37th DPS Meeting, 4-9 September 2005
Session 45 Titan's Atmosphere
Poster, Wednesday, September 7, 2005, 6:00-7:15pm, Music Recital Room

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[45.28] On the scattering properties of fractal tholin particle

Y.V. Skorov, H.U. Keller (Max-Planck-Institut für Sonnensystemforschung), M. Tomasko, L. Doose (Lunar and Planetary Laboratory, University of Arizona), DISR Team

As is well-known, the measurements carried out by the pioneer and Voyager spacecrafts showed simultaneous high degree polarization in light scattered from Titan near 90o phase angle and essential forward scattering. The former observation could only be matched by spherical particles having radii less about 0.1 \mum. The latter observation implies presence of particles with an effective radius of about 0.35\mum. This inconsistency was successfully remedied in a series of theoretical models of the Titan haze published since the early nineties. These models included the use of fractal aggregate haze particles consisting of small monomers of the required (prescribed) radius. Up to the Huygens mission there had not been enough observational data for a more developed haze model. The new DISR observations give a measurement of the monomer radius of 0.05 microns, in good agreement with previous estimates. The number of monomeres to fit the observed radiation field, however, is considerably higher (ca. 250) than microphysics models produce. The analysis uses essentially only the monomere radius and the number of monomeres. The scattering parameters of fractal particles depend on a multitude of additional physical characteristics such as the fractal dimension, fractal prefactor, different refractive indices (depending on the type of tholin assumed). Results of a systematic investigation of the resulting scattering properties based on the T-matrix method will be presented.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.