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1

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

2

Education and Public Outreach using Venus Express  

Science.gov (United States)

Nearly two decades after NASA’s Magellan radar mission to Venus, its atmosphere and surface is being investigated with new instruments by the Venus Express spacecraft from orbit. It was launched by the European Space Agency (ESA) on 11 November 2005, and has been orbiting Venus since April 2006. This mission provides an opportunity to focus on comparative planetary meteorology for education and public outreach efforts. We present an inquiry-based approach for informal and formal learning audiences by comparing atmospheric states of Venus and Earth using data available from Earth weather satellites and Venus Express. In the context of a middle or a high school curriculum, the science themes of Venus Express mission provide many connections to the themes of the National Science Education Standards. For the general audiences, Venus presents many of its mysteries such as its super rotation in the form of a giant hemispheric vortex akin to a hurricane, its deep atmosphere with sulfuric acid clouds, and the huge greenhouse effect concepts that are familiar to many. More than a dozen US scientists are participating in the Venus Express mission with support from NASA.

Pertzborn, Rosalyn A.; Limaye, S. S.; Pi, H. Y.

2006-12-01

3

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

4

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

5

MESSENGER and Venus Express Observations of the Solar Wind Interaction with Venus: A Dual Spacecraft Study  

Science.gov (United States)

At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 krn) during its second flyby of Venus en route to its 201 1 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. Pioneer Venus Orbiter measurements have shown that this interaction affects the upper atmosphere and ionosphere down to altitudes of - 150 km. Here we present an initial overview of the MESSENGER observations during the - 4 hrs that the spacecraft spent within 10 planet radii of Venus and, together with Venus Express measurements, examine the influence of solar wind plasma and interplanetary magnetic field conditions on the solar wind interaction at solar minimum.

Slavin, James A.; Acuna, M. H.; Anderson, B. J.; Barabash, S.; Benna, M.; Boardsen, S. A.; Fraenz, M.; Gloeckler, G.; Gold, R. E.; Ho, G. C.; Korth, H.; Krimigis, S. M.; McNutt, R. L., Jr.; Raines, J. M.; Sarantos, M.; Solomon, S. C.; Zhang, T.; Zurbuchen, T. H.

2007-01-01

6

Foreshock ULF waves at Venus from Venus Express  

Science.gov (United States)

There exist large amplitude ultralow frequency (ULF) waves in the ion foreshock of the Venusian bow shock. With the magnetic field observations from Venus Express between 2006 and 2011, an abundance of quasi-monochromatic ULF waves (with frequency below and far enough from the local proton cyclotron frequency) have been identified by an automatic survey. One objective is to derive the relative occurrence of such foreshock waves and proton cyclotron waves associated to local pickup ions linked to exospheric hydrogen previously reported. The transverse part of the power spectrum dominates the parallel part for these foreshock ULF waves. The periods found are in the range from ~20 to ~40 seconds and most of the waves display left-hand polarization in the spacecraft frame. Taking into account the Doppler-shift by the high-speed solar wind, they may be right-hand polarized in the solar wind frame. These characteristics suggest that they are RH mode waves generated in the ion foreshock region by the field aligned beam protons reflected at the shock.

Shan, Lican; Mazelle, Christian; Lu, Quanming; Delva, Magda; Zhang, Tielong

2014-05-01

7

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

8

The Surface of Venus After VIRTIS on Venus Express: Laboratory Analogs and the Venus Emissivity Mapper  

Science.gov (United States)

A combination of laboratory work and remote sensing will be able to determine the large-scale compositional variations of the surface of Venus and will provide valuable input for any landing site selections for future Venus lander missions.

Ferrari, S.; Helbert, J.; Maturilli, A.; Dyar, D. M.; Mueller, N.; Elkins-Tanton, L. T.

2014-05-01

9

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

10

Models of the global cloud structure on Venus derived from Venus Express observations  

Science.gov (United States)

Spatially-resolved near-infrared spectra from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express have been used to derive improved models of the vertical structure and global distribution of cloud properties in the southern hemisphere of Venus. VIRTIS achieved the first systematic, global mapping of Venus at wavelengths within transparency windows in the 1.6-2.6 ?m range, which are sensitive on the nightside to absorption by the lower and middle cloud layers of thermally-emitted radiation from the hot lower atmosphere ( Taylor, F.W., Crisp, D., Bézard, B. [1997]. Venus II: Geology, Geophysics, Atmosphere, and Solar Wind Environment, pp. 325-351). The cloud model used to interpret the spectra is based on previous work by Pollack et al. (Pollack, J., Dalton, J., Grinspoon, D., Wattson, R., Freedman, R., Crisp, D., Allen, D., Bézard, B., de Bergh, C., Giver, L. [1993]. Icarus 103, 1-42), Grinspoon et al. (Grinspoon, D.H., Pollack, J.B., Sitton, B.R., Carlson, R.W., Kamp, L.W., Baines, K.H., Encrenaz, T., Taylor, F.W. [1993]. Planet. Space Sci. 41, 515-542) and Crisp (Crisp, D. [1986]. Icarus 67, 484-514), and assumes a composition for the cloud particles of sulfuric acid and water, with acid concentration as a free parameter to be determined. Other retrieved parameters are the average size of the particles and the altitude of the cloud base in the model. Latitudinal variation in the atmospheric temperature structure was incorporated using data from the Venus Radio Science experiment (VeRa). Values are estimated initially using wavelength pairs selected for their unique sensitivity to each parameter, and then validated by comparing measured to calculated spectra over the entire wavelength range, the latter generated using the NEMESIS radiative transfer and retrieval code (Irwin, P.G.J., Teanby, N.A., de Kok, R., Fletcher, L.N., Howett, C.J.A., Tsang, C.C.C., Wilson, C.F., Calcutt, S.B., Nixon, C.A., Parrish, P.D. [2008]. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150). The sulfuric acid concentration in the cloud particles is found to be higher in regions of optically thick cloud. The cloud base altitude shows a dependence on latitude, reaching a maximum height near -50°. The increased average particle size near the pole found by Wilson et al. (Wilson, C.F., Guerlet, S., Irwin, P.G.J., Tsang, C.C.C., Taylor, F.W., Carlson, R.W., Drossart, P., Piccioni, G. [2008]. J. Geophys. Res. (Planets) 113, E12) and the finding of spatially variable water vapor abundance at35-40 km altitude first reported by Tsang et al. (Tsang, C.C.C., Wilson, C.F., Barstow, J.K., Irwin, P.G.J., Taylor, F.W., McGouldrick, K., Piccioni, G., Drossart, P., Svedhem, H. [2010]. Geophys. Res. Lett. 37, L02202) are both confirmed. The implications of these improved descriptions of cloud structure and variability for the chemistry, meteorology, and radiative energy balance on Venus are briefly discussed.

Barstow, J. K.; Tsang, C. C. C.; Wilson, C. F.; Irwin, P. G. J.; Taylor, F. W.; McGouldrick, K.; Drossart, P.; Piccioni, G.; Tellmann, S.

2012-02-01

11

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

12

Venus  

Science.gov (United States)

On 8 June 2004 Venus will pass in front of the Sun as seen from the Earth. Many people will watch the small dark dot cross the solar disk, but will they stop to think about Venus as a real place? In this article we discuss what we know about Venus, what it looks like from orbit, what you might see if you were on the surface and future plans for…

Martin, Paula; Stofan, Ellen

2004-01-01

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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

14

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

Directory of Open Access Journals (Sweden)

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

L. Guicking

2010-04-01

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Improved calibration of SOIR/Venus Express spectra.  

Science.gov (United States)

The SOIR instrument on board the ESA Venus Express mission has been operational since the insertion of the satellite around Venus in April 2006. Since then, it has delivered high quality IR solar occultation spectra of the atmosphere of Venus. The different steps from raw spectra to archived data are described and explained in detail here. These consist of corrections for the dark current and for the non-linearity of the detector; removing bad pixels, as well as deriving noise. The spectral calibration procedure is described, along with all ancillary data necessary for the understanding and interpretation of the SOIR data. These include the full characterization of the AOTF filter, one of the major elements of the instrument. All these data can be found in the ESA PSA archive. PMID:24103989

Vandaele, Ann Carine; Mahieux, Arnaud; Robert, Séverine; Berkenbosch, Sophie; Clairquin, Roland; Drummond, Rachel; Letocart, Vincent; Neefs, Eddy; Ristic, Bojan; Wilquet, Valérie; Colomer, Frédéric; Belyaev, Denis; Bertaux, Jean-Loup

2013-09-01

16

Boundary layer in the Venus ionosheath. Evidence from the Venus express plasma data  

International Nuclear Information System (INIS)

Complete text of publication follows. Measurements conducted with the ASPERA-4 instrument in the Venus Express spacecraft further support the presence of a plasma transition located at the flanks of the Venus ionosheath downstream from the bow shock and that had been inferred in the data obtained from previous missions at Venus. Across this transition there are sudden changes in the plasma properties including lower speed and density values as well as higher temperatures of the shocked solar wind in its downstream side. In addition there is evidence that the planetary ion component becomes enhanced in the downstream side of that transition with fluxes that lead to significantly larger densities than those measured in the upstream side. That plasma transition has been interpreted as representing the outer extent of a viscous boundary layer formed by the transport of solar wind momentum to the Venus upper ionosphere, and the ASPERA-4 data provide for the first time information on the kinetic properties of the planetary ion population that is seen to stream mostly in the solar wind direction but with values that remain smaller than those of the solar wind. From the analysis of a collection of orbits with evidence of that transition it has been possible to derive that its position varies significantly with the downstream distance from the planet. Furthermore it has also been found that the momentum flux of the dominant component of planetary ions measured downstream from the plasma transition can be accounted for from the momentum flux of the solar wind protons. In most cases the latter quantity represents 80 to 90 % of the incident momentum flux of the solar wind and implies that there is an approximate balance in the momentum between both populations as would result from the transport of solar wind momentum.

2009-08-23

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Solar Tides in the winds of the southern polar region of Venus using VIRTIS-M/Venus Express images  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of the solar tides on the winds at the top of the clouds in Venus has been studied using cloud tracking technique applied to the Venus Express/VIRTIS-M images taken at wavelengths of 3.8 and 5.0 ?m. Both these wavelengths probe about the same altitude on the clouds top, allowing for the first time to retrieve winds in the dayside and nightside simultaneously. The dataset included

Peralta, Javier; Luz, David; Berry, David; Piccioni, Giuseppe; Drossart, Pierre; Hueso, Ricardo; Sa?nchez-lavega, Agustin

2011-01-01

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Morphology and dynamics of Venus oxygen airglow from Venus Express/Visible and Infrared Thermal Imaging Spectrometer observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Images obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)-M channel instrument onboard Venus Express have been used to retrieve maps and apparent motions of the O[SUB]2[/SUB] ([SUP]1[/SUP]Delta) infrared nightglow on Venus at 1.27 mum. The nightglow distribution is highly inhomogeneous with the regions of brightest emission generally located at low latitudes near the midnight meridian. Unexpectedly some orbits show also intense airglow activity over the south polar reg...

Hueso, R.; Sa?nchez-lavega, A.; Piccioni, G.; Drossart, P.; Ge?rard, Jean-claude; Khatuntsev, I.; Zasova, L.; Migliorini, A.

2008-01-01

19

High latitude gravity waves at the Venus cloud tops as observed by the Venus Monitoring Camera on board Venus Express  

Science.gov (United States)

High resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) allow studying small-scale dynamical phenomena at the cloud tops (˜62-70 km altitude) including features like wave trains. A systematic visual search of these waves was performed; more than 1500 orbits were analyzed and wave patterns were observed in more than 300 images. Four types of waves were identified in VMC images on the base of their morphology: long, medium, short and irregular type waves. With the aim to characterize the wave types and their possible excitation source, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, orientation, and wavelength of each wave. The long type waves appear as long and narrow straight features extending more than a few hundreds kilometers and with wavelengths between 7 and 17 km. Medium type waves exhibit irregular wavefronts extending more than 100 km and with wavelengths in the range 8-21 km. Short wave packets have a width of several tens of kilometers and extend to few hundreds kilometers and are characterized by smaller wavelengths (3-16 km). Irregular wave fields appear to be the result of wave interference. The waves are often identified in all VMC filters and are mostly found in the cold collar region at high latitudes (60-80°N) and are concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet. The high speed of the Venus Express spacecraft close to the pericentre does not allow to measure phase speed of waves due to the short temporal interval between image pairs. The lack of information on phase velocities does not allow us to establish with absolute confidence the nature of these waves. However, by comparing the morphology and properties of the wave features observed in VMC images to those seen by previous observations it is reasonable to assume that the waves studied here are gravity waves.

Piccialli, A.; Titov, D. V.; Sanchez-Lavega, A.; Peralta, J.; Shalygina, O.; Markiewicz, W. J.; Svedhem, H.

2014-01-01

20

Venus winds at cloud level from VIRTIS during the Venus Express mission  

Science.gov (United States)

The Venus Express (VEX) mission has been in orbit to Venus for almost four 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 our latest results on the analysis of the global atmospheric dynamics at these cloud levels using a large selection over the full VIRTIS dataset. We will show the atmospheric zonal superrotation at these levels and the mean meridional motions. The zonal winds are very stable in the lower cloud at mid-latitudes to the tropics while it shows different signatures of variability in the upper cloud where solar tide effects are manifest in the data. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present almost null global meridional motions at all latitudes but with particular features traveling both northwards and southwards in a turbulent manner depending on the cloud morphology on the observations. A particular important atmospheric feature is the South Polar vortex which might be influencing the structure of the zonal winds in the lower cloud at latitudes from the vortex location up to 55°S. Acknowledgements This work has been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07.

Hueso, Ricardo; Peralta, Javier; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Piccioni, Giuseppe; Drossart, Pierre

2010-05-01

 
 
 
 
21

Venus  

Science.gov (United States)

This NASA (National Aeronautics and Space Administration) planet profile provides data and images of the planet Venus. These data include planet size, orbit facts, distance from the Sun, rotation and revolution times, temperature, atmospheric composition, density, surface materials and albedo. Images with descriptions of the planet include many surface features such as halos, craters, ridges, troughs, ticks and other volcano types, lava flows and other tectonic features. Some of the main region images show areas such as Selu Corona, Bright Plains, Gula Mons, Sif Mons, the Ovda Region, Danu Mountains, Akna Mountains, Crater Mead, Golubkina, Lavinia Region, the Eastern Lakshmi Region, Corona Derceto, and Sacajawea Patera. All of these images are from the Magellan Spacecraft.

22

Cloud level winds from the Venus Express Monitoring Camera imaging  

Science.gov (United States)

Six years of continuous monitoring of Venus by European Space Agency's Venus Express orbiter provides an opportunity to study dynamics of the atmosphere our neighbor planet. Venus Monitoring Camera (VMC) on-board the orbiter has acquired the longest and the most complete so far set of ultra violet images of Venus. These images enable a study the cloud level circulation by tracking motion of the cloud features. The highly elliptical polar orbit of Venus Express provides optimal conditions for observations of the Southern hemisphere at varying spatial resolution. Out of the 2300 orbits of Venus Express over which the images used in the study cover about 10 Venus years. Out of these, we tracked cloud features in images obtained in 127 orbits by a manual cloud tracking technique and by a digital correlation method in 576 orbits. Total number of wind vectors derived in this work is 45,600 for the manual tracking and 391,600 for the digital method. This allowed us to determine the mean circulation, its long-term and diurnal trends, orbit-to-orbit variations and periodicities. We also present the first results of tracking features in the VMC near-IR images. In low latitudes the mean zonal wind at cloud tops (67 ± 2 km following: Rossow, W.B., Del Genio, A.T., Eichler, T. [1990]. J. Atmos. Sci. 47, 2053-2084) is about 90 m/s with a maximum of about 100 m/s at 40-50°S. Poleward of 50°S the average zonal wind speed decreases with latitude. The corresponding atmospheric rotation period at cloud tops has a maximum of about 5 days at equator, decreases to approximately 3 days in middle latitudes and stays almost constant poleward from 50°S. The mean poleward meridional wind slowly increases from zero value at the equator to about 10 m/s at 50°S and then decreases to zero at the pole. The error of an individual measurement is 7.5-30 m/s. Wind speeds of 70-80 m/s were derived from near-IR images at low latitudes. The VMC observations indicate a long term trend for the zonal wind speed at low latitudes to increase from 85 m/s in the beginning of the mission to 110 m/s by the middle of 2012. VMC UV observations also showed significant short term variations of the mean flow. The velocity difference between consecutive orbits in the region of mid-latitude jet could reach 30 m/s that likely indicates vacillation of the mean flow between jet-like regime and quasi-solid body rotation at mid-latitudes. Fourier analysis revealed periodicities in the zonal circulation at low latitudes. Within the equatorial region, up to 35°S, the zonal wind show an oscillation with a period of 4.1-5 days (4.83 days on average) that is close to the super-rotation period at the equator. The wave amplitude is 4-17 m/s and decreases with latitude, a feature of the Kelvin wave. The VMC observations showed a clear diurnal signature. A minimum in the zonal speed was found close to the noon (11-14 h) and maxima in the morning (8-9 h) and in the evening (16-17 h). The meridional component peaks in the early afternoon (13-15 h) at around 50°S latitude. The minimum of the meridional component is located at low latitudes in the morning (8-11 h). The horizontal divergence of the mean cloud motions associated with the diurnal pattern suggests upwelling motions in the morning at low latitudes and downwelling flow in the afternoon in the cold collar region.

Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Limaye, S. S.; Markiewicz, W. J.; Almeida, M.; Roatsch, Th.; Moissl, R.

2013-09-01

23

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

24

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

25

Venus and Mars plasma environments. A comparative analysis of IMA (ASPERA-4, ASPERA-4) mass spectrometer data onboard Venus Express and Mars Express.  

Science.gov (United States)

First data from the IMA mass spectrometer onboard of the Venus Express (VEX) mission came on May 15 2006 almost 2 years later of the first data from the same instrument onboard of Mars Express (MEX). Now we understand relatively well the Martian plasma environment, and we can compare it with the first data from Venus Express. To do that we extracted similar parts of MEX and VEX orbits and performed an analysis of the mass and energy spectra of planetary ions and ions of magnetosheath in the similar spatial points of the planet environments. Present paper shows the obvious differences between Venusian and Martian "magnetospheres".

Fedorov, A.; Barabash, S.; Sauvaud, J.-A.; Lundin, R.; Aspera

26

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

27

The evolution of co-orbiting material in the orbit of 2201 Oljato from 1980 to 2012 as deduced from Pioneer Venus Orbiter and Venus Express magnetic records  

Science.gov (United States)

Asteroid 2201 Oljato passed through perihelion inside the orbit of Venus near the time of its conjunction with Venus in 1980, 1983, and 1986. During those three years, many interplanetary field enhancements (IFEs) were observed by the Pioneer Venus Orbiter (PVO) in the longitude sector where the orbit of Oljato lies inside Venus' orbit. We attribute IFEs to clouds of fine-scale, possibly highly charged dust picked up by the solar wind after an interplanetary collision between objects in the diameter range of 10-1000 m. We interpret the increase rate in IFEs at PVO in these years as due to material in Oljato's orbit colliding with material in, or near to, Venus' orbital plane and producing a dust-anchored structure in the interplanetary magnetic field. In March 2012, almost 30 yr later, with Venus Express (VEX) now in orbit, the Oljato-Venus geometry is similar to the one in 1980. Here, we compare IFEs detected by VEX and PVO using the same IFE identification criteria. We find an evolution with time of the IFE rate. In contrast to the results in the 1980s, the recent VEX observations reveal that at solar longitudes in which the Oljato orbit is inside that of Venus, the IFE rate is reduced to the level even below the rate seen at solar longitudes where Oljato's orbit is outside that of Venus. This observation implies that Oljato not only lost its co-orbiting material but also disrupted the "target material," with which the co-orbiting material was colliding, near Venus.

Lai, Hairong; Russell, Christopher T.; Wei, Hanying; Zhang, Tielong

2014-01-01

28

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

29

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 (90-120km 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 4.3µm, extending from 90 to 120km altitude, and of night-side O2 emission extending from 95 to 100km. The CO2 emission peak occurs at ~115km and varies with solar zenith angle over a range of ~10km. This confirms previous modelling, and permits the beginning of a systematic study of the variability of the emission. The O2 peak emission happens at 96km+/-1km, 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.

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; Ficai Veltroni, Iacopo; 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

2007-11-01

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South polar dynamics of the Venusian atmosphere from VIRTIS/Venus Express mapping in the thermal range  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report on measurements of Venus cloud velocities from VIRTIS/Venus Express observations of the south polar region of Venus. Cloud tracking has been performed using a method of automated digital correlation. Tracking has been performed on pairs of monochromatic VIRTIS images selected mainly in the 5 ?m window, but also at 1.74, 2.3, 3.93 micrometers. Wind measurements from vector retrievals based on automated feature tracking show high variability, indicating the presence of important tran...

Luz, David; Berry, David L.; Peralta, Javier; Drossart, Pierre; Piccioni, Giuseppe

2010-01-01

31

A Comparative Analysis of the Venus and Mars Magnetotail ion Flows. First Data From the IMA (ASPERA-4, Venus Express) Mass Spectrometer Compared With Mars Express.  

Science.gov (United States)

The first data from the IMA mass spectrometer aboard the Venus Express (VEX) probe arrived on May 15 2006, almost 2 years after the first data from an identical instrument aboard Mars Express (MEX). Now we understand relatively well the Martian plasma environment, and we can compare it with the new data from Venus. For this we extracted data from similar parts of the MEX and VEX orbits, and analysed the mass and energy spectra of planetary and magnetosheath ions at comparable locations of the planetary environments. We can see that the magnetotails of both planets consists of several plasma regimes which are spatially organized in the reference frame defined by the interplanetary magnetic and electric fields. The central part of the tail (Plasma Sheet) contains ions of planetary origin, accelerated to about 1keV, and the periphery of the tail is filled with dispersed plasma structures which include a very low energy component. The geometry of the tails and the ion compositions differ at Mars and Venus. Present work shows results from case studies and a statistical study.

Fedorov, A.; Barabash, S.; Sauvaud, J.; Zhang, T.; Lundin, R.; Ferrier, C.; Mazelle, C.

2006-12-01

32

Future Exploration of Venus: Opportunities and Challenges  

Science.gov (United States)

The successful fly-by of Venus by Mariner 2 began a half century of planetary exploration. During the last three decades Venus has been explored by orbiters, probes and balloons and even opportunistic fly-bys of VeGA, Galileo, Cassini and MESSENGER spacecraft, and currently ESA's Venus Express orbiter is returning data from its 24-hour highly eccentric polar orbit and JAXA's Akatsuki spacecraft awaits orbit insertion around Venus in 2015 or 2016. Recently the Planetary Science Decadal Survey (2013-2022) conducted by the US National Academies recommended a flagship mission to Venus. The current and future budget scenarios for NASA indicate that such a mission can be realized through international partnerships and collaborations. It is useful therefore to examine the scientific observations of Venus that have not yet been obtained and explore the current technological capabilities that have been developed and can be useful for Venus missions. These include long lived balloons, more efficient electric power generation, Unmanned Aerial Vehicles (UAV), surface seismometry stations and others. NASA's Venus Exploration Analysis Group (VEXAG) provides a forum for the international Venus community to consider international collaborations and scientists are invited to participate in the discussions.

Limaye, Sanjay; Svedhem, Håkan; Nakamura, Masato; Zasova, Ludila; Kiran Kumar, A. S.; Bullock, Mark; Wilson, Colin

2012-07-01

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MESSENGER and Venus Express Observations of the Near-tail of Venus: Magnetic Flux Transport, Current Sheet Structure, and Flux Rope Formation  

Science.gov (United States)

At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 km) during its second flyby of Venus en route to its 2011 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. We present MESSENGER observations of the near-tail of Venus with emphasis on determining the time scales for magnetic flux transport, the structure of the cross-tail current sheet at very low altitudes (approx. 300 to 1000 km), and the nature and origin of a magnetic flux rope observed in the current sheet. The availability of the simultaneous Venus Express upstream measurements provides a unique opportunity to examine the influence of solar wind plasma and interplanetary magnetic field conditions on this planet's solar wind interaction at solar minimum.

Slavin, James A.; Boardsen, S. A.; Sarantos, M.; Acuna, M. H.; Anderson, B. J.; Barabash, S.; Benna, M.; Fraenz, M.; Gloeckler, G.; Gold, R. E.; Ho, G. C.; Korth, H.; Krimigis, S. M.; McNutt, R. L., Jr.; Raines, J. M.; Solomon, S. C.; Zhang, T.-L.; Zurbuchen, T. H.

2008-01-01

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Atomic oxygen distribution in the Venus mesosphere from observations of O[SUB]2[/SUB] infrared airglow by VIRTIS-Venus Express  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This VIRTIS instrument on board Venus Express has collected spectrally resolved images of the Venus nightside limb that show the presence of the (0,0) band of the Deltag1-->Sigmag3 infrared atmospheric system of O[SUB]2[/SUB] at 1.27 mum. The emission is produced by three-body recombination of oxygen atoms created by photodissociation of CO[SUB]2[/SUB] on the dayside. It is consistently bright so that emission limb profiles can be extracted from the images. The vertical distribution of O[SUB]...

Ge?rard, Jean-claude; Saglam, Adem; Piccioni, Giuseppe; Drossart, Pierre; Montmessin, Frank; Bertaux, Jean-loup

2009-01-01

35

Mars and Venus - The Express Way : Evolution and Heritage in Flexi Type Missions Concerning Model Philosophy and Environmental Test Design  

Science.gov (United States)

Mars Express is the first example of ESA's "Flexible Missions", a new and more economic way of building space science missions based on maximum use of existing technology that is either 'off-the-shelf' or technology that has already been developed for other programs. The high level of recurrence in the design, the re-use of existing hardware and the implementation of new project management practices made possible to Mars Express to meet the objective of shortening the time from original concept to launch, being built unusually quickly to meet its narrow launch window in June 2003. The objective of being assembled, fully tested and prepared for launch in a record time, 30% faster than other comparable missions and with reduced financial funding, could be achieved only with a thorough re- thinking of the model philosophy and environmental test design. The encouraging results obtained with Mars Express are the basis of the AIV program of the second ESA's Flexible Mission, Venus Express. Highly recurrent of Mars Express, even if with important peculiarities due to the different mission and planetary environment, this Project will benefit of the qualifications achieved on its predecessor, allowing a single module approach where the AIT campaign will start directly on the PFM. This paper presents the innovative concepts implemented in the definition of Mars Express Model Philosophy and Environmental Test campaigns, showing the influence of the adopted solutions on the in-flight performances. An overview of Venus Express Test Campaign is also given, focusing on the effects of the previous experience and the lessons learned as well as the peculiarities of the new mission.

Rustichelli, S.; McCoy, D.; Florino, T.; Pereira, J.; Pendaries, M.

2004-08-01

36

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, Japan, Taiwan and China.

2009-04-11

37

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

38

Japanese Venus Mission, VCO: A Challenge to Answer an Outstanding Question of Planetary Science  

Science.gov (United States)

We plan a mission, called ``Venus Climate Orbiter'', in which we carry out a detailed and long-term monitoring observation of the mysterious atmosphere of the Earth's twin planet. The mission is scheduled to put a spacecraft, equipped with imaging cameras and plasma instruments, into Venus' orbit in 2009 after a cruise from the Earth by means of a M-V launching vehicle of ISAS. An outstanding and the most fundamental question regarding Venus is how its environment has been differentiated from the Earth's in spite of nearly identical dimensions of these twins. This should not be the question only to Venus but also a general question to every planet. One key to answer the question is believed to be obtained through the study of a generation and maintenance mechanism of so-called super-rotation of the Venusian atmosphere, a high-speed wind which encircles the planet in only 4 Earth days. Although the phenomenon itself has been well known, the mechanism of it remains still unsolved primarily because there has been no 3-D information of the atmospheric circulation which underlies an opaque cloud layer. The VCO mission is designed to acquire data sets essential to answer the above question. The imaging cameras utilize a recently-developed (and powerful) technique to remote probe the atmosphere, snapshots of Venus' night side in several atmospheric windows in the near IR region (1--2.4 ? m). This allows us to monitor the motion of cloud patches well below the visible cloud layer, our previous limit of visibility. Using a set of narrow-band filters, we image cloud features at several altitudes with spatial resolutions of 15--20 km at the sub-spacecraft point, good enough to achieve a few m/s of accuracy in determining the wind velocity. The column densities of carbon monoxide and water vapor will be also measured, yielding additional information on the atmospheric circulation. With the plasma instruments, on the other hand, we explore the upper atmosphere and the ionosphere. Observations of neutral and charged particle escapes from the planetary atmosphere are especially important, because of their significant influence on the atmospheric evolution as well as a general interest in the particle acceleration process including the solar-wind interactions. The cameras are expected to be active even in the cruising phase because it will be a unique opportunity to observe the infrared sky in a wide field of view with very low background level. The resonance structure of zodiacal dust disk rippled by the twins of our planetary system and its radial profile will be demonstrated by series of observations at different radial distances from the Sun. The VCO mission, which by itself is unique, will be valuable as part of an international collaborative work in a comprehensive study of Venus with several spacecraft, which include Lovoisier, Venus Express, and Ishtar missions of ESA, and Vespar mission of NASA. The basic concept, a mission overview, plus some details of VCO (including the onboard instruments) will be presented.

Satoh, T.; Nakamura, M.; Ueno, M.; Iwagami, N.; Sugita, S.; Kasaba, Y.; Abe, T.; Imamura, T.; Oyama, K.; WG, V.

2002-05-01

39

Meeting Venus  

Science.gov (United States)

On 2-3 June 2012, the University of Tromsoe hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsoe for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the scale of the solar system in the eighteenth century. The site of the conference was the Nordnorsk Vitensenter (Science Centre of Northern Norway), which is located at the campus of the University of Tromsoe. After the conference, participants were invited to either stay in Tromsoe until the midnight of 5-6 June, or take part in a Venus transit voyage in Finnmark, during which the historical sites Vardoe, Hammerfest, and the North Cape were to be visited. The post-conference program culminated with the participants observing the transit of Venus in or near Tromsoe, Vardoe and even from a plane near Alta. These Proceedings contain a selection of the lectures delivered on 2-3 June 2012, and also a narrative description of the transit viewing from Tromsoe, Vardoe and Alta. The title of the book, Meeting Venus, refers the title of a play by the Hungarian film director, screenwriter and opera director Istvan Szabo (1938-). The autobiographical movie Meeting Venus (1991) directed by him is based on his experience directing Tannhauser at the Paris Opera in 1984. The movie brings the story of an imaginary international opera company that encounters a never ending series of difficulties and pitfalls that symbolise the challenges of any multicultural and international endeavour. As is evident from the many papers presented in this book, Meeting Venus not only contains the epic tales of the transits of the seventeenth, eighteenth and nineteenth centuries, it also covers the conference participants' encounter with "Venus on the Sun" in historical archives as well as face-to-face at several locations in the Troms and Finnmark counties.

Sterken, Christiaan; Aspaas, Per Pippin

2013-06-01

40

Venus Geochemistry: Progress, Prospects, and New Missions - Program and Abstract Volume.  

Science.gov (United States)

Topics covered include: In-Situ Aerial Exploration of Venus by Balloon - Science Objectives and Mission Architecture; Geochemical Aspects of the Geological History of Venus; The Role of Sulfur in Detecting Recent Climate Change on Venus; Venus Geochemical...

2009-01-01

 
 
 
 
41

Plasma boundaries around Venus  

Science.gov (United States)

We use data of the ASPERA-4 ion and electron spectrometers onboard Venus Express to define the location and shape of bow shock and magnetic barrier at Venus and their dependence on solar wind pressure and radiation. We compare our results with those of the Pioneer Venus Orbiter and discuss implications for atmospheric escape. We also discuss the differences to similar observations made by the ASPERA-3 instrument for the Martian plasma evironment.

Martinecz, C.; Fraenz, M.; Woch, J.; Krupp, N.; Dubinin, E.; Roussos, E.; Barabash, S.; Lundin, R.

