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

We completed a systematic mapping of landslides in a 105 km2 area in Tithonium and Ius Chasmata, Valles Marineris, Mars, where landslides are abundant. Using visual interpretation of medium to highresolution 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 ALT = 4.4 × 104 km2, 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(AL) 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 (AL > 107 m2) is larger on Mars than on Earth. We estimated the volume (VL) of a subset of 49 deep-seated slides in our study area and found that the probability density of landslide volume p(VL) 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, VL = (1.2 ± 0.8) × A(1.25±0.03) L . From the fall height HL and run out length LL of a subset of 83 slides unaffected by topographic confinement, we obtained the mobility index (Heim’s ratio) HL/LL, 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.