HR: 10:20h
AN: P42A-01    [Abstracts]
TI: Origin and Evolution of Titan's Atmosphere: Testing the Models
AU: * Owen, T C
EM: owen@ifa.hawaii.edu
AF: University of Hawaii, Institute for Astronomy 2680 Woodlawn Drive, Honolulu, HI 96822 United States
AB: With early results from Cassini and the imminent deployment of Huygens, it is useful to consider what observations the orbiter and the probe will be able to make to test existing models for the origin and evoution of Titan's atmosphere. This atmosphere must have resulted from some mixture of cometary impacts plus outgassing of the materials making up the bulk of the satellite. The nature of the icy planetestimals that accreted to form Titan is thus a key unknown in attempts to deduce atmospheric origin. Ground-based observations of $^{15}$N/$^{14}$N in HCN and $^{18}$O/$^{16}$O in CO suggest massive escape of the early atmosphere. The rapid photolysis of atmospheric CH$_{4 }$ and the near-normality of $^{13 }$C/$^{12 }$C both require a continuing source for methane, and some form of renewal is also necessary to maintain the abundance of CO. Subterranean oceans, cryovolcanism, continuing Fischer-Tropsch-type reactions and the metabolism of hypothetical sub-surface organisms are all alluring solutions to these problems. Predictions for isotope ratios and abundances flowing from the different models can be tested by the array of instruments carried by the Cassini-Huygens orbiter and probe.
DE: 5405 Atmospheres--composition and chemistry
DE: 5407 Atmospheres--evolution
DE: 5455 Origin and evolution
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting