Position Markers in Preparation for Test

Mars Exploration Rover team members at NASA's Jet Propulsion Laboratory, Pasadena, Calif., prepare an experiment on July 13, 2009, for assessing how a test rover moves when embedded in loose soil and commanded to drive backward with wheels turned.Engineers checking possible rover movements to get Spirit out of the "Troy" sand trap on Mars are evaluating how a comparable rover at JPL fares in a