[meteorite-list] Leonids Cause Visible Lunar Explosions

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:55:42 2004
Message-ID: <200201071647.IAA18214_at_zagami.jpl.nasa.gov>

http://www.popularmechanics.com/science/space/2002/1/lunar_explosions/

Meteors Cause Visible Lunar Explosions
BY STEFANO COLEDAN
Popular Mechanics
January 5, 2002

Hundreds of shooting stars an hour, smoky trails in
the sky, huge flashes, and even sonic booms--these
can be the effects of a meteor storm. And it gets
even more exciting. During the Leonids meteor shower
of November 2001 some alert stargazers observed and
documented on video a dazzling flash coming from the
moon's dark side.

David Palmer, an astrophysicist at Los Alamos
National Laboratory, recorded the explosion from his
backyard in White Rock, N.M., using a portable
telescope and a low-light video camera. Even though
it was twilight, the flash was bright enough to be
detected, Palmer says.

Leonid meteor showers are produced when particles
from the tail of the comet Tempel-Tuttle encounter
the Earth's atmosphere at a speed of more than
60,000 mph. That causes the tiny grains of cometary
dust to vaporize instantly, creating the sudden
flashes we see from the ground.

Unlike Earth, however, the moon doesn't have a
protective atmosphere in which meteoroids harmlessly
disintegrate, says NASA's Bill Cooke. In fact, when
kilogram-size Leonids hit the lunar surface, they
explode in spectacular fashion, digging craters and
melting the terrain with temperatures reaching up to
200,000° F.

Throughout the 1970s, Apollo seismic stations
recorded impacts from Leonids and other annual
meteor showers. But it's only since 1999 that
explosions on the moon have been seen from Earth,
Cooke says. In fact, at least six Leonids hit the
moon in 1999, causing explosions visible from Earth.

The lack of any detectable atmosphere would deprive
future lunar settlers of both protection and the
fiery shows we enjoy on Earth. For an astronaut, the
probability of being hit by a 10- to 5-gram Leonid
while on the moon is only 0.00025:1, says Cooke.
Nevertheless, such meteoroids have enough energy to
pierce a spacesuit and severely injure a person.
"The probability of being hit by something that
might totally vaporize you, like a 10-kilogram
fragment, is a billion times less," says Cooke.
Received on Mon 07 Jan 2002 11:47:27 AM PST