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

A number of colors have been reported, including yellow, green, and red. As objects shatter, there will be flashes of light and explosions. When a meteorite falls, it is common to hear an explosion, fragmentation, or rumbling sonic boom from the shock wave caused by the major fragmentation event. It can be heard over a wide range, with a radius of hundreds of kilometers or more, and sometimes whistles or hiss can be heard, but there is a lack of understanding. After the fireball has passed, tails of soot are often seen remaining in the atmosphere for several minutes.

The meteoroid is heated on its way into the atmosphere, and its surface melts and undergoes an experience of ablation. In the process, they can be sculpted into a variety of different shapes, appearing on the surface and leaving a shallow fingerprint-like depression known as an air mark.

If the meteoroid remains in a fixed position and does not tumble forward for a period of time, it may form a tapered nose cone or a heat mask. When it slows down, it eventually solidifies the melted surface layer into a thin molten crust. In most meteorites, this layer is black (in some grainless meteorites, the molten crust may be very bright in color).

In stony meteorites, the heat-affected zone is only a few millimeters deep at most, and in iron meteorites, it is a better conductor of heat, and metal structures up to 1 cm (0.39 in) below the surface may be affected by high temperatures, but reports vary. Some meteorites have been reported to have the sensation of being burned hot to the touch after landing, while others are cold enough to freeze the water into frost. From many falling meteorites, like Bju

bole, Lake Tagish meteorite, and Buzza

d Coulee, found falling in an icy lake or sea, perhaps they were not hot at the time of the fall.

Meteoroids break apart in the atmosphere, and meteorite rain can form, with meteorites falling from a few to thousands. The area where these meteorite showers fall is called the dispersion zone, which is usually in the shape of an ellipse, with the direction of the long axis parallel to the direction of the meteor's flight. In most cases, the largest meteorite in a meteorite shower will fall at the farthest distance of the dispersal area

Meteorites have had a small chance of hitting humans and animals since records began in modern times, but there have been few human casualties. But in early 2016, according to Indian authorities, a car was hit by a meteorite. Three people were injured, and the driver was unfortunately killed. It was also the first time on record that a meteorite fell to a fatal person.

Meteorites are usually divided into four categories according to the level of iron-nickel metal content in their interiors: stony meteorites, iron meteorites, stony-iron meteorites, and glass meteorites. The iron-nickel metal content in stony meteorites is less than or equal to 30%. The iron-nickel content of stony-iron meteorites ranges from 30% to 65%. Iron meteorites contain 95% or more iron-nickel metal. Glass meteorites do not contain metal components.

Most of the meteorites were chondrites (91.5% of the total), of which common chondrites were the most abundant (80% of the total). Chondrites are characterized by the presence of large numbers of silicate spheres ranging in millimeter to submillimeter size (see figure). Chondrites are the most primitive materials in the solar system, the products of direct condensation from the primordial solar nebula, and their average chemical composition represents the chemical composition of the solar system. The largest stony meteorite in the world is the Jilin common chondrite meteorite that fell in Jilin Province in China in 1976, of which the No. 1 meteorite weighs about 1,770 kilograms.

Nonchondrites, stony-iron meteorites and iron meteorites are collectively known as differentiation meteorites, which are the products of chondrite meteorites that are differentiated and crystallized by high-temperature melting, and represent samples of different levels inside the asteroid. The internal structure of these asteroids is similar to that of Earth, with three layers, with an iron core (iron meteorite) in the center, a mixed mantle layer of stone and iron (stone iron meteorite) in the middle, and a stony crust (chondrite meteorite) on the outside. The largest iron meteorite in the world is the Hoba iron meteorite in Namibia, Africa, weighing 60 tons. The iron meteorite found in Yinniugou County, Altay Prefecture, Xinjiang, China, weighs about 28 tons and is the third largest iron meteorite in the world.

Stony-iron meteorites are composed of iron, nickel and silicon, acid, and salt minerals, with an iron-nickel metal content of 30 to 65, and this type of meteorite accounts for about 1.2 of the total number of meteorites, so it has the highest commercial value. This kind of meteorite contains more than 70% iron, followed by silicon, aluminum, nickel, the main minerals are conestone, nickel stone, synthelite, etc., and the secondary minerals are meteorite iron, chromite, graphite, etc. According to the main components and structural characteristics of the internal meteorite, stony meteorites are divided into: olivine iron meteorites (PAL), medium iron meteorites (MES), bronze pyroxene - lemopitoquite iron meteorites.

