Methane plume observations on Mars: Difference between revisions
→Challenges for interpreting carbon 12 /13 ratios from TGO
Line 44:
The carbon 13 can be depleted by abiotic proceses. It can also be depleted in methane produced by heating organics (thermogenic methane) and meanwhile, sometimes methane produced by life is not depleted in carbon 13. It also depends on the isotopic composition of its precursor. Magmatic carbon, for instance, might be depleted in carbon 13. Also processes that alter the methane such as oxidation by hydrogen peroxide can deplete the carbon 12 turning a possible microbial signature into one that looks abiotic. Meanwhile diffusion through permeable rock can increase the carbon 12 levels to mimic a biogenic signature - this could be the dominant process if the methane has to pass through an almost impenetrable "cap" on its way to the surface.<ref name=nomadmethane>[https://meetingorganizer.copernicus.org/EPSC2018/EPSC2018-211-3.pdf NOMAD on ExoMars Trace Gas Orbiter: status and preliminary results] Ann C. Vandaele., Jose-Juan Lopez-Moreno, GiancarloBellucci, Manish R. Patel, FrankDaerden, IanR. Thomas,Eddy Neefs, BojanRistic, Sophie Berkenbosch, Bram Beeckman, Roland Clairquin, Claudio Queirolo and the NOMAD Team, EPSC Abstracts,Vol. 12, EPSC2018-211-3, 2018, European Planetary Science Congress 2018</ref>
[[Image:NOMAD methane.png|thumb|"Figure 1: Ranges of terrestrial δ13C-CH4 and C1/C2 values for the three classes of methane origin (microbial, thermogenic, abiotic), their possible extension to Mars (thin arrows) and po-tential post-genetic modifications (dashed ar-rows). "<ref name=nomadmethane/>]]
The NOMAD instrument on Mars can measure the concentrations of other gases such as ethane. This could help as microbial gases typically have ethane concentrations of a thousandth or less.
| |||