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B. N. Hilbert (Boston Univ.), J. A. Stansberry, W. M. Grundy (Lowell Obs.), R. V. Yelle (Boston Univ.), M. W. Buie (Lowell Obs.), C. Dalla Piazza (Lycoming Col.)
We have obtained near-IR spectra of Triton from 1995 through 1998. The spectra were recorded with the OSIRIS spectrometer and cover the 1.2-2.3~\mum wavelength region with a nominal resolving power of 300\null. The spectra clearly show absorption features due to CH4 and N2\null. Changes in the surface temperature of Triton are expected based on the change of solar insolation with season. This expectation is supported by observed changes in the atmospheric bulk on Triton, reported by Elliot {\it et al.}\ ({\it Nature} {\bf 393,} 765--767, 1998). These authors report a doubling of atmospheric bulk in the last 8 years which is consistent with a temperature rise in the N2 ice of 2~K\null. We analyze the N2 band at 2.15~\mum, to determine if the band has changed in depth or width. Changes in band depth could be caused by volatile transport or by changes in surface texture resulting from the current maximum southern summer. Changes in band width are expected to result from the increasing temperature of Triton's surface. We also examine the CH4 bands for evidence of changes in depth and wavelength, as would result from changes in the concentration of CH4 dissolved in the N2 ice.
The author(s) of this abstract have provided an email address for comments about the abstract: hilbert@lowell.edu