NASA's robotic rover on Mars has found signs that a vast and hospitable lake once spread over the now-desolate Martian surface, providing a potential home to past life for centuries or longer. The shallow water body was roughly the size of one of New York's Finger Lakes, though not nearly so deep. Its waters boasted low salinity, just the right acidity and all the chemicals needed to support living organisms. The scientists' arguments that the rover found more hydrocarbons than would be expected from contamination alone are "tenuous at best," says Jeffrey Bada, an emeritus professor of marine chemistry at Scripps Institution of Oceanography at UC San Diego, via e-mail. He says that if Curiosity really had stumbled on hydrocarbons, other kinds would've been detected, not just the few purified by the rover's chemistry set.