Broken wheel uncovers clue to life on Mars

Broken wheel uncovers clue to life on Mars
By Duncan Hooper
22/05/2007
The Telegraph UK

A broken wheel on a space vehicle has led Nasa to some of the most conclusive evidence yet that Mars may once have been able to support life.

When one of the Mars Spirit rover's six wheels stopped rotating, it ploughed a deep trench into the planet's surface, uncovering a patch of soil that was made up of about 90% pure silica.

The discovery is significant because the production of the substance would have required the presence of water, a key ingredient in the formation of life.

Nasa scientists said yesterday it was a "remarkable" find "which continues to spur the hope that we can show that Mars was once habitable and possibly supported life."

The team has already found other indicators of long-ago water, such as patches of water-bearing, sulphur-rich soil, alteration of minerals and evidence of explosive volcanism, while exploring a low range of hills inside a basin named Gusev Crater.

One possible origin for the silica could have been interaction of soil with acid vapours produced by volcanic activity in the presence of water, a Nasa spokesman said.

Another could have been from water in a hot spring environment.

David Des Marais, an astrobiologist at Nasa's Ames Research Centre in Moffett Field, California, said: "What's so exciting is that this could tell us about environments that have similarities to places on Earth that are clement for organisms."

The Spirit, and its twin rover Opportunity, completed their three-month prime missions in April 2004, but continue to operate despite showing signs of age.

The churning of the soil caused by the Spirit's broken wheel has exposed several patches of bright soil, leading to some of its biggest discoveries at Gusev, including this latest one.

Spirit had been working within about 50 yards of latest discovery for more than 18 months before the discovery was made.

Steve Squyres, principal investigator for the Mars rovers' science instruments, said: "You could hear people gasp in astonishment."

Mr Squyres, of Cornell University, said: "This is a remarkable discovery. And 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."