Last October, NASA crash-landed a rocket near the lunar south pole, lofting water in the resulting debris. Newly published studies of this mission, called LCROSS, reveal that about 5.6 per cent of the ejected material was water, and that similar concentrations of water may exist under the surface in a "permafrost" layer. Lead scientist Anthony Colaprete at NASA's Ames Research Center in California estimates that there could be a billion gallons of water within 10 kilometres of the probe's impact site.
Other chemicals were also detected in the impact plume by a spacecraft flying behind the impactor. "We're seeing a kitchen sink of other stuff that may be useful for human exploration," says Michael Wargo, NASA's chief lunar scientist.
One of the big surprises was two strong ultraviolet emission lines of silver. Because they appeared a few seconds after impact, Colaprete and his colleagues suspect that the silver might be in a layer of rock buried below the surface.