Earlier this year scientists made the historic announcement that they had found ice on the moon buried at the lunar poles.

The discovery was made just weeks after the Lunar Prospector spacecraft entered the moon's orbit on the 16 January.

Water just below the surface

Refined calculations of the amount of lunar water are 10-times higher than the lower limit estimated earlier this year. The new research is published in Science magazine.

The new analysis also shows that the water is confined to localised areas near the poles, rather than spread out evenly across the polar regions, as was assumed.

The ice appears to be buried about half a meter beneath the lunar surface. There may be as much as three billion tonnes of water at each of the lunar poles. There may be slightly more at the north than the south pole.

When they presented their initial results in March, the scientists said that the water was likely in the form of a fine frost spread through the lunar soil. Further data analysis suggests the exciting possibility that their may be shallow deposits of ice.

The south polar region

Scientists assume that comets carried the water ice to the moon.

Lunar Prospector's instruments have also been surveying the moon's surface composition and have discovered that one well-known lunar feature - the huge Mare Imbrium basin - is unlike anything else of the moon.

"The mission has been an overwhelming success," said scientist Bill Feldman. "We have got beautiful science from two or three of our instruments. The third, we just have not had time to analyse the data yet."

According to another scientist working on the project, Rick Elphic: "We have barely begun scratching the surface of the analysis. We have not begun to touch on the many ramifications for the origin and evolution of the moon.