We discovered last year that there's a surprising amount of water on the Moon's surface. Just don't get your hopes up that the whole satellite is watery - analysis of the Apollo rocks shows the lunar interior is completely dry.
Tests of the distribution of different chlorine isotopes in the rocks reveal they must have formed in a far drier environment than that of Earth, with 10,000 to 100,000 times less water inside than the Moon than inside the Earth. The question now is whether these findings also shed new light on the surface water discovery. If there is as much surface water as last year's finding suggested, that would require massive deposits to come from space. It's possible, but the researchers working with the Apollo rocks suggest last year's results drew conclusions from an unrepresentative part of the surface.