Shape and Distribution of Rubble-pile Asteroid with Impact

摘要

The asteroid exploration spacecraft "HAYABUSA" took high resolution pictures of asteroid "IT0KAWA". ITOKAWA is a rubble-pile asteroid, whose shape and regolith size distribution are unique. These features are caused by composition of the Brazil-Nut effect and centrifugal force by spin. The Brazil-Nut effect is generally known as the phenomenon that causes larger particles to rise to the top of the shaken granular mixtures. In this study, the behaviors of various size particles on the ground or in the space are analyzed by numerical simulation using Multi-Particle model, which is model of a rubble-pile asteroid.At first, the behaviors of particles on the ground are simulated, and it is confirmed that Brazil-Nut effect occurs. Next, the behaviors of particles in the space are simulated. From this simulation results, the internal distribution of particles' upward trend is obtained. It is compared with the known information of ITOKAWA, and the inferred internal structure of rubble-pile asteroid is discussed.