WorldWideScience
 
 
1

The science return from Venus Express  

Science.gov (United States)

Since the beginning of the space era, Venus has been an attractive target for planetary scientists. Our nearest planetary neighbour and, in size at least, the Earth's twin sister, Venus was expected to be very similar to our planet. However, the first phase of Venus spacecraft exploration (1962-1985) discovered an entirely different, exotic world hidden behind a curtain of dense cloud. The earlier exploration of Venus included a set of Soviet orbiters and descent probes, the Veneras 4 to 14, the US Pioneer Venus mission, the Soviet Vega balloons and the Venera 15, 16 and Magellan radar-mapping orbiters, the Galileo and Cassini flybys, and a variety of ground-based observations. But despite all of this exploration by more than 20 spacecraft, the so-called "morning star" remains a mysterious world!

Svedhem, Håkan; Witasse, Olivier; Titov, Dmitri V.

2005-11-01

2

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

3

International Planetary Science Interoperability: The Venus Express Interface Prototype  

Science.gov (United States)

NASA's Planetary Data System (PDS) and ESA's Planetary Science Archive (PSA) have successfully demonstrated interoperability between planetary science data archives with the Venus Express (VEX) Interface prototype. Because VEX is an ESA mission, there is no memorandum of understanding to archive the data in the PDS. However, using a common communications protocol and common data standards, VEX mission science data ingested into the PSA can be accessed from a user interface at the Atmospheres Node of the PDS, making the science data accessible globally through two established planetary science data portals. The PSA makes scientific and engineering data from ESA's planetary missions accessible to the worldwide scientific community. The PSA consists of online services incorporating search, preview, download, notification and delivery basket functionality. Mission data included in the archive aside from VEX include data from the Giotto, Mars Express, Smart-1, Huygens, and Rosetta spacecraft and several ground-based cometary observations. All data are compatible to the Planetary Data System data standard. The PDS archives and distributes scientific data from NASA planetary missions, astronomical observations, and laboratory measurements. The PDS is sponsored by NASA's Science Mission Directorate. Its purpose is to ensure the long-term usability of NASA data and to stimulate advanced research. The architecture of the VEX prototype interface leverages components from both the PSA and PDS information system infrastructures, a user interface developed at the New Mexico State University, and the International Planetary Data Alliance (IPDA) Planetary Data Access Protocol (PDAP). The VEX Interoperability Project was a key project of the IPDA, whose objective is to ensure world-wide access to planetary data regardless of which agency collects and archives the data. A follow-on IPDA project will adapt the VEX Interoperability protocol for access in JAXA to the Venus Climate Orbiter "Planet C” data.

Sanford Bussard, Stephen; Chanover, N.; Huber, L.; Trejo, I.; Hughes, J. S.; Kelly, S.; Guinness, E.; Heather, D.; Salgado, J.; Osuna, P.

2009-09-01

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

3.6 cm signal attenuation in Venus' lower and middle atmosphere observed by the Radio Science experiment VeRa onboard Venus Express  

Science.gov (United States)

The planet Venus is shrouded within a roughly 20 km thick cloud layer, which extends from the lower to the middle atmosphere (ca. 50 - 70 km). While the clouds are mostly composed of sulfuric acid droplets, a haze layer of sulfuric acid vapor exists below the clouds. Within the cloud and the sub - cloud region Radio signal strength variations (intensity scintillations) caused by atmospheric waves and a decrease in the signal intensity caused by absorption by H2SO4 are observed by radio occultation experiments. The Venus Express spacecraft is orbiting Venus since 2006. The Radio Science Experiment VeRa probes the atmosphere with radio signals at 3.6 cm (XBand) and 13 cm (S-Band) wavelengths. The disturbance of the radio signal intensity is used to investigate the cloud region with respect to atmospheric waves. The absorption of the signal is used to determine the abundance of H2SO4 near the cloud base. This way a detailed study of the H2SO4 abundance within the cloud and sub - cloud region is possible. Results from the intensity scintillations within the cloud deck are presented and compared with gravity wave studies based on temperature variations inferred from VeRa soundings. Vertical absorptivity profiles and resulting sulfuric acid vapor profiles are presented and compared with previous missions. A distinct latitudinal dependence and a southern northern symmetry are clearly visible.

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

2012-09-01

6

Microwave absorptivity by sulfuric acid in the Venus atmosphere: First results from the Venus Express Radio Science experiment VeRa  

Science.gov (United States)

The Venus Express (VEX) Radio Science experiment VeRa utilizes radio occultation techniques to investigate the Venus atmosphere over a wide range of latitudes. Radio attenuation measurements with the VEX 3.6 cm (X-band) signal provide information on the absorptivity distribution within the Venus cloud deck. The combined results from 6 years of occultation measurements reveal a distinct latitudinal variation in absorptivity in the altitude range from 50 to 55 km. Enhanced absorptivity is observed at equatorial and mid-latitudes (0-50°S), exceeding 0.008 dB/km on the dayside and 0.01 dB/km on the nightside of the southern hemisphere. Poleward of 50°S latitude a decrease in the absorptivity is observed, reaching minimal values at polar latitudes (>70°S), where the absorptivity did not exceed 0.005 dB/km on the dayside and 0.004 dB/km on the nightside. The main absorber of radio waves in the Venus atmosphere, gaseous sulfuric acid, can serve as a tracer for atmospheric motions. The inferred absorptivity was used to determine the abundance of gaseous sulfuric acid. Abundances of about 1-2 ppm are found between 0°S and 70°S latitude in the altitude range from 50 to about 52 km, sometimes increasing to values of about 3 ppm on the dayside and 5 ppm on the nightside near 50 km. The abundance at polar latitudes (>70°S) did not exceed 1 ppm within the considered altitude range. The absorptivity and gaseous sulfuric acid height profiles are compared with previous measurements.

Oschlisniok, J.; Häusler, B.; Pätzold, M.; Tyler, G. L.; Bird, M. K.; Tellmann, S.; Remus, S.; Andert, T.

2012-11-01

7

Results from Venus Express  

Science.gov (United States)

Venus Express has been in orbit around Venus since May 2006 and has since then delivered a large amount of new and unique information on our sister planet. The atmosphere has been mapped in three dimensions and at regular intervals time lapse movies have been generated in order to make detailed characterization of the circulation patterns at different altitudes. The thermal structure has been investigated with several different but complementary techniques to cover the range between 40km and 140 km. The surface temperature has been mapped over a large part of the southern hemisphere and regions with anomalous emissivity have been studied in some detail. The chemical analysis has characterised a large number of species and detected for the first time the radical hydroxyl. Existence of frequent lightning has been inferred from whistler waves detected by the magnetometer. Escape rates of hydrogen, oxygen and helium have been estimated. Recently the pericentre altitude was reduced to 185 km in order to better characterize, in situ, the magnetic fields and energetic particle environment. This talk will provide a summary of the most important results and give a status update of the mission.

Svedhem, Hakan

2008-09-01

8

Small-scale temperature fluctuations seen by the VeRa Radio Science Experiment on Venus Express  

Science.gov (United States)

The Venus Express Radio Science Experiment VeRa retrieves atmospheric profiles in the mesosphere and troposphere of Venus in the approximate altitude range of 40-90 km. A data set of more than 500 profiles was retrieved between the orbit insertion of Venus Express in 2006 and the end of occultation season No. 11 in July 2011. The atmospheric profiles cover a wide range of latitudes and local times, enabling us to study the dependence of vertical small-scale temperature perturbations on local time and latitude. Temperature fluctuations with vertical wavelengths of 4 km or less are extracted from the measured temperature profiles in order to study small-scale gravity waves. Significant wave amplitudes are found in the stable atmosphere above the tropopause at roughly 60 km as compared with the only shallow temperature perturbations in the nearly adiabatic region of the adjacent middle cloud layer, below. Gravity wave activity shows a strong latitudinal dependence with the smallest wave amplitudes located in the low-latitude range, and an increase of wave activity with increasing latitude in both hemispheres; the greatest wave activity is found in the high-northern latitude range in the vicinity of Ishtar Terra, the highest topographical feature on Venus. We find evidence for a local time dependence of gravity wave activity in the low latitude range within ±30° of the equator. Gravity wave amplitudes are at their maximum beginning at noon and continuing into the early afternoon, indicating that convection in the lower atmosphere is a possible wave source. The comparison of the measured vertical wave structures with standard linear-wave theory allows us to derive rough estimates of the wave intrinsic frequency and horizontal wavelengths, assuming that the observed wave structures are the result of pure internal gravity waves. Horizontal wavelengths of the waves at 65 km altitude are on the order of ?300-450 km with horizontal phase speeds of roughly 5-10 m/s.

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

2012-11-01

9

The Venus Express mission  

Science.gov (United States)

Venus evokes the ever-attractive image of a goddess from antiquity, and yet our sister planet, although attractive, is far from hospitable. The reasons for such a great difference between Earth and Venus have still to be understood and so, considering that they are very close in terms of astronomical distances, a mystery is invoked. Whether Earth is a unique planet, for which life was destined, or whether both planets were created under similar circumstances and subsequently evolved in different manners, is fundamental to the understanding of our place in the Solar System and, indeed, perhaps the Universe.

McCoy, Donald; Siwitza, Thorsten; Gouka, Roy

2005-11-01

10

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

11

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

12

Experimental Aerobraking with Venus Express  

Science.gov (United States)

Venus Express has successfully orbited Venus in its polar 24 hour, 250km by 66000 km, orbit since April 2006 and has provided a wealth of new data from our sister planet. Approaching the end of the mission we are now planning an experimental campaign dedicated to aerobraking at altitudes down to as low as about 130km. These low pericentre passes will provide direct measurements of density, temperature, magnetic field and energetic particles in a region not accessible by other methods. Experience of operations and studies of spacecraft responses will be valuable knowledge for possible future missions that might need this techniques as a part of its nominal operations. Aerobraking was considered in the early design phase of the mission but it was fairly soon realised that the nominal mission would not need this. However, a few important design features were maintained in order to allow for this in case it should be needed at a later stage. The inherently stable geometry of the spacecraft configuration and the inclusion of a software mode for aerobraking are the two most important elements from this early design phase. An recent study by industry has determined the constraints for the spacecraft and identified several potential scenarios. The present highly elliptical orbit has as one of its inherent features a downward drift of the pericentre altitude of between 1 and 4 km/day. However, at certain times, when the Sun is in the orbital plane, this drift disappears for a period of up to two weeks. This is a very well suited time to carry out these initial experiments as it is makes operations safer and it reduces the heat input on the spacecraft as the solar panels will be edge-on towards the sun during the aerobraking. Already a number of low altitude operations have been carried out during the so called atmospheric drag campaigns. The spacecraft has then dipped down to altitudes as low as 165 km and a good characterisation of this region has been performed. This collected information will be helpful for the planning of the aerobraking itself.

Svedhem, Hakan

2013-10-01

13

Venus Express and Venus Climate Orbiter: An Opportunity for mutual occultations to investigate the Venus Atmosphere  

Science.gov (United States)

The Venus Express orbiter mission planned for launch in 2005 and the Japanese Planet C Orbiter Mission to Venus planned for launch in 2008 together provide an unprecedented opportunity to investigate the thermal structure of the atmosphere of Venus using the radio occultation technique. As currently planned, the Venus Ex-press will go into a polar orbit (˜18-24 hour period) and Planet C into a near equato-rial orbit (172^o inclination, ˜30 hour period). These orbits will provide many mu-tual occultations between the two satellites, and periodically, occultations with re-spect to the earth. The advantage of the mutual occultations is that the locations and the time-of-day for the occultation zone is not aliased by the celestial Venus-Earth geometry that results in a very biased sampling of latitudes and local times. A simi-lar approach is being considered for investigation of the Martian atmosphere through Mars Scout opportunity (Kursinski et al., 2003). Unfortunately, due to lack of coor-dination and foresight, the opportunity to use the Mars Global Surveyor and the Mars Odyssey orbiters for mutual occultations has been lost. The realization of this invaluable opportunity requires that the communication in-struments on the two orbiters be mutually compatible and capable of receiving and measuring the Doppler shift of the signal between the two orbiters. Further, it is likely that Venus Express will have completed its nominal mission by the time Planet C arrives at Venus, hence the transmitter on Venus Express will need to be left turned so that the atmospheric signature of the Doppler shift in its signal as received on Planet C orbiter can be analyzed to determine the thermal structure, with perhaps 100 m vertical resolution. Such a high vertical resolution has been demon-strated through mutual occultations between the GPS constellation and METSAT on earth (Kursinski et al., 1997). With the looming prospect of a third orbiter around Venus through NASA's Discovery program in the next decade, the opportunity to obtain a unique and extensive sampling of the Venus atmosphere is being presented, and it is up to the mission teams to coordinate their efforts to realize its full potential that minimal resources.

Limaye, S.

2003-04-01

14

SPICAV IR acousto-optic spectrometer experiment on Venus Express  

Science.gov (United States)

SPICAV IR, a part of SPICAV/SOIR suite on Venus Express, is a compact single pixel spectrometer for the spectral range of 0.65-1.7 ?m based on acousto-optical tunable filter (AOTF) technology. SPICAV IR is derived from SPICAM IR operating on Mars Express, the first AOTF spectrometer in the deep space, and adapted for Venus atmosphere measurements. The spectrometer sequentially measures spectra of reflected solar radiation from Venus on the dayside and the emitted Venus radiation in spectral “windows” on the nightside, and works also in solar occultation mode. The spectral range is 0.65-1.1 ?m with spectral resolution of 7.8 cm-1, and 1-1.7 ?m with spectral resolution of 5.2 cm-1. A description of this near-IR instrument, its calibration, in-flight performances, and the modes of operations on Venus’ orbit are presented. A brief overview of the science measurements is given: water vapor measurements in the mesosphere on the day-side and near surface on the nightside, mapping of the O2(a1?g) emission at 1.27 ?m, aerosol studies via polarization and scattering solar radiation at the day-side, and measurements of aerosol properties at the tops of the clouds in solar occultations.

Korablev, Oleg; Fedorova, Anna; Bertaux, Jean-Loup; Stepanov, A. V.; Kiselev, A.; Kalinnikov, Yu. K.; Titov, A. Yu.; Montmessin, F.; Dubois, J. P.; Villard, E.; Sarago, V.; Belyaev, D.; Reberac, A.; Neefs, E.

2012-05-01

15

Characterizing the V1 layer in the Venus ionosphere using VeRa observations from Venus Express  

Science.gov (United States)

The Venus Radio Science Experiment (VeRa) on the Venus Express spacecraft sounds the Venus atmosphere during Earth occultations to obtain vertical profiles of electron density in the ionosphere. The resultant profiles reveal the vertical structure of the Venus ionosphere from the topside down to below the lower layers (VeRa profiles from 2006 to 2012 during which the Sun went from the deep solar minimum of Solar Cycle 23 to the rising solar activity levels of Solar Cycle 24. We investigate how the peak electron density and peak altitude of the V1 layer depend on solar zenith angle. We also characterize the shapes of the V1 layer and show how they are related to the solar activity level. Solar spectra from the Solar EUV Experiment (SEE) on the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft are used to characterize the shapes of the V1 layer with solar activity.

Girazian, Z.; Withers, P.; Fallows, K.; Tarrh, A.; Paetzold, M.; Tellmann, S.; Haesler, B.

2013-12-01

16

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

17

ESA's Venus Express to reach final destination  

Science.gov (United States)

First step: catching Venus To begin to explore our Earth’s hot and hazy sister planet, Venus Express must complete a critical first step, the most challenging one following launch. This involves a set of complex operations and manoeuvres that will inject the spacecraft into orbit. The Venus Orbit Insertion (VOI) manoeuvre allows the spacecraft to reduce its speed relative to Venus, so that it can be captured by the planet’s gravitation. The manoeuvre is a critical one which must proceed at precisely the right place and time. The VOI phase officially started on 4 April and will not be completed until 13 April. It is split into three main sub-phases. The first consists in preparing or initialising the spacecraft for the actual capture manoeuvre so as to avoid the risk of the spacecraft going into safe mode, should parameters unrelated to VOI go off-range. The capture manoeuvre itself consists of a main-engine burn lasting about 50 minutes on the morning of 11 April starting at 09:17 (Central European Summer Time). This is the second main VOI sub-phase. The final sub-phase will be restoring all spacecraft functions, notably resuming communications with Earth and uplinking the commands to be executed during the preliminary ‘capture’ orbit. Orbital capture is controlled by an automatic sequence of predefined commands, uploaded to the spacecraft four days prior to VOI. This sequence is the minimum set needed to perform the main-engine burn. All spacecraft operations are controlled and commanded by the ground control team located at ESA’s European Spacecraft Operations Centre (ESOC) in Darmstadt, Germany. Timeeline of major VOI events (some times subject to change) 4 Aprilacecraft transmitter connected to low gain antenna is switched on. During its interplanetary cruise and during the scientific part of the mission to come, Venus Express communicates with Earth by means of its two high gain antennas. However, during the orbit capture phase (11 April), these two antennas become unusable because of the spacecraft’s required orientation at that time. The low gain antenna, carrying a feeble but instantly recognisable signal, will be transmitting throughout all VOI manoeuvres. This will allow ground controllers to monitor the velocity change during the burn, using NASA’s Deep Space Network’s 70-metre antenna near Madrid, Spain. No other means of communication with the Earth is possible during the capture burn. 5 and 9 April, targeting control manoeuvres. Two time slots are available to adjust course if needed. Given the high accuracy of the course correction performed end of March, Venus Express is currently on the right trajectory for a successful capture into orbit and it is therefore unlikely that either of these two extra slots will be required. 10 to 11 April, final preparations for VOI manoeuvre. 24 to 12 hours before VOI, spacecraft controllers will command Venus Express into its final configuration for the burn. Over the final 12 hours, they will monitor its status, ready to deal with any contingencies requiring last-minute trajectory correction or any revising of the main-engine burn duration. 11 April, 08:03 (CEST), ‘slew’ manoeuvre. This manoeuvre lasts about half an hour and rotates Venus Express so that the main engine faces the direction of motion. Thanks to this, the burn will slow down (rather than accelerate) the spacecraft. 11 April, 09:17 (CEST), main-engine burn starts. A few minutes after firing of the spacecraft thrusters to make sure the propellant settles in the feed lines to the main engine, the latter will begin its 50-minute long burn, ending at 10:07. This thrust will reduce the initial velocity of 29 000 kilometres per hour (in relation to Venus) by 15 percent, allowing capture. Venus Express will settle into its preliminary, elongated nine-day orbit. On capture, it will be at about 120 million kilometres from the Earth and, at its nearest point, within 400 km of the surface of Venus. During the burn, at 09:45 (CEST), Venus Express will disappear behind the planet and will not be visi

2006-04-01

18

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

19

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

20

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

 
 
 
 
21

Venus Express en route to probe the planet's hidden mysteries  

Science.gov (United States)

Venus Express will eventually manoeuvre itself into orbit around Venus in order to perform a detailed study of the structure, chemistry and dynamics of the planet's atmosphere, which is characterised by extremely high temperatures, very high atmospheric pressure, a huge greenhouse effect and as-yet inexplicable "super-rotation" which means that it speeds around the planet in just four days. The European spacecraft will also be the first orbiter to probe the planet's surface while exploiting the "visibility windows" recently discovered in the infrared waveband. The 1240 kg mass spacecraft was developed for ESA by a European industrial team led by EADS Astrium with 25 main contractors spread across 14 countries. It lifted off onboard a Soyuz-Fregat rocket, the launch service being provided by Starsem. The lift-off from the Baikonur Cosmodrome in Kazakstan this morning took place at 09:33 hours local time (04:33 Central European Time). Initial Fregat upper-stage ignition took place 9 minutes into the flight, manoeuvring the spacecraft into a low-earth parking orbit. A second firing, 1 hour 22 minutes later, boosted the spacecraft to pursue its interplanetary trajectory. Contact with Venus Express was established by ESA's European Space Operations Centre (ESOC) at Darmstadt, Germany approximately two hours after lift-off. The spacecraft has correctly oriented itself in relation to the sun and has deployed its solar arrays. All onboard systems are operating perfectly and the orbiter is communicating with the Earth via its low-gain antenna. In three days' time, it will establish communications using its high-gain antenna. Full speed ahead for Venus Venus Express is currently distancing itself from the Earth full speed, heading on its five-month 350 million kilometre journey inside our solar system. After check-outs to ensure that its onboard equipment and instrument payload are in proper working order, the spacecraft will be mothballed, with contact with the Earth being reduced to once daily. If needed, trajectory correction manoeuvres can go ahead at the half-way stage in January. When making its closest approach, Venus Express will face far tougher conditions than those encountered by Mars Express on nearing the Red Planet. For while Venus's size is indeed similar to that of the Earth, its mass is 7.6 times that of Mars, with gravitational attraction to match. To resist this greater gravitational pull, the spacecraft will have to ignite its main engine for 53 minutes in order to achieve 1.3 km/second deceleration and place itself into a highly elliptical orbit around the planet. Most of its 570 kg of propellant will be used for this manoeuvre. A second engine firing will be necessary in order to reach final operational orbit: a polar elliptical orbit with 12-hour crossings. This will enable the probe to make approaches to within 250 km of the planet's surface and withdraw to distances of up to 66 000 km, so as to carry out close-up observations and also get an overall perspective. Exploring other planets to better understand planet Earth "The launch of Venus Express is a further illustration of Europe's determination to study the various bodies in our solar system", stressed Professor David Southwood, the Director of ESA's science programmes. "We started in 2003 with the launch of Mars Express to the Red Planet and Smart-1 to the Moon and both these missions have amply exceeded our expectations. Venus Express marks a further step forward, with a view to eventually rounding off our initial overview of our immediate planetary neighbours with the BepiColombo mission to Mercury to be launched in 2013." "With Venus Express, we fully intend to demonstrate yet again that studying the planets is of vital importance for life here on Earth", said Jean Jacques Dordain, ESA Director General. "To understand climate change on Earth and all the contributing factors, we cannot make do with solely observing our own planet. We need to decipher the mechanics of the planetary atmosphere in

2005-11-01

22

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

23

Venus Express observations of ULF and ELF waves in the Venus ionosphere: Wave properties and sources  

Science.gov (United States)

Electrical activity in a planetary atmosphere enables chemical reactions that are not possible under conditions of local thermodynamic equilibrium. In both the Venus and terrestrial atmospheres, lightning forms nitric oxide. Despite the existence of an inventory of NO at Venus like the Earth’s, and despite observations of the signals expected from lightning at optical, VLF, and ELF frequencies, the existence of Venus lightning still is met with some skepticism. The Venus Express mission was equipped with a fluxgate magnetometer gradiometer system sampling at rates as high as 128 Hz, and making measurements as low as 200 km altitude above the north polar regions of Venus. However, significant noise levels are present on the Venus Express spacecraft. Cleaning techniques have been developed to remove spacecraft interference at DC, ULF, and ELF frequencies, revealing two types of electromagnetic waves, a transverse right-handed guided mode, and a linearly polarized compressional mode. The propagation of both types of signals is sensitive to the magnetic field in ways consistent with propagation from a distant source to the spacecraft. The linearly polarized compressional waves generally are at lower frequencies than the right-handed transverse waves. They appear to be crossing the usually horizontal magnetic field. At higher frequencies above the lower hybrid frequency, waves cannot enter the ionosphere from below when the field is horizontal. The arrival of signals at the spacecraft is controlled by the orientation of the magnetic field. When the field dips into the atmosphere, the higher frequency guided mode above the lower hybrid frequency can enter the ionosphere by propagating along the magnetic field in the whistler mode. These properties are illustrated with examples from five orbits during Venus Express’ first year in orbit. These properties observed are consistent with the linearly polarized compressional waves being produced at the solar wind interface and the transverse guided waves being produced in the atmosphere.

Russell, C. T.; Leinweber, H.; Hart, R. A.; Wei, H. Y.; Strangeway, R. J.; Zhang, T. L.

2013-11-01

24

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

25

Lightning on Venus? Searching for optical evidence with VIRTIS on Venus Express  

Science.gov (United States)

The Venus Express mission has been observing the Venusian Atmosphere continuously since 2006, producing great amounts of hyper-spectral data from the Visible to the Near InfraRed. Although the occurrence of lightning in the Venus atmosphere has been published several times in the past years, always on the basis of detected electromagnetic pulses, the subject is still controversial. It is generally agreed that an optical observation of the phenomenon would settle the issue. We will show here some details of the analysis of the whole data collection of hyperspectral images produced by the VIRTIS instrument in the visible and infrared range, with description of the method and preliminary results.

Cardesín Moinelo, A.; García Muñoz, A.; Piccioni, G.

2013-09-01

26

Sulfur dioxide in the Venus atmosphere measured by SOIR on board Venus Express  

Science.gov (United States)

SO2 is a key constituent of the Venus mesosphere, playing an important role in the atmosphere chemistry, as it is a product of the photodisociation of the clouds constituent, H2SO4. New SO2 observations are important in the frame of constraining Global Computation Models (GCM), which simulate the circulation and the chemistry of the Venus atmosphere. The SOIR instrument flying on board the Venus Express spacecraft records infrared spectra of the Venus atmosphere, using the solar occultation technique. Amongst the species absorbing in the SOIR wavelength range, sulfur dioxide presents a weak band, from which regular observations are obtained in the 60 to 100 km altitude region. We derive number density and volume mixing ratio vertical profiles. Total density and temperature profiles are obtained from the carbon dioxide number density profiles. This study presents the latitude and temporal variations observed between 2006 and 2013. The results are compared to literature data and discussed. Future work will consist of including and comparing the data to Venus GCM.

Mahieux, Arnaud; Carine Vandaele, Ann; Drummond, Rachel; Robert, Séverine; Wilquet, Valérie; Belyaev, Denis; Bertaux, Jean-Loup

2014-05-01

27

Results of the Venus Express Aerobraking Campaign  

Science.gov (United States)

After a very successful mission orbiting Venus for more than 8 years, slowly the fuel is running out and the spacecraft will inevitably one day end up in the hot and acid atmosphere of the planet. Being near the end of the mission and in a position to accept some risk to the spacecraft we decided to take the opportunity to dip down deep into the atmosphere, to around 130 km, in a controlled manner, in order to make detailed in situ investigations of this for remote sensing instruments difficult to access region. The on board accelerometers gave direct measurements of the deceleration which in turn is directly proportional to the local atmospheric density. This provided an excellent way to study both the total density profile throughout the orbital arc in the atmosphere and small scale density variations in the region of the pericentre. The spacecraft behaved perfectly well throughout the whole campaign and provided a wealth of data both on the atmosphere and on the response of the spacecraft to the harsh environment with strong heat loads and some dynamic stress. At the time of the campaign the pericentre was located near the terminator at about 75 degrees Northern latitude. Aerobraking is a very efficient method of reducing the pericentre velocity and thereby reducing the apocentre altitude and the orbital period.The so called "walk-in" phase started at an altitude of 190 km on 17 May and the campaign ended on 11 July, after having reached a lowest altitude of 129.2 km. Subsequently, a series of orbit control manoeuvres lifted up the pericentre to 460 km altitude and the science activities were resumed after a thorough check-out of the spacecraft. We have detected a highly variable atmosphere, both on a day to day basis and within the individual pericentre passes. The duration of each pass was approximately 100 s and the maximum dynamic pressure achieved was more than 0.75 N/m2, probably a record for a spacecraft that continued its operation afterwards. The orbital period was reduced over the duration of the campaign changing from 24 hours to 22 hours 20 minutes.

Svedhem, Hakan; Müller-Wodarg, Ingo

2014-11-01

28

Analysis of Venus Express optical extinction due to aerosols in the upper haze of Venus  

Science.gov (United States)

Observations by the SPICAV/SOIR instruments aboard the Venus Express (VEx) spacecraft have revealed that the upper haze (UH) of Venus, between 70 and 90 km, is variable on the order of days to weeks and that it is populated by two particle modes. Gao et al. (submitted, Icarus, 2013) posit that one mode is made up of cloud particles that have diffused upwards from the main sulfuric acid cloud deck below, while the other mode is generated in situ by nucleation of sulfuric acid droplets on meteoric dust. They also propose that the observed variability in the UH is caused in part by vertical transient winds. They test this hypothesis by simulating a column of the Venus atmosphere from 40 to 100 km above the surface using a model based upon the Community Aerosol and Radiation Model for Atmospheres (CARMA). In this work, we significantly extend the analysis using the new more detailed SOIR/VeRa VEx temperature profiles which better constrain the observed strong CO2 15-micron cooling emission and 4.3-?m near-IR heating in Venus' atmosphere (and consistent with Venus Thermospheric General Circulation Model (VTGCM) simulations of Brecht et al. (2011)). We discuss our new results in context of the recent VEx observations (Wilquet et al., Icarus 217, 2012) with an intercomparison with the PVO data. We will also discuss similarities and differences arising from the PVO and VEx epochs where they exist. Additionally we report on our efforts self-consistently applying the VTGCM to constrain the degree to which effects due to vertical transient wind simulations can establish variability timescales and number density profiles that match VEx observations.

Parkinson, C. D.; Bougher, S. W.; Schulte, R.; Gao, P.; Yung, Y. L.; Vandaele, A.; Wilquet, V.; Mahieux, A.; Tellmann, S.

2013-12-01

29

Venus Express observations of magnetic field fluctuations in the magnetosheath  

Science.gov (United States)

Magnetic field fluctuations within a planetary magnetosheath play an important role in the solar wind interaction with the planet, since they can reconfigure the plasma flow and the magnetic field and transfer energy from the bow shock to the lower boundary. Many studies have been presented on the fluctuations in the terrestrial magnetosheath; however, hardly any studies have so far been carried out for Venusian magnetosheath fluctuations, except for Luhmann et al. [1983] and Vörös et al. [2008] who performed some case studies on the magnetosheath fluctuations at Venus. It was shown that the fluctuations are probably convected from the vicinity of the quasi-parallel bow shock along the streamlines. Based on the Venus Express observations in 2006 and 2007, we investigate the spatial distributions of magnetic field fluctuations in the Venus magnetosheath statistically.

Du, J.; Wang, C.; Zhang, T. L.; Volwerk, M.; Delva, M.; Baumjohann, W.

2008-12-01

30

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

31

Aerobraking at Venus: A science and technology enabler  

Science.gov (United States)

Venus remains one of the great unexplored planets in our solar system, with key questions remaining on the evolution of its atmosphere and climate, its volatile cycles, and the thermal and magmatic evolution of its surface. One potential approach toward answering these questions is to fly a reconnaissance mission that uses a multi-mode radar in a near-circular, low-altitude orbit of ?400 km and 60-70° inclination. This type of mission profile results in a total mission delta-V of ?4.4 km/s. Aerobraking could provide a significant portion, potentially up to half, of this energy transfer, thereby permitting more mass to be allocated to the spacecraft and science payload or facilitating the use of smaller, cheaper launch vehicles.Aerobraking at Venus also provides additional science benefits through the measurement of upper atmospheric density (recovered from accelerometer data) and temperature values, especially near the terminator where temperature changes are abrupt and constant pressure levels drop dramatically in altitude from day to night.Scientifically rich, Venus is also an ideal location for implementing aerobraking techniques. Its thick lower atmosphere and slow planet rotation result in relatively more predictable atmospheric densities than Mars. The upper atmosphere (aerobraking altitudes) of Venus has a density variation of 8% compared to Mars' 30% variability. In general, most aerobraking missions try to minimize the duration of the aerobraking phase to keep costs down. These short phases have limited margin to account for contingencies. It is the stable and predictive nature of Venus' atmosphere that provides safer aerobraking opportunities.The nature of aerobraking at Venus provides ideal opportunities to demonstrate aerobraking enhancements and techniques yet to be used at Mars, such as flying a temperature corridor (versus a heat-rate corridor) and using a thermal-response surface algorithm and autonomous aerobraking, shifting many daily ground activities to onboard the spacecraft. A defined aerobraking temperature corridor, based on spacecraft component maximum temperatures, can be employed on a spacecraft specifically designed for aerobraking, and will predict subsequent aerobraking orbits and prescribe apoapsis propulsive maneuvers to maintain the spacecraft within its specified temperature limits. A spacecraft specifically designed for aerobraking in the Venus environment can provide a cost-effective platform for achieving these expanded science and technology goals.This paper discusses the scientific merits of a low-altitude, near-circular orbit at Venus, highlights the differences in aerobraking at Venus versus Mars, and presents design data using a flight system specifically designed for an aerobraking mission at Venus. Using aerobraking to achieve a low altitude orbit at Venus may pave the way for various technology demonstrations, such as autonomous aerobraking techniques and/or new science measurements like a multi-mode, synthetic aperture radar capable of altimetry and radiometry with performance that is significantly more capable than Magellan.

Hibbard, Kenneth; Glaze, Lori; Prince, Jill

2012-04-01

32

The OH Venus nightglow spectrum: intensity and vibrational composition from VIRTIS-Venus Express observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Limb spectra of the OH nightglow emission corresponding to the ?v=1 and ?v=2 sequences have been collected with the VIRTIS infrared imaging spectrograph on board Venus Express between April 2006 and October 2008. A detailed statistical analysis shows that the peak intensity and altitude of the two vibrational sequences are significantly correlated, with a mean intensity ratio of the two sequences of 0.38±0.37. The altitude of the maximum of the ?v=2 emission is located ~1 km lower than...

Soret, Lauriane; Ge?rard, Jean-claude; Piccioni, Giuseppe; Drossart, Pierre

2012-01-01

33

First Results from Venus Express Aerobraking Campaign  

Science.gov (United States)

After a very successful mission orbiting Venus for more than 8 years, slowly the fuel is running out and the spacecraft will inevitably end up in the hot and acid atmosphere of the planet. Before this will happen we are taking the opportunity to dip down to around 130 km in a controlled manner in order to make detailed in situ investigations of this for remote sensing instruments difficult to access region. The spacecraft will use an aerobraking technique which maximizes the atmospheric drag by placing the solar panels perpendicular to the flight direction and will benefit from the inherent dynamically stable configuration this will provide. The on board accelerometers will give a direct measurement of the deceleration which in turn is directly proportional to the local atmospheric density. This will provide an excellent way to study both the total density profile and small scale density variations in the region of the pericentre. At the time of this campaign the pericentre will be located near the terminator at about 75 degrees Northern latitude. Aerobraking is a very efficient method of reducing the pericentre velocity and thereby reducing the apocentre altitude and the orbital period. Using this technique missions otherwise not feasible due to mass and fuel constraints can be enabled. This will be the first time an ESA spacecraft will be used for aerobraking and therefore it is run on an experimental basis as only limited resources are available. The so called “walk-in” phase will start at 190 km altitude on 17 May and the campaign ends on 11 July. Depending on the atmospheric densities encountered the orbital period may be reduced with up to 30 minutes. This presentation will report on the initial findings from this aerobraking campaign.

Svedhem, Håkan

34

Analysis of Venus Express optical extinction due to aerosols in the upper haze of Venus  

Science.gov (United States)

Observations by the SPICAV/SOIR instruments aboard Venus Express (VEx) have revealed that the Upper Haze of Venus is populated by two particle modes, as reported by Wilquet et al. (J. Geophys. Res., 114, E00B42, 2009; Icarus 217, 2012). Gao et al. (In press, Icarus, 2013) posit that the large mode is made up of cloud particles that have diffused upwards from the cloud deck below, while the smaller mode is generated by the in situ nucleation of meteoric dust. They tested this hypothesis by using version 3.0 of the Community Aerosol and Radiation Model for Atmospheres, first developed by Turco et al. (J. Atmos. Sci., 36, 699-717, 1979) and upgraded to version 3.0 by Bardeen et al. (The CARMA 3.0 microphysics package in CESM, Whole Atmosphere Working Group Meeting, 2011). Using the meteoric dust production profile of Kalashnikova et al. (Geophys. Res. Lett., 27, 3293-3296, 2000), the sulfur/sulfate condensation nuclei production profile of Imamura and Hashimoto (J. Atmos. Sci., 58, 3597-3612, 2001), and sulfuric acid vapor production profile of Zhang et al. (Icarus, 217, 714-739, 2012), they numerically simulate a column of the Venus atmosphere from 40 to 100 km above the surface. Their aerosol number density results agree well with Pioneer Venus Orbiter (PVO) data from Knollenberg and Hunten (J. Geophys. Res., 85, 8039-8058, 1980), while their gas distribution results match that of Kolodner and Steffes below 55 km (Icarus, 132, 151-169, 1998). The resulting size distribution of cloud particles shows two distinct modes, qualitatively matching the observations of PVO. They also observe a third mode in their results with a size of a few microns at 48 km altitude, which appears to support the existence of the controversial third mode in the PVO data. This mode disappears if coagulation is not included in the simulation. The Upper Haze size distribution shows two lognormal-like distributions overlapping each other, possibly indicating the presence of the two distinct modes. In this work, we significantly extend the analysis to include new SOIR (PSS, 2014 Submitted) and VeRa VEx temperature profiles (which are quite different from the PVO profiles) and discuss our new results in context of the recent VEx observations (Wilquet et al., Icarus 217, 2012) with an inter comparison with the PVO data. We will also discuss similarities and differences arising from the PVO and VEx epochs where they exist.

