NASA’s Curiosity rover has been exploring Gale Crater on Mars since 2012, and has collected data showing many chemical variations in the crater’s sedimentary rocks. A team led by Joel Hurowitz of Stony Brook University in New York analysed the data and conclude that older rocks seem to have formed in relatively cold climates. By contrast, younger sediments suggest that environmental conditions were warmer and wetter. The crater could have been hospitable to life between 3.8 billion and 3.1 billion years ago, not long after it was first formed.
In a separate study, a team led by Jens Frydenvang of the University of Copenhagen looked at data from elsewhere in the crater and found large amounts of silica that appear as light-coloured halos on the red rocks. As in hot springs on Earth, the silica was probably deposited by warm water percolating through the ground. It’s unclear when this water movement occurred, but it is likely to be some of the most-recent water flow in the crater, the authors say.