Titan's complex ion chemistry

Titan, Saturn's largest moon, has a substantial ionosphere on the night side, and complex ion chemistry is operating there, according to the first analysis of mass spectral data gathered last year during the Cassini spacecraft's flight through the moon's ionosphere (Geophys. Res. Lett. 2006, 33, L07105). Titan's dense atmosphere is composed of molecular nitrogen and methane with minor amounts of many hydrocarbon and nitrile species. Past studies have shown that solar radiation and energetic electrons from Saturn's magnetosphere ionize neutral molecules in Titan's atmosphere, creating an ionosphere above 800 km. That ionosphere has now been found to persist into the night, according to Thomas E. Cravens of the University of Kansas. He and his colleagues confirmed the presence of several ions that were previously predicted by ionospheric models, such as HCNH⁺ (the most abundant ion), C₂H₅⁺, CH₅⁺, and C₃H₅⁺. The data also revealed unexpectedly high densities of other ions, such as one of mass 18, which the researchers suggest is NH₄⁺, even though its neutral precursor, NH₃, hasn't yet been detected in Titan's atmosphere.