Megaflood Duration from Bedform Pattern Disequilibrium in Outflow Channels of Mars

Planetary-scale outflow channels were carved by catastrophic floods flowing into Mars’ northern lowlands, inspiring the hypothesis that they may have fed oceans. However, the sizes and durations of these catastrophic events remain highly debated.  To estimate flood discharge, previous studies have typically assumed that canyons were filled to the brim with water, ignoring the progressive deepening of gorges as floods carve into bedrock. As a result, discharges are grossly overestimated and estimated flood durations are unrealistically short. To improve upon previous estimates, we develop a new approach to estimating flood duration that is grounded in sediment-transport mechanics and bedform morphodynamics. First, we validate the approach at a well-documented terrestrial analog site - giant gravel ripples in the Channeled Scablands of Washington, USA. Second, we apply the new framework to a field of multi-meter dunes along the bed of Athabasca Valles, Mars. Our results provide an independent constraint on the duration of the floods that carved the Outflow Channels and bear significance to our understanding of the sources and lifetime of potential early oceans on Mars.

Speaker: Claire Blaske, Stanford University

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Room 350/372