A meteorite is a solid body of natural cosmic origin that has fallen to the surface of the planet and has a size of 2 mm or more. Bodies that have reached the surface of the planet and have sizes from 10 microns to 2 mm are usually called micrometeorites; smaller particles are cosmic dust. Meteorites are characterized by different composition and structure. These features reflect the conditions of their origin and allow scientists to more confidently judge the evolution of bodies. solar system.

Types of meteorites by chemical composition and structure

The meteorite substance is mainly composed of mineral and metal components in various proportions. The mineral part is iron-magnesium silicates, the metal part is represented by nickel iron. Some meteorites contain impurities that determine some important features and carry information about the origin of the meteorite.

How are meteorites divided? chemical composition? Traditionally, three large groups are distinguished:

• Stony meteorites are silicate bodies. Among them are chondrites and achondrites, which have important structural differences. So, chondrites are characterized by the presence of inclusions - chondrules - in the mineral matrix.
• Iron meteorites composed predominantly of nickel iron.
• Iron-stone - bodies of an intermediate structure.

In addition to a classification that takes into account the chemical composition of meteorites, there is also the principle of dividing "heavenly stones" into two broad groups according to structural features:

• differentiated, which include only chondrites;
• undifferentiated - an extensive group that includes all other types of meteorites.

Chondrites - remnants of a protoplanetary disk

A distinctive feature of this type of meteorites is chondrules. They are mostly silicate formations of an elliptical or spherical shape, about 1 mm in size. The elemental composition of chondrites is almost identical to the composition of the Sun (if we exclude the most volatile, light elements - hydrogen and helium). Based on this fact, scientists came to the conclusion that chondrites were formed at the dawn of the existence of the solar system directly from the protoplanetary cloud.

These meteorites have never been part of large celestial bodies that have already undergone magmatic differentiation. Chondrites were formed by condensation and accretion of protoplanetary matter, while experiencing some thermal effects. The substance of chondrites is quite dense - from 2.0 to 3.7 g / cm 3 - but fragile: a meteorite can be crushed by hand.

Let's take a closer look at the composition of meteorites of this type, the most common (85.7%) of all.

carbonaceous chondrites

Carbonaceous rocks are characterized by a high content of iron in silicates. Their dark color is due to the presence of magnetite, as well as impurities such as graphite, soot and organic compounds. In addition, carbonaceous chondrites contain water bound in hydrosilicates (chlorite, serpentine).

According to a number of characteristics, C-chondrites are divided into several groups, one of which - CI-chondrites - is of exceptional interest to scientists. These bodies are unique in that they do not contain chondrules. It is assumed that the substance of meteorites of this group was not subjected to thermal impact at all, that is, it remained practically unchanged since the time of condensation of the protoplanetary cloud. These are the oldest bodies in the solar system.

Organics in meteorites

In carbonaceous chondrites, organic compounds such as aromatic and carboxylic acids, nitrogenous bases (in living organisms they are part of nucleic acids) and porphyrins are found. Despite the high temperatures experienced by a meteorite as it passes through earth's atmosphere, hydrocarbons are preserved due to the formation of a melting crust, which serves as a good heat insulator.

These substances, most likely, are of abiogenic origin and testify to the processes of primary organic synthesis already in the conditions of a protoplanetary cloud, given the age of carbonaceous chondrites. So the young Earth already at the earliest stages of its existence had the source material for the emergence of life.

Ordinary and enstatite chondrites

The most common are ordinary chondrites (hence their name). These meteorites contain, in addition to silicates, nickel iron and bear traces of thermal metamorphism at temperatures of 400–950 °C and shock pressures of up to 1000 atmospheres. The chondrules of these bodies are often irregular in shape; they contain detrital material. Ordinary chondrites include, for example, the Chelyabinsk meteorite.

Enstatite chondrites are characterized by the fact that they contain iron mainly in the metallic form, and the silicate component is rich in magnesium (enstatite mineral). This group of meteorites contains less volatile compounds than other chondrites. They underwent thermal metamorphism at temperatures of 600-1000 °C.

Meteorites belonging to both of these groups are often fragments of asteroids, that is, they have been in the composition of small protoplanetary bodies in which the processes of interior differentiation did not take place.

Differentiated meteorites

Let us now turn to the consideration of what types of meteorites are distinguished by chemical composition in this large group.

Firstly, these are stone achondrites, secondly, iron-stone and, thirdly, iron meteorites. They are united by the fact that all representatives of these groups are fragments of massive bodies of asteroid or planetary size, the interior of which has undergone differentiation of matter.

Among differentiated meteorites, there are both fragments of asteroids and bodies knocked out from the surface of the Moon or Mars.

