Interpretation of chromatographic data recovered from space missions: decoding of complex chromatograms by Fourier analysis

In the near future, space probes will be used to investigate Titan and the P/Wirtanen comet because they are of interest for the fields of planetology and exo/astrobiology. One of the main objectives of these probes is to characterize the chemical composition of these extraterrestrial environments. The scientific payload of the probes will carry gas chromatography (GC) as one of the main experiments focused on this characterization through the separation and identification of the many species present in these environments. Despite the development of proper instrumentation for space applications, limitations and instrumental constraints imposed by the space environment prevent optimal separation of the analyzed species. Therefore, complex chromatograms are obtained from in situ space analysis and a mathematical approach is required to decode the signals and interpret all the data recovered by the space instruments. This paper describes a chemometric approach based on Fourier analysis and applications specifically developed to interpret the complex chromatograms that will be collected during space missions. This approach can be used to determine the number of species present in the chromatogram and other analytical properties, but can also be used to find repeated structures in the retention pattern, representative of common chemical features between the chromatographic peaks and the corresponding compounds. Therefore, within the framework of experiments for the calibration of the Cassini-Huygens GC-MS and ACP experiments, this approach was applied to the interpretation of data related to GC analysis of Titanʹs tholins produced in the laboratory. The procedure was also directly applied to isothermal chromatograms simulating the GC analyses of complex samples, obtained with standard species, which could be operated by the Rosetta Lander probe to investigate the nucleus of the comet P/Wirtanen (COSAC experiments). It is thus demonstrated that this method is helpful both in the chemical characterization of analogues of extraterrestrial matter produced in laboratory simulation aimed at calibrating space instruments and in the interpretation of data collected during space missions.