Improved Determination of Ethane (C2H6) Abundance in Titanʹs Stratosphere

Ethane spectral lines were observed in emission from Titan in August 1993, October 1995, and September 1996, at a spectral resolution of λ/Δλ≈106, at wavelength 11.7−11.9 μm using the Goddard Infrared Heterodyne Spectrometer at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. The ethane mole fraction is determined to be (8.8±2.2)×10−6 (68.3% confidence limits, “1σ”), averaging the retrievals from each observing run obtained using the “recommended” thermal profile of R. V. Yelle, D. Strobel, E. Lellouch, and D. Gautier (1997, in Huygens: Science, Payload, and Mission (J.-P. Lebreton, Ed.), pp. 243–256, European Space Agency SP-1177).