Planners feel the microscopic formations in Mars meteorite ALH84001, found in Antarctica, and the highly diverse samples of rocks believed to have been strewn about by ancient rivers seen at the Mars Pathfinder landing site, provide a strong motive for sending human exobiologists and geologists to the Red Planet. This artist's rendering depicts two such scientists. Unlike the meteorite, the sedimentary deposits evident in recent Mars Global Surveyor images could contain fossils visible under ordinary magnification, according to many scientists.