H₂O (solid lines) and CO₂ (dashed lines) profiles in a time-dependent Enceladus source model (H08 chemistry) compared to the observed profile of H₂O from (i) left panel: Herschel (S_a profile from Moreno et al. (2012); and (ii) right panel: Cassini/CIRS (Cottini et al. 2012) . Two initial conditions with different and enhanced OH input fluxes (1.0 × 10⁷ in black lines and 2.0 × 10⁷ cm^-2 s^-1 in red lines) are considered. Evolution times are adjusted so that the H₂O mole fraction above 300 km matches observations in the case of Herschel data and at 230 km in the case of Cassini/CIRS. The resulting (i.e., after t₀ yr of evolution) H₂O and CO₂ profiles are plotted with blue and green lines for the initial profiles 1 and 2, respectively (see text for more details). Upper limits on H₂O thermospheric abundance by Cui et al. (2009) are also shown as arrows.