DOCSLIB.ORG

Global Tectonics of Terrestrial Planets Laurent Montesi University of Maryland

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Global Tectonics of Terrestrial Planets Laurent Montesi University of Maryland Melas Dorsa, Solis Planum, Mars (HRSC) Global Tectonics of Terrestrial Planets Laurent Montesi University of Maryland CIDER 2014 Marc WieczorekCIDER 2014 Marc WieczorekCIDER 2014 Marc WieczorekCIDER 2014 Global tectonics on Earth Strain rate map (Corné Kremeer) http://gsrm.unavco.org/ CIDER 2014 Recognizing Plate Tectonics • Rigid interior / • Divergent motion deformable boundaries • Normal faults • Linear belts of activity • Rift morphology with • Earthquakes volcanism • Volcanoes • Convergent motion • Topography • Differentiated volcanism • Faults • Accretionary wedges • Plate interior • Coherent motion • High-grade • Reconstructions metamorphism • Geodesy • Strike-slip motion • Negligible current • Horizontal offsets activity • Limited volcanism GEOL412/789A – Lecture 07 Planetary Observables Earth Mars Venus Distribution of earthquakes Soon (InSight) Not available Distribution of volcanism Yes Yes Composition Hypsometry Hypsometry Flow morphology Flow morphology Surface composition Surface composition Samples Remote sensing Faulting Visible images Radar images Topography Laser altimetry (global) Radar altimetry (global) Interferometry (local) Interferometry (local) Geodesy Not available Not available Ages Cratering (coarse) Cratering (coarse) Geological units Yes Yes Geoid Yes Yes Heat flux Soon (InSight) Not available Resources • Google Earth • Google Mars http://www.google.com/mars Native to Google Earth (also Google Moon and Google Sky) • Google Venus (under development from Scripps and Google) • ftp://topex.ucsd.edu/pub/sandwell/google_venus/Google_Venus.kmz • Careful with measuring scale: 1 km on the map is 1km on Earth, would be ~0.95km on Venus • Blue or white tint comes from Earth’s landmass vs. distribution; Ocean glimmer effect can be bothersome. • Other resources • http://planetologia.elte.hu/globes/index2.html • http://www.digitalplanets.org/ (Venus is buggy) • Other Planetary GIS • PIGWAD http://webgis.wr.usgs.gov/ • JMARS http://jmars.asu.edu/map-layer • Map-a-planet http://www.mapaplanet.org/ CIDER 2014 Extension on Venus Normal faults, Zverine Chasma CIDER 2014 Rift on Venus: Zverine Chasma CIDER 2014 How much extension? Balch crater, Devana Chasma (BetaRegio) CIDER 2014 Large-scale view (Beta Regio) CIDER 2014 Large-scale view (Beta Regio) Plume-driven uplift What does it mean for the East African Rift? CIDER 2014 Dali Chasma CIDER 2014 Corona-rich rift (Dali Chasma) CIDER 2014 Coronae Nei-Teuvez corona Mantle Plume? Delamination? CIDER 2014 Artemis Largest corona? Subduction rollback? CIDER 2014 Artemis (topography) “Prism” is a rift! CIDER 2014 Artemis Chasma … Although a weird one CIDER 2014 Ridge belt Pandrosos Dorsa CIDER 2014 Ridges and fracture belts CIDER 2014 Ridge and fracture belts Some positive, some negative relief CIDER 2014 Ridge belt vs. fracture belt Lavinia Planitia CIDER 2014 Northern highlands Fortuna Tessera Akna Montes Lakshmi planum Maxwell Montes CIDER 2014 Akna Montes Fold belt CIDER 2014 Maxwell Montes and Fortuna Tessera CIDER 2014 Tessera At least two (often more) tectonic events CIDER 2014 Ribbon tessera 1) Narrow, parallel graben 2) Orthogonal folding CIDER 2014 Ovda deformation sequence 1) Narrow, parallel graben 2) Orthogonal folding 3) Broader graben CIDER 2014 Global compression Wrinkle ridges, Guinevere Planitia CIDER 2014 Tectonic summary • Minor rifts • Globally consistent tectonic • Influence of mantle upwellings sequences • Parallel sets of ridge belts • Tessera ribbons followed by folds • Low plains followed by wrinkle • No large-scale plates ridges • Global reach of Artemis? • Climate-induced tectonics (Solomon et al., 1999) Evolution of surface temperature and stress following the eruption of a volume of lava equivalent to a global layer 500 m in thickness (Solomon et al., 1999) CIDER 2014 Mantle convection regime • 2D Mantle convection coupled with atmosphere, melting, and degassing • 4 stages: • Early stagnant lid (efficient escape) • Mobile lid removes internal heat • Stagnant lid replenishes internal heat • Episodic lid with local (?) resurfacing events • Artemis? Dali? • Timing of transitions? Armann and Tackley, 2012; Gillmann and Tackley, 2014 CIDER 2014 The global reach of Artemis? Hansen, 2010 CIDER 2014 Wrinkle ridges without interbed slip with interbed slip Wrinkle Topographic offset Backthrust Ridge Thrust Layered plain CIDER 2014 Basement Hesperia Planum Influence of buried structures CIDER 2014 Topography-derived sets Arcadia Planum CIDER 2014 Larger thrusts Amenthes Rupes CIDER 2014 Normal faults Ceraunius