Typical penetration snapshots of the projectile impacting onto granular beds and the resultant surface deformation. The panels (a)−(e) show the projectile impacting a hierarchical granular bed (wet grains), and the panels (g)−(k) present the impact onto a rigid glass beads bed. In both situations, the projectile was dropped from h = 80 mm (v₀ ≃ 1.2 and 1.4 m s⁻¹ for wet-grains and glass-beads cases, respectively). In the right panels (f,l), topview images of the impacted surfaces of (f) the hierarchical-granular-bed (wet) case and (l) the rigid-glass-beads case (after removing the projectile) are displayed. The impact points are marked with red laser points.