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H.G. Roe (Caltech), T.K. Greathouse (U.T. Austin), M.J. Richter (U.C. Davis), J.H. Lacy (U.T. Austin)
We report the first Earth-based detection of propane (C3H8) in Titan's atmosphere. Previous attempts at measuring Titan's propane abundance using Voyager and Infrared Space Observatory (ISO) spectra were hampered by low spectral resolution, which left the contribution from propane emission entangled with strong emission from more abundant species. Using the high-resolution spectrograph TEXES (\lambda/\Delta\lambda=100,000) on NASA's Infrared Telescope Facility we unambiguously detected numerous propane lines near the center of the 748~cm-1 \nu26 band. The lines are overlaid on strong acetylene (C2H2) and HCN lines and require high spectral resolution in order to separate the contribution of propane from that of these other species. We fit our data with the available laboratory measurements and theoretical calculations of the \nu26 band to give a new measurement of the abundance of propane in Titan's atmosphere. Further, we inter-compare the available laboratory measurements and theoretical calculations and suggest that more low-temperature/low-pressure measurements of propane's 748~cm-1 \nu26 band are warranted.
TKG was supported by the SOFIA project through USRA grant 8500-98-008. Observations with TEXES are supported by NSF grant AST-0205518. This material is based upon work supported by the National Aeronautics and Space Administration under Cooperative Agreement no. NCC 5-538 issued through the Office of Space Science, Planetary Astronomy Program.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.