. 30, 1993. During this period, the periapsis altitude of the Orbiter spacecraft descended slowly from 1900 km altitude, at which altitude the spacecraft was outside the Venus ionosphere, to approximately 130 km altitude in Oct. 1992 at which time communication with the spacecraft ceased as a result of entry of the spacecraft into the Venus atmosphere. The quantity of ORPA data returned during this reporting period was greatly reduced over that recovered in the previous years of the mission because of the reduced power capability of the spacecraft, loss of half of the onboard data storage, and partial failure of the ORPA. Despite the reduction in available data, especially ionospheric data, important scientific discoveries resulted from this extended period of the Pioneer Venus mission. The most significant discovery was that of a strong solar cycle change in the size of the dayside ionosphere and the resulting shutoff of flow of dayside ions into the nightside hemisphere. The large, topside O+ F2 ionospheric layer observed during the first three years of the Pioneer Venus mission, a period of solar cycle maximum activity, is absent during the solar cycle minimum activity period.

Knudsen, William C.

1993-01-01

290

The case for a deep-atmospheric in situ mission to address the highest priority Decadal Survey questions for Venus (Invited)  

Science.gov (United States)

Current understanding of Venus lags behind that for Mars, with a major disparity of information concerning noble and trace gases and the small scale surface processes needed for comparative studies of terrestrial planet evolution. Despite global surface mapping by Magellan, discoveries by Venera landers, and ongoing atmospheric observations by the Venus Express (VEx) orbiter, significant questions about Venus remain unanswered. To place Venus into its proper context with respect to Mars and Earth, it is necessary to obtain new measurements that address top issues identified in the National Research Council (NRC) Solar System Decadal Survey: (1) evolution of the atmosphere, history of climate, and evidence of past hydrologic cycles; (2) history of volatiles and sedimentary cycles; and (3) planetary surface evolution. To answer these questions, new measurements are needed. First and foremost, in situ noble gas measurements are needed to constrain solar system formation and Venus evolution. In particular, the isotopic ratios of Xe and Kr can provide unique insights into planetary accretion. Isotopic measurements of nitrogen (15N/14N) will place important constraints on atmospheric loss processes. Current knowledge of this ratio has a substantial uncertainty of ×20%. VEx observations of hydrogen isotopes indicate the D/H ratio above the clouds is substantially greater than measured by Pioneer Venus, and varies with height. High precision measurements of the vertical distribution of the D/H isotopic ratio below the cloud layers will provide constraints on models of the climate history of water on Venus. The majority of atmospheric mass is located below the clouds. Current data suggest intense interaction among atmospheric gases down to the surface. The haze within the cloud region of unknown composition plays a central role in the radiative balance. Photochemically-derived species (H2SO4, OCS, CO, Sn) are subjected to thermochemical reactions below the clouds, especially within 30 km of the surface. Competing temperature-pressure dependent reactions and atmospheric circulation may cause vertical and latitudinal gradients of chemically-active trace gases (e.g., SO2, H2S, OCS, CO). Measurements of the chemical composition of the near-surface atmosphere can be used to evaluate the stability of primary and secondary minerals and can help to understand chemistry of atmosphere-surface interactions. However, concentrations of many trace species have never been measured below ~30 km, and multiple in situ measurements are required to evaluate chemical processes and cycles of volatiles, which can only be accomplished with deep entry probes. Current lack of understanding about Venus not only limits our understanding of evolutionary pathways Earth could experience, but also suggests that we are ill-equipped to understand the evolution of star systems with similar-sized planets.

Atreya, S. K.; Garvin, J. B.; Glaze, L. S.; Campbell, B. A.; Fisher, M. E.; Flores, A.; Gilmore, M. S.; Johnson, N.; Kiefer, W. S.; Lorenz, R. D.; Mahaffy, P. R.; Ravine, M. A.; Webster, C. R.; Zolotov, M. Y.

2013-12-01

291

The 28 GHZ, 10 KW, CW Gyrotron Generator for the VENUS ECR Ion Source at LBNL  

International Nuclear Information System (INIS)

The VIA-301 HeatwaveTM gyrotron generator was specifically designed to meet the requirements of the Venus ECR Ion Source at the Lawrence Berkeley National Laboratory (LBNL). VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end].This VIA-301 HeatwaveTM gyrotron system provides 100 watts to 10 kW continuous wave (CW) RF output at 28 GHz. The RF output level is smoothly controllable throughout this entire range. The power can be set and maintained to within 10 watts at the higher power end of the power range and to within 30 watts at the lower power end of the power range. A dual directional coupler, analog conditioning circuitry, and a 12-bit analog input to the embedded controller are used to provide a power measurement accurate to within 2%. The embedded controller completes a feedback loop using an external command set point for desired power output. Typical control-loop-time is on the order of 500 mS. Hard-wired interlocks are provided for personnel safety and for protection of the generator system. In addition, there are software controlled interlocks for protection of the generator from high ambient temperature, high water temperature, and other conditions that would affature, and other conditions that would affect the performance of the generator or reduce the lifetime of the gyrotron. Cooling of the gyrotron and power supply is achieved using both water and forced circulation of ambient air. Water-cooling provides about 80% of the cooling requirement. Input power to the generator from the prime power line is less than 60 kW at full power. The HeatwaveTM may be operated locally via its front panel or remotely via either RS-232 and/or Ethernet connections. Through the RS-232 the forward power, the reflected power, the interlock status and crucial operating parameters are transmitted and tied into the VENUS PLC control system.The paper describes the gyrotron system, control software, the user interface, the main system parameter, and performance in respect to output power stability

292

The 28 GHZ, 10 KW, CW Gyrotron Generator for the VENUS ECR Ion Source at LBNL  

Science.gov (United States)

The VIA-301 Heatwave™ gyrotron generator was specifically designed to meet the requirements of the Venus ECR Ion Source at the Lawrence Berkeley National Laboratory (LBNL). VENUS (Versatile ECR ion source for NUclear Science) is a next generation superconducting ECR ion source, designed to produce high current, high charge state ions for the 88-Inch Cyclotron at the Lawrence Berkeley National Laboratory. VENUS also serves as the prototype ion source for the RIA (Rare Isotope Accelerator) front end [1]. This VIA-301 Heatwave™ gyrotron system provides 100 watts to 10 kW continuous wave (CW) RF output at 28 GHz. The RF output level is smoothly controllable throughout this entire range. The power can be set and maintained to within 10 watts at the higher power end of the power range and to within 30 watts at the lower power end of the power range. A dual directional coupler, analog conditioning circuitry, and a 12-bit analog input to the embedded controller are used to provide a power measurement accurate to within 2%. The embedded controller completes a feedback loop using an external command set point for desired power output. Typical control-loop-time is on the order of 500 mS. Hard-wired interlocks are provided for personnel safety and for protection of the generator system. In addition, there are software controlled interlocks for protection of the generator from high ambient temperature, high water temperature, and other conditions that would affect the performance of the generator or reduce the lifetime of the gyrotron. Cooling of the gyrotron and power supply is achieved using both water and forced circulation of ambient air. Water-cooling provides about 80% of the cooling requirement. Input power to the generator from the prime power line is less than 60 kW at full power. The Heatwave™ may be operated locally via its front panel or remotely via either RS-232 and/or Ethernet connections. Through the RS-232 the forward power, the reflected power, the interlock status and crucial operating parameters are transmitted and tied into the VENUS PLC control system. The paper describes the gyrotron system, control software, the user interface, the main system parameter, and performance in respect to output power stability.

Marks, M.; Evans, S.; Jory, H.; Holstein, D.; Rizzo, R.; Beck, P.; Cisto, B.; Leitner, D.; Lyneis, C. M.; Collins, D.; Dwinell, R. D.

2005-03-01

293

ENA diagnostic of the solar wind interaction with Mars and Venus  

Science.gov (United States)

Charge - exchange of the solar wind ions flowing around non-magnetized Mars and Venus on their exospheres results in hydrogen energetic neutral atom (ENA) emissions. Accelerated planetary ions may also experience charge - exchange resulting in planetary ENAs, mainly oxygen. The ENAs carry information on the ion distribution functions integrated over the line-of-sight and are used for remote sensing of the original plasma populations. The ASPERA-3/4 instruments (Analyzer of Space Plasmas and Energetic Atoms) onboard Mars Express and Venus Express missions performed the first-ever measurements of ENAs from these bodies in the energy range 100 eV - 10 keV. ENAs are mostly emitted by the magnetospheath plasma flowing around the induced magnetosphere. Due to lower gravity the Martian exosphere extends further in the magnetosheath than at Venus that makes Mars a “brighter ENA source”. We thus focus mostly on Mars and only briefly discuss ENA observations at Venus. ENA emissions from an elementary emitting volume in the magnetosheath are highly anisotropic and occur along the tangential line to the stream-line in this point. That makes impossible to obtain a global ENA image of the object from a single vantage point contrary to, for example, “classical” ENA imaging of the terrestrial ring current. At Mars the statistically obtained emission pattern shows an increase in the ENA flux perpendicular to the sun direction resembling a thick layer or a wall. The emissions coming mostly from the sub-solar point show an increase in the direction opposite to the convective electric field indicating the induced magnetosphere boundary is not cylindrically symmetric and closer to planet in this direction. Measurements of ENAs turned out to be an effective way to reveal the global dynamics of an induced magnetosphere. Arrival of an interplanetary shock to Mars and the associated compression of the induced magnetosphere are clearly detected as an abrupt termination of the ENA signal because the ENA wall suddenly moved away from the spacecraft. When the spacecraft stays sufficiently long inside the ENA wall, oscillations of the ENA signal with a period of 30 sec - few min (~0.01 Hz) can be observed. The oscillations of the similar frequency are observed in the electron and ion fluxes in the magnetosheath as well as magnetic field. Their physics is not understood. Mars Express/ASPERA-3 detected a slight increase of the ENA emissions above the magnetic anomalies. It may be related to the increase of the neutral densities above these regions. Contrary to the predictions, Mars Express/ASPERA-3 did not detect any oxygen ENAs. That allowed to provide upper limits for the hydrogen exospheric densities which turned out to be much lower at the solar minimum than expected. Finally, we introduce a few “exotic” ideas of using ENAs for studies the near-Venus and near-Mars space. Using ENAs backscattered from the atmosphere one may obtain global precipitating maps. Using the neutral solar wind passing through the upper atmosphere at the terminate region, one may realize neutral solar wind occultation geometry and use the ENA signal variation for the upper atmosphere profiling.

Barabash, Stas

294

Volcano-rift interaction on Venus: initial results from the Beta-Atla-Themis region.  

