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

We completed a systematic mapping of landslides in a 10 5 km 2 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 × 10 4 km 2 , 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 > 10 7 m 2 ) 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 (Heimʹs 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.