This study of the atmosphere of Jupiter and Titan consists in large part of three papers, each of which employs the Caltech/ JPL one-dimensional photochemical model.
Paper One: Aromatic compounds have been considered a likely candidate for enhanced aerosol formation in the polar region of Jupiter. In this paper, a newchemical model for aromatic compounds in the auroral thermosphere/ionosphere is developed, which satisfies constraints from the observations of each of Voyager, Galileo and the Infrared Space Observatory. The study demonstrates that sufficient quantities of higher ring species can condense to form aerosol.
Paper Two: A comprehensive atmospheric model is put forward and used to investigate the details of benzene chemistry on Jupiter, in both its auroral and non-auroralregions. The benzene formation schemes are discussed for neutral chemistry and ion chemistry, and the major uncertainties in the chemical kinetics are identified.The model shows that ion chemistry adds an additional source of benzene in auroral regions. The results are compared with observations made by the Infrared SpaceObservatory. 172
Paper Three: The recent observation of the heavy isotopomers of CO, ^(13)CO and C^(18)O, may be used to place constraints on the evolution of the atmosphere of Titan. 200 However, the original isotopic signature may be altered by photochemical reactions. This paper explains the absence of C isotopic enrichment in Titan's atmosphere,despite the significant enrichment of heavy H, N, and O isotopes. It is shown that there is a rapid exchange for C atoms between the CH_4 and CO reservoirs, mediatedby the reaction ^1CH_2+*CO →^1*CH_2 + CO, where *C is ^(13)C. 261 Next, the isotopic dilution of CO is investigated using a photochemical model, the results ofwhich suggest that the time constant for isotopic exchange through the aforementioned reaction is approximately 800 Myr. This duration is considerably shorter than the age of Titan, and thus any original isotopic enhancement of ^(13)C in CO may have been diluted by this exchange process. This paper concludes by proposing a plausible model for the evolution history of CO on Titan's atmosphere.
