What can we expect from the in situ chemical investigation of a cometary nucleus by gas chromatography: First results from laboratory studies

Comets are probably the most primitive bodies of the solar system, and they participated in the early bombardment of the primitive planets. Consequently, the knowledge of their composition can play a key role in our understanding of the solar system formation, the origin of the planetary volatile constituents, and the origin of the organics implied in terrestrial prebiotic chemistry. However, we still do not have any direct information about the molecular composition of the cometary nucleus. This is why the COmetary SAmpling and Composition experiment (COSAC), onboard the surface landing probe of the Rosetta cometary mission, is specifically devoted to the molecular and enantiomeric analysis of a cometary nucleus. This experiment includes a gas chromatograph instrument dedicated to the specific identification and quantification of the general molecular species present in samples collected at the nucleus surface. In order to evaluate the performances of the integrated chromatographic system which was selected for the flight model instrument, experiments were carried out with a laboratory set up that reproduced the flight configuration and mimicked the in situ operating conditions. The obtained results demonstrate the ability for the gas chromatograph to identify a wide range of organic and inorganic volatile compounds, even those present at trace level, within the constrained space operating conditions. The aim of this paper is to present, for the first time, the performances of this system and to discuss the potential role of in situ gas chromatographic measurements in the future cometary, planetological and prebiotic chemistry studies.