1. Fifth Workshop on Titan Chemistry 11-14 April 2011, Kauai, Hawaii Organic Synthesis in the Atmosphere of Titan: Modeling and Recent Observations Yuk Yung (Caltech), M. C. Liang (Academia Sinica), X. Zhang (Caltech), J. Kammer (Caltech), D. Shemansky (SET)

3. Outline of Today’s Talk Titan: gas phase chemistry Aerosol formation Surface chemistry Synergism with lab data

4. Lorenz + Mitton 02

5. [Moses et al., JGR, 2005]

6. Solar Scattering Stellar Occultation J. Ajello

7. Mixing Ratios of Selected Species from Occultations

8. UVIS spectrum Liang et al. 2007 tholin CH 4 Impact: 514 km

9. Optical Depth Images

10. c Lavvas et al. 2008 EUV FUV autoauto Auto-catalytic process

11. 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.

12. Photochemical results Liang, Yung, Shemansky ApJ 2007 CH 4 ; hydrostatic CH 4 ; non-hydrostatic HC 3 N HCN C6N2C6N2 C6H6C6H6 C 6 N 2 ; condensation line

13. Gu et al. 2009

14. Model without Haze

16. C6HxC6Hx

18. Model with Haze

20. C6HxC6Hx

22. [Vuitton, et al., 2006]

24. Ion observation

25. Outline of Today’s Talk Titan: gas phase chemistry Aerosol formation Surface chemistry Synergism with lab data

26. Solar Scattering Stellar Occultation J. Ajello

27. Liang et al. 2007 tholin CH 4 Impact: 514 km Stellar Occultation

28. Single Scattering Albedo (SSA): SSA = Q s /Q e Important Parameters Goody and Yung 1989

29. Obs: 0.118 16 nm Refractive Index from Khare and Sagan (1984) SSA at 1875 Å

30. Shemansky et al. 2010

31. . 2 Trainer, et al 2006 Tomasko et al. 2008: ~100 km 50 nm radius 3000 monmers Comparisons

32. 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) ; 40 nm from Bar- Nun et al. (2008) Lavvas et al. (2008) at 520 km (ISS): ~40 nm Comparison of radius of tholins

33. T Tomasko et al. 2008

34. Outline of Today’s Talk Titan: gas phase chemistry Aerosol formation Surface chemistry Synergism with lab data

35. What happens to the Unsaturated Hydrocarbons at the Surface? COSMIC-RAY-MEDIATED FORMATION OF BENZENE ON THE SURFACE OF SATURN’S MOON TITAN Zhou et al. 2010

36. Benzene (PAH) Production on Surface Cosmic-ray flux on Titan’s surface (φ CR =1e9 eV cm −2 s −1 ) Yield of benzene from solid acetylene (from lab: Y = 5.6e-3 eV −1 ) Fraction of the surface of Titan covered by organics (F o =0.2) Fraction of organics that is acetylene (F a =0.2) Time for turnover of the surface by geological processes (τ=2e6 yrs, lowest estimate ) We get: M = 1.4e19 molecules cm −2 3.4 e−17 g cm−2 s−1

37. Outline of Today’s Talk Titan: gas phase chemistry Aerosol formation Surface chemistry Synergism with lab data

38. Inverse Model Parameter Estimate Predictions Adjoint Forcing Gradients (sensitivities) Optimization Forward Model Adjoint Model Observations Improved Estimate - t0t0 tftf tftf t0t0 Forward and adjoint models <-- time evolution profiles

39. Lab: Adamkovics et al. (2003) Liang et al. (submitted)

41. Jupiter (Moses 2005)

42. Titan (Moses 2005)

43. References Yung, Y. L., M. Allen, and J. P. Pinto. (1984). "Photochemistry of the Atmosphere of Titan: Comparison between Model and Observations." Astrophysical Journal Supplement Series 55(3): 465-506. Goody, R. M., and Y.L. Yung, Atmospheric Radiation: Theoretical Basis, 1989, Oxford University Press. Yung, Y. L., and W. D. DeMore, Photochemistry of Planetary Atmospheres, 1999, Oxford University Press.

44. Acknowledgements We appreciate discussions with kinetics groups of Prof Kaiser and Dr Sander, Mark Allen, Bob West, and support from NASA Cassini, OPR and PATM.