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

Abstract

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 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 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)×AL(1.25±0.03). 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.