Fossae CIDER 2014 Rifts of Tempe Terra CIDER 2014 Tempe Terra CIDER 2014 Tharsis tectonics CIDER 2014 Tectonic centers • Missing wrinkle ridges to NW • “CF” reinterpreted as strike-slip fault (Yin, 2012) " !" ! ! Anderson et al., 2001 CIDER 2014 Elastic flexure • Extension predicted by the topography and gravity of Tharsis with an 100 km thick elastic spherical shell (Banerdt and Golombek, 2000; Golombek and Phillips, 2010) CIDER 2014 Elastic flexure • Compression predicted by the topography and gravity of Tharsis with an 100 km thick elastic spherical shell (Banerdt and Golombek, 2000; Golombek and Phillips, 2010) CIDER 2014 Valles Marineris CIDER 2014 Origin of rifts Graben widened by erosion CIDER 2014 Strike-slip faulting… CIDER 2014 Montgomery et al., 2009 GEOL412/789A – Lecture 07 Plate or landslide? • Solis Planum as a mega-landslide over a salt layer • Mechanics are problematic • Wedge mechanics imply the décollement should dip 2° to 20° over 2000 km! Montgomery et al., 2009 CIDER 2014 Basin-centered tectonics Utopia Planitia CIDER 2014 Mars summary • Limited horizontal motion • 40 km maximum extension/compression • Possibly 250 km left-lateral strike-slip at Valles Marineris • Centers of activity, mostly Tharsis • Success of flexure models implies an intact plate, limited strain • Global contraction • Modulated by regional and local stress sources • No confirmed evidence for plate tectonics • Magnetic lineations (Connerney et al., 1999): not linear, not symmetric, not along long circle • Oceanic plate to the north (Sleep 1994): preserved ancient structures inconsistent with volcanic “arc” of Tharsis; inconsistent tectonics on edge • Rollback tectonics (Yin 2012) has major timing and mechanical issues CIDER 2014 What’s up with the Earth? Estimats of Martian heat flux from flexure • Interior process? (McGovern et al., 2002) and wrinkle ridge spacing (Montési and Zuber, 2003) • Intensity of convection? • Interior layering? Laul et al., 1986 • Lithosphere process? Treiman et al., 1986 • Presence of water? • Presence of continents? • Rheology of the Half-space cooling lithosphere? • Surface process? • Erosion allows large fault offsets CIDER 2014 Localization • Structural changes (grain size, fabric) can weaken rocks. • Under what conditions are these changes efficient? Continent Oceanic Mars Venus Unresolved questions • Origin of the crust • Thick basaltic crusts: • Is there enough partial melting in the mantle? • Generation of a thick depleted lithosphere? • Heat producing elements partitioning and thermal evolution • Localization in the lithosphere? • Can the lithosphere fail as a whole? • Role of water, crustal thickness? • Metamorphic assemblages? .
Load more

Recommended publications
  • 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]
  • 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]
  • 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]
  • 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]
  • Venus' Ishtar Terra: Topographic Analysis of Maxwell, Freyja, Akna
    16th VEXAG Meeting 2018 (LPI Contrib. No. 2137) 8046.pdf Venus’ Ishtar Terra: Topographic Analysis of Maxwell, Freyja, Akna and Danu Montes. Sara Rastegar1 and 2 1 ​ Donna M. Jurdy ,​ C​ ity Colleges of Chicago, Harold Washington College, 30 E. Lake Street, Chicago, IL 60601, ​ ​ 2 [email protected], D​ epartment of Earth and Planetary Sciences, Northwestern University, 2145 Sheridan ​ ​ Rd, Evanston, IL 60208, [email protected] ​ Introduction: Venus’ mountain chains (Figure 1) Analysis: We attempt to address these questions ​ ​ ​ surround Lakshmi Planum, a 3-4 km highland, making with analysis of Magellan topographic data for up Ishtar Terra. No other mountain belts exist on quantitative comparison of Venus' four mountain Venus. Circling Ishtar Terra, Maxwell Montes, ascends chains: Maxwell, Freyja, Akna and Danu. Patterns in to over 11 km, ranking as the location of highest topography may provide clues to the dynamics forming elevation on the planet. Freyja Montes rises to over 7 these Venusian orogenic belts. From topographic km, higher than Akna Montes at about an elevation of profiles across the ec mountain chain, we then 6 km. Danu Montes, ~1.5 km over Lakshmi Planum, determine an average profile for each mountain belt. alone displays a distinctly arcuate form. Next, we correlate these averages to establish a measure of similarity between the chains and terrestrial Tectonic Enigma: The existence of the four analogs. These correlations allow construction of a venusian mountain chains has been attributed to covariance matrix, which can be diagonalized for localized downwelling - analogous to terrestrial eigenvalues, for Principal Component Analysis (PCA) subduction - in response to the proposed upwelling [4].
