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I. de Pater (UC Berkeley), R.J. Sault, C. Engel (ATNF)
Prior to the Galileo probe entry in Jupiter's atmosphere, the ammonia abundance in the planet's deep atmosphere as derived from radio and infrared data was found to be close to the solar N value at P>3 bar and subsolar at P<2 bar. Analysis of the attenuation of the probe radio signal during its descent in Jupiter's atmosphere suggested NH3 to be 3.6 ±0.5 times solar N at P>8 bar. If the ammonia abundance is indeed this high, it has profound consequences for the formation theories of Jupiter, as summarized recently by Owen et al (1999). In earlier work, we investigated how to reconcile the probe data with other observations of Jupiter's ammonia profile. We assumed the high NH3 value to be globally representative of the ammonia abundance in Jupiter's deep atmosphere, as expected from dynamical considerations, and showed that to match Jupiter's disk-averaged microwave spectrum the ammonia abundance must, globally, decrease at pressures P < 4 bar, and reach subsolar (< 0.5 N) values at P < 2 bar. The big question is: why does the ammonia abundance decrease at altitudes well below the level where NH3-ice clouds form? To investigate this in more detail, we developed a technique to construct `topographic' maps of Jupiter's thermal radio emission: maps which contain both longitudinal and latitudinal structure. We present our first topographic map, obtained from 2-cm VLA data taken close in time with the Galileo probe entry. We compare this map with infrared IRTF data (from Orton and Ortiz), and derived the NH3 abundance in the radio hot spots.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.