astroengine writes "Gale Crater, the region being explored by NASA's Curiosity rover, isn't the only place on Mars where ancient microbes may have thrived. New evidence from NASA's senior robotic Mars scout, Opportunity, shows life-friendly water once mixed with telltale, clay-bearing rocks that now lie on the broken rim of Endeavour Crater, an ancient 14-mile wide basin on the other side of the planet from Gale. 'If I were to go Mars early in time and wanted to do a well, I'd do it there,' planetary scientist Ray Arvidson, with Washington University in St. Louis, told Discovery News. 'It's like drinking water. This would have been a niche for whatever life at the time existed.'"