the LCROSS mission, switching the target from satellite crater Cabeus A. The change was made after review of the latest data gathered by other lunar exploration craft, which indicated that Cabeus proper had a higher concentration of hydrogen than Cabeus A. At 11:31 UTC on 9 October 2009 the Centaur upper stage of its Atlas V carrier rocket impacted Cabeus, followed shortly thereafter by the impact of the LCROSS spacecraft itself. The impact of the Centaur was intended to throw up a plume of lunar surface material to be sampled by sensors carried on the LCROSS spacecraft as it traversed the plume. But the debris plumes were smaller than predicted. Preliminary data from the LCROSS spectrometer measurements of the impact plume appeared to confirm the presence of water in the crater. Analysis of the plume observations supports the presence of water in the regolith. Absorption in the near-infrared can be attributed to ice and water vapor, while emissions in the ultraviolet indicate the presence of hydroxyl radicals, which also supports the likelihood of water. The estimated total amount of water vapor and ice in the plume is up to , or an estimated by mass. The spectral signatures of other volatiles were observed, matching the signatures of carbon dioxide, light hydrocarbons, and sulfur-bearing compounds. Satellite craters By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Cabeus. References External links USGS: Lunar south pole map Impact craters on the Moon