The Importance of Venus Tesserae and Remaining Open Questions
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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. -
Testing Evolutionary Models for Venus with the DAVINCI+ Mission
EPSC Abstracts Vol. 14, EPSC2020-534, 2020 https://doi.org/10.5194/epsc2020-534 Europlanet Science Congress 2020 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Venus, Earth's divergent twin?: Testing evolutionary models for Venus with the DAVINCI+ mission Walter S. Kiefer1, James Garvin2, Giada Arney2, Sushil Atreya3, Bruce Campbell4, Valeria Cottini2, Justin Filiberto1, Stephanie Getty2, Martha Gilmore5, David Grinspoon6, Noam Izenberg7, Natasha Johnson2, Ralph Lorenz7, Charles Malespin2, Michael Ravine8, Christopher Webster9, and Kevin Zahnle10 1Lunar and Planetary Institute/USRA, Houston, Texas, United States of America ([email protected]) 2NASA Goddard Space Flight Center, Greenbelt MD USA 3Planetary Science Laboratory, University of Michigan, Ann Arbor MI USA 4Center for Earth and Planetary Studies, Smithsonian Institution, Washington DC USA 5Dept. of Earth and Environmental Science, Wesleyan University, Middletown CT USA 6Planetary Science Institute, Tucson AZ USA 7Applied Physics Lab, Johns Hopkins University, Laurel MD USA 8Malin Space Science Systems, San Diego CA USA 9Jet Propulsion Laboratory, California Insitute of Technology, Pasadena CA USA 10NASA Ames Research Center, Moffet Field CA USA Understanding the divergent evolution of Venus and Earth is a fundamental problem in planetary science. Although Venus today has a hot, dry atmosphere, recent modeling suggests that Venus may have had a clement surface with liquid water until less than 1 billion years ago [1]. Venus today has a nearly stagnant lithosphere. However, Ishtar Terra’s folded mountain belts, 8-11 km high, morphologically resemble Tibet and the Himalaya mountains on Earth and apparently require several thousand kilometers of surface motion at some time in Venus’s past. -
Geological Evolution of Lada Terra, Venus
42nd Lunar and Planetary Science Conference (2011) 1090.pdf GEOLOGICAL EVOLUTION OF LADA TERRA, VENUS. P. Senthil Kumar 1,2 and James W. Head 2, National Geophysical Research Institute, CSIR, Hyderabad 500606, India ([email protected]); 2Department of Geological Sciences, Brown University, Providence, RI02912, USA ([email protected]) Introduction: In this study, we present the history depict outflow features inundating the ejecta deposits. of geologic processes at Lada Terra (V-56 Quadrangle) Lineaments are abundant in V-56. These are in the southern hemisphere of Venus, through geologic principally secondary deformation features such as mapping at 1:5,000,000 scale, using 250-m-per-pixel fractures, faults, grabens, linear ridges, and wrinkle Magellan SAR image and ArcGIS 9.3 software, ridges. In V-56, there are three concentric coronae following the methods of geologic unit definition and (e.g., Quetzalpetlatl, Eithinaho, and Serpantium), one characterization of planetary surfaces [1-3]. Geological double ringed corona (Otygen), seven asymmetric units in the V-56 were products of tectonics, coronae (e.g., Derceto, Demvamvit, Toyo-uke, volcanism, and impact cratering with characteristic Dyamenyuo and Ekhe-Burkhan) and one astra-like geomorphic expressions (Figure 1). Basically, this structure (Loo-Wit Mons). Radial and concentric quadrangle addresses how coronae evolved in fractures and grabens define the coronae structures. association with regional extensional belts, in addition The large extensional belts are composed of fractures, to evolution of tessera, regional plains and impact grabens and strike-slip zones. The most prominent craters, which are also significant geological units of tectonic features are the traverses of four large-scale Lada Terra. -
Observational Constraints on Venus Surface Composition and Geologic History
