From Wikipedia, the free encyclopedia
This map, based on a survey of 300 TLPs by Barbara Middlehurst and
shows the approximate distribution of observed events. Red-hued
events are in red; the remainder are in yellow.
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 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
experiments that could be used to distinguish among alternative
hypotheses. Few reports concerning these
phenomena are ever published in peer reviewed scientific journals, 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.
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
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
exposing his second spectrogram, he noticed "a marked increase in
the brightness of the central region and an unusual white color."
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
Observatory, Flagstaff, Arizona, manually recorded very bright
red, orange, and pink color 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
- 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.
- 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.
Explanations for the transient lunar phenomena fall in four
classes: outgassing, impact events, electrostatic phenomena, and
unfavorable observation conditions.
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 maria, 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
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
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
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
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.
Eight individual frames taken from a video of the lunar crater
Clavius showing the effect of the Earth's atmosphere on
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
It is possible that many transient phenomena might not be
associated with the moon itself but could be a result of
unfavorable 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 seeing). Other
non-lunar explanations include the viewing of Earth-orbiting
satellites and meteors or observational error.
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 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
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
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.
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