NASA'S twin rovers reached out their robotic arms to touch the surface of Mars, marking the first time in the joint US$820 million mission that both spacecraft were in full swing.

　　Opportunity and Spirit, 10,620 kilometers apart on opposite sides of the planet, began the workweek on Monday gearing up for in-depth analyses of the soil and rocks beneath their wheels.

　　Opportunity rolled onto the Martian ground on Saturday, a week after it landed.

　　Spirit arrived on January 3 but broke off its science work nearly two weeks ago after software problems crippled the vehicle.

　　On Monday, mission manager Jennifer Trosper said Spirit had joined Opportunity back at work, even as engineers worked out the last kinks in its computer software.

　　"We have two operational rovers on Mars," Trosper said at NASA's laboratory.

　　NASA also showed the first 360-degree color image taken by Opportunity of its landing site.

　　The rover touched down in one of the flattest, smoothest regions on Mars but ultimately came to rest inside a crater 21.6 meters across.

　　"It provides us with a real sense of 'you are there,"' said scientist Jeff Johnson of the US Geological Survey office in Flagstaff, Arizona.

　　Johnson likened the mosaic image to the overlapping snapshots tourists often take of the Grand Canyon, one of America's most popular attractions, to capture its full sweep.

　　Opportunity stretched out its robotic arm and photographed in detail each of the four instruments it carries.

　　The arm is the most complex mechanism on each rover and was reported to be working well.

　　NASA planned for it to brush the dust off a volcanic rock dubbed Adirondack, allowing the rover's to photograph it in extreme close-up.

　　NASA launched the pair of vehicles to find geological evidence of past water activity on Mars. That could show the planet was hospitable to life perhaps billions of years ago.

　　It appears Opportunity has not had to venture far to find such evidence: It has already discovered an iron-rich mineral called gray hematite, and preliminary measurements suggest it is of a variety that forms in liquid water.

　　Spirit, in contrast, may have to drive hundreds of meters, to a nearby crater called Bonneville, to uncover similar geologic proof.