By ELANOR MAYNE, Mail On Sunday

Last updated at 11:00 28 May 2006

Scientists have paved the way for the first permanently manned base on the Moon by developing a way to 'squeeze' oxygen out of lunar soil.

Nasa experts say the technique will allow astronauts of the future to create their own supplies of the gas instead of transporting it all from Earth.

The space agency plans to take its extraction system to the Moon in 2011 as part of its Robotic Lunar Exploration Program, which will test a range of equipment designed to support human life. If the technique is successful, it could lead to a permanent station like Moon-base Alpha from the popular Seventies series Space: 1999.

To extract oxygen from lunar soil, scientists used a lens-like structure to focus sunlight on to it, heating it to 2,500C.

In Nasa's latest tests, a 12ft-wide dish was used to concentrate the sun's rays on to 100g of a substance similar to Moon soil. After a few hours, one fifth of the substance had turned into oxygen.

The soil is kept in a vacuum during the process to help suck out the oxygen.

Lunar soil brought back to Earth is in short supply and highly prized, so Nasa researchers have been using matter with the same composition for its tests.

The soil contains about 45 per cent oxygen by weight, but it is mostly 'trapped' in the form of silcon dioxide.

Nasa plans to repeat the same processs on the Moon to produce oxygen, which could support life and be used to help fuel rockets setting out on deep-space missions.

At the moment, all oxygen supplies would have to be brought from Earth, which is so expensive and energy-inefficient that it effectively rules out a permanent Moon base.

Dr Eric Cardiff, an engineer at Nasa's Goddard Space Flight Centre in Maryland, explained: 'Part of the advantage of the technique is that we're using the resources that are present on the Moon. We're living off the land, as it were.'

He added: 'You can breathe pure oxygen. There are some trace gases mixed with the oxygen we produced but they're in very small amounts. There is nothing dangerous.'

The next step for scientists will be to reduce the temperature needed to extract oxygen.

Carrying out the method on the Moon would involve a mining operation to collect soil and feed it into a reactor, where the oxygen could be drawn off.

It will be easier to lift the soil than it would be on Earth because the Moon has a lower gravity.

Alternative methods to extract oxygen from Moon soil are also under investigation, including melting the rocks into a liquid and freeing oxygen with an electric current.