= Solution
* \b[Vertical chemical quenching:] when the <eddy mixing time> becomes shorter than the <chemical relaxation time>, transported gas retains a deeper abundance rather than reaching local <thermochemical equilibrium>. For example, <carbon monoxide–methane quenching> can maintain excess <carbon monoxide> in cool upper giant-planet gas where equilibrium favors <methane>.
* \b[<Atmospheric photochemistry>:] ultraviolet photons dissociate molecules and drive reaction networks away from thermal equilibrium. For example, irradiation of CH4-containing gas can produce <acetylene> and hydrocarbon precursors of an <atmospheric haze>.
* \b[<Horizontal chemical quenching>:] winds cross a day-night temperature gradient faster than reactions can reset the composition. For example, CO-rich dayside gas can reach a cooler <hot Jupiter> nightside without converting most of its carbon to CH4.
These are three distinct ways to maintain <disequilibrium chemistry in an exoplanet atmosphere>; each compares chemistry with a different transport or irradiation process.
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