[meteorite-list] Meteor Dust Could Affect Climate, Study Suggests

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Aug 25 12:50:46 2005
Message-ID: <200508251649.j7PGngl06590_at_zagami.jpl.nasa.gov>

http://www.spacedaily.com/2005/050824171838.q06h7fw0.html

Meteor dust could affect climate, study suggests
AFP
August 24, 2005

PARIS (AFP) - A space boulder that disintegrated in a fiery descent
over Antarctica last year has sparked a theory that meteor dust may
play a hidden role in our climate system.

The rock, estimated at 1,000 tonnes, entered the upper atmosphere above
Antarctica last September 3, becoming a fireball spotted by the infrared
eyes of US defence satellites, a study published on Thursday says.

Friction with air molecules stripped away the rock, transforming it into
a cloud of dust that trailed from 56 to 18 kilometers (35 to 11 miles)
in altitude. The rock was consumed in the plunge.

Closer inspection of the lingering cloud, using instruments at an
Antarctic ground station, suggests its particles were as large as 20
micronsmillionths of a metre) -- around a thousand times bigger than
previous estimates for the size of meteor debris.

The finding is significant, because large quantities of dust are dumped
in Earth's atmosphere from tiny pieces of asteroid rubble or debris left
by passing comets, although no-one knows for sure how much is deposited.

Previous research has already shown that particles which are larger than
one micron, spewed out by volcanoes, can play a crucial role in
affecting weather.

Their relatively large size helps them to reflect the Sun's rays, thus
creating a local cooling effect, and also provides a nucleus for
attracting atmospheric moisture -- they encourage clouds to form.

In addition, large particles tend to linger longest in the atmosphere,
sometimes taking months to reach the planet's surface.

Space dust is mostly deposited by rubble that is consumed in the fiery
descent. To the human eye, the event is visible as a reddish-golden
streak, a meteor, that may also leave a smoke-like trail.

Larger objects may partly survive the collision with the atmosphere.
Their remains -- called meteorites -- can amount for between one and 25
percent of the original rock, as the rest of the mineral is ablated away
by atmospheric friction.

Very big rocks, mercifully rare, can explode with catastrophic force if
they collide with Earth. The long reign of the dinosaurs is believed to
have been ended by a large asteroid or comet that smacked into the globe
some 65 million years ago in modern-day Mexico.

The study, published in the British science journal Nature, was led by
Andrew Klekociuk of the Australian Antarctic Division, based in
Kingston, Tasmania.
Received on Thu 25 Aug 2005 12:49:42 PM PDT