Features of differentiated meteorites

Achondrite does not contain special inclusions and, being poor in metal, is a silicate meteorite. In composition and structure, achondrites are close to terrestrial and lunar basalts. Of great interest is the HED group of meteorites, thought to originate from the mantle of Vesta, which is thought to be a preserved protoplanet. terrestrial group. They are similar to the ultramafic rocks of the Earth's upper mantle.

Stony iron meteorites - pallasite and mesosiderite - are characterized by the presence of silicate inclusions in a nickel iron matrix. Pallasites got their name in honor of the famous Pallas iron found in the 18th century near Krasnoyarsk.

Most iron meteorites are distinguished by an interesting structure - "widmanstätten figures" formed by nickel iron with different nickel content. Such a structure was formed under conditions of slow crystallization of nickel iron.

The history of the substance of "heavenly stones"

Chondrites are messengers from the most ancient era of the formation of the solar system - the time of accumulation of pre-planetary matter and the birth of planetesimals - the embryos of future planets. Radioisotope dating of chondrites shows that their age exceeds 4.5 billion years.

As for differentiated meteorites, they show us the formation of the structure of planetary bodies. Their substance has distinct signs of melting and recrystallization. Their formation could take place in different parts of the differentiated parental body, which subsequently underwent complete or partial destruction. This determines what chemical composition of meteorites, what structure formed in each case, and serves as the basis for their classification.

Differentiated celestial guests also contain information about the sequence of processes that took place in the depths of the parent bodies. Such, for example, are iron-stone meteorites. Their composition testifies to the incomplete separation of the light silicate and heavy metal components of the ancient protoplanet.

In the processes of collision and fragmentation of asteroids of different types and ages, the surface layers of many of them could accumulate mixed fragments of various origins. Then, as a result of a new collision, a similar “composite” fragment was knocked out from the surface. An example is the Kaidun meteorite containing particles of several types of chondrites and metallic iron. So the history of meteorite matter is often very complex and confusing.

At present, much attention is paid to the study of asteroids and planets with the help of automatic interplanetary stations. Of course, it will contribute to new discoveries and a deeper understanding of the origin and evolution of such witnesses to the history of the solar system (and our planet as well) as meteorites.

Origin of meteorites

At present, at least 500 tons of meteorite material are stored in many museums of the world. The calculation shows that about 10 tons of matter falls on the Earth in the form of meteorites and meteoric dust per day, which over a period of 2 billion years gives a layer 10 cm thick.

The source of almost all small meteor particles are, apparently, comets. Large meteoroids are of asteroid origin.

Russian scientists - Academician V.G. Fesenkov, S.V. Orlov and others believe that comets and meteorites are closely related. Asteroids are giant meteorites, and meteorites are very small, dwarf comets. Both are fragments of planets that, billions of years ago, moved around the Sun between the orbits of Mars and Jupiter. These planets apparently fell apart as a result of the collision. Countless fragments of various sizes were formed, down to the smallest grains. These fragments are now worn in interplanetary space and, colliding with the Earth, fall on it in the form of meteorites.

The composition of meteorites and their substances

In some cases, a large meteoroid during its movement in the atmosphere does not have time to evaporate and reaches the Earth's surface. This remnant of a meteoroid is called a meteorite. Approximately 2,000 meteorites fall on Earth every year.

Depending on the chemical composition, meteorites are subdivided into stony chondrites (their relative abundance is 85.7%), stony achondrites (7.1%), iron (5.7%), and stony-iron meteorites (1.5%). Chondrules are small round particles of gray color, often with a brown tint, abundantly interspersed in the stone mass.

Iron meteorites are almost entirely composed of nickel iron. It follows from the calculations that the observed structure of iron meteorites is formed if, in the temperature range from about 600 to 400C, the substance cools at a rate of 1° - 10°C per million years.

Stony meteorites that do not have chondrules are called achondrites. The analysis showed that chondrules contain almost all chemical elements. Most often in meteorites are the following eight chemical elements: iron, nickel, sulfur, magnesium, silicon, aluminum, calcium and oxygen. All other chemical elements of the periodic table are found in meteorites in negligible, microscopic quantities. When combined chemically, these elements form various minerals. Most of these minerals are found in terrestrial rocks. And absolutely in insignificant quantities in meteorites were found such minerals that are not and cannot be on Earth, since it has an atmosphere with a high content of oxygen. Combining with oxygen, these minerals form other substances. Iron meteorites are almost entirely composed of iron combined with nickel, while stony meteorites are mainly composed of minerals called silicates. They are composed of compounds of magnesium, aluminum, calcium, silicon and oxygen.

