Mapping and Characterization of Martian Intercrater Bedrock Plains: Insights Into Resurfacing Processes in the Martian Cratered Highlands

摘要

We have produced a map of the Martian highlands that identifies and delineates flat, areally expansive regions of lithified material (bedrock plains) using orbit-based thermal measurements. We performed morphological and spectral analyses to infer their mechanical properties and determine compositional differences from the surrounding unlithified materials. We tested a previously noted relationship between bedrock plains and olivine spectral detections with quantitative olivine abundance modeling. Finally, we created a catalogue of process-related landforms (e.g., layering, sinuous ridges, and raised lobate surfaces) associated with bedrock plains. These investigations were used to interpret potential bedrock plain origins. We found that bedrock plains commonly contain multiple morphologically and spectrally distinct subunits. Many bedrock plain surfaces are moderately to heavily degraded, with an apparent susceptibility to aeolian erosion. These properties are consistent with friable clastic materials. Bedrock plains are generally basaltic in composition. They are compositionally distinct from their surroundings, in nearly all cases due to variations in mafic mineralogy. Olivine enrichments associated with bedrock plains are common but not ubiquitous. Olivine enrichments within plain subunits were typically less than 10% above the surrounding, unlithified surface materials. These enrichments could have arisen from mineral fractionation processes during the bulk transport and erosional deflation of clastic materials. Some bedrock plains show strong evidence for fluvial deposition, especially in the Terra Sabaea region. Finally, in addition to clastic bedrock plains, a cluster of bedrock plains in central Terra Cimmeria contain subunits that show evidence for emplacement via effusive volcanism.