The doughty Mars rovers will celebrate their third anniversary on the Red Planet with new software that will make them smarter and more independent.
Spirit and Opportunity will have improved image processing capabilities that will help them search out dust devils and other weather patterns. A new navigation system will allow the rovers to spot hazards and figure out how to avoid them without help from controllers on Earth.
Until now, if the rovers encountered an obstacle, all they could do was back up and try a different direction. Sometimes the rover could not find a solution, said John Callas, the project manager for the Mars Exploration Rovers at Jet Propulsion Laboratory in Pasadena, Calif.
"With this new capability, the rover could find its way through a maze," he said.
The twin rovers continue to defy all expectations for their longevity. When Spirit landed on Jan. 3, 2004, and Opportunity followed three weeks later, experts hoped they would last through their planned mission of 90 Martian days, which are 37 minutes longer than Earth days.
Their key discoveries include uncovering evidence that water was once abundant on the surface of Mars in at least one region.
Opportunity also found a series of exposed rock layers showing that wind-blown dunes came and went while the water table fluctuated. Spirit spotted dust devils forming and moving across the arid surface.
As they begin their fourth year of work, Spirit has lost the service of one of its six wheels but remains mobile. Opportunity is looking for a path into Victoria Crater, where it could sample exposed layers of rock.