Post by Chicago Astronomer - Astro Joe on Dec 2, 2006 15:49:15 GMT -6
Lunar Leonid Strikes
Dec. 1, 2006: Meteoroids are smashing into the Moon a lot more often than anyone expected.
see captionThat's the tentative conclusion of Bill Cooke, head of NASA's Meteoroid Environment Office, after his team observed two Leonids hitting the Moon on Nov. 17, 2006. "We've now seen 11 and possibly 12 lunar impacts since we started monitoring the Moon one year ago," says Cooke. "That's about four times more hits than our computer models predicted."
Last month, Earth passed through a "minefield" of debris from Comet 55P/Tempel-Tuttle. This happens every year in mid-November and results in the annual Leonid meteor shower. From Nov. 17th to Nov. 19th both Earth and the Moon were peppered with meteoroids.
During the passage through Tempel-Tuttle's debris field, Cooke's team trained their telescopes (two 14-inch reflectors located at the Marshall Space Flight Center) on the dark surface of the Moon. On Nov. 17th, after less than four hours of watching, they video-recorded two impacts: a 9th magnitude flash in Oceanus Procellarum (the Ocean of Storms) and a brighter 8th magnitude flash in the lunar highlands near crater Gauss.
"The flashes we saw were caused by Leonid meteoroids 2 to 3 inches (5 to 8 cm) in diameter," says Cooke. "They hit with energies between 0.3 and 0.6 Giga-Joules." In plain language, that's 150 to 300 pounds of TNT.
For comparison, the ESA's SMART-1 probe crashed into the Moon on Sept. 2nd, delivering 0.6 Giga-Joules of energy to the lunar surface—the same as the brighter of the two Leonids.
"Leonid impacts are as energetic as the crash of a 700-lb spacecraft!" says Cooke.
Next up: The Geminid meteor shower on December 13th-14th. Once again Earth and Moon will be peppered with meteoroids—this time from the asteroid 3200 Phaethon. Says Cooke, "we'll be watching."
Source: science.nasa.gov/headlines/y2006/01dec_lunarleonid.htm
=============
There have been many reports of astronomers seeing impacts on the Moon thruout the centuries, but the astronomical community thought them as daft and nuts.
Seems that they are now vindicated.
