Scientists Estimate Ice Content in Shackleton Crater on Moon's South Pole
Posted on June 22, 2012
NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft has returned data that indicates ice may make up as much as 22% of the surface material in the Shackleton crater, which is located on the moon's south pole. The team of NASA and university scientists using laser light from LRO's laser altimeter examined the floor of Shackleton crater. They found the crater's floor is brighter than those of other nearby craters, which is consistent with the presence of small amounts of ice.
Gregory Neumann of NASA's Goddard Space Flight Center in Greenbelt, Md., a co-author of the paper published here in Nature, says, "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."
The crater, named after the Antarctic explorer Ernest Shackleton, is two miles deep and more than 12 miles wide. The small tilt of the lunar spin axis means Shackleton crater's interior is permanently dark and extremely cold. The LRO spacecraft mapped Shackleton crater using a laser to illuminate the crater's interior and measure its albedo or natural reflectance. The laser light measures to a depth comparable to its wavelength, or about a micron. The team also used the instrument to map the relief of the crater's terrain based on the time it took for laser light to bounce back from the moon's surface. The longer it took, the lower the terrain's elevation.