Spirit Makes Tracks on Mars
Spirit looks back at its tracks on Sol 1861 of its mission on Mars. Its immobile right-front wheel, which forces the rover to drive backwards, churned up bright soil. The edge of Home Plate forms the horizon on the right side of this image. Husband Hill i
Credit: NASA/JPL-Caltech

On its way toward its next destination on Mars, NASA's Spirit rover took a glance back at the tracks it has made on its journey, which exposed a bright patch of dirt.

Spirit is on its way from a low plateau called "Home Plate," where it spent the Martian winter, to two features dubbed von Braun and Goddard.

Spirit and its twin rover, Opportunity, have been roaming the Martian surface for more than five years now, after touching down in January 2004. Opportunity is also on its way to a new target, Endeavour Crater, miles (12 kilometers) away.

On the 1,861st sol, or Martian day, of Spirit's mission (March 28 here on Earth), the rover used its front hazard-avoidance camera to look back at the tracks it had made that day.

The rover's right-front wheel, immobile since 2006, churned up a long stripe of bright soil during this drive. Where Spirit has found such bright soil in the past, subsequent analysis of the composition found concentrations of sulfur or silica that testified to past action of water at the site.

When members of the rover team saw the large quantity of bright soil exposed by the Sol 1861 drive, they quickly laid plans to investigate the composition with Spirit's alpha particle X-ray spectrometer.

The Sol 1861 drive took the rover past the northwest corner of Home Plate, making progress on a route around the western side of the plateau, which can be seen on the right side of the image taken by Spirit. The rover covered about 74 feet (22.7 meters) of ground during this drive.