One of the new software programs allows spacecraft to examine and "recognize" certain types of features. For instance, Spirit has photographed numerous images of dust whirlwinds and clouds, and scientists are learning to select the most relevant parts of those images to send back to Earth, freeing up communication time for other discoveries, according to NASA.
Three more capabilities allow the rover to better navigate away from hazards, keep "recognizing" a landscape feature as it drives by and judge on the same day whether it can use the tools on its robotic arm to investigate an object, rather than waiting a day for the crew on Earth to give the go-ahead.
As for investigating the Mars terrain, the rover Opportunity is circling and photographing Victoria Crater, searching for a way inside -- and out. "We're not interested in having a one-way suicide mission unless we have to," said Steve Squyres, the mission's principal investigator and a professor of astronomy at Cornell University, at a meeting of the American Geophysical Union in December.
Once inside, Opportunity will inspect the exposed layered rock along the walls of the half-mile-wide crater, which scientists hope will tell more of the story of Mars' environmental past.
On the other side of Mars, meanwhile, Spirit has spotted two iron-nickel meteorites, but cannot drive to them because the rocks in the way are too large, said Ray Arvidson, deputy principal investigator of the Mars rover mission.
Opportunity also found a rock with a similar composition to a meteorite that hit Earth from Mars.
The solar-powered rovers were only intended to last three months on the Red Planet, but have surpassed their life expectancies many times over.
Soon after the rovers touched down in January 2004, they encountered evidence of Mars' watery past, including rock formations and sediment layering that showed signs that water at one time seeped to the surface.
After making those initial headline-grabbing discoveries, the mission researchers now are doing more in-depth field study, said Squyres.
"We come up with new stuff almost every day," he said.
Eventually, NASA hopes to send other rovers to Mars to study more areas, retrieve samples and search for possible biological signs.