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Mars was habitable longer, more recently than thought

Warmer, wetter conditions lasted until 3.5 billion years ago

WETTER ONCE  Curiosity’s Mast Camera surveyed Mars’ Yellowknife Bay formation, a region that could have supported liquid water for millions of years. The foothills of Mount Sharp, Curiosity’s primary destination, are at upper left.

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The dried-up Martian lakebed where NASA’s Curiosity rover landed last year could have supported microbial life for millions of years, ending as recently as about 3.5 billion years ago. The findings, described in six studies published December 9 in Science, expand what scientists thought was a very brief window of time during which life could have thrived on the Red Planet.

Curiosity, an SUV-sized rover, landed on Mars in August 2012 in a region full of rocks that resemble weathered clays on Earth. In March, researchers announced that minerals in a sample drilled in an area known as Yellowknife Bay had formed long ago in a lake that was neither salty nor acidic. The lake’s water may have been hospitable to bacteria (SN Online: 3/12/13). Now, after finding multiple layers of clays in the area and determining the chemical composition and ages of several samples, researchers are confident that this temperate era was prolonged, perhaps giving simple life a chance to take hold.

Curiosity hasn’t detected complex organic chemicals that are essential for life. But project scientist John Grotzinger of Caltech notes that many of the ancient rocks Curiosity analyzed reached the surface relatively recently, so their molecules haven’t been severely battered by solar radiation. He adds that the rocks are about the same age as the oldest rocks on Earth with signs of life, possibly allowing researchers to compare the planets’ early life-friendly environments.

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