Largest meteorite find in Canadian history

University Of Calgary Press Release

Dennis Urquhart

Research Communications

(403) 220-7722

Outdoorsman Jim Brook and scientists at The University of Western Ontario
(UWO) and the University of Calgary (U of C) have recovered the largest
meteorite fall in Canadian history. Analysis shows the meteorite is composed
of a very rare material, making it among the most scientifically significant
meteorite finds worldwide.

The meteorites fell on the morning of January 18, 2000 in a remote area
between Atlin, British Columbia and Carcross, Yukon Territory. A week later
on January 25th, a nearby resident, Jim Brook, found the first meteorite
fragments while driving homewards on the ice of Taku Arm in Tagish Lake.

Jim Brook describes his discovery, “I was watching closely for meteorites
and suspected their identity as soon as I saw them, although I had been
fooled several times by wolf droppings. It was obvious what they were as
soon as I picked one up, because rocks aren’t found on the ice, and I could
see the outer melted crust. I was very happy and excited.” Darkness soon
ended additional meteorite hunting that day, but Jim was back the next
morning, collecting several dozen of the space rocks.

Since that find, U of C and UWO researchers, working with the National
Aeronautics and Space Administration (NASA), have made several trips to the
area to collect samples of the very fragile meteorites and to map the fall
area. To date, 500 fragments have been found and hundreds have been
recovered from the site – many still encased in ice.

“This is the find of a lifetime,” says Peter Brown, meteor scientist in the
Department of Physics and Astronomy at The University of Western Ontario and
co-leader of the meteorite recovery investigation. “The size of the initial
object, the extreme rarity and organic richness of the meteorites combined
with the number we have uncovered make this a truly unique event.”

“Of all the times I dreamed of finding meteorites, I never thought
of finding them like this,” says Alan Hildebrand (left), planetary
scientist in the Department of Geology and Geophysics at the University of
Calgary and the other investigation co-leader. “One day while I was picking
pieces of meteorite out of porous ice I thought that the experience must be
a bit like sampling on the surface of a comet. We believe these to be the
most fragile meteorites ever recovered.”

Initial analysis by Michael Zolensky, a meteoriticist at NASA’s Johnson
Space Center showed the meteorites were a type of carbonaceous chondrite – a
rare, organically rich, charcoal-like class of meteorites. Zolensky says
that his work and that of colleagues “provides indications that the
meteorites are unique carbonaceous chondrites with hints of relation to the
CI chondrites.” Carbonaceous chondrite meteorites make up about three per
cent of meteorite finds. The possible chemical class of this fall
constitutes less than 0.1 per cent of all meteorites recovered to date, and
represents the most primordial samples known from the early solar system.
While the possibilities have researchers very excited, the meteorites’ true
significance remains to be fully understood. However, Jim Brook’s careful
collection of pristine meteorites from the icebox of a Canadian winter and
subsequent frozen storage has opened brand new doors for meteorite
researchers around the world.

The Nomenclature Committee of the Meteoritical Society has officially
designated the name Tagish Lake Meteorite for the fall specimens.

Using eyewitness and photographic data gathered during the field
investigations, and observations from two US Department of Defense satellite
systems, the trajectory and velocity of the fireball were determined. The
ability to calculate this is a relatively new development in meteorite
science – essentially allowing researchers to determine a meteorite’s
pre-fall size, orbit and origin in space.

“There have only been four previous meteorites for which accurate orbits are
known and no orbits for a carbonaceous chondrite have ever been secured,”
says Brown. “The entire process of recovery of the material and
determination of where it comes from makes this the scientific equivalent of
an actual sample-return space mission – at a thousandth of the cost.”

“The Tagish Lake fall is the largest ever recorded over land by the
satellite systems,” notes Hildebrand. “The recovery of hundreds of
meteorites allows studies which will precisely constrain the meteorite’s
size when it entered the Earth’s atmosphere. Calibrating the satellite
observations for such a large object will help us understand all the
fireballs that the satellites record around the globe, in effect creating a
global fireball camera system. These observations will increase our
knowledge of both the hazards and opportunities created by the
Earth-crossing asteroids and comets.”

