A year after landing, Mars probes continue work

This image obtained from Nasa on August 19, 2004, taken by the Mars Exploration Rover 'Spirit' shows a rock outcrop dubbed 'Longhorn,' and behind it, the sweeping plains of Gusev Crater.PHOTO: AFP/NASA

Spirit landed on the Red Planet on January 3, 2004, followed by Opportunity three weeks later.

"The unanticipated longevity is allowing both rovers to reach additional destinations and to keep making discoveries," The Jet Propulsion Laboratory of the National Aeronautics and Space Administration said in a statement.

"The rovers are both in amazingly good shape for their age," said JPL's Jim Erickson, a rover project manager. "The twins sailed through the worst of the Martian winter with flying colors, and spring is coming. Both rovers are in strong positions to continue exploring, but we can't give you any guarantees."

Opportunity was the first to discover a few months ago that salt water once existed on Mars.

Spirit found a mineral, geothite, another indicator that water once existed on the planet.

NASA's next Mars mission, the Mars Reconnaissance Orbiter, is due to launch in August.