SECONDARY CRATERS
Rocks thrown out during the formation of large impact craters often produce smaller, secondary craters when they fall back to the lunar surface. The 1-3-meter (3-10-foot) secondary craters in the foreground of this photograph have numerous rocks on their rims. These rocks were excavated from beneath the surface by the impacts.

ZAP PIT
Tiny impact craters, called "zap pits" are produced by small, high velocity particles and are common on the exposed faces of lunar rocks. This zap pit is 50 microns (2/1000 inch) in diameter and has a raised rim of glassy material caused by the impact.

Lunar Breccia Under a Microscope