DOCSLIB.ORG

Workshop on Venus Exploration Targets

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Workshop on Venus Exploration Targets Program and Abstract Volume LPI Contribution No. 1781 Workshop on Venus Exploration Targets May 19–21, 2014 • Houston, Texas Institutional Support Universities Space Research Association (USRA) Lunar and Planetary Institute (LPI) Venus Explorations Analysis Group (VEXAG) National Aeronautics and Space Administration (NASA) Conveners Virgil L. Sharpton Lunar and Planetary Institute Universities Space Research Association Larry Esposito Laboratory for Atmosphere and Space Physics University of Colorado Christophe Sotin Jet Propulsion Laboratory California Institute of Technology Scientific Organizing Committee Virgil L. Sharpton, Lunar and Planetary Institute, Universities Space Research Association Ben Bussey, Applied Physics Laboratory, Johns Hopkins University Larry Esposito, Laboratory for Atmosphere and Space Physics, University of Colorado Martha Gilmore, Department of Earth and Environmental Sciences, Wesleyan University Lori Glaze, NASA Goddard Space Flight Center Robert Herrick, Geophysical Institute, University of Alaska, Fairbanks Stephanie Johnston, Department of Geology, University of Maryland Christopher Lee, Ashima Research Christophe Sotin, Jet Propulsion Laboratory, California Institute of Technology Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 LPI Contribution No. 1781 Compiled in 2014 by Meeting and Publication Services Lunar and Planetary Institute USRA Houston 3600 Bay Area Boulevard, Houston TX 77058-1113 This material is based upon work supported by NASA under Award No. NNX08AC28A. Any opinions, findings, and conclusions or recommendations expressed in this volume are those of the author(s) and do not necessarily reflect the views of the National Aeronautics and Space Administration. The Lunar and Planetary Institute is operated by the Universities Space Research Association under a cooperative agreement with the Science Mission Directorate of the National Aeronautics and Space Administration. Material in this volume may be copied without restraint for library, abstract service, education, or personal research purposes; however, republication of any paper or portion thereof requires the written permission of the authors as well as the appropriate acknowledgment of this publication. Abstracts in this volume may be cited as Author A. B. (2014) Title of abstract. In Workshop on Venus Exploration Target, p. XX. LPI Contribution No. 1781, Lunar and Planetary Institute, Houston. ISSN No. 0161-5297 Preface This volume contains abstracts that have been accepted for presentation at the Workshop on Venus Exploration Targets, May 19–21, 2014, Houston, Texas. Administration and publications support for this meeting were provided by the staff of the Meeting and Publication Services Department at the Lunar and Planetary Institute. Technical Guide to Sessions Monday, May 19, 2014 8:00 a.m. Great Room Registration 9:00 a.m. Lecture Hall Introductory Plenary 1:30 p.m. Lecture Hall Poster Plenary 4:00 p.m. Great Room Poster Session Within the Atmosphere From Orbit On the Surface Tuesday, May 20, 2014 8:30 a.m. Breakout Rooms Targets and Objectives Breakout Session Hess Room Within the Atmosphere Berkners ABC On the Surface Berkners DEF From Orbit 1:30 p.m. Lecture Hall Targets and Objective Plenary 2:45 p.m. Breakout Rooms Data Requirements Breakout Session Hess Room Within the Atmosphere Berkners ABC On the Surface Berkners DEF From Orbit Wednesday, May 21, 2014 8:30 a.m. Lecture Hall Data Requirements Plenary 9:30 a.m. Breakout Rooms Instrumentation and Enabling Assets Breakout Session Hess Room Within the Atmosphere Berkners ABC On the Surface Berkners DEF From Orbit 1:30 p.m. Lecture Hall Final Plenary Contents Program ........................................................................................................................................................................ ix Venus Discovery-Class Balloon Missions: Science Objectives and Desired Latitudinal and Longitudinal Coverage K. H. Baines, S. K. Atreya, M. Bullock, D. Crisp, L. W. Esposito, D. Grinspoon, J. L. Hall, S. S. Limaye, P. R. Mahaffy, C. T. Russell, C. R. Webster, and K. Zahnle ...................................................... 1 Potential Landing Sites for Future Missions to Venus A. T. Basilevsky, M. A. Ivanov, and J. W. Head .............................................................................................. 3 Orbital Reconnaissance of Pyroclastic Deposits on Venus L. M. Carter, D. B. Campbell, and B. A. Campbell ......................................................................................... 