Parkinson, Christopher; Bougher, Stephen; Mahieux, Arnaud; Tellmann, Silvia; Pätzold, Martin; Vandaele, Ann C.; Wilquet, Valérie; Schulte, Rick; Yung, Yuk; Gao, Peter; Bardeen, Charles

35

Study and Implementation of the End-to-End Data Pipeline for the Virtis Imaging Spectrometer Onbaord Venus Express: "From Science Operations Planning to Data Archiving and Higher Lever Processing"  

Science.gov (United States)

This PhD Thesis describes the activities performed during the Research Program undertaken for two years at the Istituto Nazionale di AstroFisica in Rome, Italy, as active member of the VIRTIS Technical and Scientific Team, and one additional year at the European Space Astronomy Center in Madrid, Spain, as member of the Mars Express Science Ground Segment. This document will show a study of all sections of the Science Ground Segment of the Venus Express mission, from the planning of the scientific operations, to the generation, calibration and archiving of the science data, including the production of valuable high level products. We will present and discuss here the end-to-end diagram of the ground segment from the technical and scientific point of view, in order to describe the overall flow of information: from the original scientific requests of the principal investigator and interdisciplinary teams, up to the spacecraft, and down again for the analysis of the measurements and interpretation of the scientific results. These scientific results drive to new and more elaborated scientific requests, which are used as feedback to the planning cycle, closing the circle. Special attention is given here to describe the implementation and development of the data pipeline for the VIRTIS instrument onboard Venus Express. During the research program, both the raw data generation pipeline and the data calibration pipeline were developed and automated in order to produce the final raw and calibrated data products from the input telemetry of the instrument. The final raw and calibrated products presented in this work are currently being used by the VIRTIS Science team for data analysis and are distributed to the whole scientific community via the Planetary Science Archive. More than 20,000 raw data files and 10,000 calibrated products have already been generated after almost 4 years of mission. In the final part of the Thesis, we will also present some high level data processing methods developed for the Mapping channel of the VIRTIS instrument. These methods have been implemented for the generation of high level global maps of measured radiance over the whole planet, which can then be used for the understanding of the global dynamics and morphology of the Venusian atmosphere. This method is currently being used to compare different emissions probing at different altitudes from the low cloud layers up to the upper mesosphere, by using the averaged projected values of radiance observed by the instrument, such as the near infrared windows at 1.7 ?m and 2.3?m, the thermal region at 3.8?m and 5?m plus the analysis of particular emissions in the night and day side of the planet. This research has been undertaken under guidance and supervision of Giuseppe Piccioni, VIRTIS co-Principal Investigator, with support of the entire VIRTIS technical and scientific team, in particular of the Archiving team in Paris (LESIA-Meudon). The work has also been done in close collaboration with the Science and Mission Operations Centres in Madrid and Darmstadt (European Space Agency), the EGSE software developer (Techno Systems), the manufacturer of the VIRTIS instrument (Galileo Avionica) and the developer of the VIRTIS onboard software (DLR Berlin). The outcome of the technical and scientific work presented in this thesis is currently being used by the VIRTIS team to continue the investigations on the Venusian atmosphere and plan new scientific observations to improve the overall knowledge of the solar system. At the end of this document we show some of the many technical and scientific contributions, which have already been published in several international journals and conferences, and some articles of the European Space Agency used for public outreach.

Cardesín Moinelo, Alejandro

2010-04-01

36

Scattering particles in nightside limb observations of Venus’ upper atmosphere by Venus Express VIRTIS  

Science.gov (United States)

Nightside infrared limb spectra of the Venus upper atmosphere, obtained by Venus Express VIRTIS, show strong scattering of thermal radiation. This scattering of upward-going radiation into the line-of-sight is dominant below 82.5 km even at a wavelength of 5 ?m, which is indicative of relatively large particles. We show that 1 ?m-sized sulfuric acid particles (also known as mode 2 particles) provide a good fit to the VIRTIS limb data at high altitudes. We retrieve vertical profiles of the mode 2 number density between 75 and 90 km at two latitude ranges: 20-30°N and 47-50°N. Between 20 and 30°N, scattering by mode 2 particles is the main source of radiance for altitudes between 80 and 85 km. Above altitudes of 85 km smaller particles can also be used to fit the spectra. Between 47 and 50°N mode 2 number densities are generally lower than between 20 and 30°N and the profiles show more variability. This is consistent with the 47-50° latitude region being at the boundary between the low latitudes and high latitudes, with the latter showing lower cloud tops and higher ultraviolet brightness (Titov, D.V., Taylor, F.W., Svedhem, H., Ignatiev, N.I., Markiewicz, W.J., Piccioni, G., Drossart, P. [2008]. Nature 456, 620-623).

de Kok, R.; Irwin, P. G. J.; Tsang, C. C. C.; Piccioni, G.; Drossart, P.

2011-01-01

37

Oxygen nightglow investigation with VIRTIS/Venus-Express  

Science.gov (United States)

Venus-Express is orbiting around Venus since April 2006, and the VIRTIS instrument (Visible and Infrared Thermal Imaging Spectrometer) on board the spacecraft, is providing a large set of valuable data. In particular several spectral features in the spectral region between 1.0 and 1.6µm, have been detected during the night and attributed to molecular oxygen airglow. The most intense feature has been observed at 1.27 µm and has been identified as the widely studied (0,0) band of the (a1?g -X3?-g) oxygen transition. A weaker oxygen emission, peaking at 1.58µm and due to the (0,1) band of the same electronic transition has also been investigated with the help of VIRTIS observations and reported in recent papers. The spectral region between 1.2 and 1.4µm is not fully satisfactorly explained considering the (0,0) band of the (a1?g -X3?-g) oxygen transition alone. This would suggest that other emitting species could be the cause of the mismatch between the available data and what is observed in the Venus atmosphere by VIRTIS. In the present work, we propose to improve the fit of the spectral region around the (0,0) (a1?g -X3?-g) oxygen emission near 1.27µm, by adding other transitions and modifying physical parameters like the rotational temperature. We find that the inclusion of the (1,1) band contributes to significantly improve the fit over the 1.27-1.28µm spectral range. Moreover, we discuss the detection of a not yet identified emission at 1.06µm, which we attribute to the (1,0) transition of oxygen, which supports further more the emission of the (1,1) reported in the previous point. The detection of these new emissions provide new hints to better investigate the upper mesosphere of Venus and to shed light on the chemistry and dynamics of our sister planet. Acknowledgment: We wish to thank ESA, ASI, CNES and the VIRTIS/Venus Express Team to have supported this research.

Migliorini, Alessandra; Piccioni, Giuseppe; Gerard, Jean-Claude; Stefani, Stefania; Snels, Marcel; Zasova, Ludmila; Drossart, Pierre

38

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

39

From Earth to Venus - reaching our sister planet  

Science.gov (United States)

On 9 November 2005, Venus Express left Earth and was placed in orbit around Venus on 11 April 2006. Only 48 hours later, the first astonishing images of the south pole were received on Earth. A few weaks later, after orbital manoeuvres, Venus Express achieved its operational science orbit ready to begin several years of observations.

Accomazzo, Andrea; Schmitz, Peter; Tanco, Ignacio

2006-08-01

40

Investigation of planetary space weather effects at Venus observed by the ASPERA-4 particle analyzer and the magnetometer flying onboard of Venus Express Mission  

Science.gov (United States)

In this study we identified several coronal mass-ejections (CME's) interacting with the induced magnetosphere of Venus during 2010 and 2011 using STEREO observations and ENLIL simulations. Our purpose is to analyze the response of the induced magnetosphere and the ionosphere to these extreme conditions based on measurements made by the ASPERA-4 and MAG instruments on Venus Express. The parameters of the interplanetary magnetic field (IMF) during these solar events are also discussed. Previously we investigated the effects of the May 2007 solar eruption on the induced magnetosphere of Venus in a poster publication (EPSC2013-266). During the analyzed solar event large scale rotation of the interplanetary magnetic field was observed and in the polar region, the altitude where planetary ions were present decreased compared to the average cases. Polarity reversal of the induced magnetosphere also took place, similar to the cases discussed by Edberg et. al (2011). Several CME's interacted with Venus in November 2011. One of the largest lifted off on 3rd November and reached Venus on 5th November. The solar wind parameters showed large variations: the velocity peaked over 900 km/s, and the magnitude of the IMF suddenly increased threefold. The magnetic field reached 240 nT inside the induced magnetosphere, which is extremely high compared to normal conditions. The heavy ion density measured by VEX peaked over 1000 1/cm3 providing clear evidence for ionosphere crossing. Due to the orbit parameters it is possible to investigate the magnetic structure in the tail. The other selected solar eruptions caused similar changes including the sudden increase in the solar wind velocity and magnitude of the magnetic field in the magnetic barrier but due to the different orbital parameters other regions of the induced magnetosphere were investigated as well. In conclusion the observed planetary space weather effects include that in the shocked solar wind we observed Increased velocity, ion density and thermal pressure. As a consequence of those, the ion outflow flux increased at the ion composition boundary; a stronger than usual magnetic barrier was observed. In the tail the magnetic field structure was modified and higher than usual ion outflow was indicated but these require further study. References: Edberg, N. J. T., et al. (2011), Atmospheric erosion of Venus during stormy space weather, J. Geophys. Res., 116, A09308, doi:10.1029/2011JA016749. Vech et. al (2013), The effects of the May 2007 solar eruption on the induced magnetosphere of Venus, European Planetary Science Congress 2013, London, EPSC2013-266

Vech, Daniel; Szego, Karoly; Opitz, Andrea; Fraenz, Markus

2014-05-01

 
 
 
 
41

Water abundance and hydrogen isotopic ratio in the upper atmosphere of Venus from SOIR measurements on board Venus Express  

Science.gov (United States)

Water on Venus is much more scarce than on Earth, with volume mixing ratios lower than a part per million. The reason for this has always been of great interest, because it may give clues to the difference of evolution between the two planets. Studying water gives also access to another important planetary parameter, which is the deuterium to hydrogen isotopic ratio. H _{2}O and HDO are measured together with CO _{2} in the SOIR wavelength range, in the region 2.5 to 2.6 ?m (3800 to 4000 cm ^{-1}) for H _{2}O and 3.35 to 3.85 ?m (2600 to 3000 cm ^{-1}) for HDO, which allows the derivation of their vertical density profiles together with the temperature and total density profiles obtained from CO2 measurements [1], which can be used to calculate 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 1000 m and 2500 m). The maximum extent of the H _{2}O and the HDO profiles is from 120 to 70 km, with variations from orbit to orbit. We will present results from the simultaneous measurements of H _{2}O and HDO that occur during the first 5 occultation seasons of Venus Express, i.e. from 04/09/2006 to 22/08/2007. 1. Mahieux, A., A.C. Vandaele, S. Robert, V. Wilquet, R. Drummond, F. Montmessin, and J.L. Bertaux, Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express. Carbon dioxide measurements at the Venus terminator. J. Geophys. Res., (submitted) (2012)

Drummond, Rachel; Mahieux, Arnaud; Wilquet, Valerie; Bertaux, Jean-Loup; Robert, Severine; Vandaele, Ann C.; Matsui, Hiroki; Iwagami, Naomoto

2012-07-01

42

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

43

The variable upper atmosphere of Venus, as determined by data from drag and torque measurements by Venus Express  

Science.gov (United States)

Until recently the only information on the structure of the polar upper atmosphere of Venus available has been based on the reference atmosphere models such as the VTS3 or VIRA models. These models extrapolate the values from low latitudes to high latitudes by using equivalent solar zenith angles. New measurements by Venus Express show that such extrapolations not always give correct results and that there is a permanent overestimate of the density at high latitudes. These new results have been reached by using two different but related techniques, both using an atmospheric drag effect on the spacecraft. By reducing the pericentre altitude the total mass density in the altitude range 150-200km can be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the telecommunication link. Such measurements have been performed with Venus Express several times during the last years as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericenter pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric attitude with respect to the center of gravity, center of drag and the velocity vector. This technique has proven very sensitive, in particular if the geometric asymmetry is large, and offers an additional method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. Between 2009 and 2012 several campaigns, with altitudes going as low as 165 km, were held. The highest density measured was 7.7 10-12kg/m3 which is significantly less than earlier models predict. The results largely confirm the density measurements by the VExADE drag measurements and add to the confidence in the results from these measurements. By using these drag and torque results and assuming a hydrostatic diffusive equilibrium atmosphere a new model has been constructed. The model is fitted to the Venus Express remote sensing measurements in the upper mesosphere (VeRa radio occultation data) and lower thermosphere (SpicaV/SOIR data) to give a continuous transition across the different regions.

Svedhem, Håkan; Müller-Wodarg, Ingo; Rosenblatt, Pascal

2013-04-01

44

Probing Venus' polar upper atmosphere in situ: Preliminary results of the Venus Express Atmospheric Drag Experiment (VExADE).  

Science.gov (United States)

On its highly elliptical 24 hour orbit around Venus, the Venus Express (VEx) spacecraft briefly reaches a pericenter altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008 (campaign1), October 2009 (cam-paign2), February and April 2010 (campaign3), for which the pericenter altitude was lowered to about 175 km in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in-situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the pericenter pass, allowing us to infer total atmospheric mass density at the pericenter altitude. The GINS software (Géodésie par Intégration Numérique e e Simultanées) is used to accurately reconstruct the orbital motion of VEx through an iterative least-squares fitting process to the Doppler tracking data. The drag acceleration is modelled using an initial atmospheric density model (VTS model, A. Hedin). A drag scale factor is estimated for each pericenter pass, which scales Hedin's density model in order to best fit the radio tracking data. About 20 density scale factors have been obtained mainly from the second and third VExADE campaigns, which indicate a lower density by a factor of about one-third than Hedin's model predicts. These first ever polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus' thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements. The preliminary results of the VExADE cam-paigns show that it is possible to obtain reliable estimates of Venus' upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from the planned further lowering of VEx pericenter altitude to below 170 Km.

Rosenblatt, Pascal; Bruinsma, Sean; Mueller-Wodarg, Ingo; Haeusler, Bernd

45

Water vapor abundance near the surface of Venus from Venus Express/VIRTIS observations  

Science.gov (United States)

Nightside observations of the 1.18-?m atmospheric window by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard the Venus Express spacecraft were analyzed to measure and map the water vapor abundance in the lower atmosphere. Thermal emission in this window originates partly from the surface and partly from the first scale height (0-15 km) of the atmosphere. Constraints on the CO2 continuum absorption, which is the dominant source of gaseous opacity in the window, were obtained from the variation of the 1.185-?m intensity with surface elevation. An absorption coefficient of 1 ± 0.4 × 10-9 cm-1 amagat-2 best fits the observed variation. We retrieved a water vapor mole fraction of 44 ± 9 ppm from various selections of VIRTIS spectra in the southern hemisphere, in agreement with previous analyses of the nightside emission. This value is somewhat larger than that previously determined at higher altitudes from the 2.3- and 1.74-?m nightside windows, but the error bars still allow a constant with height H2O mole fraction from the surface up to 40 km. Using the intensity ratio in the two wings of the 1.18-?m window as a proxy, we searched for horizontal variations of the H2O abundance in various VIRTIS observational sequences. We derived stringent upper limits for any possible latitudinal variations on the night side: ±1.5% in the range 60°S-25°N and ±3% for the broader range 80°S-25°N. The lack of detectable latitudinal variations is consistent with a constant with height water profile in the lower atmosphere and probably precludes any strong concentration gradient near the surface.

Bézard, Bruno; Tsang, Constantine C. C.; Carlson, Robert W.; Piccioni, Giuseppe; Marcq, Emmanuel; Drossart, Pierre

2009-05-01

46

Exploring Venus: the Venus Exploration Analysis Group (VEXAG)  

Science.gov (United States)

In July 2005 NASA s Planetary Division established the Venus Exploration Analysis Group VEXAG http www lpi usra edu vexag in order to engage the scientific community at large in identifying scientific priorities and strategies for the exploration of Venus VEXAG is a community-based forum open to all interested in the exploration of Venus VEXAG was designed to provide scientific input and technology development plans for planning and prioritizing the study of Venus over the next several decades including a Venus surface sample return VEXAG regularly evaluates NASA s Venus exploration goals scientific objectives investigations and critical measurement requirements including the recommendations in the National Research Council Decadal Survey and NASA s Solar System Exploration Strategic Roadmap VEXAG will take into consideration the latest scientific results from ESA s Venus Express mission and the MESSENGER flybys as well as the results anticipated from JAXA s Venus Climate Orbiter together with science community inputs from venues such as the February 13-16 2006 AGU Chapman Conference to identify the scientific priorities and strategies for future NASA Venus exploration VEXAG is composed of two co-chairs Sushil Atreya University of Michigan Ann Arbor and Janet Luhmann University of California Berkeley VEXAG has formed three focus groups in the areas of 1 Planetary Formation and Evolution Surface and Interior Volcanism Geodynamics etc Focus Group Lead Steve Mackwell LPI 2 Atmospheric Evolution Dynamics Meteorology

Ocampo, A.; Atreya, S.; Thompson, T.; Luhmann, J.; Mackwell, S.; Baines, K.; Cutts, J.; Robinson, J.; Saunders, S.

47

Composition of the upper Venus atmosphere using SPICAV-SOIR on board Venus Express  

Science.gov (United States)

The wavelength range probed by SOIR/VEX allows a detailed chemical inventory of the Venus atmosphere. Several trace gases, such as H2O/HDO, HF, HCl, CO, or SO2, are observed together with CO2, leading to the derivation of their vertical density profiles. Temperature and total density profiles are deduced from the CO2 density profiles and VMR are obtained for all trace gases. The measurements all occur at the Venus terminator, morning and evening sides, covering all latitudes from the North Pole to the South Pole. The vertical resolution is between 100 and 500 m in the Northern hemisphere, and is poorer at southern latitudes (between 1 and 2.5 km). The typical vertical extent of the profiles ranges from 70 to 120 km (for CO2: from 70 to 170 km), encompassing thus the mesosphere and the lower thermosphere of the planet. The Venus atmospheric region probed by SOIR is very special as it acts as a transition region between two distinct dynamic regimes characterized by different flow patterns: the zonal retrograde flow below 70 km and the subsolar to antisolar circulation above 100 km. Some of the detected trace gases play important roles in the chemistry of the atmosphere. The study of CO, which is mainly produced through photodissociation of CO2 at high altitudes by solar ultraviolet radiation, can lead to significant information on the dynamics in this region. Investigation of trace gases leads to a better understanding of the processes occurring in the upper atmosphere of Venus.

Vandaele, A. C.; Mahieux, A.; Robert, S.; Wilquet, V.; Drummond, R.; Bertaux, J.-L.

2013-09-01

48

Electrophysiological characteristics of inhibitory neurons of the prepositus hypoglossi nucleus as analyzed in Venus-expressing transgenic rats.  

Science.gov (United States)

The identification and characterization of excitatory and inhibitory neurons are significant steps in understanding neural network functions. In this study, we investigated the intrinsic electrophysiological properties of neurons in the prepositus hypoglossi nucleus (PHN), a brainstem structure that is involved in gaze holding, using whole-cell recordings in brainstem slices from vesicular GABA transporter (VGAT)-Venus transgenic rats, in which inhibitory neurons express the fluorescent protein Venus. To characterize the intrinsic properties of these neurons, we recorded afterhyperpolarization (AHP) profiles and firing patterns from Venus-expressing [Venus?] and Venus-non-expressing [Venus?] PHN neurons. Although both types of neurons showed a wide variety of AHP profiles and firing patterns, oscillatory firing was specific to Venus? neurons, while a firing pattern showing only a few spikes was specific to Venus? neurons. In addition, AHPs without a slow component and delayed spike generation were preferentially displayed by Venus? neurons, whereas a firing pattern with constant interspike intervals was preferentially displayed by Venus? neurons. We evaluated the mRNAs expression of glutamate decarboxylase (GAD65, GAD67) and glycine transporter 2 (GlyT2) to determine whether the recorded Venus? neurons were GABAergic or glycinergic. Of the 67 Venus? neurons tested, GlyT2 expression alone was detected in only one neuron. Approximately 40% (28/67) expressed GAD65 and/or GAD67 (GABAergic neuron), and the remainder (38/67) expressed both GAD(s) and GlyT2 (GABA&GLY neuron). These results suggest that most inhibitory PHN neurons use either GABA or both GABA and glycine as neurotransmitters. Although the overall distribution of firing patterns in GABAergic neurons was similar to that of GABA&GLY neurons, only GABA&GLY neurons exhibited a firing pattern with a long first interspike interval. These differential electrophysiological properties will be useful for the identification of specific types of PHN neurons. PMID:21952130

Shino, M; Kaneko, R; Yanagawa, Y; Kawaguchi, Y; Saito, Y

2011-12-01

49

Venus OH nightglow distribution based on VIRTIS limb observations from Venus Express  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The full set of VIRTIS?M limb observations of the OH Venus nightglow has been analyzed to determine its characteristics. Based on 3328 limb profiles, we find that the mean peak intensity along the line of sight of the OH(deltaV = 1 sequence) is 0.35 MR and is located at 96.4 ± 5 km. The emission is highly variable and no dependence of the airglow layer altitude versus the antisolar angle is observed. The peak brightness appears to decrease away from the antisolar point even if the varia...

Soret, Lauriane; Ge?rard, Jean-claude; Piccioni, Giuseppe; Drossart, Pierre

2010-01-01

50

Cloud-top altitude from limb views acquired by the Venus Monitoring Camera (VMC) on Venus Express  

Science.gov (United States)

A good knowledge of the effective cloud top altitude is essential for interpretation of cloud motions measured from Venus images taken in reflected sunlight at different wavelengths. Ignatiev et al. (2009) reported the first inferences of the cloud top altitude from nadir observations acquired by the Visible Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express using the depth of the 1.6µ CO2 continuum. Their results indicate that the cloud tops are 74 ± 1 km above the mean surface in low and mid-latitudes and at only 63-69 km in polar latitudes. The nominal cloud top altitude used in most previous analyses of imaging data are generally either 6115 and 6120 km radius, or 62.8 and 67.8 km respectively above the mean surface. The Level 3 map products generated from the VMC data use a cloud altitude of 65 km for all filters. Given the large number of images acquired from the VMC since the insertion of Venus Express in orbit in April 2006, it is now possible to measure the altitude of the visible cloud top (slant optical depth, ?slant = 1) from the images. Preliminary results were presented by Limaye et al. (2011) by determination of the ?slant location in the VMC images and using the observing geometry information to determine the altitude by first determining the image center very precisely. We used star field images from recent orbits to re-assess the pixel size. Results from the four filters of VMC (365, 513, 965 and 1010 nm central wavelengths) provide an improved value for the visible cloud top altitude using the improved values for the image scale of the four VMC cameras.

Limaye, S. S.; Krauss, R. J.; Ignatiev, N.; Markiewicz, W. J.,

2012-04-01

51

A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express.  

Science.gov (United States)

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120 km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft and ground-based observations of infrared emission from CO2, O2 and NO have established that photochemical and dynamic activity controls the structure of the upper atmosphere of Venus. These data, however, have left unresolved the precise altitude of the emission owing to a lack of data and of an adequate observing geometry. Here we report measurements of day-side CO2 non-local thermodynamic equilibrium emission at 4.3 microm, extending from 90 to 120 km altitude, and of night-side O2 emission extending from 95 to 100 km. The CO2 emission peak occurs at approximately 115 km and varies with solar zenith angle over a range of approximately 10 km. This confirms previous modelling, and permits the beginning of a systematic study of the variability of the emission. The O2 peak emission happens at 96 km +/- 1 km, which is consistent with three-body recombination of oxygen atoms transported from the day side by a global thermospheric sub-solar to anti-solar circulation, as previously predicted. PMID:18046396

Drossart, P; Piccioni, G; Gérard, J C; Lopez-Valverde, M A; Sanchez-Lavega, A; Zasova, L; Hueso, R; Taylor, F W; Bézard, B; Adriani, A; Angrilli, F; Arnold, G; Baines, K H; Bellucci, G; Benkhoff, J; Bibring, J P; Blanco, A; Blecka, M I; Carlson, R W; Coradini, A; Di Lellis, A; Encrenaz, T; Erard, S; Fonti, S; Formisano, V; Fouchet, T; Garcia, R; Haus, R; Helbert, J; Ignatiev, N I; Irwin, P; Langevin, Y; Lebonnois, S; Luz, D; Marinangeli, L; Orofino, V; Rodin, A V; Roos-Serote, M C; Saggin, B; Stam, D M; Titov, D; Visconti, G; Zambelli, M; Tsang, C; Ammannito, Eleonora; Barbis, Alessandra; Berlin, Rainer; Bettanini, Carlo; Boccaccini, Angelo; Bonnello, Guillaume; Bouyé, Marc; Capaccioni, Fabrizio; Cardesin, Alejandro; Carraro, Francesco; Cherubini, Giovanni; Cosi, Massimo; Dami, Michele; De Nino, Maurizio; Del Vento, Davide; Di Giampietro, Marco; Donati, Alessandro; Dupuis, Olivier; Espinasse, Sylvie; Fabbri, Anna; Fave, Agnès; Veltroni, Iacopo Ficai; Filacchione, Gianrico; Garceran, Katia; Ghomchi, Yamina; Giustizi, Maurizio; Gondet, Brigitte; Hello, Yann; Henry, Florence; Hofer, Stefan; Huntzinger, Gerard; Kachlicki, Juergen; Knoll, René; Kouach, Driss; Mazzoni, Alessandro; Melchiorri, Riccardo; Mondello, Giuseppe; Monti, Francesco; Neumann, Christian; Nuccilli, Fabrizio; Parisot, Jérôme; Pasqui, Claudio; Perferi, Stefano; Peter, Gisbert; Piacentino, Alain; Pompei, Carlo; Réess, Jean-Michel; Rivet, Jean-Pierre; Romano, Antonio; Russ, Natalie; Santoni, Massimo; Scarpelli, Adelmo; Sémery, Alain; Soufflot, Alain; Stefanovitch, Douchane; Suetta, Enrico; Tarchi, Fabio; Tonetti, Nazzareno; Tosi, Federico; Ulmer, Bernd

2007-11-29

52

Tracking of Mars Express and Venus Express spacecraft with VLBI radio telescopes  

Science.gov (United States)

The ESA Mars Express and Venus Express spacecraft (S/C) have been observed for the last two years with the European VLBI radio telescopes of Metsähovi (FI), Wettzell (GE), Yebes (SP), Medicina, Matera, Noto (IT), Puschino (RU) and Onsala (SW). The campaign is in the framework of the assessment study and preparation of the European VLBI Network to the upcoming ESA and other deep space missions. It also offers new opportunities for applications of radio astronomy techniques to planetary science, geophysics and geodesy. Observations are carried out either in single- or multi-dish modes when S/C is locked to the ESA’s ESTRACK ground stations (Cebreros or New Nortia) observing the two way link. Data are recorded locally at the stations using standard VLBI equipment and transferred to the Metsähovi for processing. Further on, the data are transferred from Metsähovi to Joint Institute for VLBI in Europe for further post-analysis. High dynamic range of the S/C signal detections allowed us to determine the apparent topocentric frequency of the S/C carrier line and accompanying ranging tones down to milli-Hz spectral accuracy and to extract the phase of the S/C signal carrier line. With multi-station observations, the respective phases can be calibrated on the per-baseline basis using VLBI phase referencing technique and observations of background quasars close to S/C in their celestial position using far-field VLBI delay model for quasars and near-field model for S/C. The post-analysis of the S/C tracking data enables us to study several parameters of the S/C signals. Of these, the phase fluctuations of the signal can be used for characterization of the interplanetary plasma density fluctuations along the signal propagation line at different spatial and temporal scales and different solar elongations. These fluctuations are well represented by a near-Kolmogorov spectrum. Multi-station observations can distinguish the contributions of propagation effects in the plasma along the up- and down-link paths as seen from different VLBI stations through different Fresnel channels. We also demonstrated high accuracy S/C Doppler tracking with 3 EVN stations (Metsähovi, Wettzell and Yebes) during the MEX-Phobos flyby, which occurred on 2010 march 03. These multi-station observing sessions could help to better determine the Phobos gravity field and together with phase referencing provide additional geometrical constrains on the orbiter/Phobos trajectories. VEX S/C signal detection with four VLBI antennae (23/08/2010).

Molera Calvés, G.; Pogrebenko, S. V.; Wagner, J.; Cimò, G.; Gurvits, L.; Duev, D.

2010-12-01

53

Photochemical Control of the Distribution of Venusian Water and Comparison to Venus Express SOIR Observations  

Science.gov (United States)

We use the JPL/Caltech 1-D KINETICS photochemical model to solve the continuity diffusion equation for the atmospheric constituent abundances and total number density as a function of radial distance from the planet Venus. The photochemistry of the Venus atmosphere from 58 to 112 km is modeled using an updated and expanded chemical scheme (Zhang et al., 2010; 2012), guided by the results of recent observations. We mainly follow Zhang et al. (2010; 2012) to guide our choice of boundary conditions for 40 species. We fit the SOIR Venus Express results of 1 ppm at 70-90 km (Bertaux et al (2007) by modeling water from between 10 – 35 ppm at our 58 km lower boundary and using an SO2 mixing ratio of 25 ppm as our nominal reference value. We then vary the SO2 mixing ratio at the lower boundary between 5 and 75 ppm and find that it can control the water distribution at higher altitudes.

Parkinson, Chris; Yung, Yuk; Esposito, Larry; Gao, Peter; Bougher, Steve

2014-11-01

54

Science News or Astrological Debating: Chinese Records of the Transit of Venus of 1874  

Science.gov (United States)

The Venus transit is very important in the measuring of the distance between the sun and the earth. It ever occurred in 1874, but this time it was visible only in China and some other places in eastern sphere. So many astronomers of the western countries had to come to China to observe it. In traditional Chinese astrological explanation, the sun represented the emperor. If the sun were invaded by other stars, it means that the emperor and the country would have some ominous disasters. In late 19th century, western astronomical knowledge was widely translated into Chinese and understood by Chinese intellectuals. The Venus transit should easily be understood by Chinese intellectuals as one kind of astronomical phenomena. But early before the Venus transit taking place in 1874, many Chinese publications had to introduce this kind of celestial phenomena as science news because at same time, some influential news papers and journals also had some discussion on what astrological connection between the Venus transit of this time and the fortune of the country. This article collects these interesting Chinese records and discusses what different attitude to the Venus transit by Chinese intellectuals and officials during that period in which western learning was widely disseminated in China.

Lu, Lingfeng

2012-09-01

55

The 2004 Transit of Venus as a Space Science Education Opportunity  

Science.gov (United States)

We will present some of the programs and activities that NASA and its missions are preparing in order to support public and K12 education in space science and astronomy using the 2004 transit of Venus as a focal event. The upcoming transit of Venus on June 8 offers a unique opportunity to educate students and the general public about the scale of the solar system and the universe, as well as basic issues in comparative planetology. NASA's Sun-Earth Connection Education Forum is offering a number of programs to take advantage of this rare event. Among these are a live web cast from Spain of the entire transit, a series of radio and TV programs directed at students and the general public, a web cast describing extra-solar planet searches using the transit geometry, and archived observations produced by public observatories and student-operated solar viewers. The NASA/OSS Education Forums will also partner with science museums, planetaria and teachers across the country to bring the transit of Venus 'down to Earth'. In addition to offering enrichment activities in mathematics and space science, we also describe collaborations that have yielded unique historical resources including online archives of newspaper articles from the 1874 and 1882 transits. In addition, in collaboration with the Library of Congress Music Division, we have supported a modern re-orchestration of John Philip Sousa's Transit of Venus March which has not been performed since 1883. We anticipate that the transit of Venus will be a significant event of considerable public interest and curiosity, if the newspaper headlines from the transit seen in 1882 are any indication.

Odenwald, S.; Mayo, L.; Vondrak, R.; Thieman, J.; Hawkins, I.; Schultz, G.

2003-12-01

56

Time-series analysis of temperature profiles from VIRTIS Venus Express data  

Science.gov (United States)

Nighttime infrared observations of the VIRTIS instrument on board Venus Express have already demonstrated their potential in the study of air temperature fields of the Venusian mesosphere. The entire available dataset acquired by the VIRTIS-M IR channel was processed at moderate spatial resolution (i.e. averaging pixels in 8x8 boxes) to derive an unprecedented dataset of air temperature profiles in the pressure range 100-0.1 mbar, covering mostly the latitudes south of 45S. We presented in Grassi et al. (2010, doi:10.1029/2009JE003553) an analysis of the mean properties of temperature profiles, once binned in the latitude/local time/pressure space. Here we discuss the preliminary findings of time-series analysis of data from individual bins. Despite the sparsity of most series, Lomb-Scargle periodogram can be effectively applied in the regions south of 70S, where better coverage is made possible by specific properties of Venus Express orbit. Here the algorithm is able to extract a clear signature related to a period of about 115-120 Earth days, i.e. one Venus solar day, particularly strong at the level around 10 mbar. Further analysis of average temperature fields in the latitude - longitude space demonstrated, for different local times during night, that air temperatures east of Lada Terra (most specifically in a region centered around 130°E and about 60° wide) are about 10K warmer than in other longitudes at 75S.

Grassi, D.; Migliorini, A.; Politi, R.; Montabone, L.; Piccioni, G.; Drossart, P.

2012-04-01

57

Venus Exploration opportunities within NASA's Solar System Exploration roadmap  

Science.gov (United States)

Science goals to understand the origin, history and environment of Venus have been driving international space exploration missions for over 40 years. Past missions include the Magellan and Pioneer-Venus missions by the US; the Venera program by the USSR; and the Vega missions through international cooperation. Furthermore, the US National Research Council (NRC), in the 2003 Solar System Exploration (SSE) Decadal Survey, identified Venus as a high priority target, thus demonstrating a continuing interest in Earth's sister planet. In response to the NRC recommendation, the 2005 NASA SSE Roadmap included a number of potential Venus missions arching through all mission classes from small Discovery, to medium New Frontiers and to large Flagship class missions. While missions in all of these classes could be designed as orbiters with remote sensing capabilities, the desire for scientific advancements beyond our current knowledge - including what we expect to learn from the ongoing ESA Venus Express mission - point to in-situ exploration of Venus.

Balint, Tibor; Thompson, Thomas; Cutts, James; Robinson, James

2006-01-01

58

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

International Nuclear Information System (INIS)

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, Japaships with initiatives in the EU, US, Japan, Taiwan and China.

59

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

60

Return to Venus of AKATSUKI, the Japanese Venus Orbiter  

Science.gov (United States)

Japanese Venus Climate Orbiter 'AKATSUKI' (PLANET-C) was proposed in 2001 with strong support by international Venus science community and approved as an ISAS mission soon after the proposal. AKATSUKI and ESA's Venus Express complement each other in Venus climate study. Various coordinated observations using the two spacecraft have been planned. Also participating scientists from US have been selected. Its science target is to understand the climate of Venus. The mission life we expected was more than 2 Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' expansion was confirmed. AKATSUKI was put into the 3-axis stabilized mode in the initial operation from Uchinoura station and the critical operation was finished at 20:00JST on the same day. The malfunction, which happened during the Venus Orbit Insertion (VOI) on7 Dec, 2010 is as follows. We set all commands on Dec. 5. Attitude control for Venus orbit insertion (VOI) was automatically done on Dec. 6. Orbital maneuver engine (OME) was fired 08:49 JST on Dec. 7. 1min. after firing the spacecraft went into the occultation region and we had no telemetry, but we expected to continuous firing for 12min. Recording on the spacecraft told us later that, unfortunately the firing continued just 152sec. and stopped. The reason of the malfunction of the OME was the blocking of check valve of the gas pressure line to push the fuel to the engine. We failed to make the spacecraft the Venus orbiter, and it is rotating the sun with the orbital period of 203 days. As the Venus orbit the sun with the period of 225 days, AKATSUKI has a chance to meet Venus again in 5 or 6 years depending on the orbit correction plan. Let us summarize the present situation of AKATSUKI. Most of the fuel still remains. But the condition of the propulsion system is unclear. ISAS is examining various scenarios of second Venus orbit insertion depending on the conditions of the check valve and the OME. Thermal condition during the extended cruise phase is severe. The solar flux (W/m2) to which the spacecraft is exposed from May 21, 2010 (Launch date) to the end of 2016. We expected about 2600W/m2 in the Venus orbit, but it is exposed to more than 3600W/m2 at perihelion (0.6AU from the sun). The temperatures of the instruments exposed to space gradually increased as the spacecraft approaching the perihelion. We tried to minimize the number of instruments whose temperatures exceed the allowed upper limits by letting a certain side of the spacecraft face to the sun. After passing the perihelion every instruments have been working normally. The degradation of the reflectivity of the outer film (MLI) during the extended cruise may influence the temperature tendency. Laboratory tests to evaluate the degradation are ongoing. We operate the test maneuver of the OME in September and hopefully the orbit maneuver in November, which leads the spacecraft close to Venus in 2015. We will report the result in the presentation.

Nakamura, M.; Iwagami, N.; Satoh, T.; Taguchi, M.; Watanabe, S.; Takahashi, Y.; Imamura, T.; Suzuki, M.; Ueno, M.; Yamazaki, A.; Fukuhara, T.; Yamada, M.; Ishii, N.; Ogohara, K.

2011-12-01

 
 
 
 
61

First ever in situ observations of Venus' polar upper atmosphere density using the tracking data of the Venus Express Atmospheric Drag Experiment (VExADE)  

Science.gov (United States)

On its highly elliptical 24 h orbit around Venus, the Venus Express (VEX) spacecraft briefly reaches a periapsis altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008, October 2009, February and April 2010, for which the periapsis altitude was lowered to the 186-176 km altitude range in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the periapsis pass, allowing us to infer total atmospheric mass density at the periapsis altitude. A Precise Orbit Determination (POD) of the VEX motion is performed through an iterative least-squares fitting process to the Doppler tracking data, acquired by the VEX radioscience experiment (VeRa). The drag acceleration is modelled using an initial atmospheric density model (VTS3 model, Hedin, A.E., Niemann, H.B., Kasprzak, W.T., Seiff, A. [1983]. J. Geophys. Res. 88, 73-83). A scale factor of the drag acceleration is estimated for each periapsis pass, which scales Hedin's density model in order to best fit the radio tracking data. Reliable density scale factors have been obtained for 10 passes mainly from the second (October 2009) and third (April 2010) VExADE campaigns, which indicate a lower density by a factor of about 1.8 than Hedin's model predicts. These first ever in situ polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus' thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements (Müller-Wodarg et al., in preparation). The preliminary results of the VExADE campaigns show that it is possible to obtain with the POD technique reliable estimates of Venus' upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from the planned further lowering of VEX pericenter altitude to below 170 km.

Rosenblatt, P.; Bruinsma, S. L.; Müller-Wodarg, I. C. F.; Häusler, B.; Svedhem, H.; Marty, J. C.

2012-02-01

62

Science to the public. VENUS TRANSIT 2004. Spain National Node. FINAL REPORT  

Science.gov (United States)

The Pamplona Planetarium hosted the Spain National Node for the international project named VT-2004, a whole compendium of activities of science popularisation based on the Venus Transit of June 8, 2004, including an on-line calculation of the Astronomical Unit using the transit observation method depicted by Edmond Halley in 17th Century. To achieve a wide knowledge of the activities, and to encourage citizens to participate in, several different networks (mainly using the Internet) were established that coordinated the participation of different institutions and individuals: planetariums and science centres; research institutions, observatories and universities; colleges and schools; amateur astronomer associations and groups; other cultural associations and the media. A wide range of activities were promoted throughout the nation, all of them having thus a common coordination centre. Acceptance from the society was achieved, with a wide coverage of media and great participation of people in all the activities.

Armentia, J.; Jáuregui, F.

63

Electron optical study of the Venus Express ASPERA-4 Electron Spectrometer (ELS) top-hat electrostatic analyser  

Science.gov (United States)

The performance of the Venus Express (VEX) ASPERA-4 Electron Spectrometer (ELS) is different from the nominal response shown by the ASPERA-3 ELS aboard Mars Express due to machining tolerance. Up to now, the precise mechanism for this was unknown and, therefore, the results of the experimental calibration could not be supported with a theoretical understanding of the fundamental instrument science behind the device. In this study, we show that the difference is due to a misalignment of the inner hemisphere and a widening of the entrance aperture of the instrument. The response of the VEX ELS can be approximated by a combination of a vertical offset of the inner hemisphere of ?0.6 mm and a lateral offset of less than 0.125 mm, combined with an aperture that is ?0.54 mm wider than nominal. The resulting K-factor, geometric factor, energy resolution and peak elevation are in good agreement with those observed experimentally. Therefore, we now have a good agreement between both laboratory calibration data and computer simulation, giving a firm foundation for future scientific data analysis.

Collinson, Glyn A.; Kataria, D. O.; Coates, Andrew J.; Tsang, Sharon M. E.; Arridge, Christopher S.; Lewis, Gethyn R.; Frahm, Rudy A.; Winningham, J. David; Barabash, Stas

2009-05-01

64

Electron optical study of the Venus Express ASPERA-4 Electron Spectrometer (ELS) top-hat electrostatic analyser  

International Nuclear Information System (INIS)

The performance of the Venus Express (VEX) ASPERA-4 Electron Spectrometer (ELS) is different from the nominal response shown by the ASPERA-3 ELS aboard Mars Express due to machining tolerance. Up to now, the precise mechanism for this was unknown and, therefore, the results of the experimental calibration could not be supported with a theoretical understanding of the fundamental instrument science behind the device. In this study, we show that the difference is due to a misalignment of the inner hemisphere and a widening of the entrance aperture of the instrument. The response of the VEX ELS can be approximated by a combination of a vertical offset of the inner hemisphere of ?0.6 mm and a lateral offset of less than 0.125 mm, combined with an aperture that is ?0.54 mm wider than nominal. The resulting K-factor, geometric factor, energy resolution and peak elevation are in good agreement with those observed experimentally. Therefore, we now have a good agreement between both laboratory calibration data and computer simulation, giving a firm foundation for future scientific data analysis

65

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

66

Missions to Venus  

Science.gov (United States)

Venus has always been a fascinating objective for planetary studies. At the beginning of the space era Venus became one of the first targets for spacecraft missions. Our neighbour in the solar system and, in size, the twin sister of Earth, Venus was expected to be very similar to our planet. However, the first phase of Venus spacecraft exploration in 1962-1992 by the family of Soviet Venera and Vega spacecraft and US Mariner, Pioneer Venus, and Magellan missions discovered an entirely different, exotic world hidden behind a curtain of dense clouds. These studies gave us a basic knowledge of the conditions on the planet, but generated many more questions concerning the atmospheric composition, chemistry, structure, dynamics, surface-atmosphere interactions, atmospheric and geological evolution, and the plasma environment. Despite all of this exploration by more than 20 spacecraft, the "morning star" still remains a mysterious world. But for more than a decade Venus has been a "forgotten" planet with no new missions featuring in the plans of the world space agencies. Now we are witnessing the revival of interest in this planet: the Venus Orbiter mission is approved in Japan, Venus Express - a European orbiter mission - has successfully passed the selection procedure in ESA, and several Venus Discovery proposals are knocking at the doors of NASA. The paper presents an exciting story of Venus spacecraft exploration, summarizes open scientific problems, and builds a bridge to the future missions.

Titov, D. V.; Baines, K. H.; Basilevsky, A. T.; Chassefiere, E.; Chin, G.; Crisp, D.; Esposito, L. W.; Lebreton, J.-P.; Lellouch, E.; Moroz, V. I.; Nagy, A. F.; Owen, T. C.; Oyama, K.-I.; Russell, C. T.; Taylor, F. W.; Young, R. E.

2002-10-01

67

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

68

Experiencing Venus: Clues to the origin, evolution, and chemistry of terrestrial planets via in-situ exploration of our sister world  

Science.gov (United States)

We review the current state of knowledge of (1) the origin and evolution of Venus and (2) the photochemical and thermochemical processes occurring in the middle and lower atmosphere there. For each, we review the promise of on-going and planned orbital observations by ESA's Venus Express and Japan's Venus Climate Orbiter missions. We review the need for future in-situ measurements for understanding Venus origin and evolution and present-day chemistry, and the implications for understanding the origin and history of the Earth and other bodies in the inner solar system, as well as for understanding terrestrial planets in other solar systems. We prioritize the goals remaining in the post Venus Express era, based on the Decadal Survey (National Research Council, 2003). Using past experience with Pioneer Venus, VEGAs, Veneras, and, most recently, Venus Express as guides, we suggest appropriate techniques and measurements to address these fundamental science issues.

Baines, Kevin H.; Atreya, Sushil K.; Carlson, Robert W.; Crisp, David; Grinspoon, David; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

69

Priorities for Venus Exploration  

Science.gov (United States)

Venus remains one of the most enigmatic bodies in our Solar System. Important questions remain regarding the origin and evolution of the atmosphere, the history of the surface and interior, and how the surface and atmosphere interact. In a broader context, understanding Venus has implications for understanding the evolution of terrestrial planets in our Solar System as well as for interpreting the growing set of observations of extra-solar planets. The Venus Exploration Analysis Group (VEXAG), established in 2005, is chartered by NASA's Planetary Science Division and reports its findings to the NASA Advisory Council. Open to all interested scientists, VEXAG regularly evaluates Venus exploration goals, scientific objectives, investigations and critical measurement requirements, including especially recommendations in the NRC Decadal Survey and the Solar System Exploration Strategic Roadmap. At the last general meeting in November 2012, VEXAG resolved to update the scientific priorities and strategies for Venus exploration. To achieve this goal, three major tasks were defined for 2013, (1) update the document prioritizing Goals, Objectives and Investigations for Venus Exploration, (2) develop a Roadmap for Venus exploration that is consistent with VEXAG priorities as well as Planetary Decadal Survey priorities, and (3) develop a white paper on technologies for Venus missions. Proposed versions of all three documents were presented at the VEXAG general meeting in November 2013. Here, we present the findings and final versions of all three documents for community comment and feedback. A follow-on Workshop on Venus Exploration Targets is also being planned for the early summer of 2014. The workshop will provide a forum for the Venus science community to discuss approaches for addressing high priority investigations. Participants will be encouraged to present their ideas for specific targets on Venus (interior, surface and atmosphere) as well as to present specific data requirements (measurement type, resolution, precision, etc.) needed to answer key questions.

Glaze, L. S.; Beauchamp, P. M.; Chin, G.; Crisp, D.; Grimm, R. E.; Herrick, R. R.; Johnston, S.; Limaye, S. S.; Smrekar, S. E.; Ocampo, A.; Thompson, T. W.

2013-12-01

70

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

71

International Collaboration for Venus Exploration  

Science.gov (United States)

The Venus Exploration Analysis Group (VEXAG) was established by NASA in July 2005 to identify scientific priorities and strategy for exploration of Venus. From the outset, VEXAG has been open to the international community participation and has followed the progress of the ESA Venus Express Mission and the JAXA Akasuki mission as well exploring potential broad international partnerships for Venus exploration through coordinated science and missions. This paper discussed three mechanisms through which these collaborations are being explored in which VEXAG members participate One pathway for international collaboration has been through COSPAR. The International Venus Exploration Working Group (IVEWG) was formed during the 2012 COSPAR general assembly in Mysore, India. Another potentially significant outcome has been the IVEWG’s efforts to foster a formal dialog between IKI and NASA/PSD on the proposed Venera D mission resulting in a meeting in June 2013 to be followed by a discussion at the 4MS3 conference in October 2013. This has now resulted in an agreement between NASA/PSD and IKI to form a joint Science Definition Team for Venera D. A second pathway has been through an international focus on comparative climatology. Scientists from the established space faring nations participated in a first international conference on Comparative Climatology for Terrestrial Planet (CCTP) in Boulder Colorado in June 2012 sponsored by several international scientific organizations. A second conference is planned for 2015. The Planetary Robotics Exploration Coordinating Group (PRECG) of International Academy of Astronautics (IAA) the IAA has been focusing on exploring affordable contributions to the robotic exploration by non-space-faring nations wishing to get involved in planetary exploration. PRECG has sponsored a two year study of Comparative Climatology for which Venus is the focal point and focused on engaging nations without deep space exploration capabilities. A third area of interchange has been the International Planetary Probe Workshop (IPPW) , now in its eleventh year, which brings together scientists, technologists and mission designers interested in the exploration of planets with atmospheres and particularly in the challenges of entry, descent and landing and sustained flight on other planets. IPPW has been an opportunity for developing the collaborations at a grass roots level. With both NASA and ESA favoring competitive rather than strategic approaches for selecting planetary missions (except for Moon and Mars), future collaboration on Venus exploration will involve flexible partnerships. However, international standards for proximity communication frequencies and protocols will be vital to international collaboration.

Cutts, James; Limaye, Sanjay; Zasova, Ludmila; Wilson, Colin; Ocampo, Adriana; Glaze, Lori; Svedhem, H.; Nakamura, Masato; Widemann, Thomas

72

Vertical structure of Venus polar thermosphere from in-situ data of the Venus Express Atmospheric Drag Experiment (VExADE)  

Science.gov (United States)

The Venus Express Atmospheric Drag Experiment (VExADE) has enabled first ever in-situ measurements of the density of the near-polar thermosphere of Venus above an altitude of 165 km. The measured values have been compared with existing models such as VTS3, which has been built mainly with the Pioneer Venus Orbiter Mass Spectrometer (PV-ONMS) data taken near 16? latitude, but extrapolated globally. The VExADE density values have been derived from the Precise Orbit Determination (POD) of the VEx spacecraft using both navigation and dedicated tracking data around pericenter passes during several VExADE campaigns. The last campaign has also benefited from the Planetary Radio Interferometry and Doppler Experiment (PRIDE) tracking. The combination of POD techniques has provided 46 reliable estimates of the polar thermosphere density. An independent set of density measurements was also taken by inferring the torque of the VEx spacecraft exerted by Venus’ upper atmosphere on the spacecraft during pericenter passes. This method has provided more than 120 density values in remarkably good agreement with the density values provided by the POD method. To date, the VExADE data have probed a range of 160 to 185 km in altitude, 80 to 90 degrees North in latitude and 5 to 20 hours in local time. While sampling in these ranges is insufficient to establish detailed horizontal density structures of the polar thermosphere a set of important properties can be inferred. First, the densities are lower by a factor of around 1.5 than the densities predicted by VTS3. At the same time, we find the density scale heights of VExADE and VTS3 to be consistent. Second, the density values exhibit strong variability, which is not taken into account in the VTS3 model. In order to investigate this dynamical behavior of the polar thermosphere, the ratio between the VExADE and VTS3 density has been analyzed. The latitude, altitude and local time trends are tentatively identified, but the sparse sampling provided by the VExADE data prevents us from drawing any definitive conclusions. We tentatively interpret the measured densities by a vertical wave-like pattern in the thermosphere with the amplitude of about 40% of the mean density value and a vertical wavelength of about 15 km. The causes of this vertical structure are as yet unknown. In order to improve sampling in this altitude range and thereby advance our understanding of the behavior of the polar thermosphere, further measurements are needed. An opportunity will be offered by the forthcoming aerobraking campaign scheduled for June-July 2014. The altitude of the spacecraft will decrease down to 130 km where the sensitivity of the accelerometer will enable density measurements. Tracking data and torque data may still be used to provide reliable density measurements at higher altitudes (150 to 185 km range).

Mueller-Wodarg, Ingo; Svedhem, Håkan; Bruinsma, Sean; Gurvits, Leonid; Cimo, Giuseppe; Molera Calves, Guifre; Bocanegra Bahamon, Tatiana; Rosenblatt, Pascal; Duev, Dmitry; Marty, Jean-Charles; Progebenko, Sergei

73

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

74

The characteristics of the O2 Herzberg II and Chamberlain bands observed with VIRTIS/Venus Express  

Science.gov (United States)

The oxygen Venus nightglow emissions in the visible spectral range have been known since the early observations from the Venera spacecraft. Recent observations with the VIRTIS instrument on board Venus Express allowed us to re-examine the Herzberg II system of O2 and to further study its vertical distribution, in particular the (0-?? with ?? = 7-13) bands. The present work describes the vertical profile of the observed bands and relative intensities from limb observation data. The wavelength-integrated intensities of the Herzberg II bands, with ?? = 7-11, are inferred from the recorded spectra. The resulting values lie in the range of 84-116 kR at the altitudes of maximum intensity, which are found to lie in the range of 93-98 km. Three bands of the Chamberlain system, centered at 560 nm, 605 nm, and 657 nm have been identified as well. Their emission peak is located at about 100 km, 4 km higher than the Herzberg II bands. For the first time, the O2 nightglow emissions were investigated simultaneously in the visible and in the IR spectral range, showing a good agreement between the peak position for the Herzberg II and the O2(a?g-X?g-) bands. An airglow model, proposed by Gérard et al. (Gérard, J.C., Soret, L., Migliorini, A., Piccioni, G. [2013]. Icarus.) starting from realistic O and CO2 vertical distributions derived from Venus-Express observations, allows reproduction of the observed profiles for the three O2 systems.

Migliorini, A.; Piccioni, G.; Gérard, J. C.; Soret, L.; Slanger, T. G.; Politi, R.; Snels, M.; Drossart, P.; Nuccilli, F.

2013-03-01

75

Venus - summary and review of science research activities 1983-87  

International Nuclear Information System (INIS)

The geology, geomorphology, and atmosphere of Venus are characterized on the basis of observations obtained with the Soviet Venera 15 and 16 spacecraft (including two international Vega balloon experiments), the Pioneer Venus Orbiter, and the Arecibo radio telescope during the period 1983-1986. Features discussed include impact craters, evidence of tectonic and volcanic activity, the high average age of the Venusian surface (apparently over 1 Gyr, indicating resurfacing rates much lower than on earth), and atmospheric temperature differences across the equator. 85 references

76

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

77

A Venus Flagship Mission: Exploring a World of Contrasts  

Science.gov (United States)

Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission to Venus. This 3- to 4 billon mission, to launch in the post 2020 timeframe, should revolutionize our understanding of how climate works on terrestrial planets, including the close relationship between volcanism, tectonism, the interior, and the atmosphere. It would also more clearly elucidate the geologic history of Venus, including the existence and persistence of an ancient ocean. Achieving these objectives will provide a basis to understand the habitability of extra solar terrestrial planets. To address a broad range of science questions this mission will be composed of flight elements that include an orbiter that is highlighted by an interferometric SAR to provide surface topographic and image information at scales one to two orders of magnitude greater than that achieved by any previous spacecraft to Venus. Two balloons with a projected lifetime of weeks will probe the structure and dynamics of the atmosphere at an altitude of 50 to 70-km. In addition, two descent probes will collect data synergistic to that from the balloon and analyze the geochemistry of surface rocks over a period of hours. The technology road map focuses on key areas of science instruments and enabling engineering to provide greater in situ longevity in the hostile Venus environment.

Senske, D.; Bullock, M.; Balint, T.; Benz, A.; Campbell, B.; Chassefiere, E.; Colaprete, A.; Cutts, J.; Glaze, L.; Gorevan, S.; Grinspoon, D.; Hall, J.; Hasimoto, G.; Head, J.; Hunter, G.; Johnson, N.; Kiefer, W.; Kolawa, E.; Kremic, T.; Kwok, J.; Limaye, S.; Mackwell, S.; Marov, M.; Peterson, C.; Schubert, G.; Spilker, T.; Stofan, E.; Svedhem, H.; Titov, D.; Treiman, A.

2008-12-01

78

Limb Altitude and the Southern Hemispheric Vortex Observed by Venus Monitoring Camera on VEX Orbiter  

Science.gov (United States)

The Venus Monitoring Camera (VMC) on European Space Agency's Venus Express orbiter has been collecting almost daily images at four wavelengths (365, 550, 980 and 1050 nm) since June 2006 with a few gaps during solar conjunctions. These data provide a nearly continuous record of the southern vortex (Limaye at al. 2009) that spans the entire hemisphere and reveal a dynamic, constantly evolving structure and showing a range of dynamical instability features in the central region. These instability features are also seen in the near infrared observations from the VIRTIS instrument on Venus Express (Luz et al. 2011). Some similarities between the Venus hemispheric vortex and a tropical cyclone have been previously noted (Suomi and Limaye, 1981; Limaye et al., 2009; 2011) and more have been discovered from the VMC observations. While the details of the spatial structure of the vortex is easily observed from the imaging observations at ultraviolet (VMC) and near infrared wavelengths (VIRTIS), the vertical structure is more difficult to determine from Venus Express. Here we present inferences about the vertical level obtained from the visible limb of the planet in VMC images. The altitude of the limb has been measured using full or near full disk images and depicts the altitude of the Venus cloud cover which comprises the vortex circulation. By precisely locating the limb location by fitting each limb profile in the VMC images, the average latitudinal profile of the limb altitude has been estimated. Although the pixel size of the images used is ~ 30-45 km, the large number of images (> 25,000) provides a very large sample of limb altitude determinations at each latitude between the equator and about 60° S latitude enabling sub-pixel variations of the limb altitude. The latitudinal profile of the limb altitude is similar to that inferred from the near infrared observations from VIRTIS (Ignatiev et al., 2009; Cottini et al., 2012) - high in low latitudes and low in polar latitudes and is consistent with the vortex structure. References Cottini, V., N.I. Ignatiev, G. Piccioni, P. Drossart, D. Grassi, W.J. Markiewicz (2012), Water vapor near the cloud tops of Venus from Venus Express/VIRTIS dayside data, Icarus, 217, 561-569. Ignatiev, N.I., D. V. Titov, G. Piccioni, P. Drossart, W. J. Markiewicz, V. Cottini, Th. Roatsch, M. Almeida, and N. Manoel, (2009), Altimetry of the Venus cloud tops from the Venus Express observations, J. Geophys. Res., DOI: 10.1029/2008JE003320. Limaye, S.S., J.P. Kossin, C. Rozoff, G. Piccioni, D.V. Titov, W.K. Markiewicz (2009) Vortex circulation on Venus: dynamical similarities with terrestrial hurricanes, Geophys. Res.Lett., 36, L04204, doi:10.1029/2008GL036093. Limaye, S., R.J. Krauss, D. Santek and W. Markiewicz (2011), Global Cloud Organization and Motions on Venus from the Venus Monitoring Camera on Venus Express, EPSC Abstracts, Vol. 6, EPSC-DPS2011-1230, 2011.T@ Luz, D., et al., "Venus's Southern Polar Vortex Reveals Precessing Circulation", published online on Science Express, 7 April 2011. DOI:10.1126/science.1201629. Suomi, V. E., and S. S. Limaye (1978), Venus: Further evidence of vortex circulation, Science, 201, 1009- 1011.

Limaye, Sanjay; Krauss, Robert; Markiewicz, Wojciech

2013-04-01

79

Venus geology  

Science.gov (United States)

The Magellan mission to Venus is reviewed. The scientific investigations conducted by 243-day cycles encompass mapping with a constant incidence angle for the radar, observing surface changes from one cycle to the next, and targeting young-looking volcanos. The topography of Venus is defined by the upper boundary of the crust and upwelling from lower domains. Tectonic features such as rift zones, linear mountain belts, ridge belts, and tesserae are described. The zones of tesserae are unique to the planet. Volcanism accounts for about 80 percent of the observed surface, the remainder being volcanic deposits which have been reworked by tectonism or impacts. Magellan data reveal about 900 impact craters with flow-like ejecta resulting from the fall of meteoroids. It is concluded that the age of the Venusian surface varies between 0 and 800 million years. Tectonic and volcanic activities dominate the formation of the Venus topography; such processes as weathering and erosion are relatively unimportant on Venus.

Mclaughlin, W. I.

1991-01-01

80

Pioneer Venus: Report of a study by the Science Steering Group, June 1972. [concerning 1976, 77, 78 and 80 missions  

Science.gov (United States)

The 1976/77 multiple probe mission of the Pioneer Venus spacecraft is discussed, along with the 1978 and 1980 missions. Various questions about Venus are answered; velocities and temperatures expected in the atmosphere, atmospheric chemistry, magnetic measurements, and model atmospheres are included.

1974-01-01

 
 
 
 
81

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

82

A balloon-borne stratospheric telescope for Venus observations  

Science.gov (United States)

A terrestrial stratospheric telescope is ideally suited for making infrared observations of Venus' night hemisphere during inferior conjunctions. The near-space environment at 35 km altitude has low daytime sky backgrounds and lack of atmospheric turbulence, both of which are necessary for observing Venus' night side at the diffraction limit when Venus is close to the Sun. In addition, the duration of the observing campaign will be around 3 weeks, a time period that is achievable by current long duration flights. The most important advantage, however, will be the ability of a balloonborne telescope to clearly image Venus' night side continuously throughout a 12-hr period (more for certain launch site latitudes), a capability that cannot be matched from the ground or from the Venus Express spacecraft currently in orbit around Venus. Future missions, such as the Japanese Venus Climate Orbiter will also not be able to achieve this level of synoptic coverage. This capability will provide a detailed, continuous look at evolving cloud distributions in Venus' middle and lower cloud decks through atmospheric windows at 1.74 and 2.3 ?m, which in turn will provide observational constraints on models of Venus' circulation. The science requirements propagate to several aspects of the telescope: a 1.4-m aperture to provide a diffraction limit of 0.3" at 1.74 ?m (to improve upon non-AO ground-based resolution by a factor of 2); a plate scale of 0.1" per pixel, which in turn requires an f/15 telescope for 13 ?m pixels; pointing and stability at the 0.05" level; stray light baffling; a field of view of 2 arc minutes; ability to acquire images at 1.26, 1.74 and 2.3 ?m and ability to operate aloft for three weeks at a time. The specific implementations of these requirements are outlined in this paper. Briefly, a 1.4-m Gregorian telescope is proposed, with stray light baffling at the intermediate focus. A three-stage pointing system is described, consisting of a coarse azimuthal rotator, a moderate pointing system based on a star tracker and ALT/AZ gimbals, and a fine pointing system based on analog photodiodes and a fine steering mirror. The science detectors are not discussed here, except to specify the requirement for moderate resolution (R > 1000) spectroscopy.

Young, Eliot F.; Bullock, Mark A.; Kraut, Alan; Orr, Graham; Swartzlander, Kevin; Wimer, Tony; Wong, Elton; Little, Patrick; Nakaya, Yusuke; Mellon, Russell; Germann, Lawrence

2008-07-01

83

Return to Venus of the Japanese Venus Climate Orbiter AKATSUKI  

Science.gov (United States)

Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles' deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec. 7, 2010. The engine shut down before the planned reduction in speed to achieve. The spacecraft did not enter the Venus orbit but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov. 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS.

Nakamura, Masato; Kawakatsu, Yasuhiro; Hirose, Chikako; Imamura, Takeshi; Ishii, Nobuaki; Abe, Takumi; Yamazaki, Atsushi; Yamada, Manabu; Ogohara, Kazunori; Uemizu, Kazunori; Fukuhara, Tetsuya; Ohtsuki, Shoko; Satoh, Takehiko; Suzuki, Makoto; Ueno, Munetaka; Nakatsuka, Junichi; Iwagami, Naomoto; Taguchi, Makoto; Watanabe, Shigeto; Takahashi, Yukihiro; Hashimoto, George L.; Yamamoto, Hiroki

2014-01-01

84

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

CERN Document Server

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 characterized using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCA Tter (EISCA T) radar system. Simultaneously, the global structure and evolution of these features was characterized 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...

Dorrian, Gareth; Davies, Jackie; Rouillard, Alexi; Fallows, Richard; Whittaker, Ian; Brown, Daniel; Harrison, Richard; Davis, Chris; Grande, Manuel; 10.1007/s11207-010-9599-z

2012-01-01

85

Venus Climate Orbiter: Japan's First Mission to Venus  

Science.gov (United States)

Venus Climate Orbiter (VCO), aka Planet-C, is the first Venus exploration mission of Japan Aerospace Exploration Agency (JAXA), which now is in the phase B study. VCO is scheduled to be launched via M-V rocket around 2009-2010. Arrival to Venus will be in late 2010. The main target of VCO is the meteorology of this Earth's twin sister. The wind system of Venus is characterized by so-called super-rotation: the atmosphere at the cloud-top level rotates around the planet within 4 Earth days, although the planet itself rotates much slower at a period of 243 Earth days. To study in detail the atmospheric dynamics of Venus, VCO will be inserted to a nearly-equatorial and retrograde orbit around the planet. The orbit is an elongated ellipse (30 hours period) with the periapsis at 300 km from the planet's surface and the apoapsis at 13 Venus radii. The orbit is so designed that the angular motion of the spacecraft is synchronized with the westward motion of the cloud-level atmosphere as longer time as possible. Thus, VCO is expected to perform just as the geostationary meteorological satellites do. Five cameras onboard VCO will produce successive global images at a variety of wavelengths while the spacecraft is in this portion of the orbit. Such images will enable us to derive the three-dimensional global structure of the atmospheric circulation. The shadow of Venus is utilized for observing lightning and airglow. Radio occultation will also be performed to observe the vertical profiles of temperature and sulfuric acid vapor. We expect the data obtained from VCO will complements scientific results from ESA's Venus Express Mission and greatly enhance our knowledge about Venus. A new research field ``Planetary Meteorology" will be opened by this new mission.

Nakamura, M.; Imamura, T.; Abe, T.; Ishii, N.; Ueno, M.

2005-08-01

86

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

87

Venus Transit  

Science.gov (United States)

This is an activity about the Venus Transit and how it helped astronomers determine the scale of the solar system. Learners will use measurement, ratios, and graphing to construct a model of the solar system and determine the relationship of each planet to the Sun. They will explore the scales needed to represent the size of the planets and the distances to the Sun. This activity corresponds to the NASA CONNECT video, titled Venus Transit, and has supplemental questions to support the video viewing.

88

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

89

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

90

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

91

Orbital Reconnaissance of Pyroclastic Deposits on Venus  

Science.gov (United States)

A survey of volcanoes using high-resolution radar polarimetry would enable a global search for pyroclastic deposits. Identifying the locations, extents, and relative ages of these deposits is important for multiple Venus science goals.

Carter, L. M.; Campbell, D. B.; Campbell, B. A.

2014-05-01

92

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

93

New measurements of Venus winds with ground-based Doppler velocimetry at CFHT  

Science.gov (United States)

Since Venus Express spacecraft operations started in 2006, an ongoing effort has been made to coordinate its operations with observations from the ground using various techniques and spectral domains (Lellouch and Witasse, 2008). We present an analysis of Venus Doppler winds at cloud tops based on observations made at the Canada France Hawaii 3.6-m telescope (CFHT) with the ESPaDOnS visible spectrograph. These observations consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37-1.05 ?m) to measure the winds at cloud tops using the Doppler shift of solar radiation scattered by cloud top particles in the observer's direction (Widemann et al., 2007, 2008). The observations were made during 19-20 February 2011 and were coordinated with Visual Monitoring Camera (VMC) observations by Venus Express. The complete optical spectrum was collected over 40 spectral orders at each point with 2-5 seconds exposures, at a resolution of about 80000. The observations included various points of the dayside hemisphere at a phase angle of 67°, between +10° and -60° latitude, in steps of 10° , and from +70° to -12° longitude relative to sub-Earth meridian in steps of 12°. The Doppler shift measured in scattered solar light on Venus dayside results from two instantaneous motions: (1) a motion between the Sun and Venus upper cloud particles; (2) a motion between the observer and Venus clouds. The measured Doppler shift, which results from these two terms combined, varies with the planetocentric longitude and latitude and is minimum at meridian ?N = ?Sun - ?Earth where the two components subtract to each other for a pure zonal regime. Due to the need for maintaining a stable velocity reference during the course of acquisition using high resolution spectroscopy, we measure relative Doppler shifts to ?N. The main purpose of our work is to provide variable wind measurements with respect to the background atmosphere, complementary to simultaneous measurements made with the VMC camera onboard the Venus Express. We will present first results from this work, comparing with previous results by the CFHT/ESPaDOnS and VLT-UVES spectrographs (Machado et al., 2012), with Galileo fly-by measurements and with VEx nominal mission observations (Peralta et al., 2007, Luz et al., 2011). Acknowledgements: The authors acknowledge support from FCT through projects PTDC/CTE-AST/110702/2009 and PEst-OE/FIS/UI2751/2011. PM and TW also acknowledge support from the Observatoire de Paris. Lellouch, E., and Witasse, O., A coordinated campaign of Venus ground-based observations and Venus Express measurements, Planetary and Space Science 56 (2008) 1317-1319. Luz, D., et al., Venus's polar vortex reveals precessing circulation, Science 332 (2011) 577-580. Machado, P., Luz, D. Widemann, T., Lellouch, E., Witasse, O, Characterizing the atmospheric dynamics of Venus from ground-based Doppler velocimetry, Icarus, submitted. Peralta J., R. Hueso, A. Sánchez-Lavega, A reanalysis of Venus winds at two cloud levels from Galileo SSI images, Icarus 190 (2007) 469-477. Widemann, T., Lellouch, E., Donati, J.-F., 2008, Venus Doppler winds at Cloud Tops Observed with ESPaDOnS at CFHT, Planetary and Space Science, 56, 1320-1334.

Machado, P.; Widemann, T.; Luz, D.; Peralta, J.; Berry, D. L.

2012-04-01

94

A Bright Spot on Venus  

Science.gov (United States)

In July 2009 the ultraviolet images of Venus captured by the Venus Monitoring Camera (VMC) on Venus Express showed an anomalously bright feature. The brightness was about 30% higher than generally observed on Venus. Although the initial detection was made in the images acquired on the same date (19 July 2009) that several amateur images also reported a bright spot on Venus, the brightening was present about four days earlier. The bright anomaly remained localized to an area centered at approximately 40° S and 151° longitude with a radial extent of ~ 400 km. The VMC images were being acquired every 30 minutes, and they bright core region indicates an oscillatory behavior in the peak brightness region. The bright core gradually dissipated over the next several orbits. This brightening was quite distinct from an earlier major event observed in January 2007 when a very large portion of the southern hemisphere brightened and then quickly returned to normal appearance. The July brightening was not seen in images acquired through other VMC filters, thus the cause of the brightening is a puzzle. The change in the reflective properties of a limited region suggests an unusual trigger. A dynamical (convective) cause is possible but there can be other origins also. A volcanic eruption is one possibility, a solar wind connection is another, an external impact cannot be ruled out either. The challenge is to identify the cause of the brightening from the limited observations available.

Limaye, Sanjay; Markiewicz, Wojciech; Titov, Dimitry

2010-05-01

95

First operations of the SOIR occultation infrared spectrometer in Venus orbit.  

Science.gov (United States)

Since May 2006, the Venus-Express spacecraft is in its nominal orbit around VENUS and the SPICAV optical package has begun to acquire spectra. The SOIR extension to SPICAV is an echelle spectrometer associated to an AOTF (Acousto-Optical Tunable Filter) for the order selection, which performs solar occultation measurements in the IR region (2.2-4.3 µm) at a resolution of 0.1 cm-1 . The detailed optical study and design as well as the manufacturing were performed at the BIRA/IASB in collaboration with its industrial partners OIP and PEDEO. It was funded by the Belgian Federal Science Policy Office under the ESA PRODEX programme. The wavelength range allows a detailed chemical inventory of the Venus atmosphere above the cloud layer with an emphasis on vertical distribution of gases. The first results look promising and will be qualitatively presented.

Nevejans, D.; Neefs, E.; Vandaele, A. C.; Muller, C.; Fussen, D.; Berkenbosch, S.; Clairquin, R.; Korablev, O.; Federova, A.; Bertaux, J. L.

96

Characterizing atmospheric waves on Venus, Earth, and Mars  

Science.gov (United States)

Atmospheric Waves Workshop; Noordwijk, Netherlands, 9-10 November 2011 Experts in observations and modeling of atmospheric waves from the Earth and planetary atmospheric science communities came together at a November 2011 workshop held at the European Space Agency's (ESA) European Space Research and Technology Centre ( ESTEC) site in the Netherlands to discuss the nature of waves observed in Venus's atmosphere and their comparison to those on Earth and Mars. ESA's Venus Express (VEx) satellite and ground-based observers find atmospheric waves at many scales. Migrating solar tides and other planetary- scale waves are observed in cloud- tracking wind vectors and temperature fields. Mesoscale gravity waves (GWs) can also be seen at a variety of levels from the cloud base up to the thermosphere, evident in imagery and in vertical profiles of temperature, density, and aerosol abundance. This workshop focused particularly on GWs, as their role in the atmospheric circulation is still poorly understood.

Wilson, Colin F.; Piccialli, Arianna

2012-06-01

97

Venus in motion. [Mariner 10 television pictures  

Science.gov (United States)

A comprehensive set of television pictures of Venus taken by the Mariner 10 spacecraft is presented. Included is a chronological sequence of television images illustrating the development, variety, and circulation of Venus upper-atmospheric phenomena as viewed in the near-ultraviolet. The higher-resolution images have been assembled into global mosaics to facilitate comparison. Figures and tables describing the imaging sequences have been included to provide a guide to the more complete set of 3400 Venus images on file at the National Space Science Data Center.

Anderson, J. L.; Danielson, G. E.; Evans, N.; Soha, J. M.; Belton, M. J. S.

1978-01-01

98

Venus: Water and Life  

Science.gov (United States)

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.

