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How life from Earth may have hitched a space ride to Mars

Posted on: Thursday, 25 March 2004, 06:00 CST

LIFE may exist on Mars - from organisms that hitched a ride on spacecraft from Earth.

An American scientist has claimed that such microbes may have survived on the Red Planet after arriving on a series of unsterilised robotic probes.

Dr Andrew Schuerger, of the University of Florida, said: "I believe there is life on Mars - and it's unequivocally there because we sent it."

He said microbes could have remained aboard the NASA rovers Spirit and Opportunity, which are currently roaming Mars, and Britain's ill-fated Beagle 2 mission, which has been missing since December.

Dr Schuerger said NASA's two Viking craft, which landed on the Red Planet in 1976, were the only Mars landers to have been adequately sterilised.

After studying the ability of organisms to survive on craft, Dr Schuerger believes that some organisms would have reached Mars and might even have made themselves at home, New Scientist magazine reported.

The scientist, who was speaking at a meeting of planetary experts in Houston, Texas, said it was by no means certain that Earth life would perish on the harsh surface of the Red Planet.

Images and other evidence suggest that briny, acidic water may have existed for a long time in the Martian soil, he said.

Some kinds of acid brine could be liquid even today, providing a moist environment where bacteria could grow.

Dr Schuerger said if a spacecraft's surface is made of a material that repels water, any water on the surface collects into droplets that shrink as they dry, concentrating the microbes and helping them to survive.

Dr Jeff Kargel, of the US Geological Survey, said ponds and marshes of acidic brines are possible, or even probable, on Mars. He said of the likelihood of microbes from Earth withstanding conditions on Mars: "They are probably not going to survive in sulphuric acid, but maybe they could.

"And maybe we've just done a really terrible thing."

The claim follows the discovery of signs that a salty sea once existed on Mars, further evidence of possible past life.

The find was made from photographs taken by the Opportunity rover, which is believed to have reached what was once a seashore.

It suggests that the pool of saltwater was at least 2in deep. A rocky outcropping examined by the rover had ripple patterns and concentrations of salt, strong signs that the rock had formed in standing water.

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