    [Show full text]
  • The Earth-Based Radar Search for Volcanic Activity on Venus
    52nd Lunar and Planetary Science Conference 2021 (LPI Contrib. No. 2548) 2339.pdf THE EARTH-BASED RADAR SEARCH FOR VOLCANIC ACTIVITY ON VENUS. B. A. Campbell1 and D. B. Campbell2, 1Smithsonian Institution Center for Earth and Planetary Studies, MRC 315, PO Box 37012, Washington, DC 20013-7012, [email protected]; 2Cornell University, Ithaca, NY 14853. Introduction: Venus is widely expected to have geometry comes from shifts in the latitude of the sub- ongoing volcanic activity based on its similar size to radar point, which spans the range from about 8o S Earth and likely heat budget. How lithospheric (2017) to 8o N (2015). Observations in 1988, 2012, and thickness and volcanic activity have varied over the 2020 share a similar sub-radar point latitude of ~3o S. history of the planet remains uncertain. While tessera Coverage of higher northern and southern latitudes may highlands locally represent a period of thinner be obtained during favorable conjunctions (Fig. 1), but lithosphere and strong deformation, there is no current the shift in incidence angle must be recognized in means to determine whether they formed synchronously analysis of surface features over time. The 2012 data on hemispheric scales. Understanding the degree to were collected in an Arecibo-GBT bistatic geometry which mantle plumes currently thin and uplift the crust that led to poorer isolation between the hemispheres. to create deformation and effusive eruptions will better inform our understanding of the “global” versus Searching for Change. Ideally, surface change “localized” timing of heat transport. Ground-based detection could be achieved by co-registering and radar mapping of one hemisphere of Venus over the past differencing any pair of radar maps.
    [Show full text]
  • 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.
    [Show full text]
  • Final Report Venus Exploration Targets Workshop May 19–21
    Final Report Venus Exploration Targets Workshop May 19–21, 2014, Lunar and Planetary Institute, Houston, TX Conveners: Virgil (Buck) Sharpton, Larry Esposito, Christophe Sotin Breakout Group Leads Science from the Surface Larry Esposito, Univ. Colorado Science from the Atmosphere Kevin McGouldrick, Univ. Colorado Science from Orbit Lori Glaze, GSFC Science Organizing Committee: Ben Bussey, Martha Gilmore, Lori Glaze, Robert Herrick, Stephanie Johnston, Christopher Lee, Kevin McGouldrick Vision: The intent of this “living” document is to identify scientifically important Venus targets, as the knowledge base for this planet progresses, and to develop a target database (i.e., scientific significance, priority, description, coordinates, etc.) that could serve as reference for future missions to Venus. This document will be posted in the VEXAG website (http://www.lpi.usra.edu/vexag/), and it will be revised after the completion of each Venus Exploration Targets Workshop. The point of contact for this document is the current VEXAG Chair listed at ABOUT US on the VEXAG website. Venus Exploration Targets Workshop Report 1 Contents Overview ....................................................................................................................................................... 2 1. Science on the Surface .............................................................................................................................. 3 2. Science within the Atmosphere ...............................................................................................................
