[M-ZZ40] International initiatives and cooperation in planetary defense

[MZZ40-P03] How a destructive impact changes asteroid velocity

*Takato Nishio¹, Keiji Ohtsuki¹, Keisuke Sugiura² (1.Graduate School of Science, Kobe University, 2.Advanced Technology R&D Center, Mitsubishi electric)

Keywords:Impact, Asteroids, Planetary defense

The dynamical and collisional evolution processes of small bodies are important fundamental processes to understand the formation of solar system. Since the velocity change of small bodies due to impacts is related to their dynamical evolution in various ways such as the disruption of binary asteroids/trans-Neptunian objects, it is important to understand how the velocity change of the largest remnant depends on various parameters. We use SPH impact simulations to examine change in velocity of asteroids after impacts and subsequent re-accumulation of fragments. We use 50 km basalt sphere in radius for target, and perform simulation with various impactor masses and impact velocities. The results show that the velocity change of the largest body after impact strongly depends on the impactor-to-target mass ratio and degree of disruption (the ratio of the mass of the largest remnant to the total mass). For less disruptive impacts, we found a small mass ratio impactor can make target accelerated in the direction of the impact velocity due to fragments ejected in the opposite direction of the impact velocity from near the impact point, as in the case of the impact experiment performed in the DART mission, while if the mass ratio is sufficiently large, the velocity change is rather smaller than the case of complete merger. On the other hand, in the case of catastrophic disruption, we found the velocity change is smaller than that of less disruptive impact. These results should be taken into account in kinetic impact related to planetary defense as well as in studies of dynamical evolution of asteroids.