Spirit digs up clue to life on Mars

A wonky wheel on a robot rover has uncovered exciting new evidence that life could once have existed on Mars. The broken wheel on Nasa’s Spirit rover gouged out a deep trench in the martian dirt as it was dragged along.

Scientists back at mission control were astonished to see a bright patch of soil uncovered. Analysis shows it is a concentrated deposit of silica that could only have formed in the presence of water.

It provides overwhelming new evidence that ancient Mars was once a blue planet – a much wetter place where life may have formed.

Professor Steve Squyres, who is chief investigator for Nasa’s Mars rovers, said: “You could hear people gasp in astonishment. This is a remarkable discovery.”

Spirit and its sister probe Opportunity landed on opposite sides of Mars in January 2004 on what were planned to be 90-day missions. They are still trundling about the Red Planet after more than three years of operation. Spirit is being carried along by five wheels that are still working.

Professor Squyres added: “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.”

Spirit made the find while exploring a range of hills inside the 100-mile wide Gusev Crater. Spirit had previously found other indicators of water at the site long ago, such as patches of water-bearing, sulphur-rich soil, alteration of minerals and evidence of explosive volcanism.

Albert Yen of Nasa’s Jet Propulsion Laboratory, in California, said: “This is some of the best evidence Spirit has found for water at Gusev.”

Scientists say the silica could have formed from the interaction of martian soil with acid vapours produced by volcanic activity in the presence of water. It could also have come from water in a hot spring environment. But they say the latest discovery adds compelling new evidence for ancient conditions that might have been favourable for life.

Earlier this month, Nasa revealed that an orbiting probe had found evidence that water ice is still widespread on Mars. And in March, Europe’s Mars Express probe showed there is enough ice at the planet’s south pole to cover it with an ocean 36ft deep. In December, Nasa said they had found signs that water still flows on the red planet.

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