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Hansen VL, López I. Geologic Map of Aphrodite Map Area (AMA; I-2476), Venus. EARTH AND SPACE SCIENCE (HOBOKEN, N.J.) 2020; 7:e2019EA001066. [PMID: 33134435 PMCID: PMC7583386 DOI: 10.1029/2019ea001066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2019] [Revised: 06/08/2020] [Accepted: 06/13/2020] [Indexed: 06/11/2023]
Abstract
We present a 1:10-M-scale geologic map of the Aphrodite Map Area (AMA) of Venus (0°N-57°S/60-80°E). Geologic mapping employed NASA Magellan synthetic aperture radar and altimetry data. The AMA geologic map, with detailed structural elements and geologic units covering over one eighth of Venus' surface, affords an important and unique perspective to test models of global-scale geologic processes through time. Geologic relations record a history inconsistent with global catastrophic resurfacing. The AMA displays a regional coherence of preserved geologic patterns that record three sequential geologic eras: the ancient era, the Artemis superstructure era, and the youngest fracture zone era. The ancient era and Artemis superstructure, with a footprint covering more than 25% of the surface, are recorded in the Niobe Map Area to the north. The latter two eras likely overlap in time. The fracture zone domain, part of a globally extensive province, marks the most spatially focused tectonomagmatic domain within the AMA. Impact craters are both cut by and overprint fracture zone structures. Twelve percent of AMA impact craters that occur within the fracture zone domain predate or formed during fracture zone development. This observation indicates the relative youth of the fracture zone era and is consistent with the possibility that this domain remains geologically active. The AMA records a rich geologic history of large tract of the surface of Venus and provides an important framework to formulate new working hypotheses of Venus evolution and contribute to planning future studies of the surface of planets.
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Affiliation(s)
- V. L. Hansen
- Department of Earth and Environmental SciencesUniversity of Minnesota, DuluthDuluthMNUSA
| | - I. López
- Department of Biology and Geology, Physics and Inorganic Chemistry, Área de GeologíaUniversidad Rey Juan CarlosMóstoles, MadridSpain
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Collins GS, Patel N, Davison TM, Rae ASP, Morgan JV, Gulick SPS. A steeply-inclined trajectory for the Chicxulub impact. Nat Commun 2020; 11:1480. [PMID: 32457325 PMCID: PMC7251121 DOI: 10.1038/s41467-020-15269-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/27/2020] [Indexed: 11/09/2022] Open
Abstract
The environmental severity of large impacts on Earth is influenced by their impact trajectory. Impact direction and angle to the target plane affect the volume and depth of origin of vaporized target, as well as the trajectories of ejected material. The asteroid impact that formed the 66 Ma Chicxulub crater had a profound and catastrophic effect on Earth's environment, but the impact trajectory is debated. Here we show that impact angle and direction can be diagnosed by asymmetries in the subsurface structure of the Chicxulub crater. Comparison of 3D numerical simulations of Chicxulub-scale impacts with geophysical observations suggests that the Chicxulub crater was formed by a steeply-inclined (45-60° to horizontal) impact from the northeast; several lines of evidence rule out a low angle (<30°) impact. A steeply-inclined impact produces a nearly symmetric distribution of ejected rock and releases more climate-changing gases per impactor mass than either a very shallow or near-vertical impact.
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Affiliation(s)
- G S Collins
- Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK.
