The clouds on this HRSC image have been interpreted as small local dust storms aligning perpendicular to the troughs. Local dust storms were also frequently observed in THEMIS and HiRISE data, especially at the equator-facing walls of the polar troughs. This kind of dust mobilization could facilitate scarp erosion and retreat. Both sublimation and katabatic wind erosion seem to be important active eolian processes responsible for the long-term modification of the trough walls.