Atmosphere-surface interactions relating to ice-rich landforms in Lyot Crater, Mars

Foley, Lori-Ann; Lewis, Stephen; Balme, Matthew and Holmes, James (2022). Atmosphere-surface interactions relating to ice-rich landforms in Lyot Crater, Mars. In: 7th Mars Atmospheric Modelling and Observations Conference, 14-17 Jun 2022, Paris, France.



The amount of shadow cast on a landscape varies with, inter alia, latitude and topography, and when shadow is included in a climate model it can influence atmospheric variables such as surface temperature, wind speed and wind direction. This can in turn influence how the deposition and evolution over time of water, ice or snow are represented in models of martian surface-atmosphere interaction.

Surface features that appear to be heavily influenced by the atmospheric conditions and the location’s topography include viscous flow features (VFFs). Interpreted as debris-covered glaciers, they undergo a slow, plastic deformation due to gravity, resulting in the movement of ice and debris down the steep slopes on which they are preferentially found. Their evolution is distinct from other near-by ice-rich landforms that exist in different topographic settings. Characteristics of VFFs include evidence of flow around or over obstacles, surface lineations, compressional ridges, extensional troughs, and a lobate plan-view morphology. The causes of their distinctive morphology and location are linked to the atmospheric conditions they experience.

This study focuses on Lyot crater, Mars, a ∼215‐km diameter impact crater centered at 50.5°N, 29.3°E. The crater floor is ∼3000 m below the surrounding landscape and ∼7000 m below Mars Orbiter Laser Altimeter (MOLA) datum, making it the lowest point in the northern hemisphere. It has a relatively young age, and is thought to have formed between the early Amazonian (1.6 Gyr) and the late Hesperian (3.4 Gyr ago). Lyot crater contains many geomorphological indicators of surface ice and ice melt, both past and present. Lobate features with convex-outward ridges and convex-upward profiles, identified as VFFs, can be seen predominantly in the south of the crater along the steep slopes of the crater rim and inner peak ring. VFF formation is believed to be temperature dependent and such slopes are largely shadowed, protecting the ice-rich landforms found there from sublimation due to solar insolation. Ridges found on the main body of the VFFs are interpreted as compressional ridges, indicating the ductile flow of material. The aim of this study is to use a high resolution climate model to determine when and how VFFs formed, and why they form in these specific locations, as opposed to elsewhere in the crater.

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