Transient lunar phenomenon
Encyclopedia
A transient lunar phenomenon (TLP), or lunar transient phenomenon (LTP), is a short-lived light, color, or change in appearance on the lunar surface
.
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. Few reports concerning these phenomena are ever published in peer review
ed scientific journals, and the lunar scientific community rarely discusses these observations.
Most lunar scientists will acknowledge that transient events such as outgassing
and impact cratering do occur over geologic time
: the controversy lies in the frequency of such events.
The term was created by Patrick Moore
during his co-authoring of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.
.
A few of the more famous historical events of transient phenomena include the following:
, or in other locations linked by geologists with volcanic activity. However, it should be noted that these are some of the most common targets when viewing the moon, and this correlation could be an observational bias.
In support of the outgassing hypothesis, data from the Lunar Prospector
alpha particle
spectrometer indicate the recent outgassing of radon
to the surface. In particular, results show that radon gas was emanating from the vicinity of the craters Aristarchus and Kepler
during the time of this two year mission. These observations could be explained by the slow and visually imperceptible diffusion of gas to the surface, or by discrete explosive events. In support of explosive outgassing, it has been suggested that a roughly 3 km- (1.9 mi-) diameter region of the lunar surface was "recently" modified by a gas release event. However, the age of this feature is believed to be about 1 million years old, suggesting that such large phenomena occur only infrequently.
spacecraft., India's Moon Impact Probe
and NASA's LCROSS
. Impact events leave a visible scar on the surface, and these could be detected by analyzing before and after photos of sufficiently high resolution. No impact craters having formed between the Apollo-era, Clementine
(global resolution 100 metre, selected areas 7-20 metre) and SMART-1 (resolution 50 metre) missions have been identified.
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. One possibility is that electrodynamic effects related to the fracturing of near-surface materials could charge any gases that might be present, such as implanted solar wind
or radiogenic daughter products. If this were to occur at the surface, the subsequent discharge from this gas might be able to give rise to phenomena visible from Earth. Alternatively, it has been proposed that the triboelectric
charging of particles within a gas-borne dust cloud could give rise to electrostatic discharges visible from Earth. Finally, electrostatic levitation of dust near the terminator could potentially give rise to some form of phenomenon visible from Earth.
). Other non-lunar explanations include the viewing of Earth-orbiting satellites and meteors or observational error.
One attempt to overcome the above problems with transient phenomena reports was made during the Clementine mission
by a network of amateur astronomers. Several events were reported, of which four of these were photographed both beforehand and afterward by the spacecraft. However, careful analysis of these images shows no discernible differences at these sites. 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. By documenting the appearance of these features under the same illumination and libration
conditions, it is possible to judge whether some reports were simply due to a misinterpretation of what the observer regarded as an abnormality. Furthermore, with digital images, it is possible to simulate atmospheric spectral dispersion
, astronomical seeing blur and light scattering by our atmosphere to determine if these phenomena could explain some of the original TLP reports.
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
.
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
Reproducibility
Reproducibility is the ability of an experiment or study to be accurately reproduced, or replicated, by someone else working independently...
and do not possess adequate control experiments that could be used to distinguish among alternative hypotheses. Few reports concerning these phenomena are ever published in peer review
Peer review
Peer review is a process of self-regulation by a profession or a process of evaluation involving qualified individuals within the relevant field. Peer review methods are employed to maintain standards, improve performance and provide credibility...
ed scientific journals, and the lunar scientific community rarely discusses these observations.
Most lunar scientists will acknowledge that transient events such as outgassing
Outgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...
and impact cratering do occur over geologic time
Lunar geologic timescale
The lunar geological timescale divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian , Nectarian, and Pre-Nectarian...
: the controversy lies in the frequency of such events.
The term was created by Patrick Moore
Patrick Moore
Sir Patrick Alfred Caldwell-Moore, CBE, FRS, FRAS is a British amateur astronomer who has attained prominent status in astronomy as a writer, researcher, radio commentator and television presenter of the subject, and who is credited as having done more than any other person to raise the profile of...
during his co-authoring of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.
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 plateauAristarchus (crater)
Aristarchus is a prominent lunar impact crater that lies in the northwest part of the Moon's near side. It is considered the brightest of the large formations on the lunar surface, with an albedo nearly double that of most lunar features. The feature is bright enough to be visible to the naked eye,...
.
A few of the more famous historical events of transient phenomena include the following:
- On June 18, 1178, five or more monks from CanterburyCanterburyCanterbury is a historic English cathedral city, which lies at the heart of the City of Canterbury, a district of Kent in South East England. It lies on the River Stour....
