HR: 10:35h
AN: P42A-02 [Abstracts]
TI: Titan: NatureÝs Laboratory for Organic Synthesis
AU: * Yung, Y L
EM: yly@gps.caltech.edu
AF: Caltech, 1200 E. California Blvd., Caltech 150-21, Pasadena, CA 91125
United States
AB:
It has been nearly a third of a century since StrobelÝs (1973) pioneering study of hydrocarbon chemistry and AxelÝs (1972)
seminal work on the hydrocarbon aerosols. Methane, the parent molecule of hydrocarbons, is abundant on Titan. Photolysis of
methane results in the synthesis of more complex hydrocarbons. The hydrocarbon chemistry is unique and rich and the same
reactions apply to all reducing atmospheres. The hydrocarbon chemistry inevitably leads to the formation of high molecular
weight products, giving rise to aerosols when the ambient atmosphere is cool enough for them to condense. We will review the
progress in the hydrocarbon chemistry since the Voyager encounters (Yung et al., 1984). A number of pathways to organic
synthesis from simple to complex hydrocarbons have been identified. Neutral schemes involve radicals such as C$_3$H$_3$ and
C$_3$H$_5$. Ion schemes involve charged radicals such as c-C$_3$H$_2^+$ and C$_4$H$_3^+$. Both ringed and chained compounds
can be synthesized. The organic chemistry is a very sensitive function of the H and H$_2$ concentrations in the atmosphere.
In fact, we can ``retrieve" the concentration of H atoms in the atmosphere from the recent ground-based observation of the
allene to methylacetylene ratio. Preliminary results from Cassini will also be discussed.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting