In situ sample treatment on Titan, aboard the DraMS experiment
Résumé
In 2027 NASA will launch a new exobiological mission to Titan: Dragonfly [1,2]. Onboard the DraMS instrument will aim to map the organic compounds present on the surface of the satellite and to study the fate of this organic matter towards a potential prebiotic chemistry [3,4]. To do so, DraMS is equipped with a gas chromatography instrument coupled to a mass spectrometer (GC-MS). In order to be analyzed, the samples taken by the DrACO module will be placed in an oven which will allow the sample treatment. Different techniques of sample treatment can be used: pyrolysis, derivatization and thermochemolysis. Pyrolysis allows to volatilize efficiently the organic content of the sample but has the disadvantage of degrading the original content. The derivatization allows to avoid the degradation of the labile molecules while allowing their volatilization. This derivatization will be realized thanks to the use of DMF-DMA (dimethylformamide dimethylacetal) [5]. This reagent allows to keep the asymmetry centers of the labile molecules while volatilizing them and thus allowing the separation of their enantiomers on a chiral column of Chirasil-Dex type. The last technique, thermochemolysis, is dedicated to more refractory compounds. It combines both pyrolysis and derivatization techniques by using TMAH (tetramethylammonium hydroxide) or TMSH (trimethylsulfonium hydroxide) and temperatures of about 500°C [6].
In order to optimize the treatment of DraMS samples, we studied the impact of each derivatization and thermochemolysis reagent on the identified organic targets (amino acids, nucleic bases, fatty acids, etc.) as well as using Titan analogues synthesized at LATMOS (UVSQ, France): Tholins [7].