The first detection of propane on Saturn

We report the first detection of propane, C3H8, in Saturnʹs stratosphere. Observations taken on September 8, 2002 UT at NASAʹs IRTF using TEXES, show multiple emission lines due to the 748 cm−1 ν 21 band of C3H8. Using a line-by-line radiative transfer code, we are able to fit the data by scaling the propane vertical mixing ratio profile from the photochemical model of Moses et al. [2000. Icarus 143, 244–298]. Multiplicative factors of 0.7 and 0.65 are required to fit the −20° and −80° planetocentric latitude spectra. The resultant profiles are characterized by a 5 mbar mixing ratio of 2.7 ± 0.8 × 10 −8 at −20° and 2.5 −0.8 +1.7 × 10 −8 at −80° latitude. These results suggest that the time scale for meridional circulation lies between the net photochemical lifetimes of C2H2 and C3H8, ≈ 30 – 600 years.