Comparative Tectonics and Geodynamics (2015) 5025.pdf OBSERVATIONAL CONSTRAINTS ON VENUS SURFACE COMPOSITION AND GEOLOGIC HISTORY. M. S. Gilmore, Dept. Earth & Environmental Sciences, Wesleyan University, 265 Church St., Mid- dletown CT 06457 [email protected], www.wesleyan.edu/planetary. Introduction: The Venus atmosphere precludes hematite, the high emissivity anomalies correspond to the visible-near-infrared hyperspectral observations more mafic (less weathered) compositions [10] and the that have revolutionized the study of the surface com- low emissivity anomalies correspond to more felsic position of mars, Mercury and the Moon. Our under- compositions [7, 9, 11]. If the weathering rate of bas- standing of the surface composition the Earth-sized alt to hematite is fast, this suggests the volcanoes are planet Venus is derived wholly from 1) geochemical geologically young [10]. analyses of rocks from 7 landing sites, 2) observations Tesserae – How felsic? The radiance flux corre- of the surface at 1µm through a spectral window in the sponds to low emissivity values for tessera terrain atmosphere. These data are supported by theoretical leading to the following radical conclusions about Ve- and laboratory studies of the weathering, rheology and nus: 1) tesserae have a different (more felsic, less fer- spectra of candidate rocks at Venus temperatures and rous) primary composition. This can include Archean atmospheric composition. – type (TTG) granites formed by dehydration of under- Bulk Composition: The Venera and Vega landers thrust slabs or the lower crust, or true granites which acquired drilled samples (rock + soil) at 7 locations on may require a mature global recycling mechanism in- Venus. Major elements were measured by XRF at 3 troducing water-rich rocks. -
Constraints on the Interior Dynamics of Venus
Constraints on the Interior Dynamics of Venus Sue Smrekar Jet Propulsion Laboratory Venus: Earth’s evil twin or distant cousin? Twin: Diameter is 5% smaller Same bulk composition Once had an ocean’s worth of water Average surface age: 0.3-1 b.y Evil Twin: Surface T ~460°C Surface P ~90 bars Atmosphere: CO greenhouse 2 No magnetic field Distant Cousin: No terrestial style plate tectonics Outline Available constraints Geologic overview Composition Topography, gravity Recent data Evidence for “Continents” Evidence for recent hotspot volcanism Implications for the interior Inferences (myths?) Catastrophic resurfacing No evidence for plate tectonic processes Venus interior is dry Geologic Overview Main Features Hotspots (analogs to Hawaii, etc) Coronae (smaller scale upwelling, delamination, combo) Chasmata (Troughs with fractures) Rifts (Chasmata w/graben) Subduction? (analogs to ocean-ocean subduction) Tessera Plateaus (highly deformed, isostatically compensated) Analogs to continents? Data: Magellan Mission: Early 1990s Topo (12-25 km footprint) Synthetic Apeture Radar Imaging (~125 m pixel) Gravity (Deg. & Order 40-90, ~500-250 km) Derived surface thermal emissivity from Venus Express Hotspots, Coronae, , ~10 Hotspots ~ 500 Coronae Type 1 Coronae + Type 2 Coronae Flow fields N. Hemisphere Hotspots S. Hemisphere Hotspots Hotspots, Coronae, , Type 1 Coronae + Type 2 Coronae Flow fields N. Hemisphere Hotspots S. Hemisphere Hotspots Hotspots, Coronae, , Type 1 Coronae + Type 2 Coronae Flow fields N. Hemisphere Hotspots S. Hemisphere Hotspots Hotspots, Coronae, , Rifts Type 1 Coronae + Type 2 Coronae Flow fields N. Hemisphere Hotspots S. Hemisphere Hotspots Soviet landers (1970s) had x- ray fluorescence and gamma- ray spectrometers. Composition Compositions all found to be basalts to alkaline basalts. -
Surface Processes in the Venus Highlands: Results from Analysis of Magellan and a Recibo Data
