Spatial Pattern of Projectile Direction of Crater Rays on the Moon

Crater rays are among the most prominent lunar features that are radial or subradial to fresh impact craters. According to the latest more than 800 rayed impact craters with asymmetric ejecta in a latitude zone from 75°N to 75°S using Chang’E imageries, the spatial pattern of projectile direction of crater rays on the moon, namely the nearside-farside, leading side-trailing side and latitudinal variations, have been analyzed. The results suggest that: (1) the projectiles the rayed craters created mainly come from northeast direction while the number of projectiles coming from southwest direction is small; (2) in the nearside, projectiles from north direction can account for nearly 15 % of the whole projectiles. Yet in the farside, the number of projectiles makes up no more than 10 % of the total. On the other hand, the discrepancy is characterized by smaller frequency in the east direction on the trailing side while that is in higher frequency on the leading side direction; (3) with the latitude increases, the projectiles concentrate coming from one or two directions. The spatial variation suggests that the asteroid belt can well explain the dominant direction of projectiles concentrates in northeast direction and rayed craters on the Moon are formed mainly by near-Earth asteroids rather than comets with higher encounter velocities.