Artist's rendition of the 4,400-pound (2,000-kilogram) Centaur upper stage rocket hitting the moon's surface near the south pole. The impact with the moon is expected to excavate about 220 tons (200 metric tons) of material from the lunar surface. The LCROSS shepherding satellite will observe the plume of material with a suite of six instruments to look for water ice and examine lunar soil kicked up by the impact. Credit: NASA/Roger Arno