Highlands Intermediate School 06-0043

    There is evidence of the possible existence of water ice on the moon.  Most of these suspected areas are near the north pole with a somewhat smaller area at the south pole that were possibly created by comet & asteroid bombardment.[1] Scientists have picked the Aiken Basin near the south pole as the best possible site to search for water because it is permanently shadowed.  They believe the water is concentrated in localized areas buried beneath about 40 centimeters of dry regolith.  Because the moon has no atmosphere, any water ice on the surface would be exposed to a vacuum.  During a lunar day when all regions of the moon are exposed to sunlight, the temperature can reach about 250 degrees F.  This plus the moon’s low gravity would cause any water ice on the surface to sublime directly into water vapor & escape into space.  For water ice to exist on the moon, it would have to be in permanently shadowed areas such as in the Aiken Basin which is a giant impact crater that is up to 12 km deep.  Within this basin, there are many smaller craters that are never exposed to sunlight and where the temperatures would never rise above -280 degrees F, allowing frozen water to form.[2][3]

http://www.pa.msu.edu/people/frenchj/moon/moon-15day-2884.jpg