Evidence for landslides in Sisyphi Cavi (Noachis Terra, Mars). Slope evolution and role of endogenous preparatory factors

The surface of Mars is characterized by the presence of numerous gravity-induced processes and mass movements with greatly variable sizes and peculiarities. Detailed geomorphological studies have recently made it possible to identify many landslide-like landforms along the slopes bordering pits of Sisyphi Cavi in Noachis Terra, the southern hemisphere of Mars. These pieces of evidence are generally characterized by extended trenches, sometimes associated with uphill- or downhill-facing scarps. In this study, the gravity-induced processes observed in this region of Mars, and especially those present in a closed pit of the eastern sector, are described for the first time. A quantitative stress-strain analysis was performed, and it excludes a type of deformation process that could invoke creep processes ("viscosity-driven") but rather favors instability induced by stress- perturbations in the slope more concentrated over time ("force-driven"). In particular, we performed a parametric analysis on both viscosity and stiffness parameters of the materials involved. It demonstrates that the time necessary for the rheological evolution of deformational processes associated with the observed landforms are compatible with genesis of short-term instabilities. This finding has significant implications for the origin of the depressed forms within and close to the study area, which are characterized by unstable slopes present at their edges. It is therefore not necessary to invoke the role of "viscosity-driven" creep processes to explain the origin of the shapes associated with the observed gravity-induced slope instabilities. The reported results drive towards a new interpretative scenario of morphological evolution of the widespread pits in the study area in terms of efficiency of endogenous processes (such as hypabyssal magmatism) which characterize the studied area of Mars, even if it is not possible to exclude the role of exogenous processes.