Martian Water. The thought of Martian canals comes to mind. NASA’s Curiosity rover mission has found evidence a stream that once ran vigorously across the area on Mars where the rover is driving. There is earlier evidence for the presence of water on Mars, but this evidence — images of rocks containing ancient stream bed gravels — is the first of its kind. Scientists are studying the images of stones cemented into a layer of conglomerate rock. The sizes and shapes of stones offer clues to the speed and distance of a long-ago stream’s flow.