BEIJING, Aug. 19 (Xinhuanet) --  NASA's Mars rovers have uncovered more clues about how water shaped the Red Planet, scientists said Wednesday.

    According to a Reuters report, both Spirit and Opportunity spotted ancient evidence of water on Mars earlier in their missions but new data recorded by Spirit's scientific instruments this week suggests that the life-giving liquid was once more plentiful than they thought.

    Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California said Spirit discovered a swath of bedrock that showed signs of being altered by water and may yield clues about the planet's primordial atmosphere.

    Opportunity, which landed on a flat gray plain on the opposite side of Mars that scientists said was once drenched by a salty sea, planned to investigate a dune field inside Endurance Crater, where the rover has explored since June.

    The six-wheeled rovers have operated in Mars' harsh atmosphere more than twice as long as they were designed to but are beginning to experience minor mechanical problems.

    One of Spirit's wheels has lost power, while Opportunity's rock abrasion tool jammed twice last week, engineers said. Enditem

    (Agencies)