42

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

43

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

44

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

45

In-Situ Exploration of Venus: Major Science Objectives, Investigations, and Mission Platform Options  

Science.gov (United States)

In-situ missions to Venus have been recommended by both the 2011 and 2003 Decadal Studies of the NRC and have been proposed numerous times to NASA's Discovery and New Frontiers programs as well as to ESA's Cosmic Vision program. Such missions would revolutionize our understanding of Venus, as they address key questions of Venus's origin, evolution, and current state via high precision measurements of (1) noble gases and their isotopes, and (2) reactive trace gases and aerosol associated with Venus's active photo- and thermo-chemistry and sulfur cycle, including components potentially responsible for the poorly-understood uv-absorbing haze layer. Fundamental questions, as promoted in recent VEXAG documents, include: (1) Did Venus, Mars, and Earth have a common origin? (2) What roles did comets from the outer Solar System play in delivering volatiles to Venus? (3) Did Venus once have and lose a global ocean? (4) How much has Venus outgassed, and what is the current rate of outgassing, particularly of sulfur, the major driver of Venus clouds? and (5) Through the deposition of energy within them, what role do these clouds play in (a) driving the cloud-level thermal structure and (b) generating and maintaining the super-rotating zonal windfield that covers the globe? Fundamental answers could be uniquely provided through in-situ sampling via mass spectrometry of the noble gases and their isotopes - in particular of the 8 stable Xe isotopes, the bulk abundances of Kr, and the 3 isotopes of Ne. Measurements of the relative abundances of the light isotopes of N, O, H, S and O, by, for example, tunable laser spectrometry, would provide additional insights into Venus's origin, surface outgassing and planetary escape. Such measurements could be performed by probes, landers, or balloons. On descent through the uv-absorbing layer and the surrounding H2SO4 cloud, each of these platforms could explore both the absorber and sulfur-cycle-associated reactive species and aerosols, thus addressing VEXAG desires for enhanced understanding of Venus' chemical cycles, aerosol properties, and radiative transfer. On descent to the surface, probes and landers can provide vertical profiles of temperatures and species abundances, as well as provide near-surface measurements of sulfur isotopes and trace sulfuric gases indicative of outgassing. Additional major in-situ goals dealing with Venus's global circulation and local dynamics can be addressed by a balloon platform floating within the convective middle cloud near ~55-km altitude. Drifting over a wide range of latitudes and all times-of-day and longitudes, such a floating platform could accurately measure (1) motions in all three dimensions - zonal, meridional, and vertical, including motions associated with convection and gravity waves, (2) simultaneous measurements of cloud particle size, their parent molecules, the local temperature, and vertical velocity, to study cloud formation/dissipation processes, and (3) the power and frequency of local lightning. Altogether, such in-situ measurements would potentially revolutionize our understanding of (1) Venus's circulation, including the role of waves and solar cloud heating in powering the planet's poorly-understood super-rotation, (2) Venus's sulfur cycle, key to Venus's current climate, and (3) how Earth's neighbor formed and evolved over the aeons.

Baines, K. H.; Limaye, S. S.; Hall, J. L.; Atreya, S. K.; Bullock, M. A.; Crisp, D.; Grinspoon, D. H.; Mahaffy, P. R.; Russell, C. T.; Webster, C. R.; Zahnle, K. J.

2013-12-01

46

Detailed expression pattern of aldolase C (Aldoc) in the cerebellum, retina and other areas of the CNS studied in Aldoc-Venus knock-in mice.  

Science.gov (United States)

Aldolase C (Aldoc, also known as "zebrin II"), a brain type isozyme of a glycolysis enzyme, is expressed heterogeneously in subpopulations of cerebellar Purkinje cells (PCs) that are arranged longitudinally in a complex striped pattern in the cerebellar cortex, a pattern which is closely related to the topography of input and output axonal projections. Here, we generated knock-in Aldoc-Venus mice in which Aldoc expression is visualized by expression of a fluorescent protein, Venus. Since there was no obvious phenotypes in general brain morphology and in the striped pattern of the cerebellum in mutants, we made detailed observation of Aldoc expression pattern in the nervous system by using Venus expression in Aldoc-Venus heterozygotes. High levels of Venus expression were observed in cerebellar PCs, cartwheel cells in the dorsal cochlear nucleus, sensory epithelium of the inner ear and in all major types of retinal cells, while moderate levels of Venus expression were observed in astrocytes and satellite cells in the dorsal root ganglion. The striped arrangement of PCs that express Venus to different degrees was carefully traced with serial section alignment analysis and mapped on the unfolded scheme of the entire cerebellar cortex to re-identify all individual Aldoc stripes. A longitudinally striped boundary of Aldoc expression was first identified in the mouse flocculus, and was correlated with the climbing fiber projection pattern and expression of another compartmental marker molecule, heat shock protein 25 (HSP25). As in the rat, the cerebellar nuclei were divided into the rostrodorsal negative and the caudoventral positive portions by distinct projections of Aldoc-positive and negative PC axons in the mouse. Identification of the cerebellar Aldoc stripes in this study, as indicated in sample coronal and horizontal sections as well as in sample surface photos of whole-mount preparations, can be referred to in future experiments. PMID:24475166

Fujita, Hirofumi; Aoki, Hanako; Ajioka, Itsuki; Yamazaki, Maya; Abe, Manabu; Oh-Nishi, Arata; Sakimura, Kenji; Sugihara, Izumi

2014-01-01

47

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

1987-01-01

48

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

Energy Technology Data Exchange (ETDEWEB)

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.

Saunders, R.S.

1987-03-01

49

Expression microarrays in equine sciences.  

Science.gov (United States)

Microarrays have become an important research tool for life science researchers. Expression microarrays are capable of profiling the gene expression pattern of tens of thousands of genes in a single experiment. It appears to be the platform of choice for parallel gene expression profiling. Various equine-specific gene expression microarrays have been generated and used. However, homologous microarrays are not yet commercially available for the horse. An alternative is the use of heterologous microarrays, mainly microarrays specific for mice or humans. Although the use of microarrays in equine research is still in its infancy, gene expression microarrays have shown their potential in equine research. This review presents the previous, current and potential use of expression microarrays in equine research. PMID:19027176

Ramery, Eve; Closset, Rodrigue; Art, Tatiana; Bureau, Fabrice; Lekeux, Pierre

2009-02-15

50

Winds and cloud morphology in the southern polar region of Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spinning on average 60 times faster than the surface, the atmosphere of Venus is superrotational, a state in which the averaged angular momentum is much greater than that corresponding to co-rotation with the solid globe. The rapid mean flow, which is main- tained by momentum transports in the deep atmo- sphere, presents a puzzle to the atmospheric and plan- etary sciences[1]. After previous missions revealed a bright polar feature at the north pole[9, 10], the Venus Express spacecraft discov...

Luz, David; Berry, David L.; Peralta, Javier; Piccioni, Giuseppe; Drossart, Pierre; VIRTIS-Venus Express Team

2010-01-01

51

Venus Anadyomene  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This painting is of Venus Anadyomene, or Venus rising out of the sea at her birth. Barry's interpretation follows descriptions of Apelles' (the 4th century BC, Greek artist) celebrated work of the same subject in which Venus wrings out her wet hair. He also used other classical texts for various details including Lucretius' 'De Rerum Natura' and Hesiod's 'The Theogony' which suggested the dispersing clouds, calm sea, rainbow, mating birds, and the plants which spring up at the touch of her fo...

Barry, James

1983-01-01

52

Venus Atmospheric Maneuverable Platform (VAMP)  

Science.gov (United States)

We have explored a possible new approach to Venus upper atmosphere exploration by applying recent Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (vehicle capable of carrying science payloads to explore the Venus upper atmosphere. In 2012 we initiated a feasibility study for a semi-buoyant maneuverable vehicle that could operate in the upper atmosphere of Venus. In this presentation we report results from the ongoing study and plans for future analyses and prototyping to advance and refine the concept. We will discuss the overall mission architecture and concept of operations from launch through Venus arrival, orbit, entry, and atmospheric science operations. We will present a strawman concept of VAMP, including ballistic coefficient, planform area, percent buoyancy, inflation gas, wing span, vehicle mass, power supply, propulsion, materials considerations, structural elements, subsystems, and packaging. The interaction between the VAMP vehicle and the supporting orbiter will also be discussed. In this context, we will specifically focus upon four key factors impacting the design and performance of VAMP: 1. Feasibility of and options for the deployment of the vehicle in space 2. Entry into the Venus atmosphere, including descent profile, heat rate, total heat load, stagnation temperature, control, and entry into level flight 3. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance (aerodynamics, power required vs. power available, propulsion, speed, percent buoyancy), performance sensitivity to payload weight 4. Science payload accommodation, constraints, and opportunities We will discuss interdependencies of the above factors and the manner in which the VAMP strawman's characteristics affect the CONOPs and the science objectives. We will show how the these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals 2 and 3. We will also discuss how the VAMP platform itself can facilitate some of these science measurements.

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

2013-12-01

53

Ice On Venus  

Science.gov (United States)

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

54

A teardrop-shaped ionosphere at Venus in tenuous solar wind  

Science.gov (United States)

A very tenuous solar wind regime, following a series of large coronal mass ejections, impacted Venus during early August, 2010. STEREO-B downstream from Venus observed that the solar wind density at Earth orbit dropped to ˜0.1#/cm3 and persisted at this value over 1 day. A similar low value was observed at Earth in 1999 and has attracted comprehensive attention (Lazarus, A.J., 2000. Solar physics: the day the solar wind almost disappeared. Science 287, 2172-2173.), especially its consequences on Earth's ionosphere and magnetosphere (Lockwood, M., 2001. Astronomy: the day the solar wind nearly died. Nature 409, 677-679.). We now have an opportunity to examine the response of Venus' ionosphere to such a tenuous solar wind. After Venus Express spacecraft entered the ionosphere near the terminator, it continuously sampled O+ dominated planetary plasma on the nightside till it left the optical shadow region when Venus Express was located at 2 RV (Venus' Radii) to the Venus center and 1.1 RV to the Sun-Venus line. Moreover, the O+ speed was lower than the gravitational escape speed. We interpret this low-speed O+ as a constituent of the extended nightside ionosphere as a consequence of long-duration (18 h) tenuous solar wind, because the very low dynamic pressure enhances the source and reduces the sink of the nightside ionosphere. Though the full extent of the nightside ionosphere is not known due to the limitation of spacecraft's trajectory, our results suggest that the global configuration of Venus' ionosphere could resemble a teardrop-shaped cometary ionosphere.

Wei, Y.; Fraenz, M.; Dubinin, E.; Coates, A. J.; Zhang, T. L.; Wan, W.; Feng, L.; Angsmann, A.; Opitz, A.; Woch, J.; Barabash, S.; Lundin, R.

2012-12-01

55

Chasing Venus  

Science.gov (United States)

Periodically the planet Venus passes directly between Earth and the Sun, appearing as a small black dot on the Sun's disk. Since astronomers first became aware of them in 1631, these "transits of Venus" have fascinated astronomers because of their rarity and their potential to help scientists measure the solar system. The expeditions that set out to observe transits from remote locations paved the way for a new era of scientific exploration - yet never managed to unlock the transits' secrets. "Chasing Venus" tells the story of astronomers' pursuit of this phenomenon, through rare books and articles written on the subject over the last four centuries. The exhibit also marks the sixth observed transit of Venus, in June 2004.

2009-05-20

56

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

57

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

58

Venus volcanism  

Energy Technology Data Exchange (ETDEWEB)

Eruption styles and processes on the planets are known to be strongly influenced by such factors as gravity, temperature, and atmospheric characteristics. The ascent and eruption of magma on Venus in the current Venus environment must take into account the influence of the extreme surface temperatures (650-750 K) and pressures (40-100 bars) on these processes. Conditions on Venus will reduce the subsurface exsolution of volatiles and lead to a reduction of the possible range of explosive interactions with the atmosphere. Pyroclastic eruptions will be severely inhibited and continuous magma disruption by gas bubble growth may not occur at all unless the exsolved magma volatile content exceeds several weight percent. Recent US and USSR spacecraft missions and Earth-based radar observations are beginning to provide a view of the range of Venus volcanic features, including domes, cones, calderas, shields, and flows. The nature of many lava flows suggests that numerous eruptions have effusion rates exceeding common terrestrial rates and lying more in the range inferred for lunar basaltic flood eruptions (10/sup 4/-10/sup 5/m/sup 3//s). Shield volcanoes are often wide but are low (<2 km elevation) relative to those on Mars and the Earth. Volcano height depends in part on the depth of origin of the magma and the density contrast between the lava and the rocks between the source and the surface, both of which may be different on Venus. Correlations between volcanic style and tectonic structure are emerging.

Head, J.W.

1985-01-01

59

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.

60

The Venus oxygen nightglow and density distributions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Observing Venus nightglow is a key tool to understand the composition and the dynamics of its atmosphere. Results deduced from observations can be implemented to produce a data model of Venus atmosphere. For instance, the Visible and Infra-Red Thermal Imaging Spectrometer (VIRTIS) instrument on board the Venus Express spacecraft is very useful to analyze the O2(a1?) nightglow at 1.27 µm in the Venus mesosphere. Nadir observations can be used to create a statistical map of the emission on Ve...

Soret, Lauriane; Ge?rard, Jean-claude; Montmessin, Franck; Piccioni, Giuseppe; Drossart, Pierre; Bertaux, Jean-loup

2010-01-01

 
 
 
 
61

The Venus environment  

International Nuclear Information System (INIS)

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

1982-08-01

62

Venusian ion populations and bow shock as seen by the ASPERA-4 ion instrument on Venus Express  

Science.gov (United States)

Introduction We examine ion populations at Venus. Previous models use magnetic crossing points to derive the bow shock position. The current work uses data from the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) [1] instrument to measure ion populations and derive a bow shock position at Venus. Instrumentation The ASPERA-4 instrument flies onboard Venus Express (VEX) and is comprised of five different detectors (Barabash et al 2006 [1]). A neutral particle detector and analyser, an electron spectrometer and the Ion Mass Analyser (IMA) (ref). This paper uses the IMA instrument for all its data and an explanation of the specifications is required. The instrument is a top hat electrostatic analyser; it runs through voltages to scan look angles and also acceptance energies. In one look direction it scans through 96 different energy values before changing to the next. A full scan of all look directions and energies takes 192 seconds. Data Collection All data is weighed dependant upon its probability of the spacecraft measuring at a particular point and when fitted produces a value of 1.24 RV, somewhat closer distance for the sub solar point than previous authors - see figure 1. We separate the data according to slow or fast solar wind and not the similarities and differences in the results derived. The inbound and outbound bow shock crossings were taken by inspection of 106 orbits between November 2006 and February 2007. Any orbits where the crossing point was not clear or with data missing were ignored. The occupational probability is found from orbital mechanics. By setting up a grid and deriving the amount of time it takes to cross each square the probability as a whole can then be determined. Ion distribution plots Two dimensional maps of the ions are produced and the bow shock model overplotted to verify its accuracy, as shown in figure 3. The test of the bow shock is to place it upon real data and examine the fit. To do this ion distribution plots are created and have the bow shock model placed upon them. The maps are shown in fig 8 and comprise 6 months of data from VEX in 2007. The count rates of all spectra of every orbit were stored and binned into a grid system. Each box in the grid being averaged from all values placed into it. The results were then smoothed and the maps created for individual species and plot types. Fig 3 shows maps for hydrogen ions in the x-y plane and in cylindrical coordinates signed with y. This plot is the same as a standard cylindrical plot but the r value is positive if y is positive and negative if y is negative. Effect of Coronal mass Ejections The HI imager on STEREO is able to image Coronal mass Ejections (CME) in the inner Solar System. In a recent paper, Roullard et al 2008 [2] have considered a CME observed to impact Venus, and used in situ measurements to examine the response of the magnetosphere. The plots in figure4 show the measured ion response to this and an earlier CME. We will examine the ion signatures in detail. Acknowledgements We acknowledge the contributions of the entire Aspera 4 team: S. Barabash, R. Lundin, H. Andersson, K. Brinkfeld, A. Grigoriev, H. Gunell, M. Holmström, M. Yamauchi, K. Asamura, P. Bochsler, P. Wurz, R. Cerulli-Irelli, A. Mura, A. Milillo, M. Maggi, S. Orsini, A. J. Coates, D. R. Linder, D. O. Kataria, C. C. Curtis, K. C. Hsieh, B. R. Sandel, R. A. Frahm, J. R. Sharber, J. D. Winningham, M. Grande, E. Kallio, H. Koskinen, P. Riihelä, W. Schmidt, T. Säles, J. U. Kozyra,N. Krupp, J. Woch,.S. Livi, J. G., Luhmann, S. McKenna-Lawlor, E. C. Roelof, D. J. Williams, J.-A. Sauvaud, A. Fedorov, and J.-J. Thocaven. References [1] S. Barabash, R. Lundin, H. Andersson, K. Brinkfeld, A. Grigoriev, H. Gunell, M. Holmström, M. Yamauchi, K. Asamura, P. Bochsler, P. Wurz, R. Cerulli-Irelli, A. Mura, A. Milillo, M. Maggi, S. Orsini, A. J. Coates, D. R. Linder, D. O. Kataria, C. C. Curtis, K. C. Hsieh, B. R. Sandel, R. A. Frahm, J. R. Sharber, J. D. Winningham, M. Grande, E. Kallio, H. Koskinen, P. Riihelä, W. Schmidt, T. Säles, J. U. Kozyra,N. Krupp

Grande, M.; Whittaker, I.; Guymer, G.; Barabash, S.

2008-09-01

63

The Venus Radar Mapper (VRM) mission  

Science.gov (United States)

The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface of Venus using a synthetic aperture mapping radar. The spacecraft is scheduled to be launched in April 1988 using a Shuttle-Centaur G combination. The spacecraft arrives at Venus in late July 1988 and begins its mapping mission which lasts for one Venus rotation or 243 days. This paper describes the VRM mission at its present state of design. The science objectives and project constraints are described. Key features of the spacecraft system and radar system are discussed. The interplanetary and mapping orbit design are covered. Navigation strategy is explained, including trajectory maneuvers and mapping phase orbit determination. Finally, the mapping sequences to optimize planet coverage are described.

Cutting, E.; Kwok, J. H.; Mohan, S. N.

1984-01-01

64

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

65

Geology of Venus planet  

International Nuclear Information System (INIS)

Nowadays data of geological-morphological analysis of the Venus surface obtained as a result of the analysis of ''Venus-15 and -16'' space probes images are presented. The specific features of the Venus relief - plains, mountains, craters are considered and geological-morphological map of the Venus survey zone by ''Venus-15 and -16'' space probes is presented. Data on potassium, uranium, torium and main rockforming elements in the Venus surface rocks by the data of ''Venus-8;-9;-10;-13 and -14'' and ''Vega-1 and -2'' space probes are given

1986-01-01

66

Velocities of Venus clouds derived from VIRTIS observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Retrograde superrotation is a well known feature of the atmosphere of Venus, with Venus’ cloud tops rotating in only 4.4 days, much faster than the 243-day rotation period of the solid globe. A good characterization of the circulation of the venusian atmosphere is essential in order to understand the mechanisms controlling superrota- tion. VIRTIS, onboard ESA’s Venus Express, is one of the most flexible instruments for such a characterization. The VIRTIS-M imaging spectrometer, operating ...

Luz, David; Berry, David L.; Piccioni, Giuseppe; Drossart, Pierre

2008-01-01

67

The Planet Venus  

Science.gov (United States)

This resource covers early and modern views of Venus; the general features of Venus; its cloud layer, including high velocity winds, the absence of water vapor, and the different wavelengths used to analyze the Venusian atmosphere; properties of the Venusian atmosphere; a runaway greenhouse effect (where oceans would boil and rocks would sublimate), caused by radiation trapping by greenhouse gases; surface features of Venus, including different hemispheric views, mountains, volcanoes, lava flows, rift valleys and meteor craters; and a comparison of Venus and Earth.

2007-05-12

68

Future Venus Exploration: Mission Venera-D  

Science.gov (United States)

Venera-D is a strategic mission to explore Venus, included in the Russian Federal Space Program 2016-2025. Venera-D mission is in the phase A now. The Venera-D Roscosmos/IKI - NASA Joint Science Definition Team has been formed in February 2014.

Zasova, L. V.; Ignatiev, N. I.; Gerasimov, M. V.

2014-05-01

69

High Temperature Mechanisms for Venus Exploration  

Science.gov (United States)

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

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

70

Venus: discoveries and problems  

International Nuclear Information System (INIS)

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

1980-01-01

71

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 (470"0C) 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

1986-05-01

72

Salt tectonics on Venus  

Energy Technology Data Exchange (ETDEWEB)

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 (470/sup 0/C) 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.

Wood, C.A.; Amsbury, D.

1986-05-01

73

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

74

Venus sky light polarization  

Energy Technology Data Exchange (ETDEWEB)

The computations of the polarization degree and intensity of radiation near the Venus surface are described. A purely gaseous plane layer with physical parameters corresponding to those of the lower 20 km of the Venus atmosphere has been chosen as a model of the subcloud atmosphere. It is shown that the radiation field near the surface is practically determined only by the amount of absorbing components in the lower atmospheric layers. The conclusion is drawn that simultaneous polarimetric and photometric experiments should make it possible to determine the absorbing components in the Venus atmosphere, such as water vapour and finely dispersed aerosol.

Loskutov, V.M.; Minin, I.N.; Selyakov, K.I.

1984-10-01

75

The atmosphere of Venus  

International Nuclear Information System (INIS)

The last expeditions to Venus carried out in 1978 - American (Pioneer-Venus) and Soviet (Venera 11 and 12) - brought much news and it is interesting to sum up the results just now. The contents of this review are: 1. The planet Venus - basic astronomical data. 2. Chemical composition. 3. Temperature, pressure, density (from 0 to 100 km). 4. Clouds. 5. Thermal regime and greenhouse effect. 6. Dynamics. 7 Chemical processes. 8. Upper atmosphere. 9. Origin and evolution. 10. Problems for future studies. (orig./WL)

1981-01-01

76

Transits of Venus and Mercury as muses  

Science.gov (United States)

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

Tobin, William

2013-11-01

77

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the solar wind induced oxygen ion escape from Venus' upper atmosphere and the Venus Express observations of the Venus-solar wind interaction by the HYB-Venus hybrid simulation code. We compare the simulation to the magnetic field and ion observations during an orbit of nominal upstream conditions. Further, we study the response of the induced magnetosphere to the emission of planetary ions. The hybrid simulation is found to be able to reproduce the main observed regions of the Venusi...

Jarvinen, R.; Kallio, E.; Janhunen, P.; Barabash, S.; Zhang, T. L.; Pohjola, V.; Sillanpa?a?, I.

2009-01-01

78

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.

79

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

80

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

 
 
 
 
81

Resurfacing on Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The resurfacing evolution of Venus has beene valuated through Monte Carlo simulations. Forthefirst time, the size sof volcanic flows in the models were generated using the frequency–size distribution of volcanic units measured on Venus. Anon-homogeneous spatial generation of volcanic units was included in the models reproducing the Beta–Alta–Themis volcanic anomaly. Crater modification is simulated using a 3 Dapproach. The final number of modified craters and randomnes sof...

Romeo Briones, Ignacio; Turcotte, Donald L.

2010-01-01

82

The European Space Agency's Planetary Science Archive (PSA)  

Science.gov (United States)

The Planetary Science Archive (PSA), available at http://archives.esac.esa.int/psa, represents the central repository for all science data returned by ESA's planetary missions. PSA provides support for data producers and end users of the data, aiming to maximize its long-term usability and access after the mission itself is complete. The repository contains data from all of ESA's planetary explorers, from Giotto through to the ongoing Mars Express, Venus Express and Rosetta missions.

Heather, D.; Barthelemy, M.; Szumlas, M.; Arviset, C.; Osuna, P.

2012-09-01

83

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

84

Limb imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera  

CERN Document Server

We investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 70s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kiloRayleighs at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 {\\mu}m made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted.

Muñoz, A García; Sánchez-Lavega, A; Markiewicz, W J; Titov, D V; Witasse, O; Opitz, A

2013-01-01

85

The Twilight Atmosphere of Venus.  

Science.gov (United States)

An investigation of the discrepancies between the theoretically predicted and the actually observed shape and periodic appearance of Venus. Current astronomical methods of observation of the twilight sky of Venus are investigated by combining a rigorous c...

G. F. Schilling R. C. Moore

1967-01-01

86

Variations of zonal wind speed at Venus cloud tops from Venus Monitoring Camera UV images  

Science.gov (United States)

7 years of continuous monitoring of Venus by ESA's Venus Express provided an opportunity to study dynamics of the atmosphere of Venus. Venus Monitoring Camera (VMC) [1] delivered the longest and the most complete so far set of UV images to study the cloud level circulation by tracking motion of the cloud features. We analyzed 130 orbits with manual cloud tracking and 600 orbits with digital correlation method. Here we present the latest update of our results. Total number of wind vectors derived in this work is approximately a half million. During Venus Express observations the mean zonal speed was in the range of 85-110 m/s. VMC observations indicated a long term trend for the zonal wind speed at low latitudes to increase. The origin of low frequency trend with a period about 3000 days is unclear. Fourier analysis [2-3] of revealed quasi-periodicities in the zonal circulation at low latitudes. Two groups of the periods were found. The first group is close to the period of superrotation at low latitudes (4.83±0.1 days) with the period 4.1-5.1 days and the amplitude ranging from ±4.2 to ±17.4 m/s. The amplitude and phase of oscillations demonstrates dependence from the latitude and also time variability with preserving stable parameters of oscillation during at least 70 days. Short term oscillations may be caused by wave processes in the mesosphere of Venus at the cloud top level. Wave number of the observed oscillations is 1. The second group is a long term periods caused by orbital motion of Venus (116 days, 224 days) and is related to the periodicity in VMC observations. Also VMC UV observations showed a clear diurnal pattern of the mean circulation. The zonal wind demonstrated semi-diurnal variations with minimum speed close to noon (11-14 h) and maxima in the morning (8-9 h) and in the evening (16-17 h). The meridional component clearly peaks in the early afternoon (13-15h) at latitudes near 50S. The minimum of the meridional wind is located at low latitudes in the morning (8-11h). References [1] Markiewicz W. J. et al.: Venus Monitoring Camera for Venus Express // Planet. Space Sci.. V.55(12). pp1701-1711. doi:10.1016/j.pss.2007.01.004, 2007. [2] Deeming T.J.: Fourier analysis with unequally-spaced data. Astroph. and Sp. Sci. V.36, pp137-158, 1975. [3] Terebizh, V.Yu. Time series analysis in astrophysics. Moscow: "Nauka," Glav. red. fiziko-matematicheskoi lit-ry, 1992. In Russian

Khatuntsev, Igor; Patsaeva, Marina; Ignatiev, Nikolai; Titov, Dmitri; Markiewicz, Wojciech J.

2013-04-01

87

Rare gases on the Venus  

International Nuclear Information System (INIS)

Methods and equipment and results of a mass spectrometry of rare gases on the Venus are described. The dynamic radio-frequency mass analyzer used in the ''Venus-11, 12, 13, 14'' space probes is described. Primary (unprocessed) mass spectra obtained using the ''Venus-13, 14'' space probes under the consitions of analysis of rare gases are presented. Unexpectedly high content of argon-36 and argon-38 isotopes, observed on the Venus as compared to the Earth is indicated

1982-01-01

88

The contribution of science locus of control orientation to expressions of attitude toward science teaching  

Science.gov (United States)

Science locus of control (SciLOC) orientation is examined as a predictor of attitudes toward science teaching among 104 preservice elementary school teachers. SciLOC orientation refers to beliefs people hold regarding their personal efficacy, or ability to influence the outcome of events, in situations where decisions or actions require either the application of scientific knowledge or the use of reasoning skills associated with scientific thinking. A causal model that links such beliefs to attitudes toward science teaching was formulated and tested in this study. Multiple regression analysis demonstrates that 46% of the variance in attitudes toward science teaching expressed by subjects in the sample studied can be explained by SciLOC orientation. Path analysis of the proposed causal model accounts for 57% of the variance in expressed attitudes and 11% of the variance in SciLOC orientation. These results are interpreted as evidence that SciLOC orientation is a major contributor to attitudes expressed toward science teaching among preservice elementary teachers, with the major contributors to SciLOC orientation remaining to be identified. A troublesome relationship between expressed attitudes and academic performance in college science is also noted.

Haury, David L.

89

Solar wind driven plasma fluxes from the Venus ionosphere  

CERN Document Server

Measurements conducted with the ASPERA-4 instrument and the magnetometer of the Venus Express spacecraft show that the dynamic pressure of planetary O+ ion fluxes measured in the Venus wake can be significantly larger than the local magnetic pressure and, as a result, those ions are not being driven by magnetic forces but by the kinetic energy of the solar wind. Beams of planetary O+ ions with those properties have been detected in several orbits of the Venus Express through the wake as the spacecraft traverses by the noon-midnight plane along its near polar trajectory. The momentum flux of the O+ ions leads to superalfvenic flow conditions. It is suggested that such O+ ion beams are produced in the vicinity of the magnetic polar regions of the Venus ionosphere where the solar wind erodes the local plasma leading to plasma channels that extend downstream from those regions.

Perez-de-Tejada, H; Barabash, S; Zhang, T L; Sauvaud, J A; Durand-Manterola, H J; Reyes-Ruiz, M

2012-01-01

90

Ionospheric photoelectrons at Venus. A statistical review covering the first year of the VEX mission  

International Nuclear Information System (INIS)

Complete text of publication follows. At unmagnetised bodies, such as Venus, the solar wind interacts directly with the planet's atmosphere, causing an induced magnetosphere to form. Ionospheric photoelectrons are created when the solar HeII 30.4nm line ionises the upper part of the atmosphere, producing ionospheric photoelectrons and positive ions. Theory predicts these photoelectrons will be seen as two distinct peaks, at 21-24eV and 27eV, in the electron energy spectrum. These events have recently been seen at Venus as well as in other parts of the solar system, such as Earth, Mars, Titan and Saturn's rings. Several case studies at Venus have previously been published by the authors using electron, and corresponding ion, data from the Venus Express instrument ASPERA-4. We will now present a statistical review of ionospheric photoelectrons at Venus in the main ionosphere, and in the tail region, covering the first year of the Venus Express mission.

2009-08-23

91

MEETING VENUS. A Collection of Papers presented at the Venus Transit Conference Tromsoe 2012  

Science.gov (United States)

On 2-3 June 2012, the University of Tromsoe hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsoe for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the scale of the solar system in the eighteenth century. The site of the conference was the Nordnorsk Vitensenter (Science Centre of Northern Norway), which is located at the campus of the University of Tromsoe. After the conference, participants were invited to either stay in Tromsoe until the midnight of 5-6 June, or take part in a Venus transit voyage in Finnmark, during which the historical sites Vardoe, Hammerfest, and the North Cape were to be visited. The post-conference program culminated with the participants observing the transit of Venus in or near Tromsoe, Vardoe and even from a plane near Alta. These Proceedings contain a selection of the lectures delivered on 2-3 June 2012, and also a narrative description of the transit viewing from Tromsoe, Vardoe and Alta. The title of the book, Meeting Venus, refers the title of a play by the Hungarian film director, screenwriter and opera director Istvan Szabo (1938-). The autobiographical movie Meeting Venus (1991) directed by him is based on his experience directing Tannhauser at the Paris Opera in 1984. The movie brings the story of an imaginary international opera company that encounters a never ending series of difficulties and pitfalls that symbolise the challenges of any multicultural and international endeavour. As is evident from the many papers presented in this book, Meeting Venus not only contains the epic tales of the transits of the seventeenth, eighteenth and nineteenth centuries, it also covers the conference participants' encounter with "Venus on the Sun" in historical archives as well as face-to-face at several locations in the Troms and Finnmark counties.