Science.gov (United States)

Extensional deformation and volcanism are widespread and geographically related processes on the surface of Venus (e.g. Head et al., 1992; Solomon et al., 1992). We report the initial results of an ongoing study on the interaction between fracture belts (chasmata and fossae) and large to intermediate-size volcanoes on Venus. The initial work focused in Beta-Atla-Themis, a region centered at ˜ 250o of longitude that covers ˜ 20 percent of the surface of the planet in which concentration of volcanic centers and fracture belts exceeds the global mean density (e.g. Crumpler et al., 1993). We carried out a survey of the volcanic features located in and close to fracture belts using existing volcano databases (Crumpler and Aubele, 2000) updated during this initial stage of our study through the analysis of full-resolution Magellan radar images for the studied region. We identified over a hundred volcanic features of different size and type (large volcanoes, intermediate-size volcanoes, steep-side domes and modified or fluted edifices) located in or near fracture belts. In this initial work, we have also established the time relationship that exist between each volcanic feature and the fracture belts and found that volcanic edifices predate, postdate or develop contemporaneously to extensional fracturing. Detailed structural mapping of locations where extensional fracturing and the formation of volcanoes is related is being carried out. In these geological settings the fracture patterns resulting from the interaction between both processes can help to constrain the different processes that operate during volcano growth (i.e. dike intrusion, chamber inflation, volcanic sagging and volcanic spreading) and its interaction with the regional stress fields responsible for the fracture belts. References: - Crumpler L.S. and J.C. Aubele (2000). Volcanism on Venus. In Encyclopedia of volcanoes, (Sigurdsson, H, B. Houghton, S.R. McNutt, H. Rymer, J. Stix, eds), p.727- 770. Academic Press. - Crumpler, L.S., J.W. Head and J.C. Aubele (1993). Relation of mayor volcanic center concentration on Venus to global tectonic patterns. Science, 261, p.591-595. - Head, J.W., L.S. Crumpler, J.C. Aubele, J.E. Guest and R.S. Saunders (1992). Venus volcanism: Classification of volcanic features and structures, associations, and global 1 distribution from Magellan data. J. Geophys. Res., 97, p.13153-13197. - Solomon S.C., S.E. Smrekar, D.L. Bindschadler, R.E. Grimm, W.M. Kaula, G.E. McGill, R.J. Phillips, R.S. Saunders, G. Schubert, S.W, Squyres and E.R. Stofan (1992). Venus tectonics: An overview of Magellan observations. J. Geophys. Res., 97, p.13199-13255. 2

Lopez, I.; Martin-Gonzalez, F.; Marquez, A.; de Pablo, M. A.; Carreno, F.

295

RAVEN - High-resolution Mapping of Venus within a Discovery Mission Budget  

Science.gov (United States)

It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission (RCM) to map Venus in an economical, highly capable, and reliable way. RCM relies on a C-band SAR that can be tuned to generate images at a wide variety of resolutions and swath widths, ranging from ScanSAR mode (broad swaths at 30-m resolution) to strip-map mode (resolutions as fine as 3 m), as well as a spotlight mode that can image patches at 1-m resolution. In particular, the high-resolution modes allow the landing sites of previous missions to be pinpointed and characterized. Repeat-pass interferometric SAR (InSAR) and stereo radargrammetry provide options for constraining topography to better than 100-m horizontal and 10-m vertical resolution. InSAR also provides the potential for detecting surface deformation at centimeter precision. Performing InSAR requires precise knowledge and control of the orbital geometry, and for this reason a 600-km circular polar orbit is favored. This configuration causes the equatorial nadir point to move ~9 km per orbit. Considering both ascending and descending passes, the spacecraft will pass over every point on the planet in half a Venus day (~4 Earth months). The ability to transmit data back to Earth via the Deep Space Network is the primary limiting factor on the volume of data that can be collected. Our current estimates indicate that within an imaging cycle of one Venus day we can image 20-30 percent of the planet at 20-30-m resolution and several percent at 3-5 m resolution. These figures compare favorably to the coverage provided by recent imaging systems orbiting Mars. Our strategy calls for the first cycle of coverage to be devoted to imaging large geographic areas (e.g., Thetis Regio) at 20-30-m resolution with interleaved observation of pre-selected targets at high resolution. The second cycle will include additional imaging, but the focus will be repeat-pass coverage to obtain topography for a significant fraction of the first-cycle targets. A focus of the third cycle will be InSAR-based deformation studies of selected areas. All components of the spacecraft are expected to remain operational well beyond the nominal mission time, so global mapping at 10 m or better resolution during an extended mission is conceivable. RAVEN will allow us to determine both the broad framework of the planet’s geologic history (e.g, uniformitarian versus catastrophic evolution) and the nature of current geologic activity. It will substantially advance our understanding of Venus and reveal details, issues, and further questions that will benefit future site-specific missions such as probes and landers. Current RAVEN science team members are Buck Sharpton (PI), Rudi Gens, Rebecca Ghent, Martha Gilmore, Robert Grimm, Robert Herrick, Catherine Johnson, Patrick McGovern, Franz Meyer, Peter Mouginis-Mark, Jeff Plaut, David Sandwell, Mark Simons, and Sean Solomon.

Sharpton, V. L.; Herrick, R. R.; Rogers, F.; Waterman, S.

2009-12-01

296

Venus night side measurements of winds at 115 km altitude from NO bright patches tracking.  

Science.gov (United States)

N and O atoms produced by photo-dissociation of CO2 and N2 on the day side of Venus are transported to the night side in the thermospheric circulation. When the air parcel is descending, the recombination N+O? NO produces the famous ? and ? bands of NO emission. Pioneer Venus (1978) suggested that the statistical center of the emission is off from the anti-solar point, about one- two hours in Local time after midnight. This is confirmed from SPICAV/VEX results, and the explanation generally accepted is the influence of retrograde super rotation. However, the emission takes place at 115 km, while VIRTIS/VEX, with maps of O2 emission (peak altitude 95 km) in the night side of Venus (recombination of O+O coming from the day side), has shown that the maximum of emission is statistically centered on the antisolar point. Therefore, there is no influence of super-rotation at 95 km. One way to explain this paradox is that the cause of the super rotation is different at 115 km and in the lower atmosphere. Alternately, some gravity waves could propagate from below, crossing the altitude 95 km with minimal interaction, and breaking around 115 km, depositing their momentum. Another consideration is that the altitude of N2 photo-dissociation is higher in the thermosphere than CO2, therefore the thermospheric circulation pattern may be different for the transport of N atoms, and O atoms. We have started building maps of the NO emission by moving around the spacecraft along its orbit on the night side. The idea is that NO emission is concentrated generally in rather well defined patches of light. Therefore, by comparing maps taken at 1 hour or 24 hr interval, we can make a "bright patch tracking", and derive directly the velocity of the moving air parcel containing N and O (we are aware that a part of the motion could be due to a phase shift of a gravity wave, if it has some influence on the NO emission). Preliminary results from this exercise with Venus Express will be presented and discussed.

Bertaux, Jean-Loup

2014-05-01

297

The 825-1110 angstroms EUV spectrum of Venus.  

Science.gov (United States)

On 15 August 1994 we launched the EUVS sounding rocket payload to observe the 825-1110 angstrom region of Venus's far ultraviolet airglow spectrum. The EUVS telescope/spectrograph obtained good data at five times higher spectral resolution than was previously available in the far ultraviolet. We present these data and compare our results to those obtained by the Galileo UVS and Venera 11/12 UV spectrophotometers. We identify several new spectral emission features, including both singly ionized nitrogen and molecular nitrogen in Venus's spectrum. We also see evidence for electron-impact-induced emission from CO. Finally, the EUVS data indicate that the "Ar" emissions detected in Venus's far ultraviolet spectrum by Venera 11/12 spectrophotometers are in fact not due to argon, thus eliminating the discrepancy between in situ and remote sensing measurements. PMID:11539409

Stern, S A; Slater, D C; Gladstone, G R; Wilkenson, E; Cash, W C; Green, J C; Hunten, D M; Owen, T C; Paxton, L

1996-07-01

298

The upper atmosphere of Venus during morning conditions  

Science.gov (United States)

The structure and composition of the Venus upper atmosphere between 130- and 650-km altitude were measured for a solar zenith angle of approximately 60 deg by the neutral gas mass spectrometer on board the Pioneer Venus multiprobe bus. Below 180 km a wavelike structure is quite evident in the CO2 and He number density profiles. For altitudes above 100 km a one-dimensional model of the Venus upper atmosphere during morningside conditions (MS model) is presented. Number densities at 150-km altitude are as follows: CO2 equals 4.2 x 10 to the 9th, N2 equals 1.1 x 10 to the 9th, CO equals 2.8 x 10 to the 9th, and He equals 4.8 x 10 to the 6th per cu cm. The homopause altitudes for N2 and He are at 136 and 130 km, respectively.

Von Zahn, U.; Fricke, K. H.; Hunten, D. M.; Krankowsky, D.; Mauersberger, K.; Nier, A. O.

1980-01-01

299

Venus atmospheric circulation - Observations and implications of the thermal structure  

Science.gov (United States)

Thermal structure data obtained by Pioneer Venus (PV) were analyzed and used to make calculations concerning cyclostrophic circulation around Venus. These indicate a balanced zonal (east to west) circulation, with midlatitude jets of peak velocities in the 110-120 m/s range, located between 50 and 40 mb in each hemisphere of the planet near 45 deg latitude. The calculations indicate breakdown of the balance conditions near the upper and lower boundaries at low latitudes. A slight asymmetry in the balanced zonal circulation arises out of an asymmetry in the thermal field. The PV radio occultation data show evidence of a direct meridional circulation that may be important in sustaining the atmospheric circulation of Venus. The value of continuous radio occultation measurements is stressed for studying shortand long-term variations of the atmospheric circulation.

Limaye, S. S.

1985-01-01

300

Nature of the Venus clouds as derived from their polarization  

International Nuclear Information System (INIS)

The linear polarization of sunlight reflected by Venus is analyzed by comparing observations with extensive multiple scattering computations. The analysis establishes that Venus is veiled by a cloud or haze layer of particles which have a narrow size distribution with a mean radius approximately 1 ?. The refractive index of the particles is 1.44 +- 0.015 at lambda = 0.55 ? with a small normal dispersion, the refractive index decreasing from the ultraviolet toward the infrared. The particles exist at a high level in the atmosphere, with the optical thickness unity occurring where the pressure is about 50 mb. The particle properties deduced from the polarization eliminate all but one of the cloud compositions which have been proposed for Venus. A concentrated solution of sulfuric acid (H2SO4-H2O) provides good agreement with the polarization data. (Auth.)

 
 
 
 
301

Thermal structure at the Venus terminator: Comparison of SOIR/Vex profiles with a radiative transfer model  

Science.gov (United States)

The wavelength range probed by the SOIR instrument on board Venus Express - 2.2 to 4.3 µm - allows a detailed chemical inventory of the Venus atmosphere [Bertaux et al., 2006; Vandaele et al., 2007]. The measurements all occur at the Venus terminator, on both the morning and evening sides, covering all latitudes from the North Pole to the South Pole. In particular CO2 number density vertical profiles are obtained from 70 to 160 km. Temperature profiles are deduced from the CO2 density profiles, using two different and independent techniques. The first one considers the hydrostatic law applied on the retrieved CO2 density profiles, assuming a CO2 mixing ratio vertical profile [Mahieux et al., 2010; 2012; 2014a]. The second one uses the ro-vibrational structure of the CO2 lines [Mahieux et al., 2014b]. Results of both methods are in agreement within their error bars; the uncertainties are larger with the ro-vibrational method. These temperature measurements show a striking permanent temperature minimum (at 125 km) and a weaker temperature maximum (over 100-115 km). The time variability of the CO2 density profiles spans over two orders of magnitude, and a clear trend is seen with latitude. The temperature variations are also important, up to 80 K for a given pressure level, but the latitude variation are small [Mahieux et al., 2014a].A 1D radiative transfer model has been developed to reproduce the SOIR terminator profiles, derived from the Mars thermosphere code used to simulate the atmospheric effects of Siding Springs coma on Mars atmosphere [Yelle et al., 2014]. This model has been improved to better account for the CO2 and CO radiative heating and cooling processes which have to be considered in the dense atmosphere of Venus. Atmospheric diffusion of CO2, CO and O is also considered. The preliminary results of the model and its comparison with the SOIR observations will be presented and discussed.

