Active Boulder Falls in Terra Sirenum, Mars: Constraints on Timing and Causes

International audience; We use time series images to identify significant active boulder falls in an impact crater on Mars. Evidence for active boulder falls include boulder trails with impact marks from bouncing and rolling, and dark patches from boulder impacts away from the base of the crater walls. We were able to define three time periods with active boulder falls and additional slope streak formation, for which we refined the most significant activity to a time period between January 2012 and March 2013. A search of 236 images within 500 km of the study site identified two further sites with similar, but reduced, activity during the same time period. We discuss plausible mechanisms for the boulder fall activity, and conclude that the local geology and crater age is likely to be of significant importance. Our method of identifying and highlighting such activity will allow further studies of active surface processes on Mars.