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 104, NO. E], PAGES 1897-1916, JANUARY 25, 1999 Surface processes in the Venus highlands: Results from analysis of Magellan and A recibo data Bruce A. Campbell Center for Earth and Planetary Studies, Smithsonian Institution, Washington, D.C. Donald B. Campbell National Astronomy and Ionosphere Ceiitei-, Cornell University, Ithaca, New York Christopher H. DeVries Department of Physics and Astronomy, University of Massachusetts, Amherst Abstract. The highlands of Venus are characterized by an altitude-dependent change in radar backscattcr and microwave emissivity, likely produced by surface-atmosphere weathering re- actions. We analyzed Magellan and Arecibo data for these regions to study the roughness of the surface, lower radar-backscatter areas at the highest elevations, and possible causes for areas of anomalous behavior in Maxwell Montes. Arecibo data show that circular and linear radar polarization ratios rise with decreasing emissivity and increasing Fresnel reflectivity, supporting the hypothesis that surface scattering dominates the return from the highlands. The maximum values of these polarization ratios are consistent with a significant component of multiple-bounce scattering. We calibrated the Arecibo backscatter values using areas of overlap with Magellan coverage, and found that the echo at high incidence angles (up to 70") from the highlands is lower than expected for a predominantly diffuse scattering regime. This behavior may be due to geometric effects in multiple scattering from surface rocks, but fur- ther modeling is required. Areas of lower radar backscatter above an upper critical elevation are found to be generally consistent across the equatorial highlands, with the shift in micro- wave properties occurring over as little as 5ÜÜ m of elevation. -
GLOBAL MORPHOLOGIC MAP of TESSERAE on VENUS. R. S. Albach1 and J
52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2232.pdf GLOBAL MORPHOLOGIC MAP OF TESSERAE ON VENUS. R. S. Albach1 and J. L. Whitten1, 1Department of Earth and Environmental Sciences, Tulane University, New Orleans, LA ([email protected]). Introduction: Tesserae are regions of high radar mapping was completed in ArcGIS Pro at a scale of backscatter and tectonic deformation that cover ~8% of 1:750,000 and covered Alpha Regio, Phoebe Regio, the surface of Venus [1]. Despite being the oldest units Manatum Tessera, Ovda Regio, Aphrodite Terra, and on Venus [1], many open questions about tesserae re- Thetis Regio. Individual tesserae are divided into tex- main like their composition, surface evolution, and for- turally-distinct regions. “Texturally distinct” describes mation mechanism. Proposed formation mechanisms differences in the spacing, the shape, and the orientation include upwelling or downwelling of the mantle [2, 3]. of the tectonic features such as graben, fractures, and Tesserae material has been variously proposed to be ba- ridges that compose tesserae. Each texturally distinct re- saltic or felsic [4, 5]. Comprehensive global studies gion was grouped into classes (e.g., A, B, C) based on aimed at determining the composition and formation the similarity of their surface morphologies. mechanism(s) of tesserae are limited by available global The Magellan SAR base map is dynamically- datasets of the surface of Venus from the Magellan mis- stretched using the screen area for radar-bright tesserae. sion (SAR, emissivity, topography), VIRTIS on Venus Dynamic stretching prevents high average backscatter Express, and low-resolution radar data from Arecibo. -
Envision – Front Cover
EnVision – Front Cover ESA M5 proposal - downloaded from ArXiV.org Proposal Name: EnVision Lead Proposer: Richard Ghail Core Team members Richard Ghail Jörn Helbert Radar Systems Engineering Thermal Infrared Mapping Civil and Environmental Engineering, Institute for Planetary Research, Imperial College London, United Kingdom DLR, Germany Lorenzo Bruzzone Thomas Widemann Subsurface Sounding Ultraviolet, Visible and Infrared Spectroscopy Remote Sensing Laboratory, LESIA, Observatoire de Paris, University of Trento, Italy France Philippa Mason Colin Wilson Surface Processes Atmospheric Science Earth Science and Engineering, Atmospheric Physics, Imperial College London, United Kingdom University of Oxford, United Kingdom Caroline Dumoulin Ann Carine Vandaele Interior Dynamics Spectroscopy