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Control/Tracking Number: 07-RC-204-AAS-DPS
Activity: Research Contributed
Current Date/Time: 7/26/2007 6:28:32 PM
Titan Atmospheric Structure From 2000 Km To 300 Km: Models Compared To Cassini Uvis Observations
Author Block: D. E. Shemansky1, Y. L. Yung2, M. Liang3
1Space Environment Technologies, 2California Institute of Technology, 3Research Center for Environmental
Changes/Academia Sinica, Taiwan.
Cassini UVIS occultations at Titan have provided measurements of atmospheric structure in the altitude range 2000 km
- 300 km at several latitudes and longitudes. The molecular nitrogen abundance has been measured to 350 km above
the exobase with apparent temperatures close to 200 K. Vertical profiles of hydrocarbons and nitriles show distinct
dependence on latitude. Extinction by aerosols have been measured for the first time over the altitude range 100 km 300 km, indicating abundance latitude dependence below 500 km, and large scale heights above 500 km. Derived
vertical abundances of the higher order species shows significantly declining mixing ratios below altitudes ranging
from 750 km to 550 km. C2H2 follows the atmospheric scale of CH4 over the range 800 km to 1000 km. C2H4/CH4
abundance mixing ratios show latitudinal abundance variation by as much as a factor of 4. At latitude -35o the
abundance of CH4 is depleted in the sunlit atmosphere above 880 km relative to the darkside, and higher order species
by factors of 2 to 4. Below 880 km CH4 shows no longitude dependence, but higher order species remain depleted in
the subsolar atmosphere. Aerosol extinction is unchanged at latitude -35o, independent of longitude and the 2 year span
between observations. Model atmospheres have been calculated. Physical chemistry models including atmospheric
dynamics have been calculated using the observed latitudinally dependent distributions as constraints. Limits on the
processes of formation and lifetimes of aerosols based on the observed profiles will be discussed.
This work is supported by the Cassini and the NASA PATM Programs
Category (Complete): 31. Titan: Atmosphere (Chemistry, Clouds, and Dynamics)
Facility Keywords (Complete): {\it Facilities:} \facility{Cassini ()}
Presentation Preference (Complete): 1 - Oral Preferred
Additional Information (Complete):
I am willing to serve as a Chair: : Yes
(1) Area of Expertise: : 15. Gaint planets: Aurorae and Magnetospheres
(2) Area of Expertise: : 23. Mercury and Moon
(3) Area of Expertise: : 18. Laboratory Research
Status: Complete
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