Mahieux, Arnaud; Erwin, Justin T.; Chamberlain, Sarah; Funke, Bernd; López Puertas, Manuel; López Valverde, Miguel; Robert, Séverine; Vandaele, Ann Carine; Wilquet, Valérie; Yelle, Roger V.; Bertaux, Jean-Loup

2014-11-01

302

The rate of pyrite decomposition on the surface of Venus  

Science.gov (United States)

We report the results of a detailed experiment study of the kinetics and mechanism of pyrite (FeS2) chemical weathering under Venus surface conditions. Pyrite is thermodynamically unstable on the surface of Venus and will spontaneously decompose to pyrrhotite (Fe7S8) because the observed S2 partial pressure in the lower atmosphere of Venus is lower than the S2 vapor pressure over coexisting pyrite and pyrrhotite. Pyrite decomposition kinetics were studied in pure CO2 and CO2 gas mixtures along five isotherms in the temperature range 390-531 C. In all gas mixtures studied, pyrite thermally decomposes to pyrrhotite (Fe7S8), which on continued heating loses sulfur to form more Fe-rich pyrrhotites. During this process the pyrrhotites are also being oxidized to form magnetite (Fe3O4), which converts to maghemite (gamma-Fe2O3), and then to hematite (alpha-Fe2O3). The reaction rates for pyrite thermal decomposition to pyrrhotite were determined by measuring the weight loss. The thickness of the unreacted pyrite in the samples provided a second independent reaction rate measurement. Finally, Mossbauer spectra done on 42 of the 115 experimental samples provided a third set of independent reaction rate data. Pyrite decomposition follows zero-order kinetics and is independent of the amount of pyrite present. The rate of pyrite decomposition is apparently independent of the gas compositions used and of the CO2 number density over a range of a factor of 40. The derived activation energy of approximately 150 kJ/mole is the same in pure CO2, two different CO-CO2 mixtures, and a ternary CO-SO2-CO2 mixture. Based on data for a CO-CO2-SO2 gas mixture with a CO number density approximately 10 times higher than at the surface of Venus and a SO2 number density approximately equal to that at the surface of Venus, the rate of pyrite destruction on the surface of Venus varies from about 1225 +/- 238 days/cm at the top of Maxwell Montes (approximately 660 K) to about 233 +/- 133 days/cm in the plains of Venus (approximately 740 K). These lifetimes are very short on a geological time scale and show that pyrite cannot exist on the surface of Venus for any appreciable length of time.

Fegley, B., Jr.; Lodders, K.; Treiman, A. H.; Klingelhoefer, G.

1995-01-01

303

Magnetic field overshoots in the Venus blow shock  

International Nuclear Information System (INIS)

An examination of Pioneer Venus Orbiter fluxgate magnetometer data has shown that magnetic field overshoots occur not only behind quasi-perpendicular bow shocks but also behind quasi-parallel shocks. Overshoots are assocciated only with supercritical shocks. Their amplitudes increase with increasing fast Mach number. Solar wind beta has a lesser effect. The thickness of the overshoot increases with decreasing Theta-BN. The thickness of apparent overshoots detected behind 4 strong fast interplanetary shocks (M greater than M/crit) is about 3 orders of magnitude larger. Multiple crossings of the Venus bow shock were observed mainly at turbulent shocks. Their occurence is not influenced by Theta-BN. 15 references

304

The 2010 European Venus Explorer (EVE) mission proposal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an 'M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (~25°C and ~0. 5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet....

Wilson, Cf; Chassefiere, E.; Hinglais, E.; Baines, Kh; Balint, Ts; Berthelier, J-j; Blamont, J.; Durry, G.; Ferencz, Cs; Grimm, Re; Imamura, T.; Josset, J-l; Leblanc, F.; Lebonnois, S.; Leitner, Jj

2012-01-01

305

Aerodynamic Parameter Identification of a Venus Lander  

Science.gov (United States)

An analysis was conducted to identify the parameters of an aerodynamic model for a Venus lander based on experimental free-flight data. The experimental free-flight data were collected in the NASA Langley 20-ft Vertical Spin Tunnel with a 25-percent Froude-scaled model. The experimental data were classified based on the wind tunnel run type: runs where the lander model was unperturbed over the course of the run, and runs were the model was perturbed (principally in pitch, yaw, and roll) by the wind tunnel operator. The perturbations allow for data to be obtained at higher wind angles and rotation rates than those available from the unperturbed data. The model properties and equations of motion were used to determine experimental values for the aerodynamic coefficients. An aerodynamic model was selected using a priori knowledge of axisymmetric blunt entry vehicles. The least squares method was used to estimate the aerodynamic parameters. Three sets of results were obtained from the following data sets: perturbed, unperturbed, and the combination of both. The combined data set was selected for the final set of aerodynamic parameters based on the quality of the results. The identified aerodynamic parameters are consistent with that of the static wind tunnel data. Reconstructions, of experimental data not used in the parameter identification analyses, achieved similar residuals as those with data used to identify the parameters. Simulations of the experimental data, using the identified parameters, indicate that the aerodynamic model used is incapable of replicating the limit cycle oscillations with stochastic peak amplitudes observed during the test.

Sykes, Robert A.

306

Observations of D/H ratios in H2O, HCl, and HF on Venus and new DCl and DF line strengths  

Science.gov (United States)

Intensities of the spectral lines in the fundamental bands of D35Cl and DF were calculated using the semi-empirical dipole moment functions derived from the most accurate and precise measurements of intensities of the ro-vibrational lines of H35Cl and HF. Values obtained in this way for the deuterated species are superior to any available measured or calculated data to date. Our study of the D/H ratios in H2O, HCl, and HF on Venus is based on spatially-resolved high-resolution spectroscopy using the CSHELL spectrograph at NASA IRTF. Search for DF on Venus using its R5 (1-0) line at 3024.054 cm-1 results in a DF mixing ratio of 0.23 ± 0.11 ppb that corresponds to (D/H)HF = 420 ± 200 times that in the Standard Mean Ocean Water (SMOW). H2O abundances on Venus were retrieved using lines at 3022.366 and 3025.761 cm-1 that were observed at an exceptionally low overhead telluric water abundance of 0.3 pr. mm. The measured H2O mixing ratios at 74 km vary insignificantly between 55°S and 55°N with a mean value of 3.2 ppm. When compared with simultaneous observations of HDO near 2722 cm-1, this results in (D/H)H2O = 95 ± 15 times SMOW. Reanalysis of the observation of the D35Cl R4 (1-0) line at 2141.540 cm-1 (Krasnopolsky, V.A. [2012b]. Icarus 219, 244-249) using the improved line strength and more thorough averaging of the spectra gives (D/H)HCl = 190 ± 50 times SMOW. The similarity of the measured (D/H)H2O = 95 ± 15 at 74 km with 120 ± 40 observed by De Bergh et al. (De Bergh, C., Bezard, B., Owen, T., Crisp, D., Maillard, J.P., Lutz, B.L. [1991]. Science 251, 547-549) below the clouds favors the constant (D/H)H2O from the surface to the mesosphere, in accord with the prediction by theory. D/H ? 100 removes a difference of a factor of 2 between H2O abundances in the observations by Krasnopolsky (Krasnopolsky, V.A. [2010b]. Icarus 209, 314-322) and the Venus Express nadir observations (Cottini, V., Ignatiev, N.I., Piccioni, G., Drossart, P., Grassi, D., Markiewicz, W.J. [2012]. Icarus 217, 561-569). Equivalent widths of the HDO and H2O lines are similar in our observations; therefore some errors cancel out in their ratios. Photochemistry of HCl in the mesosphere tends to enrich D in HCl and deplete it in H2O. This may be an explanation of the twofold difference between the observed D/H in HCl and H2O. An alternative explanation is based on (D/H)H2O ? 200 observed in the mesosphere by Bjoraker et al. (Bjoraker, G.L., Larson, H.P., Mumma, M.J., Timmermann, R., Montani, J.L. [1992]. Bull. Am. Astron. Soc. 24, 995) and Fedorova et al. (Fedorova, A. et al. J. Geophys. Res. 113, E00B22). This means an effective exchange of D between H2O and HCl and almost equal D/H in both species. However, this requires a twofold increase in D/H from the lower atmosphere to the mesosphere. This increase is not supported by theory; furthermore, condensation processes usually deplete D/H above the clouds. Photochemistry of HF has not been studied; it proceeds mostly in the lower thermosphere, and D/H in HF may be very different from that in H2O. Overall, the observational data on D/H in all hydrogen-bearing species on Venus are helpful to solve the problem of deuterium fractionation on Venus.

Krasnopolsky, V. A.; Belyaev, D. A.; Gordon, I. E.; Li, G.; Rothman, L. S.

2013-05-01

307

Magellan Science Briefing from NASA Headquarters  

Science.gov (United States)

This video presents a Magellan Science update on the most recent findings from the Magellan Mission to Venus. Brian Dunbar, NASA Public Affairs, introduces Dr. Wes Huntress, Division Director Solar System and Exploration Division. Dr. Huntress explains the Magellan Mission to Venus, which tested the temperature and emissivity of Venus, and collected high resolution radar imagery of 92% of the surface of the planet. Dr. Steve Saunders, Magellan Project Scientist, Jet Propulsion Lab, presents a visual global view of the North Pole of Venus. He also presents planet wide patterns of fracture on Venus. Dr. Saunders showed a video presentation of radio mapping results from Artemis. Dr. Wood, Radar Investigator, Smithsonian Astrophysical Observatory explains Mat Mons, which is the second highest mountain on Venus. Dr. John Wood also presents a video presentation of his findings. Dr. Gordon Pettengill, Principle Investigator, Massachusetts Institute of Technology, presents a video on the Topography of the Magellan Mission, which is able to give resolution ten times finer and further into the South and into the North than was possible earlier. The video of the Magellan Science update ends with a question and answer period.

1991-10-01

308

Survey of the spectral properties of turbulence in the solar wind, the magnetospheres of Venus and Earth, at solar minimum and maximum  

Science.gov (United States)

In the framework of the European FP7 project STORM ("Solar system plasma Turbulence: Observations, inteRmittency and Multifractals") we analyze the properties of turbulence in various regions of the solar system, for the minimum and respectively maximum of the solar activity. The main scientific objective of STORM is to advance the understanding of the turbulent energy transfer, intermittency and multifractals in space plasmas. Specific analysis methods are applied on magnetic field and plasma data provided by Ulysses, Venus Express and Cluster, as well as other solar system missions (e.g. Giotto, Cassini). In this paper we provide an overview of the spectral properties of turbulence derived from Power Spectral Densities (PSD) computed in the solar wind (from Ulysses, Cluster, Venus Express) and at the interface of planetary magnetospheres with the solar wind (from Venus Express, Cluster). Ulysses provides data in the solar wind between 1992 and 2008, out of the ecliptic, at radial distances ranging between 1.3 and 5.4 AU. We selected only those Ulysses data that satisfy a consolidated set of selection criteria able to identify "pure" fast and slow wind. We analyzed Venus Express data close to the orbital apogee, in the solar wind, at 0.72 AU, and in the Venus magnetosheath. We investigated Cluster data in the solar wind (for time intervals not affected by planetary ions effects), the magnetosheath and few crossings of other key magnetospheric regions (cusp, plasma sheet). We organize our PSD results in three solar wind data bases (one for the solar maximum, 1999-2001, two for the solar minimum, 1997-1998 and respectively, 2007-2008), and two planetary databases (one for the solar maximum, 2000-2001, that includes PSD obtained in the terrestrial magnetosphere, and one for the solar minimum, 2007-2008, that includes PSD obtained in the terrestrial and Venus magnetospheres and magnetosheaths). In addition to investigating the properties of turbulence for the minimum and maximum of the solar cycle we also analyze the spectral similarities and differences between fast and slow wind turbulence. We emphasize the importance of our data survey and analysis in the context of understanding the solar wind turbulence, the exploitation of data bases and as a first step towards developing a (virtual) laboratory for studying solar system plasma turbulence. Research supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no 313038/STORM, and a grant of the Romanian Ministry of National Education, CNCS - UEFISCDI, project number PN-II-ID-PCE-2012-4-0418.

Echim, Marius M.

2014-05-01

309

Origin of Corona-Dominated Topographic Rises on Venus  

Science.gov (United States)

Both large-scale mantel upwellings, comparable to terrestrial hotspots on Earth, and smaller scale mantel upwellings, known as coronae, occur on Venus. Corona-dominated rises have many of the characteristics of large scale mantle upwellings, or hotspots, such as broad topographic rises greater than 1000km in diameter and large positive gravity anomalies.

