Distribution of Subsurface Carbon Dioxide Ice at Different Obliquities

Patel, Narissa; Lewis, Stephen; Hagermann, Axel and Balme, Matthew (2020). Distribution of Subsurface Carbon Dioxide Ice at Different Obliquities. In: RAS Planetary Atmospheres Meeting, 14 Feb 2020, Royal Astronomical Society, London.

Abstract

We present initial results from the UK version of the LMD Mars Global Circulation Model using a newly developed subsurface model showing the distribution of subsurface carbon dioxide (CO₂) at four different obliquities (15°, 25°, 35° and 45°). These results use an initial condition of subsurface CO₂ ice at latitudes >50° N/S and are an initial study that will inform future investigations because the amount and distribution of subsurface CO₂ ice in the present day is unknown. Studies of subsurface ice on Mars focused mostly on the distribution of water ice, because subsurface CO₂ ice is unstable outside of the polar regions. However, subsurface CO₂ ice is more likely to be stable at the higher pressures expected for Early Mars [e.g. 1].

Studies [e.g. 2, 3] have also shown that water ice becomes more widespread across the surface at high obliquities due to sublimation of the polar caps and the equatorward transport of water [e.g. 3, 4]. However, since it has been assumed that CO₂ ice can only occur within the polar regions, any changes in subsurface CO₂ ice distribution with obliquity are unknown. We have included CO₂ ice physics in the subsurface to account for potential subsurface CO₂ ice outside of the polar regions.

[1] Kahn R. (1985) Icarus, 62, 175-190
[2] Mellon M.T., Jakosky B.M. (1995) JGR:Planets, 100, 6, 2156-2202
[3] Head J.W. et al. (2003) Nature, 426, 6968, 797-802
[4] Pollack J.B., Toon O.B. (1982), Icarus, 50, 2, 259-287

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