Meadville Tribune

National News

March 15, 2013

Mars was habitable, but no sign of inhabitants

By drilling into Mars for the first time and analyzing a martian rock in unprecedented detail, Curiosity team members have shown that eons ago, microorganisms could have lived on Mars. At a spot on the floor of Gale crater-the site the rover has been studying since landing on Mars last August -- there was mud long-wetted by benign waters, a ready supply of the essential elements of life as we know it, and energy enough to power life. The search for the remains of ancient life was not so lucky.

Curiosity found "all the things we were really hoping for in a habitable environment," said Michael Meyer, lead scientist for NASA's Mars Exploration Program at headquarters in Washington. Curiosity project scientist John Grotzinger of the California Institute of Technology in Pasadena made it a bit more personal: "We have found a habitable environment so benign that if you were on the planet when water was around, you would have been able to drink it."

The news of certain martian habitability came Tuesday at a Curiosity press conference at NASA headquarters. Orbiting spacecraft had imaged lots of places where early in Mars history there was plenty of water-river channels and crater lakes for sure, maybe even an ocean-and some of those once-watery locales even had signs of clay. Rock turns into clay only after long exposure to water of more or less neutral pH. In fact, the Opportunity rover is still roaming across a plain of once water-soaked rock. But it turned out to be rotted by highly acidic brine-not a nice place for life.

The sediment that formed the rock outcrop drilled by Curiosity proved to have been far more hospitable, Curiosity team members reported at the press conference. For starters, geologists say that it could have been mud on the floor of a lake nestled on the crater floor 3 billion years or more ago, about the time fossil life first appeared on Earth. Curiosity's Chemistry and Mineralogy x-ray instrument showed that the rock is 20% to 30% clay. And the Sample Analysis at Mars (SAM) instrument package detected no chemical signs of high acidity or brines. Concentrated brines can suck the water out of any microbes.

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