5 Raman and Laser-Induced Breakdown Spectroscopy (LIBS) Geochemical Analysis Under Venus Atmospheric Pressure S. M. Clegg, M. D. Dyar, S. K. Sharma, A. K. Misra, R. C. Wiens, S. E. Smrekar, S. Maurice, and L. Esposito ............................................................................................................................ 7 The Highlands of Venus C. G. Cochrane and R. C. Ghail...................................................................................................................... 9 Exploration Targets for a Mission Concept with Multiple Venus Gliders J. A. Cutts, D. C. Nunes, K. L. Mitchell, D. A. Senske, M. T. Pauken, L. H. Matthies, and P. Tokamaru .................................................................................................................. 11 Exploration Targets in the Venus Cloud Regions J. A. Cutts, T. Widemann, S. Limaye, K. H. Baines, C. F. Wilson, P. Voss, J. L. Hall, J. Nott, and V. Kerzhanovich ......................................................................................................................... 13 Venus Geochemistry Mission: A Global Perspective M. S. Duncan and M. B. Weller ..................................................................................................................... 15 In Situ Measurements on Venus Plains, Domes, Canali, and Tessera: Choices and Constraints for Mineralogical and Geochemical Measurements M. D. Dyar, A. H. Treiman, S. M. Clegg, R. C. Wiens, J. Filiberto, S. K. Sharma, and A. K. Misra ...................................................................................................................... 17 The Surface of Venus After VIRTIS on Venus Express: Laboratory Analogs and the Venus Emissivity Mapper S. Ferrari, J. Helbert, A. Maturilli, D. M. Dyar, N. Mueller, and L. T. Elkins-Tanton ................................. 19 Venera-D: New Russian Attempt to Land on the Surface of Venus M. V. Gerasimov, L. V. Zasova, and N. I. Ignatiev ........................................................................................ 21 EnVision: Design Options for the M4 Call R. C. Ghail and EnVision Science Team ....................................................................................................... 22 Which Tesserae are the best Tesserae to Measure Tessera Composition? M. S. Gilmore ................................................................................................................................................ 23 Importance of Geodetically Controlled Topography to Constrain Rates of Volcanism and Internal Magma Plumbing Systems L. S. Glaze, S. M. Baloga, J. B. Garvin, and L. C. Quick .............................................................................. 25 Mapping the Surface Composition of Venus in the Near Infrared J. Helbert, N. Müller, S. Ferrari, D. Dyar, S. Smrekar, J. W. Head, and L. Elkins-Tanton .......................... 27 Cleopatra Crater, a Circular Portal to the Soul of Venus R. R. Herrick.................................................................................................................................................. 29 Selection of Landing Sites for the Venera-D Mission M. A. Ivanov, A. T. Basilevsky, J. W. Head, L. V. Zasova, and E. N. Guseva ............................................... 31 Global Geologic Map of Venus: A Resource for Venus Exploration Planning and Site Selection M. A. Ivanov, J. W. Head, and A. T. Basilevsky ............................................................................................ 33 Rift System Architecture on Venus and Implications for Lithospheric Structure W. S. Kiefer ................................................................................................................................................... 35 Landing Sites Optimized for Understanding the Radar Anomalies on Venus E. Kohler, V. Chevrier, and C. Lacy ............................................................................................................. 37 Venus’ Surface Layer: A Neglected Class of Venus Exploration Targets M. A. Kreslavsky, N. V. Bondarenko, J. W. Head, A T. Basilevsky, and M. A. Ivanov .................................. 38 Exploration Targets in the Lower Atmosphere of Venus S. S. Limaye, L. S. Glaze, J. A. Cutts, C. F. Wilson, H. F. Parish, G. Schubert, K. H. Baines, C. C. Covey, and T. Widemann ..................................................................................................................... 40 Large Volcanic Edifices and Rises on Venus: The Benefits of Improved Topography and Gravity Data P. J. McGovern.............................................................................................................................................. 42 Is Venus Volcanically Active Today? P. J. Mouginis-Mark ...................................................................................................................................... 44 Late Impacts
