An exciting scientific component of the Pathfinder mission is the rover, which will act as a mini-field geologist by providing us with access to samples for chemical analyses and close-up images of the Martian surface, performing active experiments to modify the surface and study the results, and exploring the landing site area. Structures, textures, and fabrics revealed in the rover camera images will provide a bounty of geologic information, which can be put in the larger context of geologic features seen in lander camera images. Rover technology experiments will improve our understanding of soil properties (grain size, bulk density, friction angle, cohesion, and compressibility) by contributing information not provided by the other Pathfinder instruments. Unplanned opportunities and activities are also likely to provide valuable science information, such as examination of any slumped or eroded soil that has been piled up by the rover wheels, and examination of overturned rocks. Using its ability to actively explore and experiment, the rover will fill in key gaps in our understanding of the landing site.¿ 1997 American Geophysical Union