and Solar Occultation Laboratoire de Planétologie et Géodynamique Belgian Institute for Space Aeronomy, de Nantes, Belgium France Pascal Rosenblatt Emmanuel Marcq Spin Dynamics Volcanic Gas Retrievals Royal Observatory of Belgium LATMOS, Université de Versailles Saint- Brussels, Belgium Quentin, France Robbie Herrick Louis-Jerome Burtz StereoSAR Outreach and Systems Engineering Geophysical Institute, ISAE-Supaero University of Alaska, Fairbanks, United States Toulouse, France EnVision Page 1 of 43 ESA M5 proposal - downloaded from ArXiV.org Executive Summary Why are the terrestrial planets so different? Venus should be the most Earth-like of all our planetary neighbours: its size, bulk composition and distance from the Sun are very similar to those of Earth. -
Venus Voyage 2050 White Paper Wilson, Widemann Et Al
Venus Voyage 2050 White Paper Wilson, Widemann et al. August 2019 Venus: Key to understanding the evolution of terrestrial planets A response to ESA’s Call for White Papers for the Voyage 2050 long- term plan in the ESA Science Programme. ? Contact Scientist: Colin Wilson Atmospheric, Oceanic and Planetary Physics, Clarendon Laboratory, University of Oxford, UK. E-mail: [email protected] Venus Voyage 2050 White Paper Wilson, Widemann et al. August 2019 Executive summary In this Voyage 2050 White Paper, we emphasize the importance of a Venus exploration programme for the wider goal of understanding the diversity and evolution of habitable planets. Why are the terrestrial planets so different from each other? Venus, our nearest neighbour, should be the most Earth-like of all our planetary siblings. Its size, bulk composition and solar energy input are very similar to those of the Earth. Its original atmosphere was probably similar to that of early Earth, with large atmospheric abundances of carbon dioxide and water. Furthermore, the young sun’s fainter output may have permitted a liquid water ocean on the surface. While on Earth a moderate climate ensued, Venus experienced runaway greenhouse warming, which led to its current hostile climate. How and why did it all go wrong for Venus? What lessons can we learn about the life story of terrestrial planets/exoplanets in general, whether in our solar system or in others? Comparing the interior, surface and atmosphere evolution of Earth, Mars and Venus is essential to understanding what processes determined habitability of our own planet and Earth-like planets everywhere. -
Evidence of Vertical and Horizontal Motions on Venus: Maxwell Montes
EVIDENCE OF VERTICAL AND HORIZONTAL MOTIONS ON VENUS: MAXWELL MONTES V. ANSAN 1 and E VERGELY 2 l Centre National d'Etudes Spatiales, Division Instrumentation Radar, 18, avenue Edouard Be#n, 31055 Toulouse cedex, France; 2Laboratoire de Géologie Dynamique de la Terre et des planètes, Bät. 509, Université Paris-Sud, 91405 Orsay cedex, France (Received 16 February 1995) Abstract. Based on full-resolution Magellan radar images, the detailed structural analysis of central Ishtar Terra (Venus) provides new insight to the understanding of the Venusian tectonics. Ishtar Terra, centered on 65 ° N latitude and 0 ° E longitude includes a high plateau. Lakshmi Planum, surrounded by highlands, the most important being Maxwell Montes to the East. Structural analysis has been performed with classical remote-sensing methods. Folds and faults identified on radar images were reported on structural map. Their type and distfibution allowed to define the style of the crustal deformation and the context in which these structures formed. This analysis shows that Lakshmi Planum formed under a crustal stretching associated with a volcanic activity. This area then became a relatively steady platform, throughout the formation of Maxwell Montes mountain belt. Maxwell Montes is characterized by a series of NNW-SSE trending thrust faults dipping to the East, formed during a WSW-ESE horizontal shortening. In its NW quarter, the mountain belt shows a disturbed deformation controlled by pre-existing grabens and old vertical crustal fault zone. The deformation of this area is characterized by a shortening of cover above a fiat detachment zone, with a progressive accommodation to the southwest. All these tectonic structures show evidence of horizontal and vertical crustal movements on Venus, with subsidence, mountain belt raise, West regional overthrusting of this mountain belt, and regional shear zone. -
