Laboratory Investigations of Flow Dynamics and Volume Growth During Erosion of Different Substrates by CO 2 ${\text{CO}}_{2}$ -Driven Granular Flows in Martian Gullies

Gullies are actively changing landforms on planet Mars. The prevailing hypothesis, supported by a suite of different studies, states that present-day activity in these gullies is caused by fluidized granular flows driven by the sublimation of seasonal ${\text{CO}}_2$ ice. However, the long-term formation process of gully landscapes is a contentious issue as water-driven debris-flow processes could easily explain erosion. In contrast, we do not know if ${\text{CO}}_2$-driven granular flows can cause a significant amount of erosion. In this study, we conducted flume experiments investigating the flow dynamics and erosion capacity of ${\text{CO}}_2$-driven granular flows under different substrate and flow settings. Our experiments show that ${\text{CO}}_2$-driven granular flows under Martian conditions are efficient erosive agents, which can erode and entrain large volumes of unconsolidated material in various environmental (i.e., substrate and flow) settings. In general, erosion and entrainment enhance the mobility of ${\text{CO}}_2$-driven flows. However, the frost and thermal conditions of the slopes and the flow composition determine the erosion efficiency of these flows. Finally, based on terrestrial debris-flow erosion theory we estimate that collisional forces at the base of ${\text{CO}}_2$-driven flows can also cause erosion of more consolidated material such bedrock, permafrost or Latitude Dependent Mantle.