Along with its Centaur booster, the Lunar CRater Observation and Sensing Satellite (LCROSS) was deliberately smashed into the moon on October 9, in a bid to detect water that might be present as ice in some of the permanently shadowed spots on the moon's surface. At the time, ground-based astronomers, both professional and amateur, were disappointed when the impact failed to produce a plume visible from Earth. However, NASA scientists analyzing the data returned from LCROSS announced today that large quantities of water have been detected.

The plume kicked up by the impact of a spent rocket stage in a lunar crater as detected by the LCROSS probe minutes before it too crashed into the Moon. Picture courtesy NASA

The chosen impact site was in Cabeus crater, near the Moon's south pole. Preceding LCROSS on its suicide run by a few minutes was the spent Centaur rocket stage that boosted LCROSS toward the Moon (incidentally, the Centaur is one of the oldest and most reliable boosters in service, its basic design having first flown in 1963). Although too faint to see from Earth, when the Centaur crashed its plume was visible to LCROSS's camera and spectrographs. According to the scientists, water is the only material that matches the spectral analysis of the plume. They also detected the presence of other materials that have been collecting in Cabeus's shadows for billions of years, but these have not yet been identified.

How this data will play into the current policy debate over whether or not NASA should continue its plans to establish a base on the moon is unknown, but it does suggest that the Moon has at least a few surprises left in store.