Whatever happened to Transient Lunar Phenomena?

There are said to be many unexplained occurrences and phenomenon in the Universe but us science-minded folk like to think we have solved most of those mysterious and unusual events here on Earth. Yet we humans are still baffled by many things, from the whys and hows, humans always search for a plausible and sometimes implausible answer to what plagues our curious minds. This is no different when it comes to deeper into space and it has been curiosity that has been expanding our ever growing knowledge of the extraterrestrial realm. But sometimes you can hit a very stubborn (metaphorical) brick wall and we can be left completely stumped by the strangeness of an event or occurrence and this definitely true of the very baffling Transient Lunar Phenomenon (TLP).

Image of the Moon with sites of TLP events marked.

You may initially think this is something that only an astrophysicist could describe but put in simpler terms, TLPòÀÙs are the short-lived changes in brightness in areas on the surface of the moon, appearing as quick bright flashes, with some lasting seconds and some lasting for hours! These changes can also be of changing colours such as flashes of red or violet and some have even been recorded as òÀØdarkeningòÀÙs.òÀÙ These occurrences also have sometimes been describe as a haze rather than flash of light so it appears any occurrence of light on or near the Moon’s surface whose origin is not know is referred to as a TLP. These occurrences are usually spotted by lone observers and mostly in the past by amateur astronomers but there have been studies on it to try and discover what they could actually be. It seems that with the first telescopes came the more regular reports of TLPòÀÙs including sightings recorded by the famous astronomer William Herschel.ˆà In April 1787 he reported that he had spotted three red glowing spots on the dark side of the moon. Herschel was so determined that he seen these that he even had King George III come to try and see them through his telescope.

From then there have been a vast number of recorded sightings by lone amateur and professional astronomers. The first serious attempt made by a professional body to catalogue sightings was by NASA before the Apollo 11 mission. They catalogued 579 lunar events from 1540 until 1967, one year before Neil Armstrong and Buzz Aldrin put their feet on its surface. NASA did not necessarily give much exposure to the concept of random unidentified , potentially hazardous flashes appearing on the moon before the Apollo missions for fear of the Apollo programme being cancelled due to the unexplained TLPs but they still where interested in finding out more about them, just in a more secretive and hushed manner.

In the early days of the Apollo programme NASA commissioned a research project into TLPòÀÙs but avoided the use of the term. Instead they called this endeavour Project Moon-Blink,ˆà its goal was to try to discover more about òÀØunusual colour occurrencesòÀÙ on the Moon and if they really occurred.ˆà Within their findings they confirmed the occurrences of red colourations on the moon surfaces some occurring for several hours. An example of this being the Trident sighting on 15 Novemberˆà 1965 where the coloration was observed for a few hours and may have lasted longer but the sunrise cut observations short.

The astronauts in the Apollo programme would have been informed of the existence of TLPòÀÙs andˆà they observed certain occurrences of their own. This included the first mission to make it to the Moon and land there, Apollo 11 in 1969. Whilst circling the moon Houston radioed Apollo informing them of an observation of a TLP that astronomers in Germany had observed in the region of Aristarchus on the Moon. The Apollo crew checked it for themselves and reported back stating;

òÀÜHey, Houston, IòÀÙm looking north up toward Aristarchus now, and thereòÀÙs an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence.òÀÝ NASA, Apollo 11 Transcripts

An interesting fact that was discovered when all the 579 official TLPs were recorded was that a third of these were observed in the vicinity of Aristarchus crater on the north-west part of the Moon’s near side. The feature itself is already quite a prominent as it is already considered to be quite bright itself and easy to identify when it is highlighted by the occurrence of earthshine on the Moon. (This is when reflected sunlight from the Sun on the Earth lights up the dark portion of the Moon).

