To the millions of people glued to their televisions last Fourth of July, the Pathfinder mission to Mars was a resounding success. It gave them expansive views of a rock-strewn, undulating terrain washed billions of years ago by a flood of Noachian proportions, dust-laden pink Martian sunrises, and images—sometimes comical—of the Sojourner rover ambling like an Erector toy from rock to rock. The probe even sent Martian weather reports: there was a deep chill in the summer air and the dust devils were out.