Features similar to honeycomb weathering are observed in some Martian rocks at the Pathfinder landing site. Honeycomb weathering on Earth develops in a range of environments, including extremely arid and cold areas in Antarctica, and on many types of rocks, e.g. basalts and andesites, subjected to physical and/or chemical weathering. Salt weathering, in combination with frost shattering and chemical weathering, provides a viable explanation for the development of honeycomb features on Mars under current environmental conditions. Data supporting this theory are presented and discussed. These findings are important in understanding the present climate, geology, and, in particular, the geomorphology of Mars. They also suggest new paths for research and experimentation in future missions to Mars. ¿ 1998 American Geophysical Union