Abstract:
Titan's surface chemical composition is still poorly identified and determined. On one hand, 
Huygens DISR instrument measured Titan's surface reflection and detected water ice, possibly
 mixed with an organic material absorber resembling laboratory analogues of Titan's aerosols.
 On the other hand, Cassini orbiter instruments observed Titanfs lakes and seas. VIMS detected 
liquid ethane in the southern lake Ontario Lacus, while Cassini RADAR measurements of northern
 Ligeia Mare suggest a predominant methane composition. 
Theoretical models predict liquid ethane-methane mixed compositions with additional species
 from atmospheric precipitation, including the refractory material of Titanfs aerosols. Generally,
 the solid organic aerosols and condensates of the atmospheric gases, accumulate in substantial
 amounts over the entire surface of Titan. 
Nonetheless, they may be chemically reprocessed by interaction with the water ice, or episodic
 liquid water, as well as with the liquid hydrocarbons. I will summarize what we know up to date
 about Titan's surface chemistry and will present laboratory studies I have been performed to try
 to understand surface chemical processes involving complex organics and to identify possible
 candidate components for the material on Titan's surface.