Assume that our Moon is hit by 25 million tiny meteorites every day. On average, it takes about 20 such impacts to obliterate a footprint left by an Apollo astronaut on the surface of the Moon. About how long would you estimate that it would take to erase evidence of a single footprint

1.1 year for any small rock.

Explanation:

As the moon is frequently hit by the asteroid that directly impacts the surface and creates creators. As per the question if it takes about 20 of such impacts to remove the footprints lt by the apollo moon lander. Then it should take about one year as the moon has no atmosphere and is exposed to the solar winds.