NASA says the Curiosity rover has uncovered signs of an ancient freshwater lake on Mars that may have supported tiny organisms for tens of millions of years.
The lake near the Martian equator existed about 3.5 billion years ago. Scientists say it was neither salty nor acidic, and contained nutrients -- a perfect spot to support microbes.
The findings were published online Monday in the journal Science and presented at the American Geophysical Union meeting in San Francisco.
Curiosity touched down near the Mars equator last year. Now that the $2.5 billion mission has accomplished a key goal -- finding a habitable environment -- the rover will look for organic compounds that are fundamental to all living things.