Non-biological CH4 and CO2 in Earth's atmospheres
Abundant atmospheric methane from volcanism on terrestrial planets is unlikely and strengthens the case for methane as a biosignature
Magmatic volcanic outgassing on terrestrial planets can produce atmospheric methane and carbon dioxide with a thermodynamic model.We show, using a photochemical model, that high abiotic methane abundances produced by volcanoes would be accompanied by high carbon monoxide abundances, which could be a detectable falsepositive diagnostic.Our model suggests that volcanoes are unlikely to produce methane and carbon monoxide fluxes comparable to biological fluxes when the abundance implies a surface flux comparable to modern earth s biological methane and carbon monoxide fluxes.The difficulty of volcanically-generated methane and carbon monoxide atmospheressuitable for an origin of life may favor alternatives such as impact-induced reducing atmospheres.
