Modelling Martian landslides: dynamics, velocity, and paleoenvironmental implications

Landslides on Mars exhibit features such as steep collapse, extreme deposit thinning, and long runout. We study the flow dynamics of Martian landslides particularly in Valles Marineris, where landslides are among the largest and longest. Firstly, we observe that landslides in Valles Marineris share a series of features with terrestrial landslides fallen onto glaciers. The presence of suspected glacial and periglacial morphologies from the same areas of Valles Marineris, and the results of remote sensing measurements suggest the presence of ice under the soil and into the rock slopes. Thus, we explore with numerical simulation the possibility that such landslides have been lubricated by ice. To establish a plausible rheological model for these landslides, we introduce two possible scenarios. One scenario assumes ice only at the base of the landslide, the other inside the rock-soil. A numerical model is extended here to include ice in these two settings, and the effect of lateral widening of the landslide. Only if the presence of ice is included in the calculations, do results reproduce reasonably well both the vertical collapse of landslide material in the scarp area, and the extreme thinning and runout in the distal area, which are evident characteristics of large landslides in Valles Marineris. The calculated velocity of landslides (often well in excess of 100 m/s and up to 200 m/s at peak) compares well with velocity estimates based on the run-up of the landslides on mounds. We conclude that ice may have been an important medium of lubrication of landslides on Mars, even in equatorial areas like Valles Marineris.