The Cassini spacecraft has revealed in 2006 the existence of lakes and seas in the polar regions of Titan, Saturn's major moon. These lakes would be filled by liquid methane and ethane, metastable on Titan's surface, such as water is on Earth. The rounded shape of the depressions in which they lie suggests a depression formation related to volcanic, thermokarstic, karstic or evaporitic processes. This thesis thus aims at understanding formation mechanisms and the development of the lacustrine depressions on Titan. The comparative study between Ontario Lacus, the largest lacustrine depression of the southern hemisphere, and the Etosha pan, a karsto-evaporitic depression of Namibia, suggests a formation scenario based on the dissolution of a superficial layer soluble in the liquids. This layer would form by (1) evaporitic crystallization under an arid climate of organic compounds dissolved in the liquids, and/or (2) surface accumulation of solid hydrocarbons synthesized in the atmosphere. The analogies between other lacustrine depressions on Titan and on Earth seem to indicate that dissolution and evaporation play a predominant role in the shaping and the evolution of Titan's surface. The comparison between Titan's and Earth's climates indicates the existence of an overall arid climate, more humid at high latitudes, compatible with the suggested karstic and evaporitic mechanisms. Future laboratory experiments, compositional mapping of the surface and geomorphological studies will bring further constraints on the link between these processes and Titan's climate.