Load more

Recommended publications
  • Planetary Geologic Mappers Annual Meeting
    Program Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 Planetary Geologic Mappers Annual Meeting June 12–14, 2018 • Knoxville, Tennessee Institutional Support Lunar and Planetary Institute Universities Space Research Association Convener Devon Burr Earth and Planetary Sciences Department, University of Tennessee Knoxville Science Organizing Committee David Williams, Chair Arizona State University Devon Burr Earth and Planetary Sciences Department, University of Tennessee Knoxville Robert Jacobsen Earth and Planetary Sciences Department, University of Tennessee Knoxville Bradley Thomson Earth and Planetary Sciences Department, University of Tennessee Knoxville Abstracts for this meeting are available via the meeting website at https://www.hou.usra.edu/meetings/pgm2018/ Abstracts can be cited as Author A. B. and Author C. D. (2018) Title of abstract. In Planetary Geologic Mappers Annual Meeting, Abstract #XXXX. LPI Contribution No. 2066, Lunar and Planetary Institute, Houston. Guide to Sessions Tuesday, June 12, 2018 9:00 a.m. Strong Hall Meeting Room Introduction and Mercury and Venus Maps 1:00 p.m. Strong Hall Meeting Room Mars Maps 5:30 p.m. Strong Hall Poster Area Poster Session: 2018 Planetary Geologic Mappers Meeting Wednesday, June 13, 2018 8:30 a.m. Strong Hall Meeting Room GIS and Planetary Mapping Techniques and Lunar Maps 1:15 p.m. Strong Hall Meeting Room Asteroid, Dwarf Planet, and Outer Planet Satellite Maps Thursday, June 14, 2018 8:30 a.m. Strong Hall Optional Field Trip to Appalachian Mountains Program Tuesday, June 12, 2018 INTRODUCTION AND MERCURY AND VENUS MAPS 9:00 a.m. Strong Hall Meeting Room Chairs: David Williams Devon Burr 9:00 a.m.
    [Show full text]
  • Copyrighted Material
    Index Abulfeda crater chain (Moon), 97 Aphrodite Terra (Venus), 142, 143, 144, 145, 146 Acheron Fossae (Mars), 165 Apohele asteroids, 353–354 Achilles asteroids, 351 Apollinaris Patera (Mars), 168 achondrite meteorites, 360 Apollo asteroids, 346, 353, 354, 361, 371 Acidalia Planitia (Mars), 164 Apollo program, 86, 96, 97, 101, 102, 108–109, 110, 361 Adams, John Couch, 298 Apollo 8, 96 Adonis, 371 Apollo 11, 94, 110 Adrastea, 238, 241 Apollo 12, 96, 110 Aegaeon, 263 Apollo 14, 93, 110 Africa, 63, 73, 143 Apollo 15, 100, 103, 104, 110 Akatsuki spacecraft (see Venus Climate Orbiter) Apollo 16, 59, 96, 102, 103, 110 Akna Montes (Venus), 142 Apollo 17, 95, 99, 100, 102, 103, 110 Alabama, 62 Apollodorus crater (Mercury), 127 Alba Patera (Mars), 167 Apollo Lunar Surface Experiments Package (ALSEP), 110 Aldrin, Edwin (Buzz), 94 Apophis, 354, 355 Alexandria, 69 Appalachian mountains (Earth), 74, 270 Alfvén, Hannes, 35 Aqua, 56 Alfvén waves, 35–36, 43, 49 Arabia Terra (Mars), 177, 191, 200 Algeria, 358 arachnoids (see Venus) ALH 84001, 201, 204–205 Archimedes crater (Moon), 93, 106 Allan Hills, 109, 201 Arctic, 62, 67, 84, 186, 229 Allende meteorite, 359, 360 Arden Corona (Miranda), 291 Allen Telescope Array, 409 Arecibo Observatory, 114, 144, 341, 379, 380, 408, 409 Alpha Regio (Venus), 144, 148, 149 Ares Vallis (Mars), 179, 180, 199 Alphonsus crater (Moon), 99, 102 Argentina, 408 Alps (Moon), 93 Argyre Basin (Mars), 161, 162, 163, 166, 186 Amalthea, 236–237, 238, 239, 241 Ariadaeus Rille (Moon), 100, 102 Amazonis Planitia (Mars), 161 COPYRIGHTED
    [Show full text]
  • CRATER MORPHOMETRY on VENUS. C. G. Cochrane, Imperial College, London ([email protected])
    Lunar and Planetary Science XXXIV (2003) 1173.pdf CRATER MORPHOMETRY ON VENUS. C. G. Cochrane, Imperial College, London ([email protected]). Introduction: Most impact craters on Venus are propagating east and north/south. Can be minimised if pristine, and provide probably the best available ana- framelets have good texture on the left-hand side. logs for craters on Earth soon after impact; hence the Prominence extension – features extend down value of measuring their 3-D shape to known accuracy. range into a ridge, eg central peak linked to the rim. The USGS list 967 craters: from the largest, Mead at Probably due to radar shadowing differences, these are 270 km diameter, to the smallest, unnamed