How habitable was Mars in the past? Since NASA's Curiosity rover touched down on Mars in August 2012, it has helped answer a few of these questions in the area surrounding its equatorial landing site of Gale Crater.
Most notably, in March 2013, Curiosity investigators announced extensive evidence of a lake bed or river system in a region that NASA dubs "Yellowknife Bay." The environment, which could be a favorable spot for microbes, includes minerals such as clays that are formed in waters that once existed the...
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