Organic compounds in the Tarda C2 ungrouped carbonaceous chondrite: Evaluating the sources of contamination in a desert fall

Libby D. Tunney, Patrick J. A. Hill, Christopher D. K. Herd, Robert W. Hilts

Version of Record online: 03 March 2022


“Studying organic compounds in meteorites provides important insight into the chemical processes that occurred in the early solar system. Once meteorites reach the Earth’s surface, they are subject to terrestrial organic contamination that may confound the conclusions that we draw from meteorite organic analyses. Within this study, specimens of the Tarda C2 ungrouped carbonaceous chondrite, collected within a few days of its fall on August 25, 2020, from a barren desert in Morocco, were analyzed for their organic compound contents. In addition, a sand sample from the strewn field was analyzed to confirm the sources of a handful of contaminating compounds detected in the Tarda stones. Using dichloromethane (DCM) rinses of the Tarda stone exteriors and DCM and hot water extractions of meteorite specimen powders and sand sample, and analysis of the soluble organics by gas chromatography-mass spectrometry, we distinguish between extraterrestrial and contaminant sources for each organic compound. In this study, N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) was used to derivatize the hot water extractions to utilize its single-step derivatization reaction ability. The compounds determined to be intrinsic to Tarda include propanoic acid, propanedioic acid, butanedioic acid, fumaric acid, methylmaleic acid, threonine, proline, glycine, urea, and cyclic octaatomic sulfur. We detected numerous terrestrial organic compounds, all of which were traced back to the meteorites’ collection area, with several being confirmed in the sand sample. Our results have implications for best practices for the collection of freshly fallen meteorites, especially carbonaceous chondrites, as well as how specimens should be handled and curated after collection.”