Gas chromatography in space exploration - Capillary and micropacked columns for in situ analysis of Titan's atmosphere

The gas chromatography-mass spectrometry (GC-MS) experiment using capillary and micropacked columns is one of the main instruments of the Huygens probe of the Cassini-Huygens mission launched in October 1997 for the in situ analysis of Titan's atmosphere. Because of its composition and density the study of the atmosphere of Titan is of primary interest for understanding the prebiotic chemistry in the primitive Earth's environment. We describe here the GC subsystem of the GC-MS instrument with a particular emphasis on its exobiological implications. The GC subsystem includes three columns which operate in parallel: a carbon molecular sieve micropacked column is used for the separation of CO, N-2 and other permanent gases; a capillary column will separate the light hydrocarbons up to C-3; a second capillary column with a cyanopropyl dimethyl polysiloxane stationary phase will analyze the C-4-C-8 hydrocarbons and the low-molecular mass nitriles up to C-4. These heavier compounds will mainly result from the pyrolysis of the aerosols present in the atmosphere of Titan by using the aerosol collector pyrolyser instrument. (C) 1999 Published by Elsevier Science B.V. All rights reserved.