NASA's Spirit rover went for "a little Sunday drive" over the weekend, moving up to a football-sized rock called Adirondack to begin its geological exploration of the Martian surface.
The 9-foot trip took 30 minutes, but 28 of those minutes were spent on repeated stops for picture taking to assess progress, said Eddie Tunstel, a mobility engineer on the mission.
"The rover is sitting right now in front of that rock," said Tunstel of NASA's Jet Propulsion Laboratory in Pasadena.
The pyramid-shaped Adirondack is about 14 inches wide and 8 inches high, possibly made of volcanic basalt.
The team chose it because it does not appear to be covered with dust, the rover can safely approach it, and its flat surface is readily accessible to the craft's instruments.
The rover will spend at least three days studying the rock.
Using its robotic arm, Spirit will examine the rock with its microscopic imager, then with two spectrometers before grinding away a bit of the surface and repeating the procedure to see what is underneath the top layer.
The rocks "are little time capsules of the past," said geologist Dave Des Marais of the NASA Ames Research Center in Sunnyvale, Calif.
Comparing the interior and the exterior will help the team determine the history of the rock and how it has been affected by wind and, possibly, water.
"We might begin to see the signature of the processes that worked on the rock," Des Marais said.
After it is finished at Adirondack, Spirit will probably make one more move before "standing down" for three days over the weekend while engineers deal with the landing of the craft's twin, scheduled for Saturday evening on Meridiani Planum, halfway around the Red Planet.
Engineers made a minor correction in Opportunity's course on Friday and will probably not have to make any more, said JPL's Mark Adler.
"Everything is looking good for the upcoming landing," he said.