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  •  Water water everywhere (2+ / 0-)
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    iceweasel, QuestionAuthority

    The "water on the moon" craze started about 10 years ago when the Clementine spacecraft found decreased neutron flux at the lunar poles, indicating (perhaps) that neutrons formed by radioactive decay in the moon's crust were being absorbed by hydrogen, in the form of H2O.

    Even if true, the hypothetical amount of water in the lunar regolith, as the kids say, would have been about 1%--i.e., about the water content of concrete. Not exactly convenient for use, although it could be said that there was a lake's worth if however many gazillion tons of regolith are considered. So that finding kind of languished.

    The idea that the polar craters have water took things up a notch, with the hope that solid ice might be found right on the surface.

    This came out fairly recently:

    Japan's now-finished lunar mission found no water ice

    "However, [Selene imaging] indicates that exposed relatively pure water-ice deposits are lacking on the floor [of Shackleton Crater]," according to the Japanese report. Japanese scientists said in Houston they could not find water ice anywhere else in craters near the Moon's rugged south pole, one of the primary NASA justifications for flying the LCROSS mission.

    The LRO press kit mentions two competing theories for why Clementine saw decreased neutron flux at the poles, both involving absorption of same by hydrogen: either in water form, or alternatively hydrogen deposited from solar wind could be more stable and accumulate more due to the cold polar temperatures.

    So the hydrogen detected by Clementine and Chandrayaan-1 (by inference from neutron flux measurements) could be just that deposited by the solar wind, not water or ice. It's all in the interpretation, or a one scientific wag put it, "if I hadn't believed it I wouldn't have seen it!"

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