Methane absorption variations in the spectrum of Pluto

Marc W. Buie, Uwe Fink

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Absolute spectrophotometry of Pluto in the wavelength range of 5600 to 10,500 Å was obtained on 4 nights covering lightcurve phases of 0.18, 0.35, 0.49, and 0.98. The four phases included minimum light (0.98) and one near maximum light (0.49). The spectra reveal significant variations in the absorption depths of the methane bands at 6200, 7200, 7900, 8400, 8600, 8900, and 10,000 Å. The minimum amount of absorption was found to occur at minimum light. This variation would imply a 30° change in the column abundance of methane within 3 days. A model employing an anisotropic surface distribution of methane frost and a clear layer of CH4 gas was developed to explain the variation in absorption strength with rotational phase. The fit to the overall spectrum requires the presence of a frost with particle sizes on the order of a few millimeters. An upper limit of 5.5 m-am is derived for the one-way column abundance of CH4 gas. An equally good fit to the variation of the 7200-Å band is obtained if the atmosphere is removed from the model entirely.

Original languageEnglish (US)
Pages (from-to)483-498
Number of pages16
Issue number3
StatePublished - Jun 1987

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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