Transient Lunar Phenomenon - Description of Events

Description of Events

Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape. Cameron classifies these as (1) gaseous, involving mists and other forms of obscuration, (2) reddish colorations, (3) green, blue or violet colorations, (4) brightenings, and (5) darkenings. Two extensive catalogs of transient lunar phenomena exist, with the most recent tallying 2,254 events going back to the 6th century. Of the most reliable of these events, at least one-third come from the vicinity of the Aristarchus plateau.

A few of the more famous historical events of transient phenomena include the following:

• On June 18, 1178, five or more monks from Canterbury reported an upheaval on the moon shortly after sunset. "There was a bright new moon, and as usual in that phase its horns were tilted toward the east; and suddenly the upper horn split in two. From the midpoint of this division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals, and sparks. Meanwhile the body of the moon which was below writhed, as it were, in anxiety, and, to put it in the words of those who reported it to me and saw it with their own eyes, the moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then after these transformations the moon from horn to horn, that is along its whole length, took on a blackish appearance." In 1976, Jack Hartung proposed that this described the formation of the Giordano Bruno crater.

• During the night of April 19, 1787, the famous British astronomer Sir William Herschel noticed three red glowing spots on the dark part of the moon. He informed King George III and other astronomers of his observations. Herschel attributed the phenomena to erupting volcanoes and perceived the luminosity of the brightest of the three as greater than the brightness of a comet that had been discovered on April 10. His observations were made while an aurora borealis (northern lights) rippled above Padua, Italy. Aurora activity that far south from the Arctic Circle was very rare. Padua's display and Herschel's observations had happened a few days before the sunspot number had peaked in May 1787.

• In 1866, the experienced lunar observer and mapmaker J. F. Julius Schmidt made the claim that Linné crater had changed its appearance. Based on drawings made earlier by J. H. Schröter, as well as personal observations and drawings made between 1841 and 1843, he stated that the crater "at the time of oblique illumination cannot at all be seen" (his emphasis), whereas at high illumination, it was visible as a bright spot. Based on repeat observations, he further stated that "Linné can never be seen under any illumination as a crater of the normal type" and that "a local change has taken place." Today, Linné is visible as a normal young impact crater with a diameter of about 1.5 miles (2.4 km).

• On November 2, 1958, the Russian astronomer Nikolai A. Kozyrev observed an apparent half-hour "eruption" that took place on the central peak of Alphonsus crater using a 48-inch (122-cm) reflector telescope equipped with a spectrometer. During this time, the obtained spectra showed evidence for bright gaseous emission bands due to the molecules C₂ and C₃. While exposing his second spectrogram, he noticed "a marked increase in the brightness of the central region and an unusual white colour." Then, "all of a sudden the brightness started to decrease" and the resulting spectrum was normal.

• On October 29, 1963, two Aeronautical Chart and Information Center cartographers, James A. Greenacre and Edward 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. This event sparked a major change in attitude towards TLP reports. According to Willy Ley: "The first reaction in professional circles was, naturally, surprise, and hard on the heels of the surprise there followed an apologetic attitude, the apologies being directed at a long-dead great astronomer, Sir William Herschel." A notation by Winifred Sawtell Cameron states (1978, Event Serial No. 778): "This and their November observations started the modern interest and observing the Moon." The credibility of their findings stemmed from Greenacre's exemplary reputation as an impeccable cartographer. It is interesting to note that this monumental change in attitude had been caused by the reputations of map makers and not by the acquisition of photographic evidence.

• On the night of November 1–2, 1963, a few days after Greenacre's event, at the Observatoire du Pic-du-Midi in the French Pyrenees, Zdenek Kopal and Thomas Rackham made the first photographs of a "wide area lunar luminescence." His article in Scientific American transformed it into one of the most widely publicized TLP events. Kopal, like others, had argued that Solar Energetic Particles could be the cause of such a phenomenon.

• Project Moon-Blink was a draft NASA 1965-1966, for the exploration of unusual phenomena (anomalies) on the surface of the Moon. Work performed by Trident Engineering Associates (Annapolis, Maryland) under contract NAS 5-9613 dated June 1, 1965, Goddard Space Flight Center (Grinbelt, Maryland).

• During the Apollo 11 mission Houston radioed to Apollo 11: "We've got an observation you can make if you have some time up there. 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. The report was passed on to Houston and thence to the astronauts. Almost immediately, Armstrong reported back, "Hey, Houston, I'm looking north up toward Aristarchus now, and there's an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence."

• In 1992, Audouin Dollfus of the Observatoire de Paris reported anomalous features on the floor of Langrenus crater using a one-meter (3.2-foot) telescope. While observations on the night of December 29, 1992, were normal, unusually high albedo and polarization features were recorded the following night that did not change in appearance over the six minutes of data collection. Observations three days later showed a similar, but smaller, anomaly in the same vicinity. While the viewing conditions for this region were close to specular, it was argued that the amplitude of the observations were not consistent with a specular reflection of sunlight. The favored hypothesis was that this was the consequence of light scattering from clouds of airborne particles resulting from a release of gas. The fractured floor of this crater was cited as a possible source of the gas.