Water ice fraction of the planets for a model where the water ice line evolves in time as indicated in Fig. 1 and the planets are not migrating. The black and white lines correspond to the temperature at the given time t₀. As the growth of the planets takes several Myr, the ice line sweeps over the planet’s location also if the planet is initially at . Only planets forming exterior to T = 150 K can contain water ice. These planets can contain up to about ~35% of water ice, which is the maximum allowed in our chemical model. In the outer part at T < 70 K, the water ice fraction decreases again, because our chemical model allows for more CO production which binds oxygen efficiently resulting in a smaller water ice fraction.