Nasa’s plans to set up manned colonies on the Moon were dealt a blow tonight when astronomers revealed they had detected no signs of ice there.

The space agency was hoping that pockets of ice might lie near the lunar south pole and be used as water for drinking and to be converted into fuel.

But Nature reports in tomorrow’s edition that detailed radar maps of the Moon made from Earth show no evidence for ice in its craters.

Radio dishes at Arecibo in Puerto Rico, and Green Bank in West Virginia, produced the highest-resolution radar pictures ever made of the Moon. They gave astronomers their best views of the landscape at the lunar south pole, where craters are permanently shadowed from sunlight.

Theories that there could be ice in the craters were boosted in 1992 when similar craters on planet Mercury were found to contain ice deposits.

A Nasa probe is being sent to the Moon in 2008 with the prime aim of seeking signs of water on the Moon. It will crash a missile into a crater deliberately to see if there is any ice. But Professor Donald Campbell, of Cornell University, who led a joint US and Australian team, said his radar observations had found no trace of water.

He said: “These new results do not preclude ice being present as small grains in the lunar soil. There is always the possibility that concentrated deposits exist in a few of the shadowed locations not visible to radars on Earth, but any current planning for landers or bases at the lunar poles should not count on this.”

The picture is a mosaic of images of the lunar south pole taken by Nasa’s Clementine spaceprobe.