Exploring the Jau Crater Cluster, Gale Crater, Mars

Abstract

The Jau crater cluster on the north flank of Mt. Sharp in the Gale crater consists of 20–30 simultaneously formed impact structures. The craters are ∼2 to ∼25 m across (generally increasing in size from the ESE to WNW). Using Digital Terrain Models derived from orbital and rover orthomosaics of two of the larger craters, we evaluated the amount and processes of degradation based upon current versus expected original crater morphology. We conclude that the craters in the cluster are the result of a fragmenting primary impactor and that predominantly aeolian degradation at these two craters is responsible for ∼1–2 m wall back-wasting, 10s of cm of infilling by aeolian drift, and 20–40 cm rim lowering. Other craters in the cluster experienced similar degradation whose expression varied according to crater size: smaller-scale morphology at smaller craters is more modified by a given amount of erosion. Prevailing winds erode the downhill, NNE side of the craters more though raised rims persist at the larger craters. An estimated vertical erosion rate of 0.1 m/Myr and a horizontal erosion rate of several m/Myr predicted by others appear most consistent with the Jau crater morphology and setting relative to erosion estimates for elsewhere in Gale crater and other Mars landing sites. Factoring in uncertainties in our estimates, these rates are broadly consistent with the scale of erosion inferred for the evolution of larger, older features on Mt. Sharp and suggest that the cluster-forming impact occurred one to a few and less than ∼5 Ma.