Sterken, Christiaan; Aspaas, Per Pippin

2013-05-01

92

Venus: Not evil, jus t a bit unfortunate  

Science.gov (United States)

The Venus Express mission, currently orbiting Earth's nearest planetary neighbour, has just had its mission extended until the end of 2012 by the European Space Agency (ESA). In December 2010 it will be joined by the Japanese Venus Climate Orbiter, which has similar goals of understanding the atmosphere and climate. In this article Fred Taylor looks at what has been learned so far and what remains mysterious about our nearby twin, with its torrid weather and its global warming issues.

Taylor, Fw

2010-02-01

93

The clouds of Venus  

International Nuclear Information System (INIS)

The current state of knowledge of the Venusian clouds is reviewed. The visible clouds of Venus are shown to be quite similar to low level terrestrial hazes of strong anthropogenic influence. Possible nucleation and particle growth mechanisms are presented. The Pioneer Venus experiments that emphasize cloud measurements are described and their expected findings are discussed in detail. The results of these experiments should define the cloud particle composition, microphysics, thermal and radiative heat budget, rough dynamical features and horizontal and vertical variations in these and other parameters. This information should be sufficient to initialize cloud models which can be used to explain the cloud formation, decay, and particle life cycle. (Auth.)

1977-01-01

94

Venus rack cooling system  

International Nuclear Information System (INIS)

A rack cooling system for the VENUS detector has been developed. It uses forced-air cooling and has enough cooling power for crates with as much as 1500 watts of power consumption. The design and the cooling performance for FASTBUS crates are reported

1986-02-01

95

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

96

Phases of Venus  

Science.gov (United States)

This simple animation illustrates how we observe the phases of Venus. As the planet revolves around the Sun, there are times of the year when it is observed completely lit up by the star and times when we only get it's dark side. The user can change the inclination of the observing plane, allowing a better understanding of the process.

Fowler, Michael; Timmins, Michael

2007-12-28

97

The Pioneer Venus Missions.  

Science.gov (United States)

This document provides detailed information on the atmosphere and weather of Venus. This pamphlet describes the technological hardware including the probes that enter the Venusian atmosphere, the orbiter and the launch vehicle. Information is provided in lay terms on the mission profile, including details of events from launch to mission end. The…

National Aeronautics and Space Administration, Mountain View, CA. Ames Research Center.

98

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.

99

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

100

The Oldest Rocks on Venus: the Importance of Tessera Terrain for Venus Exploration (Invited)  

Science.gov (United States)

Venus tessera terrain is a major, yet unsampled, tectonic unit on Venus characterized by multiple sets of intersecting compressional and extensional structures. Tessera terrain is temporally, morphologically, and perhaps also compositionally unique on Venus. Stratigraphic studies of tessera terrain establish that they consistently appear locally, and perhaps even globally, as the oldest material on a planet with an average surface crater retention age of ~500 million years. Thus, the tesserae provide the best chance to access rocks that are derived from the first 80% of the history of the planet, an era obscured by the emplacement of voluminous (presumably basaltic) plains. Analysis of Magellan imagery, topography and gravity data show that tessera terrain is characterized by higher strain rates and a thinner lithosphere than at present and thus records an extinct geodynamical era on Venus. Yet very little is understood about the number, morphology and stratigraphy of geologic units within tessera terrain, nor mass wasting processes operating on the surface. Improved radar imagery at the 5-25 m scale, and optical images below the clouds (geologic processes operating in the pre-plains era. Such data products are also essential for judicious landing site selection, since tessera meter-scale roughness will limit landing site safety and sample access. Improved topography data are required to quantify the deformation recorded by ubiquitous tesserae structures that are finer than Magellan resolution. Tessera terrain is unsampled, but recent analyses of radiance from the surface at 1 micron using instruments on Venus Express and Galileo are consistent with felsic compositions for tesserae. Silicic compositions likely require both water and a plate recycling mechanism (e.g., subduction) for formation. The high D/H ratio of the Venus atmosphere is consistent with the loss of a significant inventory of water over the history of the planet. Felsic tesserae may herald from an ancient water-rich Venus, perhaps with an ocean and potentially habitable. Further assessment of tessera composition requires more comprehensive 1 micron radiance measurements from orbital, near-surface and surface platforms and in-situ measurement of mineralogy and chemistry. Radiance data need tobe supported by improved laboratory measurements of the emissivity of relevant rocks and weathering products in a Venus environment. Venus weathering experiments also support the interpretation of in situ analyses at the surface of Venus and may constrain sampling strategy. If confirmed, felsic tesserae would be critical targets for sample return due to their potential to include ancient rocks and/or minerals formed in the presence of water (e.g., zircons). In sum, the tesserae are the oldest materials exposed on the Venus surface and are the best candidates for containing ancient rocks and for comprising evolved compositions. They uniquely and critically constrain the geochemistry, geodynamics and history of water on Venus through time.

Gilmore, M. S.; Glaze, L. S.

2013-12-01

 
 
 
 
101

Tectonics and composition of Venus  

Energy Technology Data Exchange (ETDEWEB)

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 cosmochemical explanation. There may be no need to invoke differences in composition or oxidization state.

Anderson, D.L.

1980-01-01

102

Venus, Earth, Xenon  

Science.gov (United States)

Xenon has been regarded as an important goal of many proposed missions to Venus. This talk is intended to explain why. Despite its being the heaviest gas found in natural planetary atmospheres, there is more evidence that Xe escaped from Earth than for any element apart from helium: (i) Atmospheric Xe is very strongly mass fractionated (at about 4% per amu) from any known solar system source. This suggests fractionating escape that preferentially left the heavy Xe isotopes behind. (ii) Xe is underabundant compared to Kr, a lighter noble gas that is not strongly mass fractionated in air. (iii) Radiogenic Xe is strongly depleted by factors of several to ~100 compared to the quantities expected from radioactive decay of primordial solar system materials. In these respects Xe on Mars is similar to Xe on Earth, but with one key difference: Xe on Mars is readily explained by a simple process like hydrodynamic escape that acts on an initially solar or meteoritic Xe. This is not so for Earth. Earth's Xe cannot be derived by an uncontrived mass fractionating process acting on any known type of Solar System Xe. Earth is a stranger, made from different stuff than any known meteorite or Mars or even the Sun. Who else is in Earth's family? Comets? We know nothing. Father Zeus? Data from Jupiter are good enough to show that jovian Xe is not strongly mass-fractionated but not good enough to determine whether Jupiter resembles the Earth or the Sun. Sister Venus? Noble gas data from Venus are incomplete, with Kr uncertain and Xe unmeasured. Krypton was measured by several instruments on several spacecraft. The reported Kr abundances are discrepant and were once highly controversial. These discrepancies appear to have been not so much resolved as forgotten. Xenon was not detected on Venus. Upper limits were reported for the two most abundant xenon isotopes 129Xe and 132Xe. From the limited data it is not possible to tell whether Venus's affinities lie with the solar wind, or with the chondrites, with Earth, or with none of the above. Modern spacecraft mass spectrometers are at least 100-fold more sensitive to noble gases. Sending such an instrument to Venus may be the last best hope for decrypting what Earth's noble gases have been trying to tell us.

Zahnle, K. J.

2013-12-01

103

On ion escape from Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This doctoral thesis is about the solar wind influence on the atmosphere of the planet Venus. A numerical plasma simulation model was developed for the interaction between Venus and the solar wind to study the erosion of charged particles from the Venus upper atmosphere. The developed model is a hybrid simulation where ions are treated as particles and electrons are modelled as a fluid. The simulation was used to study the solar wind induced ion escape from Venus as observed by the European S...

Ja?rvinen, Riku

2011-01-01

104

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

105

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

106

Status of the VENUS ECR ion source  

International Nuclear Information System (INIS)

The status and future developments of the 28-GHz VENUS (Versatile ECR for Nuclear Science) Electron Cyclotron Resonance (ECR) ion source after the two years repair are presented. The fully superconducting ECR ion source VENUS serves as prototype injector for the Facility for Rare Isotope Beams (FRIB) project at Michigan State University (MSU) as well as injector ion source for the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). As such the source has produced many record beams of high charge state ions as well as high-intensity, medium charge state ions. As the FRIB project has now entered the preliminary design phase, LBNL is involved in the design of two new VENUS-like ECR injector ion sources for the FRIB facility. This paper will review the design changes for the FRIB injector, which will allow the installation of the FRIB injector source on a 100 kV platform. In support of the FRIB ion sources design systematic measurements of the heat load due to Bremsstrahlung from the plasma for different magnetic fields have been performed and are presented. Finally, a possible future upgrade path for the FRIB injector using an advanced Nb3Sn magnet structure is described. The paper is followed by the slides of the presentation. (authors)

2010-08-23

107

The transit of Venus enterprise in Victorian Britain  

CERN Document Server

In nineteenth century, the British Government spent money measuring the distance between the earth and the sun using observations of the transit of Venus. This book presents a narrative of the two Victorian transit programmes. It draws out their cultural significance and explores the nature of 'big science' in late-Victorian Britain.

Ratcliff, Jessica

2008-01-01

108

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)

1983-05-01

109

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

110

VENUS-2 Experimental Benchmark Analysis  

International Nuclear Information System (INIS)

The VENUS critical facility is a zero power reactor located at SCK-CEN, Mol, Belgium, which for the VENUS-2 experiment utilized a mixed-oxide core with near-weapons-grade plutonium. In addition to the VENUS-2 Core, additional computational variants based on each type of fuel cycle VENUS-2 core (3.3 wt.% UO2, 4.0 wt.% UO2, and 2.0/2.7 wt.% MOX) were also calculated. The VENUS-2 critical configuration and cell variants have been calculated with MCU-REA, which is a continuous energy Monte Carlo code system developed at Russian Research Center ''Kurchatov Institute'' and is used extensively in the Fissile Materials Disposition Program. The calculations resulted in a keff of 0.99652 ± 0.00025 and relative pin powers within 2% for UO2 pins and 3% for MOX pins of the experimental values

2001-01-01

111

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

Science.gov (United States)

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

2005-11-01

112

Latitudinal - local time distribution of the O2 and OH infrared nightglows and O density in the Venus lower thermosphere  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Atomic oxygen has been measured in situ only above 145 km on both the day and the night sides of Venus. Limb observations obtained with the Venus Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express show that the O2 infrared nightglow peaks at ~97 km [1, 2], with a mean intensity value of about 1 MR. Yet, the distribution is largely inhomogeneous, with an enhanced region of ~3 MR statistically located near the midnight meridian at low latitude [3].

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

2009-01-01

113

Encounters of the dust trails of comet 45P/Honda-Mrkos-Pajdusakova with Venus in 2006  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aims. We aim to investigate the dynamical fate of meteoroids ejected during past perihelion passages of comet 45P/Honda-Mrkos-Pajdusakova that intersect the orbit of Venus. Of particular interest is the possibility, borne of previous work, that a significant flux of these particles will reach the planet during early June and late August 2006, when the Venus Express spacecraft will be operating in orbit around Venus. Methods. We have simulated the generation of meteoroid trails ejected by the ...

Vaubaillon, Jeremie; Christou, Apostolos A.

2006-01-01

114

Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission  

Science.gov (United States)

The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

2011-12-01

115

Tectonic resurfacing of Venus  

Science.gov (United States)

Impact crater distributions and morphologies have traditionally played an important role in unraveling the geologic histories of terrestrial objects, and Venus has proved no exception. The key observations are: mean crater retention age about 500 Ma; apparently random spatial distribution; modest proportion (17 percent) of modified craters; and preferential association of modified craters with areas of low crater density. The simplest interpretation of these data alone is that Venus experienced global resurfacing (assumed to be largely volcanic) prior to 500 Ma, after which time resurfacing rates decreased dramatically. This scenario does not totally exclude present geological activity: some resurfacing and crater obliteration is occurring on part of the planet, but at rates much smaller than on Earth. An alternative endmember model holds that resurfacing is also spatially randomly distributed. Resurfacing of about 1 sq km/yr eliminates craters such that a typical portion of the surface has an age of 500 Ma, but actual ages range from zero to about 1000 Ma. Monte Carlo simulation indicates that the typical resurfacing 'patch' cannot exceed about 500 km in diameter without producing a crater distribution more heterogeneous than observed. Volcanic or tectonic processes within these patches must be locally intense to be able to obliterate craters completely and leave few modified. In this abstract, we describe how global geologic mapping may be used to test resurfacing hypotheses. We present preliminary evidence that the dominant mode of resurfacing on Venus is tectonism, not volcanism, and that this process must be ongoing today. Lastly, we outline a conceptual model in which to understand the relationship between global tectonics and crater distribution and preservation.

Malin, Michael C.; Grimm, Robert E.; Herrick, Robert R.

1993-01-01

116

Mesoscale roughness of Venus  

Science.gov (United States)

The global distribution of multi-kilometer (approx. 9 km) length scale 'roughness' (hereafter mesoscale roughness or MR) on Venus can be estimated from the Magellan global altimetry dataset (GxDR) and then compared with MR data derived for Earth from 5' ETOP5 data and for Mars (from USGS Mars DTM dataset). The mesoscale roughness parameter (MR) represents the RMS variance in meters of the actual planetary surface topography relative to the best fitting tangent plane defined on the basis of a 3x3 pixel sliding window. The best-fit plane was computed using a least-squares solution which minimizes delta H, the sum of the squares of the differences between the 9 local elevation values (H(sub i)), and the elevation of best-fit plane at the same grid location. Using the best-fit plane and delta H, we have computed the RMS 'roughness' var(delta R), where this parameter is always minimized on the basis of its calculation using least squares. We have called this 'ruggedness' parameter the Mesoscale Roughness (MR) because it is directly related to the high-frequency variance of topography after mesoscale slopes and tilts (i.e., for Venus, the baseline over which MR is computed (dx) is approx. 8.8 km and dx for Earth is approx. 9.3 km) are removed. As such, MR represents the degree to which a planetary surface is more rugged than approximately 10 km scale facets or tilts. It should not be confused with the radar 'RMS Roughness' parameter computed at 0.1 to 10 m length scales on the basis of the Magellan radar altimeter echo. We will use our MR parameter to investigate the global ruggedness properties of Venus as they relate to geological provinces and in comparison with the spatial pattern of MR for Earth and Mars.

Garvin, J. B.; Frawley, James J.

1994-01-01

117

Pioneer Venus gas chromatography of the lower atmosphere of Venus  

International Nuclear Information System (INIS)

A gas chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, N_2, O_2, Ar, CO, H_2O, SO_2, and CO_2 were measured, and upper limits set for H_2, COS, H_2S, CH_4, Kr, N_2O, C_2H_4, C_2H_6, and C_3H_8. Simulation studies have provided indirect evidence for sulfuric acid--like droplets and support the possibility of water vapor at altitudes of 42 and 24 km. The paper discusses the implications of these results for the origin, evolution, and present state of Venus' atmosphere

1980-12-30

118

Venus cloud microphysics  

Science.gov (United States)

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

Young, A. T.

1983-01-01

119

Little or no solar wind enters Venus' atmosphere at solar minimum.  

Science.gov (United States)

Venus has no significant internal magnetic field, which allows the solar wind to interact directly with its atmosphere. A field is induced in this interaction, which partially shields the atmosphere, but we have no knowledge of how effective that shield is at solar minimum. (Our current knowledge of the solar wind interaction with Venus is derived from measurements at solar maximum.) The bow shock is close to the planet, meaning that it is possible that some solar wind could be absorbed by the atmosphere and contribute to the evolution of the atmosphere. Here we report magnetic field measurements from the Venus Express spacecraft in the plasma environment surrounding Venus. The bow shock under low solar activity conditions seems to be in the position that would be expected from a complete deflection by a magnetized ionosphere. Therefore little solar wind enters the Venus ionosphere even at solar minimum. PMID:18046399

Zhang, T L; Delva, M; Baumjohann, W; Auster, H-U; Carr, C; Russell, C T; Barabash, S; Balikhin, M; Kudela, K; Berghofer, G; Biernat, H K; Lammer, H; Lichtenegger, H; Magnes, W; Nakamura, R; Schwingenschuh, K; Volwerk, M; Vörös, Z; Zambelli, W; Fornacon, K-H; Glassmeier, K-H; Richter, I; Balogh, A; Schwarzl, H; Pope, S A; Shi, J K; Wang, C; Motschmann, U; Lebreton, J-P

2007-11-29

120

To Venus with spare parts  

Science.gov (United States)

The Jet Propulsion Laboratory (JPL) is studying the possibilities of developing a special spacecraft to fly to Venus to replace the more costly Venus Orbiting Imaging Radar (VOIR) mission. According to a recent JPL Newsletter, the new Venus Radar Mapper (VRM) spacecraft is to be constructed mainly of spare parts left over from other missions. The VRM is to be landed in the spring of 1988 by means of either the space shuttle/ two-stage inertial upper-stage (IUS) combination or, preferably, with the much more powerful shuttle/Centaur upper-stage rocket. Once boosted into orbit around Venus, the scientific objections of VRM are clear. Venus has about the same mass and composition as the earth, and yet little is known about its geology. It will be possible for the VRM to map Venus by radar from an elliptical orbit, which is a lower cost option than would have been possible with the VOIR. VRM will carry a synthetic aperture radar (SAR) that operates with variable angles ranging from 51° for the lowest altitudes (250 km) to 24° for the highest altitudes (1900 km). A total of about 92% of Venus' surface will be mapped at a resolution of 1 km/line or better.

Bell, Peter M.

 
 
 
 
121

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

1990-01-01

122

Progress report on VENUS  

Energy Technology Data Exchange (ETDEWEB)

The construction of VENUS, a next generation superconducting Electron Cyclotron Resonance ion source designed to operate at 28 GHz, is complete. The cryostat including the superconducting magnet assembly was delivered in September 2001. During acceptance tests, the superconducting magnets produced an axial magnetic field strength of 4T at injection, 3T at extraction, and a radial field strength of 2T at the plasma chamber wall without any quenches. These fields are sufficient for optimum operation at 28 GHz. The cryogenic system for VENUS has been designed to operate at 4.2 K with two cryocoolers each providing up to 45 W of cooling at 50 K and 1.5 W at 4 K in a closed loop mode without further helium transfers. However, during the acceptance tests an excessive heat leak of about 3W was measured. In addition, the liquid helium heat exchanger did not work properly and had to be redesigned. The cryogenic system modifications will be described. In addition, an update on the installation of the ion source and its beam line components will be given.

Leitner, Matthaeus A.; Leitner, Daniela; Abbott, Steve R.; Taylor, Clyde E.; Lyneis, Claude

2002-09-03

123

Progress report on VENUS  

International Nuclear Information System (INIS)

The construction of VENUS, a next generation superconducting Electron Cyclotron Resonance ion source designed to operate at 28 GHz, is complete. The cryostat including the superconducting magnet assembly was delivered in September 2001. During acceptance tests, the superconducting magnets produced an axial magnetic field strength of 4T at injection, 3T at extraction, and a radial field strength of 2T at the plasma chamber wall without any quenches. These fields are sufficient for optimum operation at 28 GHz. The cryogenic system for VENUS has been designed to operate at 4.2 K with two cryocoolers each providing up to 45 W of cooling at 50 K and 1.5 W at 4 K in a closed loop mode without further helium transfers. However, during the acceptance tests an excessive heat leak of about 3W was measured. In addition, the liquid helium heat exchanger did not work properly and had to be redesigned. The cryogenic system modifications will be described. In addition, an update on the installation of the ion source and its beam line components will be given

2002-06-12

124

Short Large-Amplitude Magnetic Structures (SLAMS) at Venus  

Science.gov (United States)

We present the first observation of magnetic fluctuations consistent with Short Large-Amplitude Magnetic Structures (SLAMS) in the foreshock of the planet Venus. Three monolithic magnetic field spikes were observed by the Venus Express on the 11th of April 2009. The structures were approx.1.5->11s in duration, had magnetic compression ratios between approx.3->6, and exhibited elliptical polarization. These characteristics are consistent with the SLAMS observed at Earth, Jupiter, and Comet Giacobini-Zinner, and thus we hypothesize that it is possible SLAMS may be found at any celestial body with a foreshock.

Collinson, G. A.; Wilson, L. B.; Sibeck, D. G.; Shane, N.; Zhang, T. L.; Moore, T. E.; Coates, A. J.; Barabash, S.

2012-01-01

125

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

126

Constraining Corona Formation on Venus  

Science.gov (United States)

We model the formation of off-rift coronae at Parga Chasma in order to understand how Venus loses its heat. We find the data required to make proper comparisons between models and observations is lacking.

Piskorz, D.; Elkins-Tanton, L. T.; Smrekar, S. E.

2014-05-01

127

Venus näitas lillekleite / Regina Hansen  

Index Scriptorium Estoniae

Sunflower Beauty Contest esitles ööklubis Venus eluslilledest valmistatud kleite. Parimaks tunnistati kaupluse Annilill floristid tööga "My Bunny", teiseks tunnistati Katrin Pedaru ja Ninell Soosaare "C'est la vie", kolmanda koha pälvis Karina Saberi töö "Unistus"

Hansen, Regina

2001-01-01

128

Venus' free obliquity.  

Science.gov (United States)

The predicted orientation of Venus' rotation axis relative to its orbit can be uniquely determined given knowledge of its J2 gravity coefficient and polar moment of inertia C if its free obliquity is fully damped. This assumption seems warranted given the dominant damping mechanism: turbulent fluid friction at a core mantle boundary (CMB). This skin friction results from differential obliquity of mantle and core spin axes, and the associated damping rate could be as short as 1/10 6 year. However, the observed pole orientation indicates a free obliquity amplitude ? ? 2.1° compared with a nominal forced amplitude of 0.5°. There are two plausible explanations. The most likely is that the observed obliquity is a tidally evolved end state in which core friction, modulated by CMB ellipticity and core obliquity amplitude, counterbalances solid and atmospheric tidal torques. This concept is similar to the explanation for the retrograde spin to as an end state in which solid and atmospheric thermal tidal torques balance at the present spin rate because of the ?-1 dependence of the axial thermal torque. Large core ellipticity e c ? (C c - 1/2(A c + B c ))/C c (C c ? B c ? A c are core moments of inertia) can substantially increase fluid friction damping time if e c is significantly larger than the whole body ellipticity e o = J2MR2/ C ? 1.3 × 10 -5 by reducing the relative obliquity of core and mantle spin vectors. Note that the hydrostatic contribution to oblateness ˜1.7 × 10 -7 is presently negligible. Weaker effects such as solid and thermal tides can then compete with core friction and for plausible models, their sum tends to increase free obliquity. The obliquity balance is controlled by the nonlinear (and nearly quadratic) dependence of the CMB turbulent "skin friction" torque on obliquity. I find that a steady state is achieved for e c ? 29 e o ? 4 × 10 -4. If the CMB topography is dynamically supported, then the necessary bottom density anomaly is constrained to the bottom ˜10% of the mantle. An alternative model is that the obliquity results from resonant excitation due to small amplitude (?0.002°), prograde oscillations in Venus' orbit, one of which happens nearly to match Venus' precession rate ?. This mechanism can account for the obliquity even if the iron core has solidified, but also requires a tectonically quiescent planet ( d| J2/ dt| fluid, core size and c

Yoder, Charles F.

1995-10-01

129

Atomic oxygen on the Venus nightside: Global distribution deduced from airglow mapping  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Visible and Infra-Red Thermal Imaging Spectrometer (VIRTIS) instrument on board the Venus Express spacecraft has measured the O2(a1[Delta]) nightglow distribution at 1.27 [mu]m in the Venus mesosphere for more than two years. Nadir observations have been used to create a statistical map of the emission on Venus nightside. It appears that the statistical 1.6 MR maximum of the emission is located around the antisolar point. Limb observations provide information on the altitude and on the ...

Soret, Lauriane; Ge?rard, Jean-claude; Montmessin, Franck; Piccioni, Giuseppe; Drossart, Pierre; Bertaux, Jean-loup

2012-01-01

130

Temporal variations of zonal wind speed at Venus cloud tops from Venus Monitoring Camera UV images  

Science.gov (United States)

Venus Monitoring Camera (VMC) [1] on board the Venus Express mission obtained great number of UV images of the upper cloud. The observations cover about 10 Venusian years. 600 orbits or about 25% of all available UV images were processed by the digital wind tracking routine resulting in ~400000 vectors for the whole period of observations. Mean profiles were calculated for individual orbits. Time series of zonal speed for 5 degrees latitude bins centered at 10, 15, 20, 25 and 30 South were created from the individual mean profiles. The time series were investigated for periodicities by using Deeming algorithm [2] for unequally-spaced data. Two groups of the periods were found. The first group is close to the period of superrotation at low latitudes (4.83±0.1 days) with the period 4.1-5.1 days and the amplitude ranging from ±4.26 to ±17.44 m/s. The amplitude and phase of oscillations demonstrates dependence from the latitude and also time variability with preserving stable parameters of oscillation during at least 70 days. The second one is a long term periods caused by orbital motion of Venus (116 days, 224 days) and is related to the periodicity in the VMC observations.

Khatuntsev, I. V.; Patsaeva, M. V.; Ignatiev, N. I.; Titov, D. V.; Markiewicz, W. J.; Turin, A. V.

2012-09-01

131

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

Science.gov (United States)

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

Grimm, Robert E.; Phillips, Roger J.

1991-01-01

132

Venus - Magellan and Arecibo Comparison  

Science.gov (United States)

This image shows a comparison between a Magellan image (right) and the highest resolution Earth-based radar image of Venus, obtained by the U.S. National Astronomy and Ionosphere Center's Arecibo Observatory in Puerto Rico. The small white box in the Arecibo image on the left corresponds to the Magellan image. This portion of a Magellan radar image strip shows a small region on the east flank of a major volcanic upland called Beta Regio. The image is centered at 23 degrees north latitude and 286.7 degrees east longitude. The ridge and valley network in the middle part of the image is formed by intersecting faults which have broken the Venusian crust into a complex deformed type of surface called tessera, the Latin word for tile. The parallel mountains and valleys resemble the Basin and Range Province in the western United States. The irregular dark patch near the top of the image is a smooth surface, probably formed by lava flows in a region about 10 km (6 miles) across. Similar dark surfaces within the valleys indicate lava flows that are younger than the tessera. The Arecibo image contains probable impact craters, many faults, volcanic flows and tessera regions that will be mapped in detail by Magellan. The Magellan image has a resolution of 120 meters, (400 feet). The image segment is 20 km (12.4 miles) wide and 150 km (90 miles) long. The Arecibo image has a resolution of 1 3 km (0.6 1.8 miles) and is approximately 900 km (550 miles) across. The National Astronomy and Ionosphere Center is operated by Cornell University under a management agreement with the National Science Foundation with some support from NASA.

1990-01-01

133

Recent discoveries of the thermospheres and ionospheres of Venus and Mars (Invited)  

Science.gov (United States)

Of all the non-terrestrial ionospheres and thermospheres, those of Venus and Mars have been explored and studied the most, thanks to the Pioneer Venus Orbiter and the Mars Global Surveyor from NASA, and the Venus Express and the Mars Express from ESA. We know that the thermosphere and ionosphere are atmospheric layers strongly influenced by solar wind and solar extreme ultra-violet and soft X-ray flux. This talk will outline the most significant discoveries made recently, which have strong implications on how atmospheres evolve and interact with the Sun. For Venus, there is the sporadic behaviour of the atomic oxygen green line emission, and there is the strong variability of the polar upper atmospheric density. For Mars, there are the responses of the upper atmosphere to solar energetic particle events, the effect of the crustal magnetic field, and the ionospheric vertical structure and boundaries. Finally, this talk will address questions that need to be answered by future missions.

Witasse, O. G.

2013-12-01

134

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

135

Enabling Venus In-Situ Science - Deployable Entry System Technology, Adaptive Deployable Entry and Placement Technology (ADEPT): A Technology Development Project funded by Game Changing Development Program of the Space Technology Program  

Science.gov (United States)

Venus is one of the important planetary destinations for scientific exploration, but: The combination of extreme entry environment coupled with extreme surface conditions have made mission planning and proposal efforts very challenging. We present an alternate, game-changing approach (ADEPT) where a novel entry system architecture enables more benign entry conditions and this allows for greater flexibility and lower risk in mission design

Wercinski, Paul F.; Venkatapathy, Ethiraj; Gage, Peter J.; Yount, Bryan C.; Prabhu, Dinesh K.; Smith, Brandon; Arnold, James O.; Makino, alberto; Peterson, Keith Hoppe; Chinnapongse, Ronald I.

2012-01-01

136

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

1996-01-01

137

Biologically closed electrical circuits in venus flytrap.  

Science.gov (United States)

The Venus flytrap (Dionaea muscipula Ellis) is a marvel of plant electrical, mechanical, and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The Venus flytrap can accumulate small subthreshold charges and, when the threshold value is reached, the trap closes. Here, we investigated the electrical properties of the upper leaf of the Venus flytrap and proposed the equivalent electrical circuit in agreement with the experimental data. PMID:19211696

Volkov, Alexander G; Carrell, Holly; Markin, Vladislav S

2009-04-01

138

Clouds of Venus. Input to VIRA.  

Science.gov (United States)

Venus is completely covered by a thick clod deck. Its' total optical depth in the visible is equal to 30+/-10. Original VIRA model based on the measurements from Pioneer Venus descent probes and orbiter described mainly cloud particle sizes, properties and their vertical distribution. Later measurements from Venera-15 and Venus Express permitted more detailed studies of horizontal and vertical variations. Imaging of Venus in the UV range shows variety of cloud features that include mottled and streaky clouds in the low latitudes, bright mid-latitude belt and ``polar cap'' with imbedded oval polar dipole. Despite this non-uniform picture the location of the upper boundary of the clouds, derived from the observation of the absorption bands in the reflected IR spectrum, demonstrates a smooth systematic behavior with the latitudinal trends symmetric with respect to equator. In low and middle latitudes the cloud top is located at 72+/-1 km. It decreases poleward of +/-50 degrees and reaches 63--69 km in polar regions. This depression coincides with the eye of the planetary vortex. The effective average particle size radius is equal to (1.3+/-0.5) micron at latitudes of 0--70, with a peak value some 50% larger in the polar regions. Cloud top can experience fast variations of about metricconverterProductID1 km1 km in tens of hours, while larger long-term variations of several kilometers have been observed only at high latitudes. UV markings correlate with the cloud altimetry, however the difference between adjacent UV dark and bright regions never exceeds few hundred meters. Ultraviolet dark spiral arms, which are often seen at about --70 degress, correspond to higher altitudes or to the regions with strong latitudinal gradient of the cloud top altitude. In contrast to the relatively uniform upper cloud boundary, strong variations of the brightness temperature at specific near infrared wavelengths, especially in low latitudes, are related to variations of the cloud thickness in the middle and low cloud decks consistent with significant convective activity at these levels. The morphology of the holes tends from highly variable orientations of features with aspect ratios of nearly one at low latitudes, to very large aspect ratios and zonally oriented features at higher latitudes.

Ignatiev, Nikolay; Zasova, Ludmila

2012-07-01

139

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

1982-01-01

140

A Generic Science Operation Planning Concept for Planetary Missions and its Implementation on the First ESA Lunar Mission SMART-1  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The subsystems of an interplanetary spacecraft can be broken down in two categories: The satellite platform and the scientific payload instruments. The same breakdown is reflected in the distribution of the tasks and responsibilities in the ground segment of the planetary missions of the European Space Agency. Examples for ESA planetary missions are the SMART-1, MarsExpress, VenusExpress, Rosetta and the BepiColombo missions. The Science Operation Centre, SOC, of a planetary mission is respon...

Sarkarati, Mehran

2010-01-01

 
 
 
 
141

Rate of volcanism on Venus  

Energy Technology Data Exchange (ETDEWEB)

The maintenance of the global H/sub 2/SO/sub 4/ clouds on Venus requires volcanism to replenish the atmospheric SO/sub 2/ 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 SO/sub 2/ and calcite (CaCO/sub 3/) to form anhydrite (CaSO/sub 4/), are reported. If the rate of this reaction is representative of the SO/sub 2/ reaction rate at the Venus surface, then we estimate that all SO/sub 2/ in the Venus atmosphere (and thus the H/sub 2/SO/sub 4/ clouds) will be removed in 1.9 million years unless the lost SO/sub 2/ 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, B. Jr.; Prinn, R.G.

