Top: minimum fragment size s_min in a 20 m/s collision (Eq. (4)) for three materials, as a function of collider size s₀. We have assumed η = 10^-2 and s_max = 2^{−1 / 3}s₀. The grey shaded areas are excluded because of mass conservation (left), and self-gravity (right). The dotted lines indicate the limit of Eq. (6). Bottom: critical energies versus size for equal-sized collisions. The energy needed to split a particle (e.g. Eq. (6)) is shown for η = 10^-3 (dotted) and η = 1 (dashed). The solid curves correspond to catastrophic fragmentation of aggregates (Beitz et al. 2011), and ice and basalt (Benz & Asphaug 1999), showing both the strength-dominated (small sizes) and self-gravity dominated regimes (large sizes).