Hopes Dashed for Ice on Moon
A radar image of the moon's south lunar pole, which shows dark crater regions never illuminated by the sun. Some scientists think water ice or hydrogen deposits may exists in such areas.
Credit: NASA

A permanently shadowed crater at the moon's south pole has long been suspected of harboring water ice deposits that might be used by future lunar colonists. No such luck, a new study suggests.

Scientists have debated whether or not these cold craters, constantly shielded from sunlight, could contain water ice, which could be melted for drinking water and potentially converted into rocket fuel.

NASA's Lunar Prospector mission (1998?1999) recorded an enhanced signal of hydrogen in these features. Some scientists contend that this hydrogen is in the form of water ice.

The Pentagon's Clementine lunar orbiter (1994) gave positive indications of water ice in one of the cold depressions called Shackleton crater, some scientists think. Others have disputed this interpretation because Earth-based radar of that area reflected a signal more indicative of rock than ice.

New images of Shackleton taken by the Japanese lunar explorer satellite KAGUYA (SELENE) support the view that there likely aren't any exposed water ice deposits in the crater.

The images were made during lunar mid-summer, when enough sunlight is scattered off the upper inner wall of the crater to provide faint illumination of the inside of the crater.

Junichi Haruyama of the Japan Aerospace Exploration Agency and his team analyzed the images and data. They suggest that temperatures in the crater are less than -297 degrees Fahrenheit (-183 degrees Celsius), certainly cold enough to hold ice. But the images reveal no conspicuous brightness that would indicate a patch of pure water ice.

This new analysis, detailed in the Oct. 24 issue of the journal Science, could mean that there is no water ice present at all in Shackleton crater, or that any ice that exists is mixed into the lunar dirt in low amounts, Haruyama and his team concluded.