at 1.3 km. easily recognised and avoided during analysis. Initially, research focussed on the larger craters. Araration (from Latin: Arare to plough) consists of Schaber et al [1] (11 craters >50 km) and Ivanov et al parallel furrows some 50 pixels apart, oriented north- [2] (31 craters >70 km) took crater depth from Magel- south, and at least tens of metres deep. Fig 2, a lan altimetry. Sharpton [3] (94 craters >18 km) used floor-offsets in Synthetic Aperture Radar (SAR) F- MIDR pairs, as did Herrick & Phillips [4]. They list many parameters but not depth for 891 craters. The LPI database1 now numbers 941. Herrick & Sharpton [5] made Digital Elevation Models (DEMs) of all cra- ters at least partially imaged twice down to 12 km, and 20 smaller craters down to 3.6 km. Using FMAP im- ages and the Magellan Stereo Toolkit (MST) v.1, they automated matches every 900m but then manually ed- ited the resultant data.
    [Show full text]
  • N93"14373 : ,' Atmospheric Density, Collapse of Near-Rim Ejecta Into a Flow Crudely MAGELLAN PROJECT PROGRESS REPORT
    106 lnternational Colloquium on Venus ment as observed on Venus [5,6]. Such a process accounts for the results in late-stage reworking, if not self-destruction, of ejecta long run-out flows consistently originating downrange in oblique faciescmplaced earlier.Surfaceexpressionshould includebedforrns impacts (i.e., oplmsite the missing ejecta sector) even if uphill from (e.g., meter-scale dunes and decicentlmeter-scale ripples) reflect- the crater rim. Atmospheric mflxflence and recovery winds deeoupled hag eddies created in the boundary layer at the surface. Because from the gradient-controlled basal run-out flow continues down- radar imaging indicates small-scale surface roughness (as well as range and produces wind streaks in the Ice of topographic highs. resolved surface features), regions affected by such long-lived low- Turbulence accompanying the basal density flows may also produce energy processes can extend to enormous distances. Such areas are wind streak patterns. Uprange the atmosphere is drawn in behind the not directly related to ejecta emplacement but reflect the almo- f'_reball(and enhancedby the impinging impactor wake), resulting spheric equivalent to distant seismic waves in the target. Late-stage in strong winds that will last at least as long as the time for crater atmospheric processes also include interactions with upper-level formation (i.e., minutes). Such winds can entrain and saltate surface winds. Deflection of the winds around the advancing/expanding materials as observed in laboratory experiments [2,3] and inferred fireball creates a parabolic-shaped interface aloft. This is preserved from large transverse dunes uprange on Venus [2]. in the fall-out of f'mer debris for impacts directed into the winds aloft Atmospheric Effects on Ballistic EJecta: Even on Venus, (from the west) but self-destructs if the impact is directed with the target debris will be ballistically ejected and form a conical ejecta wind.
    [Show full text]
  • Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 Μm Images
    atmosphere Article Winds in the Lower Cloud Level on the Nightside of Venus from VIRTIS-M (Venus Express) 1.74 µm Images Dmitry A. Gorinov * , Ludmila V. Zasova, Igor V. Khatuntsev, Marina V. Patsaeva and Alexander V. Turin Space Research Institute, Russian Academy of Sciences, 117997 Moscow, Russia; [email protected] (L.V.Z.); [email protected] (I.V.K.); [email protected] (M.V.P.); [email protected] (A.V.T.) * Correspondence: [email protected] Abstract: The horizontal wind velocity vectors at the lower cloud layer were retrieved by tracking the displacement of cloud features using the 1.74 µm images of the full Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M) dataset. This layer was found to be in a superrotation mode with a westward mean speed of 60–63 m s−1 in the latitude range of 0–60◦ S, with a 1–5 m s−1 westward deceleration across the nightside. Meridional motion is significantly weaker, at 0–2 m s−1; it is equatorward at latitudes higher than 20◦ S, and changes its direction to poleward in the equatorial region with a simultaneous increase of wind speed. It was assumed that higher levels of the atmosphere are traced in the equatorial region and a fragment of the poleward branch of the direct lower cloud Hadley cell is observed. The fragment of the equatorward branch reveals itself in the middle latitudes. A diurnal variation of the meridional wind speed was found, as east of 21 h local time, the direction changes from equatorward to poleward in latitudes lower than 20◦ S.
