Frankengeek

After five frustrating weeks, engineers at the Jet Propulsion Laboratory have managed to free the Mars rover Opportunity from a sand dune where it had been stuck.

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.

The soil in which Opportunity got stuck was described earlier by one of the JPL engineers as being like talcum powder, so loose that it provided virtually no traction. The plan the team ultimately worked out, which has succeeded, was to spin the rover's wheels in short bursts, very slowly inching it forward. Now, after moving, again, less than a foot in a month, it has gone forward several feet in one day, leaving behind a clear trail of tire marks, visible in the photo.

Opportunity and its twin Spirit landed on Mars in January 2004 for what were supposed to be 90-day missions. So far, they have exceeded those expectations by 487 and 507 days, respectively.