In the same spirit with which hundreds of eyewitnesses described their
observations and donated photographs and videos to the investigation, and
the U.S. Department of Defense quickly supplied satellite data, the two
universities and Jim Brook have agreed to immediately make available some of
the rare meteorite to researchers. Forty grams of once water-soaked (but now
dried) meteorite fragments are now available on a proposal basis to
interested researchers. Work descriptions and sample requirements (to a
maximum length of one page) should be sent to hildebra@geo.ucalgary.ca for
consideration before June 30, 2000. Material for analysis will be provided
to all successful proposals within 30 days barring unanticipated
circumstances.

Media contacts:

Dennis Urquhart, University Communications, University of Calgary (403) 220-7722, cell: (403) 650-1153

Marcia Daniel, Communications and Public Affairs, The University of Western Ontario, (519) 661-2111 ext. 85165

—————————————————————————-

Backgrounder

January 18, 2000 – The fireball – A spectacular meteor crosses the Yukon
Territory into northern British Columbia at 08:43 PST. Eyewitnesses reported
a brilliant, multicolored fireball that lit up the countryside. Sizzling
sounds and peculiar smells that remain to be adequately explained
accompanied the fireball. Ground shaking detonations followed a few minutes
after the meteor’s passage when its sound arrived at the land surface. The
fireball and its explosions were so stunning that local residents were
concerned about the safety of their children and friends. The fireball was
also observed by satellites in Earth orbit, maintained by the U.S.
Department of Defense (D of D). These observations established an asteroid
weighing 200 tonnes and approximately five metres across had impacted the
Earth’s atmosphere. Data from D of D satellites were available within hours
of the event, the quickest any such data have been released after a bolide
event by the D of D.

January 19, 2000 – Airbourne sampling – From information gathered via email
and press reports, Peter Brown, meteor scientist at The University of
Western Ontario, discusses with Dr. Michael Zolensky of NASA’s Johnson Space
Center (JSC) the possibility of arranging an ER-2 aircraft sampling flight
over the area to attempt to recover small airborne particles. A series of
two flights is approved, but technical problems ground a first flight and
only one air photo/air sampling flight is performed on January 21, 2000.
Analysis of particles from this air-sampling mission are ongoing.

January 26, 2000 – Meteorites discovered – While Jim Brook was driving south
on the ice of Taku Arm, Tagish Lake, British Columbia, he noticed small dark
rocks on the ice. He suspected that these were meteorites from the fireball.
He carefully collected the rocks, covering his fingers with clean plastic
and placing the meteorites in plastic bags. Brook uncovered almost one
kilogram of this material during a total of only a few hours of searching on
the lake ice late on January 25 and early on January 26. Snow blankets the
area on January 27 ending recovery opportunities.

February 7, 2000 – Rare meteorite type confirmed – Zolensky receives two
samples from Brook with transportation arranged by the Geological Survey of
Canada. He confirms their suspected identification as carbonaceous
chondrites. Counting of short-lived cosmogenic nuclides begins immediately
at JSC.

February 16 – 28, 2000 – Fireball investigation and field search – An
initial field investigation is led by Brown and Hildebrand to the fall area.
Eyewitnesses of the fireball across the Yukon and northern B.C. are
interviewed, and video and photographic stills of the long-lasting dust
cloud left by the fireball are gathered. An initial path through the
atmosphere is calculated. The lake area and adjacent forest along Taku Arm,
Tagish Lake, where the initial meteorites were recovered is searched in an
effort to recover more pristine material. However, the heavy snow cover
proves insurmountable. The decision is made that, if more meteorites are
present, they probably can’t be found until the spring melt arrives.

April 6 – 15, 2000 – Second expedition – Additional fireball data are
gathered. From the information obtained during the first field investigation
a more accurate path has been derived for the fireball trajectory. With
velocity data from satellite observations, calculations were performed as to
where meteorites of various sizes would have fallen to narrow the potential
search area.

