Data gathered by India's Chandrayaan probe and two other spacecraft indicates the Moon contains surprising quantities of water. Scientists discovered Moon soil is damp, a very fine film of H2O coats the particles that make up the lunar dirt. US moon researcher Larry Taylor estimates about a litre of water could be squeezed out of a cubic metre of lunar soil, making it a useful resource for future Moon expeditions.
The quantity of water is seen to increase the closer the observations are made to the poles - the very places the Apollo missions never went.
Scientists suspect the water is created in the soil in an interaction with the solar wind, the fast-moving stream of particles that constantly billows away from the Sun.
Harsh space radiation triggers a chemical reaction in which oxygen atoms already in the soil acquire hydrogen nuclei to make water molecules and the simpler hydrogen-oxygen (OH) molecule.
The amounts are small, say researchers, but boost the notion that astronauts based on the Moon could use it as a resource.