https://phys.org/news/2018-07-image-lunar-darkened-moon.html

For at least a thousand years people have claimed to witness short-lived phenomena occurring on the face of the moon. By definition these transient flashes are hard to study, and determining their cause remains a challenge.

For this reason scientists are studying these 'transient lunar phenomena' with great interest, not only for what they can tell us about the moon and its history, but also about Earth and its future.