Scientists have found evidence of an ancient freshwater lake on Mars well suited to support microbial life. The lake located inside Gale Crater where the rover landed in August 2012, likely covered an area 31 miles long and 3 miles wide though its size varied over time and Analysis of sedimentary deposits gathered by NASA's Mars rover Curiosity shows the lake existed for at least tens of thousands of years. There is no water left in it but drill tests and chemical analysis of fine-grained rocks by the Curiosity robot's science tools suggest conditions were right for the lake to have once supported microbial life, perhaps 3.6 billion years ago. The rocks contained signs of carbon, hydrogen, oxygen, nitrogen and sulphur, and would provide perfect conditions for simple microbial life. Even if life never started on Mars, organic material presumably would have been deposited on the surface by crashing comets and asteroids.