Formation and erosion of layered materials: Geologic and dust cycle history of eastern Arabia Terra, Mars



[1] Eastern Arabia Terra is mantled in a layer of dust a few centimeters to a meter thick, yet contains morphologic features that suggest a history of multiple events of deposition and consolidation of fine-grained material and a significant amount of erosion. Early in Martian history, this region was affected by volcanic and fluvial activity but has since been dominated by aeolian processes. Five craters in this region contain interior mound material that ranges in height from 1600 to 2100 m above the crater floor. The fluted erosional pattern and the thermal inertia are suggestive of a weakly indurated material, and the extensive layering implies that these mounds were formed by a repeated process or processes. Although these materials primarily occur within craters, there are materials outside craters that have similar erosional features and fine laminations, suggesting a more extensive deposit. The most likely process to form this material is the deposition and cementation of air fall dust and is potentially related to Martian obliquity changes. The significant amount of erosion of the intracrater mounds unit indicates a dramatic change from a depositional environment to an erosional regime over the past 106–108 years. Currently dust is accumulating in this region in years with planet-encircling dust events, but global circulation model results indicate that dust devils may be removing slight amounts of dust from Arabia Terra. These observations suggest that the thickness of the dust mantle may not be currently increasing and may instead be in equilibrium.