"The brightness measurements have been puzzling us since two summers ago... While the distribution of brightness was not exactly what we had expected, practically every measurement related to ice and other volatile compounds on the moon is surprising, given the cosmically cold temperatures inside its polar craters."
Source: Gregory Neumann of NASA's Goddard Space Flight Center in Greenbelt, MD, a co-author of a paper suggesting that NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft has returned data that indicate ice may make up as much as 22 percent of the surface material in a crater located on the moon's south pole.