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Low 13C-13C abundances in abiotic ethane
Koudai Taguchi1, Alexis Gilbert2,3, Barbara Sherwood Lollar4,5
1Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, 152-8551, Japan. taguchi.k.ab@m.titech.ac.jp.
Nature Communications
|October 2, 2022
Summary
Clumped-isotope analysis of ethane reveals distinct carbon-13-carbon-13 signatures, enabling differentiation between abiotic, thermogenic, and microbially altered hydrocarbons for origin studies.
Area of Science:
- Geochemistry
- Astrobiology
- Organic Geochemistry
Background:
- Distinguishing biotic from abiotic organic compounds is crucial in geology and astrobiology.
- Stable isotopes are traditionally used but struggle to unequivocally identify abiotic hydrocarbons.
- Clumped-isotope analysis offers a more robust method, independent of starting material isotopic composition.
Purpose of the Study:
- To investigate the utility of carbon-13-carbon-13 clumped-isotope analysis for discriminating hydrocarbon origins.
- To analyze ethane synthesized abiotically, thermogenically, and after microbial alteration.
Main Methods:
- Performed carbon-13-carbon-13 clumped-isotope analysis on ethane samples.
- Utilized a collision frequency model to predict isotopic abundances.
- Analyzed ethane produced via methyl radical recombination and thermogenic processes.
- Examined ethane remaining after microbial oxidation.
Main Results:
- Abiotically synthesized ethane exhibited significantly lower carbon-13-carbon-13 abundances (anti-clumping) than thermogenic ethane.
- A collision frequency model supported the observed anti-clumping in abiotically produced ethane.
- Thermogenic ethane showed a near-stochastic carbon-13-carbon-13 distribution, likely from biological precursors.
- Microbially altered ethane displayed an exceptionally high carbon-13-carbon-13 signature.
Conclusions:
- Carbon-13-carbon-13 clumped-isotope analysis effectively distinguishes between thermogenic, microbially altered, and abiotic hydrocarbons.
- This isotopic signature provides a powerful new tool for determining the origin of organic molecules on Earth and potentially elsewhere in the universe.
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