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  • 1
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    Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging (2010)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transmits a single sense of circular polarization, and both senses of circular polarization are received, which allows for the construction of the Stokes polarization vector. From the Stokes vector, daughter products such as the circular polarization ratio, the degree of linear polarization, and linear polarization angle are obtained. Recent polarimetric imaging using Arecibo has included Venus and the Moon. These observations can be compared to radar data for terrestrial surfaces to better understand surface physical properties and regional geologic evolution. For example, polarimetric radar studies of volcanic settings on Venus, the Moon and Earth display some similarities, but also illustrate a variety of different emplacement and erosion mechanisms. Polarimetric radar data provides important information about surface properties beyond what can be obtained from single-polarization radar. Future observations using polarimetric synthetic aperture radar will provide information on roughness, composition and stratigraphy that will support a broader interpretation of surface evolution.
    Keywords: Lunar and Planetary Science and Exploration
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  • 2
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    Orbital Imaging Radar and the Search for Water on Mars (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The surface of Mars has been modified by a range of geologic processes, and many regions are mantled by varying depths of wind-blown dust, volcanic ash, and fluvially deposited or other water-lain sediments. We are proposing an orbital mission carrying a synthetic aperture radar (SAR) that can penetrate a significant depth of overlying material to reveal the detailed geomorphology as it relates to the changing fluvial, eolian, volcanic, and cratering history of Mars. Moreover, the data to be returned are of direct relevance to the search for past and present occurrences of liquid water, life, changing martian climate, and geologic history (e.g., origin of the northern plains, mechanisms for past and possible present valley formation, and genesis of widespread mantling deposits), the validation of potential landing sites for rover safety, and evaluation of sub-surface accessibility for drilling.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Conference on the Geophysical Detection of Subsurface Water on Mars; 16-17; LPI-Contrib-1095
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  • 3
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    Searching for Surficial Deposits on Venus Using Multi-Polarization Radar (2003)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: Introduction. The Magellan spacecraft returned hundreds of images of craters, radardark halos, and wind features on Venus. It is clear that surficial layers are associated with some of these features; for example, 59 of the craters have parabolic shaped deposits that are thought to be a few centimeters to a meter in thickness. Magellan also revealed about 400 radar dark "splotches" that may be places where a smooth rubble layer was formed when the shock wave from an impactor hit the surface and crushed the rock. Two dune fields and several areas of microdunes were identified in Magellan data, as well a few thousand windstreaks, so it is clear that dust is transported and redeposited by wind. Thin surficial layers that are not clearly visible in the Magellan imagery may be present in other regions as well. In fact, many surfaces on Venus that were imaged by Magellan SAR may look much different when viewed at optical wavelengths, since radar waves penetrate surface layers and show details of the underlying terrain. A good example is the L-Band (24 cm wavelength) shuttle imaging radar (SIRA) observations by McKauley et al. who detected buried river valleys in the Arbain Desert in southern Egypt.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXIV; LPI-Contrib-1156
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  • 4
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    Pyroclastic Flow Deposits on Venus as Indicators of Renewed Magmatic Activity (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Radar-bright deposits on Venus that have diffuse margins suggest eruptions that distribute debris over large areas due to ground-hugging flows from plume collapse. We examine deposits in Eastern Eistla, Western Eistla, Phoebe, and Dione Regiones using Magellan data and Earth-based radar maps. The radar-bright units have no marginal lobes or other features consistent with viscous flow. Their morphology, radar echo strength, polarization properties, and microwave emissivity are consistent with mantling deposits comprised of few-cm or larger clasts. This debris traveled downhill up to 100 km on modest slopes, and blanketed lava flows and tectonic features to depths of tens of cm to a few meters over areas up to 40x10(exp 3) sq km. There is evidence for ongoing removal and exhumation of previously buried terrain. A newly identified occurrence is associated with a ridge belt south of Ushas Mons. We also note radar-bright streaks of coarse material west of Rona Chasma that reflect the last traces of a deposit mobilized by winds from the formation of Mirabeau crater. If the radar-bright units originate by collapse of eruption columns, with coarse fragmental material entrained and fluidized by hot gases, then their extent suggests large erupted volatile (CO2 or H2O) amounts. We propose that these deposits reflect the early stage of renewed magmatic activity, with volatile-rich, disrupted magma escaping through vents in fractured regions of the upper crust. Rapidly eroding under Venus surface conditions, or buried by subsequent eruptions, these markers of recently renewed activity have disappeared from older regions.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN44529 , Journal of Geophysical Research: Planets (ISSN 2169-9097) (e-ISSN 2169-9100); 122; 7; 1580-1596
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  • 5
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    Physical Properties of Volcanic Deposits on Venus from Radar Polarimetry (2005)
    In:  CASI
    Details
    Publication Date: 2019-08-15
