[meteorite-list] Lunar Geminids

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 4 Jan 2007 09:14:01 -0800 (PST)
Message-ID: <200701041714.JAA13600_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/headlines/y2007/03jan_lunargeminids.htm

Lunar Geminids
NASA Science News
January 3, 2007

January 3, 2007: Another meteor shower, another bunch of lunar impacts...

"On Dec. 14, 2006, we observed at least five Geminid meteors hitting the
Moon," reports Bill Cooke of NASA's Meteoroid Environment Office in
Huntsville, AL. Each impact caused an explosion ranging in power from 50
to 125 lbs of TNT and a flash of light as bright as a 7th-to-9th
magnitude star.

The explosions occurred while Earth and Moon were passing through a
cloud of debris following near-Earth asteroid 3200 Phaethon. This
happens every year in mid-December and gives rise to the annual Geminid
meteor shower: Streaks of light fly across the sky as rocky chips of
Phaethon hit Earth's atmosphere. It's a beautiful display.

The same chips hit the Moon, of course, but on the Moon there is no
atmosphere to intercept them. Instead, they hit the ground. "We saw
about one explosion per hour," says Cooke.

How does a meteoroid explode? "This isn't the kind of explosion we
experience on Earth," explains Cooke. The Moon has no oxygen to support
fire or combustion, but in this case no oxygen is required: Geminid
meteoroids hit the ground traveling 35 km/s (78,000 mph). "At that
speed, even a pebble can blast a crater several feet wide," says Cooke.
"The flash of light comes from rocks and soil made so hot by impact that
they suddenly glow."

Cooke's group has been monitoring the Moon's nightside (the best place
to see flashes of light) since late 2005 and so far they've recorded 19
hits: five or six Geminids, three Leonids, one Taurid and a dozen random
meteoroids (sporadics). "The amazing thing is," says Cooke, "we've done
it using a pair of ordinary backyard telescopes, 14-inch, and
off-the-shelf CCD cameras. Amateur astronomers could be recording these
explosions, too."

Indeed, he hopes they will. The NASA team can't observe 24-7. Daylight,
bad weather, equipment malfunctions, vacations - "lots of things get in
the way of maximum observing." Amateur astronomers could fill in the
gaps. A worldwide network of amateurs, watching the Moon whenever
possible, "would increase the number of explosions we catch," he says.

To that end, Cooke plans to release data reduction software developed
specifically for amateur and professional astronomers wishing to do this
type of work. (The release will be announced on Science at NASA in the near
future.) The software runs on an ordinary PC equipped with a digital
video card. "If you have caught a lunar meteor on tape, this program can
find it. It eliminates the need to stare at hours of black and white
video, looking for split-second flashes."

More data will help NASA assess the meteoroid threat as the agency
prepares to send astronauts back to the Moon. Ready to assist? Stay
tuned to Science at NASA for further instructions.
Received on Thu 04 Jan 2007 12:14:01 PM PST