Wet past of life on Mars
The Martian landscape may not always have been this dry
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Tuesday, 22, May 2007 11:22
Some of the "best evidence yet" has been found to prove that ancient Mars was much wetter than it is now, scientists claim.
Images of the planet beamed back to the Earth show it to be dry, red and dusty, but soil analysed by Nasa's Spirit rover has shown that it has not always been this way.
The soil was rich in silica, and the concentrations of the material are such that scientists believe it can only be there because water was once present.
A chemical analyser at the end of Spirit's arm measured a composition of about 90 per cent pure silica for this soil.
Steve Squyres, principal investigator for the Mars rovers' science instruments, said that the discovery is "remarkable".
"The fact that we found something this new and different after nearly 1,200 days on Mars makes it even more remarkable. It makes you wonder what else is still out there."
It is thought that one possible origin for the silica could have been interaction of soil with acid vapours produced by volcanic activity in the presence of water. Another is that it could have been from water in a hot spring environment.
The discovery adds to evidence that the red planet once had conditions that could have been favourable to life.
David Des Marais, an astrobiologist at Nasa's Ames research centre, explained: "What's so exciting is that this could tell us about environments that have similarities to places on Earth that are clement for organisms."
Further studies of the soil patch and surrounding deposits have been planned.