Creation Date: July 18, 1997
Mars Pathfinder: Sojourner & Yogi
Rover tracks lead to Sojourner, shown using its Alpha Proton X-Ray Spectrometer (APXS) instrument
to study the large rock "Yogi". Yogi, low in quartz content, appears to be more primitive than
Barnacle Bill, and appears more like the common basalts found on Earth. This image is the
clearest image yet of Yogi. It clearly shows the "two-toned" surface of this large rock. The
nature of this color difference is not known, however. It might consist of wind-blown dust
accumulated on the surface (the rock is leaning into the prevailing wind) or might be evidence of
a break from a larger boulder as it was deposited in the ancient flood that scoured this area.
The tracks and circular pattern in the soil leading up to Yogi were part of Sojourner's soil
mechanics experiments, in which varying amounts of pressure were applied to the wheels in order
to determine physical properties of the soil. During its traverse to Yogi the rover stirred the
soil and exposed material from several centimeters in depth. During one of the turns to deploy
Sojourner's Alpha Proton X-Ray Spectrometer, the wheels dug particularly deeply and exposed white
material. Spectra of this white material show it is virtually identical to the rock "Scooby Doo",
and such white material may underlie much of the site.
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 IMP was developed by the
University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the
PLEASE NOTE THE ACTUAL IMAGE AREA IS ABOUT TWICE AS LONG AS IT IS HIGH. For example an 8x10 inch
print will have a 5.5 x 10 inch image area.