Methane and nitrogen abundances on Pluto and Eris

Tegler, S. C. and Cornelison, D. M. and Grundy, W. M. and Romanishin, W. and Abernathy, M. R. and Bovyn, M. J. and Burt, J. A. and Evans, D. E. and Maleszewski, C. K. and Thompson, Z. and Vilas, F. (2010) Methane and nitrogen abundances on Pluto and Eris. Astrophysical Journal, 725 (1). pp. 1296-1305. ISSN 1538-4357

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Abstract

We present spectra of Eris from the MMT 6.5 m Telescope and Red Channel Spectrograph (5700-9800 Å, 5 Å pixel–1) on Mt. Hopkins, AZ, and of Pluto from the Steward Observatory 2.3 m Telescope and Boller and Chivens Spectrograph (7100-9400 Å, 2 Å pixel–1) on Kitt Peak, AZ. In addition, we present laboratory transmission spectra of methane-nitrogen and methane-argon ice mixtures. By anchoring our analysis in methane and nitrogen solubilities in one another as expressed in the phase diagram of Prokhvatilov & Yantsevich, and comparing methane bands in our Eris and Pluto spectra and methane bands in our laboratory spectra of methane and nitrogen ice mixtures, we find Eris' bulk methane and nitrogen abundances are ~10% and ~90% and Pluto's bulk methane and nitrogen abundances are ~3% and ~97%. Such abundances for Pluto are consistent with values reported in the literature. It appears that the bulk volatile composition of Eris is similar to the bulk volatile composition of Pluto. Both objects appear to be dominated by nitrogen ice. Our analysis also suggests, unlike previous work reported in the literature, that the methane and nitrogen stoichiometry is constant with depth into the surface of Eris. Finally, we point out that our Eris spectrum is also consistent with a laboratory ice mixture consisting of 40% methane and 60% argon. Although we cannot rule out an argon-rich surface, it seems more likely that nitrogen is the dominant species on Eris because the nitrogen ice 2.15 μm band is seen in spectra of Pluto and Triton.

Item Type:	Article
Publisher’s Statement:	© 2010 The American Astronomical Society. Published by IOP Publishing.
ID number or DOI:	10.1088/0004-637X/725/1/1296
Keywords:	04; 2003 ub313; aliphatic hydrocarbons; Alkanes; argon; Astrophysics - Earth and Planetary Astrophysics; ch4; chemical composition; dwarf planets; Eris; experimental studies; Extraterrestrial geology; hydrocarbons; Ice; kuiper-belt; laboratory studies; methane; methods: laboratory; methods: observational; mu-m; n-2; nitrogen; noble gases; optical spectra; Organic compounds; planets and satellites: surfaces; Pluto; Solubility; spectra; Spectroscopy; spectrum; Stoichiometry; Surface; techniques: spectroscopic; triton; volatiles
Subjects:	Q Science > QB Astronomy
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited:	30 Sep 2015 17:56
URI:	http://openknowledge.nau.edu/id/eprint/433

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