Volume 46 | Issue 5 | June 2004
Spirit and Opportunity have completed their jobs, but now they're working (R)overtime
By Sarah Merlin
Having completed their original three-month assignment with flying colors, the twin Mars rovers Spirit and Opportunity are now working overtime for their bosses at NASA's Jet Propulsion Laboratory in Pasadena.
The six-wheeled robotic geologists were launched separately in June 2003 from Cape Canaveral Air Force Station, Fla., and made successful landings in January for a 90-day mission. As the initial assignment came to a close in April, the program was officially extended through September and the pair will continue working as long after that as they are able.
In the first phase of the mission, the rovers uncovered exciting evidence of the presence of water in the Red Planet's past. Pictures of rocks sent back to JPL confirmed that liquid water once coursed through the Martian geology, changing the planet's texture and chemistry.
Currently, Spirit is at work in a range of 300-foot hills dubbed the Columbia Hills - named for the crew of the lost Shuttle mission STS-107 - that took the rover two months to reach after crossing a plain near where it landed in Gusev Crater. After climbing into the range, Spirit immediately began transmitting photos of rocks unlike any scientists have seen.
"Some of the rocks appear to be disintegrating," said Dr. Larry Soderblom, a rover science team member from the U.S. Geological Survey in Flagstaff, Ariz.
"They have an odd kind of rotting appearance, with soft interiors and resistant rinds or hulls. The strangest things we've encountered are what we're calling 'hooded cobras,' which are evidently the resistant remnants of some of those rocky rinds. They stand above the surface like small canopies."
The entire area Spirit is exploring is within its landing site. Scientists anticipate finding a complex blend of rocks in the Columbia Hills, perhaps holding evidence of a broader range of environmental conditions than has been seen in the volcanic rubble surfacing the plain.
Meanwhile, Opportunity has been driven into stadium-sized Endurance Crater halfway around the planet from where Spirit is doing its digging. En route, the rover drilled into a rock it had impacted during landing and also examined a mysterious crack in the Martian surface that scientists have dubbed "Anatolia."
Opportunity's first target in the crater was a flat-lying stone about 14 inches by six inches called "Tennessee" for its shape. Using its spectrometers and the microscopic imager on its robotic arm, the rover will analyze the stone and allow scientists to examine different sedimentary sequences in the region - color differences among the layers of rock suggest at least three lower, older layers beneath the surface where Opportunity is stationed.
Spirit is the first of the two robotic explorers to exhibit signs of wear, with one wheel drawing two to three times the amount of current as the other five. During coming weeks, project scientists will study options for addressing the potential degradation. In the mission's initial phase, a reload of the crafts' software packages - from a distance of some 200 million miles - was completely successful in addressing glitches that hampered operation of Spirit's rock abrasion tool and Opportunity's communications system.
Additional information and photos about the rovers' extended mission is available at http://marsrovers.jpl.nasa.gov.