LCROSS

The Lunar Crater Observation and Sensing Satellite, known as LCROSS, was a robotic spacecraft operated by NASA to investigate the nature of hydrogen previously detected at the polar regions of the Moon. Launched alongside the Lunar Reconnaissance Orbiter, its main objective was to determine whether that hydrogen signature came from water ice held in a permanently shadowed lunar crater. The mission succeeded in confirming the presence of water ice in the southern lunar crater Cabeus by deliberately crashing a spent rocket stage into it and analyzing the resulting debris plume.