The second mission, the Lunar Crater Observation and Sensing Satellite (LCROSS), aims to answer whether there is water on the Moon - either in the form of ice or hydrated minerals. It consists of two elements: a shepherding spacecraft and a Centaur upper stage rocket.
After being guided to a permanently shadowed crater at the Moon's south pole by its shepherding spacecraft, the Centaur rocket separates.
LCROSS will crash a rocket into the lunar surface
Hitting the Moon at more than 9,000 km/h (5,600 mph), the 2,200kg Centaur will kick up a huge plume of debris which could rise to 50km (30 miles).
It is expected to excavate some 350 metric tonnes of lunar material.
http://news.bbc.co.uk/1/hi/sci/tech/8107197.stm