The Mars Odyssey spacecraft has found what appears to be large areas of ice on the red planet's surface.
U.S. scientists say Odyssey which began mapping the Martian surface last week has detected significant amounts of hydrogen near the planet's south pole.
This, they say, indicates the likely presence of ice formed from water. The discovery also bolsters the theory that life once existed on the Red Planet.
Earlier missions to Mars by other spacecraft have discovered deep canyons and other geologic features that also suggested water once flowed on the planet.