The Mesoscale Meteorology of Lyot Crater on Mars

Foley, Lori-Ann (2024). The Mesoscale Meteorology of Lyot Crater on Mars. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.00098852

Abstract

This PhD investigates the relationship between the changing climate, the water cycle and the deposition and ablation of surface water ice on Mars. It focusses on Lyot crater, a location with ice-rich landforms and fluvial features formed during the Amazonian epoch (from present day to 2.9 billion years ago). I show that Lyot has its own microenvironment even under present-day conditions. I modelled Lyot's climate with changing orbital parameters to determine during which periods ice was deposited or ablated and where in Lyot this happened. I found that the ice source moved from the poles to the tropics at obliquities below 45◦, a value lower than that suggested by other researchers. Frost deposition was common, with snowfall also occurring during some periods in the winter, leading to the formation of the ice-rich mantle covering much of Lyot. Several ice-rich features evolved from this mantle. Pits in the ice formed throughout much of Lyot's history, predominantly by sublimation but also by melt and evaporation when conditions were suitable. Thick ice on steep slopes is shown to flow downslope when conditions were suitable for ice to thaw. Polygons in the ice formed by thermal contraction, enhanced by ice melt and refreezing, with fractures expanding during periods when conditions were suitable. I show that Lyot's microenvironment, under some orbital conditions, would permit ice to melt and water to flow during summertime, which is consistent with the presence of fluvial features such as channels, paleolakes and fan deposits. At times when conditions were not suitable, the water would freeze and in areas where water was sufficiently deep and slow flowing the freezing ice could form a cover, protecting the liquid water underneath. Hence, the research in this thesis has expanded knowledge of the water cycle on Mars during the recent Amazonian epoch.

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