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
The fall of this meteorite occurred in the daytime, and was observed by many eyewitnesses. The evaluation of this observational data allowed V. G. Fesenkov, chairman of the meteorite committee of the USSR Academy of Science, to compute the orbit of the original body. It is most likely that the former orbit of the Sikhote-Alin meteoroid is similar to that of many other small bodies of the solar system. It is ellipse-shaped, and its point of greatest distance from the sun lies within the asteroid belt. This suggests that the creation of the meteoroid, and its subsequent passage to earth, was precipitated by the collision of asteroids.
[edit] Fall
The Sikhote-Alin meteorite fell in the Sikhote-Alin Mountains, Primorye, Russia, near the village of Paseka (approximately 440 km northeast of Vladivostok) on the morning of February 12, 1947. At around 10:30 am that morning, witnesses reported a fireball brighter than the sun that came out of the north, descending 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. The smoke train, which remained in the sky for several hours, was 32 km long.
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
The specimens from this fall are basically of two types. There are pieces showing ablation and fusion crust, which probably broke off of 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 show evidence of having been either violently torn apart in the atmosphere during the descent or blasted apart upon impact. These pieces are most likely 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
Sikhote-Alin is a coarse iron octahedrite. Its composition is as follows: 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, 0.28% sulfur, smaller amounts of germanium and iridium, and the remainder (approximately 93%) is iron.
The following minerals are present: taenite, plessite, rhabites, troilite, chromite, kamacite, and schreibersite crystals.
