INVESTIGATING THE ORIGIN OF CENTRAL MOUNDS ON MARS

Central mounds on Mars are observed as sedimentary deposits within crater interiors, but the specific processes responsible for their formation and subsequent modification are still debated. The deposits are hypothesized to have been created by either subaerial or subaqueous processes through one of two general formation mechanisms. The prevailing hypothesis suggests that after their craters were formed, sediment filled the entire crater and was later eroded into the morphologies we observe today. Alternatively, the sediment could have been deposited as the features we observe today without any significant erosion contributing to their mound shape.

Gale crater, the landing site for the Mars Science Laboratory Curiosity rover, is an example of a crater containing a central mound. Gale’s mound, Mt. Sharp, rises ~ 5 km above the crater floor and contains layered sediment that could preserve a record of early Martian climate and habitability. In order to place new discoveries at Gale crater into a global context, however, it is necessary to understand how Mt. Sharp relates to the entire population of central mounds.

We conduct a survey of central mounds that occur within craters larger than 25 km in diameter located between ± 60° latitude on Mars. We use mound locations, mound offsets within their host craters, mound heights, and details of mound morphology from imaging data sets to address various mound formation hypotheses. Our study reveals that most mounds are offset from the center of their host crater in the same direction as the regional winds. For example, the mounds in Arabia Terra are offset towards the western portion of their craters. This observation is consistent with wind erosion being the dominant method of erosion of sedimentary basin fill to form crater central mounds. Finally, we consider how these results compare to previous studies of Martian sedimentary deposits and whether we can place further constraints on the processes that deposited central mound sediments.