Low 13C-13C abundances in abiotic ethane

Type Article
Date 2022-10
Language English
Author(s) Taguchi KoudaiORCID1, Gilbert AlexisORCID1, 2, Sherwood Lollar Barbara3, 4, Giunta Thomas3, 5, Boreham Christopher J.6, Liu QiORCID7, Horita Juske8, Ueno YuichiroORCID1, 2, 9
Affiliation(s) 1 : Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551, Japan
2 : Earth-Life Science Institute (WPI-ELSI), Tokyo Institute of Technology, Meguro, Tokyo, 152-8550, Japan
3 : Department of Earth Sciences, University of Toronto, Toronto, ON, M5S 3B1, Canada
4 : Institut de physique du globe de Paris (IPGP), Université Paris Cité, Paris, France
5 : Univ Brest, CNRS, Ifremer, Geo-Ocean, F-29280, Plouzané, France
6 : Geoscience Australia, Canberra, ACT, PO Box 378, 2601, Australia
7 : State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, 550081, China
8 : Department of Geosciences, Texas Tech University, Lubbock, TX, 79409, USA
9 : Institute for Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Natsushima-cho, Yokosuka, 237-0061, Japan
Source Nature Communications (2041-1723) (Springer Science and Business Media LLC), 2022-10 , Vol. 13 , N. 1 , P. 5790 (10p.)
DOI 10.1038/s41467-022-33538-9
WOS© Times Cited 1

Distinguishing biotic compounds from abiotic ones is important in resource geology, biogeochemistry, and the search for life in the universe. Stable isotopes have traditionally been used to discriminate the origins of organic materials, with particular focus on hydrocarbons. However, despite extensive efforts, unequivocal distinction of abiotic hydrocarbons remains challenging. Recent development of clumped-isotope analysis provides more robust information because it is independent of the stable isotopic composition of the starting material. Here, we report data from a 13C-13C clumped-isotope analysis of ethane and demonstrate that the abiotically-synthesized ethane shows distinctively low 13C-13C abundances compared to thermogenic ethane. A collision frequency model predicts the observed low 13C-13C abundances (anti-clumping) in ethane produced from methyl radical recombination. In contrast, thermogenic ethane presumably exhibits near stochastic 13C-13C distribution inherited from the biological precursor, which undergoes C-C bond cleavage/recombination during metabolism. Further, we find an exceptionally high 13C-13C signature in ethane remaining after microbial oxidation. In summary, the approach distinguishes between thermogenic, microbially altered, and abiotic hydrocarbons. The 13C-13C signature can provide an important step forward for discrimination of the origin of organic molecules on Earth and in extra-terrestrial environments.

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