36th DPS Meeting, 8-12 November 2004
Session 30 Jupiter and Saturn: Composition, Structure, Dynamics
Oral, Thursday, November 11, 2004, 1:45-4:15pm, Clark

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[30.01] The HCN and CO2 distribution on Jupiter

E. Lellouch, D.F Strobel, B. Bézard (Obs. Paris), G.L. Bjoraker, F.M. Flasar, P.N. Romani (NASA/GSFC)

Cassini/CIRS observations acquired in December 2000 have revealed very different latitudinal distributions for HCN and CO2 on Jupiter (Kunde et al. 2004). HCN exhibits a maximum abundance at 45 S, a steady decrease towards the North up to 50 N and a sharp decrease poleward of 50 N and 45 S. In contrast, CO2 has a fairly constant abundance from 30 S to 80 N, and a maximum southward of 60 S.

The source of HCN and CO2 is thought to be the Shoemaker-Levy 9 collision in 1994, since observations immediately following the impacts have detected the abundant presence of HCN, CO, and H2O; CO2 can photolytically build from CO and H2O. Different latitudinal profiles for these two species are therefore puzzling. Qualitatively, the maintenance of an HCN maximum at the impact latitude 6.5 years after the impacts may result from a dynamical isolation of the high southern latitudes, or from a destruction of HCN in auroral regions. The CO2 maximum at high latitudes may be due to auroral precipitation of oxygen bearing material and its subsequent conversion to CO2. An alternate explanation is that the different HCN and CO2 distribution may reflect different horizontal transport of two species with possibly initially different vertical distributions.

We examine here some of these ideas. In particular, we use a simplified chemical-transport model to study whether the HCN distribution can result from purely diffusive transport, and to evaluate the auroral oxygen fluxes needed to produce the CO2 maximum at Southern latitudes.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.