Distribution of ices in and around a molecular clump. The amount of ice layers covering the surface of dust for several species is plotted as a function of visual extinction. The left panel displays the environment of a clump at a time of t = 1.66 × 10⁷ yr of cloud evolution. The right panel shows a time snapshot of the clump after t = 1.82 × 10⁷ yr of cloud evolution. The colored curves are least-squares fits to simulation data points.