Snapshots of crater formation at 0 (A), 0.8 (B), 1.4 (C), and 5.6 (D) seconds after the impact. Each plot is divided into two panels. The left panels show the results for an impact speed of 45 cm/s, and the right panels refer to an impact speed of 65 cm/s. The projectile is 10 cm in diameter. The colours refer to the different materials (blue for the projectile, and yellow for the target) that differ in porosity. The strength material model for this simulation was Drucker-Prager.