ST. LOUIS – They move slowly and take naps. Their camera lenses are mottled by dust, their wheels sometimes gimpy.

Remember the Mars rovers? After a year and a half on the red planet, Spirit and Opportunity are still puttering along, poking at rocks that tell the story of the planet’s warm and watery ancient environment.

On Sunday, Spirit crawled backward to the top of 300-foot tall Husband Hill – the highest any rover has been – ending a climb that took more than a year. Friday, the rover is set to finish a panoramic picture, which NASA plans to release next week.

Each day the rovers last beyond their original 90-day mission is more loving labor for Washington University geologist Ray Arvidson, the No. 2 mission scientist.

“I haven’t run out of steam yet,” said Arvidson, who shepherds detailed Spirit plans through four daily meetings.

Tuesday morning, Arvidson planned Spirit’s 583rd Mars day, or Sol, while connected in a videoconference with dozens of scientists and engineers. Arvidson vetoed suggestions of moving the rover to a slightly more scenic spot. Instead, Spirit’s schedule would be simple and safe: a 310-degree antenna turn, four naps (to recharge) and the start of the three-day panoramic camera shot.

Steve Ruff, an Arizona State University geologist, wanted to skip the “pan cam” and get back to scientific tests.

“We might die tomorrow. I think the pan cam is going to blow the mind of the rover,” he said.

They have reason to be cautious. Rocks have stuck in the wheels. One wheel has also run hot, forcing engineers to drive backward while dragging it. Dust on the solar panels has sapped energy. The freezing and thawing caused by daily 100-degree Celsius temperature swings also worries Arvidson.

But on Tuesday, some of the scientists seemed content to snap a nice picture atop Husband Hill after a long, slippery climb that involved zigzags, K-turns, and parallel parking maneuvers.

“We had to learn a lot of new tricks,” said Chris Leger, an engineer at NASA’s Jet Propulsion Laboratory and one of a dozen “drivers” who avoids boulders bigger than 8 inches and slopes steeper than 30 degrees.

The drivers turn scientific goals – moving to a rock, sampling it – into hundreds of precise commands that are radioed directly to the rover.

After Friday’s photo shoot is finished, Arvidson says, Spirit will return to science full time, with its worn drill bit and aging Mossbauer spectrometer, already past the half-life of the radioactive isotope the iron-detecting instrument relies on.

Spirit has already uncovered more varied rocks than its twin on the other side of the planet. Opportunity hit the jackpot early on by landing amid rocks formed near the shore of an evaporating sea 4 billion years old.

But in the uplifted rocks of Husband Hill, Spirit has found evidence for water in the past couple billion years, Arvidson said. Some of the glue-like minerals in the rocks suggest a rising and falling water table.

The history of water on Mars, he says, is “much more diverse than anybody thought.”

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