Saturn's Hydrocarbon Emission from Ground-based and Cassini/CIRS Observations

Hydrocarbons in the upper atmosphere of Saturn are known, from Voyager and early Cassini results, to vary in emission intensity with latitude. Of particular interest is the marked increase in temperature and hydrocarbon line intensity near the South Pole (Greathouse et al. 2005, Orton and Yanamandra-Fisher, 2005, Flasar et al. 2005). Latitudinal variations in hydrocarbon abundances can be determined from measurements of hydrocarbon emission lines using temperatures derived from Cassini's Composite InfraRed Spectrometer (CIRS). Latitudinal, temporal, and vertical variations of stratospheric hydrocarbons provide constraints on dynamics, seasonal climate models, and photochemical models. In an effort to monitor temporal and latitudinal variations of hydrocarbons in Saturn's southern hemisphere we are conducting a ground-based campaign using Celeste, an infrared (5-25 μm) high-resolution (