| | - N Patel
- Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK
| | - T M Davison
- Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK
| | - A S P Rae
- Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK.,Institute of Geology, University of Freiburg, Freiburg, 79104, Germany
| | - J V Morgan
- Department Earth Science and Engineering, Imperial College London, London, SW7 2AZ, UK
| | - S P S Gulick
- Institute for Geophysics and Department of Geological Sciences, University of Texas at Austin, Austin, TX, 78758, USA
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Kurosawa K, Genda H, Hyodo R, Yamagishi A, Mikouchi T, Niihara T, Matsuyama S, Fujita K. Assessment of the probability of microbial contamination for sample return from Martian moons II: The fate of microbes on Martian moons. LIFE SCIENCES IN SPACE RESEARCH 2019; 23:85-100. [PMID: 31791609 DOI: 10.1016/j.lssr.2019.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 06/27/2019] [Accepted: 07/10/2019] [Indexed: 05/26/2023]
Abstract
This paper presents a case study of microbe transportation in the Mars-satellites system. We examined the spatial distribution of potential impact-transported microbes on the Martian moons using impact physics by following a companion study (Fujita et al., in this issue). We used sterilization data from the precede studies (Patel et al., 2018; Summers, 2017). We considered that the microbes came mainly from the Zunil crater on Mars, which was formed during 1.0-0.1 Ma. We found that 70-80% of the microbes are likely to be dispersed all over the moon surface and are rapidly sterilized due to solar and galactic cosmic radiation except for those microbes within a thick ejecta deposit produced by natural meteoroids. The other 20-30% might be shielded from radiation by thick regolith layers that formed at collapsed layers in craters produced by Mars rock impacts. The total number of potentially surviving microbes at the thick ejecta deposits is estimated to be 3-4 orders of magnitude lower than at the Mars rock craters. The microbe concentration is irregular in the horizontal direction due to Mars rock bombardment and is largely depth-dependent due to the radiation sterilization. The surviving fraction of transported microbes would be only ∼1 ppm on Phobos and ∼100 ppm on Deimos, suggesting that the transport processes and radiation severely affect microbe survival. The microbe sampling probability from the Martian moons was also investigatesd. We suggest that sample return missions from the Martian moons are classified into Unrestricted Earth-Return missions for 30 g samples and 10 cm depth sampling, even in our conservative scenario. We also conducted a full statistical analysis pertaining to sampling the regolith of Phobos to include the effects of uncertainties in input parameters on the sampling probability. The most likely probability of microbial contamination for return samples is estimated to be two orders of magnitude lower than the 10-6 criterion defined by the planetary protection policy of the Committee on Space Research (COSPAR).
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Affiliation(s)
- Kosuke Kurosawa
- Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Narashino, Tsudanuma, Chiba 275-0016, Japan.
| | - Hidenori Genda
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Ryuki Hyodo
- Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Akihiko Yamagishi
- Department of Applied Life Sciences, School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, 1432-1, Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Takashi Mikouchi
- The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Takafumi Niihara
- Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Shingo Matsuyama
- Aeronautical Technology Directorate, Japan Aerospace Exploration Agency, 7-44-1, Jindaijihigasi-machi, Chofu, Tokyo 182-8522, Japan
| | - Kazuhisa Fujita
- Institute of Space and Astronomical Science, Japan Aerospace Exploration Agency, 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210, Japan
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Origin and implications of non-radial Imbrium Sculpture on the Moon. Nature 2016; 535:391-4. [PMID: 27443741 DOI: 10.1038/nature18278] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 04/18/2016] [Indexed: 11/08/2022]
Abstract
Rimmed grooves, lineations and elongate craters around Mare Imbrium shape much of the nearside Moon. This pattern was coined the Imbrium Sculpture, and it was originally argued that it must have been formed by a giant oblique (~30°) impact, a conclusion echoed by later studies. Some investigators, however, noticed that many elements of the Imbrium Sculpture are not radial to Imbrium, thereby implicating an endogenic or structural origin. Here we use these non-radial trends to conclude that the Imbrium impactor was a proto-planet (half the diameter of Vesta), once part of a population of large proto-planets in the asteroid belt. Such independent constraints on the sizes of the Imbrium and other basin-forming impactors markedly increase estimates for the mass in the asteroid belt before depletion caused by the orbital migration of Jupiter and Saturn. Moreover, laboratory impact experiments, shock physics codes and the groove widths indicate that multiple fragments (up to 2% of the initial diameter) from each oblique basin-forming impactor, such as the one that formed Imbrium, should have survived planetary collisions and contributed to the heavy impact bombardment between 4.3 and 3.8 billion years ago.
