WN: Wired News:
"Opportunity's wheels started slipping April 26 during a planned 295-foot trip. While trying to drive over a foot-high sand dune, the robotic explorer stopped moving, its wheels hub-deep in soft soil.
Engineers spent weeks with an Opportunity mock-up figuring out what commands to give the robot to free it, but the maneuvers took time. The rover inched forward less than a foot in a month, losing most of its traction every time it tried to roll.
'It's kind of like we were swimming through it,' Erickson said.
But on Saturday morning, data showed that Opportunity was free at last and had moved several feet across the dune."
I'll save you from the obligatory Energizer Bunny joke....