A transient lunar phenomenon (TLP) is a sometimes inexplicable change of color or shape seen on the surface of the moon. Some may be caused by gas escaping from underground cavities after moonquakes. A number of these gaseous events have displayed a distinctive reddish hue, while others have appeared as white clouds or an indistinct haze. The majority appear to be associated with clefted crater floors, the edges of lunar mares, or in locations linked by geologists with volcanic activity.

In 1866, the experienced lifelong lunar observer and mapmaker Johann Friedrich Julius Schmidt made the claim that Linné crater had changed its appearance, from a normal, relatively deep crater to a mere white patch. A controversy arose and the claim remains unproven. No further changes have been observed in the crater; if true this would not be a transient change but a permanent one.

On November 2 1958, the Russian astronomer Nikolai A. Kozyrev observed an apparent outgassing of vapor near the central peak of Alphonsus crater. He took spectrograms that appeared to show the presence of carbon vapor.

Audouin Dollfus of the Observatoire de Paris observed a series of glows on the floor of Langrenus crater using the one-meter telescope on December 30, 1992. These glows changed form with time, and Professor Dollfus expressed the belief that this was likely a gaseous emission. The cracked floor of the crater may have been the source of the gas.

On April 23rd, 1999, amateur observers reported another TLP event in the vicinity of the "Cobra Head", the name for the bulbous start of the Vallis Schröteri adjacent to the Aristarchus crater. The Clementine spacecraft took before and after pictures of this region, and definite color changes were observed.

Other near-side craters where TLP have been reported are Grimaldi, Hercules, Plato, Theaetetus and Thales.

References

• The Kozyrev Observations of Alphonsus, PASP 71 (1959) 46
• Patrick Moore, On the Moon, Cassel & Co., 2001, ISBN 0304354694.

External links

• Chronological Catalog of Reported Lunar Events, July 1968 — NASA report on TLP sightings from 1540 to 1968
• "Light Side of the Moon" — An article from the Fortean Times for December 1997 by the astronomer Peter Grego
• Lunar Transient Phenomenon Research Program by David O. Darling.
• Transient Lunar Phenomena (and other weirdness) — Essay on TLP followed by links