The shape of this melt comes in a variety of shapes.

In a nutshell, the metamorphic molten body left on the surface of a small body is the crust, crater, and trough of a small body.

The metamorphic melt left inside the small celestial body is the wall of the lava cave and the melt belt.

Observations of meteorites have shown that the thickness of the molten crust produced by each impact is generally between one millimeter and ten millimeters.

When a small object is hit by thousands of gravel or dust particles, a large number of small local melts are superimposed to form the outer shell of the small body.

In general, the greater the impact, the greater the melt and the thicker the outer shell of the small object built.

Usually the shells of the small objects we see on meteorites are a few millimeters or more centimeters thick.

Take a look at the large meteorite in Xinjiang, the thick shell was built by the impact of thousands of gravel and sand particles.

Collisions between small celestial bodies often change the structure and structure of their interiors.

For example, chondrites can be changed to nochondrites, and of course, nodulares can be transformed into chondrites.

A small celestial body falling to the ground is a meteorite.

When it passes through the earth's atmosphere, it produces strong friction with the air, and under the action of high pressure and high temperature, its appearance will often melt and deteriorate, and after cooling, a layer of molten crust with a thickness of about one millimeter will be born on the surface of the meteorite.

Generally speaking, there are two kinds of molten crusts of the same meteorite, one is the molten crust produced by the collision between asteroids in space, and the other is the molten crust produced by entering the Earth's atmosphere and rubbing against the air.

When meteorites fly at high altitudes, the surface temperature reaches several thousand degrees.

At such high temperatures, the surface of the meteorite melts into liquid.

Later, due to the blockage of the dense atmosphere in the lower layers, his speed became slower and slower, and the molten surface cooled down, forming a thin crust called "molten crust".

The molten shell is very thin, generally around 1 mm, and the color is black or brown.

In the process of cooling the molten shell, the traces of air flowing on the surface of the meteorite are also retained, which are called "gas marks".

The air mark looks a lot like a finger print pressed on the dough.

Molten crusts and air marks are the main features of the surface of meteorites.

If you see a rock or iron with such a molten shell or air mark on its surface, you can immediately conclude that it is a meteorite.

However, some meteorites that fall older are due to long-term wind, sun and rain, and the molten shell has fallen off, and the air mark is not easy to identify, but that doesn't matter, there are other ways to identify it.

A stony meteorite looks a lot like a rock on Earth, and if you weigh it by hand, you will feel that it is heavier than a rock of the same volume.

Stony meteorites generally contain a few percent of iron, which is magnetic, and you can feel it when you try it with a magnet.

In addition, if you look closely at the cross-section of the stony meteorite, you will find that there are quite a few small chondrites.

Pellets are generally about 1 mm, and some are larger than 2~3 mm.

More than 90% of stony meteorites have such chondrites, which are produced when meteorites are generated, and are an important marker for identifying stony meteorites.

The main components of iron meteorites are iron and nickel. Among them, iron accounts for about 90%, and the nickel content is generally between 4~8%, and the nickel content in the earth's natural iron is generally not so much.

A section is cut on an iron meteorite, polished, and eroded with 5% nitric acid alcohol, and the shiny end face will show special stripes, like a lattice.

This is because the iron meteorite itself is unevenly distributed, some places contain more nickel, some places have less, the part with more nickel content is chemically stable, not easy to be corroded by acid, and the part with less nickel content is corroded by acid and becomes rough and dull, so that these bright and dark parts form a lattice-like stripe. These streaks occur with the exception of a very small number of meteorites with a very high nickel content.

This is one of the main methods of identifying iron meteorites.

Stony-iron meteorites are extremely rare and are composed of stone and iron, which contain roughly equal iron and silicate ores!.

Among the three types of meteorites, the stone meteorite is the most, on March 8, 1976, a large-scale meteorite rain landed in Jilin area of China, which is a stony chondrite meteorite rain.

The meteorite rain scattered an area of 4 to 500 square kilometers, and more than 100 meteorites were collected, with a total weight of more than 2,600 kilograms. Among them, the largest meteorite No. 1 weighs 1,770 kilograms, which is the heaviest stone meteorite found in the world.

In second place is the American Nortonite meteorite, which weighs 1079 kilograms.

Iron meteorites are much heavier than stony meteorites, and the heaviest piece is in Namibia, Africa, with the name Goba meteorite, which weighs 60 tons.

The large meteorite in Xinjiang, China, which I just mentioned, is called "Silver Camel", which weighs 30 tons, ranking third in the world.

Most meteoroids disintegrate when they enter the atmosphere, and it is estimated that there are still about 500 meteorites per year, ranging from marbles to basketballs, to the ground, but usually only 5 to 10 meteors are found to fall each year and are known and recovered by scientists.

A few meteorites are large enough to create huge impact craters, while others are not large enough to reach terminal velocity when they hit the ground, creating at most a small crater.

Large meteorites may hit the ground at speeds close to their second cosmic velocity, leaving a crater under a super-high-velocity impact.

The type of crater depends on the size of the meteorite, its composition, the degree of fragmentation, and the angle of impact it enters.

The force of this collision has the potential to cause widespread damage.

The most common hypervelocity impacts on Earth are caused by iron meteorites, which are the easiest to pass through the atmosphere.

Examples of impact craters caused by iron meteorites include Barringer Crater, Odessa Crater, Waba Crater, and Wolf Creek Crater, where associated iron meteorites have been found.

In contrast, large enough stony meteoroids or snow globes or asteroids like comets, even if they weigh millions of metric tons, can still be destroyed as they enter and pass through the atmosphere without leaving impact craters.

There are exceptions where impact craters are left behind, and although this phenomenon is rare, it can cause alarming oscillations, as was the case with the famous Tunguska event.

Very large stony meteoroids, hundreds of meters in diameter or larger, with masses of tens of millions of metric tons or more, can fall to the Earth's surface and strike large impact craters that will shock the world.

Such impacts are usually accompanied by enormous energy, so that the impact is completely destroyed and no meteorites remain.

Fireballs as meteoroids pass through the atmosphere can be very bright, even comparable to the intensity of the Sun, yet most are faint and even go unnoticed during the day.