[meteorite-list] low flying asteroid

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Tue, 25 Nov 2008 23:50:53 -0500
Message-ID: <57lpi41o4aoeh96krgfls3t7ruubcj32jp_at_4ax.com>

http://www.canada.com/vancouversun/news/story.html?id=dd5cc5ac-5fde-4a7b-827b-f2e14c5a1bab

10-tonne space rock lit up Prairie skies
Canwest News Service
Published: Tuesday, November 25, 2008

SASKATOON - A fireball that lit up the skies of Alberta and Saskatchewan last
Thursday evening was a chunk of low-flying asteroid that weighed about 10 tonnes
before it struck Earth's atmosphere, according to a University of Calgary
investigation.

University of Calgary researcher Alan Hildebrand has outlined a region in
western Saskatchewan where he expects to find desk-sized fragments of the space
rock.

According to the university, the fireball first appeared about 80 kilometres
above and just east of the city of Lloydminster, right on the
Alberta-Saskatchewan border.

It travelled southeast over Saskatchewan towards the Battle River valley before
it blew apart in a spectacular series of mid-air explosions.

The fireball pierced the atmosphere at a steep angle of about 60 degrees off the
horizontal and lasted about five seconds.

The fireball was recorded on all-sky and security cameras scattered across
Saskatchewan and Alberta and was witnessed by tens of thousands of people who
saw it streak across the sky.

Hildebrand said the fireball was like a billion-watt light bulb, turning night
into day with a bluish-white light. It illuminated the ground for several
hundred kilometres in all directions, shedding its intense light as far south as
Vauxhall, Alta., about 200 kilometres southeast of Calgary.

Hildebrand said the fragments most likely fell to earth in the Manitou Lake
Rural Municipality region, about 300 kilometres northwest of Saskatoon.

He urged residents to keep a sharp eye out for any of the dark, dense, usually
dimpled rocks scattered over the suspected meteorite field where chunks likely
came to rest.

He said as many as 1,000 meteorites may have landed in the field, which he's
narrowed down to a rectangle about eight kilometres long and three kilometres
wide.

"We're looking for more possible witnesses. We're going to alert the people in
that rectangle that they might have meteorites on their land," he said.

Hildebrand estimates hundreds of meteorites larger than 50 grams could have
landed, since the rock was large and it was moving relatively slowly when it
entered the atmosphere - 14 kilometres per second, instead of the average entry
speed of 20 kilometres per second.

The meteorites have "substantial commercial value" and are the property of the
landowner where they fall, Hildebrand said.

If the rocks are meteorites of common asteroids, they will be denser than the
average rock, dark grey or black with an unusual pockmarked exterior, and
usually will weakly attract a magnet, he said, noting other types of meteorites
are possible.

"We are now starting to reasonably constrain where the meteorites will have
fallen. Many witnesses reported seeing a cluster of red fragments continuing
downward in the sky after the fireball exploded. These represent the rocks
slowing down that will eventually fall to the ground as meteorites," Hildebrand
said.

"An outstanding thing about this fireball is that so many red fragments were
seen and that they travelled so low to the ground before becoming invisible in
the darkness."

Meanwhile, a University of Alberta researcher plans to use new laser technology
to help locate meteorite craters.

Dr. Chris Herd, a researcher at the department of Earth and Atmospheric
Sciences, says light detection and ranging (LiDAR) technology can clear trees
and other interference from aerial photographs to reveal hidden craters.

"You can just extract all the vegetation in a virtual sense, leaving the bare
surface behind, and that exposes the crater in beautiful detail for us," said
Herd.

Already used for forestry surveys, LiDAR employs a laser mounted in an aircraft
which is beamed at the ground. The technology allows researchers to strip off
the images of trees, leaving the crater exposed.

Because Thursday's meteor broke up into pieces and scattered over a large area,
it's unlikely it created an impact crater, Herd said.

Still, he has tips for those who may come across the remains.

"The best thing to do, for scientific reasons, is to not handle it directly with
hands, and to pick it up with a bag or even a piece of aluminum, store it in
that and go from there."
Received on Tue 25 Nov 2008 11:50:53 PM PST