1988-07-01

142

Chemical Weathering Kinetics of Basalt on Venus  

Science.gov (United States)

The purpose of this project was to experimentally measure the kinetics for chemical weathering reactions involving basalt on Venus. The thermochemical reactions being studied are important for the CO2 atmosphere-lithosphere cycle on Venus and for the atmosphere-surface reactions controlling the oxidation state of the surface of Venus. These reactions include the formation of carbonate and scapolite minerals, and the oxidation of Fe-bearing minerals. These experiments and calculations are important for interpreting results from the Pioneer Venus, Magellan, Galileo flyby, Venera, and Vega missions to Venus, for interpreting results from Earth-based telescopic observations, and for the design of new Discovery class (e.g., VESAT) and New Millennium missions to Venus such as geochemical landers making in situ elemental and mineralogical analyses, and orbiters, probes and balloons making spectroscopic observations of the sub-cloud atmosphere of Venus.

Fegley, Bruce, Jr.

1997-01-01

143

A survey of hot flow anomalies at Venus  

Science.gov (United States)

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

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

2014-02-01

144

Formation of plasma vortices in the interaction of the Solar Wind with the ionosphere of Venus  

Science.gov (United States)

Recent in-situ measurements from the Venus Express spacecraft indicate the existence of large-scale vortex-like motions in the combined plasma flow, solar wind H+ and ionospheric O+ ions, in the Venus plasma tail (Lundin et al. 2012, Pérez-de-Tejada et al., 2012). We present results of three-dimensional numerical simulations of the fluid-like interaction of the solar wind with the ionosphere of Venus. The formation of vortical flows in the near wake of Venus plasma environment is naturally explained in the context of such scenario due to the advection and stretching of structures resulting from the development of the Kelvin-Helmholtz instability at the ionopause. The consequent erosion rate of ionospheric material predicted by our results is also quantified.

Reyes-Ruiz, M.; Perez De Tejada, H. A.; Aceves, H.

2013-05-01

145

Neurogenin2-d4Venus and Gadd45g-d4Venus transgenic mice: Visualizing mitotic and migratory behaviors of cells committed to the neuronal lineage in the developing mammalian brain.  

Science.gov (United States)

To achieve highly sensitive and comprehensive assessment of the morphology and dynamics of cells committed to the neuronal lineage in mammalian brain primordia, we generated two transgenic mouse lines expressing a destabilized (d4) Venus controlled by regulatory elements of the Neurogenin2 (Neurog2) or Gadd45g gene. In mid-embryonic neocortical walls, expression of Neurog2-d4Venus mostly overlapped with that of Neurog2 protein, with a slightly (1 h) delayed onset. Although Neurog2-d4Venus and Gadd45g-d4Venus mice exhibited very similar labeling patterns in the ventricular zone (VZ), in Gadd45g-d4Venus mice cells could be visualized in more basal areas containing fully differentiated neurons, where Neurog2-d4Venus fluorescence was absent. Time-lapse monitoring revealed that most d4Venus(+) cells in the VZ had processes extending to the apical surface; many of these cells eventually retracted their apical process and migrated basally to the subventricular zone, where neurons, as well as the intermediate neurogenic progenitors that undergo terminal neuron-producing division, could be live-monitored by d4Venus fluorescence. Some d4Venus(+) VZ cells instead underwent nuclear migration to the apical surface, where they divided to generate two d4Venus(+) daughter cells, suggesting that the symmetric terminal division that gives rise to neuron pairs at the apical surface can be reliably live-monitored. Similar lineage-committed cells were observed in other developing neural regions including retina, spinal cord, and cerebellum, as well as in regions of the peripheral nervous system such as dorsal root ganglia. These mouse lines will be useful for elucidating the cellular and molecular mechanisms underlying development of the mammalian nervous system. PMID:24712911

Kawaue, Takumi; Sagou, Ken; Kiyonari, Hiroshi; Ota, Kumiko; Okamoto, Mayumi; Shinoda, Tomoyasu; Kawaguchi, Ayano; Miyata, Takaki

2014-05-01

146

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

147

Tectonic Resurfacing Model for Venus.  

Science.gov (United States)

Two remarkable aspects of the population of impact craters on Venus are as follows: that craters at all sizes are indistinguishable from a random population; and that the vast majority of craters have not been significantly modified by tectonic strain or ...

S. C. Solomon

1993-01-01

148

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

149

Venus ionopause during solar minimum  

International Nuclear Information System (INIS)

During solar minimum, the Venus ionosphere is weak and the solar wind depresses the ionopause to a limiting altitude (Knudsen et al., 1987). With the knowledge gained from the ion composition measurements on Pioneer Venus during solar maximum and during conditions of high solar wind pressure, the authors argue that the typical topside electron density profile at Venus during solar minimum has two distinct regimes; one from about 140 km (the altitude of peak electron density) to 180 km and the other above 180 km. While the former is dominated by O2+ ions which are in photochemical equilibrium, the latter is dominated by O+ ions which are strongly disturbed by the solar wind induced plasma transport. The disturbed ionosphere is formed in the photodynamical regime and has a scale height which is several times smaller than that expected under undisturbed conditions when the ionosphere is in diffusive equilibrium. The small scale height of the disturbed ionosphere is nearly equal to that of the ionizable constituent, atomic oxygen, and is only slightly larger than the chemical equilibrium scale height of the underlying chemical equilibrium region. While the photodynamical ionopause occurs rarely during solar maximum and only when the solar wind pressure is large, we believe that this kind of ionopause is observed much more frequently during solar minimum. The authors find evidence for this in the radio occultation data from Pioneer Venus, Mariner 10 and Venera 9 and 10

1989-01-01

150

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

International Nuclear Information System (INIS)

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

2005-07-01

151

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

152

Ion heating near the ion composition boundary at Venus  

Science.gov (United States)

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

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

2014-05-01

153

Transits of Venus in Public Education and Contemporary Research  

Science.gov (United States)

Transits of Venus are among the rarest predictable astronomical event that humans can enjoy, and the 2012 transit will be visible by almost all the people on Earth. It is our job as educators to bring out the thrill of being able to see the tiny dot of Venus silhouetted against the solar disk even with just a simple eye-protection filter. My Website at http://www.transitofvenus.info brings together not only historical information about the five previous transits of Venus that were observed through the 20th century--1639, 1761, 1769, 1874, and 1882--but also the scientific work carried out at the 2004 transit and at recent transits of Mercury. Based on space observations of the 1999 transit of Mercury with NASA's Transition Region and Coronal Explorer (TRACE), Glenn Schneider and I provided proof of the contemporary explanation of the black-drop effect as an amalgam of instrumental point-spread and solar limb-darkening [1]. Based on observations of the changes in the total solar irradiance during the transit, we provided an analysis of this solar-system analogue to exoplanet transits [2]. High-resolution (0.5 arcsec pixels) observations of ingress and egress with TRACE during the 2004 transit provided information about the visibility of Venus's atmosphere through its refraction of sunlight, interpreted with Venus Express observations [3]. We anticipate observing the 2012 transit with groundbased facilities of the University of Hawaii at Haleakala, and of the National Solar Observatory at Sacramento Peak, and Kitt Peak, as well as with NASA and JAXA spacecraft, including Solar Dynamics Observatory, ACRIMsat, and Hinode. The Program Group on Public Education on the Occasions of Eclipses and Transits of Commission 46 on Education and Development of the International Astronomical Union, which I chair, looks forward to participating in Education and Public Outreach efforts related to the 2012 transit.

Pasachoff, J. M.

2011-10-01

154

Abstracts for the venus geoscience tutorial and venus geologic mapping workshop  

Energy Technology Data Exchange (ETDEWEB)

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

155

The magnetosheath and magnetotail of Venus  

Energy Technology Data Exchange (ETDEWEB)

The subjects to be discussed in this review, the Venus magnetosheath and magnetotail, make up a major portion, but by no means the entirety, of the interaction of the solar wind with Venus. The authors describe the observational history and assess the current understanding of the magnetosheath and magnetotail of Venus, stressing recent developments. They make recommendations for research that can be done using existing observations, as well as desirable trajectory and instrumentation characteristics for future spacecraft missions.

Phillips, J.L.; McComas, D.J. (Los Alamos National Lab., NM (United States))

1991-01-01

156

Venus chasmata: A lithosphere stretching model  

Science.gov (United States)

An outstanding problem for Venus is the characterization of its style of global tectonics, an issue intimately related to the dominant mechanism of lithospheric heat loss. Among the most spectacular and extensive of the major tectonic features on Venus are the chasmata, deep linear valleys generally interpreted to be the products of lithospheric extension and rifting. Systems of chasmata and related features can be traced along several tectonic zones up to 20,000 km in linear extent. A lithospheric stretching model was developed to explain the topographic characteristics of Venus chasmata and to constrain the physical properties of the Venus crust and lithosphere.

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

1985-01-01

157

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

1989-06-12

158

Substorm activity in Venus's magnetotail  

Directory of Open Access Journals (Sweden)

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

M. Volwerk

2009-06-01

159

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

160

Surface and the crust of Venus planet  

International Nuclear Information System (INIS)

Modern information on surface of the Venus planet obtained by radiolocation investigations from the Earth and orbiters ''Pioneer-Venera'', ''Venera'' and ''Vega'' is presented in a popular form. The surface panoramas of the planet, obtained with automatic interplanetary stations ''Venera-9, 10, 13, 14'' are presented. Physico-chemical properties of Venus rocks are considered

1986-01-01

 
 
 
 
161

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

1987-05-01

162

Comparative aspects of Venus and terrestrial meteorology  

Energy Technology Data Exchange (ETDEWEB)

The observations and measurements made by Pioneer Venus orbiters are presented in terms of comparison of Venus and terrestrial meteorology. Although the temperature-pressure profiles of the two planets differ at lower altitudes, the temperatures are similar over their common range of pressures except for a much cooler mesosphere on Venus. The additional similarities between the earth and Venus relate to the warm polar stratospheres and the zonally-averaged energy budgets of the two planets. A difference in the mean radiation budgets for Venus is the relative smallness of the upward and downward thermal flux components. It is noted that the observed similarities reflect common mechanisms despite the difference in the dynamical regimes of the two planets.

Taylor, F.W. (Oxford University, Oxford, England); Elson, L.S. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, Calif.)

1980-01-01

163

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

164

Breast milk expression knowledge of school of medicine and faculty of health sciences students  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background: When direct breastfeeding of the mother’s breast is not possible, expressing of human milk should be provided. Education and support to the mothers for breastfeeding by health care professionals have improved breastfeeding initiation and duration. The aim of the study was to determine the knowledge of the students of Gaziantep University School of Medicine and Faculty of Health Sciences about breast milk expression. ...

2013-01-01

165

The loss of ions from Venus through the plasma wake.  

Science.gov (United States)

Venus, unlike Earth, is an extremely dry planet although both began with similar masses, distances from the Sun, and presumably water inventories. The high deuterium-to-hydrogen ratio in the venusian atmosphere relative to Earth's also indicates that the atmosphere has undergone significantly different evolution over the age of the Solar System. Present-day thermal escape is low for all atmospheric species. However, hydrogen can escape by means of collisions with hot atoms from ionospheric photochemistry, and although the bulk of O and O2 are gravitationally bound, heavy ions have been observed to escape through interaction with the solar wind. Nevertheless, their relative rates of escape, spatial distribution, and composition could not be determined from these previous measurements. Here we report Venus Express measurements showing that the dominant escaping ions are O+, He+ and H+. The escaping ions leave Venus through the plasma sheet (a central portion of the plasma wake) and in a boundary layer of the induced magnetosphere. The escape rate ratios are Q(H+)/Q(O+) = 1.9; Q(He+)/Q(O+) = 0.07. The first of these implies that the escape of H+ and O+, together with the estimated escape of neutral hydrogen and oxygen, currently takes place near the stoichometric ratio corresponding to water. PMID:18046398

Barabash, S; Fedorov, A; Sauvaud, J J; Lundin, R; Russell, C T; Futaana, Y; Zhang, T L; Andersson, H; Brinkfeldt, K; Grigoriev, A; Holmström, M; Yamauchi, M; Asamura, K; Baumjohann, W; Lammer, H; Coates, A J; Kataria, D O; Linder, D R; Curtis, C C; Hsieh, K C; Sandel, B R; Grande, M; Gunell, H; Koskinen, H E J; Kallio, E; Riihelä, P; Säles, T; Schmidt, W; Kozyra, J; Krupp, N; Fränz, M; Woch, J; Luhmann, J; McKenna-Lawlor, S; Mazelle, C; Thocaven, J-J; Orsini, S; Cerulli-Irelli, R; Mura, M; Milillo, M; Maggi, M; Roelof, E; Brandt, P; Szego, K; Winningham, J D; Frahm, R A; Scherrer, J; Sharber, J R; Wurz, P; Bochsler, P

2007-11-29

166

Proton cyclotron wave generation mechanisms upstream of Venus  

International Nuclear Information System (INIS)

Complete text of publication follows. Recent long term observations of proton cyclotron waves in the upstream region of Venus raise the question, under which general solar wind conditions these waves are generated and maintained. Magnetometer data of the Venus Express spacecraft for two Venusian years of observations are analyzed before, during and after the occurrence of the waves. The classical mechanism for nearly perpendicular configurations of the interplanetary magnetic field (BIMF) and the solar wind velocity (VSW) with ion pick-up into a ring-distribution in velocity space is investigated for its efficiency, as well as wave generation under quasi-parallel conditions for the VSW and BIMF , when the solar wind motional electric field is weak. It is found that stable magnetic field conditions for up to 20-30 minutes are required to enable sufficient ion pick-up and growth of the left-hand polarized wave component to obtain observable waves in the magnetometer data. Only few cases with persistent waves under quasi-perpendicular conditions of BIMF and VSW are detected. This indicates that instabilities driven by field-aligned planetary ion beams act as main generation mechanism for the proton cyclotron waves observed upstream of the Venus bow shock.

2009-08-23

167

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

168

Geologic Map of the Niobe Planitia Quadrangle (V-23), Venus  

Science.gov (United States)

The Niobe Planitia quadrangle (V-23) encompasses approximately 8,000,000 km2 of the Venusian equatorial region extending from lat 0 deg to 25 deg N. and from long 90 deg to 120 deg E. (approximately 9,500 15-minute quadrangles on Earth). The map area lies along the north margin of the equatorial highland, Aphrodite Terra (V-35), and extends into the lowland region to the north, preserving a transition from southern highlands to northern lowlands (figs. 1, 2, map sheet). The northern parts of the crustal plateau, Ovda Regio and Haasttse-baad Tessera, mark the south margin of the map area; Niobe and Sogolon Planitiae make up the lowland region. The division between Niobe and Sogolon Planitiae is generally topographic, and Sogolon Planitia forms a relatively small elongate basin. Mesolands, the intermediate topographic level of Venus, are essentially absent or represented only by Gegute Tessera, which forms a slightly elevated region that separates Niobe Planitia from Llorona Planitia to the east (V-24). Lowlands within the map area host five features currently classified as coronae: Maya Corona (lat 23 deg N., long 97 deg E.) resides to the northwest and Dhisana, Allatu, Omeciuatl, and Bhumiya Coronae cluster loosely in the east-central area. Lowlands extend north, east, and west of the map area. Mapping the Niobe Planitia quadrangle (V-23) provides an excellent opportunity to examine a large tract of lowlands and the adjacent highlands with the express goal of clarifying the processes responsible for resurfacing this part of Venus and the resulting implications for Venus evolution. Although Venus lowlands are widely considered to have a volcanic origin, lowlands in the map area lack adjacent coronae or other obvious volcanic sources.

Hansen, Vicki L.

2009-01-01

169

A study of Shocks in the vicinity of Venus during the passage of an ICME  

Science.gov (United States)

On 5th November 2011 an ICME with a velocity of about 850 km/s and IMF of 40nT (nominal values at 0.72AU are about 400 km/s and 10nT) passed Venus. Venus Express (VEX) was in the solar wind during the onset of the ICME which lasted for the duration of the passage of the spacecraft through the induced magnetosphere of Venus. Magnetic field data at 1Hz is available for the duration of the ICME and the location of the spacecraft allows the shock in the solar wind due to the super magnetosonic ICME and the subsequent bow shock of Venus under extreme solar wind conditions to be studied. Plasma data is also available during the ICME passage, both prior to VEX crossing the bow shock of Venus and while it is in the induced magnetosphere. On the inbound passage the location of the bow shock of Venus is compressed by around 0.22 Rv (at 19o SZA) compared to its position on the previous and following days and on the outbound passage the spacecraft makes several crossings of the bow shock, suggesting a dynamic boundary at 149o SZA, which is increased from the previous and following days location by 0.5-2.7 Rv. The step in the magnetic field on the inbound shock crossing was approximately 60% higher than observed on the previous and following days when the IMF was near the nominal value of 10nT. Consequently this leads to a significantly greater field in the induced magnetosphere than is usually present. During the multiple outbound crossings of the bow shock, strong wave precursors are observed. The paper compares the structure of both the inbound and outbound bow shock crossings with those observed at Venus for both nominal conditions and previous ICME passages.

Pope, S. A.; Dimmock, A. P.; Zhang, T.; Balikhin, M. A.; Fedorov, A.

2013-12-01

170

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 (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

2009-03-16

171

Comet Halley: The view from Pioneer Venus  

Energy Technology Data Exchange (ETDEWEB)

The plans to scan Halley's Comet at close range using the Pioneer Venus Orbiter are discussed. The composition of comets, their paths through space, and the history of comet encounters are examined. An ultraviolet spectrometer aboard the spacecraft will determine the composition of the gaseous coma and will measure the total gas production during its passage. The Pioneer Venus Orbiter will observe the comet for five weeks before solar interference with communications occurs as Venus passes on the far side of the Sun from Earth. Diagrams of the solar system and the relationship of the comet to the planets and the Sun are provided.

1989-01-01

172

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

1985-01-01

173

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

174

A correlated-k model of radiative transfer in the near-infrared windows of Venus  

International Nuclear Information System (INIS)

We present a correlated-k-based model for generating synthetic spectra in the near-infrared window regions, from 1.0 to 2.5 ?m, emitted from the deep atmosphere of Venus on the nightside. This approach is applicable for use with any near-infrared instrument, ground-based and space-borne, for analysis of the thermal emissions in this spectral range. We also approach this work with the view of using the model, in conjunction with a retrieval algorithm, to retrieve minor species from the Venus Express/VIRTIS instrument. An existing radiative-transfer model was adapted for Venusian conditions to deal with the prevailing high pressures and temperatures and other conditions. A comprehensive four-modal cloud structure model based on Pollack et al. [Near-infrared light from venus' nightside: a spectroscopic analysis. Icarus 1993;103:1-42], using refractive indices for a 75% H2SO425% H2O mixture from Palmer and Williams [Optical constants of sulfuric acid; application to the clouds of Venus? Appl Opt 1975;14(1):208-19], was also implemented. We then utilized a Mie scattering algorithm to account for the multiple scattering effect between cloud and haze layers that occur in the Venusian atmosphere. The correlated-k model is shown to produce good agreement with ground-based spectra of Venus in the near infrared, and to match the output from a line-by-line radiative-transfer model to better than 10%

2008-04-01

175

Solar Migrating Atmospheric Tides in the Winds of the Polar Region of Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the effects of migrating solar tides on the winds at the cloud tops of the polar region of Venus. The winds were measured using cloud tracking on images obtained at wavelengths of 3.9 and 5.0 ?m by the instrument VIRTIS-M onboard Venus Express. These wavelengths probe about the same altitude close to the cloud tops, allowing for the first time to retrieve winds simultaneously in the day and nightside of the planet. We use a dataset with observations from 16 orbits, covering a time s...

Peralta, Javier; Luz, David; Berry, David; Tsang, Constantine; Sa?nchez-lavega, Agusti?n; Huelso, Ricardo; Piccioni, Giuseppe; Drossart, Pierre

2012-01-01

176

The distributions of the OH (?v=1) and (?v=2) emissions on the Venus nightside  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The presence of OH was detected in the spectrum of the Venus mesosphere observed at the limb with the VIRTIS instrument on board the Venus Express spacecraft [3]. The (1-0) and (2-1) transitions at 2.80 and 2.94 mm, respectively and the (2-0) band at 1.43 mm were clearly identified. The results of this study show that a correlation is observed between the emissions associated to the ?v=1 and the ?v=2 sequences.

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

2010-01-01

177

Venus - Computer Simulated Global View Centered at 90 Degrees East Longitude  

Science.gov (United States)

This global view of the surface of Venus is centered at 90 degrees east longitude. Magellan synthetic aperture radar mosaics from the three eight-month cycles of Magellan radar mapping are mapped onto a computer-simulated globe to create this image. Magellan obtained coverage of 98 percent of the surface of Venus. Remaining gaps are filled with data from previous Venus missions -- the Venera 15 and 16 radar and Pioneer-Venus Orbiter altimetry -- and data from Earth-based radar observations from the Arecibo radio telescope. Simulated color is used to enhance small-scale structures. The simulated hues are based on color images obtained by the Venera 13 and 14 landing craft. The bright feature near the center of the image is Ovda Regio, a mountainous region in the western portion of the great Aphrodite equatorial highland. The dark areas scattered across the Venusian plains consist of extremely smooth deposits associated with large meteorite impacts. The image was produced by the Solar System Visualization Project and the Magellan Science team at the Jet Propulsion Laboratory Multimission Image Processing Laboratory. The Magellan mission is managed by JPL for NASA's Office of Space Science.

1993-01-01

178

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

179

The development of studies of Venus  

Science.gov (United States)

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

Cruikshank, D. P.

1983-01-01

180

High Temperature, Wireless Seismometer Sensor for Venus  

Science.gov (United States)

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

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

2012-01-01

 
 
 
 
181

Laying bare Venus' dark secrets  

Energy Technology Data Exchange (ETDEWEB)

Ground-based IR observations of the dark side of Venus obtained in 1983 and 1985 with the Anglo-Australian Telescope are studied. An IR spectrum of Venus' dark side is analyzed. It is observed that the Venus atmosphere is composed of CO and radiation escapes only at 1.74 microns and 2.2 to 2.4 microns. The possible origin of the radiation, either due to absorbed sunlight or escaping thermal radiation, was investigated. These two hypotheses were eliminated, and it is proposed that the clouds of Venus are transparent and the radiation originates from the same stratum as the brighter portions but is weakened by the passage through the upper layer. The significance of the observed dark side markings is discussed.

Allen, D.A.

1987-10-01

182

Mantle convection and crustal evolution on Venus  

International Nuclear Information System (INIS)

Venus is probably similar to the Earth in that recycling of basaltic crust has been induced by the development of cratons: combinations of siliceous crust with high Mg:Fe mantle. Venus has less remaining energy sources at depth, but still enough to support the great plateaus, and to deliver appreciable heat close to the surface by convection. The main differences of Venus from the Earth arise from its lack of water, rather than higher temperatures. Lack of water (plus lower stress levels due to lesser energy) makes the upper mantle more viscous, and hence Venus tectonics more driven by bulk mantle, rather than boundary layer, characteristics. Making tectonics difficult to infer from Magellan imagery will be shallower and more widespread layers of weakness in crustal rocks obscuring the mantle-driven patterns

1990-01-01

183

Breast milk expression knowledge of school of medicine and faculty of health sciences students  

Directory of Open Access Journals (Sweden)

Full Text Available Background: When direct breastfeeding of the mother’s breast is not possible, expressing of human milk should be provided. Education and support to the mothers for breastfeeding by health care professionals have improved breastfeeding initiation and duration. The aim of the study was to determine the knowledge of the students of Gaziantep University School of Medicine and Faculty of Health Sciences about breast milk expression. Methods: This questionnaire based, cross-sectional study was performed in 857 students between March 2012 and June 2012. Results: The mean age of the participants (493 female/364 male was 21.1 ± 2.0 years (16-28. The eighty-six percent (736 of the participants heard something about expression of breast milk. The majority of these students agreed that breast milk can be expressed (642/736, 87.2% and stored (595/736, 80.8%. The seventy-six percent (452/595 of the students stated that, glass container should be used to store the expressed milk. Most of the students (549/736, 74.6% specified that breast milk expression is done by manual pump; followed by manual (277/736, 37.6% and by electric pump (241/736, 32.7%. Most of the students mentioned to give the expressed breast milk with a bottle, by heating in warm water (440/595, 73.94%; 418/595, 70.25%; respectively. Conclusion: These findings provide insight into the educational program of the School of Medicine and Faculty of Health Sciences for breast milk expression. The knowledge level of our students for breast milk expression is encouraging, despite inadequate experience in education programs.

Nilgun Col-Araz

2013-03-01

184

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 < or approx. =10_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 < or approx. =10_2_5 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 10_5--10_6 K in order of magnitude

1982-11-01

185

225 years of the Venus atmosphere investigations  

International Nuclear Information System (INIS)

Historical review of investigation into the Venus atmosphere is given. It begins from the discovery of planetary atmosphere made by a great Russian scientist Lomonosov in 1761 till the latest atmosphere investigations by means of the Vega-1 and Vega-2 descent vehicles in 1985 within the framework of the international project for studying. The Venus planet and Halley comet. Results of investigation into physical properties and chemical composition of the planetary atmosphere and surface are present in short

1986-01-01

186

Carl Sagan and the Exploration of Mars and Venus  

Science.gov (United States)

Inspired by childhood readings of books by Edgar Rice Burroughs, Carl Sagan's first interest in planetary science focused on Mars and Venus. Typical of much of his career he was skeptical of early views about these planets. Early in this century it was thought that the Martian wave of darkening, a seasonal albedo change on the planet, was biological in origin. He suggested instead that it was due to massive dust storms, as was later shown to be the case. He was the first to recognize that Mars has huge topography gradients across its surface. During the spacecraft era, as ancient river valleys were found on the planet, he directed studies of Mars' ancient climate. He suggested that changes in the planets orbit were involved in climate shifts on Mars, just as they are on Earth. Carl had an early interest in Venus. Contradictory observations led to a controversy about the surface temperature, and Carl was one of the first to recognize that Venus has a massive greenhouse effect at work warming its surface. His work on radiative transfer led to an algorithm that was extensively used by modelers of the Earth's climate and whose derivatives still dominate the calculation of radiative transfer in planetary atmospheres today. Carl inspired a vast number of young scientists through his enthusiasm for new ideas and discoveries, his skeptical approach, and his boundless energy. I had the privilege to work in Carl's laboratory during the peak of the era of Mars' initial exploration. It was an exciting time, and place. Carl made it a wonderful experience.

Toon, Owen B.; Condon, Estelle P. (Technical Monitor)

1997-01-01

187

The global resurfacing of Venus  

Science.gov (United States)

The impact cratering record on Venus is unique among the terrestrial planets. Fully 84% of the craters are in pristine condition, and only 12% are fractured. Remarkably, only 2.5% of the craters and crater-related features are embayed by lava, although intense volcanism and tectonism have affected the entire planet. Furthermore, the spatial and hypsometric distribution of the craters is consistent with a completely random one, including stochastic variations. Monte Carlo simulations of equilibrium resurfacing models result in a minimum of 17 times more embayed craters than observed, or unobserved nonrandom crater distributions for resurfacing areas between 0.03% and 100% of the planet's surface. These models also are not consistent with the number and nonrandom distribution of volcanoes, and the nonrandom distribution of embayed and heavily fractured craters. The constraints imposed by the cratering record strongly indicate that Venus experienced a global resurfacing event about 300 m.y. ago followed by a dramatic reduction of volcanism and tectonism. This global resurfacing event ended abruptly (less than 10 m.y.). The present crater population has accumulated since then and remains largely intact. Thermal history models suggest that similar global resurfacing events probably occured episodically in the past. We show that neither the present level and style of geologic activity nor anything less than global resurfacing could have produced the observed cratering record. The effects of recent geologic activity are much less than those of the earlier global resurfacing event, when the record of all the early heavy bombardment and much of the later light bombardment was erased from the surface by massive volcanism and tectonic activity. Episodic regional resurfacing events that had global effects also occurred on Earth (e.g., the mid-Cretaceous superplume) and probably on Mars. On Mars they may have triggered the catastrophic releases of water that formed the outflow channels.

Strom, Robert G.; Schaber, Gerald G.; Dawsow, Douglas D.

1994-01-01

188

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

1989-01-01

189

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  

Energy Technology Data Exchange (ETDEWEB)

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{sup +} 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} < O) magnetic hemisphere. Out of a total of 167 large O{sup +} 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.

Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA))

1989-02-01

190

Closing of Venus Flytrap by Electrical Stimulation of Motor Cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Electrical signaling and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since XIX century, but the exact mechanism of Venus flytrap closure is still unknown. We found that the electrical stimulus between a midrib and a lobe closes the Venus flytrap leaf by activating motor cells without mechanical stimulation of trigger hairs. The closing time of Venus flytrap by electrical stimulation of motor cells is 0.3 s, t...

Volkov, Alexander G.; Adesina, Tejumade; Jovanov, Emil

2007-01-01

191

Remote Raman - LIBS Geochemical Investigation under Venus Atmospheric Conditions  

Science.gov (United States)

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

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

2008-12-01

192

Lithospheric and atmospheric interaction on the planet Venus  

International Nuclear Information System (INIS)

Lithospheric and atmospheric interaction in the planet Venus are discussed. The following subject areas are covered: (1) manifestation of exogenic processes using photogeological data; (2) the chemical composition and a chemical model of the troposphere of Venus; (3) the mineral composition of surface rock on Venus; and (4) the cycles of volatile components

1989-01-02

193

Dual Balloon Concept for Lifting Payloads from the Surface of Venus  

Science.gov (United States)

Introduction: Two high-rated Venus mission concepts proposed in the National Science Foundation Decadal Survey require a balloon to lift payloads from Venusian surface to high altitudes: Venus Surface Sample Return (VESSR) and Venus In-Situ Explorer (VISE). In case of VESSR the payload is a canister with the surface sample plus a Venus ascent vehicle (VAV), which is a rocket that takes the sample into orbit for rendezvous with an Earth return vehicle. VISE is envisioned as a more limited precursor mission where the surface sample is only taken to high altitudes so that non time-critical analyses can be performed. From the balloon point of view, the only difference between these two missions is that the VESSR payload to be lifted is very much larger than VISE because of the inclusion of the VAV. A key problem is that at the time the decadal survey was published, no high temperature balloon technology existed to implement either mission. Prior technology development efforts had concentrated on a single balloon that could operate across the entire 0-60 km altitude range, tolerating both the sulfuric acid aerosols and the extreme temperatures of -10 to +460 C. However, this problem was unsolved because no combination of sufficiently lightweight balloon material and manufacturing (seaming) technology was ever found to tolerate the high temperatures at the surface.

Kerzhanovich, Viktor V.; Yavrouian, A. H.; Hall, J. L.; Cutts, J. A.

2005-01-01

194

Glory on Venus cloud tops and the unknown UV absorber  

Science.gov (United States)

We report on the implications of the observations of the glory phenomenon made recently by Venus Express orbiter. Glory is an optical phenomenon that poses stringent constraints on the cloud properties. These observations thus enable us to constrain two properties of the particles at the cloud tops (about 70 km altitude) which are responsible for a large fraction of the solar energy absorbed by Venus. Firstly we obtain a very accurate estimate of the cloud particles size to be 1.2 ?m with a very narrow size distribution. We also find that for the two observations presented here the clouds are homogenous, as far as cloud particles sizes are concerned, on scale of at least 1200 km. This is in contrast to previous estimates that were either local, from entry probes data, or averaged over space and time from polarization data. Secondly we find that the refractive index for the data discussed here is higher than that of sulfuric acid previously proposed for the clouds composition (Hansen, J.E., Hovenier, J.W. [1974]. J. Atmos. Sci. 31, 1137-1160; Ragent, B. et al. [1985]. Adv. Space Res. 5, 85-115). Assuming that the species contributing to the increase of the refractive index is the same as the unknown UV absorber, we are able to constrain the list of candidates. We investigated several possibilities and argue that either small ferric chloride (FeCl3) cores inside sulfuric acid particles or elemental sulfur coating their surface are good explanations of the observation. Both ferric chloride and elemental sulfur have been suggested in the past as candidates for the as yet unknown UV absorber (Krasnopolsky, V.A. [2006]. Planet. Space Sci. 54, 1352-1359; Mills, F.P. et al. [2007]. In: Esposito, L.W., Stofan, E.R., Cravens, T.E. (Eds.), Exploring Venus as a Terrestrial Planet, vol. 176. AGU Monogr. Ser., Washington, DC, pp. 73-100).

