Lunar water
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.
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 100 kilometres (62 mi). 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. In September 2009, NASA payload Moon Mineralogy Mapper onboard Chandrayaan-1 detected water on the Moon surface and hydroxyl absorption lines in reflected sunlight. In November 2009, NASA re-confirmed water on moon with its LCROSS space probe which 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". In March 2010, it was reported that the Mini-SAR 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.
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