The impact scenario depicted is for a 21-km diameter impactor with a density of 2630 kg m3 and a speed of 12 km/s. Evolution of the crater up to 5 min after impact is depicted. Shown are cross-sections through the numerical simulation along the plane of trajectory, with \(x=0\) defined at the crater centre (measured at the pre-impact level); the direction of impact is from right to left. Colours and shading of material and tracer particles are the same as Fig. 2.