On Earth, Adirondack calls to mind a majestic mountain range in upstate New York. On Mars, Adirondack cuts a slightly less imposing figure: the name refers to a football-size rock. But the boulder stands out as the first test subject for NASAs Spirit rover, as scientists aim to gain more insight into Martian geologic history.

Over the weekend, Spirit made its way 6.2 feet from its lander to park in front of Adirondack. The journey took about 30 minutes, with Spirit stopping to take photos along the way. "The drive was designed for two purposes, one of which was to get to the rock," explains Eddie Tunstel of NASAs Jet Propulsion Laboratory. "From the mobility engineers standpoint, this drive was geared to testing out how we do drives on this new surface." On Tuesday, Spirit reached out with its robotic arm to begin probing Adirondack for clues about its origin and composition. The rovers toolkit includes a microscope and two types of spectrometers, which can help the researchers to determine the elemental makeup of the Martian rock. "The hypothesis is that this is a volcanic rock, but well test that hypothesis," says Dave Des Marais of NASAs Ames Research Center. Meanwhile, Spirits twin, Opportunity, is set to touch down on the Red Planet on Sunday, at about five minutes past midnight (EST). The chosen landing site, a region called Meridiani Planum, is located on the other side of the planet, opposite the Gusev Crater area that Spirit is exploring.

While the rover is down in the dirt collecting data, the European Space Agencys Mars Express is beginning to return results from far above the planets poles. Mars Express entered its orbit around the Red Planet on December 25, 2003, and although its seven scientific instruments are still being calibrated, they have already beamed back some of the most detailed images yet of the Martian surface. The detailed image at right, for example, shows a section of the Grand Canyon of Mars, dubbed Valles Marineris, in colorful 3-D.