    [Show full text]
  • SFSC Search Down to 4
    C M Y K www.newssun.com EWS UN NHighlands County’s Hometown-S Newspaper Since 1927 Rivalry rout Deadly wreck in Polk Harris leads Lake 20-year-old woman from Lake Placid to shutout of AP Placid killed in Polk crash SPORTS, B1 PAGE A2 PAGE B14 Friday-Saturday, March 22-23, 2013 www.newssun.com Volume 94/Number 35 | 50 cents Forecast Fire destroys Partly sunny and portable at Fred pleasant High Low Wild Elementary Fire alarms “Myself, Mr. (Wally) 81 62 Cox and other administra- Complete Forecast went off at 2:40 tors were all called about PAGE A14 a.m. Wednesday 3 a.m.,” Waldron said Wednesday morning. Online By SAMANTHA GHOLAR Upon Waldron’s arrival, [email protected] the Sebring Fire SEBRING — Department along with Investigations into a fire DeSoto City Fire early Wednesday morning Department, West Sebring on the Fred Wild Volunteer Fire Department Question: Do you Elementary School cam- and Sebring Police pus are under way. Department were all on think the U.S. govern- The school’s fire alarms the scene. ment would ever News-Sun photo by KATARA SIMMONS Rhoda Ross reads to youngsters Linda Saraniti (from left), Chyanne Carroll and Camdon began going off at approx- State Fire Marshal seize money from pri- Carroll on Wednesday afternoon at the Lake Placid Public Library. Ross was reading from imately 2:40 a.m. and con- investigator Raymond vate bank accounts a children’s book she wrote and illustrated called ‘A Wildflower for all Seasons.’ tinued until about 3 a.m., Miles Davis was on the like is being consid- according to FWE scene for a large part of ered in Cyprus? Principal Laura Waldron.
    [Show full text]
  • Investigating Mineral Stability Under Venus Conditions: a Focus on the Venus Radar Anomalies Erika Kohler University of Arkansas, Fayetteville
    University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2016 Investigating Mineral Stability under Venus Conditions: A Focus on the Venus Radar Anomalies Erika Kohler University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Geochemistry Commons, Mineral Physics Commons, and the The unS and the Solar System Commons Recommended Citation Kohler, Erika, "Investigating Mineral Stability under Venus Conditions: A Focus on the Venus Radar Anomalies" (2016). Theses and Dissertations. 1473. http://scholarworks.uark.edu/etd/1473 This Dissertation is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Investigating Mineral Stability under Venus Conditions: A Focus on the Venus Radar Anomalies A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Space and Planetary Sciences by Erika Kohler University of Oklahoma Bachelors of Science in Meteorology, 2010 May 2016 University of Arkansas This dissertation is approved for recommendation to the Graduate Council. ____________________________ Dr. Claud H. Sandberg Lacy Dissertation Director Committee Co-Chair ____________________________ ___________________________ Dr. Vincent Chevrier Dr. Larry Roe Committee Co-chair Committee Member ____________________________ ___________________________ Dr. John Dixon Dr. Richard Ulrich Committee Member Committee Member Abstract Radar studies of the surface of Venus have identified regions with high radar reflectivity concentrated in the Venusian highlands: between 2.5 and 4.75 km above a planetary radius of 6051 km, though it varies with latitude.