Markiewicz, W. J.; Petrova, E.; Shalygina, O.; Almeida, M.; Titov, D. V.; Limaye, S. S.; Ignatiev, N.; Roatsch, T.; Matz, K. D.

2014-05-01

195

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

196

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

197

Studies of Coronae and Large Volcanoes on Venus: Constraining the Diverse Outcomes of Small-Scale Mantle Upwellings on Venus  

Science.gov (United States)

Proxemy Research had a grant from NASA to perform science research on upwelling and volcanism on Venus. This was a 3 year Planetary Geology and Geophysics grant to E. Stofan, entitled Coronae and Large volcanoes on Venus. This grant closes on 12/31/05. Here we summarize the scientific progress and accomplishments of this grant. Scientific publications and abstracts of presentations are indicated in the final section. This was a very productive grant and the progress that was made is summarized. Attention is drawn to the publications and abstracts published in each year. The proposal consisted of two tasks, one examining coronae and one studying large volcanoes. The corona task (Task 1) consisted of three parts: 1) a statistical study of the updated corona population, with Sue Smrekar, Lori Glaze, Paula Martin and Steve Baloga; 2) geologic analysis of several specific groups of coronae, with Sue Smrekar and others; and 3) determining the histories and significance of a number of coronae with extreme amounts of volcanism, with Sue Smrekar. Task 2, studies of large volcanoes, consisted of two subtasks. In the first, we studied the geologic history of several volcanoes, with John Guest, Peter Grindrod, Antony Brian and Steve Anderson. In the second subtask, I analyzed a number of Venusian volcanoes with evidence of summit diking along with Peter Grindrod and Francis Nimmo.

Stofan, Ellen R.

2005-01-01

198

Meeting Venus:A Collection of Papers Presented at the Venus Transit Conference Tromsø 2012  

Digital Repository Infrastructure Vision for European Research (DRIVER)

On 2–3 June 2012, the University of Tromsø hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsø for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the s...

Aspaas, Per Pippin; Sterken, Christiaan

2013-01-01

199

Aerial electromagnetic sounding of the lithosphere of Venus  

Science.gov (United States)

Electromagnetic (EM) investigation depths are larger on Venus than Earth due to the dearth of water in rocks, in spite of higher temperatures. Whistlers detected by Venus Express proved that lightning is present, so the Schumann resonances ˜10-40 Hz may provide a global source of electromagnetic energy that penetrates ˜10-100 km. Electrical conductivity will be sensitive at these depths to temperature structure and hence thermal lithospheric thickness. Using 1D analytic and 2D numerical models, we demonstrate that the Schumann resonances—transverse EM waves in the ground-ionosphere waveguide—remain sensitive at all altitudes to the properties of the boundaries. This is in marked contrast to other EM methods in which sensitivity to the ground falls off sharply with altitude. We develop a 1D analytical model for aerial EM sounding that treats the electrical properties of the subsurface (thermal gradient, water content, and presence of conductive crust) and ionosphere, and the effects of both random errors and biases that can influence the measurements. We initially consider specified 1D lithospheric thicknesses 100-500 km, but we turn to 2D convection models with Newtonian temperature-dependent viscosity to provide representative vertical and lateral temperature variations. We invert for the conductivity-depth structure and then temperature gradient. For a dry Venus, we find that the error on temperature gradient obtained from any single local measurement is ˜100%—perhaps enough to distinguish "thick" vs. "thin" lithospheres. When averaging over thousands of kilometers, however, the standard deviation of the recovered thermal gradient is within the natural variability of the convection models, Schumann resonances to Schumann penetration depths are significantly larger. We conclude that EM sounding of the interior of Venus is feasible from a 55-km high balloon. Lithospheric thickness can be measured if the upper-mantle water content is low. If H 2O at hundreds of ppm is present, the deeper, temperature-sensitive structure is screened, but the "wet" nature of the upper mantle, as well as structure of the upper crust, is revealed.

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

2012-02-01

200

VENUS superconducting thin solenoid magnet  

International Nuclear Information System (INIS)

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

1986-05-12

 
 
 
 
201

Venus: radar determination of gravity potential.  

Science.gov (United States)

We describe a method for the determination of the gravity potential of Venus from multiple-frequency radar measurements. The method is based on the strong frequency dependence of the absorption of radio waves in Venus' atmosphere. Comparison of the differing radar reflection intensities at several frequencies yields the height of the surface relative to a reference pressure contour; combination with measurements of round-trip echo delays allows the pressure, and hence the gravity potential contour, to be mapped relative to the mean planet radius. Since calibration data from other frequencies are unavailable, the absorption-sensitive Haystack Observatory data have been analyzed under the assumption of uniform surface reflectivity to yield a gravity equipotential contour for the equatorial region and a tentative upper bound of 6 x 10(-4) on the fractional difference of Venus' principal equatorial moments of inertia. The minima in the equipotential contours appear to be associated with topographic minima. PMID:17739140

Shapiro, I I; Pettengill, G H; Sherman, G N; Rogers, A E; Ingalls, R P

1973-02-01

202

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

203

Isostatic compensation of equatorial highlands on Venus  

Science.gov (United States)

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

Kucinskas, Algis B.; Turcotte, Donald L.

1994-01-01

204

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

205

Are the clouds of Venus sulfuric acid.  

Science.gov (United States)

It is shown that strong aqueous sulfuric acid solutions have the right refractive index and freeze at Venusian cloud temperature, explain the dryness of the Venusian stratosphere, are consistent with some features of the Venusian IR spectrum, and do not absorb in highly reflecting areas of Venus. It is also indicated that such solutions should be produced by reactions between known atmospheric constituents and most sulfur-bearing rock at the Venusian surface temperature, and require only small amounts of sulfur consistent with its cosmic abundance and with the amounts of other volatile elements present in the atmosphere. It is believed therefore that the clouds of Venus consist of sulfuric acid solutions.

Young, A. T.

1973-01-01

206

Convection-driven tectonics on Venus  

Science.gov (United States)

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

Phillips, Roger J.

1990-01-01

207

Emplacement Scenarios for Volcanic Domes on Venus  

Science.gov (United States)

One key to understanding the history of resurfacing on Venus is better constraints on the emplacement timescales for the range of volcanic features visible on the surface. A figure shows a Magellan radar image and topography for a putative lava dome on Venus. 175 such domes have been identified with diameters ranging from 19 - 94 km, and estimated thicknesses as great as 4 km. These domes are thought to be volcanic in origin and to have formed by the flow of viscous fluid (i.e., lava) on the surface.

Glaze, Lori S.; Baloga, Steve M.; Stofan, Ellen R.

2012-01-01

208

Radiative energy balance of the Venus mesosphere  

Energy Technology Data Exchange (ETDEWEB)

An accurate radiative transfer model for line-by-line gaseous absorption, as well as for cloud absorption and multiple scattering, is used in the present calculation of solar heating and thermal cooling rates for standard temperature profiles and temperatures yielded by the Venera 15 Fourier Spectrometer Experiment. A strong dependency is noted for heating and cooling rates on cloud-structure variations. The Venus mesosphere is characterized by main cloud-cover heating and overlying-haze cooling. These results are applicable to Venus atmosphere dynamical models. 24 refs.

Haus, R.; Goering, H. (Heinrich-Hertz-Institut fuer Atmosphaerenforschung und Geomagnetismus, Berlin (German Democratic Republic))

1990-03-01

209

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.

210

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

211

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

Directory of Open Access Journals (Sweden)

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

T. L. Zhang

2009-11-01

212

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 α-chitin.

Paszota, Paulina; Escalante-Perez, Maria

2014-01-01

213

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

214

Pioneer Venus observations of the Venus dayglow spectrum 1250--1430 A  

Energy Technology Data Exchange (ETDEWEB)

The spectrum of the dayglow of Venus between 1250 and 1430 A has been measured by the Pioneer Venus Orbiter Ultraviolet Spectrometer. Four bands of the (14,v'') progression in the fourth positive system of carbon monoxide are identified and their excitation mechanism is shown to be fluorescent scattering of the solar Lyamn alpha line. The (14,3) and (14,4) bands at 1317 and 1354 A are blended with the atomic oxygen 1304 and 1356 A lines. The (14,5) band at 1392 A is a prominent unblended spectral feature in the Venus dayglow. This identification provides an additional remote sensing technique to determine the density distribution of carbon monoxide in the upper atmosphere of Venus.

Durrance, S.T.; Barth, C.A.; Ian, A.; Stewart, F.

1980-03-01

215

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

216

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

Science.gov (United States)

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

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

2013-12-01

217

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

218

Venus: Geochemical conclusions from the Magellan data  

Science.gov (United States)

Though the Magellan mission was not designed to collect geochemical or petrological information, it has done so nonetheless. Since the time of the Pioneer Venus mission it has been known that high-altitude (greater than 2.5-5 km) mountainous areas on Venus exhibit anomalously low radiothermal emissivity (e less than 0.6). Magellan has greatly refined and extended these observations. The low emissivity requires surface material in the uplands to have a mineralogical composition that gives it a high bulk dielectric constant, greater than 20. The dielectric constant of dry terrestrial volcanic rocks seldom exceeds 7. The high-dielectric character of high-altitude surface material cannot be a primary property of the local volcanic rock, because there is no reason why rock having the required special mineralogy would erupt only at high altitudes. Therefore it is a secondary property; the primary Venus rock has reacted with the atmosphere to form a mineralogically different surface layer, and the secondary minerals formed are controlled by the ambient temperature, which decreases with altitude on Venus. A further investigation of venusian mineralogy is presented.

Wood, J. A.

1992-01-01

219

Venus: A contrast in evolution to Earth  

International Nuclear Information System (INIS)

Of the planets, Venus and Earth are by far the most similar in primary properties, yet they differ markedly in secondary properties. A great impact into Earth is believed to have created its moon and removed its atmosphere; the lack of such an impact into Venus apparently led to a greatly differing atmospheric evolution. The lack of an ocean on Venus prevents the recycling of volatiles and inhibits subduction, so that its crust is probable more voluminous than Earth's, although distorted and quite variable in thickness. Venus's upper mantle appears to be depleted in both volatiles and energy sources because, in addition to the lack of volatile recycling, melts of mantel rocks are more dense than their solid matrix at pressures above 8 gigapascals and hence sink if they occur at depths below 250 kilometers. Appreciable energy sources persist at great depths to sustain the few great mountain complexes. The greatest current problem is reconciling the likelihood of a voluminous crust with indications of considerable strength at shallow depths of 20 to 100 kilometers

1990-03-09

220

Sulfuric acid in the Venus clouds.  

Science.gov (United States)

The extremely dry nature of the Venus upper atmosphere appears to demand the presence of an efficient desiccating agent as the chief constituent of the clouds of Venus. On the basis of polarization measures it is to be expected that this substance is present as spherical droplets, 1 to 2 microns in diameter, with a refractive index n of 1.46 plus or minus 0.02 at 3500A in the observed region of the atmosphere, with T about equal to 235 K. This substance must have ultraviolet, visible, and infrared reflection properties not inconsistent with the observed spectrum of Venus. Sulfuric acid, of about 86% by weight composition, roughly fulfills the first of these properties. The visible and ultraviolet transmission features of a thin layer of elemental bromine and hydrobromic acid dissolved in sulfuric acid somewhat resemble the Venus spectrum, up to 14 microns. The chemical process postulated for forming sulfuric acid involves the oxidation of sulfur and its compounds to sulfuric acid through the agency of elemental bromine produced by the photolytic decomposition of hydrogen bromide.

Sill, G. T.

1972-01-01

 
 
 
 
221

Estimates of lithospheric thickness on Venus  

Science.gov (United States)

Magellan altimetry data have revealed many examples of topographic flexure on Venus. Modeling of flexural features is of interest as it provides information on spatial (and for the earth, temporal) variations in lithospheric thickness. Lithospheric thickness may be determined solely from modeling topographic flexure or by combining gravity and topography data. On Venus even the highest resolution gravity is insufficient for modeling all but the very longest wavelength flexural features, so we rely heavily on altimetry data for information about lithospheric thickness. Sandwell and Schubert modeled flexure around four coronae and found lithospheric thicknesses h, in the range 35 - 70 km. Studies of several more flexural features suggests that these are typical of Aphrodite Terra and other chasmata regions on Venus. However lithospheric thicknesses associated with other regions are in the range 15-30 km. McKenzie et al. noted that part of Aphrodite Terra appeared similar in planform and morphology to the subduction zones of the East Indies on Earth. Other flexure studies using Magellan data have looked at smaller coronae (h = 5-30 km) and rifts (h = 8-20 km). It can be seen that the range of thicknesses suggested by studies to date is extremely large, and it is difficult to establish whether their mean is in agreement with that predicted by heat flow scaling arguments (h approximately 18 km). Here we present results from a global study of flexure on Venus, with particular emphasis on the variation in our results with different tectonic settings.

Johnson, C. L.; Sandwell, D. T.

1993-03-01

222

Solar activity and conjunctions of Venus  

Energy Technology Data Exchange (ETDEWEB)

Between 1856 and 1954, i.e. during 9 solar cycles, the Wolf numbers were significantly higher at superior conjunctions of Venus than an inferior conjunctions. The role of small isolated spots could be of some importance, but no theoretical explanation for the observed differences has been proposed.

Link, F.; Link, J. (Institut d' Astrophysique, 79 - Paris (France))

1983-06-20

223

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)

2008-01-01

224

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

Science.gov (United States)

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

1982-01-01

225

MSR, a multi-spectrum retrieval technique for spatially-temporally correlated or common Venus surface and atmosphere parameters  

Science.gov (United States)

A common way to regularize mathematical ill-posed retrieval problems in atmospheric remote sensing is the incorporation of single-spectrum Bayesian a priori mean values and standard deviations for the parameters to be retrieved, along with measurement and simulation error information. This decreases the probability to obtain unlikely parameter values. For a reliable evaluation of measurements with sparse spectral information content like Venus' nightside emissions in the infrared as acquired by the VIRTIS-M-IR instrument aboard ESA's Venus Express spacecraft, it can help to consider further a priori knowledge.

Kappel, David

2014-01-01

226

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

Science.gov (United States)

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

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

2014-05-01

227

Venus - Computer Simulated Global View Centered at 0 Degrees East Longitude  

Science.gov (United States)

This global view of the surface of Venus is centered at 0 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan Science team at the JPL Multimission Image Processing Laboratory, and is a single frame from a video released at the October 29, 1991, JPL news conference.

1992-01-01

228

Venus - Computer Simulated Global View Centered at 180 Degrees East Longitude  

Science.gov (United States)

This global view of the surface of Venus is centered at 180 degrees east longitude. Magellan synthetic aperture radar mosaics from the first cycle of Magellan mapping are mapped onto a computer-simulated globe to create this image. Data gaps are filled with Pioneer Venus Orbiter data, or a constant mid-range value. Simulated color is used to enhance small-scale structure. The simulated hues are based on color images recorded by the Soviet Venera 13 and 14 spacecraft. The image was produced by the Solar System Visualization project and the Magellan science team at the JPL Multimission Image Processing Laboratory and is a single frame from a video released at the October 29, 1991, JPL news conference.

1991-01-01

229

Science.  

Science.gov (United States)

This document contains the following papers on science instruction and technology: "A 3-D Journey in Space: A New Visual Cognitive Adventure" (Yoav Yair, Rachel Mintz, and Shai Litvak); "Using Collaborative Inquiry and Interactive Technologies in an Environmental Science Project for Middle School Teachers: A Description and Analysis" (Patricia…

Roach, Linda E., Ed.

230

A tectonic resurfacing model for Venus  

Science.gov (United States)

Two remarkable aspects of the population of impact craters on Venus are that craters at all sizes are indistinguishable from a random population and that the vast majority of craters have not been significantly modified by tectonic strain or by volcanic flows external to the crater rim, despite evidence from Magellan images that volcanic and tectonic features are widespread on Venus. One interpretation of these observations is that most of the surface dates from the end of a catastrophic global resurfacing event that ceased about 500 My ago, and that the small fraction of craters volcanically embayed or modified by deformation indicates that volcanic and tectonic activity subsequent to that time has been at much lower levels. An alternative model, in which resurfacing occurs episodically in patches a few hundred kilometers in extent and there is a wider spectrum of surface ages, also appears to be consistent with the characteristics of impact craters on Venus. A number of potential mechanisms for catastrophic resurfacing of Venus have been proposed, ranging from geologically sudden convective destabilization of the global lithosphere to strongly time-dependent heat flux and melt generation in the underlying mantle. In most of these geophysical models, resurfacing occurs implicitly or explicitly by volcanism. We explore the hypothesis that, at least in the geologically recent history of Venus, the primary resurfacing mechanism has been tectonic deformation rather than volcanism. We show how such a hypothesis provides at least as good an explanation of a wide range of observations as do volcanic resurfacing models. Finally, we explore the implications of tectonic resurfacing hypothesis for the controversy over the recent resurfacing history of the planet.

Solomon, Sean C.

1993-01-01

231

Protecting Venus from Asteroids, Comets, and Meteors  

Science.gov (United States)

It is well accepted that the dense, thick atmosphere of Venus prevents most small cosmic bodies from reaching the surface and forming craters. We have examined this atmospheric intervention in detail, incorporating the lessons learned from the extensive modeling of impactor deceleration and flattening motivated by the SL-9 impacts with Jupiter. We employ a "pancake" model, which best matches detailed code simulations of atmospheric energy deposition, and Schmidt-Holsapple crater scaling modified for complex (flattened) craters. We adopt the distributions of Venus-crossing asteroids and comets determined by E.M. Shoemaker and co-workers, as well as generalizations of these distributions. Our nominal simulation of the venusian crater record is shown below, calibrated to the total number of venusian craters (940). As nearly all craters on Venus are well-preserved and relatively uniformly distributed, such simulations constrain the age of the surface. The fit is reasonable, with a nominal crater retention age of approx. 700 Ma. The fit at the large-crater end is improved if the number of large asteroids is increased, which Shoemaker argues is in fact more representative of the long-term (over several 100 Ma) average, and if Halley-family comets are included. The ages we obtain under a variety of modeling choices that produce good fits (including using Shoemaker's preferred crater scaling) are approx. 700-900 Ma, substantially greater than the most widely cited age estimate in the literature (-300 Ma). The key difference is that we find very large depletions in the production of 20-30-km craters (see figure) compared with previous estimates, the size range at which atmospheric effects are often calibrated or assumed nearly negligible. As venusian global resurfacing recedes deeper into history, the likelihood that Venus is resting between bouts of activity diminishes. Venus, like Mars, may instead be dying or dead.

McKinnon, William B.; Zahnle, K. J.; Cuzzi, Jeffrey (Technical Monitor)

1996-01-01

232

Changes in Latitude, Changes in Attitude: U. S. Naval Observatory Observations of the Transit of Venus 1874-2012  

Science.gov (United States)

Of the seven transits of Venus for which unambiguous observations exist, four have occurred since the U.S. Naval Observatory (USNO) was established in 1844. With the Transit of Venus Commission, the USNO was heavily involved in observing the December 8, 1874, and December 6, 1882, events to establish an accurate value for the astronomical unit. In the 1960s, radar measurements began providing reliable Solar System distances. Scientific interest in these transits has now moved towards studies of the Venusian atmosphere and understanding transiting extrasolar planets, subjects in which the USNO is less active. In 1874, American Transit of Venus expeditions to Siberia, China, Japan, Tasmania, New Zealand, and the Kerguelen and Chatham Islands returned with 350 photographic plates. The 1882 missions collected 1,487 plates from Washington, DC; Florida; Texas; New Mexico; South Africa; Patagonia; Chile; and New Zealand. From the 1882 photographs, Harkness determined the astronomical unit to be 92,455,000 ± 123,400 miles (148,790,000 ± 198,600 km). On June 8, 2004, and June 5, 2012, the USNO hosted friends and family interested in seeing the transits of Venus. Both events were partially visible from Washington, DC while the Flagstaff station was only able to watch a portion of 2012 transit. The surviving 19th century equipment was returned to service to view this scientific curiosity. In 2012, one 5-inch (0.1-m) Alvan Clark refractor (#856) was able to observe its fourth transit of Venus from Washington despite clouds. Between the two locations, approximately 570 people participated. Other USNO astronomers made personal trips west to Hawaii and Alaska to share the event with the public. In 1882, Harkness mused on the scientific advances that had and would occur between transits of Venus. Like him, we can only wonder “What will be the state of science when the next transit season arrives” on December 11, 2117.

Bartlett, Jennifer L.; Chester, G.; Bosken, S.; Barron, E. G.

2013-01-01

233

Teaching Planetary Sciences at the Universidad del País Vasco in Spain: The Aula Espazio Gela and its Master in Space Science and Technology  

Science.gov (United States)

Planetary science is a highly multidisciplinary field traditionally associated to Astronomy, Physics or Earth Sciences Departments. Spanish universities do not generally offer planetary sciences courses but some departments give courses associated to studies on Astronomy or Geology. We show a different perspective obtained at the Engeneering School at the Universidad del País Vasco in Bilbao, Spain, which offers a Master in Space Science and Technology to graduates in Engineering or Physics. Here we detail the experience acquired in two years of this master which offers several planetary science courses: Solar System Physics, Astronomy, Planetary Atmospheres & Space Weather together with more technical courses. The university also owns an urban observatory in the Engineering School which is used for practical exercises and student projects. The planetary science courses have also resulted in motivating part of the students to do their master thesis in scientific subjects in planetary sciences. Since the students have very different backgrounds their master theses have been quite different: From writing open software tools to detect bolides in video observations of Jupiter atmosphere to the photometric calibration and scientific use or their own Jupiter and Saturn images or the study of atmospheric motions of the Venus' South Polar Vortex using data from the Venus Express spacecraft. As a result of this interaction with the students some of them have been engaged to initiate Ph.D.s in planetary sciences enlarging a relative small field in Spain. Acknowledgements: The Master in Space Science and Technology is offered by the Aula Espazio Gela at the Universidad del País Vasco Engineer School in Bilbao, Spain and is funded by Diputación Foral de Bizkaia.

Hueso, R.; Sanchez-Lavega, A.; Pérez-Hoyos, S.

2011-12-01

234

Communications Transceivers for Venus Surface Missions  

Science.gov (United States)

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

Force, Dale A.

2004-01-01

235

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

236

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

1982-01-01

237

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

1985-01-01

238

Cometary water on Venus - implications of stochastic impacts  

Energy Technology Data Exchange (ETDEWEB)

Attention is given to a Venus water abundance model, incorporating a stochastic cometary source and nonthermal hydrogen escape, that reproduces both the near-steady-state balance between escape loss and infall replenishment implied by Venus' short water lifetime, and the consistency of the observed deuterium-to-hydrogen ratio with a steady state. It is shown that the stochastic variability of each of these quantities is large. Water's quasi-steady state on Venus is judged to be mediated by comet impacts, leading to an obscuration of the early water history of Venus by the history of random impacts. 40 references.

Grinspoon, D.H.; Lewis, J.S.

1988-04-01

239

Is "Doing Science" in New Zealand Classrooms an Expression of Scientific Inquiry?  

Science.gov (United States)

In science education contexts there appears to be some consensus regarding the "doing" of science but less on the "what for". In this paper we compare and contrast scientists' view of "doing science" with the practice of "doing science" in New Zealand classrooms. After examining and critiquing these experiences with reference to New Zealand and…

Haigh, Mavis; France, Bev; Forret, Mike

2005-01-01

240

USGS Magellan stereomapping of Venus  

Science.gov (United States)

Introduction: The Magellan spacecraft went into Venus orbit in 1990 and by 1992 had made three complete cycles of polar orbits, each cycle covering the full range of longitudes. During this time the spacecraft obtained synthetic aperture radar (SAR) images of >96% of the planet at a resolution of 75 m/pixel [1]. Images taken with a decreased look angle from vertical, primarily during Cycle 3, provide stereo coverage of 17% of the planet when combined with images with same-side illumination from earlier in the mission. The stereo geometry of these images is extremely favorable, allowing elevation measurements with an estimated vertical precision (EP) of ˜10 m [2]. Magellan also obtained radar altimetry data at a horizontal resolution of 10x25 km, but photogrammetric analysis of the stereoimagery can yield topographic maps with a horizontal resolution more than an order of magnitude superior to that of the altimeter. We therefore developed software needed to utilize Magellan stereomagery on our photogrammetric workstation running commercial (SOCET SET R BAE) software [3,4]. The special hardware and SOCET SET software of this system provide many useful capabilities for stereomapping which can be extended by programming with the SOCET SET Developer's Toolkit (DEVKIT). The unique properties of the Magellan SAR data made it necessary to develop both translation software (of image data and supporting geometric information) and a sensor model [5]. Sensor Model: A sensor model is a function that specifies the transformation between image space (lines, samples) and object or ground coordinates (latitude, longitude, elevation). Our Magellan SAR sensor model includes all the physics of the Magellan imaging process, and accounts for the fact that during the Magellan imaging process, the images have been partially orthorectified as part of the correlation process: distortions attributable to topography were removed (but only those accounted for in the very low resolution pre-Magellan topo model) and must be put back in for the images to be matched correctly. The sensor model is designed to work with any combination of unmosaicked (F-BIDR), Mission-mosaicked (F- and C-MIDR), and USGS- mosaicked (FMAP) images. Information about the spacecraft position and velocity can be taken either from the F-BIDR headers or from separate NAIF SPICE kernels, letting us take advantage of post-mission improvements to the spacecraft ephemerides. In addition, the SOCET SET bundle-adjustment software can be used to estimate corrections to the ephemeris of each orbit. The form of the corrections, offsets in three orthogonal directions (along-track, across-track, and radial) suffices to correct the orbits over short arcs and reconcile SAR and altimetry observations. 1 Validation: We rigorously tested and accounted for potential error sources in our mapping process. We first addressed the well-known "cliffs," artifacts in the stereo data caused by discrepancies between the mission ephemeris solutions for successive blocks of orbits. Alex Konopliv of JPL reprocessed the entire set of orbital tracking and navigation data based on the detailed gravity observations from the end of the mission and claimed that errors in the new orbit solutions were decreased 1.5 orders of magnitude (to 50-200 m) in all 3 axes [6]. To produce seamless elevation data, we found it necessary to collect image-to-image tie point measurements and use these to estimate local position/velocity corrections to the orbits. We concluded that both the improved orbit/tracking solution and corrections based on the images themselves are necessary for successful stereomapping. Secondly, because we constrain elevations of control points based on the Magellan altimetry, the question arose of how sensitive our bundle adjustment process is to artifacts in the Magellan altimetry. (Elevations of individual altimeter footprints can be in error by several kilometers at high-contrast boundaries in the surface scattering function.) We demonstrated that the adjustable parameters allow each imag

Howington-Kraus, E.; Kirk, R. L.; Galuszka, D.; Redding, B.

 
 
 
 
241

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

Directory of Open Access Journals (Sweden)

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

M. Yamauchi

2011-03-01

242

Photochemistry of the atmosphere of Venus  

International Nuclear Information System (INIS)

The temperature variations in the atmospheric regions of Venus, the opaque clouds that absorb solar energy, and the ionospheric structure which is affected by solar UV flux and solar wind are examined. The circulation in the atmosphere is dominated by the retrograde zonal wind. The composition of the atmosphere which is CO_2 dominant, the varying ionosphere, clouds, and the surface of Venus are described. The photodissociation of CO_2 and hydrogen reactions in the thermosphere are studied. The changing day and night ionosphere is analyzed. The reactions which maintain the CO_2 atmosphere, and the influence of Cl and S on the strato-mesosphere are investigated. The relation between the troposphere and surface, and the chemistry of S, Cl, C, and H is examined. Hypotheses on the origin and evolution of the atmosphere are proposed. 132 references

1985-01-01

243

Venus y el fin del mundo  

Directory of Open Access Journals (Sweden)

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

Gonzalo Munévar

2006-01-01

244

Plasma channels in the Venus upper ionosphere  

Directory of Open Access Journals (Sweden)

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

H. Pérez de Tejada

2001-05-01

245

La Hieroglyphica y el Nacimiento de Venus  

Directory of Open Access Journals (Sweden)

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

González de Zarate, Jesús maría

2003-09-01

246

The estimate of the Venus magnetotail length  

Science.gov (United States)

We consider the process of flux tubes straightening in the Venus magnetotail on the basis of MHD model. We estimate the distance x t, where flux tubes are fully straightened due to the magnetic tension and the magnetotail with the characteristic geometry of field lines ("slingshot" geometry) ends. We investigate the influence of the transversal current sheet scale on the process of flux tubes straightening. The assumption of a thin current sheet allows to obtain a lower estimate of the magnetotail length, x t > 31 R V ( R V is the Venus radius), while the assumption of a broad current sheet allows to obtain an upper estimate, x t structure at x > x t.

Vasko, I. Yu.; Zelenyi, L. M.; Popov, V. Yu.

2014-03-01

247

Venus' Atla and Beta Regiones: Formation of Chasmata and Coronae  

Science.gov (United States)

Two likely areas of current tectonic and volcanic activity on Venus are Atla and Beta Regiones. Both are marked by pronounced topographic and geoid highs and each lies at the intersection of multiple rifts, i.e. the chasmata system. These regiones may be surface expressions of mantle upwellings. We examine the distribution, style, and attitude of coronae with respect to the two geoid highs. Coronae -- circular features unique to Venus -- could be caused by individual rising diapirs. Unlike Earth, Venus shows little evidence of horizontal motion, resulting in juxtaposition of coronae of all ages. Furthermore, there is little erosion to modify features. In our analysis, we use the three-tiered classification (based on the interior morphology) of 394 coronae, hence termed domal, circular, and calderic. These differing styles may reflect different stages in the evolution of a corona: from domal (youngest, possibly still active) features, progressing through increasing degrees of collapse to the calderic coronae. Comparing locations of these features shows the domal coronae average higher elevations, and calderic at lower elevations, with circular in between. Similar comparisons of other characteristics of the coronae, such as size, elongation, or dip, also show the progression from domal through calderic to circular. Both Atla and Beta are ringed by many coronae, but neither has coronae at or near their crests even within 20 m of their geoid highs. Coronae do occur in many rift segments, yet none occurs at or near these intersection points. Perhaps just as remarkable, Atla has a partial ring of four domal coronae, all within a 10-m geoid range of each other, whereas Beta has a partial ring of 6 or so calderic coronae between three and four 10-m contours from its crest. In both instances, the rings parallel geoid contour lines. These are the nearest coronae of their type to the crests. If corona formation is contemporaneous with the uplift process at Atla and Beta, and if the domal are younger than the calderic coronae, then Atla Regio is a recent feature and more active than Beta. This is in agreement with an independent assessment with modified craters. We use stratigraphy, crater modification, and relative tilt of craters and coronae to further test the timing of events implied in our model.

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

2004-12-01

248

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

249

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.)

1982-01-01

250

Venus clouds - A dirty hydrochloric acid model.  

Science.gov (United States)

The spectral and polarization data for Venus are consistent with micrometer-sized aerosol cloud particles of hydrochloric acid with soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The yellow color of the clouds could be due to absorption bands in the near UV involving ferric iron and chlorine complexes. It is pointed out that the UV features could arise from variations in the concentrations of iron and hydrochloric acid in the cloud particles.

Hapke, B.

