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Title: Which non-biological processes can mimic oxygen or methane biosignatures?
Plain: Oxygen and methane can sometimes be made by sunlight splitting water or by volcanic and rock-water chemistry, without life. A sign of life must be distinguishable from these.
Precise: Enumerate and quantify abiotic pathways that produce detectable O2, O3 or CH4 plus CO2 disequilibrium on rocky planets: H2O photolysis with hydrogen escape, CO2 photolysis in dry atmospheres, serpentinization and volcanic outgassing. For each, derive spectral discriminants (CO, O4, H2O abundance, redox state) measurable by a Habitable Worlds Observatory-class telescope. The answer is a classified list with abundance ranges and discriminants.
Settled by: Coupled photochemical, geochemical and escape models over the plausible parameter range, with synthetic spectra at expected telescope resolution and signal to noise.
Kind: well-posed
Answer type: classification
References: (empty)
Literature status: open
Status note: (empty)
Posed since: (empty)