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Kurosawa K, Sugita S, Ishibashi K, Hasegawa S, Sekine Y, Ogawa NO, Kadono T, Ohno S, Ohkouchi N, Nagaoka Y, Matsui T. Hydrogen cyanide production due to mid-size impacts in a redox-neutral N2-rich atmosphere. ORIGINS LIFE EVOL B 2013; 43:221-45. [PMID: 23877440 DOI: 10.1007/s11084-013-9339-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2012] [Accepted: 06/16/2013] [Indexed: 11/28/2022]
Abstract
Cyanide compounds are amongst the most important molecules of the origin of life. Here, we demonstrate the importance of mid-size (0.1-1 km in diameter) hence frequent meteoritic impacts to the cyanide inventory on the early Earth. Subsequent aerodynamic ablation and chemical reactions with the ambient atmosphere after oblique impacts were investigated by both impact and laser experiments. A polycarbonate projectile and graphite were used as laboratory analogs of meteoritic organic matter. Spectroscopic observations of impact-generated ablation vapors show that laser irradiation to graphite within an N2-rich gas can produce a thermodynamic environment similar to that produced by oblique impacts. Thus, laser ablation was used to investigate the final chemical products after this aerodynamic process. We found that a significant fraction (>0.1 mol%) of the vaporized carbon is converted to HCN and cyanide condensates, even when the ambient gas contains as much as a few hundred mbar of CO2. As such, the column density of cyanides after carbon-rich meteoritic impacts with diameters of 600 m would reach ~10 mol/m(2) over ~10(2) km(2) under early Earth conditions. Such a temporally and spatially concentrated supply of cyanides may have played an important role in the origin of life.
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Affiliation(s)
- Kosuke Kurosawa
- Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba, 275-0016, Japan.
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Herrick RR, Rumpf ME. Postimpact modification by volcanic or tectonic processes as the rule, not the exception, for Venusian craters. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003722] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Firestone RB, West A, Kennett JP, Becker L, Bunch TE, Revay ZS, Schultz PH, Belgya T, Kennett DJ, Erlandson JM, Dickenson OJ, Goodyear AC, Harris RS, Howard GA, Kloosterman JB, Lechler P, Mayewski PA, Montgomery J, Poreda R, Darrah T, Hee SSQ, Smith AR, Stich A, Topping W, Wittke JH, Wolbach WS. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proc Natl Acad Sci U S A 2007; 104:16016-21. [PMID: 17901202 PMCID: PMC1994902 DOI: 10.1073/pnas.0706977104] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A carbon-rich black layer, dating to approximately 12.9 ka, has been previously identified at approximately 50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at approximately equal 12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at approximately 12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.
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Affiliation(s)
- R B Firestone
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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Basilevsky AT, Head JW. Impact craters on regional plains on Venus: Age relations with wrinkle ridges and implications for the geological evolution of Venus. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002473] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bondarenko NV, Kreslavsky MA, Head JW. North-south roughness anisotropy on Venus from the Magellan Radar Altimeter: Correlation with geology. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002599] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Zheng XJ, Wang ZT, Qiu ZG. Impact craters in loose granular media. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2004; 13:321-324. [PMID: 15103525 DOI: 10.1140/epje/i2004-10002-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The craters formed by the impact of steel balls with a loose sand bed are experimentally studied. Both crater size and morphology depend strongly on the impact angle. Two scaling laws, corresponding to length and width, respectively, are proposed.
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Affiliation(s)
- X-J Zheng
- Department of Mechanics, Lanzhou University, 730000, Lanzhou, PRC
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Basilevsky AT. Impact crater air fall deposits on the surface of Venus: Areal distribution, estimated thickness, recognition in surface panoramas, and implications for provenance of sampled surface materials. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004je002307] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Bondarenko NV. Radar-dark impact crater–related parabolas on Venus: Characterization of deposits with Magellan emissivity data. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004je002256] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sugita S. Interactions between impact-induced vapor clouds and the ambient atmosphere: 2. Theoretical modeling. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je001960] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Barlow NG. Martian impact crater ejecta morphologies as indicators of the distribution of subsurface volatiles. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je002036] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Sugita S. Interactions between impact-induced vapor clouds and the ambient atmosphere: 1. Spectroscopic observations using diatomic molecular emission. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je001959] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Anderson JLB. Asymmetry of ejecta flow during oblique impacts using three-dimensional particle image velocimetry. