On the Trail of the Great Canadian Meteorites
Meteorite Basics
Meteoroid - a solid body in interplanetary space before it reaches the Earth's atmosphere. A rock in space.
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Meteor is the fiery streak or "shooting star" light show when a meteoroid strikes the Earth's atmosphere and burns up. Most meteors are no more than a few centimeters in diameter.
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A fireball is a meteor brighter than the planets or the moon.
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A bolide is a very bright fireball seen to explode or break-up in the air.
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A larger space rock which survives the fiery passage through the Earth's atmosphere as a meteor and strikes the Earth's surface is called a meteorite. A rock on the ground.
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A space rock that hits something on the earth, like a person, animal, house or car, is a special meteorite called a hammer.
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Meteoric material less than a tenth of a millimeter in diameter is called cosmic dust.
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Picture - Calgary Police Dashcam still of the Buzzard Coulee Meteor (bolide flash on right).
Seconds later it became many Buzzard Coulee meteorites !
"The oldest, coldest, hottest, farthest, fasted natural object you will ever hold in your hands"
- Oldest - formed before the solar system. 4.55 billion years old.
- Coldest - minus 100 C degrees in space
- Hottest - 2000 C degrees on entry
- Fastest - enter atmosphere at 12 - 72 km / sec, 27,000 mph. Hit ground usually at 200 - 300 mph.
- Farthest - average distance travelled in the solar system before reaching earth is an astonishing 250,000,000 miles !
- "Organic" - some contain the building blocks of life such as amino acids.
- "Epic !" - have influenced the course of life on our planet, eg the demise of dinosaurs and the rise of mammals **.
3 Types of Meteorites
"Stones" - Chondrites are the most common type of "stone" meteorite.
"Irons"
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"Stoney - Irons"
MAIN SUB-TYPES OF METEORITES
“STONES”
Composed of silicates, generally 27% or less iron content
1) CHONDRITES - contain small round or oval chondrules.
The most primitive chondrites are made of material from the early solar system nebula
Asteroids are composed of accreted chondritic material
- Carbonaceous chondrites - contain carbon compounds and ‘CAI’s’ - most primitive meteorites. The asteroids Ceres and Pallas are made of carbonaceous chondrite !
2) ACHONDRITES - stony meteorites that have been altered by melting, don’t contain chondrules - eg;
- “SNC” meteorites - originate on Mars !
- “HED” meteorites - originate on asteroid Vesta ! (Howardites - mixed eucrite and diogenite; Eucrites - from crust; Diogenites - from mantle)
- Some achondrites originate from the Moon or even possibly the planet Mercury !
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“IRONS”
Almost completely metallic - contain over 90% iron and nickel
Originate in the core of a large asteroid or planet.
1) octahedrites - cut surface displays an 8-sided crystal pattern (Widmanstatten pattern)
2) hexahedrites - display 6-sided crystal pattern
3) ataxites - no visible crystal lines
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“STONY - IRONS”
- rare, about 3% of known meteorites
1) Pallasites - large olivine crystals in a background network (matrix ) of metal
2) Mesosiderites - bits of iron/nickel in a stony matrix
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