Characterization of nitrogen ice on Pluto's surface from 1-4 micron spectroscopy

Abstract : Nitrogen ice is the predominant ice on Pluto's surface. Methane and CO have also been identified (e.g., Grundy & Buie 2001), but they are thought to be trace consituents relative to N2, mainly because of the strength of nitrogen's 2.147 μm feature. It is assumed that the temperature of the surface N2 frost controls the column abundance of Pluto's atmosphere through vapor pressure equilibrium. The vapor pressures of CO and CH4 are about 5 and 10,000 times less than that of N2 at a typical temperature for Pluto's surface. There is spectroscopic evidence that CH4 ice exists as a dissolved constituent in a predominantly nitrogen ice matrix as well as separate, pure CH4 ice. It would be interesting to know what fraction of N2 ice is pure for purposes of modeling the surface/ atmosphere interactions on Pluto. We present spectroscopic modeling to show that the fraction of pure N2 ice on Pluto is very small indeed – conservatively less than 6% by area. We will present spectral observations and modeling results from the IRTF1, W.M. Keck2 and Subaru3 Observatories spanning 1.0 to 4.0 μm. We have implemented a Hapke model (Hapke 1993) to constrain the abundance and states of N2 ice and CH4 ice. The depth of the Pluto spectrum at 3.3 μm effectively limits the amount of pure N2 ice that can be present on Pluto.
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Conference papers
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Submitted on : Thursday, February 26, 2009 - 6:12:57 PM
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E. F. Young, C. B. Olkin, L. A. Young, W. Grundy, Bernard Schmitt, et al.. Characterization of nitrogen ice on Pluto's surface from 1-4 micron spectroscopy. European Planetary Science Congress 2006, Sep 2006, Berlin, Germany. ⟨insu-00364695⟩

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