Spacecraft on lookout for ice on the moon

U.S. scientists say NASA's Lunar Reconnaissance Orbiter shows ice patches could make up 5 percent to 10 percent of material in the shaded walls of a crater. Using a radar instrument on the orbiter, astronomers have estimated the amount of ice likely to be found inside the permanently shadowed Shackleton crater located near the moon's south pole, Boston University researcher Bradley Thomson, who led the research, and colleagues reported in the journal Geophysical Research Letters. Observations indicate an enhanced radar polarization signature consistent with the presence of small amounts of ice in the rough inner wall slopes of the crater, researchers said. "The interior of this crater lies in permanent shadow and is a 'cold trap' -- a place cold enough to permit ice to accumulate," Ben Bussey of the Johns Hopkins University Applied Physics Laboratory said. The findings support the long-held belief that areas of permanent shadow inside polar craters are sites of the potential accumulation of water -- although not in any large amounts, the researchers caution. "Inside the crater, we don't see evidence for glaciers like on Earth," Thomson said. "Glacial ice has a whopping radar signal, and these measurements reveal a much weaker signal consistent with rugged terrain and limited ice."