Absorption coefficients of the methane-nitrogen binary ice system: Implications for Pluto

S. Protopapa, W. M. Grundy, S. C. Tegler, J. M. Bergonio

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


The methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983. Sov. J. Low Temp. Phys. 9, 94-98) 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 N2:CH4 and methane saturated with nitrogen CH4:N2. 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 (N2:CH4) and nitrogen diluted in methane (CH4:N2) are presented at temperatures between 40 and 90K, in the wavelength range 1.1-2.7μm 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.

Original languageEnglish (US)
Pages (from-to)179-188
Number of pages10
StatePublished - Jun 1 2015


  • Ices, IR spectroscopy
  • Pluto
  • Trans-neptunian objects

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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