2013-05-01

99

The Atmosphere and Climate of Venus  

Science.gov (United States)

Venus lies just sunward of the inner edge of the Sun's habitable zone. Liquid water is not stable. Like Earth and Mars, Venus probably accreted at least an ocean's worth of water, although there are alternative scenarios. The loss of this water led to the massive, dry CO2 atmosphere, extensive H2SO4 clouds (at least some of the time), and an intense CO2 greenhouse effect. This chapter describes the current understanding of Venus' atmosphere, established from the data of dozens of spacecraft and atmospheric probe missions since 1962, and by telescopic observations since the nineteenth century. Theoretical work to model the temperature, chemistry, and circulation of Venus' atmosphere is largely based on analogous models developed in the Earth sciences. We discuss the data and modeling used to understand the temperature structure of the atmosphere, as well as its composition, cloud structure, and general circulation. We address what is known and theorized about the origin and early evolution of Venus' atmosphere. It is widely understood that Venus' dense CO2 atmosphere is the ultimate result of the loss of an ocean to space, but the timing of major transitions in Venus' climate is very poorly constrained by the available data. At present, the bright clouds allow only 20% of the sunlight to drive the energy balance and therefore determine conditions at Venus' surface. Like Earth and Mars, differential heating between the equator and poles drives the atmospheric circulation. Condensable species in the atmosphere create clouds and hazes that drive feedbacks that alter radiative forcing. Also in common with Earth and Mars, the loss of light, volatile elements to space produces long-term changes in composition and chemistry. As on Earth, geologic processes are most likely modifying the atmosphere and clouds by injecting gases from volcanos as well as directly through chemical reactions with the surface. The sensitivity of Venus' atmospheric energy balance is quantified in this chapter in terms of the initial forcing due to a perturbation, radiative response, and indirect responses, which are feedbacks — either positive or negative. When applied to one Venus climate model, we found that the albedo-radiative feedback is more important than greenhouse forcing for small changes in atmospheric H2O and SO2. An increase in these gases cools the planet by making the clouds brighter. On geologic timescales the reaction of some atmospheric species (SO2, CO, OCS, S, H2O, H2S, HCl, HF) with surface minerals could cause significant changes in atmospheric composition. Laboratory data and thermochemical modeling have been important for showing that atmospheric SO2 would be depleted in ~10 m.y. if carbonates are available at the surface. Without replenishment, the clouds would disappear. Alternatively, the oxidation of pyrite could add SO2 to the atmosphere while producing stable Fe oxides at the surface. The correlation of near-infrared high emissivity (dark) surface features with three young, large volcanos on Venus is strong evidence for recent volcanic activity at these sites, certainly over the timescale necessary to support the clouds. We address the nature of heterogeneous reactions with the surface and the implications for climate change on Venus. Chemical and mineralogical signatures of past climates must exist at the surface and below, so in situ experiments on the composition of surface layers are vital for reconstructing Venus' past climate. Many of the most Earth-like planets found around other stars will probably resemble Venus or a younger version of Venus. We finish the chapter with discussing what Venus can tell us about life in the universe, since it is an example of a planetary climate rendered uninhabitable. It also resembles our world's likely future. As with the climate history of Venus, however, the timing of predictable climate transitions on the Earth is poorly constrained by the data.

Bullock, M. A.; Grinspoon, D. H.

100

Venus's southern polar vortex reveals precessing circulation.  

Science.gov (United States)

Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis. PMID:21474710

Luz, D; Berry, D L; Piccioni, G; Drossart, P; Politi, R; Wilson, C F; Erard, S; Nuccilli, F

2011-04-29

 
 
 
 
101

Exploring the Planets: Venus  

Science.gov (United States)

This site contains most of the up-to-date information known about the planet Venus, including mean distance from Sun, length of year, rotation period, mean orbital velocity, inclination of axis, average temperature (day and night), and diameter. Many discoveries about Venus have been made using Earth-based radio telescopes, however the images of Venus in this exhibit were collected by the Magellan spacecraft. Magellan used radar to produce the first high-resolution global map of Venus. Since Venus has no water erosion and little wind, volcanic eruptions are a major force reshaping the landscape. Geologic forces at work beneath the crust create mountains, rifts, and patterns of fractures, while the sluggish winds sculpt the surface in subtler ways but many mysteries remain. This site includes numerous images of the planet.

102

Venus Ionosphere and Solar Wind Interaction  

Science.gov (United States)

Venus Express, which was inserted into orbit in mid-2006, has added significantly to the knowledge gained from Pioneer Venus from 1978 to 1992. This observational database interpreted in terms of modern multi-fluid codes and hybrid simulations has deepened our understanding of Earth’s very different twin sister planet. Furthermore, the very different orbits of VEX and PVO has allowed the more complete mapping of the volume of space around the planet. Now the bow shock has been probed over its full surface, the ionosphere mapped everywhere, and the tail studied from the ionosphere to 12 Venus radii. Some unexpected discoveries have been made. The exospheric hydrogen at Venus, unlike that at Mars, does not produce ion-cyclotron waves, perhaps because the stronger gravity of Venus produces a smaller geocorona. The solar wind interaction drapes the magnetic field around the planet, and a strong layer of magnetic field builds up at low altitudes. While the layer does not appear to penetrate into the dayside atmosphere (perhaps diffusing only slowly through the low atmosphere), it does appear to dip into the atmosphere at night. Surprisingly, over the poles, this layer is most strongly seen when the IMF BY component has a positive Y-component in Venus-Solar-Orbital coordinates. Multi-fluid simulations show that this result is consistent with the pressure of significant ion densities of ions with quite different mass which causes magnetic polarity control of the ion flow over the terminators. Reconnection is found in the tail close to the planet, and the structure of the outer tail found by PVO is confirmed to exist in the inner tail by VEX. When combined, the VEX and PVO Data provide a very comprehensive picture of the physics of the solar wind interaction with the ionosphere of Venus.

Russell, C. T.; Luhmann, Janet G.; Ma, Yingjuan; Zhang, Tielong; Villarreal, M.

103

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

104

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

105

Magellan Mission to Venus  

Science.gov (United States)

The Magellan Mission to Venus Home is now available at NASA's Jet Propulsion Lab. The Magellan mission ended with a dramatic plunge into the atmosphere of Venus, the first time an operating spacecraft has ever been intentionally crashed into a planet. On October 11, 1994, Magellan's thrusters were fired in four sequences to lower its orbit into the atmosphere of Venus for its final experiment -- to gather data on Venus' high atmosphere. Within two days after these maneuvers, the spacecraft became caught in the atmosphere and plunged to the surface. Although most of Magellan will be vaporized during the fiery descent, some sections of the spacecraft will probably hit the planet's surface. The latest updates on Magellan's status -- as well as a comprehensive gallery of images and information from the five-year mission -- are available on the home page.

106

Venus Transit 2004  

Science.gov (United States)

In just several weeks, Venus, the Earth's sister planet, will pass in front of the sun, affording astronomers and the general public the ability to take part in a extremely rare event. While persons in Europe, Africa, and Asia will have the best vantage point for this occurrence, those interested in the Venus transit will want to take a detailed look at this lovely website in order to find out more about the event. Launched by the European Southern Observatory and the European Association for Astronomy Education (in cooperation with three other organizations), the site contains ample information about the latest news from the project, detailed background material about this astronomical event, the network of institutions involved with the project, and information on how individuals may participate in the Venus Transit 2004 project. One of the most helpful areas contains animations of the Venus transit from different perspectives.

107

Global scale concentrations of volcanic activity on Venus: A summary of three 23rd Lunar and Planetary Science Conference abstracts. 1: Venus volcanism: Global distribution and classification from Magellan data. 2: A major global-scale concentration of volcanic activity in the Beta-Atla-Themis region of Venus. 3: Two global concentrations of volcanism on Venus: Geologic associations and implications for global pattern of upwelling and downwelling  

Science.gov (United States)

As part of the analysis of data from the Magellan Mission, we have compiled a global survey of the location, dimensions, and subsidiary notes of all identified volcanic features on Venus. More than 90 percent of the surface area was examined and the final catalog comprehensively identifies 1548 individual volcanic features larger than approximately 20 km in diameter. Volcanic features included are large volcanoes, intermediate volcanoes, fields of small shield volcanoes, calderas, large lava channels, and lava floods as well as unusual features first noted on Venus such as coronae, arachnoids, and novae.

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

1992-01-01

108

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

109

Can Venus shed microorganisms?  

Science.gov (United States)

The pale featureless cloud tops of Venus reveal a rich complexity when viewed in ultraviolet. These features result from an unknown absorber brought up from lower atmospheric levels by convection, particularly at lower latitudes. While the surface of Venus is extremely hostile to life as we know it, there exists a habitable region in the atmosphere, centered at approximately 50 km, where the temperature ranges from 30 to 80ºC and the pressure is one bar. Numerous examples of cloud-borne life exist on Earth. However, the environment in the Venus atmospheric habitable zone has only a few ppm of water which is present as misty droplets, strong sulfuric acid, and intense UV illumination. The proposal that putative cloud-borne life forms in Venus' atmospheric habitable zone can be transported to Earth by a solar conveyance face several challenges. Vigorous convective mixing, especially at the lower latitudes is considered as a means of transport to the upper reaches of Venus' atmosphere. Potential propulsive forces imparted by both solar wind and sunlight pressure are considered as a means of achieving escape velocity from Venus. Additional hurdles include direct exposure by such transported life forms to the rigors of the space environment. These are contrasted to those experienced by microorganisms that may be carried within meteorites and comets. A middle ground is perhaps demonstrated by plankton that has been observed at high altitudes on Earth, likely lofted there by a hurricane, which is encased in protective ice crystals.

Konesky, Gregory

2009-08-01

110

A conceptual venus rover mission using advanced radioisotope power system  

Science.gov (United States)

The primary goal of this study is to examine the feasibility of using the novel Advanced RPS-driven Stirling thermoacoustic system to enable extended science operations in the extremely hostile surface environment of Venus. The mission concept entails landing a rover onto the Venus surface, conducting science measurements in different areas on the surface, and returning the science data to Earth. The study focused on developing a rover design to satisfy the science goals with the capability to operate for 60 days. This mission life influences several design parameters, including Earth elevation angle and the maximum communications range to Earth.

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

2006-01-01

111

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

112

Study of Venus cloud layers with polarimetric data from SPICAV/VEx  

Science.gov (United States)

The study of Venus's cloud layers is important in order to understand the structure, radiative balance and dynamics of the Venusian atmosphere. The main cloud layers between 50 and 70km are thought to consist in ~ 1 ?m radius droplets of a H2SO4-H2O solution. Nevertheless, the composition and the size distribution of the droplets are difficult to constrain more precisely. Polarization measurements have given great results in the determination of the constituents of the haze. In the early 1980s, Kawabata et al.(1980) used the polarization data from the OCPP instrument on the spacecraft Pioneer Venus to constrain the properties of the haze. They obtained a refractive index of 1.45 ± 0.04 at ? = 550nm effective radius of 0.23 ± 0.04?m, with a normalized size distribution variance of 0.18 ± 0.1. We introduce here new polarimetric measurements from the SPICAV-IR spectrometer onboard ESA's Venus Express. Observing Venus in the visible and IR from 650 nm to 1625 nm with a good spatial and temporal converage, SPICAV gives us an opportunity to put better constraints on haze and cloud particles at Venus cloud top, as well as their spatial and temporal variability. Our analysis is based on a polarized radiative transfer code similar to the one used by Hansen and Hovenier (1974). Using the particle size distribution from Kawabata et al.(1980) and a simple two-layered cloud model, we try to retrieve particle size and refrative index from nadir observations. We are interested in particular by the glory which is also visible in polarization and whose linear degree of polarization as a function of observation geometry is dependent on the cloud parameters. The polarization measured at higher latitudes provides constrains on the hazes, in particular their optical thickness. We will discuss the first results of our modeling of the glory. In the future we aim to characterize the cloud droplets on the planet along with their temporal and spatial variability. A comparison with the photometric observations of the glory from VMC could also provide stronger constrains on the size and composition of the cloud particles. References: HANSEN, J. E. AND HOVENIER, J. W., Interpretation of the polarization of Venus., Journal of Atmospheric Sciences, 1974. KAWABATA et al., Cloud and haze properties from Pioneer Venus Polarimetry, Journal of Geophysical Research, 1980

Rossi, Loïc; Marcq, Emmanuel; Montmessin, Franck; Bertaux, Jean-Loup; Fedorova, Anna; Stam, Daphne

2014-05-01

113

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

114

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

115

The venus kinase receptor (VKR) family: structure and evolution.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

BACKGROUND: Receptor tyrosine kinases (RTK) form a family of transmembrane proteins widely conserved in Metazoa, with key functions in cell-to-cell communication and control of multiple cellular processes. A new family of RTK named Venus Kinase Receptor (VKR) has been described in invertebrates. The VKR receptor possesses a Venus Fly Trap (VFT) extracellular module, a bilobate structure that binds small ligands to induce receptor kinase activity. VKR was shown to be highly expressed in the la...

Vanderstraete, Mathieu; Gouignard, Nade?ge; Ahier, Arnaud; Morel, Marion; Vicogne, Je?ro?me; Dissous, Colette

2013-01-01

116

Chasing Venus: Putting the Transits of Venus on Exhibition  

Science.gov (United States)

The upcoming 2004 transit of Venus provides a great opportunity to develop programs to educate the public about the history of the observations of the transits. The Smithsonian Institution Libraries is well-placed to take part in this effort with its collection of rare books that deal with the 17th- and 18th-century transits. The exhibition called ``Chasing Venus" will be on display at the National Museum of American History, Behring Center, from March 2004 to April 2005. The Museum will loan a number of its 19th-century artifacts and the US Naval Observatory is also cooperating with the loan of a telescope and some rare books from the USNO Library to flesh out the story of the 19th-century transits. The talk will take a closer look at the books and artifacts that will be used to tell the history of the transit observations in the special context of a library exhibition. Books from a wide variety of authors such as Kepler, Horrocks, Capt. Cook, Rittenhouse, Mason & Dixon, and even John Philip Sousa (!) will help express the authors' excitement about the event to the public at large.

Brashear, R. S.

2003-12-01

117

Limb Altitude and Cloud Level Circulation from Venus Monitoring Camera  

Science.gov (United States)

Venus Monitoring Camera on Venus Express has returned a large number of images of the planet's cloud cover in four flters (365, 550, 965 and 1050 nm). These images have been used to investigate the global cloud level atmosphere in terms of morphology, cloud motions, limb altitude and local scale processes. Images taken at apoapsis when the Venus Express spacecraft is over the South Pole of Venus present a view of the entire day-side southern hemisphere of Venus. The visible limb is found to be somewhat higher in the morning as compared to the afternoon hours from precision limb fits. Images taken when Venus Express is closer to the planet ( > 20,000 km) provide a view of the planet's limb at other than near equatorial latitudes from which a gradual drop off of the limb altitude with increasing latitude is apparent. The entire southern hemisphere shows the same vortex organization, but many episodes of off-center location of the vortex have been observed, accompanied by varying rotation rates of the polar region. Cloud motions reveal presence of large scale waves that likely contribute to the equatorward transport of angular momentum, and hgih resolution images reveal presence of smaller scale waves whose origins are yet unconfirmed but may be related to convection in polar regions.

Limaye, S. S.; Markiewicz, W. J.; Krauss, R. J.

2012-12-01

118

Neutral Mass Spectrometry for Venus Atmosphere and Surface  

Science.gov (United States)

The nature of the divergent evolution of the terrestrial planets Venus, Earth, and Mars is a fundamental problem in planetary science that is most relevant to understanding the characteristics of small planets we are likely to discover in extrasolar systems and the number of such systems that may support habitable environments. For this reason, the National Research Council's Decadal Survey gives Venus exploration high priority. That report was the basis of the NASA selection of Venus as one of four prime mission targets for the recently initiated New Frontiers Program. If the Decadal Survey priorities are to be realized, in situ Venus exploration must remain a high priority. Remote sensing orbital and in situ atmospheric measurements from entry probe or balloon platforms might be realized under the low cost Discovery missions while both atmospheric and landed surface measurements are envisioned with the intermediate class missions of the New Frontiers Program.

Mahaffy, Paul

2004-01-01

119

Venus Transit 2004  

Science.gov (United States)

December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the astronomical unit, calculation of longitudes on the earth, and detection of Venus' atmosphere. The NASA Sun Earth Connection Education Forum in partnership with the Solar System Exploration Forum, DPS, and a number of NASA space missions is developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.

Mayo, L. A.; Odenwald, S. F.

2002-09-01

120

Heavy metal frost on Venus  

Science.gov (United States)

Chemical equilibrium calculations of volatile metal geochemistry on Venus show that high dielectric constant compounds of lead and bismuth such as PbS (galena), Bi 2S 3 (bismuthite) or Pb-Bi sulfosalts condense in the venusian highlands and may be responsible for the low radar emissivities observed by Magellan and Pioneer Venus. Our calculations also show that elemental tellurium is unstable on Venus' surface and will not condense below 46.6 km. This is over 30 km higher than Maxwell Montes, the highest point on Venus' surface. Elemental analyses of Venus' highlands surface by laser induced breakdown spectroscopy (LIBS) and/or X-ray fluorescence (XRF) can verify the identity of the heavy metal frost on Venus. The Pb-Pb age of Venus could be determined by mass spectrometric measurements of the Pb 207/Pb 204 and Pb 206/Pb 204 isotopic ratios in Pb-bearing frosts. All of these measurements are technologically feasible now.

Schaefer, Laura; Fegley, Bruce

2004-03-01

 
 
 
 
121

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

122

Morphology and dynamics of the upper cloud layer of Venus.  

Science.gov (United States)

Venus is completely covered by a thick cloud layer, of which the upper part is composed of sulphuric acid and some unknown aerosols. The cloud tops are in fast retrograde rotation (super-rotation), but the factors responsible for this super-rotation are unknown. Here we report observations of Venus with the Venus Monitoring Camera on board the Venus Express spacecraft. We investigate both global and small-scale properties of the clouds, their temporal and latitudinal variations, and derive wind velocities. The southern polar region is highly variable and can change dramatically on timescales as short as one day, perhaps arising from the injection of SO2 into the mesosphere. The convective cells in the vicinity of the subsolar point are much smaller than previously inferred, which we interpret as indicating that they are confined to the upper cloud layer, contrary to previous conclusions, but consistent with more recent study. PMID:18046394

Markiewicz, W J; Titov, D V; Limaye, S S; Keller, H U; Ignatiev, N; Jaumann, R; Thomas, N; Michalik, H; Moissl, R; Russo, P

2007-11-29

123

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

124

History of Venus Observations  

Science.gov (United States)

Our image of Venus is that of a hellish, hot planet, permanently covered by fast-moving clouds, with its surface inaccessible to any Earth-based observer. But the perception and knowledge of our sister planet has been very different in the recent and more remote past.

Bonnet, Roger-Maurice; Grinspoon, David; Rossi, Angelo Pio

125

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

126

Transit of Venus  

Science.gov (United States)

The Transit of Venus is similar to a solar eclipse, where -- from the perspective on Earth -- Venus passes in front of the Sun. This event does not happen very often. In fact, no one alive today has experienced this phenomenon, which will take place on June 8 and will be visible for most of Europe, Asia, and Africa.First, the Armagh Planetarium created a great, expansive informational site all about the Transit of Venus (1). Users can find basic facts, observing information, histories of past transits, and much more. Next, the European Southern Observatory presents the VT-2004 project's aim to gain knowledge and encourage public interest in the event (2). Users can observe Venus's progression towards the transit with the daily images from April 17, 2004 to present news updates. Educators can discover transit-related activities and educational materials. The third site, created by NASA, discusses the details of the Sun-Earth Connection Education Forum and San Francisco's Exploratorium's live webcast of the Transit (3). The site supplies enjoyable, educational materials for students, educators, museums, scientists, and amateur astronomers. The next site, also created by NASA, provides an introduction to the Venus Transits that will take place June 2004 and 2012 (4). Visitors can find helpful figures and text about the geographic visibility of the events. The site offers an observer's handbook as well as a discussion about the predictions of the event. Next, Professor Backhaus presents a project where schools, amateur astronomers, and universities will collaborate to gather transit data and learn about observing (5). Users can discover the six parts of the project as well as learn how to participate in the worldwide endeavor. The sixth site also discusses a Venus Transit project (6). Endorsed by the Astronomical Association of Zurich, this project's goals are to process data collected by amateur astronomers by different observation methods, to act as a data exchange center, and to determine the astronomical unit. Next, the Exploratorium furnishes general information about the Transit, its history, how viewers observe it, what it looks like, and why it is an important event (7). Users can find out about the live webcast that will begin on June 7, 2004 from Athens, Greece. Educators can find student activities developed to integrate discussions into the classroom. Lastly, Willie Koorts, an employee at the South African Astronomical Observatory, recounts the observations of scientists in Africa of the last transit of Venus (8). The site contains many historical photographs along with informational diagrams and figures.

127

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

128

Science, religious tolerance and freedom of expression  

Directory of Open Access Journals (Sweden)

Full Text Available In this article we offer a perspective on the immense number of problems and challenges confronting humanity in our common biosphere. As our human population grows and urbanization increases globally, billions of humans with diverse beliefs and opinions are living in large urban areas without the basic needs of life. The way forward in our biosphere is not violence and disrespect. It is working to maintain and improve our common biosphere and solve our common global problems. Religion and religious believers will need science, so humans can survive and sustain our biosphere.

Jack T. Trevors

2010-12-01

129

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

130

Venus transit 2004: An international education program  

Science.gov (United States)

December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the detection of Venus' atmosphere, calculation of longitudes, and calculation of the astronomical unit (and therefore the scale of the solar system). The NASA Sun Earth Connection Education Forum (SECEF) in partnership with the Solar System Exploration (SSE) and Structure and Evolution of the Universe (SEU) Forums, AAS Division for Planetary Sciences (DPS), and a number of NASA space missions and science centers are developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education (TIE) network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will compare the terrestrial planets in terms of the evolutionary processes that define their magnetic fields, their widely differing interactions with the solar wind, and the implications this has for life on Earth and elsewhere in the universe. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.

Mayo, L.; Odenwald, S.

2003-04-01

131

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

132

Tectonics and composition of Venus  

Science.gov (United States)

The uncompressed density of Venus is a few percent less than the Earth. The high upper mantle temperature of Venus deepens the eclogite stability field and inserts a partial melt field. A thick basaltic crust is therefore likely. The anomalous density of Venus relative to the progression from Mercury to Mars may therefore have a tectonic rather than a cosmo-chemical explanation. There may be no need to invoke differences in composition or oxidization state.

Anderson, D. L.

1980-01-01

133

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

134

Sensor Amplifier for the Venus Ground Ambient  

Science.gov (United States)

Previous Venus Landers employed high temperature pressure vessels, with thermally protected electronics, to achieve successful missions, with a maximum surface lifetime of 127 minutes. Extending the operating range of electronic systems to the temperatures (480 C) and pressures (90 bar) of the Venus ground ambient would significantly increase the science return of future missions. Toward that end, the current work describes the innovative design of a sensor preamplifier, capable of working in the Venus ground ambient and designed using commercial components (thermionic vacuum tubes, wide band gap transistors, thick film resistors, advanced high temperature capacitors, and monometallic interfaces) To identify commercial components and electronic packaging materials that are capable of operation within the specified environment, a series of active devices, passive components, and packaging materials were screened for operability at 500C, assuming a 10x increase in the mission lifetime. In addition. component degradation as a function of time at 500(deg)C was evaluated. Based on the results of these preliminary evaluations, two amplifiers were developed.

DelCastillo, Linda Y.; Johnson, Travis W.; Hatake, Toshiro; Mojarradi, Mohammad M.; Kolawa, Elizabeth A.

2006-01-01

135

The Plains of Venus  

Science.gov (United States)

Volcanic plains units of various types comprise at least 80% of the surface of Venus. Though devoid of topographic splendor and, therefore often overlooked, these plains units house a spectacular array of volcanic, tectonic, and impact features. Here I propose that the plains hold the keys to understanding the resurfacing history of Venus and resolving the global stratigraphy debate. The quasi-random distribution of impact craters and the small number that have been conspicuously modified from the outside by plains-forming volcanism have led some to propose that Venus was catastrophically resurfaced around 725×375 Ma with little volcanism since. Challenges, however, hinge on interpretations of certain morphological characteristics of impact craters: For instance, Venusian impact craters exhibit either radar dark (smooth) floor deposits or bright, blocky floors. Bright floor craters (BFC) are typically 100-400 m deeper than dark floor craters (DFC). Furthermore, all 58 impact craters with ephemeral bright ejecta rays and/or distal parabolic ejecta patterns have bright floor deposits. This suggests that BFCs are younger, on average, than DFCs. These observations suggest that DFCs could be partially filled with lava during plains emplacement and, therefore, are not strictly younger than the plains units as widely held. Because the DFC group comprises ~80% of the total crater population on Venus the recalculated emplacement age of the plains would be ~145 Ma if DFCs are indeed volcanically modified during plains formation. Improved image and topographic data are required to measure stratigraphic and morphometric relationships and resolve this issue. Plains units are also home to an abundant and diverse set of volcanic features including steep-sided domes, shield fields, isolated volcanoes, collapse features and lava channels, some of which extend for 1000s of kilometers. The inferred viscosity range of plains-forming lavas, therefore, is immense, ranging from the extremely fluid flows (i.e., channel formers), to viscous, possibly felsic lavas of steep-sided domes. Wrinkle ridges deform many plains units and this has been taken to indicate that these ridges essentially form an early stratigraphic marker that limits subsequent volcanism to a minimum. However, subtle backscatter variations within many ridged plains units suggest (but do not prove) that some plains volcanism continued well after local ridge deformation ended. Furthermore, many of volcanic sources show little, if any, indications of tectonic modification and detailed analyses have concluded that resurfacing rates could be similar to those on Earth. Improving constraints on the rates and styles of volcanism within the plains could lend valuable insights into the evolution of Venus's internal heat budget and the transition from thin-lid to thick-lid tectonic regimes. Improved spatial and radiometric resolution of radar images would greatly improve abilities to construct the complex local stratigraphy of ridged plains. Constraining the resurfacing history of Venus is central to understanding how Earth-sized planets evolve and whether or not their evolutionary pathways lead to habitability. This goal can only be adequately addressed if broad coverage is added to the implementation strategies of any future mapping missions to Venus.

Sharpton, V. L.

2013-12-01

136

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)

137

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

138

Venus: A total mass estimate  

International Nuclear Information System (INIS)

Reductions of four independent blocks of Pioneer Venus Orbiter Doppler radio tracking data have produced very consistent determinations of the GM of Venus (the product of the universal gravitational constant and total mass of Venus). These estimates have uncertainties that are significantly smaller than any values published to data. The value of GM is also consistent with previously published results in that it falls within their one-sigma uncertainties. The value of 324858.60 ± 0.05 km3/sec2 is the best estimate

139

Hall MHD Study of the Solar wind Interaction with Venus  

Science.gov (United States)

A multi-species, global, Hall MHD model is used to study the solar wind interaction with Venus ionosphere/atmosphere. This model is based on the numerical model that has been successfully applied to Mars (Ma et al., 2004), with Hall effect included. A self-consistent Venus ionosphere is calculated in the model with three ion species (O+, O2+ and CO2+). The related chemical reactions and collision processes are also considered. Our simulation domain covers the region from 100km altitude to 16 Rv in the tail. An adaptive spherical grid structure is used with radial resolution of about 15 km in the lower ionosphere. Mass-loading effect is examined for both solar maximum and solar minimum conditions. The importance of the Hall effect will be discussed. We also show comparisons between our model results with the magnetic fields observed by the magnetometer carried aboard Venus Express.

Nagy, A. F.; Ma, Y.; Russell, C. T.; Zhang, T.; Wei, H.; Strangeway, R. J.; Toth, G.

2010-12-01

140

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

 
 
 
 
141

Decadal variations in a Venus general circulation model  

Science.gov (United States)

The Community Atmosphere Model (CAM), a 3-dimensional Earth-based climate model, has been modified to simulate the dynamics of the Venus atmosphere. The most current finite volume version of CAM is used with Earth-related processes removed, parameters appropriate for Venus introduced, and some basic physics approximations adopted. A simplified Newtonian cooling approximation has been used for the radiation scheme. We use a high resolution (1° by 1° in latitude and longitude) to take account of small-scale dynamical processes that might be important on Venus. A Rayleigh friction approach is used at the lower boundary to represent surface drag, and a similar approach is implemented in the uppermost few model levels providing a ‘sponge layer’ to prevent wave reflection from the upper boundary. The simulations generate superrotation with wind velocities comparable to those measured in the Venus atmosphere by probes and around 50-60% of those measured by cloud tracking. At cloud heights and above the atmosphere is always superrotating with mid-latitude zonal jets that wax and wane on an approximate 10 year cycle. However, below the clouds, the zonal winds vary periodically on a decadal timescale between superrotation and subrotation. Both subrotating and superrotating mid-latitude jets are found in the approximate 40-60 km altitude range. The growth and decay of the sub-cloud level jets also occur on the decadal timescale. Though subrotating zonal winds are found below the clouds, the total angular momentum of the atmosphere is always in the sense of superrotation. The global relative angular momentum of the atmosphere oscillates with an amplitude of about 5% on the approximate 10 year timescale. Symmetric instability in the near surface equatorial atmosphere might be the source of the decadal oscillation in the atmospheric state. Analyses of angular momentum transport show that all the jets are built up by poleward transport by a meridional circulation while angular momentum is redistributed to lower latitudes primarily by transient eddies. Possible changes in the structure of Venus’ cloud level mid-latitude jets measured by Mariner 10, Pioneer Venus, and Venus Express suggest that a cyclic variation similar to that found in the model might occur in the real Venus atmosphere, although no subrotating winds below the cloud level have been observed to date. Venus’ atmosphere must be observed over multi-year timescales and below the clouds if we are to understand its dynamics.

Parish, Helen F.; Schubert, Gerald; Covey, Curtis; Walterscheid, Richard L.; Grossman, Allen; Lebonnois, Sebastien

2011-03-01

142

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.

1992-01-01

143

Rate of volcanism on Venus  

International Nuclear Information System (INIS)

The maintenance of the global H2SO4 clouds on Venus requires volcanism to replenish the atmospheric SO2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO2 and calcite (CaCO3) to form anhydrite (CaSO4), are reported. If the rate of this reaction is representative of the SO2 reaction rate at the Venus surface, then we estimate that all SO2 in the Venus atmosphere (and thus the H2SO4 clouds) will be removed in 1.9 million years unless the lost SO2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth

144

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

145

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

146

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

147

Promoting Creative Thinking and Expression of Science Concepts among Elementary Teacher Candidates through Science Content Movie Creation and Showcasing  

Science.gov (United States)

This article reports the phases of design and use of video editing technology as a medium for creatively expressing science content knowledge in an elementary science methods course. Teacher candidates communicated their understanding of standards-based core science concepts through the creation of original digital movies. The movies were assigned…

Hechter, Richard P.; Guy, Mark

2010-01-01

148

How Hot Can Venus Get?  

Science.gov (United States)

The powerful greenhouse effect on Venus exists because pressure-broadened CO2 absorption bands, interlaced with water absorption features, effectively block most of the upwelling thermal radiation coming from the surface. The sulfuric acid clouds and small amounts of SO2, OCS, CO, HCl and HF are responsible for some absorption of radiation at wavelengths greater than 2 ? m. In particular, these constituents of Venus' atmosphere absorb thermal radiation in a crucial part of the spectrum -- the 2.1 to 2.6 ? m range where the CO2-H2O thermal absorption conspiracy is weak. Much of the radiation on the short-wavelength side of Venus' surface blackbody curve (which has a peak at 4 ? m), leaves the planet through this window. Variations in the abundance of the trace atmospheric species have a large effect on the efficacy of this window, both directly through their infrared absorption, and indirectly through their effect on clouds. Increased atmospheric absorption, say through an increase in atmospheric water abundance, can heat the surface. However, as the surface of Venus heats up, the peak of its Planck function moves towards the 2.1 to 2.6 ? m window, allowing more direct thermal radiation loss to space. This high temperature shift of radiative loss into the window will act as a thermostat. For moderate perturbations in atmospheric trace species therefore, such as those expected from volcanism or large impacts, there is a limit to how hot the surface of Venus can get. Using a one-dimensional, non-gray coupled cloud/radiative transfer model, we will show what the theoretical limits on the surface temperature of Venus are. We will discuss the fairly broad constraints on these conclusions, and make some general predictions for terrestrial planets with CO2-H2O atmospheres in other solar systems. These results may be relevant for models of tectonic and convective history of Venus and other planets.

Bullock, Mark A.; Grinspoon, David H.

2001-11-01

149

Scientific Balloons for Venus Exploration  

Science.gov (United States)

Almost 30 years ago, two balloons were successfully deployed into the atmosphere of Venus as an element of the VeGa – Venus Halley mission conducted by the Soviet Union. As interest in further Venus exploration grows among the established planetary exploration agencies – in Europe, Japan, Russia and the United States, use of balloons is emerging as an essential part of that investigative program. Venus balloons have been proposed in NASA’s Discovery program and ESA’s cosmic vision program and are a key element in NASA’s strategic plan for Venus exploration. At JPL, the focus for the last decade has been on the development of a 7m diameter superpressure pressure(twice that of VeGa) capable of carrying a 100 kg payload (14 times that of VeGA balloons), operating for more than 30 days (15 times the 2 day flight duration of the VeGa balloons) and transmitting up to 20 Mbit of data (300 times that of VeGa balloons). This new generation of balloons must tolerate day night transitions on Venus as well as extended exposure to the sulfuric acid environment. These constant altitude balloons operating at an altitude of about 55 km on Venus where temperatures are benign can also deploy sondes to sound the atmosphere beneath the probe and deliver deep sondes equipped to survive and operate down to the surface. The technology for these balloons is now maturing rapidly and we are now looking forward to the prospects for altitude control balloons that can cycle repeatedly through the Venus cloud region. One concept, which has been used for tropospheric profiling in Antarctica, is the pumped-helium balloon, with heritage to the anchor balloon, and would be best adapted for flight above the 55 km level. Phase change balloons, which use the atmosphere as a heat engine, can be used to investigate the lower cloud region down to 30 km. Progress in components for high temperature operation may also enable investigation of the deep atmosphere of Venus with metal-based balloons.

Cutts, James; Yavrouian, Andre; Nott, Julian; Baines, Kevin; Limaye, Sanjay; Wilson, Colin; Kerzhanovich, Viktor; Voss, Paul; Hall, Jeffery

150

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

151

Venera-D -the future Russian mission to Venus  

Science.gov (United States)

Venus was actively studied by Soviet and US mission in 60-80-th years of the last century. The investigations carried out both from the orbit and in situ were highly successful. After a 15-years break in space research of Venus, the ESA Venus Express mission, launched in 2005, successfully continues its work on orbit around Venus. In 2010 the launch of the Japanese Climate Orbiter (Planeta-C) mission is planned. However, many questions concerning the structure, and evolu-tions of planet Venus, which are the key questions of comparative planetology, very essential for understanding the evolution of the terrestrial climate, cannot be solved by observations from an orbit. Now in Russia the new investigation phase of Venus begins: the mission Venera-D is included in the Russian Federal Space Program to be launched in 2016. This mission includes the lander, balloons, and the orbiter. The long living balloons are planned to be deployed at different heights, in the clouds and under the clouds. Scientific goals of the mission include: -investigation of structure, chemical composition of the atmosphere, including noble gases abundance and isotopic ratio, structure and chemistry of the clouds; -study of dynamics of the atmosphere, nature of the superrotation, radiative balance, nature of an enormous greenhouse effect; -study of structure, mineralogy and geochemistry of the surface, search for seismic and volcanic activity, the lightening, interaction of the atmosphere and the surface; -investigation of the upper atmosphere, ionosphere, magnetosphere, and the escape rate; -study of the evolution of the atmosphere and the surface of Venus. The complex of experiments on the orbiter includes, among the others, several spectrometers in the spectral range from UV to MW, the mapping spectrometers and the plasma package. On the lander there are instruments to work during the descent, and on the surface: gas-chromatograph, PTW (meteo), nephelometer and the particle sizes spectrometer, optical package, active gamma-spectrometer, TV-complex, which includes panoramic, high resolution and descending cameras.. On the balloon which has to work near the lower boundary of clouds, the devices will be installed to study the lower atmosphere and to get the surface images with high resolution at 1 mkm. Successful realization of the project Venera-D will allow to solve the important scientific problems of comparative planetology. In particular it will help to understand why do Venus and the Earth (sister-planets), similar in many aspects, being formed at similar conditions in the protoplanet nebula, evolve by such a different way.

