We have mapped thermal inertia at high resolution for selected regions of Mars that are of potential biological relevance, using observations made by the Mars Global Surveyor Thermal Emission Spectrometer. Thermal inertia is a direct indicator of physical properties of the surface at the decimeter-to-meter scale. Our goal is to understand the geological processes by which the sites formed and their subsequent evolution, their current state, and their safety and science potential as landing sites for future lander, rover, and sample-return spacecraft missions. The thermal inertia values at ~3-km scale for the sites considered span the entire range of values measured at Mars; thermal inertias range from low values indicative of substantial aeolian mantling up to high values suggesting surfaces covered predominantly with bedrock, exposed rocks or blocks, or well-indurated crusts. The highest thermal inertias correlate strongly with local morphology, while areas with intermediate and low thermal inertias generally show no such correlation. This suggests that selection of future landing sites will be plagued by a choice of a well-mantled site that is safe but less interesting scientifically versus an unmantled site that is more interesting scientifically but less safe. ¿ 2001 American Geophysical Union