 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2015/iii/paper-59/4/b/solution

Codex  0 Created 2026-10-03 Updated 2026-10-06

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.
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.
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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