O Lunar and Planetary Institute Provided by the NASA Astrophysics Data System 710 LPSC Xxil Geologic Settings of the Venusian Channels: Komatsu, G
LPSC XXII 739 Locations and Geological Settings of the Venusian Channels. G.Komatsu, V.C.Gulick, V.R.Baker, University of Arizona, Tucson, AZ 85721; T.J.Parker, Jet Propulsion Laboratory, Pasadena, CA 91109 and University of Southern California, LA, CA 90089-0741. Magellan imagery reveals a rich variety of venusian channels. Channels were observed in the Magellan test images. The morphology of channels is described in detail by Gulick et al.[l]. The channels seen to date occur in the following four geological settings: 1. Channels associated with volcanic structures. 1) Coronae: The channels appear inside corona rims (58.3'S, 350' and 67'S, 358') and show a mor- phology similar to that of lunar rills (Fig.1). They usually originate at a collapse pit or depression. Some of the channels seem to occur near or on lava flows. Domes of about 1-5km diameter are often seen inside coronae near the channels. 2) Lava delta: The prominent lava delta at 52'-57'S, 351'-357' consists of many radar bright flows (200- 300km long, 10-30km wide). Many of these flows have superimposed channels, which exhibit darker radar response than the flows. 2. Channels occurring in the volcanic plains where volcanic structures are widely distributed. 1) Guinevere Planitia: Five narrow (1-2km wide) and sinuous channels were recognized (in the first 3 days of Magellan images) in the southeastern part (5°S100N, 330'- 340') of Guinevere Planitia, which is basically a volcanic plain (Fig.2). They generally flow east-west and seem to follow the topographic gradient down to the lower elevations of Guinevere Planitia Some channels are very long (over 1000km) and may originate from the Hengo Corona (center 2'N, 355O, 900 km diameter). -
Characterization and Assessment of the Geological Settings Of
VELI-PETRI KOSTAMA THE CROWNS, SPIDERS AND STARS OF VENUS: 2006 CHARACTERIZATION AND ASSESSMENT OF THE GEOLOGICAL SETTINGS OF VOLCANO-TECTONIC STRUCTURES ON VENUS VELI-PETRI KOSTAMA UNIVERSITY OF OULU REPORT SERIES IN PHYSICAL SCIENCES Report No. 42 (2006) ISBN 951-42-8316-3 ISBN 951-42-8317-1 (PDF) ISSN 1239-4327 THE CROWNS, SPIDERS AND STARS OF VENUS: CHARACTERIZATION AND ASSESSMENT OF THE GEOLOGICAL SETTINGS OF VOLCANO-TECTONIC STRUCTURES ON VENUS SOLAR WIND: DETECTION METHODS AND VELI-PETRI KOSTAMA LONG-TERM FLUCTUATIONS Department of Physical Sciences University of Oulu JARI VILPPOLA Finland Academic dissertation to be presented, with the permission of the Faculty of Science of the University of Oulu, for public discussion in the Auditorium TA105, Linnanmaa, on 15 December, 2006, at 12 o’clock noon. REPORT SERIES IN PHYSICAL SCIENCES Report No. 42 UNIVERSITY OF OULU OULU 2006 _ UNIVERSITY OF OULU REPORT SERIES IN PHYSICAL SCIENCES Report No. 26 (2003) ISBN 951-42-8316-3 ISSN 1239-4327 Oulu University Press Oulu 2006 Kostama, Veli-Petri The crowns, spiders and stars of Venus Department of Physical Sciences, University of Oulu, Finland Report No. 42 (2006) Abstract Venus surface has been studied extensively using SAR (synthetic aperture radar) –imagery provided by the NASA Magellan mission in 1990 - 1994. The radar images with ~98% coverage and resolution of ~100 m may be used in order to understand the global suite of surface structures, and to analyze single features and their formation processes using photogeological approaches and methods. This study recognizes and catalogues four Venusian surface structure types, the coronae, arachnoids, novae and corona-novae.