In Situ Investigation of the Martian Surface: Quantification of Dust Coverages in Gale crater and Abrasion Marks in Jezero crater

Abstract

In situ measurements by Mars rover missions contribute to our understanding of surface geochemistry, past-depositional environments, and climate conditions that may have once supported life. Microscopic cameras capture high-resolution images of the surface allowing observations of contemporary surface and atmospheric processes. This thesis investigates microscopic images of rock surfaces to (1) measure the abundances of airfall dust covering horizontal surfaces in Gale crater, and (2) measure tool marks preserved in abrasion patches from Jezero crater. The research goals are to understand which variables are influencing surface deposits of airfall dust, and how target surface mineralogy is affecting tool mark preservation. Previous studies have relied on orbital measurements of atmospheric opacity to study the seasonal suspension of Martian dust. Chapter 4 includes the longest single recording of surface dust coverages to date (~6 Mars Years) and contributes to the few studies that have quantified dust abundance at the surface. Using methods developed by Schmidt et al. (2018), dust coverages from 697 Mars Hand Lens Imager (MAHLI) microscopic images ranged from 0.4% to 76.6% and mirrored the results from atmospheric studies. Results indicate dust coverages decline in proximity to active aeolian dune deposits and increase with elevation. Airfall dust coverages on rocks increase annually as Mars enters a New Year (Solar longitude, Ls, ~0) and gradually decrease towards perihelion (Ls 251ᵒ) when seasonal winds are strongest. To examine unweathered rock interiors, the Mars 2020 mission uses a rock abrader to remove ~10 mm of surface coatings and rinds. Operation complications including flaws in rock (e.g., cracks, vugs, and voids) and shifting of the outcrop during abrasion, have caused 5 failed abrasion attempts. To better understand how physical properties influence the abrasion process, radial abrasion marks preserved in 10 successful abrasion patches were measured, relating abundance to mineralogy. Targets rich in primary igneous materials (i.e., crater floor targets) preserve greater counts and shorter abrasion lengths, compared to softer, sulfate- and carbonate- cemented sedimentary materials (i.e., delta front targets). The observations and results from this study will hopefully improve the prodapt algorithm that controls drilling parameters during abrasion and prevent future failed abrasion attempts.