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鈥檚 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鈥檚 surface. But astronomers have never
been able to confirm the sightings. 鈥淭he events were observed on many occasions,
but most astronomers don鈥檛 believe in them,鈥� says Bonnie Buratti of NASA鈥檚 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鈥檚
Clementine satellite was mapping the lunar surface.
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Intrigued by the amateur reports, Buratti鈥檚 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. 鈥淎fter the event, it looks redder,鈥� 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. 鈥淚鈥檓 pretty sure that some of
these changes are due to emanations of gas that are more dense than usual,鈥� says
Cameron. 鈥淭he Aristarchus region is the source of about a third of all of
迟丑别蝉别.鈥