144594 20260217205522.0 doi 10.1038/s42004-024-01248-6 sideral 139429 ART-2024-139429 eng Merino, P. n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics 2024 Access copy available to the general public Unrestricted Aliphatics prevail in asteroids, comets, meteorites and other bodies in our solar system. They are also found in the interstellar and circumstellar media both in gas-phase and in dust grains. Among aliphatics, linear alkanes (n-CnH2n+2) are known to survive in carbonaceous chondrites in hundreds to thousands of parts per billion, encompassing sequences from CH4 to n-C31H64. Despite being systematically detected, the mechanism responsible for their formation in meteorites has yet to be identified. Based on advanced laboratory astrochemistry simulations, we propose a gas-phase synthesis mechanism for n-alkanes starting from carbon and hydrogen under conditions of temperature and pressure that mimic those found in carbon-rich circumstellar envelopes. We characterize the analogs generated in a customized sputter gas aggregation source using a combination of atomically precise scanning tunneling microscopy, non-contact atomic force microscopy and ex-situ gas chromatography-mass spectrometry. Within the formed carbon nanostructures, we identify the presence of n-alkanes with sizes ranging from n-C8H18 to n-C32H66. Ab-initio calculations of formation free energies, kinetic barriers, and kinetic chemical network modelling lead us to propose a gas-phase growth mechanism for the formation of large n-alkanes based on methyl-methylene addition (MMA). In this process, methylene serves as both a reagent and a catalyst for carbon chain growth. Our study provides evidence of an aliphatic gas-phase synthesis mechanism around evolved stars and provides a potential explanation for its presence in interstellar dust and meteorites. info:eu-repo/grantAgreement/ES/AEI/PID2021-125309OA-I00 info:eu-repo/grantAgreement/ES/AEI/TED2021-129416A-I00 info:eu-repo/grantAgreement/EC/FP7/610256/EU/Gas and Dust from the Stars to the Laboratory: Exploring the NanoCosmos/NANOCOSMOS info:eu-repo/grantAgreement/ES/MCIU/RYC2018-024364-I info:eu-repo/grantAgreement/ES/MICINN/AEI/CNS2022-135658 info:eu-repo/grantAgreement/ES/MICINN/CEX2020-001039-S info:eu-repo/grantAgreement/ES/MCINN/EUR2021-122006 info:eu-repo/grantAgreement/ES/MICINN/FIS2016-77578-R info:eu-repo/grantAgreement/ES/MICINN/FIS2016-77726-C3-1-P info:eu-repo/grantAgreement/ES/MICINN/PGC2018-096047-B-I00 info:eu-repo/grantAgreement/ES/MICINN/RYC2020-029800-I info:eu-repo/grantAgreement/ES/MICINN/RYC2020-029810-I info:eu-repo/grantAgreement/ES/MINECO/CEX2018-000805-M info:eu-repo/grantAgreement/ES/MINECO/MAT2017-85089-C2-1-R info:eu-repo/grantAgreement/ES/MINECO/PID2020-113142RB-C21 info:eu-repo/semantics/openAccess by-nc-nd https://creativecommons.org/licenses/by-nc-nd/4.0/deed.es 6.2 2024 CHEMISTRY, MULTIDISCIPLINARY 50 / 239 = 0.209 2024 Q1 T1 1.485 2024 Biochemistry 2024 Q1 Materials Chemistry 2024 Q1 Environmental Chemistry 2024 Q1 Chemistry (miscellaneous) 2024 Q1 7.5 2024 info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Martínez, L. Santoro, G. Martínez, J. I. Lauwaet, K. Accolla, M. Ruiz del Arbol, N. Sánchez-Sánchez, C. Martín-Jimenez, A. Otero, R. Piantek, M. Serrate, D. (orcid)0000-0002-3260-9641 Lebrón-Aguilar, R. Quintanilla-López, J. E. Mendez, J. De Andres, P. L. Martín-Gago, J. A. 7, 165 (2024), 10 Communications Chemistry 2399-3669 1736839 http://zaguan.unizar.es/record/144594/files/texto_completo.pdf Versión publicada 2689732 http://zaguan.unizar.es/record/144594/files/texto_completo.jpg?subformat=icon icon Versión publicada oai:zaguan.unizar.es:144594 articulos driver 2026-02-17-20:29:16 ARTICLE