Widespread water may cling to moon's surface

A large portion of the moon's surface may be covered with water. That is the surprising finding of a trio of spacecraft that have turned up evidence of trace amounts of the substance in the lunar soil.

Many scientists suspect water ice might lurk in permanently shadowed craters at the moon's poles, which play host to some of the coldest known regions in the solar system.

But new findings suggest that a small amount of water clings to lunar soil across the moon's surface. The first detection was made by India's Chandrayaan-1 probe. The spacecraft, which failed in August after less than 10 months in orbit, was the first lunar orbiter to carry an instrument capable of measuring how much light is absorbed by water-bearing minerals.

"There's nothing else it could be," says Carle Pieters of Brown University in Providence, Rhode Island, leader of the Chandrayaan-1 instrument team that made the detection.

Chandrayaan-1 found hints of water across the lunar surface when it measured a dip in reflected sunlight at a wavelength absorbed only by water and hydroxyl, a molecule that contains one atom of hydrogen and one atom of oxygen.

But the team was not convinced they had found water. "We spent literally months digging up anything we could find that could possibly explain this feature, simply because we didn't think it was there on the surface," Pieters says.

To help verify the signature, team members turned to data collected by NASA's Cassini probe, which buzzed the moon in 1999 on its way to Saturn, and NASA's Deep Impact spacecraft, which flew past the moon in June 2009 en route to an encounter with the comet Hartley 2. Both spacecraft also showed evidence of water and hydroxyl, molecules that are likely both present on the moon.

But seemingly not in great quantities. Harvesting water from a baseball-field-sized swathe of soil might field "a nice glass of water", Pieters told New Scientist. Nonetheless, it might provide a resource for future lunar explorers.