Formation and evolution of crater rim alcoves and alluvial fans on Mars

Channels carved into planetary surfaces are a key record of tectonic, lithological, and climatic signals. On Earth, channel morphologies and longitudinal river profiles have been used to constrain histories of how landscapes respond to perturbations in base-level changes through upstream propagation of steep river reaches (i.e. knickpoints). On Mars, a suite of well-preserved deeply incised crater rim alcove basins, which source large alluvial fans, suggest a widespread episode of large-scale fluvial activity during the Late Hesperian/Amazonian epochs. We use a large dataset of CTX DEMs to extract longitudinal profiles of branching source networks for > 10 mid-latitude craters. Profiles tend towards similar concavities which fall within terrestrial values and have limited correlation to aspect, elevation, or latitudinal variation. The presence of multiple knickpoints may suggest variations in base-level, precipitation, or rock erodibility. Alcove and fan deposit volumes are predominantly aligned along N-S directions, supporting an origin from surface run-off generated by snowmelt. Combining estimates of snowmelt run-off with observed channel morphometrics, we derive a range of formation timescales for each channel system. We will combine these timescales with globally derived erosional parameters to calibrate 1- and 2-D models of alcove evolution and fan deposition, allowing us to constrain past fluvial environments and further our understanding of the climatic history and potential late-stage habitability of the Marian surface.