    [Show full text]
  • Venus in Two Acts Saidiya Hartman
    Venus in Two Acts Saidiya Hartman Small Axe, Number 26 (Volume 12, Number 2), June 2008, pp. 1-14 (Article) Published by Duke University Press For additional information about this article https://muse.jhu.edu/article/241115 Access provided by University Of Maryland @ College Park (13 Mar 2017 20:04 GMT) Venus in Two Acts Saidiya Hartman ABSTR A CT : This essay examines the ubiquitous presence of Venus in the archive of Atlantic slavery and wrestles with the impossibility of discovering anything about her that hasn’t already been stated. As an emblematic figure of the enslaved woman in the Atlantic world, Venus makes plain the convergence of terror and pleasure in the libidinal economy of slavery and, as well, the intimacy of history with the scandal and excess of literature. In writing at the limit of the unspeak- able and the unknown, the essay mimes the violence of the archive and attempts to redress it by describing as fully as possible the conditions that determine the appearance of Venus and that dictate her silence. In this incarnation, she appears in the archive of slavery as a dead girl named in a legal indict- ment against a slave ship captain tried for the murder of two Negro girls. But we could have as easily encountered her in a ship’s ledger in the tally of debits; or in an overseer’s journal—“last night I laid with Dido on the ground”; or as an amorous bed-fellow with a purse so elastic “that it will contain the largest thing any gentleman can present her with” in Harris’s List of Covent- Garden Ladies; or as the paramour in the narrative of a mercenary soldier in Surinam; or as a brothel owner in a traveler’s account of the prostitutes of Barbados; or as a minor character in a nineteenth-century pornographic novel.1 Variously named Harriot, Phibba, Sara, Joanna, Rachel, Linda, and Sally, she is found everywhere in the Atlantic world.
    [Show full text]
  • Climate Histories of Mars and Venus, and the Habitability of Planets
    CLIMATE HISTORIES OF MARS AND VENUS, AND THE HABITABILITY OF PLANETS In the temporal sequence that Part III of the book has ¡NTRODUCT¡ON 15.1 been following, we stand near the end of the Archean eon. Earth at the close of the Archean,2.5 billion years ago, By this point in time, the evolution of Venus and its atmo- was a world in which life had arisen and plate tectonics sphere almost certainly had diverged from that of Earth, dominated, the evolution of the crust and the recycling of and Mars was on its way to being a cold, dry world, if volatiles. Yet oxygen (Oz) still was not prevalent in the it had not already become one. This is the appropriate atmosphere, which was richer in COz than at present. In moment in geologic time, then, to consider how Earth's this last respect, Earth's atmosphere was somewhat like neighboring planets diverged so greatly in climate, and to that of its neighbors, Mars and Venus, which today retain ponder the implications for habitable planets throughout this more primitive kind of atmosphere. the cosmos. In the following chapter, we consider why Speculations on the nature of Mars and Venus were, Earth became dominated by plate tectonics, but Venus prior to the space program, heavily influenced by Earth- and Mars did not. Understanding this is part of the key centered biases and the poor quality of telescopic observa- to understanding Earth's clement climate as discussed in tions (figure 15.1). Thirty years of U.S. and Soviet robotic chapter 1.4.
    [Show full text]
  • Cleopatra Crater on Venus: Happy Solution of the Volcanic Vs
    CLEOPATRA CRATER ON VENUS: HAPPY SOLUTION OF THE VOLCANIC VS. IMPACT CRATER CONTROVERSY; A.T. Basilevsky, A.T. Vernadsky Institute of Geochemistry and Analytical chemistry, Moscow, USSR, and G.G. Schaber, U.S. Geological Survey, Flagstaff AZ 86001 ~ntroduction. Cleopatra is a 100-km-diameter crater on the eastern slope of Maxwell Montes in western Ishtar Terra. For over 12 years, Cleopatra has been the subject of scientific controversy. Discovered during the Pioneer Venus altimetric survey, this feature was initially interpreted as a caldera near the top of a giant volcanic construct, Maxwell Montes [I]. Venera 15/16 data and recent Arecibo radar images show, however, that the Maxwell Montes appear to be more of a tectonic construct, with little or no resemblance to other giant shields known in the Solar System; thus, a nonvolcanic origin of Cleopatra was proposed [2-61. The similarity of the double-ring structure of Cleopatra to those of other multi-ring impact craters of similar size on Venus and the Moon, Mercury, and Mars was more recently given by Basilevsky and Ivanov [7] as the primarily reason to consider this feature an impact crater. At the same time, some characteristics of Cleopatra seemed to contradict an impact origin. For example, Schaber et al. [8], suggestingthat a definitive verification of a volcanic or impact origin would probably require Magellan data, proposed that the evidence from Venera 15/16 and earlier data for a probable volcanic origin for Cleopatra is substantial. They cited, among other points: (1) the absence of a raised rim and highly backscattering ejecta deposits; (2) the crater's association with plains-forming deposits immediately downslope to the east, interpreted as probable lava flows emanating from a distinct breach in the crater's rim; (3) the excessive depth (2.5 km) and depth-to-diameter ratio (0.028) of the crater, (4) the offset of the inner and outer craters; and (5) the crater's position in what was interpreted as a regional tectonic framework.
