Scientists Confirm Ice in Craters Near the Lunar South Pole

Since the mid-1990s, scientists have had indications that there could be water ice inside permanently shadowed craters near the south pole of the Moon. These regions, where the Sun remains low on the horizon and never warms the soil, maintain temperatures just a few degrees above absolute zero. Any ice that would accumulate there, would be there virtually forever. Last decade's Lunar Prospector and Clementine spacecraft could only detect the presence of hydrogen, not of water. But results released on Nov. 13, from data collected by the Lunar CRater Observation and Sensing Satellite, or LCROSS, have now provided indisputable evidence for water ice inside lunar polar craters.

On Oct. 9, the Centaur upper stage rocket, that had taken LCROSS from Earth orbit to the Moon, crashed, with pinpoint accuracy, into Cabeus crater. Trailing behind the Centaur, LCROSS collected four minutes of data as it flew past the plume of crater soil debris the Centaur crash had created, looking for the signature of water. Unlike other spacecraft observations, which had been limited to one part of the electromagnetic spectrum, both infrared and ultraviolet measurements were taken. The spectra of water were clearly seen in both wavelengths.

Mission scientists estimate that the material from the 65-foot-wide hole created by the impact contains about 25 gallons of water. While this is described as a "significant amount," lunar soil is still comparable in moisture content to the deserts on Earth. But water will be a very precious commodity on the Moon, required to sustain life, and as a feedstock for oxygen and hydrogen rocket fuel. In situ processing technologies, particularly using nuclear energy sources, could allow future colonists to process the soil and liberate the stored water, which would then avoid having to transport it from Earth.

Scientific results from India's Chandrayaan lunar mission, released in late September, revealed a thin layer of water ice on the surface of the Moon, covering nearly the whole body. That ice, warmed during the lunar day, disappears by noon. So where the water on the Moon comes from, and where it goes, is still a question to be answered through upcoming lunar missions.