1972-01-01

251

Gasdynamic modeling of the Venus magnetotail  

International Nuclear Information System (INIS)

A gasdynamic, convected magnetic field model of the solar wind interaction with Venus is used for the first time to model the steady state Venus magnetotail. Model results are directly compared with observations. The obstacle shape is an input parameter to this model. An initial obstacle shape, accurate on the dayside, is defined by balancing a hydrostatic equilibirum approximation for the internal plasma pressure with an external flow pressure approximation. These pressure approximations produce a cylindrical obstacle in the distant tail. A refined obstacle shape that attempts to balance this same internal pressure wuth the calculated external flow pressure tapers inward toward the tail axis downstream of the terminator. Cold fluid (photoionized planetary oxygen) is added to the flow about the tapered model obstacle. The resultant bulk plasma flow and magnetic field properties compare well with experimentally observed average proton velocity and magnetic field components in the magnetotail. The added oxygen plasma has significant number densities only within 1 Rv of the tail axis in the distant tail. The model predicts central magnetotail oxygen plasma number densities of about 0.2 cm-3 and temperatures on the order of 106 degree K, flowing tailward at speeds as low as 200 m/s. These properties are consistent with the flat, featureless Pioneer Venus Orbiter plasma analyzer spectra observed in the deep central tail. Pickup ions, in the test particle limit, match direct observations of tail pickup ions. These steady state model results suggest that the mass addition at Venus originating above the dayside ionopause is predominantly fluidlike and produces the slowed flows and severe field draping observed in the central distant tail

1991-04-01

252

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

253

Venus: the twin that went wrong  

Energy Technology Data Exchange (ETDEWEB)

Results obtained from recent Russian and American missions to the planet Venus are reviewed including observations made of noble gas abundances, the lack of water vapour in the planet's atmospheres, the extent and composition of the cloud layers, the structure of the planet's surface, its gravitational field and its climate. The impact of these observations on theories of the evolution of the Solar System, are considered.

Burgess, E.

1982-06-17

254

Comparing Volcanic Terrains on Venus and Earth: How Prevalent are Pyroclastic Deposits on Venus?  

Science.gov (United States)

In the last several years, astronomers have discovered several exoplanets with masses less than 10 times that of the Earth [1]. Despite the likely abundance of Earth-sized planets, little is known about the pathways through which these planets evolve to become habitable or uninhabitable. Venus and Earth have similar planetary radii and solar orbital distance, and therefore offer a chance to study in detail the divergent evolution of two objects that now have radically different climates. Understanding the extent, duration, and types of volcanism present on Venus is an important step towards understanding how volatiles released from the interior of Venus have influenced the development of the atmosphere. Placing constraints on the extent of explosive volcanism on Venus can provide boundary conditions for timing, volumes, and altitudes for atmospheric injection of volatiles. In addition, atmospheric properties such as near-surface temperature and density affect how interior heat and volatiles are released. Radar image data for Venus can be used to determine the physical properties of volcanic deposits, and in particular, they can be used to search for evidence of pyroclastic deposits that may result from explosive outgassing of volatiles. For explosive volcanism to occur with the current high atmospheric pressure, magma volatile contents must be higher than is typical on Earth (at least 2-4% by weight) [2,3]. In, addition, pyroclastic flows should be more prevalent on Venus than convective plumes and material may not travel as far from the vent source as it would on Earth [3]. Areas of high radar backscatter with wispy margins that occur near concentric fractures on Sapho Patera [4] and several coronae in Eastern Eistla Regio [5] have been attributed to collapse of eruption columns and runout of rough materials.

Carter, Lynn M.; Campbell, B. A.; Glaze, L. S.

2012-01-01

255

Pioneer Venus orbiter magnetic field and plasma observations in the Venus magnetotail  

International Nuclear Information System (INIS)

This study uses Pioneer Venus orbiter (PVO) magnetometer and plasma analyzer measurements to investigate the draped-field tail of Venus with an emphasis on determining the magnetic field and plasma conditions within the various tail regions and their dependence upon interplanetary magnetic field (IMF) orientation. For this purpose PVO orbits during which the spacecrafts high inclination trajectory took it through the central magnetotail were identified. Analysis of the observations taken during those orbits indicates that the distribution of plasma within the magnetotail is highly asymmetric and controlled by the orientation of the IMF. In the plasma sheet and adjacent lobe regions downstream of the Venus hemisphere over which the solar wind motional electric field, is directed away from the planet, PVO observed increasing fluxes of H+ and O+ as the spacecraft moves away from the tail axis toward the outer boundary of the tail. No O+ ions were observed outside of the magnetotail based upon the magnetic field data and the definitions adopted in this study. Downstream of the Venus hemisphere over which the solar wind motional electric field is directed in toward the planet, PVO does not usually observe significant fluxes of E/Q = 0-8 kV ions, except sometimes directly adjacent to the outer boundary of the tail. These results are interpreted as being due to the more efficient pick-up of newly ionized atmospheric neutrals over the Venus hemisphere where the initial gyromotion takes the newly created ions away from the dense, lower atmosphere where they might be lost due to scattering (Cloutier et al., 1974). The implications of these findings for the formation and maintenance of the Venus magnetotail are discussed

1989-03-01

256

Pioneer Venus orbiter magnetic field and plasma observations in the Venus magnetotail  

Energy Technology Data Exchange (ETDEWEB)

This study uses Pioneer Venus orbiter (PVO) magnetometer and plasma analyzer measurements to investigate the draped-field tail of Venus with an emphasis on determining the magnetic field and plasma conditions within the various tail regions and their dependence upon interplanetary magnetic field (IMF) orientation. For this purpose PVO orbits during which the spacecrafts high inclination trajectory took it through the central magnetotail were identified. Analysis of the observations taken during those orbits indicates that the distribution of plasma within the magnetotail is highly asymmetric and controlled by the orientation of the IMF. In the plasma sheet and adjacent lobe regions downstream of the Venus hemisphere over which the solar wind motional electric field, is directed away from the planet, PVO observed increasing fluxes of H{sup +} and O{sup +} as the spacecraft moves away from the tail axis toward the outer boundary of the tail. No O{sup +} ions were observed outside of the magnetotail based upon the magnetic field data and the definitions adopted in this study. Downstream of the Venus hemisphere over which the solar wind motional electric field is directed in toward the planet, PVO does not usually observe significant fluxes of E/Q = 0-8 kV ions, except sometimes directly adjacent to the outer boundary of the tail. These results are interpreted as being due to the more efficient pick-up of newly ionized atmospheric neutrals over the Venus hemisphere where the initial gyromotion takes the newly created ions away from the dense, lower atmosphere where they might be lost due to scattering (Cloutier et al., 1974). The implications of these findings for the formation and maintenance of the Venus magnetotail are discussed.

Slavin, J.A. (NASA Goddard Space Flight Center, Greenbelt, MD (USA)); Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA)); Smith, E.J. (California Institute of Technology, Pasadena (USA))

1989-03-01

257

Venus climate stability and volcanic resurfacing rates  

Science.gov (United States)

The climate of Venus is to a large degree controlled by the radiative properties of its massive atmosphere. In addition, outgassing due to volcanic activity, exospheric escape processes, and surface/atmosphere interactions may all be important in moderating the abundances of atmospheric CO2 and other volatiles. We have developed an evolutionary climate model for Venus using a systems approach that emphasizes feedbacks between elements in the climate system. Modules for atmospheric radiative transfer, surface/atmosphere interactions, tropospheric chemistry, and exospheric escape processes have so far been developed. Climate feedback loops result from interconnections between modules, in the form of the environmental parameters pressure, temperature, and atmospheric mixing ratios. The radiative transfer module has been implemented by using Rosseland mean opacities in a one dimensional grey radiative-convective model. The model has been solved for the static (time independent) case to determine climate equilibrium points. The dynamics of the model have also been explored by employing reaction/diffusion kinetics for possible surface atmosphere heterogeneous reactions over geologic timescales. It was found that under current conditions, the model predicts that the climate of Venus is at or near an unstable equilibrium point. The effects of constant rate volcanism and corresponding exsolution of volatiles on the stability of the climate model were also explored.

Bullock, M. A.; Grinspoon, D. H.; Pollack, J. B.

1994-01-01

258

Venus round trip using solar sail  

Science.gov (United States)

Trajectory optimization and simulation is performed for Venus round trip (VeRT) mission using solar sail propulsion. Solar gravity is included but atmospheric drag and shadowing effects are neglected in the planet-centered escape and capture stages. The spacecraft starts from the Geostationary orbit (GEO) at a predetermined time to prepare a good initial condition for the Earth-Venus transfer, although the launch window is not an issue for spacecraft with solar sails. The Earth-Venus phase and the return trip are divided into three segments. Two methods are adopted to maintain the mission trajectory for the VeRT mission and then compared through a numerical simulation. According to the first approach, Planet-centered and heliocentric maneuvers are modeled using a set of blended analytical control laws instead of the optimal control techniques. The second procedure is the Direct Attitude Angle Optimization in which the attitude angles of the solar sail are adopted as the optimization variables during the heliocentric transfer. Although neither of the two methods guarantees a globally optimal trajectory, they are more efficient and will produce a near-optimal solution if employed properly. The second method has produced a better result for the minimum-time transfer of the VeRT mission demonstrating the effectiveness of the methods in the preliminary design of the complex optimal interplanetary orbit transfers.

Zhu, KaiJian; Zhang, RongZhi; Xu, Dong; Wang, JiaSong; Li, ShaoMin

2012-08-01

259

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.

2013-01-01

260

Multispectrum retrieval techniques applied to Venus deep atmosphere and surface problems  

Science.gov (United States)

The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard ESA's Venus Express is continuously collecting nightside emission data (among others) from Venus. A radiative transfer model of Venus' atmosphere in conjunction with a suitable retrieval algorithm can be used to estimate atmospheric and surface parameters by fitting simulated spectra to the measured data. Because of the limited spectral resolution of VIRTIS-M-IR-spectra, that have been used so far, many different parameter sets can explain the same measurement equally well. As a common regulative measure, reasonable a priori knowledge of some parameters is applied to suppress solutions implausibly far from the expected range. It is beneficial to introduce a parallel coupled retrieval of several measurements. Since spa-tially and temporally contiguous measurements are not expected to originate from completely unrelated parameters, an assumed a priori correlation of the parameters during the retrieval can help to reduce arbitrary fluctuations of the solutions, to avoid subsidiary solutions, and to attenuate the interference of measurement noise by keeping the parameters close to a gen-eral trend. As an illustration, the resulting improvements for some swaths on the Northern hemisphere are presented. Some atmospheric features are still not very well constrained, for instance CO2 absorption under the extreme environmental conditions close to the surface. A broad band continuum due to far wing and collisional induced absorptions is commonly used to correct individual line absorption. Since the spectrally dependent continuum is constant for all measurements, the retrieval of parameters common to all spectra may be used to give some estimates of the continuum absorption. These estimates are necessary, for example, for the coupled parallel retrieval of a consistent local cloud modal composition, which in turn enables a refined surface emissivity retrieval. We gratefully acknowledge the support from the VIRTIS/Venus Express Team, from ASI, CNES, CNRS, and from the DFG funding the ongoing work.

Kappel, David; Arnold, Gabriele; Haus, Rainer

 
 
 
 
261

Secreted major Venus flytrap chitinase enables digestion of Arthropod prey.  

Science.gov (United States)

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. PMID:24275507

Paszota, Paulina; Escalante-Perez, Maria; Thomsen, Line R; Risør, Michael W; Dembski, Alicja; Sanglas, Laura; Nielsen, Tania A; Karring, Henrik; Thøgersen, Ida B; Hedrich, Rainer; Enghild, Jan J; Kreuzer, Ines; Sanggaard, Kristian W

2014-02-01

262

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

263

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)

2003-10-01

264

Helium on Venus: implications for uranium and thorium  

Energy Technology Data Exchange (ETDEWEB)

Helium is removed at an average rate of 10/sup 6/ atoms per square centimeter per second from Venus's atmoshere 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 abundance of crustal uranium and thorium.

Prather, M.J.; McElroy, M.B.

1983-04-22

265

The Venus nitric oxide night airglow: Model calculations based on the Venus thermospheric general circulation model  

Energy Technology Data Exchange (ETDEWEB)

Pioneer Venus (PV) orbiter ultraviolet spectrometer (OUVS) images of the nightside airglow in the (0, 1) {delta} band of nitric oxide showed a maximum whose average location was at 0200 local solar time just south of the equator. The average airglow brightness calculated over a portion of the nightside for 35 early orbits during the Pioneer Venus mission was a factor of 4 lower than this maximum. Recent recalibration of the PV OUVS instrument and reanalysis of the data yield new values for this statistical maximum (1.9 {plus minus} 0.6 kR) and the nightside average (400-460 {plus minus} 120 R) nightglow. This emission is produced by radiative recombination of N and O atoms transported from their source on the dayside to the nightside by the Venus thermospheric circulation. The Venus Thermospheric General Circulation Model (VTGCM) has been extended to incorporate odd nitrogen chemistry in order to examine the dynamical and chemical processes required to give rise to this emission. Its predictions of dayside N atom densities are also compared with empirical models based on Pioneer Venus measurements. Calculations are presented corresponding to OUVS data taken during solar maximum. The average production of nitrogen atoms on the dayside is about 9.0 {times} 10{sup 9} atoms cm{sup {minus}2} s{sup {minus}1}. Approximately 30% of this dayside source is required for transport to the nightside to yield the observed dark-disk nightglow features. The statistical location and intensity of the bright spot are well reproduced, as well as the altitude of the airglow layer. The importance of the large-scale transport and eddy diffusion on the global N({sup 4}S) distribution is also evaluated.

Bougher, S.W. (Univ. of Arizona, Tucson (United States)); Gerard, J.C. (Univ. de Liege, Ougree-Liege (Belgium)); Stewart, A.I.F.; Fesen, C.G. (Univ. of Colorado, Boulder (United States))

1990-05-01

266

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.

2011-04-01

267

Mars, Venus and Gray: Gender Communication  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This research tests the propositions relating to gender communication by Gray (1992) in his book titled “Men are from Mars, Women are from Venus

Kamarul Zaman Ahmad; Kalaiselvee Rethinam

2010-01-01

268

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)

1998-09-07

269

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

270

Croconic acid - An absorber in the Venus clouds  

Energy Technology Data Exchange (ETDEWEB)

The absorbing species responsible for the UV cloud features and pale yellow hue of the Venus clouds is presently suggested to be the carbon monoxide-polymer croconic acid, which strongly absorbs in the blue and near-UV. Laboratory absorption-coefficient measurements of a dilute solution of croconic acid in sulfuric acid are used as the bases of cloud-scattering models; the Venus planetary albedo's observed behavior in the blue and near-UV are noted to be qualitatively reproduced. Attention is given to a plausible croconic acid-production mechanism for the Venus cloudtop region. 34 references.

Hartley, K.K.; Wolff, A.R.; Travis, L.D.

1989-02-01

271

Venus geology and geophysics: a review of some recent studies  

Energy Technology Data Exchange (ETDEWEB)

The nature of the surface of Venus is being revealed by a series of investigations using spacecraft observations and measurements from the Soviet and US space probes and Earth-based radar telescope observations. This paper reviews a series of recent studies on the global properties of Venus, the characteristics of the Venera and Vega landing sites, and the geological and geophysical processes operating to form and modify the surface of Venus. Emphasis is placed on studies reported at the series of Brown University-Vernadsky Institute microsymposia.

Head, J.W.; Crumpler, L.C.; Bindschadler, D.L.; Stofan, E.R.; Vorder Bruegge, R.W.; Campbell, D.B.

1987-10-01

272

Venus - Concentrations of radar-reflective minerals by wind  

International Nuclear Information System (INIS)

The effectiveness of wind in concentrating minerals with high radar reflectiveness on the surface of Venus is investigated experimentally in the Venus Wind Tunnel (Greeley et al., 1984) under CO2 densities typical of Venusian conditions. Density sorting of sand particles during the formation of microdunes is demonstrated, and calculations show that wind-blown deposits of dense conductive material such as ilmenite need to be only a few cm thick to account for the local enhancements of radar reflectivity observed by Pioneer Venus at wavelength 17 cm. 28 refs

1991-01-01

273

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

2008-04-01

274

Impact craters and Venus resurfacing history  

Science.gov (United States)

The history of resurfacing by tectonism and volcanism on Venus is reconstructed by means of an analysis of Venusian impact crater size-frequency distributions, locations, and preservation states. An atmospheric transit model for meteoroids demonstrates that for craters larger than about 30 km, the size-frequency distribution is close to the atmosphere-free case. An age of cessation of rapid resurfacing of about 500 Ma is obtained. It is inferred that a range of surface ages are recorded by the impact crater population; e.g., the Aphrodite zone is relatively young. An end-member model is developed to quantify resurfacing scenarios. It is argued that Venus has been resurfacing at an average rate of about 1 sq km/yr. Numerical simulations of resurfacing showed that there are two solution branches that satisfy the completely spatially random location restraint for Venusian craters: a is less than 0.0003 (4 deg diameter circle) and a is greater than 0.1 (74 deg diameter circle).

Phillips, Roger J.; Raubertas, Richard F.; Arvidson, Raymond E.; Sarkar, Ila C.; Herrick, Robert R.; Izenberg, Noam; Grimm, Robert E.

1992-01-01

275

The Cold Storage of Venus Nectarin Cultivars  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to determine storage and shelf life of Venus nectarine cultivar grown inMersin (Tarsus/Yenice. Fruits were kept at 0°C and %85-90ºC relative humidity for 8 weeks. In addition,three replicates of fruits removed from storage room at a week interval were kept at 20°C and %65-70ºCrelative humidity for 6 days. Percent weight loss, skin color (L*, a*, b*, fruit flesh firmness (kg force, totalsoluble solids (%, pH, titretable acidity (g malic acid / 100 ml, physiological and fungal disorders weredetermined in the fruit samples taken during cold storage at a week interval and those kept at 20°C at a twodayinterval. Weight loss increased during storage and reached to about 5% at the end of storage. Fruit fleshfirmness decreased, but still remained above 4 kg-force at the end of 8-week storage. Total soluble solid (%increased while titretable acidity (% decreased. As the storage period was extended the shelf life wasshortened. Venus nectarine cultivars could be kept at 0°C and 85-90% relative humidity for 7 weeks andcould have 4-day shelf life after cold storage.

M. Celik

2006-09-01

276

Evaluation of Long Duration Flight on Venus  

Science.gov (United States)

An analysis was performed to evaluate the potential of utilizing either an airship or aircraft as a flight platform for long duration flight within the atmosphere of Venus. In order to achieve long-duration flight, the power system for the vehicle had to be capable of operating for extended periods of time. To accomplish these, two types of power systems were considered, a solar energy-based power system utilizing a photovoltaic array as the main power source and a radioisotope heat source power system utilizing a Stirling engine as the heat conversion device. Both types of vehicles and power systems were analyzed to determine their flight altitude range. This analysis was performed for a station-keeping mission where the vehicle had to maintain a flight over a location on the ground. This requires the vehicle to be capable of flying faster than the wind speed at a particular altitude. An analysis was also performed to evaluate the altitude range and maximum duration for a vehicle that was not required to maintain station over a specified location. The results of the analysis show that each type of flight vehicle and power system was capable of flight within certain portions of Venus s atmosphere. The aircraft, both solar and radioisotope power proved to be the most versatile and provided the greatest range of coverage both for station-keeping and non-station-keeping missions.

Landis, Geoffrey A.; Colozza, Anthony J.

2006-01-01

277

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

Science.gov (United States)

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

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

2013-11-01

278

Experimental Reconstruction of Lomonosov's Discovery of Venus's Atmosphere with Antique Refractors During the 2012 Transit of Venus  

CERN Document Server

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

Koukarine, Alexandre; Petrunin, Yuri; Shiltsev, Vladimir

2012-01-01

279

Position and shape of the Venus bow shock: Pioneer Venus Orbiter observations  

International Nuclear Information System (INIS)

In this study magnetometer data from the Poineer Venus Orbiter is used to examine the position and shape of this planet's bow shock. Utilizing crossings identified on 86 occasions during the first 65 orbits a mean shock surface is defined for sun-Venus-satellite angles of 60--110 0. Both the shock shape and variance in location are found to be very similar to the terrestrial case for the range in SVS angle considered. However, while the spread in shock positions at the earth is due predominantly to the magnetopause location varying in response to solar wind dynamic pressure, ionopause altitude variations can have little effect on total obstacle radius. Thus, the Cytherean shock is sometimes observed much closer to or farther from the planet than previously predicted by gasdynamic theory applied to the deflection of flow about a blunt body which acts neither as source nor sink for any portion of the flow

1979-01-01

280

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

International Nuclear Information System (INIS)

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. 34 references

1985-01-01

 
 
 
 
281

Prediction of neutron embrittlement in the reactor pressure vessel. Venus-1 and Venus-3 benchmarks  

International Nuclear Information System (INIS)

The OECD/NEA Task Force on Computing Radiation Dose and Modelling of Radiation-Induced Degradation of Reactor Components (TFRDD) launched two international blind intercomparison exercises to examine the current computation techniques used in NEA Member countries for calculating neutron and gamma doses to reactor components. Various methodologies and different nuclear data were applied to predict dose rates in the Belgian VENUS-1 and three-dimensional VENUS-3 configurations for comparison with measured data. This report provides the detailed results from the two benchmarks.The exercise revealed that three-dimensional neutron fluence calculations provide results that are significantly more accurate than those obtained from two-dimensional calculations. Performing three-dimensional calculations is technically feasible given the power of today's computers. (author)

2000-01-01

282

Vertical profiling of SO 2 and SO above Venus' clouds by SPICAV/SOIR solar occultations  

Science.gov (United States)

New measurements of sulfur dioxide (SO 2) and monoxide (SO) in the atmosphere of Venus by SPICAV/SOIR instrument onboard Venus Express orbiter provide ample statistics to study the behavior of these gases above Venus' clouds. The instrument (a set of three spectrometers) is capable to sound atmospheric structure above the clouds in several observation modes (nadir, solar and stellar occultations) either in the UV or in the near IR spectral ranges. We present the results from solar occultations in the absorption ranges of SO 2 (190-230 nm, and at 4 ?m) and SO (190-230 nm). The dioxide was detected by the SOIR spectrometer at the altitudes of 65-80 km in the IR and by the SPICAV spectrometer at 85-105 km in the UV. The monoxide's absorption was measured only by SPICAV at 85-105 km. We analyzed 39 sessions of solar occultation, where boresights of both spectrometers are oriented identically, to provide complete vertical profiling of SO 2 of the Venus' mesosphere (65-105 km). Here we report the first firm detection and measurements of two SO 2 layers. In the lower layer SO 2 mixing ratio is within 0.02-0.5 ppmv. The upper layer, also conceivable from microwave measurements by Sandor et al. (Sandor, B.J., Todd Clancy, R., Moriarty-Schieven, G., Mills, F.P. [2010]. Icarus 208, 49-60) is characterized by SO 2 increasing with the altitude from 0.05 to 2 ppmv, and the [SO 2]/[SO] ratio varying from 1 to 5. The presence of the high-altitude SO x species could be explained by H 2SO 4 photodissociation under somewhat warmer temperature conditions in Venus mesosphere. At 90-100 km the content of the sulfur dioxide correlates with temperature increasing from 0.1 ppmv at 165-170 K to 0.5-1 ppmv at 190-192 K. It supports the hypothesis of SO 2 production by the evaporation of H 2SO 4 from droplets and its subsequent photolysis at around 100 km.

Belyaev, Denis A.; Montmessin, Franck; Bertaux, Jean-Loup; Mahieux, Arnaud; Fedorova, Anna A.; Korablev, Oleg I.; Marcq, Emmanuel; Yung, Yuk L.; Zhang, Xi

2012-02-01

283

Depths of Extended Crater-related Deposits on Venus  

Science.gov (United States)

We examine crater-related parabolic deposits on Venus with Magellan radiophysical data. We found that their maximal thickness is a few meters. Thin mantles are not seen in SAR images but are detectable in emissivity maps.

Bondarenko, N. V.; Head, J. W., III

2004-03-01

284

Rift System Architecture on Venus and Implications for Lithospheric Structure  

Science.gov (United States)

Terrestrial continental rifts are half graben, with a master boundary fault on only 1 side of the rift basin. Devana Chasma on Venus has long segments with full graben morphologies (2 boundary faults), indicating differences in lithosphere structure.

Kiefer, W. S.

2014-05-01

285

VENUS-F: A fast lead critical core for benchmarking  

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-07-01

286

Geologic Map of the Meskhent Tessera Quadrangle (V-3), Venus  

Science.gov (United States)

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the Venusian atmosphere on October 12, 1994. Magellan Mission objectives included (1) improving the knowledge of the geological processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving the knowledge of the geophysics of Venus by analysis of Venusian gravity. The Meskhent Tessera quadrangle is in the northern hemisphere of Venus and extends from lat 50 degrees to 75 degrees N. and from long 60 degrees to 120 degrees E. In regional context, the Meskhent Tessera quadrangle is surrounded by extensive tessera regions to the west (Fortuna and Laima Tesserae) and to the south (Tellus Tessera) and by a large basinlike lowland (Atalanta Planitia) on the east. The northern third of the quadrangle covers the easternmost portion of the large topographic province of Ishtar Terra (northwestern map area) and the more localized upland of Tethus Regio (northeastern map area).

Ivanov, Mikhail A.; Head, James W., III

2008-01-01

287

VENUS-F: A fast lead critical core for benchmarking  

International Nuclear Information System (INIS)

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

2011-05-22

288

A New Approach to Inferences for Pancake Domes on Venus  

Science.gov (United States)

Figure 1 shows a radar image and topography for flat-topped, steep-sided "pancake" domes on Venus. At least 145 such domes have been identified on Venus [I] and are thought to be volcanic in origin [2]. Based on analysis of the dome surfaces, [3] suggested that only the late stage surface fractures are preserved, indicating entrainment and annealing of fractures during emplacement, consistent with a basaltic composition. Figure 1 shows a radar image and topography for flat-topped, steep-sided "pancake" domes on Venus. At least 145 such domes have been identified on Venus [I] and are thought to be volcanic in origin [2]. Based on analysis of the dome surfaces, [3] suggested that only the late stage surface fractures are preserved, indicating entrainment and annealing of fractures during emplacement, consistent with a basaltic composition.

Glaze, Lori S.; Baloga, Steve M.; Stofan, Ellen R.

2008-01-01

289

On properties of the Venus ionosphere and its sources  

International Nuclear Information System (INIS)

Properties of the day- and nighttime venus ionosphere and some possible sources of its ionization are considered. Differences in measurement results of different experiments carried out at space probes and results of upper ionosphere observations by radioeclipse methods are discussed. It is shown that the satisfactory quantitative description of the Venus ionosphere as a whole is impossible. As for as the fact of the existence of ionizing flows of electrons with energies of an order of several tens of electronvolts in the nighttime Venus ionosphere is reliably established both by the Soviet and American measurements, and the value of these flows is sufficient for creation in the surroundings of the main ionization maximum electron concentrations compared with the observed ones, than any model of the nighttime Venus ionosphere should take into account the effect of the given electron flows

1986-01-01

290

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)

2006-09-10

291

Hot spot heat transfer - Its application to Venus and implications to Venus and earth  

Science.gov (United States)

Using a model that gives a relationship between surface elevation, lithospheric thickness, and heat flux, the hot spot heat loss mechanism is tested for Venus. The mechanism is found to readily explain the predicted heat loss of the planet with a modest number of hot spots (of the order of 35). Lithospheric thickness variations can explain approximately 93 percent of the mapped topography of Venus. Above a radius of 6053 km, additional compensation is required, and this can be effected by incorporating a variable thickness crust into the model. If it is assumed that the crust is generated on the crests of the hot spots, probably by processes associated with volcanism, the model is consistent with nearly 99 percent of the mapped topography of Venus. In addition, the model is basically consistent with available gravity data and interpretations that suggest compensated topography and great depths of compensation (100-1000 km) for the midlatitudes of the planet. It is thought that the approximately 1 percent of the topography not explained by hot spot crustal generation is compensated at a shallower depth primarily by variations in crustal thickness that are not directly related to hot spot volcanism.

Morgan, P.; Phillips, R. J.

1983-01-01

292

LHD bootstrap current coefficient calculations with the VENUS + ?f code  

International Nuclear Information System (INIS)

Normalized bootstrap current coefficients are calculated for Large Helical Device (LHD, Japan) plasma configurations with different magnetic axis positions using the VENUS + ?f code. The dependences on the different collisionality regimes (over the full experimental range of LHD plasma discharges) and the plasma radii are presented. The comparison of the VENUS + ?f, SPBSC and DKES codes results is shown. The approach to the LHD experimental results is discussed. The bootstrap current effect on the iota=1 islands is considered. (author)

2008-07-01

293

Nature of the magnetic flux ropes in the Venus ionosphere  

Energy Technology Data Exchange (ETDEWEB)

The onset of gutter instability at the moving, accelerating ionopause on Venus may allow magnetic flux tubes of solar wind to penetrate the interior of the ionosphere. As the ionospheric ions cross the lateral tube walls, an axial current of solar-wind electrons will enter, twisting the field lines into a rope. Such a mechanism would explain data recorded on the Pioneer Venus mission.

Dubinin, E.M.; Izrailevich, P.L.; Podgornyi, I.M.; Shkol' nikova, S.I.

1980-03-01

294

The multistring model VENUS for ultrarelativistic heavy ion collisions  

Energy Technology Data Exchange (ETDEWEB)

The event generator VENUS is based on a multistring model for heavy ion collisions at ultrarelativistic energies. The model is a straightforward extension of a successful model for soft proton-proton scattering, the latter one being consistent with e/sup )plus/)e/sup )minus/) annihilation and deep inelastic lepton scattering. Comparisons of VENUS results with pA and recent AA data alow some statements about intranuclear cascading. 18 refs., 7 figs

Werner, K.

1988-02-01

295

Viscous flow circulation of the solar wind behind Venus  

Energy Technology Data Exchange (ETDEWEB)

A latitudinal circulation model of solar wind flow in the near wake of Venus is presented. It is shown that solar wind fluxes entering through the polar terminator can be viscously forced to lower latitutdes. The resulting motion produces a downstream elongation of the nightside polar ionosphere out to the downstream extension of the middle- and low-latitude ionopause. The geometry suggested by this flow circulation model provides a simple explanation of the ionospheric bulge inferred from the Pioneer Venus observations.

Perez-de-Tejada, H.

1980-02-29

296

Topic of the moment - the transit of Venus  

... The transit of Venus is much like a solar eclipse, with the planet crossing in front of the Sun as viewed from Earth. However while the Moon can completely obscure the Sun’s disc, Venus, being much further away, appears as a small black dot slowly making its way across it over the course of six to seven hours. Like eclipses, however, the event ...

297

A Pyroclastic Flow Deposit on Venus  

Science.gov (United States)

Explosive volcanism on Venus is severely inhibited by its high atmospheric pressure and lack of water. This paper shows that a deposit located near 16°S, 144°E, here referred to as Scathach Fluctus, displays a number of morphological characteristics consistent with a pyroclastic flow deposit. These characteristics, particularly its lack of channelisation and evidence for momentum rather than cooling limited flow length, contrast with fissure-fed lava flow deposits. The total erupted volume is estimated to have been between 225 km3 and 875 km3 but this may have been emplaced in more than one event. Interaction between Scathach Fluctus and a small volcanic cone constrain the flow velocity to 48 m s-1 and plausible volatile concentrations to at least 1.8 wt% H2O, 4.3 wt% CO2 or 6.1 wt% SO2, the latter two implying magma sourced directly from the mantle. The deposit has radar characteristics, particularly an exponential backscatter function, that are similar to those of nearly half the planetary surface, implying that pyroclastic deposits may be much more common on Venus than has been recognised to date, and suggesting both a relatively volatile-rich mantle and a volcanic source for atmospheric SO2. Unfortunately, because the plains usually lack clear flow boundaries and structures, the features diagnostic of a high momentum flow - linear undulating deposits that lack channel morphology, cross narrow graben without deviation, climb obstacles and show evidence for parabolic flow out from steep drops - may not be identifiable. Thus, while pyroclastic flows may be common on Venus, Scathach Fluctus may, indeed, become the only proven example from Magellan data. False colour image of Scathach Fluctus using data from Cycle 1 (left-looking), Cycle 2 (right-looking) and passive emissivity combined to enhance the impression of relief in the grey scale image, overlain with colour-coded derived asperity height, defined as surface roughness at the scale-length of the Magellan radar wavelength (126 mm).

