LOS ANGELES (AP) – NASA’s Mars rovers don’t seem to be wearing out, so mission planners have begun to think more boldly – including a plan to let one climb up a steep slope from a crater it has been exploring to set out across a plain.

“The rovers have lasted longer than expected, but as long as we have them we’re going to keep them busy,” project manager Jim Erickson said Thursday in a conference call with reporters.

Already on the second extension of their mission, rovers Spirit and Opportunity have lasted so long that mission scientists have left NASA’s Jet Propulsion Laboratory and returned to their own institutions, working via telephone and video conferences and remote networking.

“We realized that if we were going to make rover operations sustainable over the long term we were going to have to let people go back and live at their homes again,” said Steve Squyres, rover mission principal investigator, of Cornell University.

Since landing on opposites sides of Mars in January, both of the six-wheel robots have found evidence of past water activity – including new discoveries of rocks with polygon-shaped fractures that could indicate two eras of water activity in a crater named Endurance.

The rovers are still capable of work, and controllers may even have Opportunity leave Endurance Crater soon via a 25- to 30-degree slope dubbed “escape hatch.”

“It is right on the hairy edge of what we think the vehicle is capable of,” Squyres said.

The next target would require a 11/2-mile trip across the smooth Meridiani plains to a place called “etched terrain,” where scientists believe they will find rocks exposed by the gentle erosion of wind, unlike the rocks they’ve found so far that were exposed by violent impact events.

Spirit, meanwhile, has a balky right front wheel after a nearly two-mile roll across the vast Gusev Crater region to the Columbia Hills.

Controllers have continued to drive it with five wheels while saving the problem wheel for situations when it is needed.

“As the vehicles age we may very well see aches and pains begin to happen here and there. We’ll have to learn to deal with the problems as we go,” Erickson said.

The rovers together have sent to Earth some 50,000 images, including a new 360-degree panorama from Spirit, looking back from its position in the hills. The view includes parts of the rover, the drop-off to the plain, a distant ridge and the walls of Gusev Crater about 50 miles away.

On the Net:

JPL: http://www.jpl.nasa.gov

AP-ES-10-07-04 2201EDT

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