    [Show full text]
  • Styles of Deformation in Ishtar Terra and Their Implications
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 97, NO. El0, PAGES 16,085-16,120, OCTOBER 25, 1992 Stylesof Deformationin IshtarTerra and Their Implications Wn.T.TAMM. KAU•A,• DOAN•L. BINDSCHAD•-R,l ROBERT E. GPaM•,2'3 VICKIL. HANSEN,2KARl M. ROBERTS,4AND SUZANNE E. SMREr,AR s IshtarTerra, the highest region on Venus, appears to havecharacteristics of both plume uplifts and convergent belts.Magellan imagery over longitudes 330ø-30øE indicates a great variety of tectonicand volcanic activity, with largevariations within distances of onlya few 100km. Themost prominent terrain types are the volcanic plains of Lakshmiand the mountain belts of Maxwell,Freyja, and Danu. Thebelts appear to havemarked variations in age. Thereare also extensive regions of tesserain boththe upland and outboard plateaus, some rather featureless smoothscarps, flanking basins of complexextensional tectonics, and regions of gravitationalor impactmodifica- tion.Parts of Ishtarare the locations of contemporaryvigorous tectonics and past extensive volcanism. Ishtar appearsto be the consequence of a history of several100 m.y., in whichthere have been marked changes in kinematic patternsand in whichactivity at any stage has been strongly influenced by the past. Ishtar demonstrates three general propertiesof Venus:(1) erosionaldegradation is absent,leading to preservationof patternsresulting from past activity;(2) manysurface features are the responses ofa competentlayer less than 10 km thick to flowsof 100km orbroaderscale; and (3) thesebroader scale flows are controlled mainly by heterogeneities inthe mantle. Ishtar Terra doesnot appear to bethe result of a compressionconveyed by anEarthlike lithosphere. But there is stilldoubt as to whetherIshtar is predominantlythe consequence of a mantleupflow or downflow.Upflow is favoredby the extensivevolcanic plain of Lakshmiand the high geoid: topography ratio; downflow is favoredby the intense deformationof themountain belts and the absence of majorrifts.
    [Show full text]
  • The Magellan Spacecraft at Venus by Andrew Fraknoi, Astronomical Society of the Pacific
    www.astrosociety.org/uitc No. 18 - Fall 1991 © 1991, Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, CA 94112. The Magellan Spacecraft at Venus by Andrew Fraknoi, Astronomical Society of the Pacific "Having finally penetrated below the clouds of Venus, we find its surface to be naked [not hidden], revealing the history of hundreds of millions of years of geological activity. Venus is a geologist's dream planet.'' —Astronomer David Morrison This fall, the brightest star-like object you can see in the eastern skies before dawn isn't a star at all — it's Venus, the second closest planet to the Sun. Because Venus is so similar in diameter and mass to our world, and also has a gaseous atmosphere, it has been called the Earth's "sister planet''. Many years ago, scientists expected its surface, which is perpetually hidden beneath a thick cloud layer, to look like Earth's as well. Earlier this century, some people even imagined that Venus was a hot, humid, swampy world populated by prehistoric creatures! But we now know Venus is very, very different. New radar images of Venus, just returned from NASA's Magellan spacecraft orbiting the planet, have provided astronomers the clearest view ever of its surface, revealing unique geological features, meteor impact craters, and evidence of volcanic eruptions different from any others found in the solar system. This issue of The Universe in the Classroom is devoted to what Magellan is teaching us today about our nearest neighbor, Venus. Where is Venus, and what is it like? Spacecraft exploration of Venus's surface Magellan — a "recycled'' spacecraft How does Magellan take pictures through the clouds? What has Magellan revealed about Venus? How does Venus' surface compare with Earth's? What is the next step in Magellan's mission? If Venus is such an uninviting place, why are we interested in it? Reading List Why is it so hot on Venus? Where is Venus, and what is it like? Venus orbits the Sun in a nearly circular path between Mercury and the Earth, about 3/4 as far from our star as the Earth is.
    [Show full text]