The 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.
"With this new capability, the rover could find its way through a maze," said John Callas, the project manager for the Mars Exploration Rovers at the Jet Propulsion Laboratory.
Spirit landed on Jan. 3, 2004, and Opportunity followed three weeks later.
Spirit has lost the service of one of its six wheels but remains drivable. Opportunity is skirting the edge of the half-mile-wide Victoria Crater, looking for a path into it.