Mars Laboratory Analog Sediment Flows: Investigating the Effects of Composition

Decades of Mars observations have provided strong evidence for past transport of sediments by surface liquid water. Different properties can affect the behavior of sediment-water flows, including pressure, temperature, gravity, and sediment composition. Previous studies show that mudflows (water and bentonite clay) at modern Mars pressures of 7 mbar and certain temperatures behave similarly to pahoehoe lava flows, and that boiling, levitation, and grain sputtering can be active processes affecting deposit morphology and run out distance. Further experimental studies are needed to constrain how sediment composition may affect the magnitude of these processes at pressures more analogous to early Mars (³100 mbar). Constraining this information is important as deposit properties are commonly used to reconstruct past martian surface processes and hydrology.

Our work builds upon previous studies by performing Mars analog sediment transport experiments of liquid water mixed with sediments of varying compositions (basalt, kaolinite, bentonite, and MGS-1 regolith simulant). We conducted the experiments at a pressure chamber at the Open University, U.K., by pouring regolith-water mixtures (blended inside chamber) over a 10° test bed of either warm unconsolidated sand or frozen sand to simulate different martian surface conditions. We also varied the chamber pressure (5 mbar to 1014 mbar) and temperature (247 K, 293 K), and water-rock ratios (ranging from 30:70 to 80:20). For each run, videos were taken of the flows to document their morphological evolution down the test bed. Final deposit morphologies were documented with a DSLR camera, and these images were used to make surface models using the Agisoft Metashape photogrammetry software. The surface models are used to determine deposit morphologies such as volume, slope, and surface roughness.

Results from this study will provide a framework for characterizing martian sedimentary deposits and landforms of varying compositions that formed under changing pressure and temperature conditions. This framework is necessary for constraining Mars' paleohydrology, climate, and habitability. Experiments using the MGS-1 Mars bulk regolith simulant are particularly relevant for studies of current Mars processes and future human and robotic exploration activities.