ICE MINERALOGY ACROSS AND INTO THE SURFACES OF PLUTO, TRITON, AND ERIS

Journal Article · Sun May 20 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/751/1/76· OSTI ID:22037221

Tegler, S C ^[1]; Grundy, W M ^[2]; Olkin, C B; Young, L A ^[3]; Romanishin, W ^[4]; Cornelison, D M ^[5]; Khodadadkouchaki, R ^[6]

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1. Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ 86011 (United States)
2. Lowell Observatory, Flagstaff, AZ 86001 (United States)
3. Southwest Research Institute, Boulder, CO 80302 (United States)
4. Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States)
5. Department of Physics, Astronomy, and Materials Science, Missouri State University, Springfield, MO 65897 (United States)
6. Department of Physics, California State University, Northridge, CA 91330 (United States)

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 Degree-Sign , 125 Degree-Sign , and 257 Degree-Sign . 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 Degree-Sign and 314 Degree-Sign . 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.

• OSTI ID: 22037221
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 751; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
ASTRONOMY
ASTROPHYSICS
EMISSION
GAIN
ICE
INFRARED SPECTRA
METHANE
MINERALOGY
MIXING RATIO
NEAR INFRARED RADIATION
NITROGEN
PLUTO PLANET
RADIATION HEATING
SATELLITES
SUBLIMATION
SURFACES
TELESCOPES
VISIBLE RADIATION