Nasa spacecraft detects water on the Moon

YES, there is water on the Moon: 11 million to 330 million tonnes of it, dispersed over 25,000 square miles at the satellite's poles, the US space agency said last night.

Nasa's Lunar Prospector craft has found that water, in the form of ice, is present in huge amounts beneath the surface, which could make it possible to set up a permanent base in space.

In contrast to the bullish spirit 18 months ago, when its scientists said that they had found fossil evidence of life on Mars, Nasa was restrained yesterday. It said the ice is distributed in "scattered pockets", meaning its usefulness is "not immediately clear. While the evidence of water ice is quite strong, the water signal (detected by the spacecraft's instruments) is relatively weak," said William Feldman, a Department of Energy researcher. "Our data are consistent with the presence of water ice in very low concentrations across a significant number of craters."

The question will be how easy it is to "mine" the ice and turn it into water, then into its constituent hydrogen and oxygen. Speaking at Nasa's Ames Research Centre in Moffet Field, California, chief investigator Alan Binder said: "If you picked up a cubic yard of soil in the cold areas of the pole, you might find as much as one, two, maybe five gallons of water per cubic yard. If ... we are dealing with 100 million metric tonnes, that's equivalent to a lake two miles on a side, four square miles, and about 35ft deep. That's a lot of water." Most of it is at the lunar north pole, where 18,000 square miles are reckoned to be water-bearing, compared to 7,200 square miles at the south pole. Since the Apollo landings 1969- 72, scientists thought the Moon was probably dry.

Last year the Clementine mission found evidence suggesting water at the poles - perhaps from comets which crashed there. The $65m (pounds 41m) Lunar Prospector, launched in January, marked Nasa's first return to the Moon since the last manned landing mission, Apollo 17, in 1972.

Lunar Prospector carried instruments to detect alpha particles, gamma rays and neutrons, with a radar experiment. The data meant scientists could analyse the lunar surface's composition and pinpoint gravity and magnetic features. The spacecraft will spend the rest of year mapping the Moon's surface. When it runs out of fuel, it will crash into the Moon, so as not to become a hazard to future missions.

If water can be mined on the Moon, it would ease the need of sending a supply from Earth. Water weighs 2kg per litre - the minimum daily requirement for a human - and it could take thousands of gallons to maintain a permanent Moon complex.

The presence of water could also enable astronauts to make their own breathing oxygen and to use the Moon as sort of a space-based filling station. Water can be split into its components, hydrogen and oxygen. Oxygen could be used for breathing and the combination of hydrogen and oxygen can be used as a rocket fuel.