What is a meteorite?

In the clear night sky, sometimes you can see a bright flash flying through the sky, which is a common meteor phenomenon. In the vast space of the solar system, there are countless small dust-like celestial bodies-meteoroids. When they break into the earth's atmosphere at high speed, they rub against the atmosphere and form a luminous phenomenon, which is called "meteor". Because meteoroids are generally small, most meteors burn and vaporize in the upper atmosphere; There are still a few large meteors that have not burned out in the atmosphere, and the debris falling to the ground is called "meteorite", also called "meteorite".

Usually, meteors are like "stragglers" in the night sky, appearing in all directions completely randomly. In addition to this "occasional" meteor, there is also a meteor group that often appears in groups. They have obvious regularity, and appear on a roughly fixed date and in the same sky area, so they are also called periodic meteors. Meteor swarms are a group of meteoroids with roughly the same orbit. When they rush into the earth's atmosphere, they become very beautiful and spectacular meteor showers. When it appears, thousands of meteors are produced near a certain point in the sky like holiday fireworks, which is the so-called radiation point. Usually, the name of the constellation where the radiation point is located is used as the name of the meteor group. For example, the Leonid meteor shower in 1833+065438+ 10 is the most spectacular meteor shower in history, with as many as 35,000 meteors falling every hour. China recorded the Lyra meteor shower in 687 BC, which is the earliest meteor shower record in the world.

Meteors with large original mass fall to the ground and become meteors with different sizes and compositions. There are iron meteorites, stone meteorites, glass meteorites and meteorite ice. The source of meteorites may be fragments of asteroids, satellites or comets, so meteorites carry the original materials of these celestial bodies and contain rich information on the formation and evolution of celestial bodies in the solar system. At present, more than 3,000 samples of falling events have been collected around the world, among which the famous ones are China Jilin meteorite, Namibian Goba meteorite and American Norton meteorite.

There are many craters on the earth, which are the products of meteorite impact. However, due to the weathering of the earth, most of them have been destroyed beyond recognition, and now more than 150 can be confirmed. One of the most famous is a big pit in the desert in northern Arizona, USA. Diameter1245m and depth172m. Several tons of meteorite fragments have been collected in the pit. It is estimated that this is a pothole caused by the fall of an iron meteorite weighing 65,438+10,000 tons about 20,000 years ago.

In addition, a thrilling explosion occurred in Siberia in 1908, which was attributed by some people to the "masterpiece" of a giant meteorite. The explosion shook thousands of miles, destroyed 60 kilometers of forests in Fiona Fang, and the mushroom cloud rose to a height of 20 kilometers. Its power is shocking. However, no meteorite fragments or large craters were found at the scene of the explosion afterwards. According to this, some people think that it is very likely that comets broke into the earth's atmosphere. Because the comet nucleus is mainly composed of ice, it means a rare giant ice event: fragments of a giant comet nucleus rushed into the atmosphere at high speed, and its huge impact on the air led to an earth-shattering explosion.