|
Lunar water is water that is present on the Moon. Liquid water cannot persist at the Moon's surface, and water vapor is decomposed by sunlight, with hydrogen quickly lost to outer space. However, scientists have since the 1960s conjectured that water ice could survive in cold, permanently shadowed craters at the Moon's poles. Water molecules are also detected in the thin layer of gases above the lunar surface.〔(【引用サイトリンク】title=Atmosphere of the Moon )〕〔(【引用サイトリンク】title=Is There an Atmosphere on the Moon? | NASA )〕 Water (H2O), and the chemically related hydroxyl group (-OH), can also exist in forms chemically bound as hydrates and hydroxides to lunar minerals (rather than as free water), and evidence strongly suggests that this is indeed the case in low concentrations over much of the Moon's surface. In fact, adsorbed water is calculated to exist at trace concentrations of 10 to 1000 parts per million. In 1978 it was reported that samples returned by the Soviet Luna 24 probe contained 0.1% water by mass sample. Inconclusive evidence of free water ice at the lunar poles was accumulated from a variety of observations suggesting the presence of bound hydrogen. On 18 November 2008, the Moon Impact probe was released from India's ''Chandrayaan-1'' at a height of . During its 25-minute descent, the impact probe's Chandra's Altitudinal Composition (CHACE) recorded evidence of water in 650 mass spectra gathered in the thin atmosphere above the Moon's surface.〔(Water on the Moon: Direct evidence from Chandrayaan-1's Moon Impact Probe ). Published on 2010/04/07.〕 In September 2009, Chandrayaan-1 detected water on the Moon and hydroxyl absorption lines in reflected sunlight. In November 2009, NASA reported that its LCROSS space probe had detected a significant amount of hydroxyl group in the material thrown up from a south polar crater by an impactor; this may be attributed to water-bearing materials – what appears to be "near pure crystalline water-ice".〔("Ice deposits found at Moon's pole" ), BBC News, 2 March 2010〕 In March 2010, it was reported that the Mini-RF on board Chandrayaan-1 had discovered more than 40 permanently darkened craters near the Moon's north pole that are hypothesized to contain an estimated 600 million metric tonnes (1.3 trillion pounds) of water-ice.〔 Water may have been delivered to the Moon over geological timescales by the regular bombardment of water-bearing comets, asteroids and meteoroids 〔 Elston, D.P. (1968) "Character and Geologic Habitat of Potential Deposits of Water, Carbon and Rare Gases on the Moon", Geological Problems in Lunar and Planetary Research, Proceedings of AAS/IAP Symposium, AAS Science and Technology Series, Supplement to Advances in the Astronautical Sciences., p. 441〕 or continuously produced ''in situ'' by the hydrogen ions (protons) of the solar wind impacting oxygen-bearing minerals.〔(【引用サイトリンク】title=NASA - Lunar Prospector )〕 The search for the presence of lunar water has attracted considerable attention and motivated several recent lunar missions, largely because of water's usefulness in rendering long-term lunar habitation feasible. ==Lunar water discovery== On 24 September 2009 ''Science'' magazine reported that the Moon Mineralogy Mapper (M3) on the Indian Space Research Organisation's (ISRO) ''Chandrayaan-1'' had detected water on the Moon. M3 detected absorption features near on the surface of the Moon. For silicate bodies, such features are typically attributed to hydroxyl- and/or water-bearing materials. On the Moon, the feature is seen as a widely distributed absorption that appears strongest at cooler high latitudes and at several fresh feldspathic craters. The general lack of correlation of this feature in sunlit M3 data with neutron spectrometer H abundance data suggests that the formation and retention of OH and H2O is an ongoing surficial process. OH/H2O production processes may feed polar cold traps and make the lunar regolith a candidate source of volatiles for human exploration. The Moon Mineralogy Mapper (M3), an imaging spectrometer, was one of the 11 instruments on board Chandrayaan-1, whose mission came to a premature end on 29 August 2009.〔 101004 isro.org〕 M3 was aimed at providing the first mineral map of the entire lunar surface. Lunar scientists had discussed the possibility of water repositories for decades. They are now increasingly "confident that the decades-long debate is over" a report says. "The Moon, in fact, has water in all sorts of places; not just locked up in minerals, but scattered throughout the broken-up surface, and, potentially, in blocks or sheets of ice at depth." The results from the ''Chandrayaan'' mission are also "offering a wide array of watery signals." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lunar water」の詳細全文を読む スポンサード リンク
|