Warmer, wetter conditions lasted until 3.5 billion years ago
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.
J.P. Grotzinger et al. A habitable fluvio-lacustrine environment at Yellowknife Bay, Gale Crater, Mars. Science. Published online December 9, 2013. doi: 10.1126/science.1242777.
D.T. Vaniman et al. Mineralogy of a mudstone at Yellowknife Bay, Gale Crater, Mars. Science. Published online December 9, 2013. doi: 10.1126/science.1243480.
S.M. McLennan et al. Elemental geochemistry of sedimentary rocks at Yellowknife Bay, Gale Crater, Mars. Science. Published online December 9, 2013. doi: 10.1126/science.1244734.
D.M. Hassler et al. Mars’ surface radiation environment measured with the Mars Science Laboratory’s Curiosity rover.Science. Published online December 9, 2013. doi: 10.1126/science.1244797.
D.W. Ming et al. Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale Crater, Mars. Science. Published online December 9, 2013. doi: 10.1126/science.1245267.
K.A. Farley et al. In situ radiometric and exposure age dating of the Martian surface. Science. Published online December 9, 2013. doi: 10.1126/science.1247166.
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