sirmitchell:

Space is nuts. This is moon dust under a microscope. 

The crater near top left, being only a few thousandths of an inch across, was probably made by a meteoroid only a tenth of a thousandth of an inch in diameter. On the Earth, such micrometeoroids would be slowed to negligible speeds by our atmosphere, and simply float to the surface. But the absence of a lunar atmosphere allows them to hit the surface at tens of thousands of miles per hour.