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2003je002075] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Application of three-component PIV to the measurement of hypervelocity impact ejecta. J Vis (Tokyo) 2002. [DOI: 10.1007/bf03182331] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Wieczorek MA, Zuber MT. A Serenitatis origin for the Imbrian grooves and South Pole-Aitken thorium anomaly. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001384] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ivanov MA, Head JW. Geology of Venus: Mapping of a global geotraverse at 30°N latitude. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001265] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Herrick RR, Sharpton VL. Implications from stereo-derived topography of Venusian impact craters. ACTA ACUST UNITED AC 2000. [DOI: 10.1029/1999je001225] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Pierazzo E, Melosh HJ. Understanding oblique impacts from experiments, observations, and modeling. ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES 2000; 28:141-167. [PMID: 11583040 DOI: 10.1146/annurev.earth.28.1.141] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Natural impacts in which the projectile strikes the target vertically are virtually nonexistent. Nevertheless, our inherent drive to simplify nature often causes us to suppose most impacts are nearly vertical. Recent theoretical, observational, and experimental work is improving this situation, but even with the current wealth of studies on impact cratering, the effect of impact angle on the final crater is not well understood. Although craters' rims may appear circular down to low impact angles, the distribution of ejecta around the crater is more sensitive to the angle of impact and currently serves as the best guide to obliquity of impacts. Experimental studies established that crater dimensions depend only on the vertical component of the impact velocity. The shock wave generated by the impact weakens with decreasing impact angle. As a result, melting and vaporization depend on impact angle; however, these processes do not seem to depend on the vertical component of the velocity alone. Finally, obliquity influences the fate of the projectile: in particular, the amount and velocity of ricochet are a strong function of impact angle.
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Affiliation(s)
- E Pierazzo
- Lunar and Planetary Lab., University of Arizona, Tucson, 84721, USA.
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Barnouin-Jha OS, Schultz PH, Lever JH. Investigating the interactions between an atmosphere and an ejecta curtain: 2. Numerical experiments. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1999je001027] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Collins GC, Head JW, Basilevsky AT, Ivanov MA. Evidence for rapid regional plains emplacement on Venus from the population of volcanically embayed impact craters. ACTA ACUST UNITED AC 1999. [DOI: 10.1029/1999je001041] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Barnouin-Jha OS, Schultz PH. Lobateness of impact ejecta deposits from atmospheric interactions. ACTA ACUST UNITED AC 1998. [DOI: 10.1029/98je02025] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Gilmore MS, Ivanov MA, Head JW, Basilevsky AT. Duration of tessera deformation on Venus. ACTA ACUST UNITED AC 1997. [DOI: 10.1029/97je00965] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Barnouin-Jha OS, Schultz PH. Ejecta entrainment by impact-generated ring vortices: Theory and experiments. ACTA ACUST UNITED AC 1996. [DOI: 10.1029/96je01949] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Greeley R, Schubert G, Limonadi D, Bender KC, Newman WI, Thomas PE, Weitz CM, Wall SD. Wind streaks on venus: clues to atmospheric circulation. Science 1994; 263:358-61. [PMID: 17769799 DOI: 10.1126/science.263.5145.358] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Magellan images reveal surface features on Venus attributed to wind processes. Sand dunes, wind-sculpted hills, and more than 5830 wind streaks have been identified. The streaks serve as local "wind vanes," representing wind direction at the time of streak formation and allowing the first global mapping of near-surface wind patterns on Venus. Wind streaks are oriented both toward the equator and toward the west. When streaks associated with local transient events, such as impact cratering, are deleted, the westward component is mostly lost but the equatorward component remains. This pattern is consistent with a Hadley circulation of the lower atmosphere.
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Campbell BA, Rogers PG. Bell Regio, Venus: Integration of remote sensing data and terrestrial analogs for geologic analysis. ACTA ACUST UNITED AC 1994. [DOI: 10.1029/94je01862] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Chadwick DJ, Schaber GG. Impact crater outflows on Venus: Morphology and emplacement mechanisms. ACTA ACUST UNITED AC 1993. [DOI: 10.1029/93je02605] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Campbell DB, Stacy NJS, Newman WI, Arvidson RE, Jones EM, Musser GS, Roper AY, Schaller C. Magellan observations of extended impact crater related features on the surface of Venus. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je01634] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Phillips RJ, Raubertas RF, Arvidson RE, Sarkar IC, Herrick RR, Izenberg N, Grimm RE. Impact craters and Venus resurfacing history. ACTA ACUST UNITED AC 1992. [DOI: 10.1029/92je01696] [Citation(s) in RCA: 261] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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