The Tagish Lake meteorite fell at 16:43 UTC on 18 January 2000 in the

Tagish Lake Tagish Lake is a lake in Yukon and northern British Columbia, Canada. The lake is more than long and about wide. It has two arms, the Taku Arm in the east which is very long and mostly in British Columbia and Windy Arm in the west, mostly in ...

area in northwestern British Columbia, Canada.

History

Fragments of the Tagish Lake

meteorite A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object en ...

landed upon the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface ...

on January 18, 2000, at 16:43 UT (08:43 local time in Yukon) after a large meteoroid exploded in the upper atmosphere at altitudes of with an estimated total energy release of about 1.7 kilotons of TNT. Following the reported sighting of a fireball in southern

Yukon Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...

and northern British Columbia, Canada, more than 500 fragments of the meteorite were collected from the lake's frozen surface. Post-event atmospheric photographs of the trail left by the associated fireball and U.S. Department of Defense satellite information yielded the meteor trajectory. Most of the stony,

carbonaceous Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up o ...

fragments landed on the Taku Arm of the lake, coming to rest on the lake's frozen surface. The passage of the fireball and the high-altitude explosion set off a wide array of

satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotop ...

sensors as well as

seismograph A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output ...

s. The local inhabitants described the smell in the air following the airburst as sulfurous and many first thought the blast was caused by a missile.

Meteoroid

The Tagish Lake meteoroid is estimated to have been 4 meters in diameter and 56

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton (United States c ...

s in weight before it entered the Earth's atmosphere. However, it is estimated that only 1.3 tonnes remained after

ablation Ablation ( la, ablatio – removal) is removal or destruction of something from an object by vaporization, chipping, erosive processes or by other means. Examples of ablative materials are described below, and include spacecraft material for a ...

in the upper atmosphere and several fragmentation events, meaning that around 97% of the meteorite had vaporised, mainly becoming stratospheric dust that was seen as

noctilucent clouds Noctilucent clouds, or night shining clouds, are tenuous cloud-like phenomena in the upper atmosphere of Earth. When viewed from space, they are called polar mesospheric clouds (PMCs), detectable as a diffuse scattering layer of water ice cryst ...

to the northwest of

Edmonton Edmonton ( ) is the capital city of the Canadian province of Alberta. Edmonton is situated on the North Saskatchewan River and is the centre of the Edmonton Metropolitan Region, which is surrounded by Alberta's central region. The city anchor ...

at sunset, some 12 hours after the event. Of the 1.3 tonnes of fragmented rock, somewhat over (about 1%) was found and collected.

Specimens

Tagish Lake is classified as a

carbonaceous chondrite Carbonaceous chondrites or C chondrites are a class of chondritic meteorites comprising at least 8 known groups and many ungrouped meteorites. They include some of the most primitive known meteorites. The C chondrites represent only a small prop ...

, type C2 ungrouped. The pieces of the Tagish Lake meteorite are dark grey to almost black in color with small light-colored inclusions, and a maximum size of ~2.3 kg. Except for a greyish fusion crust, the meteorites have the visual appearance of a charcoal

briquette A briquette (; also spelled briquet) is a compressed block of coal dust or other combustible biomass material (e.g. charcoal, sawdust, wood chips, peat, or paper) used for fuel and kindling to start a fire. The term derives from the French word ' ...

. The fragments were transported in their frozen state to research facilities after they were collected by a local resident in late January, 2000. Initial studies of these fresh fragments were done in collaboration with researchers from NASA. Snowfall covered the remaining fragments until April 2000, when a search effort was mounted by researchers from the University of Calgary and

University of Western Ontario The University of Western Ontario (UWO), also known as Western University or Western, is a public research university in London, Ontario, Canada. The main campus is located on of land, surrounded by residential neighbourhoods and the Thames Ri ...

. These later fragments were mostly found to have sunk into the ice by a few cm to more than 20 cm, and had to be collected out of meltwater holes, or cut in icy blocks from the frozen surface of Tagish Lake. Fragments of the fresh, "pristine" Tagish Lake meteorite totaling more than 850 g are currently held in the collections at the Royal Ontario Museum and the

University of Alberta The University of Alberta, also known as U of A or UAlberta, is a public research university located in Edmonton, Alberta, Canada. It was founded in 1908 by Alexander Cameron Rutherford,"A Gentleman of Strathcona – Alexander Cameron Rutherf ...

