Analysis of a new geomorphological inventory of landslides in Valles Marineris, Mars

Abstract

We completed a systematic mapping of landslides in a 10⁵km² area in Tithonium and Ius Chasmata, Valles Marineris, Mars, where landslides are abundant. Using visual interpretation of medium to high-resolution optical images, we mapped and classified the geometry of 219 mass wasting features, including rock slides, complex/compound failures, rock avalanches, debris flows, and rock glacier-like features, for a total landslide area of A_LT = 4.4 ×10⁴km², 44% of the study area, a proportion larger than previously recognised. Studying the landslide inventory, we showed that the probability density of landslide area p (A_L) follows a power law, with a scaling exponent α = - 1.35 ± 0.01, significantly different from the exponents found for terrestrial landslides, α = - 2.2 and α = - 2.4. This indicates that the proportion of large landslides (A_L >10⁷m²) is larger on Mars than on Earth. We estimated the volume (V_L) of a subset of 49 deep-seated slides in our study area and found that the probability density of landslide volume p (V_L) obeys a power law trend typical of terrestrial rock falls and rock slides, with a slope β = - 1.03 ± 0.01. From the combined analysis of landslide area and volume measurements, we obtained a power law dependency comparable to a similar relationship obtained for terrestrial bedrock landslides, V_L = (1.2 ± 0.8) × A_L^{(1.25 ± 0.03)} . From the fall height H_L and run out length L_L of a subset of 83 slides unaffected by topographic confinement, we obtained the mobility index (Heim's ratio) H_L /L_L, a measure of the apparent friction angle of the failed materials, ϕ = 14.4 ° ± 0.4 °. Slope stability simulations and back analyses performed adopting a Limit Equilibrium Method, and using Monte Carlo approaches on failed and stable slopes, suggest that the large landslides in Valles Marineris were seismically induced.