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C. Szopa, R. Sternberg, F. Raulin (LISA, Univ. Paris)
The knowledge of the cometary composition is of a great interest for planetary sciences and exobiology since it gives clues on the evolution of the solar system and the origin of life on Earth. These bodies contain compounds (such as HCN, HC3N, or HCHO) which may have been used in the prebiotic chemistry on Earth, and they are believed to carry the most primitive materials of the solar system. If spectroscopic observations are the most efficient for remote exploration, they do not allow direct detection of the cometary nucleus species. Therefore, only little information about the cometary nucleus chemical composition is yet available and the in situ analysis seems to be the best way to determine it. With this aim, the Surface Science Package of the ESA Rosetta mission (to be launched in 2003) will include the COmetary Sampling And Composition experiment (COSAC) containing a gas chromatograph (GC) dedicated to the separation and identification of both organic and inorganic compounds provided by the heating of nucleus material. Such an analytical technique has been chosen because it fulfills the general requirements of space instrumentation and allows to separate, identify and quantify chemical compounds. Being in charge of the selection of the GC columns subsystem (heart of the GC), we have to select the most appropriate chromatographic columns for the separation of the compounds suspected to be present in the nucleus. Results, taking into account the low space pressure reproducing the in situ analysises conditions, have already been obtained for several columns and show the capability, for the instrument, to identify new light species in the nucleus. We present these results which could open, in the future, new perspectives in cometary chemistry.