Why can an astronaut’s footprints stay on the Moon for so long?

There’s no wind or rain on the Moon to wipe the tracks away. Its atmosphere is far too thin to produce weather like ours, so the usual Earth-style cleanup never arrives. That helps preserve both astronaut tracks and much older impact craters. The surface still changes when objects from space strike it, so a footprint isn’t protected forever. But without wind and flowing water, a bootprint can outlast the person who made it by an extraordinary stretch of time.