Smrekar, S.; Stofan, E.

1999-01-01

310

Pioneer Venus sounder and small probes Nephelometer instrument  

Science.gov (United States)

The Nephelometer instrument flown on all four of the probes of the Pioneer Venus mission is described. The instruments functioned well, returning data on the backscattering properties of the Venusian clouds and ambient solar radiation in several wavelength intervals as a function of altitude at four widely separated planetary locations. The design considerations, instrument construction, calibration and performance are discussed.

Ragent, B.; Wong, T.; Blamont, J. E.; Eskovitz, A. J.; Harnett, L. N.; Pallai, A.

1980-01-01

311

Using manufacturing message specification for monitor and control at Venus  

Science.gov (United States)

The flexibility and robustness of a monitor and control (M&C) system are a direct result of the underlying interprocessor communications architecture. A new architecture for M&C at the Deep Space Communications Complexes (DSCC's) has been developed based on the Manufacturing Message Specification (MMS) process control standard of the Open System Interconnection (OSI) suite of protocols. This architecture has been tested both in a laboratory environment and under operational conditions at the Deep Space Network (DSN) experimental Venus station (DSS-13). The Venus experience in the application of OSI standards to support M&C has been extremely successful. MMS meets the functional needs of the station and provides a level of flexibility and responsiveness previously unknown in that environment. The architecture is robust enough to meet current operational needs and flexible enough to provide a migration path for new subsystems. This paper will describe the architecture of the Venus M&C system, discuss how MMS was used and the requirements this imposed on other parts of the system, and provide results from systems and operational testing at the Venus site.

Heuser, W. Randy; Chen, Richard L.; Stockett, Michael H.

1993-01-01

312

Venus and Mercury, and how to observe them  

CERN Document Server

Venus and Mercury have long been regarded as difficult targets for amateur observers, but advances in commercially-made telescopes have brought them within the skills of observers of only moderate experience. This book presents description of the history and geology of the so-called inferior planets.

Grego, Peter

2007-01-01

313

The 1761 discovery of Venus' atmosphere: Lomonosov and others  

Science.gov (United States)

Russian polymath Mikhail Vasil'evich Lomonosov claimed to have discovered the atmosphere of Venus during the planet's transit over the Sun's disc in 1761. Although several other astronomers observed similar effects during the 1761 and 1769 transits, Lomonosov's claim for priority is the strongest as he was the first to publish a comprehensive scientific report, and the first to offer a detailed explanation of the aureole around Venus at ingress and egress, which was caused by refraction of the sunlight through Venus' atmosphere. His observations, moreover, were successfully reconstructed experimentally using antique telescopes during the 2012 transit. In this paper we review details of Lomonosov's observations (which usually are poorly covered by commentators and often misunderstood); compare other reports of the eighteenth century transit observations, and summarize their findings in a comprehensive table; and address recent calls to reconsider Lomonosov's priority. After reviewing the available documentation we conclude that everything we learned before, during and after the twenty-first century transits only supports further the widely-accepted attribution of the discovery of Venus' atmosphere to Lomonosov.

Shiltsev, Vladimir

2014-03-01

314

The Electrodynamics of the Solar Wind Interaction with Venus  

Science.gov (United States)

Venus has a thick atmosphere whose upper reaches are ionized by solar EUV. The temperature and density of this ionosphere provide sufficient pressure that, at solar maximum for normal solar wind pressures, the solar wind is deflected at altitudes far above the region of significant ion-neutral collisions. Hence when the interplanetary field changes, a current is induced at the ionopause that excludes the magnetic field from the ionosphere. A magnetic barrier of magnetic field draped around the ionosphere builds up and forms the obstacle to the solar wind flow. Since the size of the Venus obstacle vastly exceeds that of the ion-gyro motion, a bow shock forms that slows, heats, and deflects the solar wind plasma. This interaction is the epitome of the induced magnetosphere. At times though, the solar wind pressure is too strong to be stood off by the ionosphere, and the ionopause drops to collisional altitudes. At this point, the ionosphere becomes magnetized throughout. Venus also has an H and O exosphere that extends into the solar wind. These can lead to the occurrence of cometary processes like mass pickup and deceleration of the flow. In short, the solar wind interaction with Venus has many facets and is sufficiently complex to continue to fuel new discoveries and a little controversy.

Russell, C. T.; Ma, Y. J.; Luhman, J. G.

2010-05-01

315

Electrotonic and action potentials in the Venus flytrap.  

Science.gov (United States)

The electrical phenomena and morphing structures in the Venus flytrap have attracted researchers since the nineteenth century. We have observed that mechanical stimulation of trigger hairs on the lobes of the Venus flytrap induces electrotonic potentials in the lower leaf. Electrostimulation of electrical circuits in the Venus flytrap can induce electrotonic potentials propagating along the upper and lower leaves. The instantaneous increase or decrease in voltage of stimulating potential generates a nonlinear electrical response in plant tissues. Any electrostimulation that is not instantaneous, such as sinusoidal or triangular functions, results in linear responses in the form of small electrotonic potentials. The amplitude and sign of electrotonic potentials depend on the polarity and the amplitude of the applied voltage. Electrical stimulation of the lower leaf induces electrical signals, which resemble action potentials, in the trap between the lobes and the midrib. The trap closes if the stimulating voltage is above the threshold level of 4.4V. Electrical responses in the Venus flytrap were analyzed and reproduced in the discrete electrical circuit. The information gained from this study can be used to elucidate the coupling of intracellular and intercellular communications in the form of electrical signals within plants. PMID:23422156

Volkov, Alexander G; Vilfranc, Chrystelle L; Murphy, Veronica A; Mitchell, Colee M; Volkova, Maia I; O'Neal, Lawrence; Markin, Vladislav S

2013-06-15

316

The GUINEVERE project at the VENUS-F Facility  

International Nuclear Information System (INIS)

Within the framework of the ECATS (Experimental activities on the Coupling of an Accelerator, a spallation Target and a Sub-critical blanket) research domain of the FP6 IP-EUROTRANS program, the GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 in order to check in the experiments an open questions stay for the techniques used in the MUSE programme (CEA Cadarache, France, 2000-2004), related to the online reactivity monitoring, sub-criticality determination and operational procedure of an Accelerator Driven System. For this purpose, the VENUS light water critical reactor at the SCK-CEN site of Mol (Belgium) was modify into a subcritical fast core (VENUS-F) and the GENEPI accelerator, designed for the MUSE experiment was up-graded to the new GENEPI-3C accelerator. The VENUS-F coupled with the GENEPI-3C and a TiT target will provide a unique facility in Europe for fast sub-critical and critical reactor physics investigations. This paper describes the present status of the facility. (authors)

317

Modulation of Venus ion densities associated with solar variations  

International Nuclear Information System (INIS)

The dayside ion concentrations in the Venus ionosphere obtained by the Pioneer Venus orbiter ion mass spectrometer exhibit a modulation corresponding to the 27-day solar variation. Comparisons were made of the amplitudes of modulation of CO2+, C+, and O2+, with the amplitudes of the 27-day variation in the 10.7 cm solar radio flux and the simultaneously measured EUV fluxes at He II (304 A) and Lyman ? (1026 A), together with a theoretical analysis of the effects of solar variability on the ionosphere and neutral atmosphere of Venus. This analysis leads us to the conclusion that the observed modulation of dayside ion densities is primarily due to the variability in the ionizing EUV radiations and, to a much lesser extent, the result of the variability with solar activity of the neutral atmosphere via the variability in exospheric temperature. In this connection, we also show, theoretically, why the percentage variation of exospheric temperature on Venus (as observed in the ONMS data) for a given variation in F/sub 10.7/, is only half of the exospheric temperature variation for Earth

318

New Results with the superconducting ECR ion source VENUS  

International Nuclear Information System (INIS)

During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA R and D injector is the production of 240emA of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+,180 e mu A of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10 kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described. During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5 emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+, 180 e muA of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance of the VENUS ion source, low energy beam transport (LEBT) and its closed loop cryogenic system are described in the paper. Recently, a new high temperature axial oven has been installed in the source and the first results on metal beams such as bismuth are given. The design of the 28 GHz, 10 kW gyrotron system is also be described

319

The evolution of Venus: Present state of knowledge and future exploration  

Science.gov (United States)

A detailed characterization of the formation and evolution of Venus is a key link to the study of terrestrial planets, and to their divergent evolutions. While Earth and to a lesser extent Mars (thanks to the analysis of SNC meteorites) are extensively studied in a comparative planetology context, the history of the most Earth-like planet of the Solar System, Venus, is still poorly understood. For how long has Venus been in its current extreme climate state? When and how did it diverge from a (possible) early Earth-like state? Has Venus been a potentially habitable planet at some time of its early history? Did a "cool early Venus" stage occur between the end of accretion and the late heavy bombardment, like suspected for Earth? What are the implications of the Venus/Earth comparison for the nature and evolution of habitable terrestrial planets throughout the universe? A major observational missing link in our understanding of Venus' climate evolution is the elementary and isotopic pattern of noble gases and of stable isotopes in Venus' atmosphere, still poorly known. The concentrations of heavy noble gases (Kr, Xe) and their isotopes are mostly unknown, and our knowledge of light noble gases and stable isotopes is incomplete and inaccurate. In this paper, we summarize our present understanding of Venus' early evolution, including the crucial question of knowing if water ever condensed at the surface of the planet. Then, we assess the potential contribution of a precise measurement of noble gases, their isotopes and stable isotopes to improve of our understanding of Venus evolution, and list the main questions that noble gases and isotope measurements would help to answer. Finally, we show how future exploration of Venus could allow to gain a glimpse into the early evolution of Venus through a small in-situ mission based on a single balloon probe, called EVE (European Venus Explorer), proposed in the frame of the ESA Cosmic Vision program.

Chassefière, Eric; Wieler, Rainer; Marty, Bernard; Leblanc, François

2012-04-01

320

Heliospheric current sheet inclinations at Venus and Earth  

Directory of Open Access Journals (Sweden)

Full Text Available We investigate the inclinations of heliospheric current sheet at two sites in interplanetary space, which are generated from the same solar source. From the data of solar wind magnetic fields observed at Venus (0.72 AU and Earth (1 AU during December 1978-May 1982 including the solar maximum of 1981, 54 pairs of candidate sector boundary crossings are picked out, of which 16 pairs are identified as sector boundaries. Of the remainder, 12 pairs are transient structures both at Venus and Earth, and 14 pairs are sector boundaries at one site and have transient structures at the other site. It implies that transient structures were often ejected from the coronal streamer belt around the solar maximum. For the 16 pairs of selected sector boundaries, we determine their normals by using minimum variance analysis. It is found that most of the normal azimuthal angles are distributed between the radial direction and the direction perpendicular to the spiral direction both at Venus and Earth. The normal elevations tend to be smaller than ~ 45° with respect to the solar equatorial plane, indicating high inclinations of the heliospheric current sheet, in particular at Earth. The larger scatter in the azimuth and elevation of normals at Venus than at Earth suggests stronger effects of the small-scale structures on the current sheet at 0.72 AU than at 1 AU. When the longitude difference between Venus and Earth is small (<40° longitudinally, similar or the same inclinations are generally observed, especially for the sector boundaries without small-scale structures. This implies that the heliospheric current sheet inclination tends to be maintained during propagation of the solar wind from 0.72 AU to 1 AU. Detailed case studies reveal that the dynamic nature of helmet streamers causes variations of the sector boundary structure.

