7 December 2006

Mars may hold a key ingredient for life

Cosmos Online
Bright-coloured gullies on Mars could indicate recent deposits left by liquid water, the key element of life, according to NASA.
Mars may hold a key ingredient for life

Two Mars Global Surveyor photographs showing the appearance of a light-coloured, possibly water-bourne, deposit in a gully in the southern hemisphere of the Red Planet. Credit: NASA

SYDNEY: Bright-coloured gullies on Mars could indicate recent deposits left by liquid water, the key element of life, according to NASA.

“These observations give the strongest evidence to date that water still flows occasionally on the surface of Mars,” said Michael Mayer, head of NASA’s Mars Exploration Program.

Liquid water is considered vital to life and, to date, the only water found on Mars has been in the form of ice or water vapor.

The newly-photographed gullies, each several hundred metres long, are finger-shaped, “what you would expect to see if the material were carried by flowing water,” said Michael Malin, lead researcher in the study, to be published on Friday in the journal Science. The research is based on photos taken by the Mars Orbiter Camera aboard the U.S. space agency’s Mars Global Surveyor spacecraft.

While Mars’s surface is far too cold for liquid water to exist for long, the team believes underground water filtered to the surface carrying debris downslope long enough to form the gullies before it froze.

The light tone of the deposits could be from surface frost continuously replenished by ice within the body of the deposit. Another possibility is a salty crust, which would be a sign of water’s effects in concentrating the salts. According to the researchers, If the deposits had resulted from dry dust slipping down the slope, they would likely be dark, based on the dark tones of dust freshly disturbed by rover tracks, dust devils and fresh craters on Mars.

Mars Global Surveyor has discovered tens of thousands of gullies on slopes inside craters and other depressions on Mars in the more than 200,000 photos it has taken of the Red Planet. Malin and his team first reported the discovery of the gullies in 2000. To look for changes that might indicate present-day flow of water, his team repeatedly imaged hundreds of the sites. One pair of images showed a gully that appeared after mid-2002. That site was on a sand dune, and the gully-cutting process was interpreted as a dry flow of sand.

Today’s announcement is the first to reveal newly deposited material apparently carried by fluids after earlier imaging of the same gullies. The two sites are inside craters in the Terra Sirenum and the Centauri Montes regions of southern Mars.

“These fresh deposits suggest that at some places and times on present-day Mars, liquid water is emerging from beneath the ground and briefly flowing down the slopes. This possibility raises questions about how the water would stay melted below ground, how widespread it might be, and whether there’s a below-ground wet habitat conducive to life. Future missions may provide the answers,” said Malin.

NASA abruptly lost contact with the Mars Global Surveyor last month, and has since been unable to re-establish contact.

with NASA

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