Composition and physico-chemical cycles of Titan's surface
Résumé
The knowledge of the composition and physical state of the surface of Titan has greatly improved in the last two years thanks to the various in-situ measurements of the Huygens probe (DISR, SSP, GCMS, . . . ) and the remote observations by several of the Cassini instruments (ISS, VIMS, SAR, . . . ), but also by ever powerful ground-based imagery and spectroscopic observations. Our understanding of the role of the surface and sub-surface in the physical and chemical cycles of the atmospheric species and aerosols has changed accordingly. Many old questions on these topics have been reformulated since the time of the oceanic view of Titan, new answer have been proposed but also several new problems have emerged from the data. In this solicited talk I will review the recent results on Titan's surface composition, physical state and distribution and will address their links with the atmospheric composition (gas, condensates, aerosols) and chemistry : do they provide a coherent view of Titan's surface and atmosphere system ? I will emphasize the role the surface materials (ices, simple and macromolecular organics, hydrocarbon liquids, . . . ) play, or may play, in the physical and chemical cycles of the atmospheric species. To conclude I will list some important open questions in this field that should be addressed by future observations, numerical models or laboratory experiments.