On Earth, we consider design, fuel efficiency, and enduring power when thinking of “green” vehicles. But there’s one solar-powered all-terrain vehicle that has by some lights out-performed anything rolling around on Earth. It is the doughty little robotic rover Opportunity, doggedly using its seven-year-old solar array to chug over the rocky surface of Mars.
Opportunity, like its twin rover Spirit, was designed to drive about .6 mile (1 kilometer) along the martian surface; by last month, Opportunity had driven more than 30 times that distance. It completed its primary mission in 2004 and since then has made important discoveries about parts of ancient Mars that might have been hospitable to microscopic life.
Like many earthly vehicles that are a bit past their prime, Opportunity has a few quirks, according to NASA’s Dave Lavery, who spoke at a briefing on the rover’s latest findings.
“We’re no longer driving a hot sports car,” he said. “We’re now driving a 1965 Mustang that hasn’t been restored.”
Even though Opportunity’s “drivers” are on Earth, controlling the golf-cart-sized robot remotely, they plainly feel a fair amount of affection for the little craft. NASA’s John Callas described the rover’s status almost as if it were a spunky grandparent.

“We have a very senior rover that’s showing her age,” Callas told reporters. “She had some arthritis and other issues, but generally she’s in good health, she’s sleeping well at night, her cholesterol levels are excellent and so we look forward to productive scientific exploration for the period ahead.”

Operating it takes a bit of doing. First off, to avoid wear on some gear teeth, Opportunity drove most of her latest jaunt backwards. Her NASA operators also warmed up actuators to the rover’s wheels, which made lubricants flow better — like applying a heating pad to an arthritic joint before a game of tennis, Callas said.

The backwards-driving had to work around an antenna that was supposed to be on the back of the craft but was recently right in the center of the robotic vehicle’s “windshield” as it drove in reverse for miles. “It’s much like trying to drive a car and your child is waving a toy in front of your face,” according to Callas.

There was also some stiffness in the rover’s robotic arm, cutting back on its freedom of movement.