Valley floor aeolianite in an equatorial pit crater on Mars

High and low albedo lineations in a valley entering a pit in Lucaya crater are overlain by a currently immobile dune field. We propose that they are an aeolianite that formed as the overlying dunes migrated. Implicit in this is the suggestion that available water promoted early cementation of evaporitic minerals. We propose that the deposit likely resulted from a combination of locally sourced carbonate minerals and transient groundwater, both of which were made available after the formation of the pit crater. We do not exclude other aerial or subsurface sources of soluble minerals. We report on a pilot regional reconnaissance of images that finds the alternating albedo of dune sediments in Lucaya crater is found elsewhere on Mars. This suggests a regional sediment source at the time of dune activity. We examine a coastal interdune site in Namibia as an analogue for early geochemical cementation and interdune microtopography similar to the features observed on Mars. We find that the curvilinear interdune strata at the field site in Namibia are the preserved lee slope facies deposited by the dune as it migrated. Early cementation occurs in the interdune vadose zone due to precipitation of salts from groundwater. The formation of aeolianite in Lucaya crater supports suggestions by others that moisture is available for a significant period following crater formation. Moreover, it suggests that groundwater flow is sustained near the surface as well as in the deeper subsurface