Largest satellite of Saturn and the only in the solar system having a dense atmosphere, Titan is one of the key planetary
bodies for astrobiological studies, due to several aspects. (i) Its analogies with planet Earth, in spite of much lower temperatures,
with, in particular, a methane cycle on Titan analogous to the water cycle on Earth. (ii) The presence of an active organic
chemistry, involving several of the key compounds of prebiotic chemistry. The recent data obtained from the Huygens instruments
show that the complex organic matter in Titan’s low atmosphere is mainly concentrated in the aerosol particles. The formation
of biologically interesting compounds may also occur in the deep water ocean, from the hydrolysis of complex organic material
included in the chrondritic matter accreted during the formation of Titan. (iii) The possible emergence and persistence of
Life on Titan. All ingredients which seem necessary for Life to appear and even develop – liquid water, organic matter and
energy – are present on Titan. Consequently, it cannot be excluded that life may have emerged on or in Titan. In spite of
the extreme conditions in this environment life may have been able to adapt and to persist. Many data are still expected from
the Cassini-Huygens mission and future astrobiological exploration mission of Titan are now under consideration. Nevertheless,
Titan already looks like another world, with an active organic chemistry, in the absence of permanent liquid water, on the
surface: a natural laboratory for prebiotic-like chemistry.
Keywords Astrobiology - Cassini-Huygens - Prebiotic chemistry - Primitive Earth - Tholins - Titan