35. Mars Pathfinder

Mars Pathfinder restarted the U.S. exploration of Mars. Pathfinder was launched at 2 a.m. on December 4, 1996, and landed on Mars on July 4, 1997 on a flat plain just outside a huge river channel, Ares Vallis. Pathfinder’s main purpose was to test new technologies for use in future Mars missions. After a seven-month cruise from Earth, Pathfinder entered Mars’ atmosphere on a direct approach trajectory. Its aeroshell and parachute first slowed it down from orbital velocity, and then the lander itself dropped to the surface, cushioned by inflated airbags. After landing, the airbags deflated and were pulled out of the way, and the lander will open up like a three-petaled flower; the center was the control and radio assembly, and each “petal” was a solar cell electrical panel.

From the center of the “flower,” a pop-up mast lifted a stereo camera, the Imager for Mars Pathfinder, to 1.5 meters above the surface. Also on the spacecraft body was a small weather station called the ASI/MET. On one of the “petals” was stowed a small rover, called Sojourner; it rolled off the petal and began investigating the rocks and soil of Ares Vallis. Sojourner had cameras front and back to help it investigate rocks and avoid them while moving, and carried the Alpha Proton X-ray Spectrometer (APXS), which determined the elemental composition of rocks and soils. Pathfinder scouted for geologically interesting rocks looked particularly for rocks washed down from ancient terrain that may be similar to martian meteorite ALH 84001.

Pat Rawlings, SAIC, for NASA; P-46480

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