Substantial water reserves have been found beneath the Moon’s surface, Nasa announced yesterday, paving the way for a permanent lunar base.

The discovery came from Nasa’s “moon bombing” mission, the Lunar Crater Observation and Sensing Satellite (LCROSS) probe, which was deliberately crashed into the lunar South Pole last month. An analysis of the dust thrown up from the impact revealed the presence of about 80 litres of water, or enough for a shallow bath. The results suggest that much larger, more accessible reserves are available at the poles.

“We can announce that we’ve found water — not just a little bit, a significant amount,” said Tony Colaprete, principal investigator for the mission at Nasa’s Ames Research Centre in California.

The exact form of the water is not yet clear, but it is likely to be spread out in small ice crystals. The rocket hit the Moon at an area where the surface temperature is around -230C. This region has not been in direct sunlight for at least two billion years.

The discovery comes at a good time for Nasa scientists, who are waiting for a White House decision on the future funding for lunar exploration, expected to be announced in January.

The Bush administration had set the ultimate goal of a permanent lunar base, but this could require an additional $3 billion a year on top of their $18 billion budget. Proposals for lunar settlements have all tended to rely heavily on the assumption that water supplies would be discovered.

“These results may just be the key to Nasa’s plans to put man back on the Moon — the LCROSS team conducted a beautifully simple experiment and it seems to have paid off,” said Chris Lintott, an astrophysicist from the University of Oxford.

The results will also come as a relief to astrophysicists who watched the impact live on October 9. The $79 million mission comprised two separate capsules, which were deliberately slammed into the Cabeus crater, around four minutes apart. The trailing capsule was designed to make spectroscopic measurements of the contents of a 6km plume of dust thrown up by the leading one. However, the impact was barely discernible and for several hours Nasa was unable to confirm that a plume had been detected at all, after having initially said that it would be visible through handheld telescopes from Earth.

Vincent Eke, from the University of Durham who helped the American space agency pick the location, said that the much smaller plume may have been a result of the large quantities of water. A high proportion of the capsule’s energy on impact would have gone into vaporising the ice, meaning there was less energy left to kick the dust up to high altitudes.

Scientists are now hoping to establish the origin of the water. One possibility is that it was deposited by comets, over as long as billions of years, meaning it could hold important clues to the history of the solar system.

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