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Gravity-Driven Differences in Fluvial Geomorphology Between Earth and Mars

Presentation #212.05 in the session Martian Geomorphology, Ice Layers, Crust, and Habitability (Poster + Lightning Talk)

Published onOct 23, 2023
Gravity-Driven Differences in Fluvial Geomorphology Between Earth and Mars

Preserved geomorphological landforms on the surface of Mars indicate the presence of abundant liquid water in the early history of Mars. Many of these geomorphic features were developed by erosion and deposition of sediments by water. It is therefore important to understand how fluvial sediment transport works on Mars and how it is different from Earth. Due to the lower gravity on Mars water flows down slope with less energy, resulting in lower bed shear stresses and flow velocities. Nonetheless, fluvial sediment transport is more efficient. Due to the lower gravity the mobility of the sediment is higher. Larger grains are brought into motion and suspension (Komar, 1980; Burr et al., 2006) and the magnitude of suspended transport is significantly higher (Amy and Dorrell, 2021), as is the total transport rate (Braat et al., 2023). In addition, the settling of sediment is slower, resulting in larger transport distances on Mars compared to Earth. Based on the differences in entrainment due to gravity, different grain size mixtures are transported and settle out in a different manner (Braat et al., 2022). Therefore, the geomorphology and stratigraphy of geomorphic landforms might be different than we expect from Earth observations. In this study, we investigate how lower gravity impacts fluvial geomorphology on Mars through idealised modelling.

We use hydro-morphodynamic numerical modelling to investigate the gravity-driven differences on river and delta morphology between Earth and Mars. The model scenarios of Earth and Mars are idealised runs with exactly the same conditions except for gravity. The most important parameters we prescribe are initial bathymetry, water discharge and grain size. Our preliminary model outcomes indicate that transport on Mars is higher than on Earth for the same river discharge (which agrees with Braat et al., 2023), and therefore the landscape can change faster. The models also indicate higher suspension rates on Mars, the presence of fewer active channels, bigger channels, and less channel dynamics. It is also expected that Martian depositional slopes will be lower and levees height and floodplain sedimentation will be higher, however, this was not yet confirmed by the model outcomes due to too many model simplifications (e.g., constant discharge preventing flooding and the use of a single grain size). Adding more complexity to the model scenarios is part of our future work.

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