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W.M. Grundy, M.W. Buie, J.R. Spencer (Lowell Observatory), L.A. Young, E.F. Young (Southwest Research Institute)
The non-uniform distribution of Pluto's surface ices, along with the planet's high obliquity, 6 day rotation period, and 250 year orbital period combine to produce variations in Pluto's reflectance spectrum over a broad range of times scales. Volatile transport can also influence the spectrum over time, as ices sublimate and re-condense elsewhere on Pluto's surface. In an effort to detect and to distinguish between the various factors influencing Pluto's spectral reflectance over time, we have been monitoring the system spectroscopically over the past 2 decades. The SpeX instrument, commissioned in 2000 at NASA's IRTF, is an ideal tool for this purpose. Using it, we have obtained good quality spectra of the Pluto\slash Charon system on 15 nights since 2000, covering the 0.8 to 2.4~\mum wavelength range at spectral resolutions ~1000\null. This spectral region features numerous, prominent CH4 ice absorption bands, as well as a few isolated bands of N2 and CO ices. We will present the new IRTF\slash SpeX observations, comparing the longitudinal distributions of these species with results from earlier observations. We will also report on subtle, longer-term seasonal and\slash or latitudinal trends. A similar quality data set has been obtained for Neptune's satellite Triton, and will be presented separately.
This work has been supported by NASA grants NAG5-4210 and NAG5-10159 to Lowell Observatory, by NASA grant NAG5-12516 and NSF grant AST-0085614 to Southwest Research Institute, by NSF REU Program grant #9423921 to Northern Arizona University, and by Hubble Fellowship grant #HF-01091.01-97A.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.