Zasova, Ludmila; Zelenyi, Lev; Korablev, Oleg; Sanko, N. F.; Khartov, Victor V.; Vorontsov, Victor A.; Basilevsky, A. T.; Pichkhadze, Konstantin M.; Elkin, Konstantin S.; Voron, Victor V.

152

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

153

Optimizing Aerobot Exploration of Venus  

Science.gov (United States)

Venus Flyer Robot (VFR) is an aerobot; an autonomous balloon probe designed for remote exploration of Earth's sister planet in 2003. VFR's simple navigation and control system permits travel to virtually any location on Venus, but it can survive for only a limited duration in the harsh Venusian environment. To help address this limitation, we develop: (1) a global circulation model that captures the most important characteristics of the Venusian atmosphere; (2) a simple aerobot model that captures thermal restrictions faced by VFR at Venus; and (3) one exact and two heuristic algorithms that, using abstractions (1) and (2), construct routes making the best use of VFR's limited lifetime. We demonstrate this modeling by planning several small example missions and a prototypical mission that explores numerous interesting sites recently documented in the plane tary geology literature.

Ford, Kevin S.

1997-03-01

154

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

155

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

156

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

157

Long-Lived Venus Lander Conceptual Design: How To Keep It Cool  

Science.gov (United States)

Surprisingly little is known about Venus, our neighboring sister planet in the solar system, due to the challenges of operating in its extremely hot, corrosive, and dense environment. For example, after over two dozen missions to the planet, the longest-lived lander was the Soviet Venera 13, and it only survived two hours on the surface. Several conceptual Venus mission studies have been formulated in the past two decades proposing lander architectures that potentially extend lander lifetime. Most recently, the Venus Science and Technology Definition Team (STDT) was commissioned by NASA to study a Venus Flagship Mission potentially launching in the 2020- 2025 time-frame; the reference lander of this study is designed to survive for only a few hours more than Venera 13 launched back in 1981! Since Cytherean mission planners lack a viable approach to a long-lived surface architecture, specific scientific objectives outlined in the National Science Foundation Decadal Survey and Venus Exploration Advisory Group final report cannot be completed. These include: mapping the mineralogy and composition of the surface on a planetary scale determining the age of various rock samples on Venus, searching for evidence of changes in interior dynamics (seismometry) and its impact on climate and many other key observations that benefit with time scales of at least a full Venus day (Le. daylight/night cycle). This report reviews those studies and recommends a hybrid lander architecture that can survive for at least one Venus day (243 Earth days) by incorporating selective Stirling multi-stage active cooling and hybrid thermoacoustic power.

Dyson, Ridger W.; Schmitz, Paul C.; Penswick, L. Barry; Bruder, Geoffrey A.

2009-01-01

158

Venus - Lakshmi Region  

Science.gov (United States)

This Magellan image is centered at 55 degrees north latitude, 348.5 degrees longitude, in the eastern Lakshmi region of Venus. This image, which is of an area 300 kilometers (180 miles) in width and 230 kilometers (138 miles) in length, is a mosaic of orbits 458 through 484. The image shows a relatively flat plains region composed of many lava flows. The dark flows mostly likely represent smooth lava flows similar to 'pahoehoe' flows on Earth while the brighter lava flows are rougher flows similar to 'aa' flows on Earth. (The terms 'pahoehoe' and 'aa' refer to textures of lava with pahoehoe a smooth or ropey surface, and aa a rough, clinkery texture). The rougher flows are brighter because the rough surface returns more energy to the radar than the smooth flows. Situated on top of the lava flows are three dark splotches. Because of the thick Venusian atmosphere, the small impactors break up before they reached the surface. Only the fragments from the broken up impactor are deposited on the surface and these fragments produce the dark splotches in this image. The splotch at the far right (east) has a crater centered in it, indicating that the impactor was not completely destroyed during its journey through the atmosphere. The dark splotches in the center and to the far left in this image each represent an impactor that was broken up into small fragments that did not penetrate the surface to produce a crater. The dark splotch at the left has been modified by the wind. A southwest northeast wind flow has moved some of the debris making up the splotch to the northeast where it has piled up against some small ridges.

1991-01-01

159

Ranging to the Venus Atmosphere With the Mercury Laser Altimeter  

Science.gov (United States)

During the flyby of Venus on 05 June 2007 by the MESSENGER spacecraft the Mercury Laser Altimeter (MLA) was operated for approximately 30 minutes, including approximately 8 minutes within 800 km of the planet's surface. With almost no expectation of receiving a return from the Venus surface the altimeter was targeted at the Venus atmosphere between 40 and 80 km above the surface, the altitude range of thickest clouds. Previous observations of the Venus atmosphere from nephelometry and particle size spectrometry indicated a structure of the clouds consisting of a haze that increases in opacity with depth, without discrete cloud tops. An objective of the MLA experiment was to attempt to identify heretofore undetected layering within the upper part of the Venus cloud deck. Although the MLA is a ranging device and not an atmospheric lidar, an instrument of similar design on the Mars Global Surveyor (MGS) spacecraft had obtained clear returns from layers within the Martian atmosphere at altitudes up to several tens of kilometers above the surface. At Venus, the MLA operated successfully in science ranging mode for the first time; the instrument recorded photon counts throughout the period of operation. We analyzed in detail a period of approximately 3 minutes when the spacecraft was closest to the planet at less than 400 km and when returns from the atmosphere would be most likely. When the backscattered signal is weak or non-existent, the altimeter dark noise dominates the detector count. Returns from cloud layers, if they exist, would appear as increased detector counts at the altitude of the cloud layer on top of the detector noise. The altimeter returns indicate a significant noise component throughout the 8-minute period of operation, including the 3 minutes bounding closest approach. Analysis of the data by three different methods suggest an increase in returns in two regions between 50 and 70 km altitude range, which, on the basis of statistical analysis, could be attributable to backscattered photons from the Venus atmosphere at a weak level of statistical significance. However, the experiment showed no evidence for discrete layering within the primary cloud deck.

Smith, D. E.; Zuber, M. T.; Neumann, G. A.; Sun, X.; Cavanaugh, J. F.; McGarry, J.; Solomon, S. C.

2007-12-01

160

Simulation of Venus Atmosphere Dynamics With an Earth Climate GCM  

Science.gov (United States)

We describe the results of initial simulations of the Venusian atmosphere, using the Community Atmosphere Model (CAM). The CAM model is a descendant of the NCAR Community Climate Model, and is defined as one of two "high-end" models designated by the US Climate Change Science Program for basic research. It may also be the most widely used 3D climate model in the US. CAM has grown substantially in complexity and Earth-specificity since the original version was released in 1983, and many of these Earth based physics parameterizations need to be adjusted to simulate the Venus atmosphere. Other groups are adapting CAM to simulate the atmospheres of Mars and Titan, thereby promising CAM simulation for all four terrestrial planets known to have substantial atmospheres. Studying these worlds together will provide calibration of Earth-centric studies of climate changes like global warming. It will also provide context for future searches for Earth-like planets orbiting other stars. In this work we will focus on Venus. The Venus atmosphere represents an extreme environment, strongly influenced by the greenhouse effect, and studying the Venus atmosphere may therefore be relevant to the possible future direction of the Earth's climate. The dynamical processes which occur in the Venusian atmosphere are not well understood, including the cause of the strong superrotation of the atmosphere, in which the planetary surface rotates with a period of around 243 days, but the atmosphere near the cloud tops has a rotational period of only around 4 days. We show the results of initial simulations of the dynamics of the Venus atmosphere, using a version of the CAM model with most of the Earth related processes, such as the cloud physics, removed. A simplified form of heating has been applied, similar to the thermal forcing approach used recently by other authors. We investigate the sensitivity of the model results to changes in the physics parameterizations we have used, including changes in the friction at the upper and lower boundaries, in the heating function, and in dissipation mechanisms, as well as the effects of introducing topography. We analyse the model results to determine the nature of the dynamical processes that produce the characteristics of the Venus atmosphere. We are implementing a self consistent model of the thermodynamic radiative forcing by a detailed calculation of the radiative fluxes at each level in the CAM model, in order to produce a more realistic representation of the thermal forcing which helps to generate the observed structure of the Venusian atmosphere. The radiation model is based on the Laboratoire de Meteorologie Dynamique Venus GCM, including parameterizations of the radiation at short and infrared wavelengths.

Parish, H. F.; Schubert, G.; Covey, C. C.; Grossman, A.

2008-12-01

 
 
 
 
161

Earth/Venus Rotation Movie  

Science.gov (United States)

This movie shows Venus and Earth as they rotate. The images are superimposed on each other so that differences in rotation speed and tilt of axes can be seen. Links to documents describing the physical properties and characteristics of the two planets are provided.

2005-09-01

162

Phlogopite Decomposition, Water, and Venus  

Science.gov (United States)

Venus is a hot and dry planet with a surface temperature of 660 to 740 K and 30 parts per million by volume (ppmv) water vapor in its lower atmosphere. In contrast Earth has an average surface temperature of 288 K and 1-4% water vapor in its troposphere. The hot and dry conditions on Venus led many to speculate that hydrous minerals on the surface of Venus would not be there today even though they might have formed in a potentially wetter past. Thermodynamic calculations predict that many hydrous minerals are unstable under current Venusian conditions. Thermodynamics predicts whether a particular mineral is stable or not, but we need experimental data on the decomposition rate of hydrous minerals to determine if they survive on Venus today. Previously, we determined the decomposition rate of the amphibole tremolite, and found that it could exist for billions of years at current surface conditions. Here, we present our initial results on the decomposition of phlogopite mica, another common hydrous mineral on Earth.

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

2005-01-01

163

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.

164

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

165

Venus Data Analysis Program: Directory of Research Projects (1993-1994)  

Science.gov (United States)

This directory provides information about the scientific investigations funded by the NASA Venus Data Analysis Program (VDAP) during fiscal year 1993. The VDAP Directory consists of summary sheets from the proposals that were selected by NASA for funding in FY 93. Each summary sheet indicates the title, principal investigator, institution of the investigation, and information related to the objectives of the research activities proposed for FY 93. The objective of the VDAP Program is to advance our understanding of the nature and evolution of Venus. VDAP supports scientific investigation using data obtained from the Magellan, Pioneer Venus, and other Venus missions, as well as earth-based observations that contribute to understanding the physical and evolutionary properties of Venus. The program intends to enhance the scientific return from these missions by broadening the participation in the analysis of Venus data. Categories of research funded by VDAP are atmosphere, ionosphere, geology, geophysics, and mapping. The directory is intended to provide the science community with an overview of the research projects supported by this program. Research activities identified in this directory were selected for funding in FY 93 on the basis of scientific peer review conducted by the VDAP Review Panel.

1994-01-01

166

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

167

BOOK REVIEW: June 8, 2004: Venus in Transit  

Science.gov (United States)

A transit of Venus is a relatively rare astronomical event in which the silhouette of Venus is seen to move across the face of the Sun. The phenomenon typically lasts several hours, during which Venus is seen as a small dot against the half-degree angular diameter of the solar disc. The last transit of Venus occurred in 1882; the next will be 8 June 2004. Such transits were once of great importance in astronomy. By observing a transit simultaneously from well separated points on the Earth's surface, astronomers were able to measure, with some degree of accuracy, the crucially important separation of the Earth and the Sun. Knowing this enabled them to convert the relative spacings of the planets indicated by Kepler's laws into absolute interplanetary distances expressed in miles or kilometres. Eli Maor's book presents the general reader with a full account of Venusian transits that covers the history of their observation as well as their significance and the reasons for their rarity. The book is a light and enjoyable read that opens well with an imaginative description of observing the 2004 transit from the hills outside Jerusalem. Following an account of Kepler's prediction of a transit of Mercury in 1631 and its observation by Gassendi, the book moves on to describe the transit of Venus in 1639, giving particular emphasis to the prescient work of Jeremiah Horrocks, the extraordinary young English curate and astronomer who died just two years later at the age of 21. The story, however, really takes off with Edmond Halley's realization, in 1677, that transits of Venus might provide the key to determining distances within the solar system. The details of Halley's method are confined to an appendix, but the central chapters of the book detail the increasingly elaborate efforts that astronomers made to observe transits of Venus up to the time of the 1882 transit, when, due to the impact of new photographic methods, interest in transit observations was waning. By that time the distance to the Sun was known to be about 93 000 000 miles and observations of Mars or the asteroids seemed to offer a better prospect of improved accuracy than further observations of Venus. The story is rounded off by a chapter that describes spurious transit observations (such as that of Vulcan, a planet that was supposed to orbit closer to the Sun than Mercury) and a chapter concerning transits of the Earth seen from Mars, Jupiter and the other outer planets. Maor, who is also the author ofe: The Story of a Number, and various other books, writes clearly and well, but Venus in Transit is not uniformly interesting throughout. The early chapters are generally very good, as is the account of Captain James Cook and theEndeavour's voyage to observe the 1761 transit. But after that I felt my interest flagging somewhat, just as the astronomers of the time seemed to find their own interest diminishing. The closing chapters helped to re-engage my interest, but I did feel that the discussion of the 19th century transits was rather perfunctory and that it would have benefited from more space. Still, these are minor criticisms of a book that I am personally very glad to have read. Venus in Transit will obviously appeal most to those with an interest in astronomy, particularly in its historical aspects. But there is also much that physicists can enjoy in the book and I can easily imagine it as a useful though non-essential addition to many school and college libraries. Robert Lambourne

Maor, Eli

2000-09-01

168

Nuclear Electric Propulsion Application: RASC Mission Robotic Exploration of Venus  

Science.gov (United States)

The following paper documents the mission and systems analysis portion of a study in which Nuclear Electric Propulsion (NEP) is used as the in-space transportation system to send a series of robotic rovers and atmospheric science airplanes to Venus in the 2020 to 2030 timeframe. As part of the NASA RASC (Revolutionary Aerospace Systems Concepts) program, this mission analysis is meant to identify future technologies and their application to far reaching NASA missions. The NEP systems and mission analysis is based largely on current technology state of the art assumptions. This study looks specifically at the performance of the NEP transfer stage when sending a series of different payload package point design options to Venus orbit.

McGuire, Melissa L.; Borowski, Stanley K.; Packard, Thomas W.

2004-01-01

169

Russia's contribution to regional geologic mapping of Venus  

Science.gov (United States)

Geologic maps in Magellan C1-format were produced by six geologists and three cartographer in Russia during 1992. More sheets are in progress. The work is coordinated by Vernadsky Institute. The Magellan SRR images in form of C1-format photomaps were used as a base for geologic-geomorphic regional mapping of Venus at approximately 1:8,000,000 scale. This work took place in Russia at Vernadsky Institute and at the Department of Geology, Lomonosov Moscow University. The aim is to produce a preliminary geologic survey of Venus with the new high resolution images obtained by Magellan. It took place at the cartographic division, Laboratory of Comparative Planetology and Meteoritics, Vernadsky Institute, Russsia's Academy of Sciences.

Burba, G. A.; Bobina, N. N.; Shashkina, V. P.

1993-01-01

170

Obliquity Evolution of an Early Venus  

Science.gov (United States)

Stark differences in both atmospheric mass and rotation are apparent between the present-day Earth and neighboring Venus. These planets may have been more similar 4 Gyr ago when most of the carbon within Venus may have been in solid form, implying a low-mass atmosphere. As a result, Venus's rotation rate could have been much faster than at present due to the smaller cumulative effects of solid-body and atmospheric tides. We investigate how the obliquity of a hypothetical rapidly-rotating Early Venus would have evolved as compared to a Moonless Earth. As with our previous investigation [Lissauer, Barnes, & Chambers 2012], slow prograde rotation of our hypothesized Early Venus generally leads to larger variations in obliquity than does retrograde rotation. However, the variability of obliquity for retrograde rotations differs from the Moonless Earth and can change with the initial spin period. The implications for early habitability of extrasolar Venus analogs will also be discussed.

Quarles, Billy L.; Barnes, Jason; Lissauer, Jack J.; Chambers, John

2014-11-01

171

Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop  

Science.gov (United States)

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.

1989-01-01

172

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

173

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

174

The ionosphere and airglow of Venus - Prospects for Pioneer Venus  

Science.gov (United States)

The paper presents model calculations for the Cytherean nighttime and daytime ionosphere. It is shown how some of the proposed mechanisms can be tested with the aid of the Pioneer Venus observations scheduled for December 1978. Theoretical calculations of the energetics of the Cytherean ionosphere are performed, and it is concluded that the Project Venus measurements will find elevated ion and electron temperatures, resulting primarily from energy fluxes associated in some manner with the solar wind. According to this model, the energy flux will act directly on the ion gas. Ultraviolet dayglow intensities were calculated, and it is anticipated that hundreds of kR's of CO2-related emission features such as the CO Cameron bands will be observed. Nightside ionosphere calculations were made assuming the precipitation of energetic electrons as an ionization source, and the intensities of some of the resulting emission features are calculated.

Cravens, T. E.; Nagy, A. F.; Chen, R. H.; Stewart, A. I.

1978-01-01

175

Similarities and Differences in the Nightglows of Venus, Earth, and Mars  

Science.gov (United States)

Although the atmospheres of Earth and its sister planets Venus and Mars are quite different, their nightglows have several features in common. These similarities are caused by the fact that all three planets contain N2 in their atmospheres, and all contain a molecule that photodissociates to give oxygen atoms, i.e. O2 in the terrestrial case, and CO2 for Venus and Mars. As a result, we find for example that two-body N + O recombination occurs on all three planets, as we know from terrestrial rocket/satellite observations, the Pioneer Venus results, and the recent observations from the Mars Express mission. The very different rotation periods of Earth and Mars on the one hand and Venus on the other presents no impediment to the generation of these emissions. The long-studied terrestrial 557.7 nm green line is now known to have its counterpart at Venus, with every expectation of observing it at Mars when the visible nightglow is finally studied. The presence of water in the terrestrial atmosphere and that of Mars differentiates them from Venus, and we do not yet know if the strong OH Meinel band emissions of the terrestrial mesosphere are duplicated at Mars, although the necessary chemical ingredients, H-atoms and ozone, are present. Comparative studies of these atmospheres lead to insights that will ultimately be useful as we start to probe the atmospheres of extrasolar planets.

Slanger, T. G.

2005-12-01

176

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

177

Investigating gravity waves evidences in the Venus upper atmosphere  

Science.gov (United States)

We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

2014-05-01

178

Tectonism on Venus: A review  

International Nuclear Information System (INIS)

Venus is more similar to Earth than to any other planet. It has elevated regions associated with marginal fold and thrust belts, fracture zones that extend tens of thousands of kilometers, crustal swells and shields that are hundreds of kilometers in diameter and 1 to 2 km high, and sublinear accumulations of volcanic cones and domes that stretch for thousands of kilometers across the plains. The Venusian surface is, however, distinctly different from Earth's in that: (1) its elevated terrains cannot be distinguished from its low plains on a hypsometric curve; (2) trenches have not been found plainsward of the marginal belts; (3) fracture zones bear no resemblance to mid-oceanic ridges; and (4) some features, such as the ridge-belt zone near 210 deg E, seem to have no terrestrial analog. Various theories about tectonism on Venus and Earth of other authors are reviewed

179

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

180

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.

 
 
 
 
181

What can Venus and Mars tell us about Sun's direct influence on Earth's Atmosphere?  

Science.gov (United States)

Venus and Mars, Earth's sister planets, are similar but also very different compared to the Earth. The mass-density and surface properties bear certain commonality, but the atmospheric composition, the temperature and the surface pressure on Venus and Mars are very different compared to the Earth. Venus and Mars are arid planets with atmospheres dominated by a greenhouse gas CO2 (>95%), while the Earth's atmosphere is dominated by molecular Nitrogen and Oxygen. The main greenhouse gas in the Earth's atmosphere is water, with a minor contribution of CO2. Bearing these differences in mind, what can we possibly learn from Mars and Venus about the solar influence on the Earth's atmosphere? The answer can be found in how solar forcing affects a planetary atmosphere, more specifically the impact of solar EUV and solar wind variability on a planetary atmosphere. The lack of a strong intrinsic magnetic field on Mars and Venus means that solar wind forcing has a global effect on the upper atmosphere of Mars and Venus. Conversely, the Earth's intrinsic dipole magnetic field alleviates the forcing to narrow zones near the magnetic poles. Results obtained from Venus and Mars orbiters imply that solar wind forcing leads to a long-term gradual removal of atmospheric constituents. New information from ESAs Mars Express and Venus Express orbiters suggests short-term solar wind forcing effects as well, especially in the polar region. While the impact of solar forcing on the "unprotected" planets Venus and Mars seems conceivable, one might argue that similar forcing effects are unlikely on a magnetically protected planet. Short-term "space weather" effects on the Earth's tropospheric circulatory system have been reported in the past, but the effects have usually been discarded using arguments that such a weak forcing is unlikely to have any implications whatsoever on the Earth's weather system. However, considering the forcing observed in e.g. the Venus polar region, solar forcing may have a significant effect on the Earth's polar region upper atmosphere as well.

Lundin, R.

2010-09-01

182

Recent progress on the superconducting ion source VENUS.  

Science.gov (United States)

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&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?A of Bi(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. PMID:22380158

Benitez, J Y; Franzen, K Y; Hodgkinson, A; Loew, T; Lyneis, C M; Phair, L; Saba, J; Strohmeier, M; Tarvainen, O

2012-02-01

183

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

184

Volcanism on Venus: a connecting link  

International Nuclear Information System (INIS)

On the basis of data obtained during recent investigations of Venus the suggestion is made that the presence of electrical discharges in the atmosphere close to the surface, the variable density of the submicron haze and the peculiarity of cloud microphysics can be jointly explained in the frame of the hypothesis about volcanic erruptions on the surface of Venus

185

Comments on the tectonism of Venus  

International Nuclear Information System (INIS)

Preliminary tectonic mapping of Venus from Venera 15/16 images shows unquestionable evidence of at least limited horizontal tectonism. The majority of tectonic features on Venus have no relation to topography. In fact, many axes of disruption interconnect, and cross sharp topographic boundaries at large angles, thereby discounting gravity as the driving force. Compressional zones (CZ's), unlike Extensional zones (EZ's), tend to be discontinuous, and, whereas EZ's cross tectonic and topographic boundaries at various angles, many CZ's on Venus are subparallel to these boundaries. Strike-like faulting is curiously lacking from the mapping, possible due to the steep incidence angle of the radar, which is far from optimal for detecting faults of small throw. A chronology of horizontal crustal movements, and hence the analysis of Venus' thermal development, is large dependent on understanding the crater form features. Regardless of their uncertain origin, the craters still could hold the answer to whether, and to what extent, crustal shuffling is occurring on Venus

186

Exploring the veiled planet. [Venus observations  

Science.gov (United States)

An overview of data obtained from various experiments which characterize geological features and atmospheric properties of Venus is presented. Data from the two Pioneer sounder probes (one located at Venus's equator and the other near the north pole) exhibit a reversal in the equator-to-pole temperature patterns at 60 km altitude which suggests that two circulation cells exist within the atmospheric region. However, the atmospheric temperature and pressure beneath the clouds are found to be nearly identical everywhere on Venus and both temperature and pressure conditions at the surface are lower than first expected. The identification of sulphur dioxide clouds which appear to coincide with Venus's characteristic global patterns of C- and Y-shaped dark markings support the hypothesis of a regular pattern of planet spanning breaks in the upper cloud layer. Explanations of a Venus sulphur cycle and of observed magnetic field structures are suggested

1980-01-01

187

Photochemical modelling of Venus clouds using Pioneer Venus data  

Science.gov (United States)

In order to understand the evolution of water on Venus, we must know the hydrogen escape flux as a function of the tropospheric water abundance. We have studied the connection between total stratospheric hydrogen and exobase hydrogen available to non-thermal escape processes and examined the details of the photochemical trap for water at the Venus cloud tops. Our immediate goal is to calculate the stratospheric water abundance as a function of the tropospheric water abundance. Photochemical production of H2SO4 acts as a sink for both water and sulfur and is capable of keeping stratospheric abundances low if a proper balance exists between the tropospheric abundances. If production of H2SO4 were the only sink for H2O and SO2, the excess in tropospheric abundance of one over the other would reach the stratosphere, and the functional dependence of stratospheric H2O on tropospheric H2O would be linear near the present state. On Venus, however, sulfuric acid condenses at cloud top temperatures and the resulting aerosols can absorb additional water of hydration. This complicates the water budget, increasing the efficiency of sulfur as a sink for water. We have investigated the balance between tropospheric H2O and SO2 and how delicate the balance is. Our major conclusions from this work are the following: (1) H2O and SO2 are mutually limiting if proper tropospheric balance is maintained; (2) changes in tropospheric abundances on the order of 5 ppm are significant; and (3) changes in mixing rates near the cloud tops can cause dramatic changes in SO2 without causing dramatic changes in H2O.

Mcelroy, Michael B.

1985-01-01

188

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

189

Outgassing history of Venus and the absence of water on Venus  

Science.gov (United States)

Similarities in the size and mean density of Earth and Venus encourage the use of Earth-analogue models for the evolution of Venus. However, the amount of water in the present Venus atmosphere is miniscule compared to Earth's oceans. The 'missing' water is thus one of the most significant problems related to the origin and evolution of Venus. Other researchers proposed that Venus accreted with less water, but this was challenged. The high D/H ratio in Venus' atmosphere is consistent with an earlier water mass more than 100 times higher than at present conditions and is often cited to support a 'wet' Venus, but this amounts to only 0.01 to 0.1 percent of the water in terrestrial oceans and the high D/H ratio on Venus could easily reflect cometary injection. Nevertheless, many authors begin with the premise that Venus once had an oceanlike water mass on its surface, and investigate the many possible mechanisms that might account for its loss. In this paper we propose that Venus degassed to lower degree than the Earth and never had an oceanlike surface water mass.

Zhang, Youxue; Zindler, Alan

1992-01-01

190

SOIR/VEX observations of thermospheric CO on Venus  

Science.gov (United States)

The wavelength range probed by the SOIR instrument on board Venus Express - 2.2 to 4.4 µm - allows a detailed chemical inventory of the Venus atmosphere. In particular CO is measured together with CO2 allowing the derivation of their vertical density profiles, which finally result in CO VMR profiles. Moreover, temperature and total density profiles are deduced from the CO2 density 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 between 100 and 500 m), and is poorer at southern latitudes (resolution between 1 and 2.5 km). The typical vertical extent of the CO vertical profiles ranges from 70 to 120 km (for CO2 : from 70 to 170 km), with variations from orbit to orbit, encompassing thus the mesosphere and the lower thermosphere of the planet. The Venus atmospheric region probed by the SOIR instrument is very special as it acts as a transition region between two distinct dynamical regimes characterized by different flow patterns: the zonal retrograde flow below 70 km and the subsolar to antisolar circulation above 100 km. The study of CO, being mainly produced through the photodissociation of CO2 at high altitudes by solar ultraviolet radiation, can lead to significant information on the dynamics taking place in this region. Results from SOIR observations of CO, together with CO2 and temperature will be presented and discussed. We will report and analyze short and long term time variations. The latitudinal dependency will also be investigated.

Carine Vandaele, Ann; Wilquet, Valérie; Drummond, Rachel; Mahieux, Arnaud; Robert, Séverine; Bertaux, Jean-Loup

2013-04-01

191

Transmission spectrum of Venus as a transiting exoplanet  

Science.gov (United States)

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 ?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 ?m by Mie extinction (~5 ppm at 0.8 ?m) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet. Appendix A is available in electronic form at http://www.aanda.orgFull Table A.1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/L2

Ehrenreich, D.; Vidal-Madjar, A.; Widemann, T.; Gronoff, G.; Tanga, P.; Barthélemy, M.; Lilensten, J.; Lecavelier Des Etangs, A.; Arnold, L.

2012-01-01

192

Announcing the Venus Transit 2004 (VT-2004) Programme  

Science.gov (United States)

Rare Celestial Event to be Observed by Millions Summary On June 8, 2004, Venus - the Earth's sister planet - will pass in front of the Sun. This event, a 'transit', is extremely rare - the last one occurred in 1882, 122 years ago. Easily observable in Europe, Asia, Africa and Australia, it is likely to attract the attention of millions of people on these continents and, indeed, all over the world. On this important occasion, the European Southern Observatory (ESO) has joined forces 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 to establish the Venus Transit 2004 (VT-2004) public education programme. It is supported by the European Commission in the framework of the European Science and Technology Week and takes advantage of this extraordinary celestial event to expose the public - in a well-considered, interactive and exciting way - to a number of fundamental issues at the crucial interface between society and basic science. VT-2004 has several components, including an instructive and comprehensive website (www.vt-2004.org). It is directed towards the wide public in general and the media, school students and their teachers, as well as amateur astronomers in particular. It invites all interested persons to participate actively in the intercontinental VT-2004 Observing Campaign (that reenacts historical Venus Transit observations) and the VT-2004 Video Contest. During the VT-2004 Final Event in November, the winners of the Video Contest will be chosen by an international jury. This meeting will also serve to discuss the project and its impact. The outcome of this rare celestial event and the overall experience from this unique public education project will clearly be of very wide interest, not just in the field of astronomy.

2004-02-01

193

Venus' thermospheric temperature field using a refraction model at terminator : comparison with 2012 transit observations using SDO/HMI, VEx/SPICAV/SOIR and NSO/DST/FIRS  

Science.gov (United States)

The transit of Venus in June 2012 provided a unique case study of the Venus' atmosphere transiting in front of the Sun, while at the same time ESA's Venus Express orbiter observed the evening terminator at solar ingress and solar egress.We report on mesospheric temperature at Venus' morning terminator using SDO/HMI aureole photometry and comparison with Venus Express. Close to ingress and egress phases, we have shown that the aureole photometry reflects the local density scale height and the altitude of the refracting layer (Tanga et al. 2012). The lightcurve of each spatially resolved aureole element is fit to a two-parameter model to constrain the meridional temperature gradient at terminator. Our measurements are in agreement with the VEx/SOIR temperatures obtained during orbit 2238 at evening terminator during solar ingress (46.75N - LST = 6.075PM) and solar egress (31.30N - LST = 6.047PM) captured from the Venus Express orbiter at the time Venus transited the Sun.We also performed spectroscopy and polarimetry during the transit of Venus focusing on extracting signatures of CO2 absorption. Observations were taken during the first half of the transit using the Facility InfraRed Spectropolarimeter (FIRS) on the Dunn Solar Telescope (DST). Although the predicted CO2 transmission spectrum of Venus was not particularly strong at 1565 nm, this region of the H-band often used in magnetic field studies of the Sun's photosphere provides a particularly flat solar continuum with few atmospheric lines. Sun-subtracted Venus limb observations show intensity distribution of vibrational CO2 bands 221 2v+2v2+v3 at 1.571?m and 141 v1+4v2+v3 at 1.606?m.

Widemann, Thomas; Jaeggli, Sarah; Reardon, Kevin; Tanga, Paolo; Père, Christophe; Pasachoff, Jay M.; Vandaele, Ann Carine; Wilquet, Valerie; Mahieux, Arnaud; Wilson, Colin

2014-11-01

194

Science Express: Out-of-Home-Media to Communicate Climate Change (Invited)  

Science.gov (United States)

Science Express is an initiative to explore, develop, and test various approaches to using Out-of-Home-Media (OHM) to engage adults riding mass transit. To date, three projects represent this work: 1) Carbon Smarts Conference, 2) Cool Science, and 3) ScienceToGo.org. While the aim of each project is different, together they serve an immediate need to understand how OHM can be leveraged as an informal science learning medium. Using Climate Change as the content focus, each project is a variation on the theme of understanding mass transit as a form of mobile classroom for riders. The basic idea behind these initiatives is to engage individuals who do not necessarily read the science magazines, listen to science radio shows, or watch science programming on television. Science Express is about bringing the science learning opportunity to the audience during their daily routines. Mass Transit provides an ideal opportunity for engaging the disengaged in science learning since they represent a ';captive' audience while waiting at the bus stop, standing on the platform, riding inside the bus or train. These ';downtimes' present informal science educators with the opportunity to foster some science learning. With the advent of smartphone technology and its explosion in popularity among consumers, OHM is poised to offer riders a new kind of real time learning experience. The Science Express projects aim to understand the strengths and weaknesses of this new model for informal science learning so as to refine and improve its effectiveness at achieving desired goals. While the Science Express model for informal science learning could be used to foster understanding about any relevant scientific content, the research team chose to use Climate Change as the focus. Climate Change seemed like an obvious because of its timeliness, complexity, robust scientific foundation, and presence in popular media. Nearly all our riders have heard of 'Climate Change' or 'Global Warming', but a much smaller percentage actually understand the underlying science. In addition, riders appear to be very curious and want to know more about these issues.

Lustick, D. S.; Lohmeier, J.; Chen, R.

2013-12-01

195

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 kinetic temperature of the O+ component is estimated as 105--106 K in order of magnitude

196

Venus Transit 2012: the expeditions to Svalbard, Norway, and Canberra, Australia  

Science.gov (United States)

A transit of Venus in front of the solar disk as seen from Earth is a rare astronomical event which comes in pairs separated by approximately 8 years and occurs only about every 105 years. Although its historic scientific importance, e.g. to measure the distances in the solar system or to analyze the Venus atmosphere, has diminished since humanity roams our solar system with robotic spacecrafts, a Venus Transit remains a spectacular astronomical event, worth observing. Unfortunately, this time the transit occurs during the night in Europe, from about midnight to seven o'clock in the morning, CEST. However, some astronomy enthusiasts working at ESA's European Space Astronomy Centre (ESAC) in Madrid, Spain, will organize a campaign to observe the Venus Transit 2012 from two separate locations: Svalbard in Norway, and Canberra in Australia. The expeditions are done in the framework of ESA and its educational project CESAR (Cooperation through Education in Science and Astronomy Research). Both teams will be equipped with a twin set of telescopes, each comprising a 90mm solar H_alpha (656 nm wavelength) telescope, and a white light 102mm telescope. H-alpha and white light images will be simultaneously transmitted live during the whole Venus Transit, through a dedicated public web page. This talk will summarize the two expeditions, its preparations and its results.

Pérez-Ayúcar, M.; Breitfellner, M.; Castillo, M.; Martinez, S.; Prieto, R.

2012-09-01

197

Commissioning of the superconducting ECR ion source VENUS at 18 GHz  

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 are now underway. During the commissioning phase with 18 GHz, tests with various gases and metals have been performed with up to 2000 W RF power. The ion source performance is very promising [1,2]. 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 240e(micro)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 5e(micro)A of U48+, a low current, very high charge state beam. To meet these ambitious goals, VENUS has been designed for optimum operation at 28 GHz. This frequency choice has several design consequences. To achieve the required magnetic confinement, superconducting magnets have to be used. The size of the superconducting magnet structure implies a relatively large plasma volume. Consequently, high power microwave coupling becomes necessary to achieve sufficient plasma heating power densities. The 28 GHz power

198

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

199

The Ancient Mariner and the transit of Venus.  

Science.gov (United States)

The achievements of William Wales FRS - astronomer, classical scholar, demographer, editor, mathematician, meteorologist and humane teacher - have been overshadowed by the fame of Cook's extraordinary voyages, and overlooked as a significant influence on Samuel Taylor Coleridge's early development. The Royal Society sent Wales to Hudson Bay, Canada, and James Cook to Tahiti, both to observe the 1769 transit of Venus as part of an international project to calculate solar parallax, and hence the distance to the Sun. Wales later taught mathematics and navigation science at Christ's Hospital School to a precocious Coleridge, whose creative mind translated tales of polar adventures into memorable poetry. PMID:14652042

Griffin-Short, Rita

2003-12-01

200

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

 
 
 
 
201

Meteoric ion layers in the ionospheres of venus and mars: Early observations and consideration of the role of meteor showers  

Science.gov (United States)

Layers of metal ions produced by meteoroid ablation have been known in Earth's ionosphere for decades, but have only recently been discovered at Venus and Mars. Here we report the results of a search for meteoric layers in earlier datasets from Venus and Mars. We find 13 candidates at Venus in Mariner 10, Venera 9/10, and Pioneer Venus Orbiter data that augment the 18 previously identified in Venus Express data. We find 8 candidates at Mars in Mariner 7 and Mariner 9 data that augment the 71 and 10 previously identified in Mars Global Surveyor and Mars Express data, respectively. These new findings extend the ranges of conditions under which meteoric layers have been observed, support studies of the temporal variability of meteoric layers, and (for Venus) independently confirm the existence of meteoric layers. One of the proposed causes of temporal variations in the occurrence rate of meteoric layers is meteor showers. This possibility is controversial, since meteor showers have minimal observed effect on meteoric layers in Earth's ionosphere. In order to aid progress towards a resolution of this issue, we present a series of tests for this hypothesis.

Withers, Paul; Christou, A. A.; Vaubaillon, J.

