The search for evidence of life on Mars will require highly capable rovers. The strategy for the search for life divides into four major objectives: understanding the history of the Martian climate, finding evidence of chemical evolution, searching for evidence of past life, and searching for evidence of living organisms. To achieve these objectives, rovers will need to traverse distances of the order of 10 km to study a variety of relevant features (e.g., fluvial channels, shorelines, eskers, hydrothermal deposits) in sufficient detail to diagnose their formation processes. Requirements for rovers include color imaging at a range of spatial scales (wide angle for geologic context, high resolution for resolving millimeter- to centimeter-scale textures, submillimeter resolution of selected areas); in situ capabilities to perform chemical, mineralogical, and organic analysis; and the ability to collect samples of rocks, soils, and subsurface samples for return to Earth for detailed laboratory analysis. Simulations of rover missions to Mars and the Moon were performed for 3 days each in February 1995 using the Marsokhod rover deployed on Kilauea volcano, Hawaii, and operated via satellite communications from Moffett Field, California. During the simulations, science teams analyzed images taken by the Marsokhod and deduced the geologic setting and history of the field site. Imaging for the Mars mission simulation used mast-mounted monochrome stereo cameras with 30¿ field of view, 1.4 mrad/pixel resolution, 1.7 m height, 1 m horizontal spacing, and fixed pointing. A camera mounted on a manipulator arm was capable of resolving 1 mm features. During 18 hours of operation, the rover traversed 800 m of terrain, made observations at eight science targets, and obtained 52 stereo images and 18 arm camera images. For the lunar mission simulation, stereo cameras were mounted on a mast with a pointable platform at 1.5 m height and 10 cm horizontal spacing. Stereo color video was transmitted to mission operations. Command cycles with 1.5 s time delay allowed live teleoperation. In 15 hours of operation the rover traversed 1.2 km, and nine science targets were studied in detail. These experiments show that rovers can be used to successfully perform field geology on other planets. ¿ 1998 American Geophysical Union