This three-frame animation aids evaluation of performance of the right-front wheel on NASA's Mars Exploration Rover Spirit during a drive on the rover's 2,117th Martian day, or sol (Dec. 16, 2009). This wheel, on the right side of the images, had stopped operating in March 2006 and had not been used for driving since then. However, it revolved with apparently normal motion during the first three of four driving segments on Sol 2117. It completed about 10 rotations, then it stopped early in the fourth segment of the drive. Whether it will work again on future drives is uncertain.

The three wide-angle views shown one after the other in this animation come from Spirit's front hazard-avoidance camera. They were taken at different stages of the Sol 2117 drive. The most obvious change is in the position of shadows, a change unrelated to the wheel's movement during the drive. The frame with the rover arm's shadow farthest to the left is the first image in the sequence of three. The view is northward.The rover team began commanding extrication drives in November after months of Earthbound testing and analysis to develop a strategy for attempting to drive Spirit out of this soft-soil site, called "Troy." The extrication drives are expected to make slow, if any, progress in coming weeks, and the probability of success in escaping from Troy is uncertain.