2013-10-01

202

Venus III: The Atmosphere, Climate, Surface, Interior And Near-space Environment Of An Earth-like Planet  

Science.gov (United States)

The new knowledge that has been acquired about Venus since the publication of the books Venus I (1982) and Venus II (1997) will form the basis for a new volume, Venus III in 2013/14. Although stimulated by Venus Express, and timed to incorporate results from the Japanese Akatsuki mission, contributions from any source including theory, models, and future mission planning will be included, and authorship is open to all subject only to the usual editorial process and review. Cambridge University Press has expressed a strong interest in publishing the volume and we plan to make a formal proposal in January 2011. An essential part of this will be an outline of the likely chapters, authors, and total number of pages. We invite interested Venus scientists to propose or suggest topics for chapters and to indicate whether they would personally be interested in leading or contributing to them. Chapter proposals and enquiries or comments of any kind can be sent to any of the editors, and/or to fwt@atm.ox.ac.uk if possible before the end of December 2010. All contributions will be reviewed and incorporated into a draft contents list by the editors, with consultation as necessary to resolve any gaps, overlaps, or conflicts, and this will be circulated for approval before submission to the publisher.

Taylor, Fredric W.; Russell, C. T.; Satoh, T.; Svedhem, H.; Titov, D. V.

2010-10-01

203

A Survey for Satellites of Venus  

CERN Document Server

We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to satellites of about a kilometer or larger. Although several main belt asteroids were found, no satellites (moons) of Venus were detected.

Sheppard, Scott S

2009-01-01

204

Signs of possible volcanism on Venus  

International Nuclear Information System (INIS)

In this paper the author discusses some independent facts established by exploration of Venus, and endeavors to clarify the origin of such phenomena as the electrical activity of the atmosphere, the bimodal particle distribution in the clouds on Venus, and the variable properties of the upper cloud deck, all discovered by polarimetric and radiometric techniques. Analysis of recent spacecraft data suggests that the frequent electrical discharges in the surface layers of the Venus atmosphere, the variable density of the submicron haze above the clouds and certain properties of the cloud microphysics can jointly be explained if the planetary surface is undergoing volcanic eruptions

205

Novel Architecture for a Long-Life, Lightweight Venus Lander  

International Nuclear Information System (INIS)

This paper describes a novel concept for an extended lifetime, lightweight Venus lander. Historically, to operate in the 480 deg. 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 (adial 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

206

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

207

Global Geological Map of Venus  

Science.gov (United States)

Introduction: The Magellan SAR images provide sufficient data to compile a geological map of nearly the entire surface of Venus. Such a global and selfconsistent map serves as the base to address the key questions of the geologic history of Venus. 1) What is the spectrum of units and structures that makes up the surface of Venus [1-3]? 2) What volcanic/tectonic processes do they characterize [4-7]? 3) Did these processes operated locally, regionally, or globally [8- 11]? 4) What are the relationships of relative time among the units [8]? 5) At which length-scale these relationships appear to be consistent [8-10]? 6) What is the absolute timing of formation of the units [12-14]? 7) What are the histories of volcanism, tectonics and the long-wavelength topography on Venus? 7) What model(s) of heat loss and lithospheric evolution [15-21] do these histories correspond to? The ongoing USGS program of Venus mapping has already resulted in a series of published maps at the scale 1:5M [e.g. 22-30]. These maps have a patch-like distribution, however, and are compiled by authors with different mapping philosophy. This situation not always results in perfect agreement between the neighboring areas and, thus, does not permit testing geological hypotheses that could be addressed with a self-consistent map. Here the results of global geological mapping of Venus at the scale 1:10M is presented. The map represents a contiguous area extending from 82.5oN to 82.5oS and comprises ~99% of the planet. Mapping procedure: The map was compiled on C2- MIDR sheets, the resolution of which permits identifying the basic characteristics of previously defined units. The higher resolution images were used during the mapping to clarify geologic relationships. When the map was completed, its quality was checked using published USGS maps [e.g., 22-30] and the catalogue of impact craters [31]. The results suggest that the mapping on the C2-base provided a highquality map product. Units and structures: A limited set of material units and tectonic structures describes the geological situation on the surface of Venus (Fig. 1). The globally applicable stratigraphic sequence summarizing varieties of local to regional columns consists of the following units (from older to younger), the relative ages of which are established by relationships of embayment: Tessera (t) represents elevated regions deformed by multiple sets of tectonic structures. Densely lineated plains (pdl) are dissected by numerous subparallel narrow and short lineaments. Ridged plains (pr) commonly form elongated belts of ridges. Shield plains (psh) have numerous small volcanic edifices on the surface. Regional plains were divided into the lower (pr1) and the upper (pr2) units. The lower unit has uniform and relatively low radar albedo; the upper unit is brighter and often forms flow-like occurrences. Shield clusters (sc) are morphologically similar to psh but occur as small patches that postdate regional plains. Smooth plains (ps) have uniform and low radar albedo and occur near impact craters and at distinct volcanic centers. Lobate plains (pl) form fields of lava flows that are typically undeformed by tectonic structures and are associated with major volcanic centers. Several structural assemblages complicate the surface of the material units: Tessera-forming structures (ridges and grooves), belts of ridges, belts of grooves (structural unit gb), mountain belts (structural unit mt that occurs around Lakhmi Planum), wrinkle ridges, and rift zones (structural unit rt). The higly tectonized material and structural units such as t, pdl, pr, mt, and gb predate vast plains units such as psh and rp1. Wrinkle ridges deform all units that are older than units ps and pl. Smooth and lobate plains together with rift zones and shield clusters appear to be contemporaneous and form the top of the global stratigraphic column. Crater statistics: Two factors, the atmosphere screening [32-34] and the observational bias [35], appear to affect the statistics of the smaller craters on Venus. For the larger crater

Ivanov, M. A.

2008-09-01

208

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

209

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

210

Bimodal Distribution of Sulfuric Acid Aerosols in the Atmosphere of Venus  

Science.gov (United States)

Observations by the SPICAV/SOIR instruments aboard Venus Express have revealed that the upper haze of Venus, between 70 and 90 km, is variable on the order of days and that it is populated by two particle modes. In this work, we posit that the observed phenomena are caused by the transient mixing of the clouds and the haze, as well as another source of sulfuric acid aerosols in the upper haze that nucleate on meteoric dust. We test this hypothesis by simulating a column of the Venus atmosphere from 40 to 100 km above the surface using a model based upon the Community Aerosol and Radiation Model for Atmospheres and consider the effects of meteoric dust and polysulfur acting as condensation nuclei in the upper haze and upper cloud, respectively, as well as transient winds at the cloud tops caused by subsolar convection. Our aerosol number density results are consistent with Pioneer Venus data from Knollenberg and Hunten (1980), while our gas distribution results match the Magellan radio occultation data as analyzed by Kolodner and Steffes (1998) below 55 km. The size distribution of cloud particles shows two distinct modes in the upper clouds region and three distinct modes in the middle and lower clouds regions, qualitatively matching the observations of Pioneer Venus. The UH size distribution shows one distinct mode that is likely an upwelled cloud particle population with which an in situ meteoric dust condensation particle population has coagulated. The results of the transient wind simulations yield a variability timescale that is consistent with Venus Express observations, as well as a clear bimodal size distribution in the UH.

Gao, Peter; Zhang, X.; Crisp, D.; Bardeen, C. G.; Yung, Y. L.

2013-10-01

211

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 ... FYI Related links How to Perform CPR Heart Attack Vital Signs Heart Attack Risk Factors & Prevention How to Perform CPR ( ...

212

Magellan Paints a Portrait of Venus.  

Science.gov (United States)

Details of the landscape of the planet Venus as revealed by the Magellan spacecraft are discussed and illustrated. Advances beyond previous space probes are demonstrated. Details of the program are described. Additional work from this project is proposed. (CW)

Kerr, Richard A.

1991-01-01

213

Mapping Venus: Modeling the Magellan Mission.  

Science.gov (United States)

Provides details of an activity designed to help students understand the relationship between astronomy and geology. Applies concepts of space research and map-making technology to the construction of a topographic map of a simulated section of Venus. (DDR)

Richardson, Doug

1997-01-01

214

The rate of volcanism on Venus  

Science.gov (United States)

The maintenance of the global H2SO4 clouds on Venus requires volcanism to replenish the atmospheric SO2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO2 and calcite (CaCO3) to form anhydrite (CaSO4), are reported. If the rate of this reaction is representative of the SO2 reaction rate at the Venus surface, then we estimate that all SO2 in the Venus atmosphere (and thus the H2SO4 clouds) will be removed in 1.9 million years unless the lost SO2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth.

Fegley, Bruce, Jr.; Prinn, Ronald G.

1988-01-01

215

Geology of Maxwell Montes, Venus  

Science.gov (United States)

Maxwell Montes represent the most distinctive topography on the surface of Venus, rising some 11 km above mean planetary radius. The multiple data sets of the Pioneer missing and Earth based radar observations to characterize Maxwell Montes are analyzed. Maxwell Montes is a porkchop shaped feature located at the eastern end of Lakshmi Planum. The main massif trends about North 20 deg West for approximately 1000 km and the narrow handle extends several hundred km West South-West WSW from the north end of the main massif, descending down toward Lakshmi Planum. The main massif is rectilinear and approximately 500 km wide. The southern and northern edges of Maxwell Montes coincide with major topographic boundaries defining the edge of Ishtar Terra.

Head, J. W.; Campbell, D. B.; Peterfreund, A. R.; Zisk, S. A.

1984-01-01

216

Results of the first statistical study of pioneer Venus orbiter plasma observations in the distant Venus tail: Evidence for a hemispheric asymmetry in the pickup of ionospheric ions  

International Nuclear Information System (INIS)

Pioneer Venus Orbiter plasma and magnetometer observations from the first nine tail seasons of crossings of the Venus wake are used to study ion pickup in the far wake of an unmagnetized object embedded in the solar wind. This first statistical study treats all of the plasma spectra containing pickup ions in the vicinity of the Venus tail. The author finds a hemispheric asymmetry in the pickup of ionospheric ions, with approximately four times more O+ events observed in the northern magnetic hemisphere (where Z double-prime > O), i.e., the induced electric field points outward, (away from the ionopause boundary) than in the southern (Z double-prime + events, 125, or 75%, occurred in the northern hemisphere when position is calculated in terms of Venus radii and 129 or 77% occurred in the northern hemisphere when position is expressed in gyroradii. This hemisphere asymmetry in ion pickup is consistent with the prediction of the Cloutier et al. (1974) mass loading model for Venusian ions above the ionopause boundary

217

Concept study for a Venus Lander Mission to Analyze Atmospheric and Surface Composition  

Science.gov (United States)

We present a concept-level study of a New Frontiers class, Venus lander mission that was developed during Session 1 of NASA's 2011 Planetary Science Summer School, hosted by Team X at JPL. Venus is often termed Earth's sister planet, yet they have evolved in strikingly different ways. Venus' surface and atmosphere dynamics, and their complex interaction are poorly constrained. A lander mission to Venus would enable us to address a multitude of outstanding questions regarding the geological evolution of the Venusian atmosphere and crust. Our proposed mission concept, VenUs Lander for Composition ANalysis (VULCAN), is a two-component mission, consisting of a lander and a carrier spacecraft functioning as relay to transmit data to Earth. The total mission duration is 150 days, with primary science obtained during a 1-hour descent through the atmosphere and a 2-hour residence on the Venusian surface. In the atmosphere, the lander will provide new data on atmospheric evolution by measuring dominant and trace gas abundances, light stable isotopes, and noble gas isotopes with a neutral mass spectrometer. It will make important meteorological observations of mid-lower atmospheric dynamics with pressure and temperature sensors and obtain unprecedented, detailed imagery of surface geomorphology and properties with a descent Near-IR/VIS camera. A nepholometer will provide new constraints on the sizes of suspended particulate matter within the lower atmosphere. On the surface, the lander will quantitatively investigate the chemical and mineralogical evolution of the Venusian crust with a LIBS-Raman spectrometer. Planetary differentiation processes recorded in heavy elements will be evaluated using a gamma-ray spectrometer. The lander will also provide the first stereo images for evaluating the geomorphologic/volcanic evolution of the Venusian surface, as well as panoramic views of the sample site using multiple filters, and detailed images of unconsolidated material and rock textures from a microscopic imager. Our mission proposal will enable the construction of a unique Venus test facility that will attract a new generation of scientists to Venus science. With emphasis on flight heritage, we demonstrate our cost basis and risk mitigation strategies to ensure that the VULCAN mission can be conducted within the requirements and constraints of the New Frontiers Program.

Kumar, K.; Banks, M. E.; Benecchi, S. D.; Bradley, B. K.; Budney, C. J.; Clark, G. B.; Corbin, B. A.; James, P. B.; O'Brien, R. C.; Rivera-Valentin, E. G.; Saltman, A.; Schmerr, N. C.; Seubert, C. R.; Siles, J. V.; Stickle, A. M.; Stockton, A. M.; Taylor, C.; Zanetti, M.; JPL Team X

2011-12-01

218

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

219

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

220

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

 
 
 
 
221

Deuterium on Venus: Observations from Earth  

Science.gov (United States)

In view of the importance of the deuterium-to-hydrogen ratio in understanding the evolutionary scenario of planetary atmospheres and its relationship to understanding the evolution of our own Earth, we undertook a series of observations designed to resolve previous observational conflicts. We observed the dark side of Venus in the 2.3 micron spectral region in search of both H2O and HDO, which would provide us with the D/H ratio in Venus' atmosphere. We identified a large number of molecular lines in the region, belonging to both molecules, and, using synthetic spectral techniques, obtained mixing ratios of 34 plus or minus 10 ppm and 1.3 plus or minus 0.2 ppm for H2O and HDO, respectively. These mixing ratios yield a D/H ratio for Venus of D/H equals 1.9 plus or minus 0.6 times 10 (exp 12) and 120 plus or minus 40 times the telluric ratio. Although the detailed interpretation is difficult, our observations confirm that the Pioneer Venus Orbiter results and establish that indeed Venus had a period in its early history in which it was very wet, perhaps not unlike the early wet period that seems to have been present on Mars, and that, in contrast to Earth, lost much of its water over geologic time.

Lutz, Barry L.; Debergh, C.; Bezard, B.; Owen, T.; Crisp, D.; Maillard, J.-P.

1991-01-01

222

X-Band Microwave Radiometry as a Tool for Understanding the Deep Atmosphere of Venus  

Science.gov (United States)

Understanding the composition, structure, and spatial variability of the deep Venus atmosphere, including the boundary layer, is a key future direction identified in the Decadal Review. While only Mariner 2 carried a microwave radiometer for the expressed purpose of evaluating the Venus atmosphere, subsequent missions to Venus and other planets have used radar receivers in a "passive mode" to map the microwave emission from both surfaces and atmospheres. Additionally, successful mapping of microwave emissions from the atmospheres of Venus and the outer planets using earth-based antenna arrays have given unique insights into the composition and variability of such atmospheres. In the past two decades, multiple observations of Venus have been made at X band (3.6 cm) using the Jansky Very Large Array (VLA), and maps have been created of the 3.6 cm emission from Venus. Since the emission morphology is related both to surface features and to the deep atmospheric absorption from CO2 and SO2 (see, e.g., Butler et al., Icarus 154, 2001), emission measurements can be used to give unique information regarding the deep atmosphere, once surface effects are removed. Since surface emissivities measured at the 12.6 cm wavelength by the Magellan mission can be extrapolated to 3.6 cm (see, e.g., Tryka and Muhleman, JGR(Planets) 197, 1992), the residual effects due to deep atmospheric variability can potentially be detected, as they were for higher altitudes at shorter wavelengths (1.3 cm and 2.0 cm, Jenkins et.al., Icarus 158, 2002). As results from this study show, the limited resolution and sensitivity of earth-based measurements make detection of moderate atmospheric variability somewhat difficult. However, the higher sensitivity and resolution provided by an orbiting X-Band radiometer can provide important insights into the variability and structure of the Venus boundary layer. As shown in the figure, the vertical resolution of X-Band radiometry compares well with IR sounding of the deep atmosphere of Venus.

Steffes, P. G.; Devaraj, K.; Butler, B. J.

2013-12-01

223

Lomonosov, the discovery of Venus's atmosphere, and the eighteenth-century transits of Venus  

Science.gov (United States)

The discovery of Venus's atmosphere has been widely attributed to the Russian academician M.V. Lomonosov from his observations of the 1761 transit of Venus from St. Petersburg. Other observers at the time also made observations that have been ascribed to the effects of the atmosphere of Venus. Though Venus does have an atmosphere one hundred times denser than the Earth's and refracts sunlight so as to produce an 'aureole' around the planet's disk when it is ingressing and egressing the solar limb, many eighteenth century observers also upheld the doctrine of cosmic pluralism: believing that the planets were inhabited, they had a preconceived bias for believing that the other planets must have atmospheres. A careful re-examination of several of the most important accounts of eighteenth century observers and comparisons with the observations of the nineteenth century and 2004 transits shows that Lomonosov inferred the existence of Venus's atmosphere from observations related to the 'black drop', which has nothing to do with the atmosphere of Venus. Several observers of the eighteenth-century transits, includ-ing Chappe d'Auteroche, Bergman, and Wargentin in 1761 and Wales, Dymond, and Rittenhouse in 1769, may have made bona fide observations of the aureole produced by the atmosphere of Venus. Therefore, it appears that several observers-but not Lomonosov-should receive credit for first detecting the aureole due to refraction of sunlight by the atmosphere of Venus during a transit. This crucial observation occurred almost three decades before Johann Schroeter independently demonstrated the existence of the atmosphere of Venus from his analysis of extensions of the semicircle of light of the planet near inferior conjunction, which are produced by back-scattering of light by aerosol-sized particles.

Pasachoff, Jay M.; Sheehan, William

2012-03-01

224

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

225

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

226

Deuterium content of the Venus atmosphere  

Science.gov (United States)

The abundance of deuterium in the atmosphere of Venus is an important clue to the role of water in the planet's history, because ordinary and deuterated water escape the atmosphere at different rates. The high-resolution mode of the IUE was used to measure hydrogen Lyman-alpha emission from Venus, but only an upper limit on deuterium Lyman-alpha emission was found, from which was inferred a D/H ratio of less than 0.002-0.005. This is smaller by a factor of 3-8 than the D/H ratio derived from measurements by the Pioneer Venus Large Probe, and may indicate either a stratification of D/H ratio with altitude or a smaller overall ratio than previously thought.

Bertaux, Jean-Loup; Clarke, John T.

1989-01-01

227

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

228

Deuterium on Venus - Observations from earth  

Science.gov (United States)

Absorption lines of HDO and H2O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 microns, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars). The resulting value of the D/H ratio is 120 + or - 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International UIltraviolet Explorer spectra. The 100-fold enrichment of the D/H ratio on Venus compared to earth is thus a fundamental constraint on models for its atmospheric evolution.

De Bergh, Catherine; Bezard, Bruno; Owen, Tobias; Crisp, David; Maillard, Jean-Pierre

1991-01-01

229

Can Venus magnetosheath plasma evolve into turbulence?  

Science.gov (United States)

The present work aims to understand turbulence properties in planetary magnetosheath regions to obtain physical insight on the energy transfer from the larger to smaller scales, in spirit of searching for power-law behaviors in the spectra which is an indication of the energy cascade and wave-wave interaction. We perform a statistical analysis of energy spectra using the Venus Express spacecraft data in the Venusian magnetosheath. The fluxgate magnetometer data (VEXMAG) calibrated down to 1 Hz as well as plasma data from the ion mass analyzer (ASPERA) aboard the spacecraft are used in the years 2006-2009. Ten-minute intervals in the magnetosheath are selected, which is typical time length of observations of quasi-stationary fluctuations avoiding multiple boundaries crossings. The magnetic field data are transformed into the mean-field-aligned (MFA) coordinate system with respect to the large-scale magnetic field direction and the energy spectra are evaluated using a Welch algorithm in the frequency range between 0.008 Hz and 0.5 Hz for 105 time intervals. The averaged energy spectra show a power law upto 0.3 Hz with the approximate slope of -1, which is flatter than the Kolmogorov slope, -5/3. A slight hump in the spectra is found in the compressive component near 0.3 Hz, which could possibly be realization of mirror mode in the magnetosheath. A spectral break (sudden change in slope) accompanies the spectral hump at 0.4 Hz, above which the spectral curve becomes steeper. The overall spectral shape is reminiscent of turbulence. The low-frequency part with the slope -1 is interpreted as realization of the energy containing range, while the high-frequency part with the steepening is interpreted either as the beginning of energy cascade mediated by mirror mode or as the dissipation range due to wave-particle resonance processes. The present research work is fully supported by FP7/STORM (313038).

Dwivedi, Navin; Schmid, Daniel; Narita, Yasuhito; Volwerk, Martin; Delva, Magda; Voros, Zoltan; Zhang, Tielong

2014-05-01

230

Galileo infrared imaging spectroscopy measurements at venus  

Science.gov (United States)

During the 1990 Galileo Venus flyby, the Near Infrared Mapping Spectrometer investigated the night-side atmosphere of Venus in the spectral range 0.7 to 5.2 micrometers. Multispectral images at high spatial resolution indicate substantial cloud opacity variations in the lower cloud levels, centered at 50 kilometers altitude. Zonal and meridional winds were derived for this level and are consistent with motion of the upper branch of a Hadley cell. Northern and southern hemisphere clouds appear to be markedly different. Spectral profiles were used to derive lower atmosphere abundances of water vapor and other species.

Carlson, R.W.; Baines, K.H.; Encrenaz, Th.; Taylor, F.W.; Drossart, P.; Kamp, L.W.; Pollack, J.B.; Lellouch, E.; Collard, A.D.; Calcutt, S.B.; Grinspoon, D.; Weissman, P.R.; Smythe, W.D.; Ocampo, A.C.; Danielson, G.E.; Fanale, F.P.; Johnson, T.V.; Kieffer, H.H.; Matson, D.L.; McCord, T.B.; Soderblom, L.A.

1991-01-01

231

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

232

A Survey for Satellites of Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a systematic survey for satellites of Venus using the Baade-Magellan 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile. In the outer portions of the Hill sphere the search was sensitive to a limiting red magnitude of about 20.4, which corresponds to satellites with radii of a few hundred meters when assuming an albedo of 0.1. In the very inner portions of the Hill sphere scattered light from Venus limited the detection to sat...

Sheppard, Scott S.; Trujillo, Chadwick A.

2009-01-01

233

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

234

The extension of ionospheric holes into the tail of Venus  

Science.gov (United States)

Ionospheric holes are Cytherian nightside phenomena discovered by the NASA Pioneer Venus Orbiter, featuring localized plasma depletions driven by prominent and unexplained enhancements in the draped interplanetary magnetic field. Observed only during solar maximum, the phenomenon remains unexplained, despite their frequent observation during the first 3 years of the mission and more than 30 years having elapsed since their first description in the literature. We present new observations by the European Space Agency Venus Express showing that ionospheric holes can extend much further into the tail than previously anticipated (1.2 to 2.4 planetary radii) and may be observed throughout the solar cycle and over a wide range of solar wind conditions. We find that ionospheric holes are a manifestation of a deeper underlying phenomenon: tubes of enhanced draped interplanetary magnetic field that emerge in pairs from below the ionosphere and stretch far down the tail. We speculate on two possible explanations for the magnetic fields underlying the phenomena: magnetic pileup due to stagnation of ionospheric flow and internal draping around a metallic core.

Collinson, G. A.; Fedorov, A.; Futaana, Y.; Masunaga, K.; Hartle, R.; Stenberg, G.; Grebowsky, J.; Holmström, M.; Andre, N.; Barabash, S.; Zhang, T. L.

2014-08-01

235

Long-term Behaviour Of Venus Winds At Cloud Level From Virtis/vex Observations  

Science.gov (United States)

The Venus Express (VEX) mission has been in orbit to Venus for more than three years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 ?m) map the opacity of the lower cloud deck at 48 km. Here we present an analysis of the overall dynamics of Venus’ atmosphere at both levels using observations that cover a large fraction of the VIRTIS dataset. We will present our latest results concerning the zonal winds, the overall stability in the lower cloud deck motions and the variability in the upper cloud. Meridional winds are also observed in the upper and lower cloud in the UV and IR images obtained with VIRTIS. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present more irregular, variable and less intense motions in the meridional direction. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

Hueso, Ricardo; Peralta, J.; Sánchez-Lavega, A.; Pérez-Hoyos, S.; Piccioni, G.; Drossart, P.

2009-09-01

236

VizieR Online Data Catalog: Transmission spectrum of Venus (Ehrenreich+, 2012)  

Science.gov (United States)

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 0.1-5m and probes the limb between 70 and 150km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20ppm as seen from Earth, and from 0.2 to 2.7m by Mie extinction (~5ppm at 0.8m) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet. (1 data file).

Ehrenreich, D.; Vidal-Madjar, A.; Widemann, T.; Grono, G.; Tanga, P.; Barthelemy, M.; Lilensten, J.; Lecavelier Des Etangs, A.; Arnold, L.

2011-11-01

237

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

238

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

239

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

240

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

 
 
 
 
241

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

242

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

243

Navigation results of the Mariner Venus/Mercury 1973 mission  

Science.gov (United States)

The navigation aspects of the Mariner Venus/Mercury 1973 mission are presented. Principal emphasis is on the maneuver strategy employed, propellant costs and the results of the navigation performance relating to the accomplishment of the mission objectives including an extended mission for a second Mercury encounter. Key error sources and mission constraints are discussed. Of particular interest is the impact of in-flight adaptation of the pre-launch maneuver strategy (due to spacecraft anomalies) on propellant cost and the delivery achieved at the first Mercury encounter. The maneuver strategy and propellant cost for the extended mission are shown to be heavily influenced by the delivery achieved at the first Mercury encounter and the science objectives at the second Mercury encounter.

Bantell, M. H., Jr.; Jones, J. B.

1975-01-01

244

Challenges in navigation of the Venus Radar Mapper (VRM) spacecraft  

Science.gov (United States)

The subject of navigation of the Venus Radar Mapper (VRM) spacecraft is presented in the light of challenges to the accomplishment of a high accuracy in spacecraft navigation, within operational constraints, in support of quality science return (sensor performance) for the VRM mission. The paper addresses major navigational challenges arising from inherent mission constraints and describes current navigational plans as well as expected performance. The VRM mission will be the first mission to use radio interferometric data on a daily basis for spacecraft navigation. While the dependency on narrowband Delta-VLBI data for navigation accuracy has been shown in this paper, aspects of scheduling, transmission, correlation, and reliability of VLBI observations for VRM operational use remain complex. Implementation of such a system for successful VRM navigation will constitute a significant advance in application of VLBI technology.

Mohan, S. N.

1985-01-01

245

A modified density model of the Venus atmosphere at 130-200 km altitude  

Science.gov (United States)

Until recently the only information on the structure of the polar upper atmosphere of Venus available has been based on the reference atmosphere models such as the VTS3 or VIRA models. These models extrapolate the values from low latitudes to high latitudes by using equivalent solar zenith angles. New measurements by Venus Express show that such extrapolations not always give correct results and that there is a permanent overestimate of the density at high latitudes. These new results have been reached by using two different but related techniques, both using an atmospheric drag effect on the spacecraft. By reducing the pericentre altitude the total mass density in the altitude range 150-200km can be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the telecommunication link. Such measurements have been performed with Venus Express several times during the last years as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericenter pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric configuration with respect to the center of gravity, center of drag and the velocity vector. This technique has proven very sensitive, in particular if the geometric asymmetry is large, and offers an additional method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. Between 2009 and 2013 several campaigns, with altitudes going as low as 165 km, were held. The highest density measured was 1.3 10-11kg/m3 which is significantly less than earlier models predict. The results largely confirm the density measurements by the VExADE drag measurements and add to the confidence in the results from these measurements. By using these drag and torque results and assuming a hydrostatic diffusive equilibrium atmosphere a new model has been constructed.

Svedhem, Håkan; Mueller-Wodarg, Ingo; Rosenblatt, Pascal; Grotheer, Emmanuel

2014-05-01

246

Loss of hydrogen and oxygen from the upper atmosphere of Venus  

Science.gov (United States)

Atmospheric escape from the upper atmosphere of Venus is mainly influenced by the loss of hydrogen and oxygen caused by the interaction of solar radiation and particle flux with the unprotected planetary environment. Because one main aim of the ASPERA-4 particle/plasma and VEX-MAG magnetic field experiments on board of ESA's forthcoming Venus Express mission is the investigation of atmospheric erosion processes from the planet's ionosphere-exosphere environment, we study the total loss of hydrogen and oxygen and identified the efficiency of several escape mechanisms involved. For the estimation of pick up loss rates we use a gas dynamic test particle model and obtained average loss rates for H+, and O+ pick up ions of about 1×1025s-1 and about 1.6×1025s-1, respectively. Further, we estimate ion loss rates due to detached plasma clouds, which were observed by the pioneer Venus orbiter and may be triggered by the Kelvin-Helmholtz instability of about 0.5-1×1025s-1. Thermal atmospheric escape processes and atmospheric loss by photo-chemically produced oxygen atoms yield negligible loss rates. Sputtering by incident pick up O+ ions give O atom loss rates in the order of about 6×1024s-1. On the other hand, photo-chemically produced hot hydrogen atoms are a very efficient loss mechanism for hydrogen on Venus with a global average total loss rate of about 3.8×1025s-1, which is in agreement with Donahue and Hartle [1992. Solar cycle variations in H+ and D+ densities in the Venus ionosphere: implications for escape. Geophys. Res. Lett. 12, 2449-2452] and of the same order but less than the estimated H+ ion outflow on the Venus nightside of about 7.0×1025s-1 due to acceleration by an outward electric polarization force related to ionospheric holes by Hartle and Grebowsky [1993. Light ion flow in the nightside ionosphere of Venus. J. Geophys. Res. 98, 7437-7445]. Our study indicates that on Venus, due to its larger mass and size compared to Mars, the most relevant atmospheric escape processes of oxygen involve ions and are caused by the interaction with the solar wind. The obtained results indicate that the ratio between H/O escape to space from the Venusian upper atmosphere is about 4, and is in a much better agreement with the stoichiometrically H/O escape ratio of 2:1, which is not the case on Mars. However, a detailed analysis of the outflow of ions from the Venus upper atmosphere by the ASPERA-4 and VEX-MAG instruments aboard Venus Express will lead to more accurate atmospheric loss estimations and a better understanding of the planet's water inventory.

Lammer, H.; Lichtenegger, H. I. M.; Biernat, H. K.; Erkaev, N. V.; Arshukova, I. L.; Kolb, C.; Gunell, H.; Lukyanov, A.; Holmstrom, M.; Barabash, S.; Zhang, T. L.; Baumjohann, W.

2006-11-01

247

Thermal Radiation In The Lower Venus Atmosphere  

Science.gov (United States)

Venus atmosphere is for a long time known for the strong greenhouse effect that gov- erns this unique climate system, however, the details of its radiative properties remains poorly known. In particular, the complexity of physics related to line broadening un- der Venus conditions results in major uncertainty of simulated infrared opacities and fluxes. Based on the theory of spectral line far wing and available spectroscopic in- formation, we have built an accurate and efficient model for thermal radiation under Venus conditions. Adopted assumptions on the spectral line contour at high pressures and its impact to the thermal balance were comprehensively tested. Simulations of thermal radiation intensities and fluxes show that they are highly dependent on spec- tral line formfactor. 1D thermal balance simulation taking into account dynamical heat transfer has resulted in quantitative evaluation of basic mechanisms that form green- house effect on Venus. In a wide altitude range between 30 and 50 km, dynamical heat transfer appears to substantially contribute to the maintenance of the present thermal profile. This work has been supported by RFBR grant 01-02-17481

Afanasenko, T. S.; Rodin, A. V.; Rodimova, O. B.; Tvorogov, S. D.

248

The guinevere project at the venus facility  

International Nuclear Information System (INIS)

The GUINEVERE project is a European project in the framework of FP6 IP-EUROTRANS. The IP-EUROTRANS project aims at addressing the main issues for ADS development in the framework of partitioning and transmutation for nuclear waste volume and radiotoxicity reduction. The GUINEVERE project is carried out in the context of Domain 2 of IP-EUROTRANS, ECATS, devoted to specific experiments for the coupling of an accelerator, a target and a subcritical core. These experiments should provide an answer to the questions of on-line reactivity monitoring, subcriticality determination and operational procedures (loading, start-up, shutdown, etc.) in an ADS by 2009-2010. The GUINEVERE project will make use of the VENUS reactor, serving as a lead fast critical facility, coupled to a continuous beam accelerator. In order to achieve this goal, the VENUS facility has to be adapted and a modified GENEPI-C accelerator has to be designed and constructed. During the years 2007 and 2008, the VENUS facility will he modified in order to allow the experimental programme to start in 2009. The paper describes the main achievements with regard to the modifications for the VENUS facility. (authors)

249

Different types of small volcanos on Venus  

Science.gov (United States)

One of the studies of volcanic activity on Venus is the comparison of that with the analogous volcanic activity on Earth. The preliminary report of such a comparison and description of a small cluster of small venusian volcanos is represented in detail in this paper.

Slyuta, E. N.; Shalimov, I. V.; Nikishin, A. M.

1992-01-01

250

First ever in-situ density measurements in Venus' polar upper atmosphere by combined drag and torque measurements  

Science.gov (United States)

Information on the atmospheric density in the altitude range 150-200 km in the atmosphere of Venus is difficult to gather remotely. The Pioneer Venus Orbiter Neutral Mass Spectrometer measured gas densities in the equatorial upper atmosphere in-situ, but no such measurements have ever been made in the polar regions of Venus. The Venus Express spacecraft on its orbit approaches the planet in the northern polar region, but is not equipped with a mass spectrometer instrument for in-situ gas density measurements. By reducing the pericentre altitude the total mass density can however be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the telecommunication link. Such measurements have been performed with Venus Express several times during the last year as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericentre pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric attitude with respect to the centre of gravity, centre of drag and the velocity vector. This technique has proven very sensitive, in particular if the asymmetry is large, and offers a further method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. First torque measurements carried out during last years' low pericentre passes have confirmed the density measurements by the VExADE drag measurements to an amazingly good accuracy and added to the confidence in the results from these measurements. New combined measurements, where the asymmetry is increased by rotating the solar panels, are planned for February and April 2010. The new results will be discussed at the meeting.

Svedhem, Håkan; Mueller, Michael; Mueller-Wodarg, Ingo

251

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.

252

The 557.7 nm Oxygen Green Line in the Venus Nightglow  

Science.gov (United States)

Observations of Venus in 1999 from the Keck I telescope in Hawai'i showed that the oxygen green line can be a relatively strong nightglow feature ( 150 R), rivaling the intensity of the terrestrial green line [Slanger et al., 2001]. The emission was not seen in two orbital missions - the Venera 9/10 study, in which the O2 Herzberg II bands were first observed [Krasnopolsky et al., 1976], and more recently, the Venus Express (VIRTIS) measurements [Garcia-Muñoz et al., 2009]. Repeated ground-based measurements of the green line have found an intensity varying strongly from apparition to apparition [Slanger et al., 2006]; it has so far not reached the emission level seen in November 1999, at close to solar maximum. We assume that the source of the green line is either O-atom recombination in the mesosphere, or O2+ dissociative recombination (DR) in the ionosphere, the two main terrestrial processes. The 2007-2008 data used in the VIRTIS/VEX study were co-added over many orbits, during a period when ground-based observations indicated a moderate ( 50 R) green line intensity. In this presentation we consider the argument for a mesospheric vs an ionospheric source. A mesospheric source would be strongly modulated by the temperature-dependent quenching of O(1S) by CO2. An ionospheric source could be interpreted in terms of ion densities [Pätzold et al., 2007]. Although the O(1D) yield is much larger than that of O(1S) from O2+ DR, O(1D) quenching by CO2 would preclude its observation and indeed, no oxygen red line was seen in 1999 when the green line intensity was at its peak. [Supported by NASA Planetary Astronomy] Garcia-Munoz, A., et al., J. Geophys. Res., (submitted, 2009). Krasnopolsky, V.A. et al., Cosmic Research, 1976. Patzold, M. et al., Nature, doi:10.1038/nature06239, 2007 Slanger, T.G., et al., Science, 2001. Slanger, T.G., et al., Icarus, 2006.

Slanger, Tom G.; Fox, J. L.

