Transient Lunar Phenomena

Summary

For centuries, observers have reported brief glows, colours, flashes and hazes on the Moon: transient lunar phenomena. The briefest flashes are meteoroid impacts, recorded by instruments since 1999, but most of the longer-lasting glows in the catalogues rest on visual reports with no permanent record.

Spacecraft have detected radioactive radon gas escaping from the Moon, and the reports that survive a statistical test of reliability cluster where the gas does. A spectrum taken by a Soviet astronomer in 1958 was offered as evidence of lunar volcanism, and that interpretation is disputed. Whether the glows are events on the Moon or products of observers, telescopes and the Earth's air is still argued, and Arlin Crotts, whose statistical work argues for a reliable core of reports, says so himself.

What is documented

The catalogues. In July 1968 NASA published a Chronological Catalog of Reported Lunar Events (Technical Report R-277), compiled by Barbara Middlehurst of the University of Arizona, Jaylee Burley of NASA's Goddard Space Flight Center, Patrick Moore of Armagh Observatory and Barbara Welther of the Smithsonian Astrophysical Observatory. It lists reported events from 1540 to 1967. In 1978 W. S. Cameron of Goddard catalogued 1,468 descriptions, sorted them into reddish, bluish, brightenings, darkenings and gaseous phenomena, and weighted each for reliability from 0 to 5. She described them as "probably only a fraction of the number of anomalies actually seen." In the summary of Bonnie Buratti and colleagues (2000), the events "range from bright flashes, to reddish or bluish glows, to obscurations."

Kozyrev, 1958. The Soviet astronomer Nikolai Kozyrev reported "the ejection of gas from the central peak of the Alphonsus crater" on 3 November 1958, and further activity in the crater on 23 October 1959. He took these as evidence of volcanic processes on the Moon, and later reported gas activity in the crater Aristarchus in 1961 (Kozyrev, 1963). His 1958 spectrum was reported to show emission bands of molecular carbon, C2 (Crotts and Hummels, 2009). Encyclopaedia Britannica describes what he saw as a reddish mist covering part of the crater for a short time, and records that his volcanic interpretation has been disputed by astronomers.

Apollo 11, 1969. With Apollo 11 in lunar orbit, Mission Control told the crew that "lunar transient events" had been reported near Aristarchus. Neil Armstrong said he could not tell at that distance whether he was looking at Aristarchus, but saw an area "considerably more illuminated than the surrounding area" with "a slight amount of fluorescence to it". Buzz Aldrin said it seemed to be "reflecting some of the Earthshine" and that he was "not sure that I am really identifying any phosphorescence." The editors of NASA's Apollo Flight Journal note that Aristarchus "is the brightest crater on the face of the Moon."

Clementine. Amateur astronomers were mobilised to watch the Moon while the Clementine spacecraft mapped it. In four cases the spacecraft imaged a site both before and after an event the amateurs reported. "None of these four sets of images shows clear changes that could be attributed to the reported LTP," Buratti and colleagues wrote. The same study found that many reported events lie on bright, spectrally reddish deposits that may be volcanic ejecta, near the edges of the maria and in other regions of crustal weakness.

Gas from the Moon. Alpha-particle spectrometers on Apollo 15 and 16 and on Lunar Prospector recorded episodic releases of radon-222, a radioactive gas (Crotts, 2008). Peter Schultz and colleagues (2006) proposed that fresh-looking patches in the Ina structure were stripped by episodic out-gassing within the last 10 million years.

Impact flashes. A meteoroid striking the Moon makes a flash. The first unambiguous detections came during the Leonid meteor shower of 18 November 1999, when J. L. Ortiz and colleagues recorded five flashes, three of them seen simultaneously by other observers, each lasting less than 0.02 seconds (Ortiz and colleagues, 2000). A monitoring programme at NASA's Marshall Space Flight Center had recorded over 300 impacts since 2006, its team reported in 2014 (Suggs and colleagues, 2014). On 6 April 2026, during a nearly hour-long solar eclipse as the Artemis II spacecraft, the Moon and the Sun aligned, the crew reported six light flashes that NASA attributed to meteoroids striking the lunar surface. NASA said scientists would compare them with observations by amateurs watching at the same time.

The statistics. Arlin Crotts (2008) passed the report database through "a discriminating statistical filter robust against sites of spurious reports." The surviving sample correlates geographically with the radon releases and with the boundaries between maria and highlands, and the Aristarchus plateau remains "the prime TLP site". Crotts also wrote that most reports "are anecdotal, not independently verified, and involve no permanently recorded signal." Crotts and Cameron Hummels (2009) found that reports of red became far more common after 1955: 11 before 1956 and 52 afterwards, although the later years supply only a quarter of the sample; after 1955 about one report in five includes red. They attributed the change "presumably" to "a shift in the nature of observer reporting after 1955 rather than a change in the physics."

Leading explanations

Meteoroid impacts. Established, for brief flashes. Impact flashes have been detected with instruments, seen simultaneously by independent observers, and reported by the Artemis II crew during their flyby. A flash lasts a fraction of a second. Impacts explain the brief flashes in the record. They do not explain reported colours, glows and obscurations that persist.

Gas escaping from the interior (release documented; a link to the visual reports is a correlation, not established). Radon releases are measured facts. Crotts's filtered reports cluster where they occur, and Buratti and colleagues found reported events on possible volcanic deposits and at the edges of the maria. The link is statistical: it rests on where the reports cluster. Kozyrev's 1958 spectrum was offered as a direct record of gas, and his interpretation of it is disputed.

Observers, telescopes and the Earth's atmosphere (a documented factor; how much of the catalogue it explains is disputed). Most reports come from eyes at eyepieces, with nothing recorded. The colours reported changed with the decade rather than with the Moon, on Crotts and Hummels's reading. In four checks, Clementine found no change where amateurs had reported events. Crotts, whose filter is meant to isolate reliable reports, states that "even their reality is a point of dispute."

Other mechanisms (proposed, untested). Buratti and colleagues list bombardment by energetic particles and piezoelectric effects among the theories offered. None has been tied to a recorded event.

Current status

Partially explained. The brief flashes are meteoroid impacts, detected with instruments, confirmed by independent observers and now reported by a crew passing the Moon. Gas release from the Moon is measured. What remains open is the bulk of the historical catalogue: glows, colours and hazes reported by eye, mostly with no permanent record, and on one analysis shifting with the habits of observers. The case would change with a glow or haze recorded on camera from two separate sites, or a spacecraft measurement of gas release at the place and time of a reported event.

Last reviewed: September 2026. Records are provisional. Where the evidence changes, the entry changes. Found an error? Tell us.