Part I Determination of kinetic temperature at the top of the Titan atmosphere D. E. Shemansky† , J. A. Kammer ‡ , X. Zhang ‡ & Y. L. Yung‡ † Planetary and Space Science Division, Space Environment Technologies, Altadena, California, USA ‡ California Institute of Technology, Pasadena, California USA Jan 4-6 UVIS Science Team Meeting, Caltech, Pasadena, CA

Mixing Ratios of Selected Species from Occultations

Hydrocarbon Abundances from TB Encounter Tholin scale heights above 540 km are larger than any other species indicating formation at high altitudes and downward diffusion.

Optical Depth Images

Optical Depth Images

Density Profiles from Solar Occultations

Conclusions High altitude profiles of CH4 abundance show deviation from hydrostatic distribution indicating that chemistry combined with tidal effects is the controlling factor in vertical structure. Kinetic temperature of the upper atmosphere cannot be directly derived from the profiles. The vertical structure, with thickness as narrow as ~25km may be related to the combination of temperature dependent chemistry and gravitational tidal waves that in theory (see Strobel, 2006) show widths of ~50km.

Conclusions Distinct layers in the observed higher order hydrocarbons in the 500 – 600km region are readily observed. There is evidence that the vertical structure is seasonally dependent. Tholin vertical distributions show strong peaks just above 500 km, and large scale heights above 800 km. Below 400 km tholin scale heights conform to the atmospheric scale. Benzene has been measured at north latitudes with large scale height in disagreement with INMS results, and with density about 3 times below the projected INMS values. High altitude tholin is confined to the low latitude regions.

Tholins in the Upper Atmosphere of Titan Part II Tholins in the Upper Atmosphere of Titan Yuk Yung (Caltech) X. Zhang (Caltech) M. C. Liang (Academia Sinica, Taiwan) D. E. Shemansky (Space Environment Technologies)

Lorenz + Mitton 2002

Solar Scattering Stellar Occultation J. Ajello

UVIS spectrum Stellar Occultation Impact: 514 km tholin CH4 Liang et al. 2007

Scattered light : Shemansky et al. 2009 Calibration : 3-15-02 Rept by UVIS Team

SSA = Qs/Qe Important Parameters Single Scattering Albedo (SSA): Goody and Yung 1989

SSA at 1875 Å Obs: 0.118 Mie code calculation Refractive Index from Khare and Sagan (1984) 16 nm

Shemansky et al. 2010

. 2 Comparisons Tomasko et al. 2008: ~100 km 50 nm radius 3000 monmers Trainer, et al 2006 Tomasko et al. 2008: ~100 km 50 nm radius 3000 monmers

Summary Tholin Radius at 1040 km: 16 nm Liang et al. (2007) “guessed” 12.5 nm from Stellar Occultation only Comparable to 25 nm (in radius) from Trainer et al. (2006) Source of monomers at ~100 km from Tomasko et al. (2008)

Thanks Cassini UVIS (PI Esposito) PATM (Phil Crane) OPR (Curt Niebur)