= Carbon monoxide–methane quenching
{title2=$\mathrm{CO}\rightleftharpoons\mathrm{CH}_4$ quenching}
<Carbon monoxide–methane quenching> preserves a transported carbon partition after local reactions become too slow to restore <thermochemical equilibrium>. A useful net reaction is
$$
\mathrm{CO}+3\mathrm{H}_2\rightleftharpoons\mathrm{CH}_4+\mathrm{H}_2\mathrm{O}.
$$
This is a net stoichiometric balance, rather than a single elementary reaction whose rate can simply be read from the equation. <Temperature>, <pressure> and the kinetic pathway determine the preferred composition and conversion time.
In models of <hot Jupiters>, vertical transport can maintain <methane> away from its local equilibrium abundance, while <atmospheric photochemistry> removes it at higher levels.<Disequilibrium Carbon, Oxygen, and Nitrogen Chemistry in the Atmospheres of HD 189733b and HD 209458b by Julianne I. Moses and others>[Abstract: transport-induced methane enhancement and high-altitude destruction]{ref} A methane band therefore probes both chemistry and circulation, rather than acting as a unique local <temperature> measurement.
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