HR: 0830h
AN: P21C-02    [Abstracts]
TI: Radiative Transfer in Primordial Atmosphere of Titan
AU: * Adams, E
EM: eya@umich.edu
AF: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 United States
AU: Atreya, S
EM: atreya@umich.edu
AF: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 United States
AU: Kuhn, W
EM: wkuhn@umich.edu
AF: Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 United States
AB: In light of Huygens measurements, we present our improved model of thermal and photochemical evolution of Titan's atmosphere. Atreya et. al (1978) demonstrated that photolysis of ammonia on primordial Titan is capable of producing a nitrogen atmosphere substantially thicker than that measured by Voyager. E. Wilson (2001) carried this calculation one step further by including methane and water vapor explicitly in the ammonia photochemistry model, and arrived at a preliminary estimate of time required to accumulate different amounts of nitrogen. However, both models assumed an isothermal atmosphere. Since chemistry leading up to nitrogen occurs in the stratosphere, both the thermal structure and saturation effects are important for determining the time constants and amounts of nitrogen production. In this presentation, we discuss preliminary results of a radiative equilibrium model for the primordial middle and lower atmosphere of Titan. It includes CH₄, NH₃ and H₂O in solar proportions for its initial composition, and CH₄-CH₄ pressure induced absorption, which presently controls the thermal structure in the troposphere. The temperature in the stratosphere is controlled by the haze, and we explore the effects of a haze layer at various altitudes for accelerating conversion of ammonia to nitrogen. Furthermore, we include the effects of enhanced solar flux during the T-Tauri phase, which could speed up both the loss of nitrogen and conversion of ammonia to nitrogen. We are in the process of coupling the radiative transfer model to a comprehensive photochemical model (Wilson and Atreya, 2004) to access the roles of trace species other than those included in this calculation.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 3359 Radiative processes
DE: 5455 Origin and evolution
DE: 6006 Atmospheres--evolution
SC: Planetary Sciences [P]
MN: 2005 Joint Assembly