Spatial and Temporal Relationships of Landslides in Valles Marineris, Mars: Constraints on their Triggering Mechanisms

The giant canyon system of Valles Marineris on Mars hosts the most concentrated landslides on the planet. Large landslides are preferentially distributed along the north wall of the Ius, Melas, and Coprates Chasmata (IMC), including a long stretch of the Coprates Chasma north wall where there is no major slide activity. There are four possible causes for the occurrence of these rotational landslides in Valles Marineris. (1) The IMC wall rocks are stratified with stronger material overlying weak material and undercutting of the weaker layer by erosion induced slope instability. (2) An episode of wet and warm climate could have also triggered the occurrence of widespread landslides that slip on nearly frictionless, water (or other medium)-lubricated surfaces. (3) A succession of concentric faults out from impacts may have triggered landslides. (4) Seismic activity along trough-bounding faults may have both enhanced the steepness of trough walls and triggered landslides, which may explain the preferential concentration of landslides along the north wall of the IMC. In addition to the above triggering mechanism, we note that the location and shape of the landslides are clearly controlled by trough-parallel pre-existing fractures, leading to the collapse of long strips of trough walls as seen in western Ius Chasma. The four competing causes make contrasting predictions on (a) timing of landslides (synchronous vs. diachronous) and (b) their spatial relationships to trough-bounding faults, nearby craters, and the strength of lithologic units comprising the trough walls. A systematic mapping of individual landslides is currently in progress to address the above issues.