An exobiological view of Titan and the Cassini-Huygens mission

The largest satellite of Saturn, Titan, is the only one in the solar system having a dense atmosphere. In many aspects it is similar to the Earth. Moreover, organic chemistry on Titan and prebiotic chemistry on Earth involve the same N-containing organic molecules : nitriles, including acetylenic nitriles and dinitriles, and their oligomers. Thus, in spite of much lower temperatures and the absence of liquid water, because of its environment very rich in organics, and the many couplings involved in the various parts of its "geofluid", Titan is a reference laboratory for studying prebiotic chemistry on a planetary scale. In the frame of the NASA-ESA Cassini-Huygens mission, which includes an orbiter (Cassini) around Saturn and a probe (Huygens) in Titan's atmosphere, organic chemistry in Titan's "geofluid" will be studied in great detail. In situ measurements, in particular from Huygens GC-MS and ACP instruments, will provide detailed analysis of the organics present in the air, aerosols, and surface. The mission will be launched in october 1997, for an arrival in the Saturn System in 2004. Thus, at horizon 2000, we can expect many information of crucial importance for the field of exobiology. (C) 1998 COSPAR. Published by Elsevier Science Ltd.