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Search for organic bioindicators in the solar system is a fundamental challenge for the space research community. If tremendous improvements have been achieved in detection, little or no research has been dedicated to extraction of the targets from the studied mineral matrices. Apart from thermodesorption, no extraction step was ever performed in situ within the context of biomarker detection experiments. This work presents an extraction protocol compatible with in situ space constraints. Two extraction methods, i.e., microwave-assisted extraction (MAE) and focused ultrasonic extraction (FUSE), were optimized with the aim of extracting molecules having an astrobiological interest (amino acids, nucleobases, polyaromatic carboxylic acids) and that are included in mineral matrices representative of the Martian soil. Higher efficiency was obtained with the FUSE method (20 kHz, amplitude 80%, pulse and relaxation 1 s each, for 10 min) with yields ranging from 30 to 95%. It was then applied on an Atacama Desert soil sample and Aguas Zarcas meteorite fragment. Both water-soluble and organic-soluble compounds present at trace levels were extracted using this short extraction time, and small amounts of sample and solvent compliant with in situ requirements (50 mg, 500 μL). This unique FUSE/derivatization-GC-MS approach gave similar yields to usual 24 h hot water extraction and increased the recovery of the target molecules compared to the derivatization-GC-MS method already used for in situ space experiments by a factor from 2 to 8. The data highlighted the suitability of a focused ultrasonic method for the extraction of trace organic compounds from extraterrestrial samples.

International audience; Molecular identification is a fundamental issue in astrobiology to investigate the routes of emergence of life on our planet involving in particular a potential seeding of extraterrestrial organic matter on the primitive Earth. However, this project encompasses major difficulties due to the low concentration of molecules present in bodies of the Solar System. This work proposes an integrative analytical workflow, no longer based on GC-MS instruments, to enhance comprehensive analysis of organic markers in these objects. Our strategy combines UPLC-HRMS and UPLC-MRM MS methods to bring both a broad molecular mapping and detailed data on indigenous compounds present in any extraterrestrial objects or laboratory analogs. Applied on water extracts from fresh meteorites, our workflow highlights a wide range of free molecules in the non-treated extracts and reveals the wide diversity of amino acid and nucleobase isomers that could lead to misinterpretation as far as the molecular composition of meteorite extracts cannot be anticipated. This strategy, never explored so far, would provide new clues for studying the organic matter in space and should offer new perspectives on its evolution and reactivity.