Abundances (given as colours) for H₂O ice as function of midplane density (x-axes), and temperature (y-axes) at different evolutionary steps for the reset scenario. From left to right panels: abundances from model runs with different parameters for grain–surface reactions: Cols. 1 and 2: b_qt = 1 Å, Cols. 3 and 4: b_qt = 1 Å, Cols. 1 and 3: with E_diff∕E_bin = 0.3, and Cols. 2 and 4: with E_diff∕E_bin = 0.5. From top to bottom panels: different evolutionary times, from 0.05 Myr (top) to 10 Myr (bottom). To the right of each plot is a colourbar, indicating the abundance level with respect to H_nuc for each colour. The chemical network utilised includes O₃ chemistry.