Apollo 15 photo of Aristarchus crater (the brighter of the two large craters near the top of the image). About 40 km across, Aristarchus is one of the brightest features in the Moon. Beside is Herodotus crater, closer to the camera (which was looking south) is the superb sinuous rille Vallis Schroteri. (Image credit: NASA)

So it seems TLPòÀÙs definitely do exist but what could they be and what are causing them? Many astronomers who have observed TLPòÀÙs have also threw their two cents in, offering possible mechanism for what could be causing them. Some believe that solar particles had a part to play in their occurrence, others supported the discarded theory that the Moon’s craters are old, inactive volcanoes with the TLP representing the last gasps of lunar vulcanism or possibly the TLP’s are gases bursting through the seams of craters. LetòÀÙs look at each of these theories that could maybe explain these odd occurrences on the Moon.

A largely accepted theory is that of òÀÙoutgassing.òÀÙ This is the idea that pockets of gas below the surface of the Moon are released to the surface through tidal stresses. The gas leaks through to the surface via cracks or cavities and cause a period of colour change in the surface of the Moon often described as a hazy colouring with a reddish hue. This could very well be the answer for the occurrences spotted around the vicinity at Aristarchus as when Apollo 15 passed over this area, the astronauts noted and recorded a very significant rise in alpha particles caused by the decay of Radon-222. This is a radioactive gas with a halflife of 3.8 days and is a decay product of uranium. This perhaps is what causes those red hazes that many have reported in the area.

Astronomer Leon Stuart’s photo of the Moon with mystery white speck taken on 15 November 1953 is still controversial. Is it a TLP, a meteor impact or a flaw on the original negative? Compare it to the next image.

Another very plausible theory, especially for those TLPòÀÙs that are quick, bright and short lived could very well be the occurrences of meteorites on the lunar surface. There is obviously no doubt that the Moon is obviously a victim at the hands of those high speed space rocks due to its pockmarked complexion. We have even observed meteorites impacting the Moon, notably in September 2013. It is very possible that a small meteorite has hit the surface of the moon causing a bright flash that would easily grab the attention of a lunar observer.

The impact of a large meteorite on the lunar surface on 11 September 2013, resulted in a bright flash, observed by scientists at the MIDAS observatory in Spain.ˆà
(Image credit: J. Madiedo / MIDAS)

Some have put forward the theory that some of these occurrences could be blamed on electrostatic phenomena. Like shuffling your feet across a carpet to charge you with static, the fracturing of near surface materials could perhaps charge gas and dust and their ultimate discharge could give way to the observations that we are seeing from the Earth. The charging of lunar particles could in turn result in the levitation of the particles, again perhaps adding to what we could be seeing from Earth.

Another very plausible reason could be the most simplest. Many dismiss the idea of TLPòÀÙs even being real and that those who have reported sightings have really just been duped by unfavourable observing conditions. by imperfections in their telescope or have been observing events in the EarthòÀÙs atmosphere. Some reported sightings, including that of HershelòÀÙs where made when the Northern Lights or Aurora Borealis was highly active. But that does seem highly improbable that all sightings have such uninteresting origins.

As the years have gone on and technology has become much more accurate and reliable there has been much less sightings and reports of TLPòÀÙs so the hype surrounding the phenomena in the 1970òÀÙs has somewhat dwindled away but there is still those who are very much interested in the oddity and are curious to pinpoint exactly what causes them. An interesting study into TLPòÀÙs by the British Astronomical Association published in March 2013 published findings suggesting that the TLPs were linked to the 11 year solar cycle of our Sun due to the increase of reported TLPs during the peak of the solar cycle. This theory had surfaced before in 1945 by H.Percy Wilkins but was later disproved by a study carried out by Barbara Middlehurst in 1966. No theory has been proved yet and there is no definite answer of how TLPs occur. With the effect of TLPs being so far irreproducible in a scientific experiment it may be some time before we can really pinpoint the cause of these strange events on the surface of the Moon.

(Article by Kerry Scullion, Education Support Officer)

Further reading

Middlehurst, Barbara M et al. Chronological Catalog Of Reported Lunar Events, NASA, 1968

Mobberley,Martin, It Came From Outer Space Wearing an RAF Blazer! Springer, 2014 (reveals Patrick Moore’s influence in the promotion of the TLP concept)

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