HR: 15:10h
AN: U23A-07 INVITED     [Abstracts]
TI: Titan Prebiotic-Like Chemistry And Astrobiology
AU: * RAULIN, F
EM: raulin@lisa.univ-paris12.fr
AF: LISA, CNRS & Univ. Paris 7 & Paris 12 61 Ave g‚n‚ral de gaulle, CRETEIL, 94000 France
AB: Since the first Voyager data , Titan, the largest satellite of Saturn and only satellite in the solar system having a dense atmosphere, became one of the key planetary bodies for astrobiological studies, due to: - its many analogies with planet Earth, in spite of much lower temperatures, - the already well observed presence of an active organic chemistry, involving several of the key compounds of prebiotic chemistry, in the gas phase but also assumed to occur in the solid phase through the haze particles - the potential development of a prebiotic chemistry in liquid water, with a possible water ocean in its internal structure, and the possible episodic formation of small liquid water bodies for short but not negligible time duration at the surface (from the melting of surface water ice by impact). Moreover, all ingredients which seems necessary for the emergence of Life are present on Titan :  liquid water : permanently as a deep sub-surface ocean, and episodically on the surface,  organic matter : in the internal structure, from chondritic materials, and in the atmosphere and on the surface, from the atmospheric organic chemistry  and energy : in the atmosphere (solar UV photons, energetic electrons from Saturn magnetosphere and cosmic rays) and, probably, in the environment of the sub-surface ocean (radioactive nuclei in the deep interior and tidal energy dissipation) as also supported by the likely presence of cryovolcanism on the surface Thus, 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. Before Cassini-Huygens arrival in the Saturn system, Titan was the source of many question of astrobiological interest, in particular: What is the source of atmospheric methane, and more generally the nature of the methane cycle on Titan? Are the models predicting water oceans in the internal structure correct ? What is their composition? Are the models predicting episodes of liquid water on the surface correct ? What is their frequency and duration? What is the complexity of its organic chemistry ? Are the haze particles made of complex organics, as predicted by laboratory models (named Titan's tholins)? Is there life on Titan ? These questions will be examined and some will be answered on the basis of the already available Cassini-Huygens data.
DE: 5200 PLANETARY SCIENCES: ASTROBIOLOGY
SC: Union [U]
MN: Fall Meeting 2005