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I was wondering, why are lighter isotopes (e.g. carbon-12 as opposed to carbon-13) preferentially used by life on Earth? Is their increased stability the only factor?

Thanks in advance!

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  • $\begingroup$ 99% of carbon is carbon-12, so it makes sense that it would incorporated by life in higher abundance. Perhaps I don't understand your question. $\endgroup$ – canadianer Oct 12 '18 at 23:59
  • $\begingroup$ I appreciate your response, but I think my question is poorly phrased. I am trying to understand why a negative carbon isotopic signature is suggestive of life. For example, if the carbon isotopic ratio of the methane detected on mars was showed to be more abundant in carbon-12 than carbon-13 (negative value), why is this suggestive of life? Do living systems prefer lighter isotopes? We only have Earth as a suitable analog, but is the a biologically reason why this is (and not merely a question of abundance)? Thanks a lot :) $\endgroup$ – JulianAngussmith Oct 13 '18 at 0:23
  • $\begingroup$ Hi Julian, interesting question. I look forward to reading a response. $\endgroup$ – Bell Oct 13 '18 at 2:07
  • $\begingroup$ I had never heard of this before, but after a bit of searching I think I found what you are referring to. I believe this Wikipedia article should answer your question. This is definitely out of my field, but I may try and formulate answer if someone more knowledgeable doesn’t come along. Interesting question! $\endgroup$ – canadianer Oct 13 '18 at 20:31
  • $\begingroup$ Thanks for you help! I look forward to reading an answer. $\endgroup$ – JulianAngussmith Oct 14 '18 at 2:06

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