Time evolution, between 1 Myr and 5 Myr, of the dust surface density distribution (top) and the dust-to-gas ratio (bottom) assuming an initial dust-to-gas ratio of 0.01 (red) and 0.1 (blue), with darker lines for older ages. This plot shows how most of the dust evolution happens within the first few Myr. After that the dust density profile and the dust-to-gas ratio are independent of the assumed initial dust-to-gas ratio.