Geological Chronicle
Cabeus lies about 100 km from the Moon's south pole. The crater is seen obliquely from Earth and remains in deep shadow for almost all of the time because it receives little sunlight, so little detail is visible even from orbit. Through a telescope, it appears near the southern limb, west of Malapert and south-southwest of Newton; libration affects visibility.
Subsequent impacts have eroded Cabeus, leaving an uneven rim with prominent ridges at the northern and southern ends. Its floor averages 4 km deep and is 60 km across; a small ridge lies near the center, and a crater 10 to 11 km across sits on the floor near the west-southwestern rim. The inner walls receive sunlight for 30% of a lunar day, while part of the western end stays in permanent shadow. In the shaded region, temperatures are below 100 K, which could let water ice remain on or near the surface for billions of years without sublimating.
The LCROSS mission was sent to look for water at the lunar south pole. On September 28, 2009, Cabeus proper was selected as the impact target instead of satellite crater Cabeus A after new data indicated a higher hydrogen concentration at Cabeus. On October 9, the Centaur upper stage of an Atlas V rocket struck the crater, followed shortly by LCROSS; sensors on the spacecraft sampled the plume. Plume analysis supported the presence of water in the regolith, with an estimated up to 155 ± 12 kg of water vapor and ice. Spectral signatures also matched carbon dioxide, light hydrocarbons and sulfur-bearing compounds.
The name Cabeus first appeared in Giovanni Riccioli's 1651 work Almagestum Novum, for Italian astronomer Niccolò Cabeo. At the time, the name marked the site later assigned to Newton crater. In 1935, the IAU Commission 17 adopted the crater's official name and location in Named Lunar Formations, by Mary A. Blagg and Karl Müller.