THE MARS PATHFINDER MISSION

Mars Pathfinder, one of the first Discovery-class missions (quick, low -cost projects with focused science objectives), will land a single sp acecraft with a microrover and several instruments on the surface of M ars in 1997. Pathfinder will be the first mission to use a rover, carr ying a chemical analysis instrument, to characterize the rocks and soi ls in a landing area over hundreds of square meters on Mars, which wil l provide a calibration point or ''ground truth'' for orbital remote s ensing observations. In addition to the rover, which also performs a n umber of technology experiments, Pathfinder carries three science inst ruments: a stereoscopic imager with spectral filters on an extendable mast, an alpha proton X ray spectrometer, and an atmospheric structure instrument/meteorology package. The instruments, the rover technology experiments, and the telemetry system will allow investigations of th e surface morphology and geology at submeter to a hundred meters scale , the petrology and geochemistry of rocks and soils, the magnetic prop erties of dust, soil mechanics and properties, a variety of atmospheri c investigations, and the rotational and orbital dynamics of Mars. Lan ding downstream from the mouth of a giant catastrophic outflow channel , Ares Vallis at 19.5 degrees N, 32.8 degrees W, offers the potential of identifying and analyzing a wide variety of crystal materials, from the ancient heavily cratered terrain, intermediate-aged ridged plains , and reworked channel deposits, thus allowing first-order scientific investigations of tile early differentiation and evolution of the crus t, the development of weathering products, and the early environments and conditions on Mars.