37th DPS Meeting, 4-9 September 2005
Session 56 TNOs and Centaurs
Poster, Thursday, September 8, 2005, 6:00-7:15pm, Music Recital Room

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[56.06] Spectrum Models of High-Albedo Kuiper Belt Objects and Centaurs

C. M. Dalle Ore (SETI/NASA Ames), D. P. Cruikshank (NASA Ames)

In a recent paper (Cruikshank and Dalle Ore 2003, Earth, Moon & Planets 92, 315) we showed that the visible and near-infrared reflectance spectra (out to 2.5 micrometers) of all of the color classes of low-albedo (approx. 0.04) Kuiper Belt Objects (KBOs) and Centaurs can be modeled with various combinations of minerals and organic complexes (tholins), both with and without water ice. New determinations of the albedos of these objects emerging from the thermal observations at 24 and 70 micrometers with the Spitzer Space Telescope show that a significant number of KBOs and Centaurs have substantially higher albedos, reaching 0.20 or greater (e.g., Cruikshank et al. 2005, Astrophys. J. Lett. 624, L53). Accordingly, we present here an extension of our original modeling study, as well as a comparison with previous results. Seven individual objects were chosen to represent different levels of redness in the UV/visible/near-IR slope and with albedos (at 0.55 micrometers) in the range 0.06 to 0.18. Models were calculated using the same basic library of optical constants used in our 2003 work to explore trends in composition and grain sizes for three different color groups. The new models confirm the need for organic materials to achieve good fits for the red color in the reddest classes of objects. The models can accommodate water ice in cases where the ice bands have been detected spectroscopically.

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