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An Innovative Synthetic Aperture Radar Design Method for Lunar Water Ice Exploration. REMOTE SENSING 2022. [DOI: 10.3390/rs14092148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Owing to the Moon’s rough surface, there is a growing controversy over the conclusion that water ice exists in the lunar permanently shadowed regions (PSRs) with a high circular polarization ratio (CPR). To further detect water ice on the Moon, an innovative design method for spaceborne synthetic aperture radar (SAR) system is proposed, to obtain radar data that can be used to distinguish water ice from lunar regolith with a small difference in the dielectric constants. According to Campbell’s dielectric constant model and the requirement that SAR radiometric resolution is smaller than the contrast of targets in images, a newly defined SAR system function involved in the method is presented to evaluate the influence of some system parameters on the water ice detection capability of SAR. In addition, several simulation experiments are performed, and the results demonstrate that the presented SAR design method may be helpful for lunar water ice exploration.
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Deutsch AN, Head JW, Neumann GA. Age constraints of Mercury's polar deposits suggest recent delivery of ice. EARTH AND PLANETARY SCIENCE LETTERS 2019; 520:26-33. [PMID: 32454531 PMCID: PMC7243170 DOI: 10.1016/j.epsl.2019.05.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Surface ice at the poles of Mercury appears as several-m-thick deposits that are composed of nearly pure water. We provide new age estimates of Mercury's polar deposits from combined analyses of Poisson statistics and direct observations of crater densities within permanently shadowed, radar-bright regions imaged by the MESSENGER spacecraft. These age estimates suggest that ice was delivered to Mercury within the last ~150 Myr. A single, recent impactor is one possible delivery mechanism that is consistent with our new age constraints, as well as the observed distinct reflectance boundaries of the polar deposits and the relative purity of the ice, as suggested by the Earth-based radar observations. In contrast to ice on Mercury, observations of the lunar poles are suggestive of a highly patchy distribution of surface frost. The patchiness of lunar polar deposits is consistent with long exposure times to the space weathering environment. Given enough time, the polar deposits on Mercury may age into a more heterogeneous spatial distribution, similar to that on the Moon.
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Affiliation(s)
- Ariel N. Deutsch
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - James W. Head
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912, USA
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Anand M, Tartèse R, Barnes JJ. Understanding the origin and evolution of water in the Moon through lunar sample studies. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130254. [PMID: 25114308 PMCID: PMC4128269 DOI: 10.1098/rsta.2013.0254] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior. This has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation. While these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin, distribution and evolution of water in the lunar interior. Another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the Moon through instruments flown on a number of orbiting spacecraft missions. Considered together, sample-based studies and those from orbit strongly suggest that the Moon is not an anhydrous planetary body, as previously believed. New observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface. Furthermore, an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source(s) involved in giving rise to the lunar water inventory. A number of sources are likely to have contributed to the water inventory of the Moon ranging from primordial water to meteorite-derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil. Perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water-rich as some Mid-Ocean Ridge Basalt source regions on Earth and that the water in the Earth and the Moon probably share a common origin.
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Affiliation(s)
- Mahesh Anand
- Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
| | - Romain Tartèse
- Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
| | - Jessica J Barnes
- Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK
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Campbell BA. High circular polarization ratios in radar scattering from geologic targets. ACTA ACUST UNITED AC 2012. [DOI: 10.1029/2012je004061] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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Siegler MA, Bills BG, Paige DA. Effects of orbital evolution on lunar ice stability. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003652] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [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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Neish CD, Bussey DBJ, Spudis P, Marshall W, Thomson BJ, Patterson GW, Carter LM. The nature of lunar volatiles as revealed by Mini-RF observations of the LCROSS impact site. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2010je003647] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Carter LM, Campbell BA, Hawke BR, Campbell DB, Nolan MC. Radar remote sensing of pyroclastic deposits in the southern Mare Serenitatis and Mare Vaporum regions of the Moon. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2009je003406] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Campbell BA, Hawke BR, Campbell DB. Surface morphology of domes in the Marius Hills and Mons Rümker regions of the Moon from Earth-based radar data. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008je003253] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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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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