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Friday, 17 August, 2001, 12:19 GMT 13:19 UK
Martian meteorite may contain water
NWA 817 Bruno Fectay
Not from Earth: NWA 817 was blasted off Mars
Image courtesy of Bruno Fectay

By BBC News Online science editor Dr David Whitehouse

A meteorite found in the Western Sahara may contain water that could have come from below the surface of Mars, French researchers say.

Discovered last December, meteorite NWA 817 weighs 104 grammes (three and a half ounces).

It is the fourth Martian meteorite to be classified as a nakhlite because of its distinctive mineral composition.

A detailed analysis of various forms of hydrogen within the rock suggests it was exposed to water from below the surface of Mars.

Possible contamination

The ratio of hydrogen and its isotope deuterium - another form of the atom - can tell researchers if the rock was exposed to water and, possibly, where that water came from.

"We detected a very low deuterium/hydrogen ratio, close to a reading for the Earth," said Dr Phillipe Gillet, director of the National Institute for Sciences of the Universe in France.

"Our interpretation is that this refers to a fluid that came from the planet's interior, not its surface," he added.

Analysis of the three other known nakhlites shows that they have also been exposed to water, but which came from the planet's surface. However, experts are concerned that the water could be just the result of contamination after the Martian rock landed on Earth.

Life questions

Dr Monica Grady of the Natural History Museum in London, UK, told BBC News Online: "Desert meteorites are often badly weathered, and water exchanges very easily during weathering so it could be contamination."

Dr Gillet admits that contamination is a possibility.

"However, if we are right, that means part of the water contained in the Martian mantle did not rise to the surface of the planet," he said.

If it is confirmed that the water came from sub-surface rocks in Mars' mantle it would add to the debate about how much water Mars had in the past. Also, because life needs water, it would be pertinent to the question of life on the planet.

Last year, the Mars Global Surveyor spacecraft in orbit around the planet saw what might be evidence of recent running water on its surface.

Martian meteorites are believed to have been blasted off the planet by an impact with a large object many millions of years ago. After wandering in space for millions of years some of the chunks of rock fell down on to Earth.

See also:

24 Jan 01 | Sci/Tech
Meteorite clue to water on Mars
09 Apr 01 | Sci/Tech
Mars and Moon rocks discovered
11 May 01 | Sci/Tech
Trade growing in stolen meteorites
23 Jun 00 | Sci/Tech
Water may flow on Mars
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