Mars Exploration Rover team members prepare a testing setup for a subsequent experiment after an experiment driving the rover in a crablike motion, with all four corner wheels angled to the right. Clockwise from top: Scott Maxwell, Pauline Hwang, Kim Lichtenberg.

This work on July 9, 2009, was part of a series of tests at NASA's Jet Propulsion Laboratory, Pasadena, Calif., designed to determine the best way to get NASA's Spirit rover 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.

To see updates on the efforts to free the Spirit rover, visit the JPL Free Spirit website.