A mysterious flash on the Moon registered half a century ago still agitates the minds of scientists. If the flash was the result of falling of a large asteroid, it means that such collisions with the Moon and the Earth may happen oftener than was earlier supposed.
In 1953, astronomer Leon Stuart took a picture of the Moon with a bright spot in the center of its visible surface. The brightness of the flash corresponded to the energy liberation equivalent to an explosion of about 500 kilotons.
Astronomer Bonnie Buratti from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena says that the newly obtained data allow to suppose that the flash on the Moon could be the result of falling of an asteroid of about 20 meters in diameter. If she is right, it may mean that collision of asteroids with the Moon (and with the Earth) may happen oftener: approximately once in 500 years with the Moon, and once in 30 years with the Earth.
The crater formed after falling of the hypothetical asteroid is too small to be discerned from the Earth. However, astronomer Buratti says that the pictures made from the Clementine automatic station on the circumlunar orbit in 1994 revealed a new crater which appeared as a result of impact. The new crater was exactly in the region where Leon Stuart discovered the flash 50 years ago. Ejection of a brighter substance cover the territory of 1.5 kilometers in diameter; and the color indicates that the crater is new enough.
Nevertheless, several scientists still insist that the picture presented by Stuart reveals not an asteroid falling on the Moon, but a so-called stationary meteor, a rather rare phenomenon: the meteor’s mechanical trajectory is directed along the eyesight axis of an observer, so that the observer can see only a flash in the sky.
Skeptics assume that the meteor on Stuart’s picture just accidentally projected on the picture of the Moon disk in the background. Despite the fact that such stationary meteors are rarely observed, they still happen oftener than falling of large asteroids on the Moon. Besides, opponents of Bonnie Buratti say that existence of the “new” crater on the Moon is of slightest importance: there are no effective criteria to determine its actual age. It is likely that the “new” crater is 20 million years old and it is just a bit newer than others.
Bonnie Buratti rejects such doubts. She says that Stuart was a very experienced astronomer. His picture was taken with the exposure of half a second; there were no signs of camera movement; and the flash itself occurred in the Moon’s part along its orbit, where fallings of meteorites are highly possible. Bonnie Buratti says that discovery of the crater in the pictures taken from Clementine proves that the astronomer was right when 50 years ago he took a picture of the Moon at the moment when a new crater appeared on the planet.
CNews Translated by Maria Gousseva
Read the original in Russian: http://science.pravda.ru/science/2003/6/20/56/5577_Selena.html