. "Degraded" fragments from the April–May 2000 search are curated mainly at the University of Calgary and the

Analysis and classification

Analyses have shown that Tagish Lake fragments are of a primitive type, containing unchanged stellar dust granules that may have been part of the cloud of material that created the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

and

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. This meteorite shows some similarities to the two most primitive carbonaceous chondrite types, the CI and CM chondrites; it is nevertheless quite distinct from either of them. Tagish Lake has a much lower density than any other type of chondrite and is actually composed of two somewhat different rock types. The major difference between the two lithologies is in the abundance of carbonate minerals; one is poor in carbonates and the other is rich in them. The meteorite contains an abundance of

organic material Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have c ...

s, including

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s. The organics in the meteorite may have originally formed in the interstellar medium and/or the solar protoplanetary disk, but were subsequently modified in the meteorites' asteroidal parent bodies. A portion of the carbon in the Tagish Lake meteorite is contained in what are called

nanodiamond Nanodiamonds, or diamond nanoparticles, are diamonds with a size below 100 nanometers. They can be produced by impact events such as an explosion or meteoritic impacts. Because of their inexpensive, large-scale synthesis, potential for surfac ...

s—very tiny diamond grains at most only a few micrometers in size. In fact, Tagish Lake contains more of the nanodiamonds than any other meteorite. As with many carbonaceous chondrites, and Type 2 specimens in particular, Tagish Lake contains

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

. The meteorite contains water-bearing

serpentinite Serpentinite is a rock composed predominantly of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake. Serpentinite has been called ''serpentine'' or ''serp ...

and

saponite Saponite is a trioctahedral mineral of the smectite group. Its chemical formula is . It is soluble in sulfuric acid. It was first described in 1840 by Svanberg. Varieties of saponite are griffithite, bowlingite and sobotkite. It is soft, m ...

phyllosilicates;

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...

has been found, but may be weathering of meteoritic sulfides. The water is not Earthly contamination but isotopically different from terrestrial water. The age of the meteorite is estimated to be about 4.55 billion years thus being a remainder of the period when the solar system was formed.

Origin

Based on eyewitness accounts of the fireball caused by the incoming meteor and on the calibrated photographs of the track which it had left behind and which was visible for about half an hour, scientists have managed to calculate the orbit it followed before it impacted with Earth. Although none of the photographs captured the fireball directly, the fireball path was reconstructed from two calibrated photos taken minutes after the event, giving the entry angle. Eyewitness accounts in the vicinity of

Whitehorse Whitehorse () is the capital of Yukon, and the largest city in Northern Canada. It was incorporated in 1950 and is located at kilometre 1426 (Historic Mile 918) on the Alaska Highway in southern Yukon. Whitehorse's downtown and Riverdale areas o ...

accurately constrained the

ground track A ground track or ground trace is the path on the surface of a planet directly below an aircraft's or satellite's trajectory. In the case of satellites, it is also known as a suborbital track, and is the vertical projection of the satellite's ...

azimuth from either side. It was found that the Tagish Lake meteorite had a pre-entry Apollo type

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a ...

that brought it from the outer reaches of the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, located roughly between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies, of many sizes, but much smaller than planets, called ...

. Currently, there are only eleven meteorite falls with accurately determined pre-entry orbits, based on photographs or video recordings of the fireballs themselves taken from two or more different angles. Further study of the reflectance spectrum of the meteorite indicate that it most likely originated from

773 Irmintraud 773 Irmintraud, provisional designation 1913 TV, is a dark and reddish, rare-type asteroid from the outer region of the asteroid belt, about 92 kilometers in diameter. It was discovered on 22 December 1913, by German astronomer Franz Kaiser at He ...

, a D-type asteroid.

Comparisons

The double, and not the expected single, plume formation of debris, as seen in video and photographs of the 2013

Chelyabinsk meteor The Chelyabinsk meteor was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately near-Earth asteroid that entered the a ...

dust trail and believed by Peter Brown to have coincided near the primary airburst location, was also pictured following the Tagish Lake fireball, and according to Brown, likely indicates where rising air quickly flowed into the center of the trail, essentially in the same manner as a moving 3D version of a

mushroom cloud A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke and usually condensed water vapor resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently ener ...

References

*'' Universe: The Definitive Visual Dictionary'', Robert Dinwiddie, DK Adult Publishing, (2005), pg. 222. *Mittlefehldt, D.W., (2002), Geochemistry of the ungrouped carbonaceous chondrite Tagish Lake, the anomalous CM chondrite Bells, and comparison with CI and CM chondrites, ''Meteoritics and Planetary Science'' 37: 703–712
See summary of the article

External links

Evidence of sodium rich alkaline water in the Tagish Lake parent body and implications for amino acid synthesis and racemizationTagish Lake meteorite contains clues as to how life may have arisen on Earth
* ttp://www.physorg.com/news65190953.html Ancient rock star finds a home at the University of Albertabr>Researchers' websiteThe Geological Society
Article/Analysis
Brief AbstractTagish Lake meteorite specimen pictures
{{Royal Ontario Museum iconic objects Meteorites found in Canada Planetary science Geography of British Columbia Geography of Yukon Natural history of British Columbia Natural history of Yukon 2000 in Canada 2000 in science Collections of the Royal Ontario Museum