In January, 2000, a seven meter, 200 metric ton rock from space streaked across the skies of western Canada. The meteor was at least as bright as the Sun before it exploded over the Yukon Territory. Scientists have recovered fragments of the carbon-rich rock, which researchers say is the most valuable meteorite find in at least 30 years.
University Of Calgary Press Release
May 31, 2000
Largest meteorite find in Canadian history
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.
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)
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
The Canadian Meteorite Catalogue
Space Science News for March 16, 2000
NASA Headquarters, Washington, DC
Johnson Space Center, Houston, TX
Natural Resources Canada, Ottawa, ON
March 16, 2000
The very primitive composition and pristine condition of the 4.5-billion-year-old meteorite "offers us a snapshot of the original composition of the entire solar system before the planets formed," said Dr. Michael Zolensky, a cosmic mineralogist at NASA's Johnson Space Center (JSC) in Houston. "It tells us what the initial materials were like that went into making up the Earth, the Moon and the Sun." The age of the solar system is about 4.5 billion years.
"These meteorite fragments are of immense scientific value and interest," said Dr. Richard Herd, Curator of National Collections for the Geological Survey of Canada. "This rare find potentially will contribute to a better understanding of the nature of the universe." He added that finding previously undetected compounds in the fragments will have implications for both planetary and biological sciences worldwide.
The scientists described the fragments -- lumps of crumbly rock with scorched, pitted surfaces -- as resembling partly used charcoal briquettes: black, porous, fairly light and still smelling of sulfur.
Several factors combined to make this meteorite a cosmic bonanza for scientists. First, it is a carbonaceous chondrite, a rare type of meteorite that contains many forms of carbon and organics, basic building blocks of life. Carbonaceous chondrites, which comprise only about 2 percent of meteorites known to have fallen to Earth, are typically difficult to recover because they easily break down during entry into Earth's atmosphere and during weathering on the ground.
Zolensky said the last time a carbonaceous chondrite like this fell to Earth and was recovered was 31 years ago. "This is probably the only time in my career this will happen," he said.
The location and timing of the fireball also contributed to the scientific value of the samples. The fragments are part of a meteor that blew apart over a remote area of the Yukon Territory the morning of Jan. 18, 2000. The resulting sonic booms startled residents as far away as British Columbia and Alaska. The frozen, snow-covered ground of the remote Yukon provided near-ideal conditions for preservation, Herd said.
The finder, a local resident who has requested anonymity, collected the fragments in clean plastic bags and kept them continuously frozen. These are the only freshly fallen meteorite fragments recovered and transferred to a laboratory without thawing. Keeping the fragments continuously frozen minimized the potential loss of organics and other volatile compounds in the fragments.
About 2 pounds of meteorite fragments have been recovered so far. Of those, Zolensky has about a pound of fragments provided by the Canadian government and the University of Calgary. The finder loaned them to the university and to the National Meteorite Collection of the Geological Survey of Canada, Natural Resources Canada (NRCan) in Ottawa, which provided the still-frozen samples to JSC for study and analysis. NASA is working closely with NRCan scientists and is providing results of the analysis to them. "We are very sensitive to the fact that these are Canadian meteorites," Zolensky said. Any future studies will be done in cooperation with scientists worldwide.
Scientific analysis of the fragments has just begun. Tests have been limited to two non-destructive activities: making a thin section to analyze the mineralogy of the fragments, and measuring induced radioactivity. Tests for induced radioactivity, which are being carried out by Dr. David Lindstrom of JSC, measure the object's exposure to space radiation. This can be used to determine the size of the original meteoroid in space, estimates of which range up to 50 feet in diameter, with a mass of more than 55 tons.
The next step in the study of the fragments will be baseline analyses of the organics in the meteorite. This would require the destruction of some samples, and negotiations are under way with the finder for permission to do such tests.
"The nice thing about having a sample like this is that you don't really know what you're going to find or where it's going to lead," Zolensky said. "You can tuck samples away for the future when new questions come along that people can't even think up now."
February 25, 2000
Debris from a fireball that exploded over Carcross, Yukon Territory, last month has been found on a snow-covered lake along the Klondike Highway. A meteorite fragment weighing about 6 ounces was sent to the Johnson Space Center near Houston for analysis.
The fragment, believed to be at least 4.5 billion years old, was found by an area resident who requested anonymity and no media coverage, according to Canadian officials. The Canadian and U.S. governments, for now, are honoring the request, so few details are available.
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