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This two-frame mosaic of images from Mars Pathfinder's camera shows the Sojourner rover after driving onto the Martian surface. When this event occurred late on the night of July 5, 1997 (Pacific Daylight Time), Sojourner became the first autonomous robot to traverse the surface of Mars.
During the trip from Earth to Mars, which began December 4, 1996, and ended July 4, 1997, the rover remained firmly attached to one of the lander's petals. Once on Mars, the lander opened its petals, and the lmager for Mars Pathfinder (IMP) camera photographed the rover and the surrounding "marscape." After commanding the lander to lift the rover's petal to clear some airbag material, the rover team at the Jet Propulsion Laboratory determined that the terrain on each side of the petal was acceptable tor a safe rover rolloff down one of the ramps.
Sojourner was then released from the lander petal and rose up to her full height. Both ramps were successfully deployed, but the end of the forward ramp did not actually touch the planet's surface. Because of the better view of the rear ramp and the interesting rocks and soil that could be seen. the team elected to roll Sojourner backwards off the rear ramp. The end of the ramp can be seen at lower left.
The ramps get their shape and strength from sheets of metal that were flattened into tight rolls. After their restraints were cut, they assumed their original tubular shape and became rigid. The rover's wheels, three on each side, straddled the outside of each tube so that Sojourner would not tip or turn.
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Under power from its electric motors, Sojourner six-wheeled down the ramp and onto the soil of Mars. The "rocker-bogie" suspension system was immediately put to the test. As the far set of wheels (at left in the picture) left the ramp, they encountered a small rock. The suspension system neatly carried the rover over the rock, as can be seen by the wheel tracks on the fine surface material. The tracks run trom the end of the ramp for a few centimeters, abruptly end, and continue on the far side of the rock where the wheel stopped. No such obstacle was encountered by the other set of wheels, but traveling over the rock did cause the rover to fishtail slightly and turn a bit to the lett.
The dark surface on top of Sojourner is her solar panel, which, along with non-rechargeable batteries, provides electrical power for her operation. The rover measures 65 centimeters (2 feet) long, 48 centimeters (1.5 feet) wide, and 30 centimeters (1 foot) tall. On Mars she weighs 4 kilograms (8.8 pounds) compared to 10.5 kilograms (23 pounds) on Earth.
The shadow of the rock known as Barnacle Bill, the first rock studied by Sojourner, can be seen in the upper left corner. Patches of very fine-grained material can be seen on either side of the rover. Below Barnacle Bill there are a number of small pebbles with streaks of material trailing off to the left. At some point, perhaps during one of Mars' periodic dust storms, winds blew across this surface trom right to left, depositing dust finer than talcum powder on the wind-shadowed side of the pebbles. Mars Pathfinder has observed variable wind speeds and directions; these winds will eventually alter or erase Sojourner's tracks.
This image and additional information about the Mars Pathfinder mission can be found on the Internet at: http://mpfwww.jpl.nasa.gov
The Mars Pathfinder mission is part of a long-term program of Mars exploration being conducted by NASA's Office of Space Science. The Jet Propulsion Laboratory, an operating division of the Calitornia Institute of Technology, manages the Mars Exploration Program tor NASA.
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