Vertical profiles of H₂O and CO₂ derived from the time-dependent model assuming three different scenarios for a cometary impact on Uranus (cases 0–3 in Table 4) delivering 10 times less H₂ O than CO, and no CO₂. Available observational data on H₂O (Feuchtgruber et al. 1997) and best-fit matching the Spitzer measured column density (Orton et al. 2014b) are also shown. Photochemical, condensation, turbulent transport with K(z) = 5000 cm² s⁻¹, and molecular diffusion are taken into account.