Vertical Distribution of Cyclopropenylidene and Propadiene in the Atmosphere of Titan

Titan's atmosphere is a natural laboratory for exploring the photochemical synthesis of organic molecules. Significant recent advances in the study of the atmosphere of Titan include: (a) detection of C₃ molecules: C₃H₆, CH₂CCH₂, c-C₃H₂, and (b) retrieval of C₆H₆, which is formed primarily via C₃ chemistry, from Cassini Ultraviolet Imaging Spectrograph data. The detection of c-C₃H₂ is of particular significance as ring molecules are of great astrobiological importance. Using the Caltech/JPL KINETICS code, along with the best available photochemical rate coefficients and parameterized vertical transport, we are able to account for the recent observations. It is significant that ion chemistry, reminiscent of that in the interstellar medium, plays a major role in the production of c-C₃H₂ above 1000 km.