Abstract: Within the Valles Marineris region on Mars, a huge system of interconnected valleys interpreted as flood channels reveals the presence of braided channels and strong incisions into the bedrock. We focus our study on Ganges Chasma, where two examples of outflow channels lie on the Valles Marineris plateau and take source in depressions. These channels may represent good examples for studying the relationship between the formation of Chasmata and outflow channels. No mass deposition is observed at the mouth of both channels, indicating that outflows were active before the opening of Ganges Chasma. In addition, possible sapping valleys were formed at the mouth in both cases. Residual aquifer could have been responsible for a late hydrogeological activity in this region after the opening and the widening of Ganges Chasma. From these observations and our flux calculations, we concludet hat overpressure due to dyke ascent could have initiated outflows on Valles Marineris plateau, which is consistent with previous studies. Our results suggest that these mechanisms played a role in the opening and the widening of the Chasmata around 3 to 3.5 Gy.

Abstract: Recent experiments on dry granular flows over horizontal plane bare some similarities with large Martian landslides observed in Valles Marineris (VM). However, Martian normalized runout are twice as large as those that observed in dry granular flow experiments. Numerical simulations on theoretical 2D and real 3D topographies reconstructed from remote sensing data show that slope effects significantly reduce the shift between experimental results and Martian observation. However, topography effects are not strong enough to explain the high mobility of Martian landslides. As a result, other physical and/or geological processes should play a key role into the dynamics of Martian landslides. A new mobility is defined that makes it possible to characterize the dynamics of the flow regardless of the geometry of the released mass and of the underlying topography.