NASA’s LCROSS mission impacted Cabeus crater near the Moon’s south pole.
On October 9, 2009, LCROSS sent the spent Centaur rocket stage into Cabeus, followed by the mission’s shepherding spacecraft several minutes later. The deliberate impact excavated material from a permanently shadowed part of the crater so instruments could analyze the resulting debris plume.
Cabeus was selected because its shadowed floor is extremely cold and showed signs of elevated hydrogen. Observations of the plume provided strong evidence for water ice and other volatile materials in the lunar polar soil, an important result for future exploration.
LCROSS launched with the Lunar Reconnaissance Orbiter in June 2009, but the missions had different jobs: LRO surveyed the Moon from orbit, while LCROSS investigated the composition of a specific polar impact site. Clavius, Copernicus, and Tycho are prominent lunar craters, but none was LCROSS’s target.