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A transient lunar phenomenon (TLP) or lunar transient phenomenon (LTP) is a short-lived change in light, color or appearance on the surface of the Moon.

The term was created by Patrick Moore in his co-authorship of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968. Claims of short-lived lunar phenomena go back at least 1,000 years, with some having been observed independently by multiple witnesses or reputable scientists. Nevertheless, the majority of transient lunar phenomenon reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses to explain their origins. Most lunar scientists will acknowledge that transient events such as outgassing and impact cratering do occur over geologic time.

Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape. Two extensive catalogs of transient lunar phenomena exist, with the most recent tallying 2,254 events going back to the 6th century. An overview of the more famous historical accounts of transient phenomena include the following:

However, more recent studies suggest that it appears very unlikely the 1178 event was related to the formation of Crater Giordano Bruno, or was even a true transient lunar phenomenon at all. On November 26, 1540, a transient phenomenon appeared between Mare Serenitatis and Mare Imbrium. During the night of April 19, 1787, the British astronomer Sir William Herschel noticed three red glowing spots on the dark part of the Moon. On November 1–2, 1791, J.H.Schröter noticed the bowl-shaped crater Posidonius A on the floor of crater Posidonius without internal shadow. Barr, at the Lowell Observatory, Flagstaff, Arizona, manually recorded very bright red, orange, and pink colour phenomena on the southwest side of Cobra Head; a hill southeast of the lunar valley Vallis Schröteri; and the southwest interior rim of the Aristarchus crater. There's been some lunar transient events reported in the vicinity of Aristarchus." Astronomers in Bochum, West Germany, had observed a bright glow on the lunar surface—the same sort of eerie luminescence that has intrigued Moon watchers for centuries. During the Apollo 17 mission in December 1972, Lunar Module Pilot Harrison Schmitt observed a bright flash-like phenomenon north of crater Grimaldi while in orbit around the Moon (First Revolution, 21:11:09 GMT, December 10, 1972). On December 27, 1982, British Moon observer Harold Hill noticed the absence of the principal craterlet (Nasmyth A) on the floor of the crater Nasmyth.

Johann Hieronymus Schröter once saw for a short time on the lunar night side, near craters Agrippa and Godin, a minute point of light.

Explanations for the transient lunar phenomena fall in four classes: outgassing, impact events, electrostatic phenomena, and unfavorable observation conditions.

It has been suggested that effects related to either electrostatic charging or discharging might be able to account for some of the transient lunar phenomena.

It is possible that many transient phenomena might not be associated with the Moon itself but could be a result of unfavourable observing conditions or phenomena associated with the Earth.

The most significant problem that faces reports of transient lunar phenomena is that the vast majority of these were made either by a single observer or at a single location on Earth (or both). This does not necessarily imply that these reports were a result of observational error, as it is possible that outgassing events on the lunar surface might not leave a visible marker, but neither is it encouraging for the hypothesis that these were authentic lunar phenomena. Observations are currently being coordinated by the Association of Lunar and Planetary Observers and the British Astronomical Association to re-observe sites where transient lunar phenomena were reported in the past.

Professor Hakan Kayal of the Space Technology at Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany – Moon telescope set up in Spain, to investigate Transient Lunar Phenomena

Quick Facts

• Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape.
• Nevertheless, the majority of transient lunar phenomenon reports are irreproducible and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses to explain their origins.
• Most lunar scientists will acknowledge that transient events such as outgassing and impact cratering do occur over geologic time.
• The term was created by Patrick Moore in his co-authorship of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.
• There's been some lunar transient events reported in the vicinity of Aristarchus." Astronomers in Bochum, West Germany, had observed a bright glow on the lunar surface—the same sort of eerie luminescence that has intrigued Moon watchers for centuries.

Source material: Wikipedia - "Transient lunar phenomenon". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.