Stony meteorites are composed of silicate minerals such as olivine, pyroxene and a small amount of plagioclase, and also contain a small amount of metallic iron particles, sometimes up to more than 20. Density 3 to 3.5. Stony meteorites account for 95% of the total number of meteorites. At 3 p.m. on March 8, 1976,

Jilin area is 12 kilometers from east to west, 8 kilometers from north to south, with a total area of more than 500 square kilometers, a meteorite rain that is rare in the world falls. More than 200 meteorites were collected, and the largest No. 1 meteorite weighed 1,770 kilograms, ranking the heaviest single meteorite in the world. On the surface of the Jilin meteorite, there are black, black-brown molten crusts and gas marks of different sizes. The chemical composition was 37.2 for SiO2, 3.19 for MgO2 and 28.43 for Fe. The main minerals are noble olivine, bronze pyroxene, ferrolite, and meteorite iron. Minor minerals are monoclinic pyroxene, plagioclase, etc.

Stony meteorites can be divided into two categories according to whether they contain chondrites inside: chondrites and non-chondrites. Chondrites are divided into five chemical groups: E, H, L, LL, and C according to chemopetrological classification. Group E has the highest content of iron-nickel metals, formed in an extremely reducing environment, with little iron oxide in olivine and pyroxene. Complex C has the lowest iron-nickel content (or no iron-nickel metal component) and is formed in a fairly oxidized environment with the highest ratio of iron oxide content in olivine to pyroxene. The formation environment of H, L, LL groups is between E group and C group, and its characteristics are also between E group and C group.

According to the level of calcium oxide content, chondrites are divided into two categories: calcium-poor chondrites and calcium-rich chondrites. The calcium oxide content in calcium-poor chondrites is less than or equal to 3%. Calcium-rich chondrites contain more than or equal to 5% calcium oxide.

Iron meteorites contain 90% iron and 8% nickel. Its exterior is covered with a black or brown 1 mm thick oxide layer called a molten shell. There are also many large and small round pits on the exterior called air marks. In addition, there are grooves of different shapes, called melt grooves. These are formed due to the fact that they have a violent friction and combustion with the atmosphere during the fall. The facets of iron meteorites are as bright as those of pure iron.

Iron meteorites account for about 3c/o of the total number of meteorites. The world's No. 3 iron meteorite was discovered in Qinghe County, Xinjiang, China at the end of the 19th century, with a size of 2.42×1.85×1.37 and a weight of about 30 tons. The meteorite contains 88.67 c/o iron and 9.27 c/o nickel. It contains a variety of minerals that are not found on Earth, such as cononeite, nickel and other cosmic minerals. Among them, the iron meteorite with high nickel content is black and green all over, and yellowish, and is commonly known as the black treasure green meteorite, which belongs to the top grade of meteorites.

Iron meteorites are divided into four categories: I(A, B, C), II (A, B, C, D, E), III (A, B, C, D, E), and IV(a, b) according to the relative abundance and nickel content of the main chemical groups in their interior.

Namibia (weighing 60 tons), scientists from all over the world have collected a large number of meteorite samples in the Antarctic region and the desert areas of Africa, including rare and precious lunar meteorites and Martian meteorites.

(ALH84001) American scientists reported in 1996 that signs of life on Mars had been found in this Martian meteorite.

The Chinese Antarctic expedition team has discovered and recovered 4,480 meteorites in the Grove Mountain area of Antarctica three times, two of which are meteorites from Mars, "GRV99027" and "GRV020090". The Martian meteorite GRV99027 weighs 9.97 grams and is covered with a thin black molten crust. The Martian meteorite "GRV020090" weighs 7.54 grams. These two Martian meteorites belong to the rarer peridotite, and there are only six such meteorites in the world.

During China's 30th Antarctic scientific expedition, expedition members found a total of 583 meteorites in the Grove Mountain area of Antarctica. After nearly a year of hard work, Guilin University of Technology classified and named 149 of the samples. Among them, the largest meteorite is 1,300 grams, which has been detected as a Vesta meteorite, and has been numbered as GRV13001 in accordance with international practice.

"Outwardly, this Vesta meteorite has a relatively complete molten shell, the molten shell is dark gray, and the internal texture is grayish-white. Through microscopic observation, the meteorite has a breccia structure, the breccia has a subdiabase structure, and the matrix clastic mineral assemblage and composition are exactly the same as the breccia, which belongs to the basalt meteorite. Miao Bingkui said, "This rocky meteorite has three possibilities: Mars, the moon, and asteroids. According to the analysis of mineral composition and oxygen isotopes, the possibility of coming from Mars and the Moon is ruled out, and it should be from Vesta, which is a calcium-long radiance and long chondrite meteorite, which belongs to the Vesta meteorite. ”

Lunar meteorites can be divided into two categories: volcanic rocks and sedimentary rocks, and lunar basalt is one of the main rocks that make up the moon, with black, white, and dark purple colors

Color, fuchsia, green, dark green (commonly known as black treasure green), gray-green, yellow, brown-yellow, mixed colors, etc. Speckle structure and almond structure with biotite. Common sulfides found in lunar meteorites are meteorite iron, pyrite, chalcopyrite, chalcopyrite, sulfurinite and unknown minerals.

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