The Sichote-Alin iron meteorite fell in 1947 in the mountain of the same name in the southeastern part of Russia. Never before in recorded history has an impact of this magnitude been observed, it was an estimated 70-300 (numbers vary widely) ton meteorite weighing about 4 metres in diameter that survived a fiery passage through the atmosphere and impacted the Earth.
At about 10:30 a.m. on February 12, 1947, eyewitnesses in the Sichote-Alin Mountains in the Russian part of the Soviet Union observed a large bolide brighter than the Sun coming from the north and descending at an angle of about 41 degrees. The bright flash and deafening sound of the fall were observed 300 km away from the point of impact near Luchegorsk and about 440 km northeast near Vladivostok. A smoke trail about 32 km long remained in the sky for several hours.
The Sichote-Alin entered the atmosphere at about 12-14 km per second, began to disintegrate, and the largest fragments are believed to have exploded at an altitude of about 5.6 km.
The scattered field for this meteorite formed an elliptical area of 1.3 square kilometres. Some of the fragments formed craters, the largest of which was 26 metres in diameter and 6 metres deep. More than 100 craters were discovered, a record that has never been broken in modern history.
Sikhote-Alin is classified as an iron meteorite belonging to the chemical group IIAB with a coarse octahedrite structure. It consists of approximately 93% iron, 5.9% nickel, 0.42% cobalt, 0.46% phosphorus, 0.28% sulphur and trace amounts of germanium and iridium. Minerals present include taenite, plessite, troilite, chromite, kamacite, and schreibersite.
Sikhote-Alin meteorite samples are of two types:
- individual samples, showing crustal fusion and signs of atmospheric ablation
- shrapnel or fragmented specimens, with sharp edges torn by pieces of metal
