English: In this view from behind a test rover at NASA's Jet Propulsion Laboratory, Pasadena, Calif., the rear wheels of the rover are turned toward the left, and the left-front wheel is turned toward the the right. Bruce Banerdt, project scientist for Spirit and Opportunity, measures the rover's position before the rover receives commands to drive a forward right arc.

The experiment was designed to assess whether this maneuver could pivot the rover around the immobile right-front wheel, since the right-front wheel on NASA's rover Spirit has been inoperable for more than three years.

This work on July 15, 2009, was part of a series of tests at JPL designed to determine the best way to get Spirit out of a Martian patch of soft soil called "Troy," where Spirit's wheels have dug in. The test setup, in a box that team members are calling the dustbin, simulates the situation at Troy. The box holds about 2.7 tons of a powdery mixture of diatomaceous earth and fire clay. This material has physical properties similar to the soil at Troy. The top surface is sloped at 10 degrees.