From Wireservices: NASA plots next steps for Mars rovers With the Mars rovers still functioning after completing their missions, NASA is planning their overtime work. PASADENA, Calif. - The rovers have already made history. They landed safely on Mars, motored around its surface, photographed everything in sight and found evidence that today's rock-strewn wasteland once accommodated liquid water. Pretty good. Now what? That is the question that scientists at NASA's Jet Propulsion Laboratory are asking this month as the two rovers, Spirit and Opportunity, complete the job they were sent to do. From now on, they are on overtime as they embark on extended forays expected to last until the middle of September -- perhaps beyond. The extra mission begins May 1, but the transition is well underway. Planners have found $15 million in additional funding, started software upgrades for the rovers and put scientists on Earth time after three exhausting months of round-the-clock -- the Mars clock -- staffing. They have also chosen new targets to explore. After a mostly uneventful sojourn at Gusev Crater, Spirit is embarked on a nine-tenths-of-a-mile drive to a highland known as Columbia Hills, where planners hope to find rock outcrops that will provide new insights into Mars' geologic history. Opportunity, meanwhile, has begun a 750-yard traverse to the edge of a crater dubbed Endurance. Scientists hope to find as much as 100 feet of exposed rock that could offer fresh clues about the extent of an ancient salt sea whose traces Opportunity discovered only a few yards from its landing site on Meridiani Planum. If the crater shows promise, Opportunity's handlers may decide to drive into it. If it shows spectacular promise, they may plunge in, even if they might never get out. ''The rovers go down a lot better than they go up,'' flight system manager Richard Cook said. ``Will we take the bird in the hand? There will be a strong inclination to do that.'' The major imponderable is how long the two rovers will function. The mission's 90-day design life ran out for Spirit on April 5 and will run out for Opportunity on April 26, but neither machine shows the slightest sign of slowing down, wearing out, losing communications, freezing to death, blowing an engine or otherwise falling apart. Cook said engineers have had several major concerns about the rovers' hardware, beginning with the falling efficiency of the solar arrays that charge the vehicles' batteries. During the first part of the mission, charging capacity declined by 0.13 percent per day because of dust accumulating on the array panels. But Cook noted that the 1997 Mars Pathfinder arrays stopped degrading after a 20 percent loss of efficiency, probably because new dust either blew away or created a prism effect that helped the batteries charge. The same thing appears to be happening with the new rovers, he said. As a result, he added, the rovers should be able to function until Mars' winter solstice, Sept. 20, even though the sun's power diminishes with the cold season's advance.