[meteorite-list] Lunar Transient Phenomena

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 23 Jan 2007 13:15:46 -0800 (PST)
Message-ID: <200701232115.NAA14250_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/headlines/y2007/23jan_ltps.htm

Lunar Transient Phenomena
NASA Science News
January 23, 207

January 23, 2007: If you stare at the Moon long enough, you start seeing
things. "82 things to be exact," says Bill Cooke, leader of NASA's
Meteoroid Environment Group. That's how many "transient phenomena" the
group has video-taped since they started monitoring the night side of
the Moon in Nov. 2005.

"In 107 hours of observing, we've tallied 20 lunar meteors + at least 50
Earth-orbiting satellites + one airplane + one terrestrial meteor = 82 in
all."

This is the first systematic count of lunar night-side phenomena. "It
gives astronomers an idea of what to expect when they undertake a lunar
monitoring program from Earth."

(Note: The lunar night side shouldn't be confused with the lunar
farside. "We can never see the farside of the Moon," he says. "But we
often see the night side. It's any lunar terrain not lit up by the Sun,
like the dark half of a quarter Moon.")

Cooke's prime target is lunar meteors--flashes of light that occur when
meteoroids hit the Moon's surface: video
<http://science.nasa.gov/headlines/y2006/images/lunarsporadic/movie760.gif>.
"Of the 20 lunar meteors we've seen so far, about half come from
well-known meteor showers such as the Leonids and Geminids. The other
half are random meteoroids that take us completely by surprise." NASA is
preparing to send astronauts back to the Moon and the agency is
understandably interested in how often this happens.

"Everything else we've seen is just a coincidence, something flying in
front of the Moon while we happen to be watching." Leading this category
are Earth-orbiting satellites and pieces of space debris. This Orbcomm
A4 communications satellite is a typical example:

NORAD tracks more than 10,000 Earth-orbiting objects wider than 10 cm.
"Some of them are bound to cross in front of the Moon while we're
watching," he says. Objects like Orbcomm are easy to identify as
satellites. Tumbling space debris, on the other hand, can be trickier:
"A sudden glint of sunlight from a flat surface looks an awful lot like
a lunar meteor flash," he explains. "So we have to be very careful. When
we see a flash of light on the Moon, we always double-check that there
was no piece of space junk passing by at that exact moment."

Back in days of Apollo, astronomers who monitored the Moon didn't have
this problem. "There were very few satellites in Earth orbit, and a
lunar transit was rare," he says. "But now we see one or two every night."

Here's a mystery: "Can you identify this object
<http://science.nasa.gov/headlines/y2007/images/ltps/lunarairplane_23dec06.avi>?"
laughs Cooke. "Airplanes are my favorite."

So far, they have detected only one terrestrial meteor - that is, a
meteoroid disintegrating in Earth's atmosphere: video
<http://science.nasa.gov/headlines/y2007/images/ltps/meteor_13nov06.avi>.
This may seem puzzling. During a
typical meteor shower, novice sky watchers see dozens of shooting stars.
Why has NASA counted only one? "The telescope's field of view is too
narrow," explains Cooke. The human eye is much better for terrestrial
meteor watching.

He's more interested in the Moon, anyway. Exploding meteoroids, tumbling
satellites and jet airplanes: "It's a great show." What's next? "We plan
to keep watching, so stay tuned."
Received on Tue 23 Jan 2007 04:15:46 PM PST