PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

PHOTO CAPTION                 MRPS #80911                               
                              July 5, 1997  (Sol 2) 
                              Rover touchdown on Martian surface

     This picture taken by the IMP (Imager for Mars Pathfinder) aboard 
the Mars Pathfinder spacecraft depicts the rover Sojourner's 
position after driving onto the Martian surface. Sojourner has 
become the first autonomous robot ever to traverse the surface of 
Mars. This image reflects the success of Pathfinder¹s principle 
objective -- to place a payload on Mars in a safe, operational 
configuration.

     The primary mission of Sojourner, scheduled to last seven days, 
will be to use its Alpha Proton X-ray Spectrometer (APXS) 
instrument to determine the elements that make up the rocks and 
soil on Mars.  A full study using the APXS takes approximately 
ten hours, and can measure all elements except hydrogen at any 
time of the Martian day or night. The APXS will conduct its 
studies by bombarding rocks and soil samples with alpha particle 
radiation -- charged particles equivalent to the nucleus of a 
helium atom, consisting of two protons and two neutrons.

     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.  

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