TIL according to NASA scientists the moon is only 65,000 years old.
Thickness of moon dust is measured at 65 millimeters (2½ inches) [https://ncse.com/cej/4/3/space-dust-moons-surface-age-cosmos].*
The rate of moon dust accumulation is 1 millimeter (0.04 inches) per 1,000 years [http://www.space.com/23694-moon-dust-mystery-apollo-data.html].**
1 millimeter / 1,000 years = 65 millimeters / 65,000 years
* “Kofahl and Segraves (p. 146), Whitcomb and DeYoung (pp. 94-95), Slusher (1980, p. 41), and Hahn (pp. 553-555) all repeat the same argument that the moon should have accumulated thick layers of dust in 4.5 billion years and that the 65 millimeters (2½ inches) actually there could have accumulated in less than ten thousand years.”
** “A revisited trove of data from NASA’s Apollo missions more than 40 years ago is helping scientists answer a lingering lunar question: How fast does moon dust build up?
The answer: It would take 1,000 years for a layer of moon dust about a millimeter (0.04 inches) thick to accumulate, the researchers found. That rate may seem slow by the standards of Earth but it’s 10 times faster than scientists had believed before, and it means moon dust could pose big problems for astronauts and equipment alike.”