Catastrophic Disruption of Hollow Ice Spheres

Catastrophic disruption is a possible outcome of high-speed collisions in the solar system. The critical energy density Q* (impact energy/mass of the target), which is taken to mark the onset of catastrophic disruption, occurs when the largest intact fragment post-impact is 50% of the original target mass. Studies of Q* usually suppose the target body is a solid, rigid object. However, what if the body has a rigid shell and a hollow interior? Here, hollow ice spheres (a diameter of 19–20 cm with an ice thickness of 2.5–3.6 cm) were impacted at speeds up to ∼5 km/s. Catastrophic disruption occurred at Q* ∼ 25.5 ± 0.5 J kg−1, greater than that for similar size solid, or water-filled ice spheres (16–18 J kg−1). However, while the Q* value has increased, the actual impact energy associated with the new value of Q* has not, and the change in Q* arises due to the lower mass of the hollow target bodies