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Depth to Diameter Analysis on Small Simple Craters at the Lunar South Pole—Possible Implications for Ice Harboring. REMOTE SENSING 2022. [DOI: 10.3390/rs14030450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In this paper, we present a study comparing the depth to diameter (d/D) ratio of small simple craters (200–1000 m) of an area between −88.5° to −90° latitude at the lunar south pole containing Permanent Shadowed Regions (PSRs) versus craters without PSRs. As PSRs can reach temperatures of 110 K and are capable of harboring volatiles, especially water ice, we analyzed the relationship of depth versus diameter ratios and its possible implications for harboring water ice. Variations in the d/D ratios can also be caused by other processes such as degradation, isostatic adjustment, or differences in surface properties. The conducted d/D ratio analysis suggests that a differentiation between craters containing PSRs versus craters without PSRs occurs. Thus, a possible direct relation between d/D ratio, PSRs, and water ice harboring might exist. Our results suggest that differences in the target’s surface properties may explain the obtained results. The resulting d/D ratios of craters with PSRs can help to select target areas for future In-Situ Resource Utilization (ISRU) missions.
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Exploration of Planetary Hyperspectral Images with Unsupervised Spectral Unmixing: A Case Study of Planet Mars. REMOTE SENSING 2018. [DOI: 10.3390/rs10050737] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Constraints on the volatile distribution within Shackleton crater at the lunar south pole. Nature 2012; 486:378-81. [PMID: 22722197 DOI: 10.1038/nature11216] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Accepted: 05/04/2012] [Indexed: 11/08/2022]
Abstract
Shackleton crater is nearly coincident with the Moon's south pole. Its interior receives almost no direct sunlight and is a perennial cold trap, making Shackleton a promising candidate location in which to seek sequestered volatiles. However, previous orbital and Earth-based radar mapping and orbital optical imaging have yielded conflicting interpretations about the existence of volatiles. Here we present observations from the Lunar Orbiter Laser Altimeter on board the Lunar Reconnaissance Orbiter, revealing Shackleton to be an ancient, unusually well-preserved simple crater whose interior walls are fresher than its floor and rim. Shackleton floor deposits are nearly the same age as the rim, suggesting that little floor deposition has occurred since the crater formed more than three billion years ago. At a wavelength of 1,064 nanometres, the floor of Shackleton is brighter than the surrounding terrain and the interiors of nearby craters, but not as bright as the interior walls. The combined observations are explicable primarily by downslope movement of regolith on the walls exposing fresher underlying material. The relatively brighter crater floor is most simply explained by decreased space weathering due to shadowing, but a one-micrometre-thick layer containing about 20 per cent surficial ice is an alternative possibility.
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Sanin AB, Mitrofanov IG, Litvak ML, Malakhov A, Boynton WV, Chin G, Droege G, Evans LG, Garvin J, Golovin DV, Harshman K, McClanahan TP, Mokrousov MI, Mazarico E, Milikh G, Neumann G, Sagdeev R, Smith DE, Starr RD, Zuber MT. Testing lunar permanently shadowed regions for water ice: LEND results from LRO. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2011je003971] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Thompson TW, Ustinov EA, Heggy E. Modeling radar scattering from icy lunar regoliths at 13 cm and 4 cm wavelengths. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2009je003368] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mishchenko MI, Liu L. Electromagnetic scattering by densely packed particulate ice at radar wavelengths: exact theoretical results and remote-sensing implications. APPLIED OPTICS 2009; 48:2421-2426. [PMID: 19412198 DOI: 10.1364/ao.48.002421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We use the numerically exact superposition T-matrix method to compute electromagnetic scattering characteristics of a macroscopic volume of a discrete random medium filled with wavelength-sized spherical particles with a refractive index typical of water ice at centimeter wavelengths. Our analysis demonstrates relative strengths of various optical observables in terms of their potential remote-sensing content. In particular, it illustrates the importance of accounting for the forward-scattering interference effect in the interpretation of occultation measurements of planetary rings. We show that among the most robust indicators of the amount of multiple scattering inside a particulate medium are the cross-polarized scattered intensity, the same-helicity scattered intensity, and the circular polarization ratio. We also demonstrate that many predictions of the low-packing-density theories of radiative transfer and coherent backscattering are applicable, both qualitatively and semi-quantitatively, to densely packed media.
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Affiliation(s)
- Michael I Mishchenko
- NASA Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, USA.
