In Situ Exploration of Titan and Cometary Nucleus: Implication for Exobiology

Abstract

Titan, the largest satellite of Saturn, is in many aspects similar to the Earth. In spite of much lower temperatures and the absence of liquid water, because its environment is very rich in organics, and many couplings are involved in the various parts of its ''geofluid'', Titan is a reference for studying prebiotic chemistry on a planetary scale. The NASA-ESA Cassini-Huygens mission, which will send Cassini into orbit around Saturn and the Huygens probe into Titan's atmosphere, will systematically study organic chemistry in Titan's ''geofluid''. 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. Comets are also of prime importance. With their nuclei rich in C,H,N & O-containing compounds, cometary impacts may have largely contributed to the build up of organic matter on early Earth. The ESA Rosetta mission will include a spacecraft, which will approach and follow a comet for several years. It will carry landers which will be delivered to the surface of the comet, and will perform in situ studies of the cometary nucleus, including chemical (elemental and molecular) analysis. With the Horizon 2000 ESA program, these two very ambitious missions should provide many information of crucial importance for the field of exobiology.