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COLLOQUIUM on ) I T R NARA-CO-19007o Papers Presented to the INTERNATIONAL COLLOQUIUM ON ) I t_ r" i 1 i*- c; ,...4 I "r I VENUS _._ _._. ,.-,- (j ,-"4 o 3 :. ,.-., j ,- ' t ? e,- _L "r ", ) I _7 _a { i 2 -3-- AUGUST 10-12, 1992 PASADENA, CALIFORNIA PAPERS PRESENTED TO THE INTERNATIONAL COLLOQUIUM ON VENUS August 10-12, 1992 Pasadena, California Sponsored by National Aeronautics and Space Administration " Jet Propulsion Laboratory Lunar and Planetary Institute Russian Academy of Sciences International Union of Geological Sciences International Space Year LPI Contribution No. 789 Compiled in 1992 by Lunar and Planetary Institute 3600 Bay Area Boulevard Houston TX 77058-1113 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 appropriate acknowledgment of this publication. The Lunar and Planetary Institute is operated by the Universities Space Research Association under Contract No. NASW-4574 with the National Aeronautics and Space Administration. PREFACE This volume contains short papers that have been accepted for the International Colloquium on Venus, August 10-12, Pasadena, California. The Program Committee consisted of R. Stephen Saunders (Jet Propulsion Laboratory) and Sean C. Solomon (Massachusetts Institute of Technology), chairmen; Raymond Arvidson (Washington University); Valery L. Barsukov, Mikhail Yu. Zolotov, Alexander T. Basilevsky (Vernadsky Institute); Vassily Moroz (Institute for Space Research); Donald Bo Campbell (Cornell University); Thomas Donahue (University of Michigan); James W. Head HI (Brown University); Pamela Jones (Lunar and Planetary Institute); Mona Jasnow, Andrew Morrison, Timothy Parker, Jeffrey Plaut, Ellen Stofan, Tommy Thompson, Cathy Weitz (Jet Propulsion Laboratory); Gordon Pettengill (Massachusetts Institute of Technology); and Janet Luhmann (University of California, Los Angeles). Logistics and administrative support were provided by the Program Services Depart- ment staff at the Lunar and Planetary Institute. This volume was prepared by the Publica- tions Services Department staff at the Lunar and Planetary Institute. TABLE OF CONTENTS Venus Radar Mapping from the Venera 15 and 16 Spacecrafts: Results and Restrictions E. L. Akim, A. I. Zakharov, and A. P. Krivtsov ........................................................................... 1 Local-Time Asymmetries in the Venus Thermosphere M. J. Alexander, A. I. F. Stewart, and S. W. Bougher .................................................................. 1 Ringed Impact Craters on Venus: An Analysis from Magellan Images J. S. Alexopoulos and W. B. McKinnon ....................................................................................... 2 Is Ishtar Terra a Thickened Basaltic Crust? J. Arkani-Hamed .......................................................................................................................... 4 Constraints on the Thermal Evolution of Venus Inferred from Magellan Data J. Arkani-Hamed, G. G. Schaber, and R. G. Strom ....................................................................... 5 Surface Processes on Venus R. E. Arvidson ............................................................................................................................. 6 Shield Fields: Concentrations of Small Volcanic Edifices on Venus J. C. Aubele and L. S. Crumpler .................................................................................................. 7 The Geology of the Venera/Vega Landing Sites A. T. Basilevsky and C. M. Weitz ................................................................................................ 8 Global Deformation on the Surface of Venus F. Bilotti, C. Connors, and J. Suppe ........................................................................................... 10 Coldspots or Hotspots? The Origin of Plateau-shaped Highlands on Venus D. L. Bindschadler. .................................................................................................................... 12 Monte Carlo Modeling of the Resurfacing of Venus M. A. Bullock, D. H. Grinspoon, and J. W. Head ....................................................................... 14 Debris Avalanches and Slumps on the Margins of Volcanic Domes on Venus: Characteristics of Deposits M. H. Bulmer, J. E. Guest, K. Beretan, G. Michaels, and S. Saunders ........................................ 14 Mixed-Valence Iron Minerals on Venus: Fe2*-Fe z+ Oxides and Oxy-silicates Formed by Surface-Atmosphere Interactions R. G. Burns and D. W. Straub .................................................................................................... 15 Thermal Buoyancy on Venus: Preliminary Results of Finite Element Modeling J. D. Burt and J. W. Head ........................................................................................................... 