Wind-Related Modification of Some Small Impact Craters on Mars

Abstract

Inferred wind-related modifications of impact craters are observed in the vicinity of the Mars Pathfinder (MPF) site and in other regions of Mars. Mars Obiter Camera (MOC) images show three types of inferred wind-modified morphologies for craters 0.3–1 km in diameter. Such modifications could be related to seasonal variations of the strongest winds and a possible paleowind regime. Geomorphic mapping of Big Crater at the MPF shows evidence of former aeolian modification of the crater rim and interiors similar to smaller craters in the area. The morphologic patterns are in good agreement with the results from the Mars Regional Atmospheric Modeling Simulation (MRAMS) of topographically forced wind circulation and atmosphere-surface interactions generated by flow over small craters. Simulations show that the maximum surface stress is on the downwind crater rim, consistent with inferred wind modification of the crater rim seen in MOC images. The trend of the inferred paleowind regime at the MPF site cannot be explained by a change in the global atmospheric circulation resulting from changes in Mars' obliquity. We suggest that this wind regime could be associated with a regional meteorological pattern that is not modeled by global scale circulation. An alternative explanation is that Mars' spin axis was in a different geographic position than it is at present.