April 15 – 19, 2000 – Spring thaw accelerates – Searching of the fall area
begins again despite continued snow cover. Snow depths decrease during these
five days as temperatures increase. Searching bare spots on land yields no
meteorites.

April 20, 2000 – Meteorites found – The first meteorites are found and a
race against time begins. The Taku Arm lake ice would soon melt and ever
changing conditions complicated field work. In the first few days less than
10 meteorites were recovered per day. These meteorites were absorbing
sunlight and rapidly sinking through the meter-thick ice. The recovery team
wondered how much longer meteorites could be found and retrieved. Then
searching conditions improved and totals found soared, reaching a high of 94
meteorites in one day.

May 8, 2000 – Unsafe conditions and an exhausted team – The ice in the fall
region had become unsafe, and recovery efforts stop. Approximately 500
meteorites had been found on Taku Arm in a strewn field 16 kilometres long
and three kilometres wide. Thousands more fell on the ice and the
surrounding hills and mountains, but none have yet been found on land.
Approximately 200 meteorites were recovered totaling five to 10 kilograms in
mass, but most of this material remains frozen and a tonne of
meteorite-bearing ice is now in storage. A field effort consisting of 234
person field days is now over. This recovery effort is believed unique in
the history of meteoritics.

May 28, 2000 – Meteorites “drown” – Jim Brook reports that the ice of Taku
Arm is now gone.

Field Recovery Participants:

February 16 – 28, 2000:

Mr. Andrew Bird (U of C – Geology and Geophysics)

Mr. Jim Brook

Dr. Peter Brown (UWO – Physics and Astronomy)

Dr. Alan Hildebrand (U of C – Geology and Geophysics)

Mr. Mike Mazur (U of C – Geology and Geophysics)

Ms. Tina Mazur-Rubak (U of C – Educational Psychology)

April 6 – May 8, 2000:

Mr. Jim Brook

Dr. Peter Brown (UWO – Physics and Astronomy)

Ms. Margaret Campbell (UWO – Physics and Astronomy)

Mr. Robert Carpenter (UWO – Earth Sciences)

Mrs. Heather Gingerich (UWO – Earth Sciences)

Ms. Erika Greiner (UWO – Earth Sciences)

Mr. Mike Glatiotis (U of C – Geology and Geophysics)

Dr. Alan Hildebrand (U of C – Geology and Geophysics)

Mr. Philip McCausland (UWO – Earth Science)

Mr. Mike Mazur (U of C – Geology and Geophysics)

Dr. Howard Plotkin (UWO – Philosophy)

Ms. Doreen Stangel

Dr. Edward Tagliaferri (Aerospace Corporation – Los Angeles, CA)

Terminology

Carbonaceous Chondrites: A rare class of meteorites that have suffered
exposure to water on their original parent body surfaces in space. This
meteorite group is among the most primitive material in the solar system,
having generally escaped from high-temperature processing.

Carbonaceous chondrites are also unique in that they contain significant
carbon, primarily in the form of organic compounds similar to those found in
living organisms on Earth. Amino acids, for example, have been identified in
carbonaceous chondrites, including a large number which do not occur
naturally on Earth. These meteorites are metal-poor and water rich, in
contrast to almost all other meteorite classes.

Satellite Systems: The U.S. Department of Defense maintains two satellite
systems that can detect fireballs caused by asteroidal and cometary
fragments entering Earth’s atmosphere. One system consists of visible light
sensors which ‘stare’ continuously at the Earth; they have high temporal
resolution of transient flashes and measure the total energy released at
visible wavelengths. A second system of detectors is sensitive in the
infrared (IR) and scan across the visible face of the Earth at intervals;
the IR detectors can provide location and velocity information for
fireballs.

Map of Tagish Lake, B.C., and location of meteorites:

http://phobos.astro.uwo.ca/~pbrown/mets.jpg

The Canadian Meteorite Catalogue:

http://www.geo.ucalgary.ca/cdnmeteorites/