Sikhote-Alin meteorite
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The Sikhote-Alin meteorite fall was a massive impact event that occurred on February 12, 1947, approximately 440 km northeast of Vladivostok, Russia.
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[edit] Orbit
Because the meteorite fell during daytime, it was observed by many eyewitnesses. Evaluation of this observational data allowed V. G. Fesenkov, then chairman of the meteorite committee of the USSR Academy of Science, to estimate the meteoroid's orbit before it encountered the Earth. This orbit was ellipse-shaped, with its point of greatest distance from the sun situated within the asteroid belt, similar to many other small bodies crossing the orbit of the Earth. Such an orbit was probably created by collisions within the asteroid belt.
[edit] Fall
At around 10:30 am on February 12, 1947, eyewitnesses in the Sikhote-Alin Mountains, Primorye, Russia, observed a fireball brighter than the sun that came out of the north and descended at an angle of about 41 degrees. The bright flash and the deafening sound of the fall were observed for three hundred kilometres around the point of impact near the village of Paseka (approximately 440 km northeast of Vladivostok). A smoke train, estimated at 32 km long, remained in the sky for several hours.
As the meteorite entered the atmosphere, traveling at a speed of about 14 km/s, it began to break apart, and the fragments fell together. At an altitude of about 5.6 km, the largest mass apparently broke up in a violent explosion.
The strewn field for this meteorite covered an elliptical area of about 1.3 km². Some of the fragments made craters, the largest of which was about 26 m across and 6 m deep. Fragments of the meteorite were also driven into the surrounding trees.
[edit] Description of the meteorites
Specimens of the Sikhote-Alin Meteorite are basically of two types; pieces showing fusion crust and signs of ablation, and those showing evidence of violent fragmentation. The first probably broke off the main object early in the descent. These pieces are characterized by regmaglypts (cavities resembling thumb prints) in the surface of each specimen. The second type are fragments which were either torn apart in the atmosphere during the descent or blasted apart upon impact. Most were probably the result of the explosion at 5.6 km altitude.
[edit] Size
Sikhote-Alin is a massive fall. The overall size has been estimated at just under 900,000 kg. A large specimen is on display in Moscow, and a great number of smaller specimens have made their way into the collector's market.
Krinov had estimated the post atmospheric mass of the meteoroid at some 70,000 kg. A more recent estimate by Tsvetkov (and others) puts the mass at around 100,000 kg. [1]
[edit] Structure and chemical composition
The Sikhote-Alin meteorite is classified as a coarse octahedrite. It is composed of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, and 0.28% sulfur, with trace amounts of germanium and iridium. Minerals present include taenite, plessite, rhabites, troilite, chromite, kamacite, and schreibersite.
[edit] Other
