Formation rates of gas-phase species. The main formation rates of H₂O (top left), CO (top right), H₂CO (bottom left), and CH₃OH (bottom right) are plotted as a function of time in 10⁷ yrs. R_evap, the evaportation rate, is drawn for each specie, however, this rate is quite low for methanol such that the line does not fall within the limits of the plot. Other molecular reactions as well as photo-processes that result in the four mentioned species are given within the legend.