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

Tegler, S. C. and Grundy, W. M. and Olkin, C. B. and Young, L. A. and Romanishin, W. and Cornelison, D. M. and Khodadadkouchaki, R. (2012) Ice mineralogy across and into the surfaces of Pluto, Triton, and Eris. Astrophysical Journal, 751 (1). p. 76. ISSN 1538-4357


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Publisher’s or external URL: http://dx.doi.org/10.1088/0004-637x/751/1/76


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.

Item Type: Article
Publisher’s Statement: © 2012 The American Astronomical Society. Published by IOP Publishing.
ID number or DOI: 10.1088/0004-637X/751/1/76
Keywords: 04; 2003 ub313; aliphatic hydrocarbons; Alkanes; Astrophysics -- Research; ch4; composition; Depth; dwarf planets; Eris; Evolution; Extraterrestrial geology; Hapke model; hydrocarbons; Ice; icy satellites; laboratory studies; methane; methane ice; methods; methods: laboratory; methods: observational; Mixing; n-2; NEAR infrared radiation; near-infrared spectra; nitrogen; observations; optical spectra; Organic compounds; Planetary research; planets and satellites: surfaces; Pluto; Pluto (Dwarf planet); research; satellites; spectra; Spectroscopy; statistical analysis; sublimation; techniques: spectroscopic; telescope methods; thermal emission; The Sun and the Solar System; Triton Satellite
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 17:59
URI: http://openknowledge.nau.edu/id/eprint/434

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