This is a chunk of the Sikhote-Alin meteorite, fell in 1947 in Siberia
This is a chunk of the Sikhote-Alin meteorite, fell in 1947 in Siberia

That is a chunk of rock that, until 1947, was in space. It spent the previous 4.568 billion years touring the solar system as one of the many left over pieces of formation (Bouvier & Wadhwa, 2010).
This small piece (owned by the York University Astronomical Observatory) was part of a much bigger object that fell in the Sikhote-Alin mountains of south east Siberia on the 12th of February 1947; as a result it is known as the Sikhote-Alin meteorite.
[Aside: A ‘meteoroid’ is an object much smaller than asteroid (probably part of an asteroid originally) and a ‘meteorite’ is anything that falls to the ground]
The original meteoroid was approximately 90,000 kg – 100,000 kg in mass, and thus far approximately 25 000 kg of that has been recovered. Typical orbital velocities of meteoroids/asteroids in space are tens of km/s. When entering Earth’s atmosphere, the meteoroid will compress the gas in front of it to very high densities. There is a very famous equation that tells us what happens to a gas that has been compressed, called the ideal gas law:

    \[ PV=nRT. \]

Looking at the equation you can see that if you increase the pressure (P) then the temperature (T) of the gas will also be forced to increase. The other way around, if you decrease the pressure of a gas, its temperature will also decrease. This is something many people may have noticed when using compressed gas in a can, the kind you use to clean computer parts for instance. If you release the gas, the pressure inside the can drops, and the can becomes cold to the touch.
This exact same natural law forces the air in front of a falling meteoroid to very high temperatures. Exposing rock to temperatures of this kind will force it to break up and fall apart. A falling meteoroid may also explode as a result of this sudden increase in pressure on its leading edge, this is known as an air burst.
The Sikhote-Alin fall was probably travelling at about 14 km/s and broke up/exploded at an altitude of approximately 5.6 km (for reference, the Chelyabinsk air burst event air burst at an altitude of 23 km). The fireball and airburst were seen and heard over a geographical area as large as a few hundreds of kilometers.
Many pieces of the Sikhote-Alin meteorite were recovered, allowing researchers to study it in detail. Some highlights: it was mostly made of iron (93%) and nickel (5.9%); this makes it an Iron Meteorite, which are relatively ray (comprising about 6% of all meteorite falls).





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