2009-09-01

253

Compositions of Igneous Rocks on Venus  

Science.gov (United States)

The limited available data on Venus' igneous rocks (from landed geochemistry and radar-based geomorphology and elevation data) are all consistent with basalt of one variety or another. Venus' shield volcanos have shallow slopes, comparable to terrestrial basalt shields; Venus' lava plains are consistent with extensive flows of fluid lava, i.e. basalt; the margins of distinct lava flows are consistent also with fluid like basalt. A few small volcanic constructs (e.g., pancake domes) could represent more silicic lavas, but could also represent basalt extrusives, either crystal-rich or with very slow effusion rates. The Venera and VEGA landers, technical and scientific triumphs that they were, provided limited and imprecise constraints on the chemistry of Venus' basalts. Their landing sites were all in the lowland plains, and so did not sample rocks from any highland: shield volcanos, tesserae, nor the unique plateau and high mountains of Ishtar Terra. The V/V analyses for Mg, Al, and Mn are little more than 2? detections, and V/V returned no data on Na, Cr, Ni, P and other minor/trace elements. The V/V analyses for K, U, and Th (by ? rays) are imprecise, except for one (Venera 8) with extremely high K (~4% K2O) and one (Venera 9) with a super- chondritic Th/U abundance ratio (at the 2? level). Even with this imprecise limited data, a few inferences are fairly sound. [1] The FeO content of Venus basalts is similar to those of Earth basalts, suggesting a comparable mantle composition and thus a similar-sized core. [2] The range of K abundances suggests significant processes of depletion and enrichment in incompatible elements, consistent with repeated or extensive igneous processing. [3] The super-chondritic Th/U value measured by V9 is difficult to generate in low- pressure silicate melt/crystal fractionations. This Th/U value could possibly represent garnet fractionation in the mantle source, action of an ionic fluid (like carbonate melt) or even action of liquid water. [4] The Venus basalts, as a whole, have sub-chondritic Ca/Al. This relative deficit in Ca could arise from weathering at Venus's surface, or could be a primary characteristic possibly reflecting an origin as melted eclogite.

Treiman, A. H.

2007-05-01

254

In-situ Observations of a Co-rotating Interaction Region at Venus Identified by IPS and STEREO  

Science.gov (United States)

This paper reports on the first combination of results from in-situ plasma measurements at Venus, using data from Venus Express, and remote sensing data from observations of interplanetary scintillation (IPS). In so doing, we demonstrate the value of combining remote sensing and in-situ techniques for the purpose of investigating interaction between solar wind, under several different conditions, and the Venusian magnetosphere. The ion mass analyser instrument (IMA) is used to investigate solar wind interaction with the Venusian magnetosphere in the presence of two different solar wind phenomena; a co-rotating interaction region (CIR) and a coronal mass ejection (CME). The CIR, detected with IPS and sampled in-situ at Venus is found to dramatically affect upstream solar wind conditions. These case studies demonstrate how combining results from these different data sources can be of considerable value when investigating such phenomena.

Whittaker, I. C.; Dorrian, G. D.; Breen, A.; Grande, M.; Barabash, S.

2010-08-01

255

Geophysical Research Letters. Selected Papers on Pioneer Venus Orbiter: Entry Phase. Volume 20  

Science.gov (United States)

Contents include the following papers which are comprised of subject matter related to the The Pioneer Venus Orbiter's Entry Phase: The Pioneer Venus entry phase; solar cycle variations of electron density and temperature in the Venusian nightside ionosphere; the magnetic state of the lower ionosphere during Pioneer Venus entry phase; the nightside ionosphere of Venus under varying levels of solar EUV flux; observation of the nightside Venus ionosphere; final encounter of the Pioneer Venus orbiter ion mass spectrometer; ion measurement during Pioneer Venus reentry; implications for solar cycle variation of ion composition and dynamics; evidence for day-to-night ion transport at low solar activity in the Venus pre-dawn ionosphere; model calculations of the dayside ionosphere of Venus at solar minimum; natural composition measurements by the Pioneer Venus neutral mass spectrometer during orbiter reentry; the Venus atmospheric response to solar cycle variations; and plasma waves observed at low altitudes in the tenuous Venus nightside ionosphere.

1993-01-01

256

Venus: Crater distribution and plains resurfacing models  

Science.gov (United States)

Detailed analysis of the distribution of craters on Venus using Mth nearest neighbor analysis, coupled with models based upon surface morphology constraints, indicates that the hypothesis of complete spatial randomness (CSR) cannot be rejected, but is not a unique model of the observed crater distribution. Based on morphologic mapping, the extensive volcanic plains can be divided into four units that have a spread in age of the order of 0.5T (the mean surface age of the planet). This four-unit plains model, along with its derivatives, produce test statistics that indicate such models also cannot be rejected. Further, the probability of obtaining a result at least as extreme as the observed test statistic given that the null hypothesis (model corresponds to Venus) is true is lowest for the CSR model. There is no particular reason to pick a CSR model (along with its implications for catastrophic resurfacing) as a constraint on the evolution of Venus, and there are geological reasons to choose the multiage models. We find that we cannot distinguish statistically among models that have two, three, or four distinct production ages within the plains. However, the hypothesis that the variation in crater density within all of the plains is due to a single random process can be rejected for two reasons. First, the binomial probability that such a process could exist within each of the plains units is CSR cannot be used as a constraint on models of resurfacing or planetary evolution of Venus because of the non-uniqueness in matching such a model to the observed crater distribution and the strong indication of distinct ages within the plains with a significant spread in age. Geological and geophysical constraints provide our best clues for understanding Venus.

Hauck, Steven A.; Phillips, Roger J.; Price, Maribeth H.

1998-06-01

257

Educational Impact of the Transit of Venus 2004  

Science.gov (United States)

The 2004 transit of Venus was viewed by millions of people around the world. For this historic event, the NASA Sun Earth Connection Education Forum developed and executed a large international education program with cross discipline ties to math, science, geography, history, and music. The program consisted of on site web casts, NASA TV programming, on line data and other resources, observatory and spacecraft images, science center activities, and materials and curricula for schools. Program sucess was driven by the large number of NASA and external partnerships including each of the Space Science education forums, amateur astronomers, observatories from Nova Scotia to Uraguay, Earth and Sky Radio, PlanetQuest, Library of Congress, Museum of American History, Astronomy Cafe, and many, many other science and education groups. Current impact estimates point to well over 20 million people that were touched by this program. In addition, the recent OSS Product Review identified the March PlanetQuest program as their number 1 rated product. This talk will outline the details of this extraordinary education program.

Mayo, L.

2004-11-01

258

PIONEER VENUS 2 MULTI PROBE IS ENCAPSULATED IN PROTECTIVE SHROUD  

Science.gov (United States)

Encapsulation of the Pioneer Venus Multiprobe in its protective nose fairing is closely monitored by technicians in Hangar AO. The 2,000-pound spacecraft is one of two being launched toward the planet Venus. The Multiprobe is scheduled for launch aboard an Atlas Centaur rocket on August 7. Flying a direct path to the cloud-shrouded planet, the Multiprobe will reach Venus five days after the arrival of its sister spacecraft, the Pioneer Venus Orbiter, which was launched May 20, 1978. Three weeks before the Multiprobe reaches Venus, its four heavily instrumented scientific probes (seen on top of the spacecraft's main body or ''bus'') will be released and will impact at various points on the planet's surface. Together, the two spacecraft will conduct a thorough scientific exploration of the planet Venus.

1978-01-01

259

Search for a Venus halo effect during 1970.  

Science.gov (United States)

Photometric observations of Venus during 1970 inferior conjunction, in contrast to observations made during the 1969 inferior conjunction, show no evidence of a Venus halo effect at 158 phase angle. The upper limit to brightening is about 0.005 mag but can still be reconciled with earlier results. Because of the importance of the question of H2O-ice in the Venus clouds, further observations are encouraged to remove the marginality of most observations to date.

Ward, D.; O'Leary, B.

1972-01-01

260

Solar wind interaction with comets - lessons from Venus  

International Nuclear Information System (INIS)

Data on the solar wind interaction with Venus are examined for the purpose of comparison with similar processes that may occur in comets. Attention is given to bow shock, magnetosheath, ionopause, ionosphere, and magnetotail of Venus. These features are compared with, respectively, the bow shock, magnetosheath, contact surface, coma, and plasma tail of a comet. It is concluded that observations of the solar wind interaction with Venus should provide new insight into the solar wind interaction with comets

 
 
 
 
261

SO2 on Venus: A final cross-calibration with Pioneer Venus  

Science.gov (United States)

The three observing programs under NASA Grant NAG5-1913 are described. They are NSOSS, VEOEB, and PCOEB. The scientific objectives for the IUE observation program NSOSS were to: make the first ever UV observations of a near-earth asteroid (4179 Toutatis), an irregular satellite of Jupiter (Himalia), and the Saturnian satellite Hyperion; obtain the first radially-dependent information on the UV color of Saturn's rings; gather the uncontaminated UV spectra of Iapetus's bright and dark hemispheres; and obtain a spectrum of Titania to initiate the comparitive study of UV photometric properties in Uranian system. The VEOEB program studied Venus SO2, an important indicator of key processes in the Venus atmosphere and perhaps Venus surface. Based on past Pioneer Venus and IUE observations, significant SO2 variations have been interpreted as indicating that the long term atmospheric SO2 abundance may be related to large, episodic injections from the surface or interior of Venus. The PCOEB program studied the Pluto-Charon system, for which evidence of a variable UV light curve has been presented. This program is to complete the coverage of that UV light curve, since only approximately 26% has been observed.

1994-01-01

262

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

263

Atmospheric tides on Venus. III - The planetary boundary layer  

Science.gov (United States)

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Dobrovolskis, A. R.

1983-10-01

264

The Structure of the Upper Atmosphere of Venus - New Measurements and Models of the Northern Polar Region  

Science.gov (United States)

Until recently the only information on the structure of the polar upper atmosphere of Venus available has been based on the reference atmosphere models such as the VTS3 or VIRA models. These models extrapolate the values from low latitudes to high latitudes by using equivalent solar zenith angles. New measurements by Venus Express show that such extrapolations not always give correct results and that there is a general overestimate of the density at high latitudes. These new results have been reached by using two different but related techniques, both using an atmospheric drag effect on the spacecraft. By reducing the pericentre altitude the total mass density in the altitude range 150-200km can be measured in situ by monitoring the orbital decay caused by the drag on the spacecraft by the atmosphere via direct tracking of the Doppler signal on the telecommunication link. Such measurements have been performed with Venus Express several times during the last years as part of the Venus Express Atmospheric Drag Experiment (VExADE). The results indicate a large variability within only a few days and have led to questions if these variations are real or within the uncertainty of the measurements. A completely different and independent measurement is given by monitoring the torque asserted by the atmosphere on the spacecraft. This is done by monitoring the momentum accumulated in the reaction wheels during the pericentre pass and at the same time considering all other perturbing forces. This requires the spacecraft to fly in an asymmetric attitude with respect to the centre of gravity, centre of drag and the velocity vector. This technique has proven very sensitive, in particular if the geometric asymmetry is large, and offers an additional method of measuring atmospheric densities in-situ that previously had not been explored with the Venus Express spacecraft. Similar measurements have been done in the past by Magellan at Venus and by Cassini at Titan. Between 2009 and 2011 several campaigns, with altitudes going as low as 165 km, were held. The highest density measured was 7.7 10-12kg/m3 which is significantly less than earlier models predict. The results largely confirm the density measurements by the VExADE drag measurements and add to the confidence in the results from these measurements. By using these drag and torque results and assuming a hydrostatic diffusive equilibrium atmosphere a new model has been constructed. The model is fitted to the Venus Express remote sensing measurements in the upper mesosphere (VeRa radio occultation data) and lower thermosphere (SpicaV/SOIR data) to give a continuous transition across the different regions.

Svedhem, H.; Mueller-Wodarg, I. C.; Rosenblatt, P.

2011-12-01

265

The Transit of Venus and the Notorious Black Drop  

Science.gov (United States)

With the long-awaited transit of Venus soon approaching, I have been looking at the question of the physical cause of the notorious Black Drop effect. This effect has Venus' silhouette appear with a meniscus between the planet and the solar limb around the time of interior contacts. The Black Drop confused the timings of contacts and greatly reduced the accuracy of the measured Astronomical Unit. At least one book calls this the cause for the ultimate failure of the world's first grand international science program. The majority of books claim that the Black Drop is caused by diffraction, illusion, or atmospheric refraction. However, all of these are easy to disprove. Diffraction redistributes light over a nano-arc-second angular scale and hence is negligible, while it cannot be illusion or a Venusian atmospheric phenomenon since the effect has been photographed during transits of Mercury. The correct explanation has been known at least since 1770 when J. J. de Lalande proposed that normal terrestrial atmospheric smearing would blur the image such that a meniscus appears. I have modeled this smearing and find that isophotal contours indeed show meniscuses. The atmospheric seeing should thus be correlated with the appearance of the Black Drop, as indeed it is. Visual perception also enters since the observer makes some judgement as to which isophotal contour to label as the edge, and the appearance of the bridge will depend on this choice. An additional source of smearing will be the ordinary diffraction within the telescope, and this accounts for why the transit observers in the 1700's (with their small apertures) had much more trouble with the Black Drop than those during the 1800's. Smearing can also arise due to the finite size of the eye's pupil in the case of a thumb and forefinger held close together immediately in front of the eye, and this provides a Black Drop that can be easily seen or photographed at any time.

Schaefer, B. E.

2000-12-01

266

Venus-solar wind interaction in a hybrid plasma simulation model  

Science.gov (United States)

We present a study of the plasma interaction between Venus and the solar wind. In the study we use a computer simulation model to interpret recerently acquired insitu data by the Venus Express spacecraft. The numerical simulation is based on a 3-dimensional hybrid model, which consists of particle ions, a charge neutralizing massless electron fluid and non-radiative electrodynamics. This arrangement makes it possible to study self-consistently coupled ion kinetics and electromagnetism in a global planetary scale. In the model, the Venusian upper atmosphere and exosphere are modelled as a perfectly conducting ionospheric medium and hydrogen and oxygen photoion production. Given the upstream conditions and the spatial planetary ion distributions the model provides, for example, the escape rates of the atmospheric ion populations and the geometry of the interplanetary magnetic field draped around the planet. Here the model is used to study ion observations from the ASPERA-4 plasma instrument and magnetic field measurements from the MAG magnetometer on Venus Express.

Jarvinen, R.; Kallio, E.; Barabash, S.; Zhang, T. L.; Fedorov, A.; Sillanpää, I.; Janhunen, P.

2007-08-01

267

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

268

Electron plasma oscillations in the Venus foreshock  

International Nuclear Information System (INIS)

Plasma waves are observed in the solar wind upstream of the Venus bow shock by the Pioneer Venus Orbiter. These wave signatures occur during periods when the interplanetary magnetic field through the spacecraft position intersects the bow shock, thereby placing the spacecraft in the foreshock region. The electron foreshock boundary is clearly evident in the data as a sharp onset in wave activity and a peak in intensity. Wave intensity is seen to drop rapidly with increasing penetration into the foreshock. The peak wave electric field strength at the electron foreshock boundary is found to be similar to terrestrial observations. A normalized wave spectrum was constructed using measurements of the electron plasma frequency and the spectrum was found to be centered about this value. These results, along with polarization studies showing the wave electric field to be field aligned, are consistent with the interpretation of the waves as electron plasma oscillations

269

Mariner 10 mission to Venus and Mercury  

Science.gov (United States)

The unmanned spacecraft Mariner 10 was launched on November 3, 1973. Investigations conducted during the first part of its journey included studies carried out to calibrate the instruments in the well-known environment of the earth-moon system. Images of the north polar region of the moon were obtained and observations of the comet Kohoutek were made. Mariner confirmed the presence of a Venus bowshock. Information obtained by the spacecraft about the Venus atmosphere is considered. On March 29, 1974, Mariner 10 passed across the night side of Mercury only 703 kilometers above the planetary surface. It was found that Mercury is a moon-like body, heavily cratered, and with large, flat, circular basins similar to those on the moon and Mars.

Giberson, W. E.; Cunningham, N. W.

1974-01-01

270

Periodic solar EUV flux monitored near Venus  

Science.gov (United States)

A detector sharing the orbital rate of Venus has a unique perspective on solar periodicities. Fourier analysis of the 8.6 year record of solar EUV output gathered by the Langmuir probe on Pioneer Venus Orbiter shows the influences of global oscillation modes located in the convective envelope and in the radiative interior. Seven of the eight lowest angular harmonic r-mode familes are detected by their rotation rates which differ almost unmeasurably from ideal theoretical values. This determines a mean sidereal rotation rate for the envelope of 457.9 + or - 2.0 nHz which corresponds to a period of 25.3 days. Many frequencies are aliased at + or - 106 nHz by modulation from the lowest angular harmonic r-mode in the envelope.

Wolff, Charles L.; Hoegy, Walter R.

1989-01-01

271

Venus transit, aureole and solar diameter  

CERN Document Server

The possibility to measure the solar diameter using the transits of Mercury has been exploited to investigate the past three centuries of its evolution and to calibrate these measurements made with satellites. This measurement basically consists to compare the ephemerides of the internal contact timings with the observed timings. The transits of Venus of 2004 and 2012 gave the possibility to apply this method, involving a planet with atmosphere, with the refraction of solar light through it creating a luminous arc all around the disk of the planet. The observations of the 2012 transit made to measure the solar diameter participate to the project Venus Twilight Experiment to study the aureole appearing around it near the ingress/egress phases.

Xie, Wenbin; Wang, Xiaofan; Tanga, Paolo

2012-01-01

272

Comparison of measurements of electromagnetic induction in the magnetosphere of Venus with laboratory simulations  

International Nuclear Information System (INIS)

Analysis of Venera 9 and 10 data suggest a comingled excitation of the ionosphere of Venus by the time dependent component of the interplanetary magnetic field, upon which may be superimposed a contribution from the interplanetary electric field. The inductive contributions correspond respectively to generation of eddy currents and to unipolar induction, i.e., the TE and TM modes of classical electromagnetism. The former is suggested when the interplanetary magnetic field exhibits significant changes in intensity or orientation, but could also have contributions from fluctuations in plasma pressure expressed through the frozen-in field. The magnetic field measured near Venus by Venera 9 and 10 is considered within this framework and with respect to laboratory simulation using both conducting and insulated (but internally conducting) spheres. (Auth.)

273

The Venus nitric oxide night airglow - Model calculations based on the Venus Thermospheric General Circulation Model  

Science.gov (United States)

The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General Circulation Model (Dickinson et al., 1984), modified to include simple odd nitrogen chemistry. Results obtained for the solar maximum conditions indicate that the recently revised dark-disk average NO intensity at 198.0 nm, based on statistically averaged OUVS measurements, can be reproduced with minor modifications in chemical rate coefficients. The results imply a nightside hemispheric downward N flux of (2.5-3) x 10 to the 9th/sq cm sec, corresponding to the dayside net production of N atoms needed for transport.

Bougher, S. W.; Gerard, J. C.; Stewart, A. I. F.; Fesen, C. G.

1990-01-01

274

The Superrotation of Venus: Where's the Torque?  

CERN Document Server

The superrotation of the atmosphere of Venus requires a large torque on the up- per atmosphere. Mechanisms for providing a net balancing of this through waves or ionospheric motions to other parts of the atmosphere have been proposed but all have difficulties. Here we demonstrate that the albedo gradient from the day to night side of the cloud layer allows a gradient of light pressure that is sufficient to provide an external torque to drive this flow.

Chafin, Clifford

2014-01-01

275

An impact hypothesis for Venus argon anomalies  

Science.gov (United States)

The Ar-36+38 argon-excess anomally of Venus has been hypothesized to have its origin in the impact of an outer solar system body of about 100-km diameter. A critical evaluation is made of this hypothesis and its competitors; it is judged that its status must for the time being remain one of 'Sherlock Holmes' type, in that something so improbable must be accepted when all alternatives are eliminated.

Kaula, W. M.; Newman, W. I.

1997-03-01

276

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

277

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

278

Venus - Lineated Plains in Lakshmi Region  

Science.gov (United States)

This mosaic shows an area of the Lakshmi region that is located 30 degrees north latitude and 333.3 degrees east longitude. (Longitude on Venus is measured from 0 degrees to 360 degrees east). The area shown measures about 37 kilometers (23 miles) wide and 80 kilometers (50 miles) long. Based on data from the Pioneer Venus Orbiter and the ground-based Arecibo Radar Observatory, it is known that this region is located on the low rise that separates Sedna Planitia and Guinevere Planitia, just to the west of Eistla Regio. Two sets of parallel lineations are seen intersecting almost at right angles. The fainter lineations are spaced at regular intervals of about one kilometer (0.6 mile) and extend beyond the boundary of the image. The width of the faint lineations is at the limit of resolution of the best Magellan images. The brighter, more dominant lineations are less regular and, in places, appear to begin and end where they intersect the fainter lineations. It is not clear whether the two sets of lineations are faults or fractures, but in other Magellan images, these bright lineations are associated with pit craters and volcanic features. This type of terrain has not been seen on Venus nor on other planets. North is at the top of the image.

1990-01-01

279

VLF imaging of the Venus foreshock  

Science.gov (United States)

VLF plasma wave measurements obtained from the Pioneer Venus Orbiter Electric Field Detector (OEFD) have been used to construct statistical images of the Venus foreshock. Our data set contains all upstream measurements from an entire Venus year (approximately 200 orbits). Since the foreshock VLF characteristics vary with Interplanetary Magnetic Field (IMF) orientation we restrict the study to IMF orientations near the nominal Parker spiral angle (25 to 45). Our results show a strong decrease in 30 kHz wave intensity with both foreshock depth and distance. There is also an asymmetry in the 30 kHz emissions from the upstream and downstream foreshocks. The ion foreshock is characterized by strong emissions in the 5.4 kHz OEFD channel which are positioned much deeper in the foreshock than expected from terrestrial observations. No activity is observed in the region where field aligned ion distributions are expected. ULF wave activity, while weaker than at Earth, shows similar behavior and may indicate the presence of similar ion distributions.

Crawford, G. K.; Strangeway, R. J.; Russell, C. T.

1993-01-01

280

Signs of hypothetical fauna of Venus  

Science.gov (United States)

On March 1 and 5, 1982, experiments in television photography instrumented by the landers VENERA-13 and -14, yielded 37 panoramas (or their fragments) of the Venus surface at the landing site. Over the past 31 years, no similar missions have been sent to Venus. Using a modern technique the VENERA panoramas were re-examined. A new analysis of Venusian surface panoramas' details has been made. A few relatively large objects of hypothetical fauna of Venus were found with size ranging from a decimeter to half meter and with unusual morphology. Treated once again VENERA-14 panoramic images revealed `amisada' object about 15 cm in size possessing apparent terramorphic features. The amisada's body stands out with its lizard-like shape against the stone plates close by. The amisada can be included into the list of the most significant findings of the hypothetical Venusian fauna. The amisada's body show slow movements, which is another evidence of the Venusian fauna's very slow style of activity, which appears to be associated with its energy constraints or, and that is more likely, with the properties of its internal medium. The terramorphic features of the Venusian fauna, if they are confirmed, may point out at outstandingly important and yet undiscovered general laws of the animated nature on different planets.

Ksanfomality, Leonid V.

2014-04-01

 
 
 
 
281

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

282

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.

283

Regional tectonic analysis of Venus as part of the Pioneer Venus guest investigator project  

Science.gov (United States)

Over the past year, much of the tectonic analysis of Venus we have done has centered on global properties of the planet, in order to understand fundamental aspects of the dynamics of the mantle and lithosphere of Venus. We have developed convection models of the Earth and Venus. These models assume whole mantle internally-heated convection. The viscosity is temperature, volatile-content, and stress dependent. An initial temperature and volatile content is assumed, and the thermal evolution is tracked for 4.6 billion years. During this time, heating occurs by decay of radiogenic elements in the mantle, and degassing and regassing of volatiles takes place at the surface. For a model assuming plate tectonics as the primary heat loss mechanism, representing the Earth through most of it's history and perhaps Venus' earlier history, degassing of the mantle was found to occur rapidly (approximately 200 My) over a large range of parameters. Even for parameters chosen to represent extreme cases of an initially cool planet, low radiogenic heating, and large initial volatile complement, the mantle water content was degassed to an equilibrium value in about 2 By. These values may be applicable to the early Venus, if a large, Moon-forming impact on Earth resulted in efficient heating and loss of water, leaving Venus with a comparably greater volatile budget and less vigorous early convection. It may therefore be impossible to retain large amounts of water in the interior of Venus until the planet cools down enough for the 'cold-trap' effect to take place. This effect traps crust forming melts within the mantle due to a cusp in the solidus, causing these melts to refreeze at depth into a dense eclogite phase, which will inhibit ascent of this material to the surface. This effect, however, requires a hydrous mantle, so early loss of water might prevent it from taking place. Since without plate tectonics there is no mechanism for regassing volatiles into the mantle, as occurs on Earth at subduction zones, this means the interior of Venus would at present be almost completely dry. We have also calculated argon degassing, and mantle flow velocities. viscosities, and cooling rates in these models, and these values can provide constraints on present day mantle dynamics.

Williams, David R.

1991-01-01

284

Carbonate-sulfate volcanism on Venus?  

Science.gov (United States)

Venusian canali, outflow channels, and associated volcanic deposits resemble fluvial landforms more than they resmeble volcanic features on Earth and Mars. Some canali have meandering habits and features indicative of channel migration that are very similar to meandering river channels and flood plains on Earth, venusian outflow channels closely resemble water-carved outflow channels on Mars and the Channeled Scabland in Washington, collapsed terrains at the sources of some venusian channels resemble chaotic terrains at the sources of martian outflow channels, venusian lava deltas are similar to bird's-foot deltas such as the Mississippi delta, and venusian valley networks indicate sapping. We have developed an alternative possibility that the lava had a water-like rheology and a melting point slightly greater than Venus' surface temperature, thus accounting for the unusual behavior of the lava. Unlike silicate lavas, some carbonatites (including carbonate-sulfate-rich liquids) have these properties; thus they can flow great distances while retaining a high fluidity, significant mechanical erosiveness, and substantial capacity to transport and deposit sediment. Venusian geochemistry and petrology are consistent with extensive eruptions of carbonatite lavas, which could have crustal and/or mantle origins. Venus' atmosphere (especially CO2, HCl, and HF abundances) and rocks may be in local chemical equilibrium, which suggests that the upper crust contains large amounts of calcite, anhydrite, and other salts. Chemical analyses indicate, according to some models, that Venusian rocks may contain 4-19% calcite and anhydrite. Mixtures of crustal salts could melt at temperatures a few tens to a few hundred Kelvins higher than Venus' surface temperature; hence, melting may be induced by modest endogenetic or impact heating. Salts may have many of the same geologic roles on Venus as water and ice have on Mars. A molten salt (carbonatite) 'aquifer' may exist beneath a few hundred meters to several kilometers of solidified salt-rich 'permafrost.' Many geologic features can be explained by carbonatite magmatism: (1) impact melting of crustal salts can explain crater outflows, (2) small, sustained eruptions from molten salt aquifers can explain sapping valleys, (3) large, sustained eruptions may explain canali and their flood plans, and (4) catastrophic outbursts amy have formed outflow channels and chaotic terrain. Landforms created by carbonate-rich lavas would be thermally stable on Venus' surface, though some minerals may weather to other solid substances.

Kargel, Jeffrey S.; Kirk, Randolph L.; Fegley, Bruce, Jr.

1994-01-01

285

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

286

Venus, Mars, and the ices on Mercury and the moon: astrobiological implications and proposed mission designs.  

Science.gov (United States)

Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have adapted to live in these ecological niches by the evolutionary force of directional selection. Missions to our neighboring planets should therefore be planned to explore these potentially life-containing refuges and return samples for analysis. Sample return missions should also include ice samples from Mercury and the Moon, which may contain information about the biogenic material that catalyzed the early evolution of life on Earth (or elsewhere). To obtain such information, science-driven exploration is necessary through varying degrees of mission operation autonomy. A hierarchical mission design is envisioned that includes spaceborne (orbital), atmosphere (airborne), surface (mobile such as rover and stationary such as lander or sensor), and subsurface (e.g., ground-penetrating radar, drilling, etc.) agents working in concert to allow for sufficient mission safety and redundancy, to perform extensive and challenging reconnaissance, and to lead to a thorough search for evidence of life and habitability. PMID:16379531

Schulze-Makuch, Dirk; Dohm, James M; Fairén, Alberto G; Baker, Victor R; Fink, Wolfgang; Strom, Robert G

2005-12-01

287

Meteoric Dust as Condensation Nuclei of Small-Mode Particles in the Upper Haze of Venus  

Science.gov (United States)

Observations by the SPICAV/SOIR instruments aboard Venus Express have revealed that the Upper Haze of Venus is populated by two particle modes, as reported by Wilquet et al. (J. Geophys. Res., 114, E00B42, 2009). In this work, we posit that the large mode is made up of cloud particles that have diffused upwards from the cloud deck below, while the smaller mode is generated by the in situ nucleation of meteoric dust. We test this hypothesis by using version 3.0 of the Community Aerosol and Radiation Model for Atmospheres, first developed by Turco et al. (J. Atmos. Sci., 36, 699-717, 1979) and upgraded to version 3.0 by Bardeen et al. (The CARMA 3.0 microphysics package in CESM, Whole Atmosphere Working Group Meeting, 2011). Using the meteoric dust production profile of Kalashnikova et al. (Geophys. Res. Lett., 27, 3293-3296, 2000), the sulfur/sulfate condensation nuclei production profile of Imamura and Hashimoto (J. Atmos. Sci., 58, 3597-3612, 2001), and sulfuric acid vapor production profile of Zhang et al. (Icarus, 217, 714-739, 2012), we numerically simulate a column of the Venus atmosphere from 40 to 100 km above the surface. Our aerosol number density results agree well with Pioneer Venus data from Knollenberg and Hunten (J. Geophys. Res., 85, 8039-8058, 1980), while our gas distribution results match that of Kolodner and Steffes below 55 km (Icarus, 132, 151-169, 1998). The resulting size distribution of cloud particles shows two distinct modes, qualitatively matching the observations of Pioneer Venus. We also observe a third mode in our results with a size of a few microns at 48 km altitude, which appears to support the existence of the controversial third mode in the Pioneer Venus data. This mode disappears if coagulation is not included in the simulation. The Upper Haze size distribution shows two lognormal-like distributions overlapping each other, possibly indicating the presence of the two distinct modes. We test our hypothesis by simulating the atmospheric column with only meteoric dust input, and with only sulfur/sulfate nuclei input. Our results show that the combined Upper Haze size distribution is in essence the sum of the size distributions of these two cases, indicating that it is very likely the two observed modes indeed arise from the different sources mentioned above. We will test the robustness of these results by varying the input rates and sizes of condensation nuclei and the altitude-dependence of the eddy diffusion coefficient in future sensitivity tests.

Gao, P.; Zhang, X.; Crisp, D.; Bardeen, C.; Yung, Y. L.

2012-12-01

288

Orbit Determination of the EnVision D-InSAR mission to Venus  

Science.gov (United States)

EnVision is proposed to the European Space Agency for launch in 2020-22, to detect geological change on Venus and to address key questions from Magellan and Venus Express, particularly: how active is the surface of Venus now? The global distribution of impact craters has been shown (Romeo and Turcotte, 2010) as consistent with a range of resurfacing models, with rates of volcanic and tectonic activity comparable to that of plate interiors on Earth, i.e., perhaps up to 10 mm a-1 in localised tectonic movement and less than 1km3 a-1 (Stofan et al., 2005) in global extrusive activity. Capturing, during the lifetime of a single spacecraft, evidence of an individual volcanic eruption or tectonic movement under the clouds of Venus is only feasible using Differential Interferometric SAR (D-InSAR). D-InSAR is a radar interferometry technique using repeat-pass images of a surface area to measure terrain deformation using radar phase differences at the beginning and end of the observation period. To separate the effects of topography, at least three images are required: a pair closely spaced in time, in which any phase differences are solely attributable to topography, and a third acquired later but from one of the orbital positions used previously. Such technology is now routinely used in earth orbit for terrestrial applications. EnVision is a mission that will use these techniques at Venus to determine the rate and location of geological activity (e.g., tectonics, earthquakes, or volcanic eruptions) on Venus. The EnVision radar will be designed to detect rates of movement as close to the theoretical limit of 1 mm a-1as possible, from a quasi-circular, quasi-polar orbit of 300 km altitude, over a period of up to 10 years. Hence, EnVision must repeat its initial orbit throughout its 10 year mission and in synchronism with surface rotation to within 100 m in all three axes. This paper describes how we propose to determine EnVision's orbit to the necessary degree of accuracy by cost-effective use of the techniques listed in the table.

Cochrane, C. G.; Ghail, R.; Wilson, C. F.; Hall, D.; Mason, P.; EnVision Mission Design Team

2011-12-01

289

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

290

Interpretation of Strain Measurements in Diana Chasma, Venus  

Science.gov (United States)

We have used a new digital technique (usable as a general mapping tool) to explore the spatial variation of extensional tectonic strain within the Diana Chasma region of Venus. The results are consistent with the presence of micro-plates on Venus.

Fowell, M.; Wilson, L.

2001-03-01

291

The morphology and evolution of coronae on Venus  

Science.gov (United States)

The morphology and morphometry of a number of coronae and related features on Venus are discussed with reference to new data from the Magellan spacecraft. The specific features discussed are concentrated in the portion of Venus imaged during about the first three months of Magellan mapping. Sequences of events and basic geophysical processes involved in the formation of these features are inferred.

Squyres, Steven W.; Janes, D. M.; Baer, Gidon; Bindschadler, Duane L.; Schubert, Gerald; Sharpton, Virgil L.; Stofan, Ellen R.

1992-01-01

292

Critical experiments: Recent and future international programmes in VENUS  

International Nuclear Information System (INIS)

This paper outlines the outstanding measurement capabilities of the VENUS critical facility, by giving examples of validation calculations against the two experimental databases VIPEX and VIPO. Then, the two future programmes, called REBUS-BWR and VIPOX, are investigated by calculation. The paper ends by prospecting other possible projects with VENUS. (author)

293

Bimodal distribution of sulfuric acid aerosols in the upper haze of Venus  

Science.gov (United States)

Observations by the SPICAV/SOIR instruments aboard Venus Express have revealed that the upper haze (UH) of Venus, between 70 and 90 km, is variable on the order of days and that it is populated by two particle modes. We use a one-dimensional microphysics and vertical transport model based on the Community Aerosol and Radiation Model for Atmospheres to evaluate whether interaction of upwelled cloud particles and sulfuric acid particles nucleated in situ on meteoric dust are able to generate the two observed modes, and whether their observed variability are due in part to the action of vertical transient winds at the cloud tops. Nucleation of photochemically produced sulfuric acid onto polysulfur condensation nuclei generates mode 1 cloud droplets, which then diffuse upwards into the UH. Droplets generated in the UH from nucleation of sulfuric acid onto meteoric dust coagulate with the upwelled cloud particles and therefore cannot reproduce the observed bimodal size distribution. By comparison, the mass transport enabled by transient winds at the cloud tops, possibly caused by sustained subsolar cloud top convection, are able to generate a bimodal size distribution in a time scale consistent with Venus Express observations. Below the altitude where the cloud particles are generated, sedimentation and vigorous convection causes the formation of large mode 2 and mode 3 particles in the middle and lower clouds. Evaporation of the particles below the clouds causes a local sulfuric acid vapor maximum that results in upwelling of sulfuric acid back into the clouds. In the case where the polysulfur condensation nuclei are small and their production rate is high, coagulation of small droplets onto larger droplets in the middle cloud may set up an oscillation in the size modes of the particles such that precipitation of sulfuric acid “rain” may be possible immediately below the clouds once every few Earth months. Reduction of the polysulfur condensation nuclei production rate destroys this oscillation and reduces the mode 1 particle abundance in the middle cloud by two orders of magnitude. However, it better reproduces the sulfur-to-sulfuric-acid mass ratio in the cloud and haze droplets as constrained by fits to UV reflectivity data. In general we find satisfactory agreement between our nominal and transient wind results and observations from Pioneer Venus, Venus Express, and Magellan, though improvements could be made by incorporating sulfur microphysics.

Gao, Peter; Zhang, Xi; Crisp, David; Bardeen, Charles G.; Yung, Yuk L.

2014-03-01

294

Solar wind-driven thermospheric winds over the Venus North Polar region  

Science.gov (United States)

from the neutral particle imager (NPI) on Venus Express reveals the presence of a persistent +Y (Venus Solar-Oriented) flow of Energetic Neutral Atoms (ENAs) in the Venus polar thermosphere. The overall flow morphology and altitude distribution of ENAs, solar wind H+ (SWH+), and ionospheric O+ imply that SWH+&O+ Charge Exchange (CE) with thermosphere neutrals causes the ENA flow. A dusk-dawn and noon-midnight ENA flux asymmetry is consistent with an asymmetric CE-interaction with higher ENA fluxes in the dayside and dawn (+Y). Model ENA fluxes derived from CE between SWH+&O+ and a model oxygen thermosphere is consistent with NPI data. Adding energy-corrected NPI fluxes and ion fluxes gives essentially constant fluxes of ?1012 part/(m2s) in the altitude range of 200-1200 km. The energy and momentum of the 1-10 km/s ion and ENA flow, induced by solar wind forcing, should have implications for wind patterns in the polar thermosphere above 200 km.

