Methane plume observations on Mars: Difference between revisions
→Carbon 12 / 13 ratios
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Plants have values of from -10% or so down to -30% or less, clustering at around -13% and -28%<ref>O'Leary, Marion H. [http://sethnewsome.org/sethnewsome/EE_files/O%27Leary%201988.pdf "Carbon isotopes in photosynthesis."] Bioscience 38, no. 5 (1988): 328-336.</ref>. Algae have a similar range of values, from higher than -10% down to -30% or less. Coal and marine petroleum typically has values around -25%, terrestrial petroleum around -30%, and land plants average around -25%, but with a fair bit of variation around those figures. See figure 1 in this article.Park, Roderic, and Samuel Epstein. [https://authors.library.caltech.edu/62406/1/4259733.pdf "Metabolic fractionation of C13 & C12 in plants."] Plant Physiology 36, no. 2 (1961): 133.
However, sometimes abiotic methane can have carbon 13 depleted, for instance it can sometiems be depleted to as low as -50%
McDermott, Jill M., Jeffrey S. Seewald, Christopher R. German, and Sean P. Sylva. [http://www.pnas.org/content/pnas/112/25/7668.full.pdf "Pathways for abiotic organic synthesis at submarine hydrothermal fields."] Proceedings of the National Academy of Sciences 112, no. 25 (2015): 7668-7672.</ref>
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