Ice mineralogy across and into the surfaces of Pluto, Triton, and Eris

S. C. Tegler, W. M. Grundy, C. B. Olkin, L. A. Young, W. Romanishin, D. M. Cornelison, R. Khodadadkouchaki

Research output: Contribution to journalArticle

21 Scopus citations

Abstract

We present three near-infrared spectra of Pluto taken with the Infrared Telescope Facility and SpeX, an optical spectrum of Triton taken with the MMT and the Red Channel Spectrograph, and previously published spectra of Pluto, Triton, and Eris. We combine these observations with a two-phase Hapke model and gain insight into the ice mineralogy on Pluto, Triton, and Eris. Specifically, we measure the methane-nitrogen mixing ratio across and into the surfaces of these icy dwarf planets. In addition, we present a laboratory experiment that demonstrates it is essential to model methane bands in spectra of icy dwarf planets with two methane phases - one highly diluted by nitrogen and the other rich in methane. For Pluto, we find bulk, hemisphere-averaged, methane abundances of 9.1% ± 0.5%, 7.1% ± 0.4%, and 8.2% ± 0.3% for sub-Earth longitudes of 10°, 125°, and 257°. Application of the Wilcoxon rank sum test to our measurements finds these small differences are statistically significant. For Triton, we find bulk, hemisphere-averaged, methane abundances of 5.0% ± 0.1% and 5.3% ± 0.4% for sub-Earth longitudes of 138° and 314°. Application of the Wilcoxon rank sum test to our measurements finds the differences are not statistically significant. For Eris, we find a bulk, hemisphere-averaged, methane abundance of 10% ± 2%. Pluto, Triton, and Eris do not exhibit a trend in methane-nitrogen mixing ratio with depth into their surfaces over the few centimeter range probed by these observations. This result is contrary to the expectation that since visible light penetrates deeper into a nitrogen-rich surface than the depths from which thermal emission emerges, net radiative heating at depth would drive preferential sublimation of nitrogen leading to an increase in the methane abundance with depth.

Original languageEnglish (US)
Article number76
JournalAstrophysical Journal
Volume751
Issue number1
DOIs
StatePublished - May 20 2012

Keywords

  • methods: laboratory
  • methods: observational
  • planets and satellites: surfaces
  • techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Tegler, S. C., Grundy, W. M., Olkin, C. B., Young, L. A., Romanishin, W., Cornelison, D. M., & Khodadadkouchaki, R. (2012). Ice mineralogy across and into the surfaces of Pluto, Triton, and Eris. Astrophysical Journal, 751(1), [76]. https://doi.org/10.1088/0004-637X/751/1/76