    Description: Studies of the morphology and radar properties of volcanic deposits can aid in understanding their differences and formation. On Venus, volcanoes range in size from large highland edifices, such as Theia Mons, to small shields and domes which are often found in groups of tens to hundreds. In plains regions, windstreaks are sometimes found near shield fields, suggesting that there may be fine grained deposits associated with the volcanoes. Previous studies of Bell Regio suggest the presence of fine-grained material in a low dielectric constant triangular shaped region on the flank of Tepev Mons, which may be crater ejecta or a pyroclastic deposit spread westward by wind. The eastern caldera on Tepev Mons shows a steep trend in backscattered power with incidence angle and has high RMS-slopes, implying a finegrained covering such as ash. Radar waves can easily penetrate smooth mantling layers such as ash and aeolian deposits. If a radar system can measure two orthogonal polarizations, it is possible to detect subsurface scattering and infer the presence of surficial deposits. The Magellan spacecraft could only measure one polarization and was therefore not able to fully characterize the polarization state of the radar echoes. We compare Arecibo dual-polarization data for Venus to Magellan images and emissivity data to investigate the physical properties of volcanic deposits.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXVI, Part 3; LPI-Contrib-1234-Pt-3
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  • 6
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    Pyroclastic Deposits on Venus as Indicators of the Youngest Volcanism (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: While most of the surface of Venus formed by effusive volcanic processes, deposits suggesting eruption styles that distribute airfall debris over large areas, or ground-hugging flows from plume collapse, are not common. Prior work notes radar-bright units with diffuse margins, generally consistent with a plume collapse emplacement model, in Eistla Regio, Dione Regio, and near Sappho Patera. We examine these deposits, and map additional occurrences, using Magellan data and Earth-based polarimetric radar maps from 1988, 2012, and 2015 observations.
    Keywords: Lunar and Planetary Science and Exploration
    Type: GSFC-E-DAA-TN39446 , Lunar and Planetary Science Conference; Mar 20, 2017 - Mar 24, 2017; The Woodlands, TX; United States
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  • 7
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    Parent volatiles in comet 9P/Tempel 1: before and after impact (2005)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We quantified eight parent volatiles (H2O, C2H6, HCN, CO, CH3OH, H2CO, C2H2, and CH4) in the Jupiter-family comet Tempel 1 using high-dispersion infrared spectroscopy in the wavelength range 2.8 to 5.0 micrometers. The abundance ratio for ethane was significantly higher after impact, whereas those for methanol and hydrogen cyanide were unchanged. The abundance ratios in the ejecta are similar to those for most Oort cloud comets, but methanol and acetylene are lower in Tempel 1 by a factor of about 2. These results suggest that the volatile ices in Tempel 1 and in most Oort cloud comets originated in a common region of the protoplanetary disk.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Science (ISSN 0036-8075); Volume 310; 5746; 270-4
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  • 8
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    Curiosity at Gale Crater, Mars: Characterization and Analysis of the Rocknest Sand Shadow (2013)
    In:  CASI
    Details
    Publication Date: 2014-11-22
    Description: The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MER) Spirit and Opportunity. The fraction of sand 〈150 micron in size contains approx. 55% crystalline material consistent with a basaltic heritage, and approx. 45% X-ray amorphous material. The amorphous component of Rocknest is Fe-rich and Si-poor, and is the host of the volatiles (H2O, O2, SO2, CO2, and Cl) detected by the Surface Analysis at Mars (SAM) instrument and of the fine-grained nanophase oxide (npOx) component first described from basaltic soils analyzed by MER. The similarity between soils and aeolian materials analyzed at Gusev crater, Meridiani Planum and Gale crater implies locally sourced, globally similar basaltic materials, or globally and regionally sourced basaltic components deposited locally at all three locations.
    Keywords: Lunar and Planetary Science and Exploration
    Type: ARC-E-DAA-TN11260
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  • 9
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    Probing the Martian Subsurface with Synthetic Aperture Radar (2005)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Many regions of the martian surface are covered by fine-grained materials emplaced by volcanic, fluvial, or aeolian processes. These mantling deposits likely hide ancient channel systems (particularly at smaller scale lengths) and volcanic, impact, glacial, or shoreline features. Synthetic aperture radar (SAR) offers the capability to probe meters below the surface, with imaging resolution in the 10 s of m range, to reveal the buried terrain and enhance our understanding of Mars geologic and climate history. This presentation focuses on the practical applications of a Mars orbital SAR, methods for polarimetric and interferometric radar studies, and examples of such techniques for Mars-analog sites on the Moon and Earth.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Workshop on Radar Investigations of Planetary and Terrestrial Environments; 25-26; LPI-Contrib-1231
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  • 10
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    More New Names for the Features on Venus: A Review of the 1999 Progress (2000)
    In:  Other Sources
    Details
    Publication Date: 2017-10-02
    Description: Sixty-five features of 13 different types were named on Venus in 1999. Eleven of the names are in the Northern hemisphere, and 54 are in Southern hemisphere to support the NASA program of Venus geologic mapping at 1:5,000,000 scale after the Magellan Synthetic Aperture Radar (SAR) image data.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXI; LPI-Contrib-1000
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