The Sikhote-Alin meteorite fell during daylight at 10:38 a.m. local time on February 12th, 1947 in the Sikhote-Alin mountain range in Russia, about 440 km northeast of Vladivostok. Sikhote-Alin is a massive fall. The overall size has been estimated to be just below 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) put the mass at around 100,000 kg, or 100 tons.
Because the meteorite fell during daytime, it was observed by many eyewitnesses who reported a fireball that was brighter than the sun. It left a trail of smoke and dust estimated to be 32 km long, which remained in the sky for several hours. The bright flash and the deafening sound of the fall were observed three hundred kilometres around the point of impact near the village of Paseka (approximately 440 km northeast of Vladivostok).
The speed of entry was estimated to be 14.5 kilometers per second, which corresponds to 31,000 miles per hour! When the meteorite entered the atmosphere, it started to break apart. The group of fragments fell together.
When the descending group of meteorites reached an altitude of about 3.5 miles, the largest mass apparently broke up in a violent explosion. This was a very low altitude for such an event (about half the altitude at which passenger jets fly).
Sikhote-Alin is one of the most spectacular falls in recorded history. The fragments scattered over an elliptical area of about 1.3 km. The biggest fragments made craters, the largest of which was about 26 m across and 6 m deep.
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.
Types of Sikhote-Alin specimen
- Specimens from this fall are of two types. There are those called “complete individuals“, which show ablation and fusion crust. These are probably the ones that broke off from the main mass early in the decent. The surface was vaporized and eroded by the trip through the atmosphere. These are characterized by regmaglypts – or thumb prints – ablation cavities in the surface of the specimen.
- The second type of Sikhote-Alin specimen is the fragments. These show the violent effects of being torn apart in the atmosphere or of being blasted apart on impact with the ground. A metallurgist would say they were cold-worked. These are probably the fragments from the explosion 3.5 miles high. Many look like shrapnel from violent explosions. Some show shield shapes or orientation. Striations may be seen on some flatter surfaces.
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