It was caused by the impact of meteorites on the surface of the early moon. Because there is no thick atmosphere on the surface of the moon, when the meteorite falls to the surface of the early moon, the air will not slow down, but will accelerate, so the impact is great, which will arouse the fluctuation of the early moon surface and form a crater. Because there is no weathering of air and water vapor, the impact marks can be kept for a long time.