Lundin, R.; Barabash, S.; Futaana, Y.; Holmström, M.; Sauvaud, J.-A.; Fedorov, A.

2014-07-01

295

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 (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

296

Stereo-Derived Magellan Topography, VIRTIS Emissivity Estimates, and Tesserae on Venus  

Science.gov (United States)

The VIRTIS instrument aboard the Venus Express spacecraft has allowed for emissivity estimates of surface materials for a variety of terrains in the southern latitudes of Venus. In the case of tesserae, such as Alpha Regio, emissivity signatures tend to be relatively low and suggest a possibly more evolved, Si-rich composition [Mueller et al, 2008]. If confirmed for tesserae, such a composition would imply crustal recycling, a locally depressed solidus and weaker crust. This would not only help constrain our understanding of tessera formation, whether it is due to crustal contraction or volcanic underplating over 1 Gyr ago, but also the environmental conditions prevailing on Venus then. A more silicic composition would imply a wetter, and therefore cooler (more habitable?) Venus and a dramatically different planet from the one we see today. The significance of such a climatic transition would be profound. Correcting for topography is a key step in deriving emissivity from the surface brightness obtained by VIRTIS at 1.02 ?m. Magellan altimetry suffers from large errors at tessera because the rough relief caused surface returns that were more complex than those in the templates used in the processing of the Magellan altimetry data. We are working to produce a high-accuracy DEM from Magellan stereo SAR coverage for a patch of tessera present that is also present in the VIRTIS dataset. Our technique [Hensley and Shaffer, 1994] uses a hierarchical scheme that applies a 2-D normalized correlation function to determine offsets between two images with formal error calculation, which is of crucial importance in constraining emissivity values. Our preliminary results have lateral resolution of 600 m and vertical resolutions of less than 100 m. First estimates of vertical error lie in the 0 to 40 m range.

Nunes, D. C.; Mitchell, K. L.; Hensley, S.; Shaffer, S.; Mueller, N. T.; Smrekar, S. E.

2013-12-01

297

HIGH-RESOLUTION SATELLITE IMAGING OF THE 2004 TRANSIT OF VENUS AND ASYMMETRIES IN THE CYTHEREAN ATMOSPHERE  

International Nuclear Information System (INIS)

This paper presents the only space-borne optical-imaging observations of the 2004 June 8 transit of Venus, the first such transit visible from Earth since AD 1882. The high-resolution, high-cadence satellite images we arranged from NASA's Transition Region and Coronal Explorer (TRACE) reveal the onset of visibility of Venus's atmosphere and give further information about the black-drop effect, whose causes we previously demonstrated from TRACE observations of a transit of Mercury. The atmosphere is gradually revealed before second contact and after third contact, resulting from the changing depth of atmospheric layers refracting the photospheric surface into the observer's direction. We use Venus Express observations to relate the atmospheric arcs seen during the transit to the atmospheric structure of Venus. Finally, we relate the transit images to current and future exoplanet observations, providing a sort of ground truth showing an analog in our solar system to effects observable only with light curves in other solar systems with the Kepler and CoRoT missions and ground-based exoplanet-transit observations.

298

Coronae on Venus - Morphology, classification, and distribution  

Science.gov (United States)

Venera 15/16 radar images of Venus show two circular features having no analog among the terrestrial planets: 21 coronae, which have a complex interior zone, and 11 corona-like features, which lack the ridge annuli of the coronae. Each of these two groups of features is subdivisible into three classes; coronae may be symmetrical, asymmetrical, and subdued, while corona-like structures are double, irregular, and heart-shaped. The various classes of both types of classes are interpreted as having a similar mode of origin, namely the uplift and volcanism generated by a thermal anomaly at depth, followed by gravitational relaxation.

Pronin, A. A.; Stofan, E. R.

1990-01-01

299

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)

300

Coronae on Venus - Morphology, classification, and distribution  

International Nuclear Information System (INIS)

Venera 15/16 radar images of Venus show two circular features having no analog among the terrestrial planets: 21 coronae, which have a complex interior zone, and 11 corona-like features, which lack the ridge annuli of the coronae. Each of these two groups of features is subdivisible into three classes; coronae may be symmetrical, asymmetrical, and subdued, while corona-like structures are double, irregular, and heart-shaped. The various classes of both types of classes are interpreted as having a similar mode of origin, namely the uplift and volcanism generated by a thermal anomaly at depth, followed by gravitational relaxation. 37 refs

 
 
 
 
301

Venus orogenic belt environments: Architecture and origin  

International Nuclear Information System (INIS)

Orogenic belt environments (Danu, Akna, Freyja, and Maxwell Montes) in Western Ishtar Terra, Venus, display a range of architectural elements, including (from the center of Western Ishtar outward) an inboard plateau (Lakshmi Planum), the linear orogenic belts themselves, outboard plateaus, steep scarps bounding Ishtar, adjacent linear foredeeps and outboard rises, and outboard low-lying volcanic plains. The main elements of the architecture are interpreted to be due to the convergence, underthrusting, and possible subduction of lowland plains at the margins of a preexisting tessera plateau of thicker crust

302

Night OH in the mesosphere of Venus and Earth: A comparative planetology perspective.  

Science.gov (United States)

Satellite measurements of the terrestrial nightside mesosphere from the MLS/Aura MLS instrument show a layer of OH near 82 km. This layer confirms earlier measurements by ground-based UVFTS. The MLS and UVFTS observations measure OH in the lowest vibrational state and are distinct, but related chemically, from vibrationally-excited emission from the OH Meinel bands in the near infrared. The Caltech 1-D KINETICS model has been extended to include vibrational dependence of OH reactions and shows good agreement with MLS OH data and with observations of the Meinel bands [1]. The model shows a chemical lifetime of HOx that increases from less than a day at 80 km to over a month at 87 km. Above this altitude transport processes become an im-portant part of HOx chemistry. The model predicts that ground state OH represents 99% of the total OH up to 84 km. Similarly, Venus airglow emissions detected at wavelengths of 1.40 to 1.49 and 2.6 to 3.14 ?m in limb observations by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express spacecraft are attributed to the OH Meinel band transitions as well [2]. The integrated emission rates for the OH Meinel bands were measured to be 100±40 and 880±90 kR respectively, both peaking at an altitude of 96±2 km near midnight local time for the considered orbit. We use the same Caltech 1-D KINETICS model to model these observations for Venus as was used for the Earth [1] and discuss the conclusions from a comparative planetology perspec-tive, highlighting the similarities and differences between Venus and Earth. References: [1] Pickett H. M., Read W. G., Lee K. K. and Yung Y. L. (2006) GRL, 33, L19808. [2] Piccioni G., Drossart P., Zasova L., Migliorini A., Gérard J.-C., Mills F. P., Shakun A., Garcia Munoz A., Ignatiev N., Grassi D., Cottini V., Taylor F. W., Erard S., and the VIRTIS-Venus Express Technical Team (2008) A and A., 483, L29-L33.

Parkinson, C. D.; Brecht, A.; Bougher, S.; Yung, Y. L.

2009-05-01

303

Transit of Venus Culture: A Celestial Phenomenon Intrigues the Public  

Science.gov (United States)

When Jeremiah Horrocks first observed it in 1639, the transit of Venus was a desirable telescopic target because of its scientific value. By the next transit of Venus in 1761, though, the enlightened public also embraced it as a popular celestial phenomenon. Its stature elevated over the centuries, the transit of Venus has been featured in music, poetry, stamps, plays, books, and art. The June 2004 transit emerged as a surprising global sensation, as suggested by the search queries it generated. Google's Zeitgeist deemed Venus Transit to be the #1 Most Popular Event in the world for that month. New priorities, technologies, and media have brought new audiences to the rare alignment. As the 2012 transit of Venus approaches, the trend continues with publicly accessible capabilities that did not exist only eight years prior. For example, sites from which historic observations have been made are plotted and readily available on Google Earth. A transit of Venus phone app in development will, if fully funded, facilitate a global effort to recreate historic expeditions by allowing smartphone users to submit their observed transit timings to a database for quantifying the Astronomical Unit. While maintaining relevance in modern scientific applications, the transit of Venus has emerged as a cultural attraction that briefly intrigues the mainstream public and inspires their active participation in the spectacle.

Bueter, Chuck

2012-01-01

304

The clouds of Venus. [physical and chemical properties  

Science.gov (United States)

The physical and chemical properties of the clouds of Venus are reviewed, with special emphasis on data that are related to cloud dynamics. None of the currently-popular interpretations of cloud phenomena on Venus is consistent with all the data. Either a considerable fraction of the observational evidence is faulty or has been misinterpreted, or the clouds of Venus are much more complex than the current simplistic models. Several lines of attack are suggested to resolve some of the contradictions. A sound understanding of the clouds appears to be several years in the future.

Young, A. T.

1975-01-01

305

Venus thermospheric response to short-term solar variations  

Science.gov (United States)

The mechanism responsible for cooling the dayside thermosphere of Venus from about 700 K to 300 K (Noll and McElroy, 1972) is examined by analyzing in situ measurements made by the Pioneer Venus Orbiter of the weak response of the thermosphere to short-term solar variations related to 27-day solar rotation. It is shown that, in order to cool the Venus dayside thermosphere to observed levels and to simultaneously explain the weak 27-day variations in the atmosphere, it is necessary to invoke strong CO2 cooling which is controlled principally by collisions of CO2 with atomic oxygen.

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

1992-01-01

306

Venus - Volcanism and rift formation in Beta Regio  

Science.gov (United States)

A new high-resolution radar image of Beta Regio, a Venus highland area, confirms the presence of a major tectonic rift system and associated volcanic activity. The lack of identifiable impact craters, together with the apparent superposition of the Theia Mons volcanic structure on the rift system, suggest that at least some of the volcanic activity occurred in relatively recent geologic time. The presence of topographically similar highland areas elsewhere on Venus (Aphrodite Terra, Dali Chasma, and Diana Chasma) suggests that rifting and volcanism are significant processes on Venus.

Campbell, D. B.; Head, J. W.; Harmon, J. K.; Hine, A. A.

1984-10-01

307

Venus: volcanism and rift formation in Beta regio.  

Science.gov (United States)

A new high-resolution radar image of Beta Regio, a Venus highland area, confirms the presence of a major tectonic rift system and associated volcanic activity. The lack of identifiable impact craters, together with the apparent superposition of the Theia Mons volcanic structure on the rift system, suggest that at least some of the volcanic activity occurred in relatively recent geologic time. The presence of topographically similar highland areas elsewhere on Venus (Aphrodite Terra, Dali Chasma, and Diana Chasma) suggests that rifting and volcanism are significant processes on Venus. PMID:17814347

Campbell, D B; Head, J W; Harmon, J K; Hine, A A

1984-10-12

308

Comparing Characteristics of Polygonal Impact Craters on Mercury and Venus  

International Nuclear Information System (INIS)

Full text: Polygonal impact craters (PICs) are defined as craters, which rims are composed of at least two straight segments. These PICs are often found on terrestrial planets like Mercury, Venus, and Mars and on the Moon. In our current study we compare characteristics of PICs: the numbers, the mean diameters, and the PICs' ages on Mercury and Venus. The surfaces of both planets show significant differences in age - Mercury’s surface is about 4.5 Gyr, but Venus' not more than 1 Gyr old. The age of polygonal impact craters correspond to this difference. (author)

309

VLF emissions in the Venus foreshock - Comparison with terrestrial observations  

Science.gov (United States)

An examination is conducted of ELF/VLF emissions observed in the solar wind upstream of the Venus shock, for the 100 Hz-30 kHz range, using data from the Pioneer Venus Orbiter's electric field detector and magnetometer instruments. Detailed comparisons are made with terrestrial measurements for both the electron and ion foreshocks. The results obtained support the Crawford et al. (1990) identification of the Venus electron foreshock emissions as electron plasma oscillations, whose waves are generated in situ and act to isotropize the electron distributions.

Crawford, G. K.; Strangeway, R. J.; Russell, C. T.

1993-01-01

310

On evidence of a possible volcanism on Venus  

International Nuclear Information System (INIS)

New data obtained During last investigations of Venus and especially results of Venera 11-14 and Pioneer Venus probes (1978-1982) are requesting to look for the mutual interaction of different phenomena on the planet. The suggestion is made that the presence of electrical discharges in the atmosphere close to the surface, the variable density of the submicron haze and peculiarity of cloud microphysics - all listed facts is possible to join together within a hypothesis about volcanic eruptions on the surface of Venus

311

The GUINEVERE project at the VENUS facility  

Energy Technology Data Exchange (ETDEWEB)

The GUINEVERE project is an international project in the framework of IP-EUROTRANS, the FP6 program which aims at addressing the main issues for ADS development in the framework of partitioning and transmutation for nuclear waste volume and radiotoxicity reduction. The GUINEVERE project is carried out in the context of domain 2 of IP-EUROTRANS, ECATS, devoted to specific experiments for the coupling of an accelerator, a target and a subcritical core. These experiments should provide an answer to the questions of online reactivity monitoring, sub-criticality determination and operational procedures (loading, start-up, shutdown,...) in an ADS by 2009-2010. The project has the objective to couple a fast lead core, within the VENUS building operated by the SCK.CEN, with a neutron generator able to work in three different modes: pulsed, continuous and continuous with beam interruptions at the millisecond scale. In order to achieve this goal, the VENUS facility has to be adapted and a modified GENEPI-3C accelerator has to be designed and constructed. The paper describes the main modifications to the reactor core and facility and to the accelerator, which will be executed during the years 2008 and 2009, and the experimental programme which will start in 2009. (authors)

Baeten, P.; Ait Abderrahim, H.; Bergmans, G.; Heyse, J.; Maes, D.; Verboomen, B.; Vermeersch, F.; Vittiglio, G. [SCK.CEN, Boeretang 200, 2400 Mol (Belgium); Aoust, T.; Baylac, M.; Billebaud, A.; Bondoux, D.; Bouvier, J.; De Conto, J.M.; Grondin, D.; Marchand, D.; Micoud, R.; Planet, M. [LPSC-CNRS-IN2P3/UJF/INPG, 53 Avenue des Martyrs. 38026 Grenoble cedex (France); Ban, G.; Gautier, J.M.; Lecolley, F.R.; Lecouey, J.L.; Marie, N.; Merrer, Y.; Steckmeyer, J.C. [LPC Caen, ENSICAEN/Universite de Caen/ CNRS-IN2P3, Caen (France); Dessagne, P.; Gaudiot, G.; Heitz, G.; Kerveno, M.; Ruescas, C. [IPHC-DRS/ULP/CNRS-IN2P3, Strasbourg (France); Laune, B.; Reynet, D. [IPNO, CNRS-IN2P3/UPS, Orsay (France); Granget, G.; Mellier, F.; Rimpault, G. [CEA-Cadarache, 13108 Saint Paul lez Durance (France)

2008-07-01

312

The GUINEVERE project at the VENUS facility  

International Nuclear Information System (INIS)

The GUINEVERE project is an international project in the framework of IP-EUROTRANS, the FP6 program which aims at addressing the main issues for ADS development in the framework of partitioning and transmutation for nuclear waste volume and radiotoxicity reduction. The GUINEVERE project is carried out in the context of domain 2 of IP-EUROTRANS, ECATS, devoted to specific experiments for the coupling of an accelerator, a target and a subcritical core. These experiments should provide an answer to the questions of online reactivity monitoring, sub-criticality determination and operational procedures (loading, start-up, shutdown,...) in an ADS by 2009-2010. The project has the objective to couple a fast lead core, within the VENUS building operated by the SCK.CEN, with a neutron generator able to work in three different modes: pulsed, continuous and continuous with beam interruptions at the millisecond scale. In order to achieve this goal, the VENUS facility has to be adapted and a modified GENEPI-3C accelerator has to be designed and constructed. The paper describes the main modifications to the reactor core and facility and to the accelerator, which will be executed during the years 2008 and 2009, and the experimental programme which will start in 2009. (authors)

313

Morphology of the Venus ultraviolet night airglow  

Science.gov (United States)

Images of the nightside of Venus in the (0,1)delta band of nitric oxide have been obtained by the Pioneer Venus orbiter ultraviolet spectrometer (OUVS). The emission, which is produced by radiative association of N and O, shows a bright spot reaching 5 kR and located at 2 a.m. local solar time just south of the equator. The emitting layer is at 111 + or - 7-km altitude. A one dimensional vertical transport model shows that the hemispheric average brightness of 0.8 kR is consistent with the orbiter neutral mass spectrometer (ONMS) measurements of N and O near 167 km, and that the altitude of the emitting layer is consistent with the eddy mixing model proposed to explain the dayside helium profile measured by the bus neutral mass spectrometer. In the model, N reaches a peak of 7 x 10 to the 8th per cu cm at 114 km, and O reaches a peak of 2.6 x 10 to the 11th per cu cm at 106 km. There is a fair degree of consistency between the ONMS, OUVS, and other airglow measurements, except as regards the local time dependence.

Stewart, A. I. F.; Rusch, D. W.; Bougher, S. W.; Gerard, J.-C.

1980-01-01

314

Geologic processes on Venus: an update  

Science.gov (United States)

Studies of Venera 15 and 16 radar image and altimetry data and reevaluation of Pioneer Venus and earlier Venera data have greatly expanded the perception of the variety and complexity of geologic processes on Venus. PV data have discriminated four highland regions (each different in geomorphic appearance), a large upland rolling plains region, and smaller areas of lowland plains. Two highland volcanic centers were identified that may be presently active, as suggested by their geomorphologic appearance combined with positive gravity anomalies, lightning strike clusters, and a change in SO2 content in the upper atmosphere. Geochemical data obtained by the Venera landers have indicated that one upland area and nearby rolling plains are composed of volcanic rocks, probably basalts or syenites. New Venera radar images of the Ishtar Terra region show folded and/or faulted linear terrain and associated volcanic features that may have been deformed by both compressional and extensional forces. Lowland surfaces resemble the mare basaltic lava flows that fill basins on the Moon, Mars and Earth. Ubiquitous crater like forms may be of either volcanic or impact origin; the origin of similar lunar features was determined by the character of their ejecta deposits.

Masursky, H.

315

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

316

The 2004 Venus Transit: AN European Educational Project  

Science.gov (United States)

On June 8 2004 the planet Venus will pass in front of the disk of the Sun. This rare event (no one alive today has never seen such a transit) reminds us the story of the measurement of the Solar System and will be emphasized next year. We would like to take benefit of this event to organize a worldwide network of schools high schools and scientific centers to make the timing of the event of June 8. More we would like to help pupils students and general public to understand a scientific procedure needing an international collaboration and to be aware of the powerful tool that is a transit (detection of extra solar planets ...). Our plans are to organize a centralized computation of the Astronomical Unit through Internet thanks to individual timings of the event to provide notes and educational material to participantsto encourage the interest to science and to promote a safe observation of the Sun. Contacts: http://www.eso.org/outreach/eduoff/vt-2004/ http://www.imcce.fr/vt2004

Arlot, Jean-Eudes; Rocher, Patrick; Thuillot, William

317

DRAGON analysis of the Venus-2 Mox benchmark  

International Nuclear Information System (INIS)

Before large quantities of plutonium can be used in a systematic way in power reactors, there is a need to assess the quality of the basic nuclear data and of the calculation methods that are used for the safety analysis of reactors under such operating conditions. In order to achieve this goal the NEA Nuclear Science Committee has proposed a 2-dimensional (2-D) and a 3-dimensional (3-D) MOX benchmarks, based on VENUS-2 core measurements. This benchmark has been analyzed with various codes using deterministic (method of characteristics and collision probability method) or Monte Carlo methods. Here, we report the results of our analysis using the code DRAGON with an ENDF/B-V based cross section library. We show that in general DRAGON performs as well as most codes for the 2-D transport calculations. As expected, much larger errors are observed for the 3-D core calculations due to the fact that DRAGON can only perform coarse mesh calculations in these cases. (authors)

318

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

319

Deuterium on Venus - Model comparisons with Pioneer Venus observations of the predawn bulge ionosphere  

Science.gov (United States)

A self-consistent model of the Venus ionosphere in the predawn bulge region where the mass-two ion density is observed to be maximum was prepared in order to examine the question of mass-two ion identification in detail. The model calculations are compared to the Pioneer Venus observations of ion composition and structure in the 153-250 km altitude range. The observed densities of major ions O2(+) and O(+) are used to constrain the source of ionization. Once the source is determined, the density distribution of D(+) and H2(+) is calculated for various values of D and H2 in the atmosphere. It is found that mass-two ion is clearly due to deuterium and that the H2 contribution to the mass-two ion is small, if present at all.

Kumar, S.; Taylor, H. A., Jr.

1985-01-01

320

Geology of the Venus equatorial region from Pioneer Venus radar imaging  

Science.gov (United States)

The data collected by Pioneer Venus have been used to map the broad radar characteristics of the equatorial region on the basis of radar brightness and texture. Seven units are defined and are used to assess the geologic character of the equatorial region. The correspondence between features in the 15 deg region of overlap between Pioneer Venus ans Venera 15/16 images is examined and used to extend units mapped in the northern high latitudes into the equatorial region. Using the properties of rms slope, reflectivity, the scattering behavior of the surface, and topographic signature, seven physiographic units are mapped on the basis of the distribution of the radar units in the equatorial region and are identified by increasing complexity as plains, dark halo plains, upland rises, upland plateaus, interhighland tectonic zones, tectonically segmented linear highlands, and tectonic junctions. The distribution of larger circular structures interpreted as coronae is also examined.

Senske, D. A.

1990-01-01

 
 
 
 
321

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

322

Corrections in the Pioneer Venus sounder probe gas chromatographic analysis of the lower Venus atmosphere  

Science.gov (United States)

Misidentification of two peaks from the Pioneer Venus sounder probe gas chromatograph (SPGC), also formerly known as the LGC, gave rise to quantitative errors in the abundances of oxygen, argon, and carbon monoxide. The argon abundance is estimated at 67 parts per million and that of carbon monoxide at 20 parts per million. At this time, no estimates for the oxygen abundance can be made.

Oyama, V. I.; Carle, G. C.; Woeller, F.

323

Its a Wind, Its a Wave, Its Two Phenomena in One: Jerry Schubert, Superrotation, and the UV Markings on Venus  

Science.gov (United States)

In the early 1970's, ground-based astronomers had already discovered that Ultraviolet (UV) cloud markings on Venus reappeared every 4 days. When radar evidence later revealed a 243-day rotation period for the solid planet, planetary scientists were faced with a quandary: Could the Venus atmosphere really move 60 times as fast as the planet below, or were the apparent movements of the UV features just an illusion caused by propagating waves? The former explanation seemed unlikely - a planet that hardly rotates should generate only a very sluggish circulation. The historical impact of Jerry Schubert's moving flame theory was twofold: It was the forerunner of current thermal tide explanations of the cloud-level superrotation, but it was also the first plausible mechanism for explaining a seemingly inconsistent set of observations. In 1974, Mariner 10 acquired UV images of the Venus clouds at unprecedented levels of detail. Although few have noted it, this began the shift of planetary atmospheric research primarily from the domain of astronomy to that of meteorology. Jerry was among the first scientists to apply terrestrial meteorology to the analysis of planetary data. At that time a young UCLA graduate student with plans to do research on mantle convection, but having flunked the solid earth geophysics section of his departmental comprehensive exam, was gently invited by Jerry to switch to atmospheric science. Jerry suggested that the Venus UV features could be revealing both superrotating winds and planetary-scale waves at the same time, and that we could distinguish the two by looking at motions on different spatial scales. This was my first science research lesson - the complexity of real geophysical systems. Over the next couple of years I was inculcated with Jerry's philosophy of a comprehensive, rigorous approach to research, which manifested itself as a scouring of the literature and the UCLA meteorology faculty to learn about every possible type of planetary-scale wave. The resulting identification of large-scale UV features on Venus as the product of Kelvin and Rossby-type wave motions was validated by extensive Pioneer Venus observations a decade later and remains one of the best examples of the use of terrestrial knowledge to understand other planets.

DelGenio, Anthony

1999-01-01

324

Spaceborne radar studies of the surface of Venus  

Science.gov (United States)

In December 1978 Pioneer Venus 1 went into orbit around Venus and included in its payload was a novel radar mapping instrument. Now, 700 orbits later the radar results have been collected into a series of maps showing for the first time the continents, mountains, and valleys of our sister planet. The radar information suggests a geology intermediate between that of the earth and Mars. Radar has revealed a vast plateau in the northern hemisphere containing a peak which towers 11 km above the surrounding plain. However, such features are rare with most of the surface comprised of a gentle rolling plain. The spacecraft radar results reveal no evidence of earth type plate tectonics on Venus. The rift areas and great trenches which criss-cross the terrestrial ocean basins are absent. It is tentatively concluded that Venus has evolved geologically much as the earth but not to the same degree.

Nozette, S.

1980-10-01

325

Exploration Targets for a Mission Concept with Multiple Venus Gliders  

Science.gov (United States)

Six targets have been identified for exploration with guided aerosondes that glide to their targets with high precision and conduct atmospheric and surface observations addressing all three of the major Venus scientific goals identified by VEXAG.

Cutts, J. A.; Nunes, D. C.; Mitchell, K. L.; Senske, D. A.; Pauken, M. T.; Matthies, L. H.; Tokamaru, P.

2014-05-01

326

VENUS-7 plutonium recycling benchmark, results of AREVA NP  

International Nuclear Information System (INIS)

Solutions for the NBA VENUS-7 plutonium recycling benchmark are presented in this paper. Various few-group 3D transport calculations were performed with pin cell homogenized cross sections, mostly generated by CASMO-4 ('L-Lib' based on ENDF/B data). In addition, also 2D solutions with a finer energy group structure are presented. In general the calculated reactivity effects agree well with the measured ones. A comparison with other VENUS configurations indicates that the reactivity of the MOX pins with Inconel 800 cladding seems to be slightly under-estimated. The calculated fission rates in the VENUS-7/1 configurations show good agreement with the measured fission rate traverses. This is also confirmed by a VENUS-9/0 analysis where preliminary measured fission rate data were available also at the water reflector, displaying the strong peaking at this reflector boundary. (authors)

327

Textured Lava Flows on Earth, Mars, and Venus  

Science.gov (United States)

Textured lava flows at Sabancaya volcano, Peru reveal morphologies similar to textured lava flows on Mars and Venus. Analysis of the flows at Sabancaya may provide an understanding of the rheological properties of the extraterrestrial flows.

Warner, N. H.; Gregg, T. K. P.; Bulmer, M. H.

2001-03-01

328

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

329

Enabling Venus In Situ Missions Using Mechanically Deployed Aerodynamic Decelerator  

Science.gov (United States)

Trade study and optimal solutions for guided entry and aerocapture for Venus in situ missions using Mechanically Deployed Aerodynamic Decelerator to reduce peak deceleration loads, as well as peak heat fluxes.

Saikia, S. J.; Saranathan, H.; Grant, M. J.; Longuski, J. M.

2014-06-01

330

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

331

Venus' Chasmata and Earth's Spreading Centers: A Topographic Comparison  

Science.gov (United States)

Like the Earth, Venus has a global rift system, which has been cited as evidence of tectonic activity, despite the apparent lack of Earth-style plate tectonics. Both systems are marked by large ridges, usually with central grabens. On Earth, the topography of the rifts can be modeled well by a cooling half-space and the spreading of two divergent plates. The origin of the topographic signature on Venus, however, remains enigmatic. Venus' rift zones (termed "chasmata") can be fit by four great circle arcs extending 1000s of kilometers. The Venus chasmata system measures 54,464 km, which when corrected for the smaller size of the planet, nearly matches the 59,200-km total length of the spreading ridges determined for Earth. As on Earth, the chasmata with the greatest relief (7 km in just a 30-km run for Venus) represent the most recent tectonic activity. We use topographic profiles to look for well-understood terrestrial analogs to Venusian features. Focusing on mid-ocean ridge systems on Earth, we examine the variation along individual ridges, or rises, due to the gradual change in spreading rate (and thus cooling times). We then analyze the difference between fast and slow ridges, and propose that this technique may also be used to pick plate boundaries along spreading centers (SAM/AFR vs. NAM/AFR, e.g.). These profiles are then compared to those for Venus' rifts. Topographic profiles are based on the Magellan (Venus) and ETOPO5 (Earth) data sets. Long wavelength features appear similar to spreading systems on Earth, suggesting a deep, thermal cause. Short wavelength features, such as rift troughs and constructional edifices, are quite different, however, as expected from the vastly different surface conditions. Comparison of topographic profiles from Venus and Earth may lend insight into tectonic features and activity on our sister planet.

Stoddard, P. R.; Jurdy, D. M.

2008-12-01

332

VENUS international programmes: A contribution for MOX use in LWRs  

Energy Technology Data Exchange (ETDEWEB)

The VENUS critical facility is used for making benchmarks for neutron codes. Nowadays mainly LWR programmes concerning MOX fuel are executed. In this paper the VENUS facility is described together with the basic parameters that are measured. Some results of former programmes are given (VIP, VIPO) and the first comparison between experimental and calculation results are given that have been obtained from the VIPEX programme. (author)

Vandermeer, K.; Marloye, D.; Minsart, G.; D' hondt, P.; Abderrahim, H.A. [SCK CEN, B-2400 Mol (Belgium); Maldague, Th.; Basselier, J. [Belgonucleaire, B-1200 Brussels (Belgium)

1998-07-01

333

VENUS international programmes: A contribution for MOX use in LWRs  

International Nuclear Information System (INIS)

The VENUS critical facility is used for making benchmarks for neutron codes. Nowadays mainly LWR programmes concerning MOX fuel are executed. In this paper the VENUS facility is described together with the basic parameters that are measured. Some results of former programmes are given (VIP, VIPO) and the first comparison between experimental and calculation results are given that have been obtained from the VIPEX programme. (author)

334

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)

335

A new radar determination of the spin vector of Venus  

Science.gov (United States)

Two radar observations of a set of three relatively small features on the surface of Venus have facilitated a refined determination of the spin vector of Venus. The period is found to be 243.019 + or 0.014 days, while the obliquity is 177.22 + or - 0.18 deg. The effects of deviations from exact sphericity on the interpretation of the measurements are discussed at length and the question of resonance with earth is reexamined.

Zohar, S.; Goldstein, R. M.; Rumsey, H. C.

1980-01-01

336

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

337

Asteroid 2012 XE133, a transient companion to Venus  

CERN Document Server

Apart from Mercury that has no known co-orbital companions, Venus remains as the inner planet that hosts the smallest number of known co-orbitals, 2: (322756) 2001 CK32 and 2002 VE68. Both objects have absolute magnitudes 18 < H < 21 and were identified as Venus co-orbitals in 2004. Here, we analyze the orbit of the recently discovered asteroid 2012 XE133 with H = 23.5 mag to conclude that it is a new Venus co-orbital currently following a transitional trajectory between Venus' Lagrangian points L5 and L3. The object could have been a 1:1 librator for several thousand years and it may leave the resonance with Venus within the next few hundred years, after a close encounter with the Earth. Our calculations show that its dynamical status as co-orbital, as well as that of the 2 previously known Venus co-orbitals, is controlled by the Earth-Moon system with Mercury playing a secondary role. The 3 temporary co-orbitals follow rather chaotic but similar trajectories with e-folding times of order of 100 yr. Ou...

Marcos, C de la Fuente

2013-01-01

338

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.

339

The oxygen nightglow emissions of Venus: vertical distribution and role of collisional quenching  

Science.gov (United States)

Three-body recombination of atomic oxygen produces O2 molecules excited in different electronic states such as a 1?g, b 1 ? g+, A 3 ? u+, c 1 ? uand A' 3?u, each with a specific quantum efficiency. When they radiate, optical transitions are observed in a wide range of wavelengths extending from the ultraviolet to the near infrared. In planetary atmospheres, spontaneous radiative deexcitation compete with collisional quenching with ambient molecules and atoms. As a consequence, the corresponding airglow emission profiles may significantly differ from each other in brightness and altitude of the emitting layer. We model the volume emission rates and limb profiles of the O2 Atmospheric Infrared (a 1?-X 3 ? ), Herzberg I (A 3 ?-X 3 ? ), Herzberg II (c 1 ? -X 3 ? ), Chamberlain (A' 3?-a 1?) bands expected on the Venus night side. The quenching rates are taken from laboratory and observational planetary data and we apply two different methods to determine the oxygen and CO2 density profiles. One is based on recent analysis of data collected by instruments on board the Venus Express mission. The second one uses a one-dimensional chemical-diffusive model where the free parameters are the strength of turbulent transport and the downward flux of O atoms. Both approaches indicate that the calculated intensities of each transition range over several orders of magnitude and that differences are expected in the altitude of the maximum emission. These predictions will be compared with VIRTIS/Venus Express limb observations, which make it possible to derive the vertical distribution of the O2 emissions in the visible and infrared. These measurements suggest that no difference is observed between the altitude of the peak of the IR Atmospheric and Herzberg II bands. Conclusions will be drawn about the validity of the current set of quenching coefficients used in the model.

Gérard, J.-C.; Soret, L.; Migliorini, A.; Piccioni, G.; Drossart, P.

2012-04-01

340

A model of the Venus ionosphere  

Science.gov (United States)

Results of model calculations of the Venus ionosphere from 120 to 300 km are presented. The chemical scheme and reaction rates used are the same as given by Kumar and Hunten (1974) except that the electron temperature dependence of the dissociative recombination rates is taken into account. Calculations are made for low and high atomic oxygen models in which the O/CO2 ratios are 0.4% and 4% respectively at 140 km, and the results agree well in shape and magnitude with the Mariner 5 and 10 occultation results in the chemically controlled region. Reasonable agreement is obtained at higher altitudes if diffusive equilibrium and high vertical flow velocities (10 km/s) are assumed as upper boundaries for the Mariner 5 and 10 conditions respectively, although solar wind-ionosphere interactions are considered to be the controlling mechanism for the Mariner 10 results.

Nagy, A. F.; Liu, S. C.; Donahue, T. M.; Atreya, S. K.; Banks, P. M.

1975-01-01

 
 
 
 
341

A mechanism for the Venus thermospheric superrotation  

Science.gov (United States)

A physical mechanism for in situ forcing of the Venus thermospheric superrotation is developed, which is in accord with the bulk of the constraining observations. Saturation of small- to medium-scale internal gravity waves in the thermosphere can supply the necessary accelerations of the mean flow if the waves have predominantly large westward phase speeds, characteristic of the wind speeds in the upper clouds. Several scenarios for wave forcing are examined, and the Lindzen-Holton parameterization is used to derive wave-induced accelerations of the mean flow. The results are compared to the VTGCM model, which uses a similar wave drag parameterization with an ad hoc (empirically based) asymmetry parameter to model the superrotation.

Alexander, M. J.

1992-01-01

342

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

343

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

344

Analysis of the VENUS-3 experiments  

International Nuclear Information System (INIS)

The results of applying a hybrid superposition-synthesis calculational method to a mockup of a three-dimensional geometry involving a partial length shield assembly at the VENUS-3 facility in Mol, Belgium, are described. Comparisons of transport calculations using the method and many measurements involving nickel, indium, and aluminum dosimeters indicate agreement usually to within measurement uncertainties estimated at around 5%, if effects of inaccuracies in the dosimeter cross sections are minimized and proper orientation of the coordinate system used in the synthesis procedure is observed. These conclusions suggest a solution to the problem of predicting pressure vessel fluence in reactors modified by these partial-length shield assemblies may already exist. 7 refs., 2 figs., 1 tab

345

Venus - Maxwell Montes and Cleopatra Crater  

Science.gov (United States)

This Magellan full-resolution image shows Maxwell Montes, and is centered at 65 degrees north latitude and 6 degrees east longitude. Maxwell is the highest mountain on Venus, rising almost 11 kilometers (6.8 miles) above mean planetary radius. The western slopes (on the left) are very steep, whereas the eastern slopes descend gradually into Fortuna Tessera. The broad ridges and valleys making up Maxwell and Fortuna suggest that the topography resulted from compression. Most of Maxwell Montes has a very bright radar return; such bright returns are common on Venus at high altitudes. This phenomenon is thought to result from the presence of a radar reflective mineral such as pyrite. Interestingly, the highest area on Maxwell is less bright than the surrounding slopes, suggesting that the phenomenon is limited to a particular elevation range. The pressure, temperature, and chemistry of the atmosphere vary with altitude; the material responsible for the bright return probably is only stable in a particular range of atmospheric conditions and therefore a particular elevation range. The prominent circular feature in eastern Maxwell is Cleopatra. Cleopatra is a double-ring impact basin about 100 kilometers (62 miles) in diameter and 2.5 kilometers (1.5 miles) deep. A steep-walled, winding channel a few kilometers wide breaks through the rough terrain surrounding the crater rim. A large amount of lava originating in Cleopatra flowed through this channel and filled valleys in Fortuna Tessera. Cleopatra is superimposed on the structures of Maxwell Montes and appears to be undeformed, indicating that Cleopatra is relatively young.

1991-01-01

346

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