BBC: After just seven weeks of roaming the surface of Mars, NASA’s Curiosity rover has found evidence of ancient liquid water. The robot has sent pictures of classic conglomerate rocks, made up of gravel and sand, found on the planet’s surface. One large slab, named Hottah for a lake in Canada’s Northwest Territories, contains pebbles whose size and rounded shape indicate they were transported and eroded in water. Researchers think the rock was part of a network of ancient streams that flowed several billion years ago. With further study, they hope to determine the water’s pH value and the speed and distance of the water flow—and, ultimately, whether such an environment could ever have supported microbial life.