It took a few days for the Mars Exploration Rover Spirit to get going, but the wheeled robot has now unfolded its six legs and started producing a color and infrared panoramic view of its landing site in Gusev Crater. NASA geologists believe the crater may once have contained a lake roughly the size of Connecticut. Soon after rolling off the lander last Thursday, Spirit’s Miniature Thermal Emission Spectrometer detected carbonates in the dust around the landing site. Carbonates form only in the presence of water, but the discovery isn’t conclusive evidence of an ancient lake because the minerals could have been created by reactions between dust and water vapor in the atmosphere.
To show that Mars once had large bodies of liquid water—a necessary precursor for life—Spirit needs to find more concrete evidence: Larger amounts of carbonates hidden within bigger pieces of rock, for instance, or rounded particles indicating that some of the local rocks are composed of lake or river sediments. That search began January 20, when Spirit took its first rock sample from a mountain-shaped lump that scientists have named Adirondack. (As of press time, controllers were optimistic that they had managed to reestablish contact with the rover after an agonizing break in its data transmissions.)
“We chose Adirondack because it was a short drive and has an interesting, shiny surface and a flat face,” says Catherine Weitz, program scientist for the Mars Exploration Rover Mission. “The engineers looked at the surface and said it was something they could ‘RAT’ on,”—referring to Spirit’s Rock Abrasion Tool, used to grind away the rock’s weathered outer surface and provide a clean area for chemical analysis by the rover’s spectrometers. The instruments will determine the elemental composition of the rock and will look for iron-bearing minerals. Iron reacts with water in well-known ways, so studies of such minerals will help geologists determine the role that water played in the rock’s formation.
After sampling Adirondack and other rocks near the landing site, Spirit will drive toward a meteor crater named Bonneville 270 yards northeast. The meteor impact may have exposed rocks from as deep as 30 yards beneath the surface, giving Spirit a glimpse into Mars’s geological past. “It is a nice hole in the ground that allows us to see exposures of buried layers that we can’t see from just driving around,” says Weitz.
Once its instruments have analyzed the mineral landscape of the crater, Spirit will roll toward the hills east of the landing site and use its panoramic camera to image an area that could possibly contain exposed rock layers. Weitz is also eager simply to get a better view. “The hills look Earth-like,” she says. “We didn’t expect to see such beautiful topography on the horizon.”