Key words. Interplanetary physics (interplanetary magnetic fields; sources of solar wind

G. Ma

 
 
 
 
321

HDO and SO2 thermal mapping on Venus. II. The SO2 spatial distribution above and within the clouds  

Science.gov (United States)

Sulfur dioxide and water vapor, two key species of Venus photochemistry, are known to exhibit significant spatial and temporal variations above the cloud top. In particular, ground-based thermal imaging spectroscopy at high spectral resolution, achieved on Venus in January 2012, has shown evidence for strong SO2 variations on timescales shorter than a day. We have continued our observing campaign using the TEXES high-resolution imaging spectrometer at the NASA InfraRed Telescope Facility to map sulfur dioxide over the disk of Venus at two different wavelengths, 7 ?m (already used in the previous study) and 19 ?m. The 7 ?m radiation probes the top of the H2SO4 cloud, while the 19 ?m radiation probes a few kilometers below within the cloud. Observations took place on October 4 and 5, 2012. Both HDO and SO2 lines are identified in our 7-?m spectra and SO2 is also easily identified at 19 ?m. The CO2 lines at 7 and 19 ?m are used to infer the thermal structure. An isothermal/inversion layer is present at high latitudes (above 60 N and S) in the polar collars, which was not detected in October 2012. The enhancement of the polar collar in October 2012 is probably due to the fact that the morning terminator is observed, while the January data probed the evening terminator. As observed in our previous run, the HDO map is relatively uniform over the disk of Venus, with a mean mixing ratio of about 1 ppm. In contrast, the SO2 maps at 19 ?m show intensity variations by a factor of about 2 over the disk within the cloud, less patchy than observed at the cloud top at 7 ?m. In addition, the SO2 maps seem to indicate significant temporal changes within an hour. There is evidence for a cutoff in the SO2 vertical distribution above the cloud top, also previously observed by SPICAV/SOIR aboard Venus Express and predicted by photochemical models.

Encrenaz, T.; Greathouse, T. K.; Richter, M. J.; Lacy, J.; Widemann, T.; Bézard, B.; Fouchet, T.; deWitt, C.; Atreya, S. K.

2013-11-01

322

Beyond Economic Valuation: Alternative Ways to express the Value of Biodiversity in Science and Policy | Convention on Biological Diversity  

...Arild Vatn, Professor of institutional and ecological economics at the Norwegian University of Life Sciences 12:00 -12:45 Alternative ways to express the value of biodiversity in EU Research and its impact on policy (from FP7 to FP8) Adrian Peres, DG Research and Innovation, Unit I3 -Management of Natural Resources Strahil Christov , DG Environment , Unit B2 - Biodiversity 12:45-14:15 Science-Policy-Society Lunch Debate on transdisciplinary research for biodiversity and natural resource management (BIOMOT policy brief #3) 14:15-15:45 General key-notes: ldquo;lessons from practitioners, projects and governance initiativesrdquo;...

323

Spectropolarimetry of Venus and Jupiter clouds - Information content of equivalent widths  

Science.gov (United States)

The theory of the curve-of-growth for absorption lines formed in an anisotropically scattering medium, particularly the clouds of Venus and Jupiter, is generalized to the case of polarization. When the photon path-length distributions associated with each of Stokes' parameters (Il, Ir, and Q) are evaluated using Pade's approximations, analytical expressions can be derived for the corresponding equivalent widths. It is found that spectra of Q, derivable from the rotational temperature of the Q-lines, are formed at a level closer to the cloud top than the photopolarimetric level, rendering a more accurate location of the cloud top than possible by photopolarization. It is also demonstrated that simultaneous measurements of the equivalent widths of strong I- and Q-lines can provide analytical relations for retrieving the scale-height ratios of ambient gas-to-cloud particles and minor constituent-to-ambient gas molecules without resorting to any other independent measurement.

Buriez, J. C.; Fouquart, Y.; Fymat, A. L.

1979-01-01

324

Mapping radiating graben-fissure systems and pit crater chains on Venus  

Science.gov (United States)

This study has mapped two types of extensional tectono-magmatic structures including radiating graben-fissure systems (RGFS) in the Idunn Mons and Mielikki Mons study areas, and pit crater chains in Idunn Mons, Themis Regio, Ulfrun Regio, and Ganiki Planitia on Venus. The areas selected to map RGFS host high emissivity anomalies focused on a single volcano and are proposed to reflect younger lava flows which might have occurred as recently as 250 ka. A relative chronology of RGFS is determined using cross-cutting relationships between interacting systems and surface geology. The Idunn Mons high emissivity anomaly is host to the youngest magmatic and volcanic activity, while the Mielikki Mons high emissivity anomaly is not the youngest. Hierarchical clusters of pit crater chains are predominantly focused on RGFS and coronae. It is hypothesized that hierarchical clustering is due to a lithology related variable as lithology may dictate how tensile stress is expressed.

Davey, Sarah

325

Investigating Climate on Venus with Future Missions (Invited)  

Science.gov (United States)

Venus presents unique opportunities to study climate on a nearby, active planet that is both surprisingly like Earth and startlingly different. Venus is remarkably like Earth in terms of bulk properties such as size, mass and density. And yet its modern climate has evolved to a state which is dramatically divergent from that of Earth. Thus Venus presents a fascinating experimental laboratory for studying and modeling climate processes on an Earth-sized world with a strong atmospheric greenhouse and for exploring the role of heliocentric distance and other initial conditions in determining the outcome of climate evolution on an Earth-like planet. Previous spacecraft investigations of Venus, combined with ground based observations, have confirmed the existence of a dynamic, changeable atmosphere with a deep troposphere extending to an altitude of 65 km, a highly variable globally encompassing cloud deck extending from 48 to 70 km altitude, and a complex pattern of global circulation dominated by superrotating winds which circle the globe at a rate up to 60 times faster than the retrograde rotation of the solid planet, with the peak wind velocities at an altitude of 60 km. Other large scale features of the global circulation include Hadley cells in which air rises at low latitudes and travels poleward at high altitudes; and large, complex vortices at both poles where sinking air from the Hadley circulation intersects with the superrotation. Attempts to model this global circulation using modified terrestrial General Circulation Models (GCMs) have been only partially successful. Such tests have the promise of not only increasing our understanding of the Venus atmosphere and its response to solar radiation, but improving our general knowledge of climate and global circulation on Earth-sized terrestrial planets, including Earth itself. They also serve as a 'reality check' on the current generation of terrestrial GCMs and their ability to accurately model climate and circulation on radically altered versions of Earth's climate. In the framework of comparative planetology, climate models and GCMs in particular have taken on a vital role in understanding and predicting the role of anthropogenic forcing in Earth's climate, and separating human from natural influences. The potential role of new spacecraft observations of Venus in improving our ability to accurately model climate on moderately to severely perturbed variations of Earth's current climate is thus extremely valuable. Several efforts to model climate on Venus using terrestrial GCMs have reproduced the gross properties of the Venusian global circulation. These efforts have also revealed that various components of terrestrial GCMs are 'hard coded' with empirically-derived assumptions that are at best only accurate for the current terrestrial climate. Many of these assumptions are hidden within complex 'black boxes' of code that are not always obvious to the modelers using the code. Thus pushing the codes near to, or beyond, the breaking point by applying them toward the problem of Venus helps to improve the veracity and reliability of these models for terrestrial applications. At this point our ability to greatly improve upon these efforts is hampered by the amount and quality of available data on the Venus atmosphere. In order to understand which model, and which assumptions are correct, improved spacecraft observations from several platforms are required.

Grinspoon, D. H.

2013-12-01

326

The VENUS/NWChem software package. Tight coupling between chemical dynamics simulations and electronic structure theory  

Science.gov (United States)

The interface for VENUS and NWChem, and the resulting software package for direct dynamics simulations are described. The coupling of the two codes is considered to be a tight coupling since the two codes are compiled and linked together and act as one executable with data being passed between the two codes through routine calls. The advantages of this type of coupling are discussed. The interface has been designed to have as little interference as possible with the core codes of both VENUS and NWChem. VENUS is the code that propagates the direct dynamics trajectories and, therefore, is the program that drives the overall execution of VENUS/NWChem. VENUS has remained an essentially sequential code, which uses the highly parallel structure of NWChem. Subroutines of the interface that accomplish the data transmission and communication between the two computer programs are described. Recent examples of the use of VENUS/NWChem for direct dynamics simulations are summarized.

Lourderaj, Upakarasamy; Sun, Rui; Kohale, Swapnil C.; Barnes, George L.; de Jong, Wibe A.; Windus, Theresa L.; Hase, William L.

2014-03-01

327

The VENUS/NWChem Software Package. Tight Coupling Between Chemical Dynamics Simulations and Electronic Structure Theory  

Energy Technology Data Exchange (ETDEWEB)

The interface for VENUS and NWChem, and the resulting software package for direct dynamics simulations are described. The coupling of the two codes is considered to be a tight coupling. The two codes are compiled and linked together and act as one executable with data being passed between the two codes through routine calls. The advantages of this type of coupling are discussed. The interface has been designed to have as little interference as possible with the core codes of both VENUS and NWChem. VENUS is the code that propagates the direct dynamics trajectories and, therefore, is the program that drives the overall execution of VENUS/NWChem. VENUS has remained an essentially sequential code, which uses the highly parallel structure of NWChem. Subroutines of the interface which accomplish the data transmission and communication between the two computer programs are described. Recent examples of the use of VENUS/NWChem for direct dynamics simulations are summarized.

Lourderaj, Upakarasamy; Sun, Rui; De Jong, Wibe A.; Windus, Theresa L.; Hase, William L.

2014-03-01

328

VENUS: Hypothetical life found at ``a wrong place''  

Science.gov (United States)

The position of the hypothetical habitability zone in extrasolar planetary system was considered by many authors. Approximately 1/4 of exoplanets orbit their stars at very low orbits, which leads to high temperatures of their surface (if any), up to 800 K or more. Some of them should have the physical conditions close to those of Venus. Is there any possibility that the life forms can exist at quite different environment than “normal”, Earth-like physical settings? Namely the planet Venus could be the natural laboratory for studies of this type, having the dense, hot (735 K) oxygenless CO2 - atmosphere and high, 9.2 MPa, pressure at the surface. It should be recalled that the only existing data of actual close in TV-observations of Venus’ surface are the results of a series of missions of the Russian VENERA landers which took place the 1970s and 80s, working in the atmosphere and on the surface of Venus. No other results of this kind were obtained since. A re-examination of images of Venusian surface returned from the VENERA landers has been undertaken using a modern processing technique, with a view to detect any possible signs of life under the specific conditions on Venus. This speculative identification rests on two characteristics of these features: (a) their somewhat suggestive morphology and (b) their temporal appearance and behavior (present, than absent on subsequent images of the same area; or changing appearances). The re-exemination has identified previously unreported features that may correspond to hypothetical life forms on Venus’ surface. A new analysis and comparison of the content of the sequence of panoramas of the Venusian surface made in 2013, allowed the author to detect some new interesting objects displayed on the panoramas that hypothetically may be related to fauna and flora of the planet. Some of the objects found were described in a dozen of papers (2012, 2013). There are also found and listed in the report images of objects with special morphology resembling the shape of some terrestrial fauna and flora. References: Ksanfomality L.V. 2013 Doklady Physics. 58 (5), 204 Ksanfomality L.V. 2013 Doklady Physics. 58 (11), 514

Ksanfomality, Leonid

329

Mission Sizing and Trade Studies for Low Ballistic Coefficient Entry Systems to Venus  

Science.gov (United States)

The U.S and the U.S.S.R. have sent seventeen successful atmospheric entry missions to Venus. Past missions to Venus have utilized rigid aeroshell systems for entry. This rigid aeroshell paradigm sets performance limitations since the size of the entry vehicle is constrained by the fairing diameter of the launch vehicle. This has limited ballistic coefficients (beta) to well above 100 kg/m2 for the entry vehicles. In order to maximize the science payload and minimize the Thermal Protection System (TPS) mass, these missions have entered at very steep entry flight path angles (gamma). Due to Venus thick atmosphere and the steep-gamma, high- conditions, these entry vehicles have been exposed to very high heat flux, very high pressures and extreme decelerations (upwards of 100 g's). Deployable aeroshells avoid the launch vehicle fairing diameter constraint by expanding to a larger diameter after the launch. Due to the potentially larger wetted area, deployable aeroshells achieve lower ballistic coefficients (well below 100 kg/m2), and if they are flown at shallower flight path angles, the entry vehicle can access trajectories with far lower decelerations (50-60 g's), peak heat fluxes (400 W/cm2) and peak pressures. The structural and TPS mass of the shallow-gamma, low-beta deployables are lower than their steep-gamma, high-beta rigid aeroshell counterparts at larger diameters, contributing to lower areal densities and potentially higher payload mass fractions. For example, at large diameters, deployables may attain aeroshell areal densities of 10 kg/m2 as opposed to 50 kg/m2 for rigid aeroshells. However, the low-beta, shallow-gamma paradigm also raises issues, such as the possibility of skip-out during entry. The shallow-gamma could also increase the landing footprint of the vehicle. Furthermore, the deployable entry systems may be flexible, so there could be fluid-structure interaction, especially in the high altitude, low-density regimes. The need for precision in guidance, navigation and control during entry also has to be better understood. This paper investigates some of the challenges facing the design of a shallow-gamma, low-beta entry system.