Ghail, R.; Wilson, L.

2013-12-01

298

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

299

Dynamic model of Venus's gravity field  

Energy Technology Data Exchange (ETDEWEB)

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

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

1984-08-01

300

Surface age of venus: use of the terrestrial cratering record  

Energy Technology Data Exchange (ETDEWEB)

The average crater age of Venus' northern hemisphere may be less than 250 m.y. assuming equivalence between the recent terrestrial cratering rate and that on Venus for craters greater than or equal to 20 km in diameter. For craters larger than this threshold size, below which crater production is significantly affected by the Venusian atmosphere, there are fairly strong observational grounds for concluding that such an equivalence in cratering rates on Venus and Earth may exist. However, given the uncertainties in the role of both active and inactive comet nuclei in the cratering history of Earth, we conclude that the age of the observed surface in the northern hemisphere of Venus could be as great as the 450-m.y. mean age of the Earth's crust. The observed surface of Venus might be even older, but no evidence from the crater observations supports an age as great as 1 b.y. If the age of the observed Venusian surface were 1 b.y., it probably should bear the impact scars of a half dozen or more large comet nuclei that penetrated the atmosphere and formed craters well over 100 km in diameter. Venera 15/16 mapped only about 25% of Venus; the remaining 75% may tell us a completely different story.

Schaber, G.G.; Shoemaker, E.M.; Kozak, R.C.

1987-10-01

 
 
 
 
301

Geologic map of the Mead quadrangle (V-21), Venus  

Science.gov (United States)

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the Venusian atmosphere on October 12, 1994. Magellan Mission objectives included (1) improving the knowledge of the geological processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving the knowledge of the geophysics of Venus by analysis of Venusian gravity. The Mead quadrangle (V-21) of Venus is bounded by lat 0 deg and 25 deg N., long 30 deg and 60 deg E. This quadrangle is one of 62 covering Venus at 1:5,000,000 scale. Named for the largest crater on Venus, the quadrangle is dominated by effusive volcanic deposits associated with five major coronae in eastern Eistla Regio (Didilia, Pavlova, Calakomana, Isong, and Ninmah), corona-like tectonic features, and Disani Corona. The southern extremity of Bell Regio, marked by lava flows from Nyx Mons, north of the map area, forms the north-central part of the quadrangle. The shield volcanoes Kali, Dzalarhons, and Ptesanwi Montes lie south and southwest of the large corona-related flow field. Lava flows from sources east of Mead crater flood low-lying areas along the east edge of the quadrangle.

Campbell, Bruce A.; Clark, David A.

2006-01-01

302

Nanoscale organization of {beta}{sub 2}-adrenergic receptor-Venus fusion protein domains on the surface of mammalian cells  

Energy Technology Data Exchange (ETDEWEB)

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 {beta}{sub 2}-adrenergic receptors ({beta}{sub 2}AR) fused to the GFP analogue Venus at the nanoscale on HEK293 cells. The expression of the {beta}{sub 2}AR-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 {beta}{sub 2}AR-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 {beta}{sub 2}AR are observed in the membrane of the HEK293 cells that stably overexpress {beta}{sub 2}AR-GFP and {beta}{sub 2}AR-eYFP. We conclude that precise chemical control of gene expression is highly advantageous for the use {beta}{sub 2}AR-Venus fusion proteins as models for {beta}{sub 2}AR function. These observations are critical for designing future cell models and assays based on {beta}{sub 2}AR, since the receptor biology is consistent with a relatively low density of nanoscale receptor domains.

Vobornik, Dusan; Rouleau, Yanouchka; Haley, Jennifer [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6 (Canada); Bani-Yaghoub, Mahmud [Institute for Biological Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6 (Canada); Taylor, Rod [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6 (Canada); Johnston, Linda J., E-mail: Linda.Johnston@nrc-cnrc.gc.ca [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6 (Canada); Pezacki, John Paul, E-mail: John.Pezacki@nrc-cnrc.gc.ca [Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6 (Canada)

2009-04-24

303

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.

2009-04-24

304

Evidence for retrograde lithospheric subduction on Venus  

Science.gov (United States)

Though there is no plate tectonics per se on Venus, recent Magellan radar images and topographic profiles of the planet suggest the occurrence of the plate tectonic processes of lithospheric subduction and back-arc spreading. The perimeters of several large coronae (e.g., Latona, Artemis, and Eithinoha) resemble Earth subduction zones in both their planform and topographic profile. The planform of arcuate structures in Eastern Aphrodite were compared with subduction zones of the East Indies. The venusian structures have radii of curvature that are similar to those of terrestrial subduction zones. Moreover, the topography of the venusian ridge/trench structures is highly asymmetric with a ridge on the concave side and a trough on the convex side; Earth subduction zones generally display the same asymmetry.

Sandwell, David T.; Schubert, Gerald

1992-12-01

305

Mars, Venus and Gray: Gender Communication  

Directory of Open Access Journals (Sweden)

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

Kamarul Zaman Ahmad

2010-03-01

306

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

Science.gov (United States)

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

2011-04-13

307

Assessing Student Scientific Expression Using Media: The Media-Enhanced Science Presentation Rubric (MESPR)  

Science.gov (United States)

The current study evaluated an assessment designed to dually promote student understanding of the experimental method and student ability to include digital and visual qualities in their presentations of scientific experiment results. The rubric, the Media-Enhanced Science Presentation Rubric (MESPR) focuses teacher-student dialogue along the…

Mott, Michael S.; Chessin, Debby A.; Sumrall, William J.; Rutherford, Angela S.; Moore, Virginia J.

2011-01-01

308

Venus was wet: a measurement of the ratio of deuterium to hydrogen  

International Nuclear Information System (INIS)

The deuterium-hydrogen abundance ratio in the Venus atmosphere was measured while the inlets to the Pioneer Venus large probe mass spectrometer were coated with sulfuric acid from Venus' clouds. The ratio is (1.6 +- 0.2) x 10"-_2. The hundredfold enrichment of deuterium means that at least 0.3% of a terrestrial ocean was outgassed on Venus, but is consistent with a much greater production. 2 figures

1982-05-07

309

Crater production on Venus and Earth by asteroid and comet impact  

International Nuclear Information System (INIS)

New calculations of the collision probabilities of asteroids and comets with Venus were carried out based on the orbits of the known Venus-crossing asteroids and comets. For comparison, asteroid and comet collision probabilities and cratering rates on the Earth and Moon were recalculated and the estimated cratering rates on Venus were normalized to those of the Earth

1987-05-01

310

Critical taper wedge mechanics of fold-and-thrust belts on Venus - Initial results from Magellan  

Science.gov (United States)

Examples of fold-and-thrust belts from a variety of tectonic settings on Venus are introduced. Predictions for the mechanics of fold-and-thrust belts on Venus are examined on the basis of wedge theory, rock mechanics data, and currently known conditions on Venus. The theoretical predictions are then compared with new Magellan data.

Suppe, John; Connors, Chris

1992-01-01

311

Calculation of neutron flux spectrum and average neutron energy for Venus No.1 assembly  

International Nuclear Information System (INIS)

Venus No.1 assembly is a system consisting of both fast and thermal neutron zones for ADS research in China. The neutronics spectrum calculations in Venus No.1 assembly were performed with two-dimensional transport code TWODANT. The result shows that the neutron spectra in Venus No.1 assembly are hard enough for the ADS experiments. (authors)

2006-03-01

312

Remote Laser Induced Breakdown Spectroscopy (LIBS) Geochemical Investigation under Venus Atmospheric Conditions  

Science.gov (United States)

The extreme Venus surface temperature (740 K) and atmospheric pressure (93 atm) creates a challenging environment for future lander missions. Scientific investigations capable of Venus geochemical observations must be completed within several hours of landing before the lander is overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. [1] and Sharma et al. [2] have 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 LIBS and demonstrate the quantitative analysis under Venus surface conditions. The LIBS experiment involves focusing a Nd:YAG laser operating at 1064 nm onto the surface of the sample. The laser ablates material from the surface, generating a plasma containing electronically excited atoms, ions and small molecules. Some of this emission is collected with an 89 mm diameter telescope. The light is directed into a Princeton Instruments f/4 0.25 m dispersive spectrometer and recorded with an ICCD detector. The powdered and pelletized samples are placed in a pressure vessel containing supercritical CO2 at 93 atm and at least 423 K and the vessel is placed at least 1.6 m from the telescope and laser. A range of Venus-analog basaltic rock types [3] was chosen for this study to reproduce compositions identified by Soviet Venera and VEGA landers, including several standards: four basalts (BCR-2, BIR-1, GUWBM, JB-2), granite (GBW 07015), andesite (JA-1), carbonate (SARM-40), and Kauai volcanic (KV04-17, KV04-25). We also added a good Venus analog, TAP 04, which is an alkali-rich rock from an olivine minette in the Ayutla volcanic field (Righter and Rosas-Elguera [4]). Our goal was to study samples with a range of abundances for each element of interest so as to optimize the efficacy of the resultant calibration for predicting a range of compositions. Peaks for all required major, minor, and trace elements were well above the noise floor and readily detected. Peak intensities and areas were then used to quantify elemental chemistry. 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 demonstrates that the major element compositions of rock powders acquired at 93 atm/423 K can be determined with better than 10% accuracy and precision. [1] Wiens R.C., et al. (2005) Spect. Acta A 61, 2324; [2] Sharma, S. K. et al. (2007) Spect. Acta A, 68 , 1036 (2007); [3] Barsukov VL (1992) Venusian Igneous Rocks. In Venus Geology, Geochemistry, and Geophysics (eds. VL Barsukov, AT Basilevsky, VP Volkov, and VW Zharkov). Univ. Arizona Press, pp. 165-176. [4] Righter K. and Rosas-Elguera J. (2001) J. Petrol. 42, 2333.

Clegg, S. M.; Barefield, J. E.; Humphries, S.; Wiens, R. C.; Vaniman, D.; Dyar, M. D.; Tucker, J. M.; Sharma, S. K.; Misra, A. K.

2009-12-01

313

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

Science.gov (United States)

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

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

2009-12-01

314

Pissible Habitats in the Venusian Environment? How Can the Venus Payload Contribute?  

Science.gov (United States)

The Venusian conditions are unique in the solar system. Venus has a dense CO2 atmosphere, is volcanically active, and has plenty of energy sources such as light, UV radiation, volcanic activity, and chemical energy from atmospheric disequilibria conditions. Its surface conditions are sufficiently hot for sterilization and volcanism injects highly toxic gases which in the absence of unbound water can accumulate in the atmosphere. The Venusian surface is constantly regenerated by volcanism and any possible fossil record from early Venus history in which oceans existed on its surface is almost certainly destroyed. Its upper atmosphere lays bare to solar radiation with only carbon dioxide to act as a confirmed EUV filter. Any possibility of life was considered irrational before extremophile bacteria were discovered in dark undersea hot sulphur rich volcanic vents on Earth. However, some regions of the Venusian clouds might show conditions similar to the earth surface and could be a habitat of thermophilic microbial life similar to the one observed on Earth. A synergy between different instruments of the VENUS-Express payload, the SPICAV spectrometer and the VMC camera in a first step, and the spectrometers VIRTIS and PFS in a second step, will probe the actual environmental conditions of the cloud region. The SPICAV spectrometer, in particular, has three channels including, two infrared AOTF channels and could give access to organic signatures in both the UV and infrared. Given these observations we will be able to analyze whether the environmental conditions of the cloud layer would make it a possible habitat for extant microbial life. The instruments will shed answers to the availability of nutrients, water, types of energy sources, atmospheric dynamics, and organic chemistry.

Muller, C. L.; Schulze-Makuch, D.

2005-12-01

315

Visible and near-infrared nightglow of molecular oxygen in the atmosphere of Venus  

Science.gov (United States)

The Herzberg II system of O2 has been a known feature of Venus' nightglow since the Venera 9 and 10 orbiters detected its c(0)-X(v?) progression more than 3 decades ago. We search for its emission at 400 nm-700 nm in spectra obtained with the VIRTIS instrument on Venus Express. Despite the weakness of the signal, integration over a few hours of limb observations of the planet's upper atmosphere reveals the unambiguous pattern of the progression. The selected data sample mainly the northern latitudes within a few hours of local midnight. The emission is ubiquitous on the nightside of Venus and can be discerned at tangent altitudes from 80 km to 110 km. The average emission vertical profiles of the c(0)-X(v?) progression and the O2 a(0)-X(0) band, the latter from simultaneous near-infrared spectra, are quite similar, with their respective peaks occurring within ±1 km of each other. We conclude that the net yield for production of the c(0) state is low, ˜1%-2% of the oxygen recombination rate, and that O(3P) and CO2 are the two likely quenchers of the Herzberg II nightglow, although CO cannot be ruled out. We also derive a value of 2.45 × 10-16 cm3 s-1 for the rate constant at which CO2 collisionally quenches the c(0) state. Our VIRTIS spectra show hints of O2 A?(0)-a(v?) emission but no traces of the O (1 S-1D) green line at 557.7 nm.

García Muñoz, A.; Mills, F. P.; Slanger, T. G.; Piccioni, G.; Drossart, P.

2009-12-01

316

High spatial Resolution mapping of Venus Mesospheric Winds by infrared heterodyne Spectroscopy of CO2  

Science.gov (United States)

We present wind measurements in the Venusian upper mesosphere / lower thermosphere by means of infrared heterodyne spectroscopy of CO2 features at 959.3917 cm-1. Observations are carried out using the Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) from May 25th to June 6th 2007 shortly before Venus superior conjunction at the McMath-Pierce solar telescope on Kitt Peak in Arizona. Providing high spectral resolution winds can be retrieved from Doppler-shifts of CO2 non-thermal emission from the upper mesosphere. The sub-solar to anti-solar flow (SS-AS flow) and the retrograde superrotating zonal circulation (RSZ) are targeted and observations are carried out systematically on the day-side of the planet which is illuminated appr. 50%. The mesospheric region is of special interest because it is the not very well understood transitions zone form the RSZ dominated troposphere and the SS-AS flow dominated thermosphere. Measurements are part of the coordinated ground-based observing campaign to support VenusExpress from May 25th to June 9th. Complementary ground based observing methods probing wind velocities at different altitudes in the atmosphere of Venus provide the possibility to get a vertical wind profile. E.g. Doppler shifts of CO2 lines at visible wavelength together with reflected solar Frauenhofer lines probe dynamics at the cloud tops and a few kilometer above while interferometric CO millimeter observations provide information about the lower mesosphere and sub-millimeter spectral line observations are pointing to a region between 95 and 105km. The presented mid- IR measurements probe an altitude of 100-120km.

Sonnabend, G.; Sornig, M.; Krötz, P.; Stupar, D.; Livengood, T.; Schieder, R.; Kostiuk, T.

2007-08-01

317

Magmatic diversity on Venus: Constraints from terrestrial analog crystallization experiments  

Science.gov (United States)

Igneous diversity is common on terrestrial planets and has been experimentally investigated for the Earth and Mars, but only suggested for Venus. Since Venus and Earth are sister planets and have similar bulk chemistry, experiments on terrestrial basalts can place constraints on the formation of the Venera and Vega basalts. Furthermore, experimental results can suggest the types of magmas that should be present on Venus if processes of differentiation similar to those taking place within the Earth are occurring on Venus, as suggested by the Venera and Vega analyses. The interpretation of the Venera 13 analysis as an alkali basalt suggests deep partial melting of a carbonated source region; while the identification of Venera 14 and Vega 2 as tholeiites suggest relatively shallow melting of a hydrous lherzolitic or peridotite source region. The residual liquids produced by differentiation of a Venus tholeiite, based on experiments on analog compositions, range from rhyolites to phonolites, depending on pressure of crystallization and bulk water content. Results from these crystallization experiments on tholeiitic terrestrial compositions can constrain the type and quality of data needed from future missions to determine the petrologic history of surface igneous rocks.

Filiberto, Justin

2014-03-01

318

Benchmark calculations for VENUS-2 MOX -fueled reactor dosimetry  

International Nuclear Information System (INIS)

As a part of a Nuclear Energy Agency (NEA) Project, it was pursued the benchmark for dosimetry calculation of the VENUS-2 MOX-fueled reactor. In this benchmark, the goal is to test the current state-of-the-art computational methods of calculating neutron flux to reactor components against the measured data of the VENUS-2 MOX-fuelled critical experiments. The measured data to be used for this benchmark are the equivalent fission fluxes which are the reaction rates divided by the U235 fission spectrum averaged cross-section of the corresponding dosimeter. The present benchmark is, therefore, defined to calculate reaction rates and corresponding equivalent fission fluxes measured on the core-mid plane at specific positions outside the core of the VENUS-2 MOX-fuelled reactor. This is a follow-up exercise to the previously completed UO2-fuelled VENUS-1 two-dimensional and VENUS-3 three-dimensional exercises. The use of MOX fuel in LWRs presents different neutron characteristics and this is the main interest of the current benchmark compared to the previous ones

2004-10-28

319

Doppler Lidar for Wind Measurements on Venus  

Science.gov (United States)

NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

2010-01-01

320

Mariner Venus/Mercury 1973 solar radiation force and torques  

International Nuclear Information System (INIS)

The need for an improvement of the mathematical model of the solar radiation force and torques for the Mariner Venus/Mercury spacecraft arises from the fact that this spacecraft will be steering toward the inner planets (Venus and Mercury), where, due to the proximity of the Sun, the effect of the solar radiation pressure is much larger than it was on the antecedent Mariner spacecraft, steering in the opposite direction. Therefore, although the model yielded excellent results in the case of the Mariner 9 Mars Orbiter, additional effects of negligible magnitudes for the previous missions of the Mariner spacecraft should now be included in the model. This study examines all such effects and incorporates them into the already existing model, as well as using the improved model for calculation of the solar radiation force and torques acting on the Mariner Venus/Mercury spacecraft

1974-01-01

 
 
 
 
321

Laboratory simulation of the induced magnetospheres of comets and Venus  

International Nuclear Information System (INIS)

The comparison of data obtained in laboratory experiments on the solar wind interaction with a body endowed with a plasma shell, the observations of comet type I tails and the direct measurements near Venus show that an induced magnetosphere is formed with an extended magnetic tail. This magnetosphere appears due to currents associated with unipolar induction. The distribution of electrodynamical forces associated with the formation of the induced magnetosphere makes it possible to explain the acceleration of matter towards the tail as in the motion across the tail observed in comets and Venus. The analysis of the condensation motion in Halley's comet yields an estimate of tail magnetic field of 30 to 50 ?. A three-dimensional model of the induced magnetospheres of Venus and comets is developed. (Auth.)

1980-01-01

322

HARPS Observations of the 2012 Transit of Venus  

Science.gov (United States)

On 6 June 2012 the black disc of Venus passed across the Solar disc, taking nearly eight hours to complete the transit. The event was followed by millions of people worldwide. The transit of Venus is one of the rarest astronomical events, occurring approximately every 120 years. By means of HARPS spectroscopic observations, and using the Moon as a mirror, we detected the Rossiter-McLaughlin effect due to the eclipse by Venus of the Solar disc with a precision of few cm s-1. The observation demonstrates that this effect can be measured even for transits of exoplanets of Earth size, or even smaller, provided enough photons can be collected by a very high resolution and extremely stable spectrograph, such as the planned HIRES instrument for the E-ELT.

Molaro, P.; Monaco, L.; Barbieri, M.; Zaggia, S.

2013-09-01

323

Steady-state plasma transition in the Venus ionosheath  

International Nuclear Information System (INIS)

The results of an extended analysis of the plasma and electric field data of the Pioneer Venus Orbiter (PVO) are presented. The authors report the persistent presence of a plasma transition embedded in the flanks of the Venus ionosheath between the bow shock and the ionopause. This transition is identified by the repeated presence of characteristic bursts in the 30 kHz channel of the electric field detector of the PVO. The observed electric field signals coincide with the onset of different plasma conditions in the inner ionosheat where more rarified plasma fluxes are measured. The repeated identification of this intermediate ionosheath transition in the PVO data indicates that it is present as a steady state feature of the Venus plasma environment. This distribution of PVO orbits in which the transition is observed suggests that it is more favourably detected in the vicinity of and downstream from the terminator

1991-01-01

324

Solar wind origin of Ar-36 on Venus  

International Nuclear Information System (INIS)

An examination is conducted concerning the circumstances under which the difference between earth and Venus (and Mars) fits naturally into theories in which the terrestrial planets formed by the gradual sweeping up of planetesimals in an essentially gas-free protoplanetary swarm. The primary purpose of the reported investigation is to use observational data to define restrictions on planetary formation theories that would be imposed if most of Venus' inert gases come from the solar wind. The observational data support the suggestion that the abundances of Ar, Kr, and Xe on Venus have been augmented by a component of solar composition. Solar wind implantation at an early stage of accumulation provides a natural way of producing the observed extreme heliocentric distribution of this component, provided that accumulation occurred after dissipation of solar gas from the solar nebula

1981-01-01

325

Water loss from Venus: Implications for the Earth's early atmosphere  

Science.gov (United States)

The atmosphere of Venus outgassed rapidly as a result of planetary heating during accretion, resulting in massive water loss. The processes affecting atmospheric chemistry following accretion have consisted largely of hydrogen escape and internal re-equilibrium. The initial bulk composition of Venus and Earth are assumed to have been roughly similar. Chemical speciation on Venus was controlled by the temperature and oxygen buffering capacity of the surface magma. It is also assumed that the surfaces of planetary bodies of the inner solar system were partly or wholly molten during accretion with a temperature estimated at 1273 to 1573 K. To investigate the range of reasonable initial atmospheric compositions on Venus, limits have to be set for the proportion of total hydrogen and the buffered fugacity of oxygen. Using the C/H ratio of 0.033 set for Earth, virtually all of the water generated during outgassing must later have been lost in order to bring the current CO2/H2O ratio for Venus up to its observed value of 10 sup 4 to 10 sup 5. The proportion of H2O decreases in model atmospheres with successfully higher C/H values, ultimately approaching the depleted values currently observed on Venus. Increasing C/H also results in a rapid increase in CO/H2O and provides an efficient mechanism for water loss by the reaction CO+H2O = CO2 + H2. This reaction, plus water loss mechanisms involving crustal iron, could have removed a very large volume of water from the Venusian atmosphere, even at a low C/H value.

Richardson, S. M.; Pollack, J. B.; Reynolds, R. T.

1985-01-01

326

Propagation of the trip behavior in the VENUS vertex chamber  

International Nuclear Information System (INIS)

The high voltage system of the VENUS vertex chamber occasionally trips by a discharge somewhere among cathode electrodes during data taking. This trip behavior induces often additional trips at other electrodes such as the skin and the grid electrodes in the vertex chamber. This propagation mechanism of trips is so complicated in this system related with multi-electrodes. Although the vertex chamber is already installed inside the VENUS detector and consequently the discharge is not able to observe directly, a trial to estimate the propagation has been done using only the information which appears around the trip circuits and the power supply of the vertex chamber. (author)

1995-01-01

327

Temperature structure and dynamics of the middle atmosphere of Venus  

Science.gov (United States)

Data obtained by the Pioneer Venus Orbiter Infrared Radiometer in late 1978 and early 1979 are presented in tabular form, including, in particular, the mean temperature structure, with complete latitudinal and longitudinal coverage, and zonal-mean cloud properties. The mean thermal and cloud structures can be interpreted in terms of general circulation of the middle atmosphere. The interim results indicate that (1) the zonal winds on Venus fall to very low values above 90 km, (2) there is a strong midlatitude jet which circles the planet approximately every two days, and (3) the observed solar tides are dominated by the semidiurnal component.

Taylor, F. W.; Valdes, P. J.; Schofield, J. T.

1985-01-01

328

Suprathermal ions observed upstream of the Venus bow shock  

Energy Technology Data Exchange (ETDEWEB)

Suprathermal ions with arrival directions quite distinct from those of the solar wind have been detected upstream of the Venus bow shock. We examine the possibility that these events could be caused by instrumental of spacecraft effects of that they could be either solar wind disturbances, planetary pickup ions, or suprathermal ions upstream of the Venus bow shock and conclude that they are consistent with upstream suprathermal ions associated with the bow shock that are observed downstream from the points of intersection of their extrapolated trajectories with the shock. copyright American Geophysical Union 1989

Moore, K.R.; McComas, D.J.; Russell, C.T.; Mihalov, J.D.

1989-04-01

329

The Venus ultraviolet aurora: A soft electron source  

Energy Technology Data Exchange (ETDEWEB)

The Pioneer Venus Orbiter Ultraviolet Spectrometer has recorded continuous but variable emissions of atomic oxygen at 1,304 and 1,356 {angstrom} in images of the nightside of Venus. The authors show that the observed intensities are consistent with the presence of precipitation of soft electrons into the nightside thermosphere. Model calculations are presented in which upper and lower limits to the magnitude of the electron flux necessary to produce the observed intensities are derived. Constraints are imposed on the energy spectrum of the electrons by the measured ion densities and by the predicted intensities of other emissions that have not been detected.

Fox, J.L. (State Univ. of New York, Stony Brook (USA)); Stewart, A.I.F. (Univ. of Colorado, Boulder (USA))

1991-06-01

330

Three-dimensional benchmark model establishment for VENUS-3 reactor  

Energy Technology Data Exchange (ETDEWEB)

The benchmark-models for VENUS-3 reactor are established as a part of International Reactor Physics Experiments Evaluation Project (IRPhEP) managed by OECD/NEA. The benchmark models for VENUS-3 experiment consist of critical configuration benchmark-model, reaction-rate distribution benchmark-model and power distribution benchmark-model. The criticality calculation is performed to obtain the k{sub eff} and 3-dimensional power distributions, and the neutron transport calculation is performed to obtain the reaction rates distribution. The results obtained using these benchmark-models are compared with the experimental data.

Moon, Bok Ja; Choi, Jong Ho; Seo, Jong Tae [Korea Power Engineering Company, Taejon (Korea, Republic of)

2005-07-01

331

The Mexican expedition to observe the 8 December 1874 transit of Venus in Japan  

Science.gov (United States)

The voyage of the Mexican commission to observe the transit of Venus on 8 December 1874 in Japan is briefly recounted. The five-man expedition was led by Francisco Díaz Covarrubias. They succeeded in establishing two observing stations near Yokohama, one in Nogue-no-Yama and one on a hill called "The Bluff", and also in determining precise geographical positions for them. Clear skies allowed the observation of the transit at both stations. The results were presented in Paris in 1875, and published on the same year. They were meant as a contribution to be processed along with all other data obtained by different missions. The importance of the expedition for the development of early modern science in Mexico - particularly astronomy - is examined in the broad context of the social and political conditions then prevailing in the country. The relevance of the mission for the establishment of scientific, cultural and even commercial ties between Japan and Mexico is emphasized.

Allen, Christine

2005-04-01

332

A novel cell-cycle-indicator, mVenus-p27K?, identifies quiescent cells and visualizes G0-G1 transition  

Science.gov (United States)

The quiescent (G0) phase of the cell cycle is the reversible phase from which the cells exit from the cell cycle. Due to the difficulty of defining the G0 phase, quiescent cells have not been well characterized. In this study, a fusion protein consisting of mVenus and a defective mutant of CDK inhibitor, p27 (p27K?) was shown to be able to identify and isolate a population of quiescent cells and to effectively visualize the G0 to G1 transition. By comparing the expression profiles of the G0 and G1 cells defined by mVenus-p27K?, we have identified molecular features of quiescent cells. Quiescence is also an important feature of many types of stem cells, and mVenus-p27K?-transgenic mice enabled the detection of the quiescent cells with muscle stem cell markers in muscle in vivo. The mVenus-p27K? probe could be useful in investigating stem cells as well as quiescent cells.

Oki, Toshihiko; Nishimura, Koutarou; Kitaura, Jiro; Togami, Katsuhiro; Maehara, Akie; Izawa, Kumi; Sakaue-Sawano, Asako; Niida, Atsushi; Miyano, Satoru; Aburatani, Hiroyuki; Kiyonari, Hiroshi; Miyawaki, Atsushi; Kitamura, Toshio

2014-01-01

333

A novel cell-cycle-indicator, mVenus-p27K-, identifies quiescent cells and visualizes G0-G1 transition  

Science.gov (United States)

The quiescent (G0) phase of the cell cycle is the reversible phase from which the cells exit from the cell cycle. Due to the difficulty of defining the G0 phase, quiescent cells have not been well characterized. In this study, a fusion protein consisting of mVenus and a defective mutant of CDK inhibitor, p27 (p27K-) was shown to be able to identify and isolate a population of quiescent cells and to effectively visualize the G0 to G1 transition. By comparing the expression profiles of the G0 and G1 cells defined by mVenus-p27K-, we have identified molecular features of quiescent cells. Quiescence is also an important feature of many types of stem cells, and mVenus-p27K--transgenic mice enabled the detection of the quiescent cells with muscle stem cell markers in muscle in vivo. The mVenus-p27K- probe could be useful in investigating stem cells as well as quiescent cells.

Oki, Toshihiko; Nishimura, Koutarou; Kitaura, Jiro; Togami, Katsuhiro; Maehara, Akie; Izawa, Kumi; Sakaue-Sawano, Asako; Niida, Atsushi; Miyano, Satoru; Aburatani, Hiroyuki; Kiyonari, Hiroshi; Miyawaki, Atsushi; Kitamura, Toshio

2014-02-01

334

Waves in Venus's middle and upper atmosphere: Implications of Pioneer Venus probe data above the clouds  

Energy Technology Data Exchange (ETDEWEB)

Probe data showing the presence of waves in Venus's middle and upper atmosphere are critically reevaluated and extended to 138 km, near the level of in-situ data taken by the Pioneer Venus orbiter. Uncertainties in temperature are determined. They are typically about 0.1 times amplitude, thus supporting the reality of large amplitude oscillations approaching 40 K at 120 km. Growth rates above 100 km follow approximately the inverse square root of density until saturation occurs (in the sense that lapse rates become adiabatic in the expanding segment of the wave). The waves then break at the 120 km level, providing a source for the friction required in models to match the observed day-night temperature contrast in Venus's lower thermosphere. The data correlate to an unexpected degree with temperatures from the Pioneer Venus orbiter atmospheric drag (OAD) experiment taken at altitudes of 140 to 165 km, which, especially for the night probe, extend not only the mean temperature structure, but also the oscillation structure of the probe data at the same local Venus time. OAD temperatures depend on local Venus time and altitude, but, in the limited number of observations, appear independent of observing date over periods of up to 11 days, and correlate as described with probe data taken 65 to 137 days earlier. These observations lead to the suggestion that the thermospheric waves are solar-fixed, induced either by the major subsidence across the terminators or as continuations upward of waves in the middle atmosphere. The wave structure in the large probe sounding below 100 km is similar to, but does not quantitatively support the solar-tidal model of Pechmann and Ingersoll, which gives much larger amplitudes and different wave phases.

Seiff, A. (San Jose State Univ. Foundation, Moffett Field, CA (USA)); Kirk, D.B. (Univ. of Oregon, Eugene (USA))

1991-07-01

335

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

Science.gov (United States)

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

Echim, Marius M.

2014-05-01

336

Resurfacing Controversy for Venus: An Overview and a Mechanistic Perspective.  

Science.gov (United States)

Two remarkable aspects of the population of impact craters on Venus are that craters at all sizes are indistinguishable from a random population and that most craters have not been significantly modified by tectonic strain or by volcanic flows external to...

