Abstract
The HAYABUSA spacecraft is carrying out the in situ observations to understand the physical and chemical characteristics of asteroid 25143 Itokawa which belongs to NEAs. We attempt to quantita-tively model the crater size-frequency distributions observed on the Itokawa's surface. The crater size-frequency distribution of the Itokawa's surface would suggest conveniently the answer of argu-ment about the cause of the steep slope part of lunar and martian crater size-frequency distribution, because the small object has the lack of atmosphere and negligible gravity that lead to show little modification of crater and negligible effect of secondary craters.
