Abstracts Category : Other

Ongoing Exhumation and Recent Exposure of Sedimentary Outcrops on Mars

by Joshua M Williams

Determining the habitability of ancient environments on Mars and their biosignature preservation potential is a primary goal of all recent Mars exploration missions. Because cosmogenic radiation destroys organic biosignatures at the Martian surface, freshly-exposed outcrops that have been previously protected by overburden provide potential sites where organic biosignatures could be observed. Scarp retreat is one common mechanism for exposing fresh outcrop surfaces. The absence of liquid water on Mars leaves aeolian processes to be the dominant eroding agent, and aeolian erosion drives scarp retreat by undercutting erosion-resistant cap rock that fails and breaks off from outcrops. This continual action creates bays and headlands. This study uses three methods to identify regions with freshly-exposed scarp surfaces using orbital images: (1) scarp orientation mapping; (2) identification of calved boulders; (3) identification of dust and drift deposition by color stretch analysis. These methods were consistent with surface observations from the Mars Science Laboratory (MSL) Curiosity rover in Gale crater. Scarp orientations in Gale crater show a distinct bay-signal (from the pattern of bays and headlands) that can be directly correlated with the known direction of ongoing aeolian scarp retreat. The bay-signal was also apparent at two of the Mars-2020 rover mission candidate landing sites: Eberswalde crater and Jezero crater. In a similar analysis of the Mars-2020 candidate landing sites Holden crater and Melas Basin, however, no clear bay-signal was identified. This work developed methods to detect recent scarp retreat on Mars and may provide a useful tool for identifying locations with high biosignature protection potential. Advisors/Committee Members: Rice, Melissa S., Clark, Douglas H., 1961-, Foreman, Brady.