Transient lunar phenomenon

This map, based on a survey of 300 TLPs by Barbara Middlehurst and Patrick Moore, 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 surface of the Moon.

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 to explain their origins.

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 in his co-authorship of NASA Technical Report R-277 Chronological Catalog of Reported Lunar Events, published in 1968.[1]

Description of events

Reports of transient lunar phenomena range from foggy patches to permanent changes of the lunar landscape. Cameron[2] 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,[1][2] 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 accounts of transient phenomena include the following:


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. 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, 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.[23] 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.[24][25] 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.[26][27][28][29] Tables of impacts recorded by video cameras exist for years since 2005 many of which are associated with meteor showers.[30] Furthermore, impact clouds were detected following the crash of ESA's SMART-1 spacecraft,[31] 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 formed between the Clementine (global resolution 100 metre, selected areas 7-20 metre) and SMART-1 (resolution 50 metre) missions have been identified.

Electrostatic phenomena

Eight individual frames taken from a video of the lunar crater Clavius showing the effect of the Earth's atmosphere on astronomical images

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.[32] 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.[33] Finally, electrostatic levitation of dust near the terminator could potentially give rise to some form of phenomenon visible from Earth.[34]

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 (an effect known as astronomical seeing). Other non-lunar explanations include the viewing of Earth-orbiting satellites and meteors or observational error.[28]

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 some 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 sites.[35] 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.

