Dre Laetitia Guibourdenche - Distinguishing methane genetic origin: A Bayesian approach using clumped methane isotopes

Methane plays a key role in Earth's biogeochemical cycle and is also detected in the atmospheres of Mars, Enceladus, and Titan. Therefore, understanding methane's genetic origin is essential for constraining Earth's methane budget and assessing its potential biogenicity on other planets.
Beyond traditional isotopic measurements (ẟ13C and ẟD) and alkane molecular ratios (C1/C2+C3), advances in mass spectrometry over the past ten years have introduced clumped isotopes (Δ13CH3D and Δ12CH2D2) as a powerful tool to differentiate methane sources. However, despite recent progress, significant overlap in empirically-defined genetic fields for methane in both bulk and clumped isotope spaces remain.
To address this, we applied a Bayesian probabilistic framework to more accurately delineate microbial from thermogenic methane within the clumped isotope space. This approach offers a first order interpretation for methane’s isotopic composition and gives a degree of certainty to methane source attribution.