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 SchmidtJohann Friedrich Julius SchmidtJohann Friedrich Julius Schmidt was a German astronomer and geophysicist.-Biography:...
made the claim that Linné craterLinné (crater)Linné is a small lunar impact crater located in the western Mare Serenitatis. The mare around this feature is virtually devoid of other features of interest. The nearest named crater is Banting to the east-southeast....
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. KozyrevNikolai Aleksandrovich KozyrevNikolai Alexandrovich Kozyrev was a Russian astronomer/astrophysicist.-Biography:He was born in St. Petersburg, and by 1928 he had graduated from the Leningrad State University. In 1931 he began working at the Pulkovo Observatory, located to the south of Leningrad...
observed an apparent half-hour "eruption" that took place on the central peak of Alphonsus craterAlphonsus (crater)Alphonsus is an ancient impact crater on the Moon that dates from the immediate post-Nectarian era. It is located on the lunar highlands on the eastern end of Mare Nubium, west of the Imbrian Highlands, and slightly overlaps the crater Ptolemaeus to the north. The surface is broken and irregular...
using a 48-inch (122-cm) reflector telescope equipped with a spectrometerSpectrometerA spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...
. 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 ObservatoryLowell ObservatoryLowell Observatory is an astronomical observatory in Flagstaff, Arizona. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965....
, 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 SchröteriVallis SchröteriSchroter's Valley, frequently known by the Latinized name Vallis Schröteri, is a sinuous valley or rille on the surface of the near side of the Moon. It is located on a rise of continental ground, sometimes called the Aristarchus plateau, that is surrounded by the Oceanus Procellarum to the south...
; and the southwest interior rim of the Aristarchus craterAristarchus (crater)Aristarchus is a prominent lunar impact crater that lies in the northwest part of the Moon's near side. It is considered the brightest of the large formations on the lunar surface, with an albedo nearly double that of most lunar features. The feature is bright enough to be visible to the naked eye,...
. This event sparked a major change in attitude towards TLP reports. According to Willy LeyWilly LeyWilly Ley was a German-American science writer and space advocate who helped popularize rocketry and spaceflight in both Germany and the United States. The crater Ley on the far side of the Moon is named in his honor.-Life:...
: "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 KopalZdenek KopalZdeněk Kopal was a Czech astronomer who mainly worked in England.Kopal was born and grew up in Litomyšl . In his early astronomical career, he studied variable stars and in particular close eclipsing binary stars. He attended Cambridge University and later went to Harvard College Observatory not...
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 ParticlesSolar Energetic ParticlesSolar Energetic Particles are high-energy particles coming from the Sun which had been first observed in the early 1940s. They consist of protons, electrons and heavy ions with energy ranging from a few tens of keV to GeV...
could be the cause of such a phenomenon.
- During the Apollo 11Apollo 11In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...
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 ParisParis ObservatoryThe Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...
reported anomalous features on the floor of Langrenus craterLangrenus (crater)Langrenus is a prominent impact crater located near the eastern lunar limb. The feature is circular in shape, but appears oblong due to foreshortening. It lies on the eastern shore of the Mare Fecunditatis...
using a one-meter (3.2-foot) telescope. While observations on the night of December 29, 1992, were normal, unusually high albedoAlbedoAlbedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...
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 reflectionSpecular reflectionSpecular reflection is the mirror-like reflection of light from a surface, in which light from a single incoming direction is reflected into a single outgoing direction...
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.
Explanations
Explanations for the transient lunar phenomena fall in four classes: outgassing, impact events, electrostatic phenomena, and unfavorable observation conditions.Outgassing
Some TLPs may be caused by gas escaping from underground cavities. A number of these gaseous events are purported to display a distinctive reddish hue, while others have appeared as white clouds or an indistinct haze. The majority of TLPs appear to be associated with floor-fractured craters, the edges of lunar mariaLunar mare
The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...
, or in other locations linked by geologists with volcanic activity. However, it should be noted that these are some of the most common targets when viewing the moon, and this correlation could be an observational bias.
In support of the outgassing hypothesis, data from the Lunar Prospector
Lunar Prospector
The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon, including mapping of surface composition and possible...
alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
spectrometer indicate the recent outgassing of radon
Radon
Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Its most stable isotope, 222Rn, has a half-life of 3.8 days...
to the surface. In particular, results show that radon gas was emanating from the vicinity of the craters Aristarchus and Kepler
Kepler (lunar crater)
Kepler is a lunar impact crater that lies between the Oceanus Procellarum to the west and Mare Insularum in the east. To the southeast is the crater Encke....
during the time of this two year mission. These observations could be explained by the slow and visually imperceptible diffusion of gas to the surface, or by discrete explosive events. In support of explosive outgassing, it has been suggested that a roughly 3 km- (1.9 mi-) diameter region of the lunar surface was "recently" modified by a gas release event. However, the age of this feature is believed to be about 1 million years old, suggesting that such large phenomena occur only infrequently.
