The image was taken by the Imager for Mars Pathfinder (IMP) on Sol 4. The rover Sojourner has traveled to an area of soil and several rocks. Its tracks are clearly visible in the soft soil seen in the foreground, and were made in part by the rover's material abrasion experiment. Scientists were able to control the force of the rover's cleated wheels to help determine the physical properties of the soil. In this image, Sojourner is using its Alpha Proton X-Ray Spectrometer (APXS) instrument to study an area of soil. Sunlight is striking the area from the left, creating shadows under Sojourner and at the right of local rocks. The large rock "Yogi" can be seen at upper right.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

Photojournal note: Sojourner spent 83 days of a planned seven-day mission exploring the Martian terrain, acquiring images, and taking chemical, atmospheric and other measurements. The final data transmission received from Pathfinder was at 10:23 UTC on September 27, 1997. Although mission managers tried to restore full communications during the following five months, the successful mission was terminated on March 10, 1998.