Absorption Coefficients of the Methane-Nitrogen Binary Ice System: Implications for Pluto

Abstract

The methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983) indicates that at temperatures relevant to the surfaces of icy dwarf planets like Pluto, two phases contribute to the methane absorptions: nitrogen saturated with methane $\overline{{\mathbf{N}}_2}$:CH${}_4$ and methane saturated with nitrogen $\overline{\mathbf{C}{\mathbf{H}}_4}$:N${}_2$. No optical constants are available so far for the latter component limiting construction of a proper model, in compliance with thermodynamic equilibrium considerations. New optical constants for solid solutions of methane diluted in nitrogen (N${}_2$:CH${}_4$) and nitrogen diluted in methane (CH${}_4$:N${}_2$) are presented at temperatures between 40 and 90 K, in the wavelength range 1.1-2.7 $\mu$m at different mixing ratios. These optical constants are derived from transmission measurements of crystals grown from the liquid phase in closed cells. A systematic study of the changes of methane and nitrogen solid mixtures spectral behavior with mixing ratio and temperature is presented.

References in corpus (1)

• New Horizons: Anticipated Scientific Investigations at the Pluto System

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• The Dwarf Planet Makemake as seen by X-Shooter