抄録
Japanese Hayabusa spacecraft found some features of boulders, such as clustering, lining up and size-sorting, on asteroid (25143) Itokawa. These features might be formed by granular convection and migrations triggered by micro body impacts. We also performed impact cratering experiments in the microgravity environment using a drop tower in order to establish the scaling law on crater size. Since the result is somewhat controversial, the conclusion is still not obtained. Understanding of particle and powder behavior in the microgravity and high-vacuum environments is necessary for elucidation of these phenomena. The microgravity experiment may be a new useful method for planetary sciences to elucidate surface processes on small bodies.
