One kind is the lines of ejecta thrown out along ballistic paths that are lines of secondary craters. On the Moon, these form the bright rays that extend for 10 to 30 crater diameters. This flowing material may form ridges and dunes that vary according to the velocity of the flow and the preexisting shape of the surface. The third type of deposit is the lines of ejecta radiating from the central peak. These materials are the last to be ejected from the crater.
Craters fall into three groups.
First, there are primary craters, which are generally randomly placed. Second, there are radiating and looped patterns of smaller craters surrounding the larger primary impact crater. These secondary craters in turn may have fans of ejecta thrown out from them in the direction away from the primary crater. These have a different form, are often alined along fractures, and have ejecta blankets of different style and form from those of impact craters. The far side, even more than the near, presents a tortured record of the bombardment suffered by the Moon throughout its history.