In southeastern Russia, an

iron meteorite Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron me ...

fell on the

Sikhote-Alin The Sikhote-Alin (, , , ) is a mountain range in Primorsky and Khabarovsk Krais, Russia, extending about to the northeast of the Russian Pacific seaport of Vladivostok. The highest summits are Tordoki Yani at above sea level, Ko Mountain () ...

mountains in 1947. Large iron

meteorite falls A meteorite fall, also called an observed fall, is a meteorite collected after its fall from outer space, that was also observed by people or automated devices. Any other meteorite is called a " find". There are more than 1,300 documented fall ...

have been witnessed, and fragments have been recovered, but never before in

recorded history Recorded history or written history describes the historical events that have been recorded in a written form or other documented communication which are subsequently evaluated by historians using the historical method. For broader world h ...

has a fall of this magnitude occurred. An estimated 23

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...

s of fragments survived the fiery passage through the atmosphere and reached the Earth.

Impact

At around 10:30 AM on 12 February 1947, eyewitnesses in the Sikhote-Alin Mountains, Primorye, Soviet Union, observed a large

bolide A bolide is normally taken to mean an exceptionally bright meteor, but the term is subject to more than one definition, according to context. It may refer to any large Impact crater, crater-forming body, or to one that explodes in the atmosphere. ...

brighter than the

sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

that came out of the north and descended at an angle of about 41 degrees. The bright flash and the loud sound of the fall were observed for around the point of impact not far from Luchegorsk and approximately northeast of

Vladivostok Vladivostok ( ; , ) is the largest city and the administrative center of Primorsky Krai and the capital of the Far Eastern Federal District of Russia. It is located around the Zolotoy Rog, Golden Horn Bay on the Sea of Japan, covering an area o ...

. A smoke trail, estimated at long, remained in the sky for several hours. As the meteor, traveling at a speed of about , entered the atmosphere, it began to break apart, and the fragments fell together, some burying themselves deep. At an altitude of about , the largest mass apparently broke up in an explosion called an

air burst An air burst or airburst is the detonation of an explosive device such as an anti-personnel artillery shell or a nuclear weapon in the air instead of on contact with the ground or target. The principal military advantage of an air burst over ...

. On November 20, 1957 the

Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...

issued a stamp for the 10th anniversary of the Sikhote-Alin meteorite shower. It reproduces a painting by P. I. Medvedev, a Soviet artist who witnessed the fall: he was sitting in his window starting a sketch when the fireball appeared and immediately began drawing what he saw.

Orbit

Because the

meteor A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a ...

fell during the 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 In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

before it encountered the Earth. This orbit was

ellipse In mathematics, an ellipse is a plane curve surrounding two focus (geometry), focal points, such that for all points on the curve, the sum of the two distances to the focal points is a constant. It generalizes a circle, which is the special ty ...

-shaped, with its point of greatest distance from the

situated within the

asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...

, similar to many other small bodies crossing the orbit of the Earth. Such an orbit was probably created by collisions within the asteroid belt.

Mass

Sikhote-Alin is a massive fall, with the pre-atmospheric mass of the

meteoroid A meteoroid ( ) is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than ''asteroids'', ranging in size from grains to objects up to wide. Objects smaller than meteoroids are classifie ...

estimated at approximately . A more recent estimate by Tsvetkov (and others) puts the mass at around . Krinov estimated the post-atmospheric mass of the meteoroid to be some .

Strewn field and craters

The

strewn field A strewn field is the area where meteorites from a single meteorite fall, fall are dispersed. It is also often used for the area containing tektite, tektites produced by a large meteorite impact.''Tektites in the geological record: showers of glas ...

for this meteorite covered an elliptical area of about . Some of the fragments made

impact craters An impact crater is a depression in the surface of a solid astronomical body formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically ...

, the largest of which was about across and deep. Fragments of the meteorite were also driven into the surrounding trees, embedding themselves.

Composition and classification

The Sikhote-Alin meteorite is classified as an

belonging to the meteorite group IIAB and with a coarse

octahedrite Octahedrites are the most common Iron meteorite#Structural classification, structural class of iron meteorites. The structures occur because the meteoric iron has a certain nickel concentration that leads to the exsolution of kamacite out of tae ...

structure. It is composed of approximately 93%

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

, 5.9%

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

, 0.42%

cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

, 0.46%

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

, and 0.28%

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

, with trace amounts of

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

and

iridium Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group, is considered the second-densest naturally occurring metal (after osmium) with a density ...

. Minerals present include

taenite Taenite is a mineral found naturally on Earth mostly in iron meteorites. It is an alloy of iron and nickel, with a chemical formula of and nickel proportions of 20% up to 65%. The name is derived from the Greek ταινία for "band, ribbo ...

, plessite,

troilite Troilite () is a rare iron sulfide mineral with the simple formula of FeS. It is the iron-rich endmember of the pyrrhotite group. Pyrrhotite has the formula Fe(1−x)S (x = 0 to 0.2) which is iron deficient. As troilite lacks the iron deficiency ...

chromite Chromite is a crystalline mineral composed primarily of iron(II) oxide and chromium(III) oxide compounds. It can be represented by the chemical formula of Iron, FeChromium, Cr2Oxygen, O4. It is an oxide mineral belonging to the spinel group. The ...

kamacite Kamacite is an alloy of iron and nickel, which is found on Earth only in meteorites. According to the International Mineralogical Association (IMA) it is considered a proper nickel-rich variety of the mineral native iron. The proportion iron:ni ...

, and

schreibersite Schreibersite is generally a rare iron nickel phosphide mineral, , though common in iron-nickel meteorites. It has been found on Disko Island in Greenland and Illinois. Another name used for the mineral is rhabdite. It forms tetragonal crystals ...

Specimens

Specimens of the Sikhote-Alin Meteorite are basically of two types: # ''individual'', ''thumbprinted'' or ''regmaglypted specimens'', showing fusion crust and signs of atmospheric

ablation Ablation ( – removal) is the removal or destruction of something from an object by vaporization, chipping, erosion, erosive processes, or by other means. Examples of ablative materials are described below, including spacecraft material for as ...

# ''shrapnel'' or ''fragmented specimens'', sharp-edged pieces of torn metal showing evidence of violent fragmentation The first type probably broke off the main object early in the descent. These pieces are characterized by regmaglypts (cavities resembling thumbprints) on the surface of each specimen. The second type are fragments which were either torn apart during the atmospheric explosions or blasted apart upon impact on the frozen ground. Most resulted from the explosion at 5.6 km (3.5 mi) altitude. A large specimen is on display in

Moscow Moscow is the Capital city, capital and List of cities and towns in Russia by population, largest city of Russia, standing on the Moskva (river), Moskva River in Central Russia. It has a population estimated at over 13 million residents with ...

. Many other specimens are held by Russian Academy of Science and many smaller specimens exist in the collectors' market. File:Sikhote_Alin_Eisenmeteorit_1.3kg.JPG, Thumbprinted individual File:Sikalin179.jpg, Oriented individual File:Sikhote-Alin meteorite, shrapnel.jpg, Shrapnel sample File:Barringer Crater 2015 039.jpg, A piece on display at Meteor Crater, Arizona

References

External links

* {{DEFAULTSORT:1947 Sikhote-Alin meteorite

Primorsky Krai Modern Earth impact events Holocene impact craters Geography of Russia 1947 in science 1947 in the Soviet Union

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

February 1947 in Asia 1947 natural disasters