NASA’s Spirit rover should be able to wriggle free of its sandy trap on Mars after all, says a scientist for the mission. But the robotic explorer will need to survive the bitter Martian winter first.

In April 2009, Spirit’s wheels broke through a thin surface crust and got mired in the loose sand below. After months of trying unsuccessfully to free the rover, NASA declared on 26 January that Spirit would henceforth be a stationary lander mission rather than a rover.

But the announcement was “a little bit premature”, rover scientist Ray Arvidson of Washington University in St Louis, Missouri, told researchers at the Lunar and Planetary Science Conference in Houston, Texas, on Monday.

In nine drives between 15 January and 8 February, mission members coaxed the rover into driving backwards by 34 centimetres – “pretty good for a lander”, Arvidson said. That far surpasses the mere millimetres of motion Spirit had managed in previous efforts.


The technique involved swivelling the rover wheels from side to side, which cleared away some of the loose soil beneath the wheels and compacted what remained. By alternating wheel swivelling with short drives, the rover was able to make slow and steady progress.

“We only stopped because we ran out of sunlight” as winter approached, Arvidson said. Spirit is hibernating now, with too little power to continue driving. “After we come out from hibernation in September or October, my suspicion is that a couple weeks [of driving] and we’ll back out [of the trap],” he said.

But first Spirit will have to survive the cruel Martian winter. In previous winters, it was able to park on slopes that tilted its solar panels northwards, maximising the amount of sunlight falling on them at Spirit’s location in the southern hemisphere of Mars.

This time around, Spirit’s solar panels are tilted slightly to the south, which means power is likely to drop lower than ever before in the mission. That could leave Spirit with too little juice to warm its electronics, and they could break if they get too cold. “It will be dicey,” Arvidson admits.