Methane plume observations on Mars: Difference between revisions
→Challenges for interpreting carbon 12 /13 ratios from TGO
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==Carbon 12 / 13 ratios==
One way Trace Gas Orbiter might help to distinguish between biogenic and abiogenic sources of methane might be to measure the carbon-12 to carbon-13 ratio, which is expressed as a percentage relative to a reference standard {{Wikipedia|δ13C}}. Methanogens produce a gas which is much richer in the lighter carbon-12 than the products of serpentization.<ref name=Baucom/>. However abiotic sources can sometimes have similar results, and the ratios can be modified in various ways after formation. The TGO can also measure concentrations of ethane which may help with the analysis (very low in most microbial gases), but this also is not conclusive. It's ability to localize the measurements of plumes to regions of Mars may help but it is likely any results are preliminary and to need later work to interpret them.
Here carbon 12 is the light stable isotope of carbon which gets taken up preferentially by biological processes through {{Wikipedia|Kinetic fractionation|kinetic fractionation}}. The energy costs are lower if the carbon in the organism uses the lighter isotope. Carbon 13 is also stable but not so much favoured by biology. (Techy note, this is not to be confused with carbon 14 dating - carbon 14 is radioactive and unstable. Carbon 12 and 13 are both stable and don't decay at all.)
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They conclude:
{{quote|In conclusion, there will be a considerable degree of uncertainty regarding the origin of any methane detected by NOMAD. Interpreting methane-ethane data will not be easy, and probably there will be more questions than answers. Atmospheric and geological analysis can add insight into gas origins, but in future missions, direct gas detection in the Martian sub-soil, coupled with a better knowledge of subsurface geology (type of rocks, permeability,
== See also==
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