Dutta, Soumyo; Smith, Brandon; Prabhu, Dinesh; Venkatapathy, Ethiraj

2012-01-01

330

Submillimeter spectroscopy of Venus's atmosphere with ALMA: CO, HDO and sulfur species  

Science.gov (United States)

The study of the composition of the upper mesosphere of Venus is necessary to characterize several atmospheric processes such as photochemistry, condensation and dynamics. At this altitude level (80-110 km), several species have been detected thanks to their (sub)millimeter rotational lines, in particular sulfur species SO2 and SO, that may be indicative of Venus' volcanic activity, and showed an abundance increase with altitude suggesting a local sulfur-bearing aerosol source[1,2]. H2O, which takes part in the formation of H2SO4 clouds, was also detected as well as its isotope HDO; their analyses revealed significant diurnal and long-term temporal variations [3,4]. To explore this case in greater detail and better assess local, diurnal and temporal variations of minor species, heterodyne spectroscopic observations were obtained in November 2011 during the first Early Science observation cycle of the Atacama Large Millimeter Array (ALMA), the largest (sub)millimeter interferometer, which at the time offered 16 12-m large antennas. These observations allowed us to map the day side of Venus with a spatial resolution down to 1.2-2.4"" (for a disk of 11"), targeting SO2, SO, HDO and CO transitions around 0.85mm (335-346 GHz). All of these transitions were well detected and their modeling yielded abundances consistent with previous single-dish assessments. We will present a detailed analysis of the data in terms of spatial distribution (horizontal and vertical) and temporal variations, and we will discuss their interpretation with regard to the efficiency of photochemical destruction in the mesosphere and aerosol sources. In addition, by mapping the CO(3-2) line's Doppler-shifts, we have been able to derive the wind field near the upper boundary of the mesosphere, whichs corresponds to a region of dynamic transition between the retrograde zonal wind regime of the troposphere and the subsolar-to-antisolar flow that dominates at higher altitudes. [1] Sandor et al., 2010, Icarus 208, p.49-60 [2] Sandor et al., 2012, Icarus 217, p. 239-244 [3] Gurwell et al., 2007, Icarus 188, p.288-304 [4] Sandor and Clancy, 2005, Icarus 177, p.129-143

Moullet, Arielle; Moreno, R.; Encrenaz, T.; Lellouch, E.; Fouchet, T.

2013-10-01

331

Venus - Improved spin vector from Goldstone radar observations  

International Nuclear Information System (INIS)

Twenty-one radar images of the surface of Venus obtained between 1972 and 1982 have been compared to follow the motion of 28 distinct features. The delays and Doppler shifts of these features with respect to the subradar points on the various days were used in a nonlinear least-squares parameter estimation algorithm to refine the period and pole orientation of Venus. The period is found to be -243.022 + or - 0.003 days; the right ascension and declination of the pole are: alpha = 272.816 + or - 0.14 deg; beta = 67.218 + or - 0.05 deg (B1950). These standard error estimates attempt to include effects of systematic errors. 14 refs

332

Venus spherical harmonic gravity model to degree and order 60  

Science.gov (United States)

The Magellan and Pioneer Venus Orbiter radiometric tracking data sets have been combined to produce a 60th degree and order spherical harmonic gravity field. The Magellan data include the high-precision X-band gravity tracking from September 1992 to May 1993 and post-aerobraking data up to January 5, 1994. Gravity models are presented from the application of Kaula's power rule for Venus and an alternative a priori method using surface accelerations. Results are given as vertical gravity acceleration at the reference surface, geoid, vertical Bouguer, and vertical isostatic maps with errors for the vertical gravity and geoid maps included. Correlation of the gravity with topography for the different models is also discussed.

Konopliv, Alex S.; Sjogren, William L.

1994-01-01

333

The thermal balance of the atmosphere of Venus  

International Nuclear Information System (INIS)

Current knowledge of the temperature structure of the atmosphere of Venus is briefly summarized. The principal features to be explained are the high surface temperature, the small horizontal temperature contrasts near the cloud tops in the presence of strong apparent motions, and the low value of the exospheric temperature. In order to understand the role of radiative and dynamical processes in maintaining the thermal balance of the atmosphere, a great deal of additional data on the global temperature structure, solar and thermal radiation fields, structure and optical properties of the clouds, and circulation of the atmosphere are needed. The ability of the Pioneer Venus Orbiter and Multiprobe Missions to provide these data is indicated. (Auth.)

334

Dynamics, winds, circulation and turbulence in the atmosphere of Venus  

International Nuclear Information System (INIS)

With the possible exception of the lowest one or two scale heights, the dominant mode of circulation of Venus' atmosphere is a rapid, zonal, retrograde motion. Global albedo variations in the ultraviolet may reflect planetary scale waves propagating relative to the zonal winds. Other special phenomena such as cellular convection in the subsolar region and internal gravity waves generated in the interaction of the zonal circulation with the subsolar disturbance may also be revealed in ultraviolet imagery of the atmosphere. The contributions of experiments on the Orbiter and Entry Probes of Pioneer Venus toward unravelling the mystery of the planet's global circulation and the role played by waves, instabilities and convection therein are discussed. (Auth.)

335

Flight performance of the Pioneer Venus Orbiter solar array  

Science.gov (United States)

The Pioneer Venus Orbiter (PVO) solar panel power output capability has degraded much more severely than has the power output capability of solar panels that have operated in earth-orbiting spacecraft for comparable periods of time. The incidence of solar proton events recorded by the spacecraft's scientific instruments accounts for this phenomenon only in part. It cannot explain two specific forms of anomalous behavior observed: 1) a variation of output per spin with roll angle, and 2) a gradual degradation of the maximum output. Analysis indicates that the most probable cause of the first anomaly is that the solar cells underneath the spacecraft's magnetometer boom have been damaged by a reverse biasing of the cells that occurs during pulsed shadowing of the cells by the boom as the spacecraft rotates. The second anomaly might be caused by the effects on the solar array of substances from the upper atmosphere of Venus.

Goldhammer, L. J.; Powe, J. S.; Smith, Marcie

1987-01-01

336

HDO and SO2 thermal mapping on Venus  

Science.gov (United States)

We report on ground-based thermal observations of Venus using the TEXES imaging spectrometer at IRTF (Mauna Kea, Hawaii) in October 2012. Highresolution data were obtained at 7 ?m and 19 ?m, probing slightly different layers atop and within the cloud, and were compared with the results of our previous campaign (January 2012, [1]). Three main conclusions can be drawn: (1) An isothermal/inversion layer appears at high latitudes in the October data but not in the January data; (2) The spatial distribution of SO2 seems to show variations within a very short timescale, less than an hour; in contrast, the HDO distribution over the Venus disk shows no noticeable spatial nor temporal variation; (3) The SO2 vertical distribution is strongly depleted a few kilometers above the cloudtop. The high variability of SO2 is probably the result of its very short photodissociation lifetime.

Encrenaz, T.; Greathouse, T.; Richter, M.; Lacy, J.; Widemann, T.; Bézard, B.; Fouchet, T.; Atreya, S.

2013-09-01

337

Planetary loss from light ion escape on Venus  

Science.gov (United States)

Using Pioneer Venus data, hydrogen and deuterium ions are shown to escape from the hydrogen bulge region in the nightside ionosphere. The polarization electric field propels these light ions upward through the ionosphere and into the ion-exosphere, where H(+) and D(+) continue to be accelerated away from Venus and move into the ionotail and beyond. The vertical flow speeds of H(+) and D(+) are found to be about the same; therefore, selective escape between H(+) and D(+) is negligible for this mechanism. Present day planetary loss rates of about 8.6 x 10(exp 25)/s and 3.2 X 10(exp 23)/s were obtained for H(+) and D(+), respectively. Such rates, persisting over a few billion years, should have significantly affected the planetary water budget.

Hartle, R. E.; Grebowsky, J. M.

1995-01-01

338

Earthlike planets: Surfaces of Mercury, Venus, earth, moon, Mars  

Science.gov (United States)

The surfaces of the earth and the other terrestrial planets of the inner solar system are reviewed in light of the results of recent planetary explorations. Past and current views of the origin of the earth, moon, Mercury, Venus and Mars are discussed, and the surface features characteristic of the moon, Mercury, Mars and Venus are outlined. Mechanisms for the modification of planetary surfaces by external factors and from within the planet are examined, including surface cycles, meteoritic impact, gravity, wind, plate tectonics, volcanism and crustal deformation. The origin and evolution of the moon are discussed on the basis of the Apollo results, and current knowledge of Mercury and Mars is examined in detail. Finally, the middle periods in the history of the terrestrial planets are compared, and future prospects for the exploration of the inner planets as well as other rocky bodies in the solar system are discussed.

Murray, B.; Malin, M. C.; Greeley, R.

1981-01-01

339

Magellan - Early results from the Venus mapping mission  

International Nuclear Information System (INIS)

Some results obtained with the Magellan Venus Radar Mapper are presented. Mapping was initiated on October 26, 1990 and has completed over 714 orbits of image data, covering 40 percent of the surface of Venus. Mapping began at 330 deg east longitude, mapping from the north pole to about 78 deg south latitude. Included are the regions of Ishtar Terra, Sedna, Guinevere and Lavinia Planitiae, and Lada Terra. Features discernable from the mapping include high and lowland plains, evidence of volcanic activity, and impact craters from 6 km to over 50 km across. Some Magellan scientific discoveries are listed, including evidence of a predominant role of ballistic volcanism, extensive and intensive tectonics, a moderate rate of volcanic and tectonic resurfacing, and a low rate of weathering and wind erosion. Other discoveries concerning techntonics, volcanism, impact cratering, and exogenous resurfacing are also listed. Magellan image coverage is discussed, and a chronology of the development of VOIR and Magellan is provided

340

Hot-spot evolution and the global tectonics of Venus  

Science.gov (United States)

The global tectonics of Venus may be dominated by plumes rising from the mantle and impinging on the lithosphere, giving rise to hot spots. Global sea-floor spreading does not take place, but direct convective coupling of mantle flow fields to the lithosphere leads to regional-scale deformation and may allow lithospheric transport on a limited scale. A hot-spot evolutionary sequence comprises (1) a broad domal uplift resulting from a rising mantle plume, (2) massive partial melting in the plume head and generation of a thickened crust or crustal plateau, (3) collapse of dynamic topography, and (4) creep spreading of the crustal plateau. Crust on Venus is produced by gradual vertical differentiation with little recycling rather than by the rapid horizontal creation and consumption characteristic of terrestrial sea-floor spreading.

