Footprints on the Moon

The Moon has no rain, rivers, or ordinary wind, so astronaut tracks are not washed away or blown over as they would be on Earth. They are not permanent: micrometeoroid impacts very slowly rework the surface, and a large impact could erase a track locally. NASA estimates lunar surface erosion at roughly 1 mm per million years and says micrometeoroid bombardment would take millions of years to erode the tracks.