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E. L. Barth (Southwest Research Institute), O. B. Toon (LASP/Univ. of Colorado)
Temperatures and pressures above Titan's main haze layer are similar to those in the Earth's polar mesosphere where noctilucent clouds are known to form. Water vapor has also been measured in this region of Titan's atmosphere and is supplied through meteoric input. We use our Titan microphysics model to simulate the formation of water ice clouds in Titan's mesosphere. We consider two cases: one using the Yelle recommended model temperature profile and one with a temperature profile constructed from Cassini CIRS and UVIS observations. Both models produce a distinct water cloud layer with peak particle concentrations around 0.1 cm-3 at 500 km. Cloud particle sizes remain similar to those of the haze particles on with the water nucleates, about 0.1 microns in radius. Between 480 and 600 km, the ice cloud opacity exceeds the tholin haze opacity by a factor of 10 or more, such that the visible extended haze seen by Cassini is likely to be dominated by water ice.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.