Mixing ratio profiles of H₂O, CO, and CO₂ ~ 50 yr after a comet nucleus of size 1.6 and 2.0 km impacted Uranus. The evolution time is tuned to reproduce the water ISO observations, which in turn produces carbon monoxide and carbon dioxide clearly above the available measurements. Photochemical, condensation, turbulent transport with K(z) =5000 cm² s⁻¹, and molecular diffusion are taken into account.