News in Science

Mars too salty to sustain life

Life on Mars may have been snuffed out early on because the water there was too salty, a biologist involved in exploring the red planet says.

"Mars has been a very dry place for a very long time," says Professor Andrew Knoll, a member of a team operating two US robots that are currently exploring Mars. "The best place to look for life is in the earliest history," he adds.

"It was really salty and difficult for microorganisms to survive in this water," he says, citing discoveries by the robots that back up earlier theories that strong concentrations of minerals killed off life.

The Harvard University researcher was speaking on the sidelines of the annual meeting of the American Association for the Advancement of Science.

But the discoveries by the robots roving the planet, Spirit and Opportunity, cannot confirm whether life ever existed on Mars.

"If there is a habitable niche, it's underground" on the planet, says the head scientist for the mission, Professor Steven Squyres of Cornell University.

Life anywhere else would leave atmospheric traces of gas produced by organisms.

According to another theory cited by Knoll, "a large meteorite may have sterilised life on Mars".

In December the US space agency NASA says the Sprint robot had discovered nearly pure silicon on Mars.

Squyres says this silicon forms near natural hot water sources or volcanic outlets, which give off natural gas. On Earth, living microbes are found in such situations.