In March 2013, NASA announced that its Curiosity rover — which had landed in Gale Crater in August 2012 — had found evidence that Mars once had environmental conditions favorable for microbial life. Analysis of a drilled rock sample from an ancient streambed called Yellowknife Bay revealed clay minerals formed in neutral-pH water, along with the key chemical elements for life (carbon, hydrogen, oxygen, phosphorus, sulfur, nitrogen) and chemical energy sources that microbes could have used. It was the most definitive evidence yet that Mars was once habitable. Curiosity continued exploring for over a decade, climbing the slopes of Mount Sharp and building an increasingly detailed picture of Mars's wet, warm past.
Continue reading