Quantifying the Channel Networks of Fan-Shaped Landforms on Mars

            River deltas and fluvial fans are both fan-shaped landforms that contain complex channel networks. Fan shaped landforms have also been identified on Mars at Jezero, Eberswalde, and Gale craters among many other locations. A principal distinction between these two landforms is that only deltas systematically form along the shorelines of a standing body of water. Fluvial fans may form along a body of water, but can also form hundreds of kilometers inland. It is thus crucial to be able to accurately distinguish between deltas and fluvial fans for the purposes of mapping paleo-shorelines on planetary bodies and understanding paleoclimates. In this work, we apply multiple quantitative methods on Martian fan-shaped landform channel networks to map channel networks to differentiate fluvial fans from river deltas on Mars. We quantify differences in channel bifurcation and divergence angles due to channel crossovers. We also measure changes in channel reach length between bifurcation and divergence nodes. Differences in channel networks occur because fluvial fans are built by channel bed aggradation and channel avulsion. River deltas are constructed by both mouth bar growth and consequent channel bifurcations, as well as infrequent avulsions. In river deltas on Earth, channel bifurcations form at an angle of approximately 72°. Channel lengths and widths in river deltas decrease downstream with increases in successive channel bifurcations. On the contrary, fluvial fan avulsions generate smaller divergence angles and down-fan channel narrowing is not necessarily linked to divergence nodes. This project applies Earth derived channel network mapping techniques to Martian fan-shaped landforms and demonstrates that this methodology is applicable on Mars. Preliminary analysis of the channel network of the Jezero crater landform suggests that it resembles a fluvial fan and not a delta. Conversely, preliminary analysis of the Eberswalde crater channel network suggests that the landform here does resemble an Earth river delta. Our results indicate that fan-shaped channel networks can and must be carefully assessed. This is especially true if the presence of deltas is used for the estimation of the location of paleo-shorelines on planetary bodies, as only deltas regularly form at shorelines. Alternatively, additional evidence is required to identify paleo-shorelines as fluvial fans may also form along shorelines. On Earth, fluvial fans are less sensitive to sea-level rise and coastal hazards than deltas and thus react differently from deltas due to changing sea levels.