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Haruyama J, Ohtake M, Matsunaga T, Morota T, Honda C, Yokota Y, Pieters CM, Hara S, Hioki K, Saiki K, Miyamoto H, Iwasaki A, Abe M, Ogawa Y, Takeda H, Shirao M, Yamaji A, Josset JL. Lack of exposed ice inside lunar south pole Shackleton Crater. Science 2008; 322:938-9. [PMID: 18948501 DOI: 10.1126/science.1164020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The inside of Shackleton Crater at the lunar south pole is permanently shadowed; it has been inferred to hold water-ice deposits. The Terrain Camera (TC), a 10-meter-resolution stereo camera onboard the Selenological and Engineering Explorer (SELENE) spacecraft, succeeded in imaging the inside of the crater, which was faintly lit by sunlight scattered from the upper inner wall near the rim. The estimated temperature of the crater floor, based on the crater shape model derived from the TC data, is less than approximately 90 kelvin, cold enough to hold water-ice. However, at the TC's spatial resolution, the derived albedo indicates that exposed relatively pure water-ice deposits are not on the crater floor. Water-ice may be disseminated and mixed with soil over a small percentage of the area or may not exist at all.
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Affiliation(s)
- Junichi Haruyama
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 229-85105, Japan
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Elphic RC, Chu P, Hahn S, James MR, Lawrence DJ, Prettyman TH, Johnson JB, Podgorney RK. Surface and downhole prospecting tools for planetary exploration: tests of neutron and gamma ray probes. ASTROBIOLOGY 2008; 8:639-652. [PMID: 18554085 DOI: 10.1089/ast.2007.0163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The ability to locate and characterize icy deposits and other hydrogenous materials on the Moon and Mars will help us understand the distribution of water and, therefore, possible habitats at Mars, and may help us locate primitive prebiotic compounds at the Moon's poles. We have developed a rover-borne neutron probe that localizes a near-surface icy deposit and provides information about its burial depth and abundance. We have also developed a borehole neutron probe to determine the stratigraphy of hydrogenous subsurface layers while operating within a drill string segment. In our field tests, we have used a neutron source to "illuminate" surrounding materials and gauge the instruments' efficacy, and we can simulate accurately the observed instrument responses using a Monte Carlo nuclear transport code (MCNPX). An active neutron source would not be needed for lunar or martian near-surface exploration: cosmic-ray interactions provide sufficient neutron flux to depths of several meters and yield better depth and abundance sensitivity than an active source. However, for deep drilling (>or=10 m depth), a source is required. We also present initial tests of a borehole gamma ray lithodensity tool and demonstrate its utility in determining soil or rock densities and composition.
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Affiliation(s)
- R C Elphic
- Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, California 94035-1000, USA.
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Campbell DB, Campbell BA, Carter LM, Margot JL, Stacy NJS. No evidence for thick deposits of ice at the lunar south pole. Nature 2006; 443:835-7. [PMID: 17051213 DOI: 10.1038/nature05167] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Accepted: 08/15/2006] [Indexed: 11/08/2022]
Abstract
Shackleton crater at the Moon's south pole has been suggested as a possible site of concentrated deposits of water ice, on the basis of modelling of bi-static radar polarization properties and interpretations of earlier Earth-based radar images. This suggestion, and parallel assumptions about other topographic cold traps, is a significant element in planning for future lunar landings. Hydrogen enhancements have been identified in the polar regions, but these data do not identify the host species or its local distribution. The earlier Earth-based radar data lack the resolution and coverage for detailed studies of the relationship between radar scattering properties, cold traps in permanently shadowed areas, and local terrain features such as the walls and ejecta of small craters. Here we present new 20-m resolution, 13-cm-wavelength radar images that show no evidence for concentrated deposits of water ice in Shackleton crater or elsewhere at the south pole. The polarization properties normally associated with reflections from icy surfaces in the Solar System were found at all the observed latitudes and are strongly correlated with the rock-strewn walls and ejecta of young craters, including the inner wall of Shackleton. There is no correlation between the polarization properties and the degree of solar illumination. If the hydrogen enhancement observed by the Lunar Prospector orbiter indicates the presence of water ice, then our data are consistent with the ice being present only as disseminated grains in the lunar regolith.
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Affiliation(s)
- Donald B Campbell
- Department of Astronomy, Cornell University, Ithaca, New York 14853, USA.
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Campbell BA, Campbell DB, Chandler JF, Hine AA, Nolan MC, Perillat PJ. Radar imaging of the lunar poles. Nature 2003; 426:137-8. [PMID: 14614491 DOI: 10.1038/426137a] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Bruce A Campbell
- Center for Earth and Planetary Studies, Smithsonian Institution, Box 37012, Washington DC 20013-7012, USA.
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