Lights glow on Moon

Light site: The mighty crater Langrenus, 136 km across

By BBC News Online science editor Dr David Whitehouse

New evidence shows that the Moon is not a totally dead world as was thought by many astronomers. It does still occasionally stir with activity.

Even though they have been reported from time to time for hundreds of years, claims of changes on the lunar surface have always been controversial. Many scientists have dismissed the occasional reported sightings of glows and mists hanging over certain lunar features.

Now a French astronomer has obtained some of the best evidence yet that occasionally something does disturb the lunar surface.

It was seen in 1992 by veteran lunar observer Audouin Dollfus of the Observatoire de Paris using the one metre (39 inch) Meudon reflecting telescope. He has only just finished analysing the results, and has submitted them for publication.

Fading light

On 30 December, he noticed a series of glows on the floor of the large crater Langrenus. They were definitely not there the day before. Professor Dollfus observed them for several days before they faded.

Clouds of light were seen dancing inside the crater

Each time he returned to the telescope, he noticed that the shape of the glows had changed.

He believes that the glows are due to escaping gas that lifts dust above the lunar surface into sunlight.

Some lunar observers have expressed surprise that such a mist should have been seen above Langrenus which was not regarded as a prime candidate for lunar changes.

Professor Dolfuss points out that Langrenus, when observed in detail, has an extensive series of fractures on its crater floor and the gas could be escaping from these.

Man on the Moon

So-called "Transient Lunar Phenonemon" (TLP) have been reported from time to time but definite evidence has been lacking.

Professor Dollfus observes the Moon

Responding to observations from the ground, Neil Armstrong was asked to look for glows on the Moon during the Moon landing in July 1969. He reported seeing a part of the Moon glow, but later could not be sure which region it was.

In 1994, the Clementine lunar orbiting satellite observed the crater Aristarchus before and after a TLP was seen from the Earth.

Clementine spectral data suggested that parts of the crater had changed colour slightly.