NASA?s Mars Rover Spirit was up and running again yesterday for the first time since it developed communications problems 10 days ago, and just a day after its twin Opportunity rolled onto martian soil on the other side of the planet.

With Spirit declared ?healthy? again, NASA said it was the first time in history that two mobile robots were exploring the surface of another planet at the same time.

?We have confirmed that Spirit is booting up normally. Tomorrow we?ll be doing some preventive maintenance,? said Dr Mark Adler, mission manager at NASA?s Jet Propulsion Laboratory in Pasadena, California.

NASA scientists were able to restore Spirit to working order by deleting thousands of files, many left over from its seven-month flight to Mars, from its flash memory ? a type of re-writable electronic memory that retains information even when power is off.

Equipped with mobile laboratory

Spirit had trouble managing its flash memory, triggering its computer to reset itself about once an hour. Two days after Spirit?s problems arose on January 22, engineers began sending commands to the rover every day that avoided use of its flash memory.

Spirit, which landed in Mars? Gusev Crater on January 3, will over the next few days complete its examination of the surface of a football-shaped rock nicknamed Adirondack, which it was exploring when it short-circuited, NASA said.

The rover will then make its way toward a crater nicknamed Bonneville about 250 metres away, taking time to investigate two nearby pale rocks dubbed Cake and Blanco.

The golf cart-sized Spirit and Opportunity are each equipped with a mobile laboratory of geologic tools designed to search for evidence that there was once potentially life-sustaining water on the barren martian surface.

NASA said Opportunity will be commanded to reach out with its robot arm to examine the martian soil in front of it over the next few days with a microscope and a pair of spectrometer instruments to determine which elements and minerals it contains.

The dual successes of Spirit and Opportunity over the weekend were welcome news for NASA as the country marked the first anniversary of the disintegration of the space shuttle Columbia over Texas and the deaths of the seven crew members on board.

Gail Fitzer-Schiller