Water on the Moon! Its presence would significantly advance the prospects of establishing a permanently-manned lunar base. Radar measurement of the south pole have provided tantalizing evidence of subsurface water, perhaps located in crater floors that rarely receive direct sunshine. In 2005 astronomers crashed a probe into the Moon's south pole hoping to release a plume of water vapor that could be detected by ground-based telescopes; no signature of water was seen. Nevertheless astronomers are planning further missions to the Moon to help determine whether or not there is water on the Moon.