17 4 PRECEt')_,NG P._GE BLANK NOT RLMED v Y _j. .1 o.rawa Erosion Vs. Construction: The Origin of Venusian Channels D. B. J. Bussey and J. E. Guest .................................................................................................. 18 Polarization Properties and Earth-based Radar Measurements of Venus in the Post-Magellan Era D. B. Campbell .......................................................................................................................... 19 Bright Crater Ouo"lows: Possible Emplacement Mechanisms D. J. Chadwick, G. G. Schaber, R. G. Strom, and D. M. Duval .................................................. 20 Image Processing and Products for the Magellan Mission to Venus J. Clark, D. Alexander, P. Andres, S. Lewicki, and M. McAuley ............................................... 22 The Thermosphere and Ionosphere of Venus T. E. Cravens ............................................................................................................................. 22 Near4nfrared Oxygen Airglow from the Venus Nightside D. Crisp, V. S. Meadows, D. A. Allen, B. Bezard, C. DeBergh, and J.-P. Maillard ...................................................................................................................... 23 Global Correlation of Volcanic Centers on Venus with Uplands and with Extension: Influence of Mantle Convection and Altitude L. S. Crumpler, J. W. Head, and J. C. Aubele ............................................................................ 25 The Spin Vector of Venus Determined from Magellan Data M. E. Davies, T. R. Colvin, P. G. Rogers, P. W. Chodas, and W. L. Sjogren ............................. 27 Monte Carlo Computer Simulations of Venus Equilibrium and Global Resurfacing Models D. D. Dawson, R. G. Strom, and G. G. Schaber ......................................................................... 27 Methane Measurement by the Pioneer Venus Large Probe Neutral Mass Spectrometer T. M. Donahue and R. R. Hodges Jr .......................................................................................... 29 Viscoelastic Relaxation of Venusian Coronae and Mountain Belts: Constraints on Global Heat Flow and Tectonism I. Duncan and A. Leith .............................................................................................................. 29 Flexural Analysis of Uplifted Rift Flanks on Venus S. A. Evans, M. Simons, and S. C. Solomon .............................................................................. 30 Understanding the Variation in the Millimeter-Wave Emission of Venus A. K. Fahd and P. G. Steffes ...................................................................................................... 32 Radar Scattering Properties of Pancakelike Domes on Venus P. G. Ford and G. H. Pettingill ................................................................................................... 34 vi Sequential Deformation of Plains Along Tessera Boundaries on Venus: Evidence from Alpha Regio M. S. Gilmore and J. W. Head ................................................................................................... 34 Venusian Hydrology: Steady State Reconsidered D. H. Grinspoon ......................................................................................................................... 36 Determining Stress States Using Dike Swarms: The Lauma Dorsa Example E. B. Grosfils and J. W. Head .................................................................................................... 37 Venus Mesospheric Winds and the Carbon Monoxide Bulge M. A. Gurwell, D. O. Muhleman, and K. P. Shah ...................................................................... 39 Tectonics and Volcanism of Eastern Aphrodite Terra: No Subduction, No Spreading V. L. Hansen, M. Keep, R. R. Herrick, and R. J. Phillips ........................................................... 40 Western Aphrodite Terra, Tectonics, Geology, and Line-of-Sight Gravity J. E. Hays and P. Morgan ........................................................................................................... 41 Venus Volcanism: A Global Overview from Magellan Data J. W. Head, L. S. Crumpler, J. C. Aubele, and the Magellan Team ............................................ 43 Chemical Differentiation on One-Plate Planets: Predictions and Geologic Observations for Venus J. W. Head, E. M. Parmentier, and P. C. Hess ............................................................................ 45 Dynamics of the Venus Atmosphere A. P. Ingersoll ...........................................................................................................................
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