    [Show full text]
  • Vénus Les Transits De Vénus L’Exploration De Vénus Par Les Sondes Iconographie, Photos Et Additifs
    VVÉÉNUSNUS Introduction - Généralités Les caractéristiques de Vénus Les transits de Vénus L’exploration de Vénus par les sondes Iconographie, photos et additifs GAP 47 • Olivier Sabbagh • Février 2015 Vénus I Introduction – Généralités Vénus est la deuxième des huit planètes du Système solaire en partant du Soleil, et la sixième par masse ou par taille décroissantes. La planète Vénus a été baptisée du nom de la déesse Vénus de la mythologie romaine. Symbolisme La planète Vénus doit son nom à la déesse de l'amour et de la beauté dans la mythologie romaine, Vénus, qui a pour équivalent Aphrodite dans la mythologie grecque. Cythère étant une épiclèse homérique d'Aphrodite, l'adjectif « cythérien » ou « cythéréen » est parfois utilisé en astronomie (notamment dans astéroïde cythérocroiseur) ou en science-fiction (les Cythériens, une race de Star Trek). Par extension, on parle d'un Vénus à propos d'une très belle femme; de manière générale, il existe en français un lexique très développé mêlant Vénus au thème de l'amour ou du plaisir charnel. L'adjectif « vénusien » a remplacé « vénérien » qui a une connotation moderne péjorative, d'origine médicale. Les cultures chinoise, coréenne, japonaise et vietnamienne désignent Vénus sous le nom d'« étoile d'or », et utilisent les mêmes caractères (jīnxīng en hanyu, pinyin en hiragana, kinsei en romaji, geumseong en hangeul), selon la « théorie » des cinq éléments. Vénus était connue des civilisations mésoaméricaines; elle occupait une place importante dans leur conception du cosmos et du temps. Les Nahuas l'assimilaient au dieu Quetzalcoatl, et, plus précisément, à Tlahuizcalpantecuhtli (« étoile du matin »), dans sa phase ascendante et à Xolotl (« étoile du soir »), dans sa phase descendante.
    [Show full text]
  • Walter S. Kiefer
    Walter S. Kiefer Lunar and Planetary Institute (281) 486-2110 (Office) 3600 Bay Area Blvd. [email protected] Houston, TX 77058 https://www.lpi.usra.edu/science/staff/kiefer/ Education Ph.D., Planetary Science and Geophysics, California Institute of Technology, 1990 Thesis: Models for the Formation of Highland Regions on Venus M.S., Planetary Science, California Institute of Technology, 1986 B.S., Physics and Astronomy, Texas Christian University, 1984, summa cum laude Honors Thesis: Fourier Transform Infrared Spectroscopy of Clay Minerals and Tar Sands Professional Experience Lunar and Planetary Institute, 1993-present Senior Staff Scientist, 2017-present Manager for Geophysics and Small Bodies Group, 2019-present Staff Scientist, 1997-2016 Research Scientist, 1993-1997 National Research Council Research Associate, Goddard Space Flight Center, 1990-1993 Graduate Research Assistant and Graduate Teaching Assistant, Division of Geological and Planetary Sciences, California Institute of Technology, 1984-1990 Spacecraft Mission and Instrument Development Experience Gravity Recovery and Interior Laboratory (GRAIL) mission Guest Scientist, 2012-2016 DAVINCI+: Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging+ mission proposal Co-I (NASA Discovery program Phase A Concept Study, 2020-2021) NASA representative on European Space Agency’s Science Study Team for the EnVision mission concept Phase A study (Venus remote sensing orbiter), 2018-2021 NASA Venus Landed Platform Science Working Group, 2018-2020 Seismic Atmospheric
    [Show full text]
  • Refining the Mahuea Tholus (V-49) Quadrangle, Venus
    3rd Planetary Data Workshop 2017 (LPI Contrib. No. 1986) 7118.pdf REFINING THE MAHUEA THOLUS (V-49) QUADRANGLE, VENUS. N.P. Lang1 , K. Rogers1, M. Covley1, C. Nypaver1, E. Baker1, and B.J. Thomson2; 1Department of Geology, Mercyhurst University, Erie, PA 16546 ([email protected]), 2Department of Earth and Planetary Sciences, University of Tennessee – Knoxville, Knoxville, TN 37996 ([email protected]). Introduction: The Mahuea Tholus quadrangle (V- divided by major corona-associated flow fields that 49; Figure 1) extends from 25° to 50° S to 150° to continue into V-49. These flows are identified as the 180° E and encompasses >7×106 km2 of the Venusian central points of volcanism within the rift zone and surface. Moving clockwise from due north, the Ma- were used to help in determining stratigraphy. There huea Tholus quadrangle is bounded by the Diana are four coronae present within the Diana-Dali Chasma Chasma, Thetis Regio, Artemis Chasma, Henie, Bar- in the map area: Agraulos, Annapuma, Colijnsplaat, rymore, Isabella, and Stanton quadrangles; together and Mayauel. Flow material from coronae outside of with Stanton, Mahuea Tholus is one of two remaining V-49 extend into this part of the map area adding fur- quadrangles to be geologically mapped in this part of ther complexity to the stratigraphy of this region. Tim- Venus. Here we report on our continued mapping of ing of fracture formation appears non-uniform with this quadrangle. Specifically, over the past year we NE-trending suites of fractures cross-cutting E-W have focused on refining the geology of the northern trending fracture suites; this suggests different parts of third of V-49 and mapping the distrubiton of small the rift zone were active at different times (stress re- volcanic edifices.
    [Show full text]
  • 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.
    [Show full text]