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G. L. Bjoraker, C. Nixon, R. Achterberg, F. M. Flasar (NASA/GSFC), B. Bézard, E. Lellouch (Obs. de Paris-Meudon)
During the Cassini flyby in 2000-2001, the CIRS instrument acquired infrared spectra of Jupiter with an unprecedented combination of spatial and spectral resolution. Stratospheric emission of HCN at 712 cm-1 (14.0 microns) and CO2 at 667 cm-1 (15.0 microns) was measured using large numbers of spectra averaged together in 10-degree wide latitude bins. Care was taken in the polar regions to select spectra both inside and outside of auroral hot spots. Knowledge of both stratospheric and tropospheric temperatures is required to derive absolute abundances of HCN and CO2. Stratospheric temperatures were obtained from observations of the nu4 band of CH4 at 1306 cm-1 (7.66 microns). Tropospheric temperatures were retrieved from H2-H2 opacity between 600 and 700 cm-1 (14-17 microns). HCN emission peaks near 45 degrees South, consistent with it being a product of the collision of Comet Shoemaker-Levy 9 with Jupiter in 1994. CO2, on the other hand, peaks near the South Pole. The short lifetime of CO2 suggests that it is also a remnant of SL9, but that additional dynamical and photochemical processes are at work. Neither HCN nor CO2 is enhanced at the longitudes of the auroral hot spots. This constrains the emission to lie deeper than 10 microbars in Jupiter's stratosphere. Preliminary results yield abundances of 35 ppb HCN and 5 ppb CO2 at 45 degrees South on Jupiter.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.