Comparing landslides to fluidized crater ejecta on Mars

摘要

We use the Mars Global Surveyor and Viking data sets to compare and contrast the geomorphology of four large Martian landslides located in Valles Marineris to fluidized ejecta of seven fresh Martian craters located in Lunae Planum. Both mass movements have flowed over the Martian surface and possess characteristics seen in terrestrial mass movements. We combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints. Our purpose is to better understand the emplacement processes of both types of mass movements. Our geomorphic analyses are consistent with previous views that the large Martian landslides resemble large terrestrial long-run-out flows. The planar flow model supports this inference: Martian landslides probably flowed as a basal glide, where motion is limited to a narrow interface at the base of the mass movement. Geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide. Distal pronounced contiguous ramparts, however, resemble features akin to terrestrial debris flows. The cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement. This model suggests, as expected, a basal glide origin for the inner portions of the ejecta. Surprisingly, basal glide also best explains the topography of the distal ejecta ramparts.