Constraints upon the history of Meridiani Planum, Mars using sub-kilometer crater counting

Abstract

Analysis of a surface's crater population provides information to reconstruct the geologic history of a regional surface. Therefore, the population of sub-kilometer impact craters within Meridiani Planum, Mars has been assessed to constrain the nature and origin of unique hematite-rich deposits that occur in this region. Crater size-frequency distributions were compiled for 16,540 small craters in eleven images with varying hematite concentration. Results show that a complex crater obliteration process, probably aeolian activity, has operated continuously on the Meridiani region between 10 My and 3 Gy. More recently the surface process seems to have halted, possibly due to dune stabilization associated with a major climate shift. There is no evidence in the cratering record of an extensive, long-lived body of water that could have created the region's hematite deposits. While not required by the size-frequency distribution, some regional stripping and removal is permitted. In this case, the maximum erosional depth incurred in the last 3 Gy is limited to less than 50 meters. This is insufficient to have metamorphosed hematite as Lane et al. (2002) previously suggested. The size-frequency distributions suggest the hematite would have had to be emplaced very early in the history of Mars.