Analysis of the data sent from the Lunar Prospector satellite has shown that there are likely to be billions of tons of ice just under the Moon's surface, which could be used as drinking water and fuel for future manned missions.
Scientists from Nasa, the American space agency, originally thought that the signals sent back from the satellite indicated that water existed as a widely diffuse ``frost'' of frozen water in the lunar soil.
But further analysis indicates that large chunks of frozen water are present, having been deposited over thousands of years by ice-laden comets falling into shaded craters where the day-time temperature has never exceeded the melting point of water.
Ice would be easier to mine as a source of drinking water for the inhabitants of a lunar base and would be a valuable source of energy.
Solar-generated electricity could split lunar water into hydrogen and oxygen, the essential ingredients of rocket fuel, making it feasible for the Moon to be used as a staging post to explore other planets.
Bill Feldman, a lunar scientist at the Los Alamos National Laboratory in New Mexico, said the latest data, which is published in the journal Science, shows that the mission to explore the lunar surface has been an ``overwhelming'' success.
An instrument on board the $63m (pounds 103m) satellite was able to identify the presence of small amounts of hydrogen on the lunar surface, which serves as a signature for the presence of water.
Scientists believe hydrogen is likely to be bound up in water molecules in the lunar soil, trapped in the cracks and crevices of craters near the poles that have never been exposed to direct sunlight.
``The data show clearly where the hydrogen is. It's localised in spots near the poles and it has be buried about half a metre or so,'' Dr Feldman said.
``In making our initial estimates, we assumed the water was spread over the `footprint' [area scanned by] the instrument. As we've gathered more data we've found that it's not spread out as we first assumed, but concentrated,'' he said.
Nasa scientists estimate that there may be as much as three billion tons of ice deposited at the lunar poles, with there being about 15 per cent more at the north pole.
Although the manned Apollo missions to the Moon failed to detect any water, scientists believe this was because the spacecraft landed near the equator, where any water would quickly evaporate in the intense sunlight.
A satellite mission in 1994, called Clementine, suggested that there may be as much as a billion cubic metres of water at the lunar poles - enough to fill Lake Eerie, one of the North American Great Lakes - but this result was disputed by some scientists.
The Lunar Prospector had the benefit of much more sensitive instruments, which could detect a cup of water in a cubic metre of lunar soil, with the result that it has produced a much larger estimate.Reuse content