Reconsideration of crater size-frequency distribution on the moon: effect of projectile population and secondary craters Original Research Article

The crater size-frequency distribution curve for the lunar surface has a bending point near 4 km in diameter. It is suggested that the steepening in the smaller diameter range is caused by the effects of secondary craters and/or size-frequency distribution of the impactors. In order to extract the fraction of the primary craters created by Near Earth Objects, among the primary-secondary mixture of km-size craters, we have examined the crater shape statistics using Clementine images of the lunar surface. We found that the size-frequency distribution of the craters with ellipticity smaller than 1.2 can be considered primary craters generated by impactors from interplanetary space.