S. C. Solomon

1993-01-01

337

Water loss on Venus - The role of carbon monoxide  

Science.gov (United States)

The four-to-fivefold difference in water abundance between the earth and Venus may reflect either initial differences in the bulk volatile content of the two planets, or massive water loss mechanisms on Venus. These two possibilities were investigated by performing thermodynamic calculations on the heterogeneous system C-O-H-N-S, varying C/H upward from its 0.033 terrestrial value. While atmospheric H2O decreases as bulk C/H increases, the latter would have to rise to an improbably high value in order to account for the low water abundance on Venus through initial deficiency alone. Calculations suggest that if the outgassed C/H on Venus was higher than on earth by even a factor of 5, it would have been sufficient for CO to become competitive with FeO as a sink for oxygen. Together with the lower initial water abundance value that follows from a higher C/H ratio, water loss due to CO may have been a major factor.

Richardson, S. M.; Pollack, J. B.; Reynolds, R. T.

1984-01-01

338

Occultation of the Bright Star Regulus by Venus.  

Science.gov (United States)

This occultation was observed and timed visually early in the afternoon of 7 July, in Madrid, Spain. The duration of the occultation was 11 minutes, 4.4 seconds, and mid-occultation occurred at 14 hours, 25 minutes, 9 seconds U.T. Over 600 individual photographs, which define the relative positions of Venus and Regulus, were obtained. PMID:17816323

Hynek, J A

1959-09-18

339

Venus Guided Aerosonde (VGA) for Landing Site Reconnaissance  

Science.gov (United States)

The VGA concept extends previous Venus dropsonde concepts by adding a precise terrain-relative navigation capability, followed by a low-altitude, shallow glide to obtain high-resolution images and 3-D mapping data to scout potential landing sights.

Matthies, L.; Cutts, J.; Tokumaru, P.; Pauken, M.

2014-06-01

340

Surface age of Venus: applying the terrestrial cratering rate  

International Nuclear Information System (INIS)

The population of Venusian craters having suspected impact crater morphology has been reported from 115 x 10 to the 6th power sq km of the northern hemisphere of the planet with the estimated average age of the surface to be approx. 1 b.y. (+ or - 0.5 b.y.) on the basis of lunar crater production curves corrected for Venus. Such an old average age is somewhat difficult to reconcile with the similarity in size and mass of Venus and Earth and with Earth's high heat flow and crustal resurfacing rate. Given the present uncertainties in the role of both active and inactive comet nuclei in the cratering history of Earth, it is concluded that the average age of the observed surface in the northern hemisphere of Venus could be as great as the 450 m.y. mean age of the Earth's crust. The surface of Venus might be even older, but no evidence from the crater observations support an age as great as 1 b.y

1987-05-01

 
 
 
 
341

The 1761 discovery of Venus' atmosphere: Lomonosov and others  

Science.gov (United States)

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

Shiltsev, Vladimir

2014-03-01

342

Cleopatra Crater, a Circular Portal to the Soul of Venus  

Science.gov (United States)

Cleopatra is on the flanks of Maxwell Montes, the tallest mountain range on Venus. Inside the peak ring is a 60-km wide, flat area that represents a relatively safe area to obtain a sample of tessera, plus the geology of the area is important.

Herrick, R. R.

2014-05-01

343

The GUINEVERE project at the VENUS-F Facility  

Energy Technology Data Exchange (ETDEWEB)

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

Baeten, P.; Ait Abderrahim, H.; Bergmans, G.; Kochetkov, A.; Uyttenhove, W.; Vandeplassche, D.; Vermeersch, F.; Vittiglio, G. [SCK-CEN, Boeretang 200, B-2400 Mol (Belgium); Ban, G.; Baylac, M.; Billebaud, A.; Bondoux, D.; Bouvier, J.; Chabod, S.; De Conto, J.M.; Dessagne, P.; Gaudiot, G.; Gautier, J.M.; Heitz, G.; Kerveno, M.; Laune, B.; Lecolley, F.R.; Lecouey, J.L.; Marie, N.; Merrer, Y.; Nuttin, A.; Reynet, D.; Steckmeyer, J.C. [CNRS-IN2P3 (France); Mellier, F. [CEA/DEN/SPeX/LPE, CEN Cadarache, F-13104 Saint-Paul-lez-Durance (France)

2010-07-01

344

Benchmark Calculation on the VENUS-7 MOX Fuel Experiments  

International Nuclear Information System (INIS)

In the late 1960's and the early 1970's, SCK·CEN (Mol, Belgium) carried out a series of experiments entitled 'Plutonium Recycling Physics Project' using the VENUS (Vulcain Experimental Nuclear Study) facility. More than 100 different core configurations have been studied. Recognizing a further need for validation of computing methods and nuclear data for MOX-fuelled systems, SCK·CEN has released all sets of these experimental results to the OECD/NEA for the international community. After having examined, the OECD/NEA expert groups have selected three most interesting configurations for international benchmark exercises. A series of the benchmarks based on these configurations and their experimental results will be organized by the OECD/NEA. One of these experimental data is the configuration VENUS-7 for different types of MOX fuel with different Pu contents. As a part of this benchmark program, 3-dimensional benchmark models have been established based on the problem specification for the configuration VENUS-7 by the Mote Carlo code MCNP4C and the calculation results have been compared with some available VENUS-7 experimental data

2006-11-02

345

Expendable Cooling for a One-Day Venus Lander  

Science.gov (United States)

A thermal architecture of a Venus lander mission using an expendable coolant system has been developed to enable a day-long surface mission. The system uses an aqua-ammonia mixture to provide cooling of the electronics and the pressure vessel.

Pauken, M. T.; Fernandez, C. J.; Jeter, S. M.

2014-06-01

346

A heat pipe mechanism for volcanism and tectonics on Venus  

International Nuclear Information System (INIS)

A heat pipe mechanism is proposed for the transport of heat through the lithosphere on Venus. This mechanism allows the crust and lithosphere on Venus to be greater than 150 km thick. A thick crust and thick lithosphere can explain the high observed topography and large associated gravity anomalies. For a 150-km-thick lithosphere the required volcanic flux on Venus is 200 km3/yr; this is compared with a flux of 17 km3/yr associated with the formation of the oceanic crust on Earth. A thick basaltic crust on Venus is expected to transform to eclogite at a depth of 60 to 80 km; the dense eclogite would contribute the lithospheric delamination that returns the crust to the interior of the planet completing the heat pipe cycle. Topography and the associated gravity anomalies can be explained by Airy compensation of the thick crust. The principal observation that is contrary to this hypothesis is the mean age of the surface that is inferred from crater statistics; the minimum mean age is about 130 Ma, and this implies an upper limit of 2 km3/yr for the surface volcanic flux. If the heat pipe mechanism was applicable on Earth in the Archean, it would provide the thick lithosphere implied by isotopic data from diamonds

1989-01-01

347

The GUINEVERE project at the VENUS-F Facility  

International Nuclear Information System (INIS)

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

2010-06-02

348

Inverse insolation dependence of Venus' cloud-level convection  

Science.gov (United States)

It is generally accepted that convection in planetary atmospheres is enhanced in low latitudes and in the daytime where incoming solar radiation is intense. Here we demonstrate, using a local convection model, that this tendency is reversed for Venus' cloud-level convection, which is driven by heating of the cloud base by upwelling infrared radiation. The dense lower atmosphere of Venus serves as a heat reservoir, whose temperature is horizontally well homogenized by large-scale dynamics, and thus upwelling infrared flux heats the cloud base almost equally over the entire planet. Since solar radiation preferentially heats the upper part of the cloud and has a stabilizing influence on the atmosphere, convection is relatively suppressed in low latitudes and in the daytime. The inverse insolation dependence seen in the numerical model explains observations of the latitudinal dependence of the convective layer depth and the gravity wave activity. The mechanism suggested in this study should be taken into account in climate modeling of Venus and cloudy exoplanets. How the combination of the opposite effects of the infrared heating and the solar heating determines the global distribution of the convective activity is an issue of universal importance. A long-lifetime Venus balloon floating at cloud heights would be useful for understanding these dynamical processes and the associated material transport.

Imamura, Takeshi; Higuchi, Takehito; Maejima, Yasumitsu; Takagi, Masahiro; Sugimoto, Norihiko; Ikeda, Kohei; Ando, Hiroki

2014-01-01

349

Geologic Map of the Helen Planitia Quadrangle (V-52), Venus  

Science.gov (United States)

The Magellan spacecraft orbited Venus from August 10, 1990, until it plunged into the Venusian atmosphere on October 12, 1994. Magellan Mission objectives included (1) improving the knowledge of the geological processes, surface properties, and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving the knowledge of the geophysics of Venus by analysis of Venusian gravity. The Helen Planitia quadrangle (V-52), located in the southern hemisphere of Venus between lat 25 deg S. and 50 deg S. and between long 240 deg E. and 270 deg E., covers approximately 8,000,000 km2. Regionally, the map area is located at the southern limit of an area of enhanced tectonomagmatic activity and extensional deformation, marked by a triangle that has highland apexes at Beta, Atla, and Themis Regiones (BAT anomaly) and is connected by the large extensional belts of Devana, Hecate, and Parga Chasmata. The BAT anomaly covers approximately 20 percent of the Venusian surface.

Lopez, Ivan; Hansen, Vicki L.

2008-01-01

350

The 'Venus' of Laussel in the Light of Ethnomusicology  

Digital Repository Infrastructure Vision for European Research (DRIVER)

De Venus of "Dame ? la corne" van Laussel werd in 1911 gevonden door G. Lalanne in de "Grand Abri de Laussel" (Dordogne, Fr.). Dit bas-relief wordt aanzien als een van de belangrijke voorbeelden van jong-paleolithische kunst uit het Perigordiaan.

Huyge, D.

1991-01-01

351

Modulation of Venus ion densities associated with solar variations  

International Nuclear Information System (INIS)

The dayside ion concentrations in the Venus ionosphere obtained by the Pioneer Venus orbiter ion mass spectrometer exhibit a modulation corresponding to the 27-day solar variation. Comparisons were made of the amplitudes of modulation of CO_2"+, C"+, and O_2"+, with the amplitudes of the 27-day variation in the 10.7 cm solar radio flux and the simultaneously measured EUV fluxes at He II (304 A) and Lyman ? (1026 A), together with a theoretical analysis of the effects of solar variability on the ionosphere and neutral atmosphere of Venus. This analysis leads us to the conclusion that the observed modulation of dayside ion densities is primarily due to the variability in the ionizing EUV radiations and, to a much lesser extent, the result of the variability with solar activity of the neutral atmosphere via the variability in exospheric temperature. In this connection, we also show, theoretically, why the percentage variation of exospheric temperature on Venus (as observed in the ONMS data) for a given variation in F/sub 10.7/, is only half of the exospheric temperature variation for Earth

1981-01-01

352

Electrotonic and action potentials in the Venus flytrap.  

Science.gov (United States)

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

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

2013-06-15

353

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

Science.gov (United States)

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

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

2012-04-01

354

Heliospheric current sheet inclinations at Venus and Earth  

Directory of Open Access Journals (Sweden)

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

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

G. Ma

355

Ocean and Seafloor Dynamics From the Ocean Networks Canada VENUS and NEPTUNE Observatories  

Science.gov (United States)

Cabled observatories allow the acquisition of long-term high-resolution time series that enable the detection of short-lived or rare events, allow the interaction with experiments in reaction to such events, as well as generate well-established base-line parameters over a long period of time. Ocean Networks Canada (ONC) has been operating the coastal observatory VENUS with continuous data streaming since 2006 and the regional ocean observatory NEPTUNE Canada since 2009. We present data from the major sites and show how dynamic the system can be. For example, the two gas hydrate nodes at Barkley Canyon and Clayoquot Slope show changes over various time ranges that are important to include in the analysis of gas hydrate dynamics and stability, including environmental changes and microbial activity. Standard conductivity, temperature and bottom pressure data are correlated with sonar and video data to show the inter- and intra-disciplinary aspects of ocean sciences and the need for continuous ocean presence. With a planned operating life span of 25 years Ocean Networks Canada aims to offer the ocean community a unique but necessary high quality data set and hopes to establish a new standard for ocean based sciences, together with new emerging ocean observatories enabling sciences in a way that has not been possible before.

Scherwath, M.; Heesemann, M.; Dewey, R. K.; Hoeberechts, M.; Mihaly, S. F.

2013-12-01

356

Venus small volcano classification and description  

Science.gov (United States)

The high resolution and global coverage of the Magellan radar image data set allows detailed study of the smallest volcanoes on the planet. A modified classification scheme for volcanoes less than 20 km in diameter is shown and described. It is based on observations of all members of the 556 significant clusters or fields of small volcanoes located and described by this author during data collection for the Magellan Volcanic and Magmatic Feature Catalog. This global study of approximately 10 exp 4 volcanoes provides new information for refining small volcano classification based on individual characteristics. Total number of these volcanoes was estimated to be 10 exp 5 to 10 exp 6 planetwide based on pre-Magellan analysis of Venera 15/16, and during preparation of the global catalog, small volcanoes were identified individually or in clusters in every C1-MIDR mosaic of the Magellan data set. Basal diameter (based on 1000 measured edifices) generally ranges from 2 to 12 km with a mode of 34 km, and follows an exponential distribution similar to the size frequency distribution of seamounts as measured from GLORIA sonar images. This is a typical distribution for most size-limited natural phenomena unlike impact craters which follow a power law distribution and continue to infinitely increase in number with decreasing size. Using an exponential distribution calculated from measured small volcanoes selected globally at random, we can calculate total number possible given a minimum size. The paucity of edifice diameters less than 2 km may be due to inability to identify very small volcanic edifices in this data set; however, summit pits are recognizable at smaller diameters, and 2 km may represent a significant minimum diameter related to style of volcanic eruption. Guest, et al, discussed four general types of small volcanic edifices on Venus: (1) small lava shields; (2) small volcanic cones; (3) small volcanic domes; and (4) scalloped margin domes ('ticks'). Steep-sided domes or 'pancake domes', larger than 20 km in diameter, were included with the small volcanic domes. For the purposes of this study, only volcanic edifices less than 20 km in diameter are discussed. This forms a convenient cutoff since most of the steep-sided domes ('pancake domes') and scalloped margin domes ('ticks') are 20 to 100 km in diameter, are much less numerous globally than are the smaller diameter volcanic edifices (2 to 3 orders of magnitude lower in total global number), and do not commonly occur in large clusters or fields of large numbers of edifices.

Aubele, J. C.

1993-03-01

357

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

Science.gov (United States)

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

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

2012-01-01

358

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-03-01

359

Dynamics of the Venus ionosphere. Final technical report, 1 January 1985-31 May 1988  

Energy Technology Data Exchange (ETDEWEB)

Data from the Pioneer-Venus orbiter has demonstrated the importance of understanding ion dynamics in the Venus ionosphere. The analysis of the data has shown that during solar maximum the topside Venus ionosphere in the dark hemisphere is generated almost entirely on the dayside of the planet during solar maximum, and flows with supersonic velocities across the terminator into the nightside. The flow field in the ionosphere is mainly axially-symmetric about the sun-Venus axis, as are most measured ionospheric quantities. The primary data base used consisted of the ion velocity measurements made by the RPA during three years that periapsis of the orbiter was maintained in the Venus ionosphere. Examples of ion velocities were published and modeled. This research examined the planetary flow patterns measured in the Venus ionosphere, and the physical implications of departures from the mean flow.

Miller, K.L.

1988-01-01

360

Proceedings of the 40th Lunar and Planetary Science Conference  

Science.gov (United States)

The 40th Lunar and Planetary Science Conference included sessions on: Phoenix: Exploration of the Martian Arctic; Origin and Early Evolution of the Moon; Comet Wild 2: Mineralogy and More; Astrobiology: Meteorites, Microbes, Hydrous Habitats, and Irradiated Ices; Phoenix: Soil, Chemistry, and Habitability; Planetary Differentiation; Presolar Grains: Structures and Origins; SPECIAL SESSION: Venus Atmosphere: Venus Express and Future Missions; Mars Polar Caps: Past and Present; SPECIAL SESSION: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1, Part I; 5 Early Nebula Processes and Models; SPECIAL SESSION: Icy Satellites of Jupiter and Saturn: Cosmic Gymnasts; Mars: Ground Ice and Climate Change; SPECIAL SESSION: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1, Part II; Chondrite Parent-Body Processes; SPECIAL SESSION: Icy Satellites of Jupiter and Saturn: Salubrious Surfaces; SNC Meteorites; Ancient Martian Crust: Primary Mineralogy and Aqueous Alteration; SPECIAL SESSION: Messenger at Mercury: A Global Perspective on the Innermost Planet; CAIs and Chondrules: Records of Early Solar System Processes; Small Bodies: Shapes of Things to Come; Sulfur on Mars: Rocks, Soils, and Cycling Processes; Mercury: Evolution and Tectonics; Venus Geology, Volcanism, Tectonics, and Resurfacing; Asteroid-Meteorite Connections; Impacts I: Models and Experiments; Solar Wind and Genesis: Measurements and Interpretation; Mars: Aqueous Processes; Magmatic Volatiles and Eruptive Conditions of Lunar Basalts; Comparative Planetology; Interstellar Matter: Origins and Relationships; Impacts II: Craters and Ejecta Mars: Tectonics and Dynamics; Mars Analogs I: Geological; Exploring the Diversity of Lunar Lithologies with Sample Analyses and Remote Sensing; Chondrite Accretion and Early History; Science Instruments for the Mars Science Lander; . Martian Gullies: Morphology and Origins; Mars: Dunes, Dust, and Wind; Mars: Volcanism; Early Solar System Chronology; Seek Out and Explore: Upcoming and Future Missions; Mars: Early History and Impact Processes; Mars Analogs II: Chemical and Spectral; Achondrites and their Parent Bodies; and Planning for Future Exploration of the Moon The poster sessions were: Lunar Missions: Results from Kaguya, Chang'e-1, and Chandrayaan-1; LRO and LCROSS; Geophysical Analysis of the Lunar Surface and Interior; Remote Observation and Geologic Mapping of the Lunar Surface; Lunar Spectroscopy; Venus Geology, Geophysics, Mapping, and Sampling; Planetary Differentiation; Bunburra and Buzzard Coulee: Recent Meteorite Falls; Meteorites: Terrestrial History; CAIs and Chondrules: Records of Early Solar System Processes; Volatile and Organic Compounds in Chondrites; Crashing Chondrites: Impact, Shock, and Melting; Ureilite Studies; Petrology and Mineralogy of the SNC Meteorites; Martian Meteorites; Phoenix Landing Site: Perchlorate and Other Tasty Treats; Mars Polar Atmospheres and Climate Modeling; Mars Polar Investigations; Mars Near-Surface Ice; Mars: A Volatile-Rich Planet; Mars: Geochemistry and Alteration Processes; Martian Phyllosilicates: Identification, Formation, and Alteration; Astrobiology; Instrument Concepts, Systems, and Probes for Investigating Rocks and Regolith; Seeing is Believing: UV, VIS, IR, X- and Gamma-Ray Camera and Spectrometer Instruments; Up Close and Personal: In Situ Analysis with Laser-Induced Breakdown Spectroscopy and Mass Spectrometry; Jupiter and Inscrutable Io; Tantalizing Titan; Enigmatic Enceladus and Intriguing Iapetus; Icy Satellites: Cryptic Craters; Icy Satellites: Gelid Geology/Geophysics; Icy Satellites: Cool Chemistry and Spectacular Spectroscopy; Asteroids and Comets; Comet Wild 2: Mineralogy and More; Hypervelocity Impacts: Stardust Models, LDEF, and ISPE; Presolar Grains; Early Nebular Processes: Models and Isotopes; Solar Wind and Genesis: Measurements and Interpretation; Education and Public Outreach; Mercury; Pursuing Lunar Exploration; Sources and Eruptionf Lunar Basalts; Chemical and Physical Properties of the Lunar Regolith; Lunar Dust and Transient

2009-01-01

 
 
 
 
361

Investigating Climate on Venus with Future Missions (Invited)  

Science.gov (United States)

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

Grinspoon, D. H.

2013-12-01

362

Venus-Earth-Mars: Comparative Climatology and the Search for Life in the Solar System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Both Venus and Mars have captured the human imagination during the twentieth century as possible abodes of life. Venus had long enchanted humans—all the more so after astronomers realized it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view. It was also the closest planet to Earth, with nearly the same size and surface gravity. These attributes brought myriad speculations about the nature of Venus, its climate, and the possibility of life existing there i...

2012-01-01

363

Charge-exchange in the magnetosheaths of Venus and Mars: a comparison  

International Nuclear Information System (INIS)

The amount of solar wind absorption due to charge-exchange in the Martian magnetosheath is evaluated and found to be about an order of magnitude less than that in the Venus magnetosheath. This difference might explain the observed difference in the scaled position and shape between the shocks at Venus and Mars. The lower solar wind absorption for Mars is attributable to the less dense hot oxygen corona of Mars compared to Venus

1983-01-01

364

Charge-exchange in the magnetosheaths of Venus and Mars: a comparison  

Energy Technology Data Exchange (ETDEWEB)

The amount of solar wind absorption due to charge-exchange in the Martian magnetosheath is evaluated and found to be about an order of magnitude less than that in the Venus magnetosheath. This difference might explain the observed difference in the scaled position and shape between the shocks at Venus and Mars. The lower solar wind absorption for Mars is attributable to the less dense hot oxygen corona of Mars compared to Venus.

Russell, C.; Gombosi, T.I.; Horanyi, M.; Cravens, T.E.; Nagy, A.F.

1983-02-01

365

Orientation of planetary O"+ fluxes and magnetic field lines in the Venus wake  

International Nuclear Information System (INIS)

The conditions in which planetary ions are picked up by the solar wind are examined using the plasma and magnetic field observations made with the Pioneer Venus Orbiter at Venus. It is shown that in the outer regions of the venusian far wake the displacement of planetary O"+ particles, characteristic of the Venus upper ionosphere, does not occur necessarily along the magnetic field lines but approximately in the direction of the shocked solar wind. (U.K.)

1982-09-23

366

Orientation of planetary O/sup +/ fluxes and magnetic field lines in the Venus wake  

Energy Technology Data Exchange (ETDEWEB)

The conditions in which planetary ions are picked up by the solar wind are examined using the plasma and magnetic field observations made with the Pioneer Venus Orbiter at Venus. It is shown that in the outer regions of the venusian far wake the displacement of planetary O/sup +/ particles, characteristic of the Venus upper ionosphere, does not occur necessarily along the magnetic field lines but approximately in the direction of the shocked solar wind.

Perez-de-Tejada, H. (Universidad Nacional Autonoma de Mexico. Inst. de Geofysica); Intriligator, D.S. (Carmel Research Center, Santa Monica, CA (USA)); Russell, C.T. (California Univ., Los Angeles (USA). Inst. of Geophysics and Planetary Physics)

1982-09-23

367

The 1986 eastern (evening) apparition of the planet Venus - Visual and photographic observations  

Energy Technology Data Exchange (ETDEWEB)

This report summarizes visual and photographic observations of the planet Venus for the 1986 eastern (evening) apparition, based on an extensive analysis of data submitted by ALPO Venus Section observers in the U.S. and three other countries. Sources of data and the instruments used in acquiring information about Venus are emphasized, with a statistical analysis of the categories of features seen or suspected in the atmosphere of Venus at visual wavelengths, both in integrated light and with color filters. A similar treatment is given to the cusps, cusp-caps, and cusp-bands, together with a discussion of dark-hemisphere phenomena, including the ashen light. 5 refs.

Benton, J.L. Jr. (Association of Lunar and Planetary Observers, San Francisco, CA (USA))

1990-07-01

368

On the long-wave tangential stresses in the Venus lithosphere and mantle  

International Nuclear Information System (INIS)

Loading coefficients for anomalous density waves situated on different levels in realistic Venus models taking into consideration astenosphere are calculated. Simultaneous analysis of topographic and non-equilibrium gravity fields permit to calculate the long-wave principal tangential stresses in lithosphere and mantle for zonal harmonics with n=2-8. Stresses in Venus lithosphere are found to be about 30 bar, in the deep mantle they may reach 45 bar, but in the weak upper mantle they appear to be small - about few bar. Small tangential stresses in the crust and mantle of Venus indicate that planetary interior is very hot. The conclusion of Venus aseismisity is confirmed

1986-01-01

369

The evaluation of preliminary extrapolation experimental results of the chinese ADS subcritical experimental assembly venus-1  

International Nuclear Information System (INIS)

The design objectives and structure of' the Chinese accelerator-driven subcritical system (ADS) subcritical assembly VENUS-1 are presented. The experiment of source multiplication method is used to determine the final loading of the Chinese ADS VENUS-i subcritical assembly. The Keff of the assembly with the same loading as extrapolation experiment have been calculated. The results of calculation and experiment are evaluated. The final loading of the Chinese ADS VENUS-1 subcritical assembly has been determined by preliminary experiments on VENUS-1. (authors)

2008-01-01

370

Magellan - Early results from the Venus mapping mission  

International Nuclear Information System (INIS)

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

1991-01-07

371

Hot-spot evolution and the global tectonics of Venus  

Science.gov (United States)

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

Phillips, Roger J.; Grimm, Robert E.; Malin, Michael C.

1991-01-01

372

Lucrecio: textos breves sobre Venus, el amor y la muerte  

Directory of Open Access Journals (Sweden)

Full Text Available Se presentan tres textos originales del poeta-filósofo Lucrecio, con sus correspondientes traducciones al castellano y comentarios. Los textos seleccionados del "De rerum natura" son representativos de los principales tópicos del autor. El primero es la invocación a Venus con que comienza la obra. El segundo versa sobre la pasión del amor. El último texto aborda el tema epicúreo del temor a la muerte. (In this article three original texts by poet-philosopher Lucrecius are presented, with their corresponding Spanish translations and commentaries. The texts, taken from "De rerum natura", are representative of the author’s main themes. The first is an invocation to Venus, the second is about the passion of love, and the last one deals with the epicurean topic of the fear of death.

Eduardo Molina Cantó

1998-09-01

373

Long-Duration Altitude-Controlled Balloons for Venus: A Feasibility Study Informed by Balloon Flights in Remote Environments on Earth  

Science.gov (United States)

In situ exploration of the upper atmosphere of Venus, approximately 65-77 km altitude, could answer many important questions (Limaye 2013, Crisp 2013). This region contains a time-variable UV absorber of unknown composition that controls many aspects of the heat balance on Venus. Understanding the composition and dynamics of this unknown absorber is an important science goal; in situ optical and chemical measurements are needed. However, conventional approaches do not provide access to this altitude range, repeated traverses, and a mission lifetime of several months needed to effectively carry out the science. This paper examines concepts for altitude-controlled balloons not previously flown on planetary missions that could potentially provide the desired measurements. The concepts take advantage of the fact that at 60 km altitude, for example, the atmospheric density on Venus is about 40% of the sea-level density on earth and the temperature is a moderate 230 K. The solar flux is approximately double that on earth, creating some thermal challenges, but making photovoltaic power highly effective. Using a steady-state thermodynamic model and flight data from Earth, we evaluate the suitability of two types of altitude-controlled balloons for a potential mission on Venus. Such balloons could repeatedly measure profiles, avoid diurnal temperature extremes, and navigate using wind shear. The first balloon design uses air ballast (AB) whereby ambient air can be compressed into or released from a constant-volume balloon, causing it to descend or ascend accordingly. The second design uses lift-gas compression (LGC) to change the volume of a zero-pressure balloon, thereby changing its effective density and altitude. For an altitude range of 60-75 km on Venus, we find that the superpressure volume for a LGC balloon is about 5% of that needed for an AB balloon while the maximum pressurization is the same for both systems. The compressor work per km descent of the LGC balloon is about 10% of the AB balloon, largely due to the much lower flow rate. The LGC balloon must compress some lift gas at sunrise, but this can be managed by one of several strategies. We conclude that while the weight constraints are likely to be significant, LGC altitude-controlled balloons may be feasible for accessing the 60 to 75 km altitude range on Venus. The underlying concept of balloons on Venus was proven by the Soviet Union's successful deployment of their two superpressure VEGA balloons in 1981 operating at a fixed altitude near 55 km. Superpressure balloon concepts for similar altitudes and larger payloads have since been proposed for NASA's Discovery program and ESA's Cosmic Visions program. The LGC balloon would add a zero-pressure envelope and a compressor to the established superpressure design, allowing it to ascend above the deployment altitude and realize lossless altitude control over a range of several scale heights. The thermodynamic equations, flight data, and conceptual analysis presented are intended to foster further discussion about the feasibility and potential benefits of a balloon mission to Venus.

Voss, P. B.; Nott, J.; Cutts, J. A.; Hall, J. L.; Beauchamp, P. M.; Limaye, S. S.; Baines, K. H.; Hole, L. R.

2013-12-01

374

Microphysical processes in a cloud layer of the Venus  

International Nuclear Information System (INIS)

On the basis of the known experimental data the main microphysical properties of aerosol in a cloud layer of the Venus (the range of particle sizes, numerical density of aerosol, etc.) are singled out. Evolution of distribution function of particles over sizes at initial stages of sulfuric acid cloud formation is considered. The role of various microphysical processes (nucleation, condensation, coagulation, sedimentation, turbulent mixing) in the formation of observed spectra of particle sizes is analyzed

1987-01-01

375

Submillimeter mapping of mesospheric minor species on Venus with ALMA  

Science.gov (United States)

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

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

2014-05-01

376

Possible Signs of Life on the Planet Venus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is possible, the question on the existence of extraterrestrial life will be answered not as a result of its search for in other worlds removed by distances of dozens of parsecs but on the surface of Venus, i.e., of the nearest planet of the Solar system. The search for “habitable zones” in extrasolar planetary systems is based on the postulate on “normal” physical conditions, i.e., the pressure, temperature, and maybe atmospher...

Ksanfomality, Leonid V.

2013-01-01

377

CO2-Reduction Primary Cell for Use on Venus  

Science.gov (United States)

A document proposes a CO2-reduction primary electrochemical cell as a building block of batteries to supply electric power on the surface of Venus. The basic principle of the proposed cell is similar to that of terrestrial Zn-air batteries, the major differences being that (1) the anode metal would not be Zn and (2) CO2, which is about 96.5 mole percent of the Venusian atmosphere, would be used, instead of O2, as the source of oxygen.

West, William; Whitacre, Jay; Narayanan, Sekhanipuram

2007-01-01

378

Geologic Map of the Mylitta Fluctus Quadrangle (V-61), Venus  

Science.gov (United States)

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

Ivanov, Mikhail A.; Head, James W., III

2006-01-01

379

Magnetization of the ionospheres of Venus and Mars: Results from radio occultation measurements  

Energy Technology Data Exchange (ETDEWEB)

In situ measurements by the Pioneer Venus orbiting spacecraft, conducted during solar maximum only, have shown that magnetization (permeation of large-scale magnetic fields) of the ionosphere of Venus occurs under high solar wind dynamic pressure and that this takes place most frequently near the subsolar region. In this paper, the authors use remote sensing radio occultation measurements to study magnetization of the ionospheres of Venus and Mars based on these characteristics. For Venus they take advantage of the unique data set consisting of 148 electron density profiles deduced from Pioneer Venus radio occultation measurements. They demonstrate that radio occultation measurements yield results on frequency of occurrence of magnetization during solar maximum that are similar to those obtained from the Pioneer Venus in situ magnetic field measurements. During solar minimum, for which direct ionospheric measurements have never been made, they find that magnetization of the Venus ionosphere is more pervasive than at solar maximum. Magnetization extends to higher solar zenith angles (SZA) and appears stronger than at solar maximum. These results confirm that during solar minimum, the high solar wind dynamic pressure state is more prevalent at Venus because the ionospheric plasma pressure is weaker than at solar maximum. Comparison of a large number of electron density profiles of Mars (deduced from radio occultation measurements by the Viking 1 and 2 and Mariner 9 spacecraft for SZA > 46{degrees}) with those of Venus shows an absence of the ledge and disturbed topside plasma observed in the Venus profiles. These results, however, do not constitute evidence against magnetization of the ionosphere of Mars, as Shinagawa and Cravens (1989) have shown on their one-dimensional MHD models that, even when the ionosphere of Mars is highly magnetized, the magnetic structure differs from that at Venus, and a ledge does not form in its electron density profiles.

Woo, R.; Kliore, A.J. (California Inst. of Tech., Pasadena (USA))

1991-07-01

380

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

Science.gov (United States)

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