3:45 PM - 4:00 PM
[PPS03-19] Change of asteroid rotation rates by collisional disruption: Implication for observation and collisional evolution
Keywords:asteroids, impact, rotation
Asteroids likely experienced collisional fragmentation and re-accumulation during the formation of the Solar System. Thus, comparison of their observational data obtained by ground-based telescopes and spacecraft with results of theoretical modeling is important to derive useful information and constraints on their collisional evolution. Among various observational data obtained for asteroids, in the present work, we focus on their rotation rates. Rotation rates have been measured for many asteroids, and their size-dependence has been examined in detail. For example, it is known that there is an apparent upper limit for the rotation rates in the size range of about several hundred meters to a few tens of kilometers in diameter, which is often called the spin barrier.
In the present work, we performed numerical simulation of impacts between asteroids. We used a Smoothed Particle Hydrodynamics code that can deal with rock fracture and friction in damaged rock (Sugiura et al. 2018). When two asteroids collide with a sufficiently low velocity, they merge and the orbital angular momentum of the impactor is added to the spin angular momentum of the target asteroid. However, when the impact velocity is higher and significant fragmentation takes place, those fragments that escape from gravity of the target asteroid can carry away a significant amount of angular momentum. Thus, the final rotation rate of the largest remnant body largely depends on the degree of fragmentation at impact. We performed simulations for various combinations of impact velocity, impact angle, pre-impact rotation rate of the target, and ratio of impactor mass to target mass, and examined characteristics of the change of asteroid rotation rates by disruptive impacts, such as the relationship between rotation rates of the largest remnant body after the impact and the degree of fragmentation. We will present results of these simulations and discuss comparison with observation as well as implication for collisional evolution of asteroids.
In the present work, we performed numerical simulation of impacts between asteroids. We used a Smoothed Particle Hydrodynamics code that can deal with rock fracture and friction in damaged rock (Sugiura et al. 2018). When two asteroids collide with a sufficiently low velocity, they merge and the orbital angular momentum of the impactor is added to the spin angular momentum of the target asteroid. However, when the impact velocity is higher and significant fragmentation takes place, those fragments that escape from gravity of the target asteroid can carry away a significant amount of angular momentum. Thus, the final rotation rate of the largest remnant body largely depends on the degree of fragmentation at impact. We performed simulations for various combinations of impact velocity, impact angle, pre-impact rotation rate of the target, and ratio of impactor mass to target mass, and examined characteristics of the change of asteroid rotation rates by disruptive impacts, such as the relationship between rotation rates of the largest remnant body after the impact and the degree of fragmentation. We will present results of these simulations and discuss comparison with observation as well as implication for collisional evolution of asteroids.