Meteorite Chelyabinsk – Russia

The Chelyabinsk meteorite belongs to the class of "chondritic" meteorites, meaning it contains chondrules - small spheres or round formations found in meteorites that are some of the oldest known formations in the solar system. These formations typically range in size from just micrometres to a few millimetres and are mainly made up of silicates such as olivine and pyroxenes. The formation of chondrules is associated with rapid heating followed by rapid cooling.

This rocky meteorite entered the Earth's atmosphere on 15 February 2013 and subsequently exploded at an altitude of about 30 km above the Earth. It was an estimated 20 metres in size and weighed around 13,000 tonnes. Entering the Earth's atmosphere at a speed of about 19 kilometres per second, it exploded over the city with energy comparable to several dozen atomic bombs. Most of the blast energy was absorbed by the atmosphere, creating a huge shock wave. The fragments hit the Chelyabinsk region of Russia. The largest fragment found weighs over 570 kg and in total over 1000 kg of this meteorite has been found. This is the only documented collision of a foreign body with Earth so far this century.

The Chelyabinsk meteorite probably came from the asteroid belt between Mars and Jupiter. It was a fragment of an asteroid that had undergone several collisions and metamorphosis. Veins of black material that had undergone high-pressure metamorphosis and partially melted in a previous collision were found in several samples of the meteorite. Chondrules in the meteorite showed signs of metamorphosis, suggesting that the original asteroid was once several kilometres below the surface of a larger LL-type chondrite asteroid. The meteorite likely entered into resonance with Jupiter, a common mechanism for expelling material from the asteroid belt, and subsequently entered an orbital path that allowed it to collide with Earth.

The main belt of asteroids

The asteroid belt between Mars and Jupiter is the region in the solar system that lies approximately between the orbits of the planets Mars and Jupiter. This belt is home to a large number of asteroids that orbit the Sun. The main features of this belt include:

1. Asteroid population: the asteroid belt contains millions of asteroids of various sizes, ranging from smaller rocks to larger bodies. The largest known asteroids in this belt are Ceres, which is also classified as a dwarf planet.
2. Origin and evolution: Asteroids in this belt are remnants of the initial accretion process that led to the formation of planets in the early Solar System. They failed to become part of the larger planets, partly due to the gravitational pull of Jupiter, which prevented them from further merging.
3. Types and composition: asteroids in this belt vary in size, chemical composition, and spectral properties. For example, some asteroids are composed of rocks and metals, while others may contain water and organic compounds.
4. Exploration and research: scientists study asteroids in the belt through ground-based and space-based observations and expeditions. These expeditions include the Dawn mission to Ceres and various NASA asteroid missions.