Strange things have been seen on the moon for centuries -- usually flashes of light or color, or lights that appear to move across the lunar surface. These are known as transient lunar phenomena (TLP), and many of the reports, dating from 1540 to 1969, have been cataloged by NASA. But perhaps the best source for this kind of information is The Lunascan Project, an organized effort by amateur astronomers to record and document TLPs.
Such flashes of light and color could be attributed to meteor impacts or perhaps some kind of gaseous emissions, but harder to explain are the "fastwalkers" that have been videotaped by several amateur observers. This one, from the Lunascan Project, is a capture from a video taken by an amateur Japanese astronomer several years ago.
The dark object (circled in the upper photo and pointed out in the close-up in the lower photo) moved from north to south some unknown distance above the lunar surface. What could account for this anomaly? A satellite orbiting the moon? (It would have to be enormous to show up like this.) A satellite orbiting the Earth that happened to cross the the observer's field of view as he or she was videotaping the moon? So what could the unexplained object be?
