FLASH FLOODING ON MARS CAN BE LINKED TO LARGE FAULT SLIP EVENTS

Understanding natural hazards and their drivers on Mars is important for planning exploration activities. Jökulhlaups, ice-melt flash flood events, can be particularly dangerous. While linked to volcanic activity on Earth, it is possible that other rapid heating mechanisms could lead to ice melting and flooding on Mars. We investigated isolated channels on the slopes of Ogygis Rupes, a large thrust fault-related landform in the mid-latitudes of Mars to describe how these channels formed and the role that frictional heating due to fault slip played in their formation. We mapped the channels, collected quantitative (width, length, slope) and qualitative (morphological descriptions) data, and calculated discharge rates and total water volumes associated with channel formation. We then used MOVE Structural Geology Modeling Software to reconstruct slip events and estimate frictional heating produced during slip events. Assuming the heat could melt subsurface, interstitial ice, we estimated the volume of ice melt produced during slip events. We compared the total volume of water expected during flood events in the channels to volumes of water produced during slip events of various sizes. Mapping efforts described 72 channels and resulted in average discharge rates of 164,000 cubic meters per second and total volumes of ~4.87E9 cubic meters. Channel morphology such as low depth-to-width ratios, linear channel-parallel boulder berms, and large isolated boulders all implied rapid flooding. These discharges and volumes corresponded to slip magnitudes of ~28 m, large slips that would only be expected on mature thrust fault-related landforms. Ogygis Rupes is one of the largest of such landforms observed on Mars and formed due to a total slip of 2,850 – 6,292 m along its associated fault plane. Water volume per flood event estimations are consistent with the total volume estimations needed to carve the channels over the lifetime of the fault, derived from erosion rates and total eroded rock removed from channels. Results indicate that only mature faults are capable of both (1) melting enough subsurface ice and (2) transporting the water to the surface to result in flooding, explaining why this impressive phenomenon remains a rare but important hazard of which to be aware during planning exploration and settlement of Mars.