Phillips, R. J.; Grimm, R. E.; Malin, M. C.

1991-05-01

 
 
 
 
341

Could plate tectonics on Venus be concealed by volcanic deposits  

Science.gov (United States)

The present investigation is supplementary to a study reported by Kaula and Phillips (1981). From an analysis of Pioneer Venus altimetry, Kaula and Phillips had inferred that any heat loss from the planet by plate tectonics must be small compared to that from the earth. However, it has been suggested by others that plate tectonic may exist on Venus, but that the expected 'square root of s' dependence of the topographic drop off is not observed because it is concealed by lava flows. The present investigation has the objective to conduct an examination whether this suggestion of concealment by lava flow is correct. On the basis of the performed analysis, it is concluded that the results obtained by Kaula and Phillips appear to be well justified.

Kaula, W. M.; Muradian, L. M.

1982-01-01

342

Instantaneous three-dimensional thermal structure of the South Polar Vortex of Venus  

Science.gov (United States)

The Venus thermal radiation spectrum exhibits the signature of CO2 absorption bands. By means of inversion techniques, those bands enable the retrieval of atmospheric temperature profiles. We have analyzed VIRTIS-M-IR night-side data obtaining high-resolution thermal maps of the Venus south polar region between 55 and 85 km altitudes. This analysis is specific to three Venus Express orbits where the vortex presents different dynamical configurations. The cold collar is clearly distinguishable centered at ?62 km (?100 mbar) altitude level. On average, the cold collar is more than 15 K colder than the pole, but its specific temperature varies with time. In the three orbits under investigation the South Polar Vortex appears as a vertically extended hot region close to the pole and squeezed by the cold collar between altitudes 55 and 67 km but spreading equatorwards at about 74 km. Both the instantaneous temperature maps and their zonal averages show that the top altitude limit of the thermal signature from the vortex is at ?80 km altitude, at least on the night-side of the planet. The upper part of the atmosphere (67-85 km) is more homogeneous and has long-scale horizontal temperature differences of about 25 K over horizontal distances of ?2000 km. The lower part (55-67 km) shows more fine-scale structure, creating the vortex morphology, with thermal differences of up to about 50 K over the same altitude range and ?500 km horizontal distances. This lower part of the atmosphere is highly affected by the upper cloud deck, leading to stronger local temperature variations and larger uncertainties in the retrieval. From the temperature maps, we also study the vertical stability of different atmospheric layers for the three vortex configurations. The static stability is always positive (ST > 0) in the considered altitude range (55-85 km) and in the whole polar vortex. The cold collar is the most vertically stable structure at polar latitudes, while the vortex and sub-polar latitudes show lower stability values. Furthermore, the hot filaments present within the vortex exhibit lower stability values than their surroundings. The layer between 62 and 67 km resulted to be the most stable. These results are in good agreement with conclusions from previous radio occultation analyses.

Garate-Lopez, I.; García Muñoz, A.; Hueso, R.; Sánchez-Lavega, A.

2015-01-01

343

Further results of the Pioneer Venus nephelometer experiment  

Science.gov (United States)

Backscattering data for the nephelometer experiments conducted aboard the Pioneer Venus mission probes, including data up to the highest altitudes measured by the probes, are presented. A few small signals were detected below the main cloud deck. Ambient radiation was measured at near-ultraviolet and visible wavelengths; the variation of extinction of near-ultraviolet with altitude is inferred. Ambient radiance decreased more rapidly at 530 than at 745 nanometers in the lower atmosphere.

Blamont, J.; Ragent, B.

1979-01-01

344

Evolution of the Atmosphere and Climate of Venus  

Science.gov (United States)

We will review the evolution of the atmosphere and climate of Venus, with a focus on the apparent divergence from early more Earth-like conditions. We will examine what constraints can be put on the nature and timing of this divergence, and in particular on the history and role of water in affecting the evolution of Venus. Venus, in comparison with Earth, is strikingly dry. As our understanding of terrestrial planet evolution has increased, the importance of water abundance as a substance controlling many evolutionary factors has become increasingly clear. This is true of biological evolution, as the presence of liquid water is widely regarded as the key to the possibility of finding "life as we know it" on other worlds. It is also true of geological and climatic evolution. Water is among the most important climatically active atmospheric gasses on the terrestrial planets. It is also a controlling variable for tectonic style and geologic processes, as well as a mediator of surfaceatmosphere chemical reactions. First, we will discuss what is known about the accretion process, the initial conditions of a primordial Venusian atmosphere, and how the differing history of late large impacts (lack of a moon-forming impact, or combination of large impacts that largely cancelled angular momentum) may have affected these initial conditions. Then we will review what is known about atmospheric loss processes and in particular the constraints on loss of water over time. The current state of modeling of the runaway or moist greenhouse will be reviewed, in the context of recent work trying to establish theoretical limits for the inner radius of the circumstellar habitable zone and its movement with stellar evolution. The coupling between of geological and tectonic evolution and the atmosphere and climate will be reviewed, including climate feedbacks, which are operating today, depending on the level of current geological activity. Finally we will discuss the prospects for improving constraints on the atmospheric and climatic evolution of Venus with measurements made by future missions.

Grinspoon, D.; Bullock, M.

2014-04-01

345

Submillimeter mapping of mesospheric minor species on Venus with ALMA  

Science.gov (United States)

ALMA offers a unique opportunity to map mesospheric species on Venus. During Cycle 0, we have observed Venus on November 14 and 15, 2011, using the compact configuration of ALMA. The diameter of Venus was 11 arcsec and the illumination factor was about 90 percent. Maps of CO, SO, SO2, and HDO have been built from transitions recorded in the 335-347 GHz frequency range. The mesospheric thermal profile has been inferred using the CO transition at 345.795 GHz. From the integrated spectrum of SO recorded on Nov. 14 at 346.528 GHz, we find that the best fit is obtained with a cut-off in the SO vertical distribution at about 88 km and a mean mixing ratio of about 8.0 ppb above this level. In the case of SO2, as for SO, we find that the best fit is obtained with a cut-off at about 88 km; the SO2 mixing ratio above this level is about 12 ppb. The map of HDO is retrieved from the 335.395 GHz transition. Assuming a typical D/H ratio of 200 times the terrestrial value in the mesosphere of Venus, we find that the disk averaged HDO spectrum is consistent with a H2O mixing ratio of about 2.5 ppm, constant with altitude. Our results are in good agreement with previous single dish submillimeter observations (Sandor and Clancy, Icarus 177, 129, 2005; Gurwell et al. Icarus 188, 288, 2007; Sandor et al. Icarus 208, 49, 2010; Icarus 217, 836, 2012), as well as with the predictions of photochemical models (Zhang et al. Icarus 217, 714, 2012).

Encrenaz, Therese; Moreno, Raphael; Moullet, Arielle; Lellouch, Emmanuel; Fouchet, Thierry

2014-05-01

346

Geologic map of the Carson Quadrangle (V-43), Venus  

Science.gov (United States)

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the venusian atmosphere on October 12, 1994. Magellan had the objectives of (1) improving knowledge of the geologic processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving knowledge of the geophysics of Venus by analysis of venusian gravity. The Magellan spacecraft carried a 12.6-cm radar system to map the surface of Venus. The transmitter and receiver systems were used to collect three datasets: synthetic aperture radar (SAR) images of the surface, passive microwave thermal emission observations, and measurements of the backscattered power at small angles of incidence, which were processed to yield altimetric data. Radar imaging and altimetric and radiometric mapping of the venusian surface were done in mission cycles 1, 2, and 3, from September 1990 until September 1992. Ninety-eight percent of the surface was mapped with radar resolution of approximately 120 meters. The SAR observations were projected to a 75-m nominal horizontal resolution; these full-resolution data compose the image base used in geologic mapping. The primary polarization mode was horizontal-transmit, horizontal-receive (HH), but additional data for selected areas were collected for the vertical polarization sense. Incidence angles varied from about 20° to 45°. High-resolution Doppler tracking of the spacecraft was done from September 1992 through October 1994 (mission cycles 4, 5, 6). High-resolution gravity observations from about 950 orbits were obtained between September 1992 and May 1993, while Magellan was in an elliptical orbit with a periapsis near 175 kilometers and an apoapsis near 8,000 kilometers. Observations from an additional 1,500 orbits were obtained following orbitcircularization in mid-1993. These data exist as a 75° by 75° harmonic field.

Bender, Kelly C.; Senske, David A.; Greeley, Ronald

2000-01-01

347

The structure of Venus' middle atmosphere and ionosphere.  

Science.gov (United States)

The atmosphere and ionosphere of Venus have been studied in the past by spacecraft with remote sensing or in situ techniques. These early missions, however, have left us with questions about, for example, the atmospheric structure in the transition region from the upper troposphere to the lower mesosphere (50-90 km) and the remarkably variable structure of the ionosphere. Observations become increasingly difficult within and below the global cloud deck (ionosphere. PMID:18046400

Pätzold, M; Häusler, B; Bird, M K; Tellmann, S; Mattei, R; Asmar, S W; Dehant, V; Eidel, W; Imamura, T; Simpson, R A; Tyler, G L

2007-11-29

348

Venus atmosphere profile from a maximum entropy principle  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The variational method with constraints recently developed by Verkley and Gerkema to describe maximum-entropy atmospheric profiles is generalized to ideal gases but with temperature-dependent specific heats. In so doing, an extended and non standard potential temperature is introduced that is well suited for tackling the problem under consideration. This new formalism is successfully applied to the atmosphere of Venus. Three well defined regions emerge in this atmosphere up ...

Epele, L. N.; Fanchiotti, H.; Garci?a Canal, C. A.; Pacheco, A. F.; San?udo, J.

2007-01-01

349

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Traditionally, stellar radiation has been the only heat source considered capable of determining global climate on long timescales. Here, we show that terrestrial exoplanets orbiting low-mass stars may be tidally heated at high-enough levels to induce a runaway greenhouse for a long-enough duration for all the hydrogen to escape. Without hydrogen, the planet no longer has water and cannot support life. We call these planets “Tidal Venuses” and the phenomenon a “tidal greenhouse.” Tida...

Barnes, Rory; Mullins, Kristina; Goldblatt, Colin; Meadows, Victoria S.; Kasting, James F.; Heller, Rene?

2012-01-01

350

A high resolution gravity model for Venus - GVM-1  

Science.gov (United States)

A spherical harmonic model of the gravitational field of Venus complete to degree and order 50 has been developed using the S-band Doppler tracking data of the Pioneer Venus Orbiter (PVO) collected between 1979 and 1982. The short wavelengths of this model could only be resolved near the PVO periapse location (about 14 deg N latitude), therefore a priori constraints were applied to the model to bias poorly observed coefficients towards zero. The resulting model has a half-wavelength resolution of 400 km near the PVO periapse location, but the resolution degrades to greater than 1000 km near the poles. This gravity model correlates well with a degree 50 spherical harmonic expansion of the Venus topography derived from a combination of Magellan and PVO data. New tracking data from Magellan's gravity mission should provide some improvement to this model, although a complete model of the Venusian gravity field will depend on tracking of Magellan after the circularization of its orbit using aerobraking.

Nerem, R. S.; Bills, B. G.; Mcnamee, J. B.

