DPS 35th Meeting, 1-6 September 2003
Session 40. Outer Planets/Gas Giants IV
Poster, Highlighted on, Friday, September 5, 2003, 3:30-6:00pm, Sierra Ballroom I-II

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[40.16] Cassini CIRS Observations of Ammonia in Jupiter's Upper Troposphere

R. K. Achterberg (SSAI), B. J. Conrath, P. J. Gierasch (Cornell U.), F. M. Flasar (NASA/GSFC)

Between Dec 31 2000 and Jan 11 2001, the Cassini spacecraft performed four global mapping sequences of Jupiter. During these maps, the Composite Infrared Spectrometer (CIRS) obtained nearly global coverage of Jupiter in the spectral range from 600 to 1400 cm-1 (16.7 to 7.1 microns) with a spectral resolution of 2.8 cm-1 and a spatial resolution of 2.5 to 3 degrees of great circle arc. Spectra from these maps have been inverted using a constrained linear inversion method to produce maps of of ammonia mole fraction and relative humidity in the 400 to 500 mbar pressure region.

We see strong meridional variations of the ammonia abundance, with maxima at the latitudes of the belts and minima in the zones. Ammonia is generally subsaturated, with relative humidities of 0.3 to 0.6, except near the equator where it is saturated (or slighly supersaturated). The zonal mean ammonia mole fraction is strongly anticorrelated with the zonal mean temperatures, suggesting that the meridional variations of both temperature and ammonia are the result of upwelling and subsidence associated with a very slow mean meridional circulation.

The Great Red Spot is visible in the ammnoia maps as a small region of enhanced ammonia, much smaller than the associated temperature anomaly, inside a broader region of low ammonia abundance.

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.