HOW ARE FANS BUILT UNDER A COLD AND ICY MARS CLIMATE SCENARIO?

Hesperian- to Amazonian-aged depositional features, such as alluvial fans, may represent one of the last wide-spread signs of fluvial activity on Mars' surface. As such, understanding the climatic conditions during the formation of these features may provide key insights on habitability and climate change on Mars.

Numerous studies have used morphometric parameters from terrestrial fan systems to differentiate between low rock-to-water fluvial processes and high rock-to-water inertial (debris flow) processes. This, combined with measurements of channel geometry, allow for the estimation of flow discharges, runoff rates, and total water volumes that likely built Martian fans. However, most terrestrial work has been conducted on alluvial fans that are in dry and arid locations where the source of water is from precipitation. This differs from the current hypothesis that most Martian fans sourced water only from their upslope catchments, likely from snowmelt, and perhaps under cold and icy conditions. Thus, there is a knowledge gap about the dominant processes and environment needed to build fans under cold and icy conditions, and importantly for Mars, a lack of understanding about the characteristic flow magnitudes (i.e., water volumes) during depositional events.

Here, we present initial results from a field-based terrestrial analog study where we characterized the sedimentology and geomorphology of periglacial alluvial fans in the Richardson Mountains, Northwest Territories, Canada. We qualitatively describe the range of sedimentary processes occurring on periglacial alluvial fans, as well characterize the influence of water-ice on fan dynamics. Lastly, we use a combination of remote sensing techniques (TLS, airborne LiDAR, drone-based LiDAR, and structure-from-motion) to determine whether periglacial alluvial fans have characteristic features recognizable at the scales at which remote sensing datasets of Mars are acquired.