New research indicates the moon's water came from comets.
ScienceDaily (Jan. 12, 2011) — Researchers at the University of Tennessee, Knoxville, continue to chip away at the mysterious existence of water on the moon -- this time by discovering the origin of lunar water.
Larry Taylor, a distinguished professor in the Department of Earth and Planetary Sciences, was the one last year to discover trace amounts of water on the moon. This discovery debunked beliefs held since the return of the first Apollo rocks that the moon was bone-dry.
Then, he discovered water was actually pretty abundant and ubiquitous -- enough so a human settlement on the moon is not unquestionable.
Now, Taylor and a team of researchers have determined the lunar water may have originated from comets smashing into the moon soon after it formed.