The Martian Dust Bowl: Thermal Inertia in Sediment-Filled Craters Reveals a Noachian Dry Spell

Abstract:

Despite decades of satellite observations of the surface of Mars, there remains a widespread class of geologic features we don’t yet fully understand. Layered sedimentary deposits in Mars’ low latitudes are thought to contain some of the best-exposed records of late Noachian surface environments on the planet, but the role of water in their formation and whether those depositional processes were localized or widespread remain uncertain. Elevated thermal inertia (TI) values in many layered deposits, relative to the surrounding units, were once thought to indicate high cohesion, consistent with localized aqueous induration in pools or lakes. However, prevalent erosional landforms suggest that many of these deposits are actually more friable than both underlying and overlying units with lower TI values. This apparent contradiction might be explained by variations in dust cover associated with erodibility, with dust preferentially accumulating on more indurated surfaces. In this work, we pair TI derived from Thermal Emission Imaging System (THEMIS) nighttime infrared imagery with Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) hyperspectral visible and near-infrared data, modeled surface winds, and observations of aeolian erosion patterns (yardangs, crater densities, dune forms and wind streaks) in order to estimate deposit cohesion and constrain possible depositional origins of layered sediments in ten Arabia Terra craters. We quantify the effects of dust and wind on apparent TI in the region, relate those effects to deposit mechanical properties, and highlight how consistently low cohesion in these deposits, along with rhythmic bedding patterns and draping geometries, suggest there was a period of widespread dry and dusty conditions that seems to have punctuated wetter phases in Mars’ history. Our results are consistent with models for duststone formation on Mars, where Arabia Terra craters were once a sink for lofted dust, and episodic mild surface induration, perhaps linked to volatile diffusion during obliquity changes, produced the observed layering. Interpretations of the material properties of these deposits will be further tested using in situ observations from Curiosity and Perseverance rovers as they investigate similar layered sulfate deposits at Gale and Jezero craters.