See also


Cited references

  1. 1 2 Barbara M. Middlehurst; Burley, Jaylee M.; Moore, Patrick; Welther, Barbara L. (1967). "Chronological Catalog of Reported Lunar Events" (PDF). Astrosurf. NASA. Retrieved 26 December 2015.
  2. 1 2 W. Cameron. "Analyses of Lunar Transient Phenomena (LTP) Observations from 557–1994 A.D." (PDF).
  3. Jack B. Hartung (1976). "Was the Formation of a 20-km Diameter Impact Crater on the Moon Observed on June 18, 1178?". Meteoritics. 11: 187–194. Bibcode:1976Metic..11..187H. doi:10.1111/j.1945-5100.1976.tb00319.x.
  4. "The Giordano Bruno Crater". BBC.
  5. Kettlewell, Jo (1 May 2001). "Historic lunar impact questioned". BBC. Retrieved 13 July 2013.
  6. "The Mysterious Case of Crater Giordano Bruno". NASA. Retrieved 13 July 2013.
  7. Herschel, W. (1956, May). Herschel’s ‘Lunar volcanos.’ Sky and Telescope, pp. 302-304. (Reprint of An Account of Three Volcanos in the Moon, William Herschel’s report to the Royal Society on April 26, 1787, reprinted from his Collected Works (1912))
  8. Kopal, Z. (December 1966). "Lunar flares". Astronomical Society of the Pacific Leaflets. 9: 401–408.
  9. J. F. Julius Schmidt (1867). "The Lunar Crater Linne". Astronomical Register. 5: 109–110. Bibcode:1867AReg....5..109S.
  10. Dinsmore Alter, Dinsmore (1959). "The Kozyrev Observations of Alphonsus". Publications of the Astronomical Society of the Pacific. 71: 46–47. Bibcode:1959PASP...71...46A. doi:10.1086/127330.
  11. Greenacre, J. A. (December 1963). "A recent observation of lunar colour phenomena". Sky & Telescope. 26 (6): 316–317. Bibcode:1963S&T....26..316G.
  12. Zahner, D. D. (1963–64, December–January). Air force reports lunar changes. Review of Popular Astronomy, 57(525), 29, 36.
  13. O'Connell, Robert; Cook, Anthony (August 2013). "Revisiting The 1963 Aristarchus Events". Journal of the British Astronomical Association. 123 (4): 197–208.
  14. Ley, W. (1965). Ranger to the moon (p. 71). New York: The New American Library of World Literature, Inc.
  15. Cameron, W. S. (1978, July). Lunar transient phenomena catalog (NSSDC/WDC-A-R&S 78-03). Greenbelt, MD: NASA Goddard Space Flight Center
  16. Meaburn, J. (June 1994). "Z. Kopal". Quarterly Journal of the Royal Astronomical Society. 35: 229–230. Bibcode:1994QJRAS..35..229M.
  17. Moore, P. (2001). "Thomas Rackham, 1919–2001". Journal of the British Astronomical Association. 111 (5): 291. Bibcode:2001JBAA..111..291M.
  18. Kopal, Z.; Rackham, T. W. (1963). "Excitation of lunar luminescence by solar activity". Icarus. 2: 481–500. Bibcode:1963Icar....2..481K. doi:10.1016/0019-1035(63)90075-7.
  19. Kopal, Z. (May 1965). "The luminescence of the moon". Scientific American. 212 (5): 28. doi:10.1038/scientificamerican0565-28.
  20. Kopal, Z.; Rackham, T. W. (March 1964). "Lunar luminescence and solar flares". Sky & Telescope. 27 (3): 140–141. Bibcode:1964S&T....27..140K.
  21. Time Magazine, Friday, Jul. 25, 1969 "A GIANT LEAP FOR MANKIND"
  22. Audouin Dollfus, A (2000). "Langrenus: Transient Illuminations on the Moon". Icarus. 146 (2): 430–443. Bibcode:2000Icar..146..430D. doi:10.1006/icar.2000.6395.
  23. S. Lawson, Stefanie L.; W. Feldman; D. Lawrence; K. Moore; R. Elphic & R. Belian (2005). "Recent outgassing from the lunar surface: the Lunar Prospector alpha particle spectrometer". J. Geophys. Res. 110: E09009. Bibcode:2005JGRE..11009009L. doi:10.1029/2005JE002433.
  24. G. Jeffrey Taylor (2006). "Recent Gas Escape from the Moon". Planetary Science Research Discoveries.
  25. P. H., Schultz; Staid, M. I. & Pieters, C. M. (2006). "Lunar activity from recent gas release". Nature. 444 (7116): 184–186. Bibcode:2006Natur.444..184S. doi:10.1038/nature05303. PMID 17093445.
  26. Tony Phillips (November 30, 2001). "Explosions on the Moon".
  27. Cudnik, Brian M.; Palmer, David W.; Palmer, David M.; Cook, Anthony; Venable, Roger; Gural, Peter S. (2003). "The Observation and Characterization of Lunar Meteoroid Impact Phenomena". Earth, Moon, and Planets. 93 (2): 97–106. Bibcode:2003EM&P...93...97C. doi:10.1023/B:MOON.0000034498.32831.3c.
  28. 1 2 "Lunar impact monitoring". NASA.
  29. "Bright Explosion on the Moon". NASA. May 17, 2013.
  30. "2005-06 Impact Candidates". rates and sizes of large meteoroids striking the lunar surface. Marshall Space Flight Center. 5 September 2008. Retrieved 2009-12-25.
  31. "SMART-1 impact flash and dust cloud seen by the Canada-France-Hawaii Telescope". 2006.
  32. Richard Zito, R (1989). "A new mechanism for lunar transient phenomena". Icarus. 82 (2): 419–422. Bibcode:1989Icar...82..419Z. doi:10.1016/0019-1035(89)90048-1.
  33. David Hughes, David W. (1980). "Transient lunar phenomena". Nature. 285 (5765): 438. Bibcode:1980Natur.285..438H. doi:10.1038/285438a0.
  34. Trudy Bell & Tony Phillips (December 7, 2005). "New Research into Mysterious Moon Storms".
  35. B. Buratti, B; W. McConnochie; S. Calkins & J. Hillier (2000). "Lunar transient phenomena: What do the Clementine images reveal?". Icarus. 146: 98–117. Bibcode:2000Icar..146...98B. doi:10.1006/icar.2000.6373.

General references

  • William Sheehan & Thomas Dobbins (2001). Epic Moon: A History of Lunar Exploration in the Age of the Telescope. Willmann-Bell. p. 363. ISBN 0-943396-70-0. 
  • Patrick Moore, On the Moon, Cassel & Co., 2001, ISBN 0-304-35469-4.

External links

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