36th DPS Meeting, 8-12 November 2004
Session 5 Uranus and Neptune
Oral, Monday, November 8, 2004, 1:30-3:00pm, Clark

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[5.04] Cloud Structure of Neptune and Uranus

A. S. Wong, S. K. Atreya (Univ. of Michigan)

Abundances of heavy elements below cloud levels provide critical constraints to the models of formation of giant planets and the origin of their atmospheres. In this study we present the results of an equilibrium cloud condensation model which calculates the bases and concentrations of methane ice, ammonia ice, ammonium hydrosulfide-solid, water ice, and aqueous-ammonia solution (``droplet") clouds. Due to their similar p-T tructures, the Neptune and Uranus results are similar. Based on the measured CH4 mixing ratio, the C/H at Neptune is 30-50x solar, and 20-30x solar at Uranus. Assuming similar enhancement for the other condensibles, as expected from formation models, we find that the base of the droplet cloud is at the 370 bars for 30x solar, and at 500 bar for 50x solar cases. On the other hand, noble gases and H2S can be accessed at much shallower levels, and still permit the retrieval of information critical to the formation of these planets and their atmospheres.

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