PASADENA, Calif., Oct. 28 (UPI) -- The U.S. space agency says its Mars Reconnaissance Orbiter has found evidence that liquid water remained on Mars far longer than previously theorized.
The National Aeronautics and Space Administration spacecraft has observed hydrated silica, or opal, spread across large regions of Mars. That, scientists said, suggests liquid water was on the planet's surface as recently as 2 billion years ago.