Impact events
Impact events are continually occurring on the lunar surface. The most common events are those associated with micrometeorites, as might be encountered during meteor showers. Impact flashes from such events have been detected from multiple and simultaneous Earth-based observations. Tables of impacts recorded by video cameras exist for years since 2005 many of which are associated with meteor showers. Furthermore, impact clouds were detected following the crash of ESA's SMART-1SMART-1
SMART-1 was a Swedish-designed European Space Agency satellite that orbited around the Moon. It was launched on September 27, 2003 at 23:14 UTC from the Guiana Space Centre in Kourou, French Guiana. "SMART" stands for Small Missions for Advanced Research in Technology...
spacecraft., India's Moon Impact Probe
Moon Impact Probe
The Moon Impact Probe developed by the Indian Space Research Organisation , India's national space agency, was a lunar probe that was released by ISRO's Chandrayaan-1 lunar remote sensing orbiter which in turn was launched, on 22 October 2008, aboard a modified version of ISRO's Polar Satellite...
and NASA's LCROSS
LCROSS
The Lunar Crater Observation and Sensing Satellite was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the moon. The main LCROSS mission objective was to explore the presence of water ice...
. Impact events leave a visible scar on the surface, and these could be detected by analyzing before and after photos of sufficiently high resolution. No impact craters having formed between the Apollo-era, Clementine
Clementine mission
Clementine was a joint space project between the Ballistic Missile Defense Organization and NASA...
(global resolution 100 metre, selected areas 7-20 metre) and SMART-1 (resolution 50 metre) missions have been identified.
Electrostatic phenomena
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
or radiogenic daughter products. If this were to occur at the surface, the subsequent discharge from this gas might be able to give rise to phenomena visible from Earth. Alternatively, it has been proposed that the triboelectric
Triboelectric effect
The triboelectric effect is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated...
charging of particles within a gas-borne dust cloud could give rise to electrostatic discharges visible from Earth. Finally, electrostatic levitation of dust near the terminator could potentially give rise to some form of phenomenon visible from Earth.
Unfavourable observation conditions
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. For instance, some reported transient phenomena are for objects near the resolution of the employed telescopes. The Earth's atmosphere can give rise to significant temporal distortions that could be confused with actual lunar phenomena (see astronomical seeingAstronomical seeing
Astronomical seeing refers to the blurring and twinkling of astronomical objects such as stars caused by turbulent mixing in the Earth's atmosphere varying the optical refractive index...
). Other non-lunar explanations include the viewing of Earth-orbiting satellites and meteors or observational error.
Debated status of TLPs
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). The multitude of reports for transient phenomena occurring at the same place on the moon could be used as evidence supporting their existence. However, in the absence of eyewitness reports from multiple observers at multiple locations on Earth for the same event, these must be regarded with caution. As discussed above, an equally plausible hypothesis for the majority of these events is that they are caused by the terrestrial atmosphere. If an event were to be observed at two different places on Earth at the same time, this could be used as evidence against an atmospheric origin.One attempt to overcome the above problems with transient phenomena reports was made during the Clementine mission
Clementine mission
Clementine was a joint space project between the Ballistic Missile Defense Organization and NASA...
by a network of amateur astronomers. Several events were reported, of which four of these were photographed both beforehand and afterward by the spacecraft. However, careful analysis of these images shows no discernible differences at these sites. 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
Association of Lunar and Planetary Observers
The Association of Lunar and Planetary Observers is an international scientific and educational organization established in March, 1947 in the United States by Walter H. Haas, and later incorporated in 1990...
and the British Astronomical Association
British Astronomical Association
The British Astronomical Association is the senior national association of amateur astronomers in the UK.-Function:It encourages observational astronomy by non-professionals in areas which cannot be covered by professional observatories...
to re-observe sites where transient lunar phenomena were reported in the past. By documenting the appearance of these features under the same illumination and libration
Libration
In astronomy, libration is an oscillating motion of orbiting bodies relative to each other, notably including the motion of the Moon relative to Earth, or of Trojan asteroids relative to planets.-Lunar libration:...
conditions, it is possible to judge whether some reports were simply due to a misinterpretation of what the observer regarded as an abnormality. Furthermore, with digital images, it is possible to simulate atmospheric spectral dispersion
Dispersion (optics)
In optics, dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency, or alternatively when the group velocity depends on the frequency.Media having such a property are termed dispersive media...
, astronomical seeing blur and light scattering by our atmosphere to determine if these phenomena could explain some of the original TLP reports.
External links
- Lunar Transient Phenomena NASA feature story
- Lunar transient phenomena Association of Lunar & Planetary Observers
- NASA - Lunar Impact Monitoring Program