Transient Lunar Phenomena

Transient Lunar Phenomena make many astronomers wonder if the moon is not so inert as was once thought.

In our present phase of post-Apollo enlightenment, it would be wrong to suggest that all the mysteries of the moon have been solved. Curious things, seen now and then—faint glows, flashing lights, patches of "mist"—still provoke argument and continue to enlist scientific inquiry and speculation.

Men have been to the moon, brought back samples of rocks, monitored the recording devices left behind; Absolutely no trace of life has been found. We are confident the moon has always been biologically sterile. We had expected a total lack of atmosphere on the moon, but were disappointed to detect no "watery" material in the rocks. Lunar surface eruptions of volcanic proportion, possible sources of the moon's craters, would have to be consigned to ancient history. The moon looks much the same today as it did when the first telescopic observations were made of it in 1609. Even so, and however quiet, many astronomers readily concede that the moon is not so inert as was once thought. In fact, can we be sure that nothing ever happens there?

Bright Lights on the Moon

Historically, bright lights have been described on several occasions. Sir William Herschel, in 1787, saw several points he believed to be active volcanoes. Modern observers have described faint glows, sometimes red, which are now generally known as TLP—Transient Lunar Phenomena.

Many who study the moon with powerful telescopes have reported these elusive glows or local obscurations. The procedure requires many hundreds of hours of fruitless searching before even a glimmer can be spotted. Following the War, most TLP reports came from amateurs but this was understandable enough. Professional astronomers were not then particularly interested in the moon; It was regarded as somewhat dull and parochial. Far more important were the stars and distant star-systems (no doubt true enough). When the Space Age drew near, however, opinions changed, and the moon, in its accessibility, once more became newsworthy.

At the Crimean Observatory in the U.S.S.R., Nikolai Kozyrev was using the 50" telescope to observe the moon. He was interested in the TLP reports. Once he was looking at the large formation Alphonsus, which is an enclosure over 110 kilometers in diameter, with a central mountain and a system of cracks or "rills" on its floor. Suddenly, Kozyrev saw a red patch not far from the central peak. It did not last for long, but he was able to obtain definite proof that something had happened. It was not the first time strange phenomena have been seen in Alphonsus. Even more interesting is Aristarchus, a 36-kilometer crater—the brightest object on the moon—which can even be seen when illuminated only by light reflected from the earth. Reddish glows have been seen here too, and the reports are too numerous to dismiss easily.

These odd lights are not confined to Alphonsus and Aristarchus. They appear elsewhere on the lunar surface, and most astronomers (though not all) are now convinced that the color spots are genuine. They are not always red. Some merely take the form of blurred patches, temporarily hiding the surface features beneath. Observers found that the lights were most common when the moon was closest to the earth (perigee), so that its crust was under maximum strain from earth's gravity.

Lunar Recordings

In 1969, the first manned landings left recording equipment behind on the lunar surface. It was found that mild moonquakes do occur most frequently at the time of perigee, which may indicate a link between moonquakes and the transient phenomena.

Still, what then causes the lights? We can certainly rule out conventional volcanic eruptions. Violent cataclysms on the moon ended at least a thousand million years ago, when life on earth was still at a primitive stage. But there have been suggestions that such glows are due to the escape of trapped gases from beneath the lunar crust, an entirely credible theory.

Meantime, observers—both professional and amateur-are continuing to keep a close watch, searching for the strange, will-o-the-wisp lights that appear so timidly from the density of lunar rocks. The moon has yielded up some of its secrets, but by no means all.  

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Transient Lunar Phenomena