1993-01-01

351

Magellan radar to reveal secrets of enshrouded Venus  

International Nuclear Information System (INIS)

Imaging Venus with a synthetic aperture radar (SAR) with 70 percent global coverage at 1-km optical line-pair resolution to provide a detailed global characterization of the volcanic land-forms on Venus by an integration of image data with altimetry is discussed. The Magellan radar system uses navigation predictions to preset the radar data collection parameters. The data are collected in such a way as to preserve the Doppler signature of surface elements and later they are transmitted to the earth for processing into high-resolution radar images. To maintain high accuracy, a complex on-board filter algorithm allows the altitude control logic to respond only to a narrow range of expected photon intensity levels and only to signals that occur within a small predicted interval of time. Each mapping pass images a swath of the planet that varies in width from 20 to 25 km. Since the orbital plane of the spacecraft remains fixed in the inertial space, the slow rotation of Venus continually brings new areas into view of the spacecraft

352

Glory revealed in disk-integrated photometry of Venus  

CERN Document Server

Context. Reflected light from a spatially unresolved planet yields unique insight into the overall optical properties of the planet cover. Glories are optical phenomena caused by light that is backscattered within spherical droplets following a narrow distribution of sizes; they are well known on Earth as localised features above liquid clouds. Aims. Here we report the first evidence for a glory in the disk-integrated photometry of Venus and, in turn, of any planet. Methods. We used previously published phase curves of the planet that were reproduced over the full range of phase angles with model predictions based on a realistic description of the Venus atmosphere. We assumed that the optical properties of the planet as a whole can be described by a uniform and stable cloud cover, an assumption that agrees well with observational evidence. Results. We specifically show that the measured phase curves mimic the scattering properties of the Venus upper-cloud micron-sized aerosols, also at the small phase angles ...

Muñoz, A García; Sánchez-Lavega, A

2014-01-01

353

Variations in effective compensation depth across Aphrodite Terra, Venus  

International Nuclear Information System (INIS)

Aphrodite Terra is the largest elevated terrain on Venus and it serves as a focal point in current discussions of global tectonic style. Using the topography and gravity data acquired by the Pioneer Venus Orbiter (PVO) the authors have estimated an effective depth of Airy compensation for each of 75 orbital arcs that provide fairly uniform areal coverage of the entire province. The most pronounced pattern that emerges is a general increase in compensation depth to the east. The most rapid change occurs near 135 degree; the average west of there is 70 km, while the average to the east is 230 km. Superimposed on this larger trend are five distinctive regional patterns, four well defined peaks and one interval of widely scattered and poorly constrained depths. The maxima in compensation depth are well correlated with regional topographic highs. While these observations are easily reconciled with the general notion that Aphrodite is a region of crustal divergence, the great depth of compensation is difficult to accord with the more specific suggestion that Aphrodite is a terrestrial type divergent plate margin. The alternative suggestion that Aphrodite, and the other equatorial highlands on Venus, are surface manifestations of hot upwelling mantle plumes is consistent both with the great depths of compensation and with the pattern of regional peaks and intervening troughs. The broader scale increase in effective depth of compensation from west to east is more enigmatic, bion from west to east is more enigmatic, but it might reflect an age progression of the plumes

354

Comparison of modern lattice codes, MCNP and other transport codes for the VENUS-1 and VENUS-2 cores  

International Nuclear Information System (INIS)

Regarding fission rate distributions, the modern lattice codes CASMO-4 and APOLLO2-A show good agreement with both MCNP solutions and with experimental data, the quality being comparable to MCNP; with the codes MOCA, VARIANT, and THREEDANT, which use pin cell homogenized few group cross sections with 5 or 18 energy groups, the C/E ratio in the fission rate distributions exhibits a slightly higher tilt from the core centre to the periphery. The overestimation of the fission rates in the MOX zone in VENUS-2 seems to be to a large extent a MOX effect, since the overestimation in the outer rows of the VENUS-1 UOX core is substantially lower. This effect is seen more or less in all solutions. Although this may be attributed to nuclear library data, the transition from JEF2.2 to JEFF3.1 does not change the results significantly. (orig.)

355

Comparison of modern lattice codes, MCNP and other transport codes for the VENUS-1 and VENUS-2 cores  

Energy Technology Data Exchange (ETDEWEB)

Regarding fission rate distributions, the modern lattice codes CASMO-4 and APOLLO2-A show good agreement with both MCNP solutions and with experimental data, the quality being comparable to MCNP; with the codes MOCA, VARIANT, and THREEDANT, which use pin cell homogenized few group cross sections with 5 or 18 energy groups, the C/E ratio in the fission rate distributions exhibits a slightly higher tilt from the core centre to the periphery. The overestimation of the fission rates in the MOX zone in VENUS-2 seems to be to a large extent a MOX effect, since the overestimation in the outer rows of the VENUS-1 UOX core is substantially lower. This effect is seen more or less in all solutions. Although this may be attributed to nuclear library data, the transition from JEF2.2 to JEFF3.1 does not change the results significantly. (orig.)

Zwermann, Winfried; Langenbuch, Siegfried [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) mbH, Garching (Germany); Alander, Alexandra; Magat, Philippe; Timm, Wolf [AREVA NP, Erlangen (Germany); AREVA NP, Paris (France)

2008-07-01

356

A Prototype Flux-Plate Heat-Flow Sensor for Venus Surface Heat-Flow Determinations  

Science.gov (United States)

Venus is the most Earth-like planet in the Solar System in terms of size, and the densities of the two planets are almost identical when selfcompression of the two planets is taken into account. Venus is the closest planet to Earth, and the simplest interpretation of their similar densities is that their bulk compositions are almost identical. Models of the thermal evolution of Venus predict interior temperatures very similar to those indicated for the regions of Earth subject to solid-state convection, but even global analyses of the coarse Pioneer Venus elevation data suggest Venus does not lose heat by the same primary heat loss mechanism as Earth, i.e., seafloor spreading. The comparative paucity of impact craters on Venus has been interpreted as evidence for relatively recent resurfacing of the planet associated with widespread volcanic and tectonic activity. The difference in the gross tectonic styles of Venus and Earth, and the origins of some of the enigmatic volcano-tectonic features on Venus, such as the coronae, appear to be intrinsically related to Venus heat loss mechanism(s). An important parameter in understanding Venus geological evolution, therefore, is its present surface heat flow. Before the complications of survival in the hostile Venus surface environment were tackled, a prototype fluxplate heat-flow sensor was built and tested for use under synthetic stable terrestrial surface conditions. The design parameters for this prototype were that it should operate on a conforming (sand) surface, with a small, self-contained power and recording system, capable of operating without servicing for at least several days. The precision and accuracy of the system should be < 5 mW/sq m. Additional information is included in the original extended abstract.

Morgan, Paul; Reyes, Celso; Smrekar, Suzanne E.

2005-01-01

357

Radar scattering mechanisms within the meteor crater ejecta blanket: Geologic implications and relevance to Venus  

Science.gov (United States)

Simple impact craters are known to occur on all of the terrestrial planets and the morphologic expression of their ejecta blankets is a reliable indicator of their relative ages on the Moon, Mars, Mercury, and most recently for Venus. It will be crucial for the interpretation of the geology of Venus to develop a reliable means of distinguishing smaller impact landforms from volcanic collapse and explosion craters, and further to use the observed SAR characteristics of crater ejecta blankets (CEB) as a means of relative age estimation. With these concepts in mind, a study was initiated of the quantitative SAR textural characteristics of the ejecta blanket preserved at Meteor Crater, Arizona, the well studied 1.2 km diameter simple crater that formed approx. 49,000 years ago from the impact of an octahedrite bolide. While Meteor Crater was formed as the result of an impact into wind and water lain sediments and has undergone recognizable water and wind related erosion, it nonetheless represents the only well studied simple impact crater on Earth with a reasonably preserved CEB. Whether the scattering behavior of the CEB can provide an independent perspective on its preservation state and style of erosion is explored. Finally, airborne laser altimeter profiles of the microtopography of the Meteor Crater CEB were used to further quantify the subradar pixel scale topographic slopes and RMS height variations for comparisons with the scattering mechanisms computed from SAR polarimetry. A preliminary assessment was summarized of the L-band radar scattering mechanisms within the Meteor Crater CEB as derived from a NASA/JPL DC-8 SAR Polarimetry dataset acquired in 1988, and the dominant scattering behavior was compared with microtopographic data (laser altimeter profiles and 1:10,000 scale topographic maps).

Garvin, J. B.; Campbell, B. A.; Zisk, S. H.; Schaber, Gerald G.; Evans, C.

358

Venus Kinase Receptors: prospects in signalling and biological functions of these invertebrate receptors  

Directory of Open Access Journals (Sweden)

Full Text Available Venus Kinase Receptors (VKRs form a family of invertebrate receptor tyrosine kinases (RTKs initially discovered in the parasitic platyhelminth Schistosoma mansoni. VKRs are single transmembrane receptors which contain an extracellular Venus Flytrap (VFT structure similar to the ligand binding domain of G Protein Coupled Receptors of class C, and an intracellular Tyrosine Kinase domain close to that of Insulin Receptors. VKRs are found in a large variety of invertebrates from cnidarians to echinoderms, and are highly expressed in larval stages and in gonads, suggesting a role of these proteins in embryonic and larval development as well as in reproduction. Vkr gene silencing could demonstrate the function of these receptors in oogenesis as well as in spermatogenesis in Schistosoma .mansoni. VKRs are activated by amino-acids, and highly responsive to arginine. As many other RTKs, they form dimers when activated by ligands and induce intracellular pathways involved in protein synthesis and cellular growth, such as MAPK and PI3K/Akt/S6K pathways. VKRs are not present in vertebrates, nor in some invertebrate species. Questions remain open about the origin of this little-known RTK family in evolution and its role in emergence and specialization of Metazoa. What is the meaning of maintenance or loss of VKR in some phyla or species in terms of development and physiological functions? The presence of VKRs in invertebrates of economical and medical importance, such as pests, vectors of pathogens and platyhelminth parasites, and the implication of these RTKs in gametogenesis and reproduction processes are valuable reasons to consider VKRs as interesting targets in new programs for eradication/ control of pests and infectious diseases, with the main advantage in the case of parasite targeting that VKR counterparts are absent from the vertebrate host kinase panel.

ColetteDissous

2014-05-01

359

Thermal Structure of Venus Night-Side Atmosphere as Seen by Ground-Based Heterodyne Observations at 10?m  

Science.gov (United States)

The structure of Venus atmosphere has been the target of intense studies in the past decade. The recent space mission Venus Express (VEX) has shed light on many open question concerning the thermal and dynamical behavior of its atmosphere. In the vicinity of the imminent shut down of the space craft, the importance of ground-based observations increases significantly. We want to introduce a new and unique opportunity to retrieve temperature profiles from the Venusian night-side atmosphere, using ground-based observation techniques. The application of heterodyne spectroscopy in the infrared enables the capability to resolve single molecular ro-vibrational transition features. Pressure broadened CO2 absorption lines, observable on the Venusian night side, have proven to be a good tracer for analyzing the predominant temperature. The profiles originate from the altitude region between the cloud top at ~65km (~100hPa) and 95km (~0.1hPa). With a spectral limited altitude resolution of 5.3km, vertical profiles can be variably deduced on various position on the planet. Initial results from two observing campaigns in March (A) and May (B) 2012 will be presented. During campaign A, Venus was shortly after maximum Eastern elongation and about 45% illuminated, while on campaign B, the Planet was close to its latest transit and thus almost completely dark. At each campaign, two different locations on the planet were investigated, by probing the CO2 P(12) transition at 10.5?m. A comparison to space-based data, including a coordinated observation with VEX, performed during campaign B, and the spatial variability of the temperature profiles are under investigation.

Stangier, Tobias; Sornig, Manuela; Hewagama, Tilak; Tellmann, Silvia; Pätzold, Martin; Krause, Pia; Kostiuk, Theodor; Livengood, Timothy

2014-05-01

360

Venus volcanism - Classification of volcanic features and structures, associations, and global distribution from Magellan data  

Science.gov (United States)

A classification and documentation of the range of morphologic features and structures of volcanic origin on Venus, their size distribution, and their global distribution and associations are presented based on a preliminary analysis of Magellan data. Some of the major questions about volcanism on Venus are addressed.

Head, James W.; Crumpler, L. S.; Aubele, Jayne C.; Guest, John E.; Saunders, R. S.

1992-01-01

 
 
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