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Spectroscopy of Pluto, 380-930 Nm at Six LongitudesWe have obtained spectra of the Pluto-Charon pair (unresolved) in the wavelength range 380-930 nm with resolution approx..450 at six roughly equally spaced longitudes. The data were taken in May and June, 2014, with the 4.2-m Isaac Newton Telescope at Roque de Los Muchachos Observatory in the Canary Islands, using the ACAM (auxiliary-port camera) in spectrometer mode, and using two solar analog stars. The new spectra clearly show absorption bands of solid CH4 at 620, 728, and 850-910 nm, which were known from earlier work. The 620-nm CH4 band is intrinsically very weak, and its appearance indicates a long optical path-length through the ice. This is especially true if it arises from CH4 dissolved in N2 ice. Earlier work (Owen et al. Science 261, 745, 1993) on the near-infrared spectrum of Pluto (1-2.5 microns) has shown that the CH4 bands are shifted to shorter wavelengths because the CH4 occurs as a solute in beta-phase crystalline N2. The optical path-length through the N2 crystals must be on the order of several cm to produce the N2 band observed at 2.15 microns. The new spectra exhibit a pronounced red slope across the entire wavelength range; the slope is variable with longitude, and differs in a small but significant way from that measured at comparable longitudes by Grundy & Fink (Icarus 124, 329, 1996) in their 15-year study of Pluto's spectrum (500-1000 nm). The new spectra will provide an independent means for calibrating the color filter bands on the Multispectral Visible Imaging Camera (MVIC) (Reuter et al. Space Sci. Rev. 140, 129, 2008) on the New Horizons spacecraft, which will encounter the Pluto-Charon system in mid-2015. They will also form the basis of modeling the spectrum of Pluto at different longitudes to help establish the nature of the non-ice component(s) of Pluto's surface. It is presumed that the non-ice component is the source of the yellow-red coloration of Pluto, which is known to be variable across the surface.
Document ID
20150020447
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Cruikshank, D. P. (NASA Ames Research Center Moffett Field, CA United States)
Pinilla-Alonso, N. (Tennessee Univ. Knoxville, TN, United States)
Lorenzi, V. (Consejo Superior de Investigaciones Cientificas Barcelona, Spain)
Grundy, William (Lowell Observatory Flagstaff, AZ, United States)
Licandro, J. (Consejo Superior de Investigaciones Cientificas Barcelona, Spain)
Binzel, R. P. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Date Acquired
November 3, 2015
Publication Date
August 18, 2014
Subject Category
Astrophysics
Report/Patent Number
ARC-E-DAA-TN18024
Meeting Information
Meeting: Annual Meeting, Division for Planetary Science,American Astronomical Society
Location: Tucson, AZ
Country: United States
Start Date: November 9, 2014
End Date: November 14, 2014
Sponsors: American Astronomical Society
Funding Number(s)
WBS: WBS 750760.06.03.02
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
Spectroscopy
Ices
Pluto

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