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L. M. Trafton, J. H. Lacy (U. Texas), H. Roe (Caltech), M. Richter (UC Dvis)
The Voyager 1 IRIS experiment, during its early northern spring 1980 flyby, first detected cyanoacetylene (HC3N) in Titan's atmosphere. It was not distributed uniformly over Titan's disk, but was found to be concentrated primarily in the northern polar regions, above 70deg latitude. It was not detected below latitude +55deg. At that time, Titan's subsolar latitude was +5deg. The first ground-based detection of Titan's cyanoacetylene was reported by Bezard et al. (1992) from sub-mm observations obtained during Titan northern summer. Martin et al. (2002) reported sub-mm observations of this band obtained between 1996-1999 during southern spring; and Garwell (2004) reported sub-mm observations taken that year during southern summer. We report the first ground-based observations of Titan's cyanoacetylene obtained in the mid-IR. The observations were taken of the \nu6 band at 20 \mum with TEXES, the Texas Echelon Cross Echelle Spectrograph, on the IRTF telescope on Jan 15, 2005, the day after the Huygens Probe decent. The instrument was operated in medium-resolution (R=15,000) longslit mode, scanning the slit past the object in a series of exposures to capture all of the flux and to provide adequate sky for background subtraction. The band head and a spectral region next to it, which is clear of emission lines, was clearly resolved; but the individual lines of this Q branch were not resolved. Titan's season corresponded to early southern summer, with subsolar latitude -27deg. None of the ground-based observations resolve Titan's disk. We will compare the column abundance of cyanoacetylene with previous measurements at different subsolar and subearth latitudes and comment on the differences.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.