The Sikhote-Alin iron meteorite fell in 1947 in the mountain range of the same name in south-eastern Russia. Never before in recorded history has an impact of this magnitude been observed; it was a meteorite weighing an estimated 70-300 tonnes (numbers vary widely), about 4 metres in diameter, which survived a fiery passage through the atmosphere and impacted the Earth.
At about 10:30 a.m. on February 12, 1947, eyewitnesses in the Sikhote-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. A bright flash and deafening crash sound were observed 300km away from the impact site near Luchegorsk and approximately 440km northeast near Vladivostok. A smoke trail about 32 kilometres long remained in the sky for several hours.
The Sikhote-Alin meteorite entered the atmosphere at a speed of about 12-14 kilometres per second, it began to disintegrate and at an altitude of about 5.6km the largest fragments are believed to have exploded.
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.
The Sikhote-Alin meteorite samples are of two types:
- individual samples, showing fusion crust and traces of atmospheric ablation;
- shrapnel or fragmented specimens, with sharp edges torn by pieces of metal.
