The rock, which researchers have named Adirondack, was to be examined by a microscope attached to a camera and by instruments that examine mineral composition, a Mossbauer spectrometer and an alpha particle X-ray spectrometer, said Mark Adler, one of the Mars Exploration Rover mission specialists.

Scientists have the results from preliminary tests last week on Martian dust, run by a Mossbauer spectrometer showing three components -- olivine, Fe2 and Fe3 -- containing iron, said Goestar Klingelhoefer, who is in charge of the instrument at the Johannes Gutenberg University in Mainz, Germany.

The X-ray spectrometer identified large amounts of iron and silicon, according to Johannes Brueckner, an expert on the tool at the Max Planck Institute in Mainz.

The robot moved about three meters to reach the rock, two minutes of non-stop rolling punctuated by several photo sessions, according to officials at NASA's Jet Propulsion Laboratory in Pasadena, California.

"These are the sorts of baby steps we are taking," said Eddie Tunstel, the engineer in charge of Spirit's move.

"The drive was designed for two reasons, one of which was to get to the rock," Tunstel said. "From the mobility engineers' standpoint, this drive was geared to testing out how we do drives on this new surface."

Researchers want to know to what degree the robot may be prone to skid on the dusty Martian surface.

They chose Adirondack over another rock dubbed Sashimi, which would have been a straight drive, as Sashimi appeared dustier and thus possibly harder to examine.

Stones are like time capsules, giving scientists a glimpse at elements of a past environment, explained Dave Des Marais, one of the team's researchers.

"We have now used all of our tools with the exception of the RAT (rock abrasion tool). Like a Swiss army knife, each gadget has its own strength," said mission scientist Steve Squyres.

Spirit arrived on Mars January 3. Its twin, Opportunity, was due to touch down overnight January 24-25.

The 820 million dollar mission expects each solar powered robot to keep working for about three months.

SPACE.WIRE