REPORTS of curious flashes and fleeting clouds on the Moon may not be figments of wild imaginations, astronomers say. A new look at observations by the American satellite Clementine show that a small area on the Moon's surface darkened and reddened in April 1994. Why this happened remains a mystery.
For hundreds of years, people have reported seeing flashes, short-lived clouds and other brief changes on the Moon's surface. But astronomers have never been able to confirm the sightings. "The events were observed on many occasions, but most astronomers don't believe in them," says Bonnie Buratti of NASA's Jet Propulsion Laboratory in Pasadena, California.
On 23 April 1994, around a hundred amateur astronomers reported seeing a possible darkening of the Moon, lasting 40 minutes, near the edge of the bright lunar crater Aristarchus. At the same time, the US Department of Defense's Clementine satellite was mapping the lunar surface.
Intrigued by the amateur reports, Buratti's team has taken a close look at the Clementine data to see if the satellite also recorded the event. Sure enough, they found that the crater looked different before and after the amateur reports. "After the event, it looks redder," says Buratti, who announced the findings at a meeting of the American Astronomical Society in Padua, Italy, last week.
Winifred Cameron, a retired astronomer who worked at the Lowell Observatory in Arizona, thinks that brief colour changes might be caused by small gas eruptions throwing dust around. We know that there are pockets of gas in the lunar soil, and the gas may occasionally escape. "I'm pretty sure that some of these changes are due to emanations of gas that are more dense than usual," says Cameron. "The Aristarchus region is the source of about a third of all of these."
Author: Charles Seife
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