[meteorite-list] Newspaper reporter doesn't learn definition of "meteor"

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Tue, 06 Jan 2009 18:50:50 -0500
Message-ID: <4gr7m4ha8e33los0vrbqbfiekghj9g69n6_at_4ax.com>


10 tonnes of flaming history
By Kevin Ma
Leader Staff
Four billion years doesn?t feel like much when you hold it in your hand.

It doesn?t look like much, either. It?s a coal-black lump of rock that?s just a
few centimetres in diameter. It?s feather-light, weighing about as much as a

But this rock is about 4.6 billion years old, says Murray Paulson, an amateur
astronomer in St. Albert. On Nov. 20 it came screaming out of the heavens at
about 50,400 kilometres an hour, part of a 10-tonne meteorite the size of an
office desk that lit up the Alberta sky as a blazing fireball.

Paulson was one of the many meteorite hunters who descended on Buzzard Coulee,
Sask. in the days after to find pieces of this rare stone.

"These are fossils of our solar system," Paulson emphasizes. "Every one of them
has a story to tell us."

Really tiny planets

Paulson, a physicist by training, says he first became hooked on meteors about
13 years ago, when he got a chance to hold one. "It was a neat thing to realize
that I was holding a piece of another planet," he says. "It was one of those
pivotal moments in your life when you realize, ?This is important.?"

He went on to start the small collection of meteors he now has on his desk.
There?s a black triangular chunk from the Bruderheim meteor of 1960, for
example, and a plastic case containing a small chip of Mars. Next to them are
the six fragments he found earlier this month - coal-like lumps ranging from
three to 50 grams in weight.

Researchers say meteors are chunks of rock dating back to the start of the solar
system about 4.6 billion years ago. Back then, as Paulson explains with
enthusiasm, the solar system was a soup of elements swirling around in a disk.
Over time, some of these elements came together to form bigger clumps called
planetesimals. Some of those lumps formed planets; others became part of what is
now known as the asteroid belt. When bits of these bodies break off through
collisions and streak into the Earth?s atmosphere, they are called meteors.

Meteors have a few features that set them apart from other rocks, Paulson
explains. They have a thin black fusion crust on the outside, caused by the
fiery heat of their descent, but are grey on the inside. They also tend to be
magnetic, he adds, sticking one to a circular magnet.

Look closely, Paulson says, and you will see that these meteors contain many
tiny spheres. These spheres are called chondrules, bits of dust that ran into
hot portions of that ancient solar soup and melted into drops of hot lava. Their
presence in these stones means the Nov. 20 meteor is classified as a chondrite
(named after the Greek word for seed, chondros).

The meteor that these fragments came from probably swung around the solar system
for millions of years before it blundered into Earth?s orbit last month, Paulson
says. Researchers are still calculating its original orbit. "Then it came
screaming in about half an hour before suppertime."

10 tonnes of fiery boom

Alan Hildebrand, professor of planetary science at the University of Calgary, is
the lead scientist in the Nov. 20 meteor recovery effort. He met Paulson and
many other meteor fans during their hunt for the stones earlier this month.

At precisely 5:26:40 p.m. on Nov. 20, he says, hundreds of Alberta and
Saskatchewan residents reported seeing a ball of blue-white fire zip across the
sky. Night briefly flared into day as the fireball thundered overhead, passing
from afternoon-bright to evening orange over the course of five seconds before
it disappeared.

This fireball was caused when a meteor hit the Earth?s atmosphere at about 14
kilometres a second ? a bit below the typical meteor speed of 20, Hildebrand
says ? at a 60-degree angle. Intense heat from friction with the air melted the
surface of the rock and created a fusion crust, a bright light and a sonic boom.
"It?s a temperature similar to the surface of the sun," he says. "Basically, we
[were] looking at white-hot air."

The meteor broke up in a series of bright explosions, the low-frequency sounds
from which were picked up by infrasound detectors from Greenland to Utah. Data
from those sensors, originally designed to detect nuclear missile launches,
suggest the rock had a mass of 10 tonnes and exploded with the force of about
300 tonnes of TNT. The fact that the rock didn?t stop breaking up until it was
about 12 kilometres above the ground suggests it was originally pretty big,
Hildebrand says ? about the size of an office desk, he estimates.

After breaking up, the rock kept falling to earth, scattering debris over a
large area. The meteor fragments would have hit the earth at a mere 180 to 360
km/h, Hildebrand says. One 13-kilogram chunk of the meteor was later found eight
inches deep in the frozen earth. Anyone standing near the impact site might have
heard a whistling sound like a golf ball as the meteors whizzed past.

The search

Hildebrand and graduate student Ellen Milley found the meteor?s debris field on
Nov. 27. Finding it was a matter of triangulation, he says. Extensive footage of
the fireball indicated that it had first appeared about 80 kilometres above and
east of Lloydminster and headed southeast towards the Battle River. Interviews
on the ground narrowed the search area to a 20 square kilometre zone near
Buzzard Coulee, southeast of the hamlet of Lone Rock, Sask.

Eventually, Hildebrand took a ride past a pond on a farm owned by Ian Mitchell.
"Ellen spotted some dark things on the pond." They got out of their car to
investigate and, after two false positives (a leaf and a rock), found the first
250 gram chunk of the meteor embedded in the ice.

Paulson says he missed the fireball by about three minutes, but soon joined the
search to find where the meteor landed. "These are the kind of chances that only
come along a few times in your life."

He and several other local astronomers reached the site on a clear, cold Nov. 29
and started their search on the Battle River. "The surface of the ice was
polished like a hockey rink," he recalls. "It was just beautiful." Several other
meteor hunters passed them on skates. Paulson and his crew scanned the ice for
suspicious black objects, testing each with magnets mounted on sticks.

After hours of searching, Paulson spotted a possible candidate buried in the
ice. He chiseled it out with a hammer and tested it with a magnet. It stuck.

"When it stuck to my magnet, that was it ? I was in seventh heaven," Paulson
says. "I?d never found a meteor before in my life and it was so cool to actually
see it among all the other things on the ground."

Paulson found about 20 other meteorites over the next few days and kept six. He
says he?s particularly proud of one he dubbed a "road-kill" meteor, because he
found it split in two on one of the area?s roads. "Somebody went a little bit
ahead of us and found a seven-kilogram piece of meteorite," he says. "Sigh."

The meteor hunt has stopped now that the snow has come, Hildebrand says. He and
other researchers will now study the meteorites to determine their contents.
Preserved dust in the rocks might offer clues on the early structure of the
solar system.

Paulson says he plans to study his meteors and show them to his friends. "Very
few of us will ever get to leave Earth and go to the moon or places like that,"
he says. "This is one of the few opportunities you have in your life of touching
another planet."
Received on Tue 06 Jan 2009 06:50:50 PM PST

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