Of particular interest is the internal structure of iron meteorites. Their polished surfaces become shiny like a mirror. If such a surface is etched with a weak solution of acid, then usually an intricate pattern appears on it, consisting of individual strips and narrow borders intertwined with each other. Parallel thin lines appear on the surfaces of some meteorites after etching. All this is the result of the internal crystal structure of iron meteorites. No less interesting is the structure of stone meteorites. If you look at the break of a stone meteorite, then often even with the naked eye you can see small rounded balls scattered over the surface of the break. These balls sometimes reach the size of a pea. In addition to them, scattered tiny shiny particles are visible in the fracture. white color. These are nickel iron inclusions. Among these particles there are golden sparkles - inclusions of a mineral consisting of iron in combination with sulfur. There are meteorites, which are, as it were, an iron sponge, in the voids of which grains of a yellowish-green color of the mineral olivine are enclosed.

Meteorites are divided into three large classes: iron, stony, and stony-iron.

Iron meteorites are composed primarily of nickel iron. In terrestrial rocks, a natural alloy of iron and nickel is not found, so the presence of nickel in pieces of iron indicates its cosmic (or industrial!) origin.

Nickel iron inclusions are found in most stony meteorites, so space rocks are usually heavier than terrestrial ones. Their main minerals are silicates (olivines and pyroxenes). characteristic feature The main type of stone meteorites - chondrites - is the presence inside them of rounded formations - chondrules. Chondrules consist of the same substance as the rest of the meteorite, but stand out on its cut in the form of individual grains. Their origin is not yet completely clear.

The third class - stony-iron meteorites - these are pieces of nickel-plated iron interspersed with grains of stony minerals.

In general, meteorites consist of the same elements as terrestrial rocks, but combinations of these elements, i.e. minerals may be those that are not found on Earth. This is due to the peculiarities of the formation of bodies that gave rise to meteorites.

Among the falls, stony meteorites predominate. This means that there are more such pieces flying in space. As for the finds, iron meteorites predominate here: they are stronger, better preserved in terrestrial conditions, stand out more sharply against the background of terrestrial rocks.

Meteorites are not large iron, stone or iron-stone space objects that regularly fall on the surface of the planets of the solar system, including the Earth. Outwardly, they are not much different from stones or pieces of iron, but they are fraught with many mysteries from the history of the universe. Meteorites help scientists uncover the secrets of the evolution of celestial bodies and study processes that take place far beyond our planet.

Analyzing their chemical and mineral composition, one can trace the patterns and relationships between meteorites. various kinds. But each of them is unique, with qualities inherent only in this body of cosmic origin.

Types of meteorites by composition:

1. Stone:

Chondrites;

Achondrites.

2. Iron-stone:

Pallasites;

Mesosiderites.

3. Iron.

Octahedrites

Ataxites

4. Planetary

Martian

Origin of meteorites

Their structure is extremely complex and depends on many factors. By studying all known varieties of meteorites, scientists have come to the conclusion that they are all closely related at the genetic level. Even taking into account significant differences in structure, mineral and chemical composition, they are united by one thing - the origin. All of them are fragments of celestial bodies (asteroids and planets) moving in outer space at high speed.

Morphology

To reach the Earth's surface, a meteorite has to make a long journey through the layers of the atmosphere. As a result of a significant aerodynamic load and ablation (high-temperature atmospheric erosion), they acquire characteristic external features:

Oriented-conical shape;

Melting bark;

Special surface relief.

A distinctive feature of real meteorites is the melting crust. In color and structure, it can differ quite significantly (depending on the type of body of cosmic origin). In chondrites it is black and matte, in achondrites it is shiny. In rare cases, the melting crust may be light and translucent.

With a long stay on the surface of the Earth, the surface of the meteorite is destroyed under the influence of atmospheric influences and oxidation processes. For this reason, a significant part of the bodies of cosmic origin after a certain time practically does not differ in any way from pieces of iron or stones.

Another distinctive external feature that a real meteorite has is the presence of depressions on the surface, called piezoglypts or regmaglipts. Reminiscent of fingerprints on soft clay. Their size and structure depend on the conditions of meteorite movement in the atmosphere.

Specific gravity

1. Iron - 7.72. The value can vary in the range of 7.29-7.88.

2. Pallasites - 4.74.

3. Mesosiderites - 5.06.

4. Stone - 3.54. The value can vary in the range of 3.1-3.84.

Magnetic and optical properties

Due to the presence of a significant amount of nickel iron, a real meteorite exhibits its unique magnetic properties. This is used to verify the authenticity of a body of cosmic origin and allows indirect judgment of the mineral composition.

The optical properties of meteorites (color and reflectivity) are less pronounced. They appear only on the surfaces of fresh fractures, but over time, due to oxidation, they become less and less noticeable. Comparing the average values ​​of the brightness coefficient of meteorites with the albedo of the celestial bodies of the solar system, scientists came to the conclusion that some planets (Jupiter, Mars), their satellites, as well as asteroids are similar in their optical properties to meteorites.

The chemical composition of meteorites

Considering the asteroidal origin of meteorites, their chemical composition can differ significantly between objects of different types. This has a significant effect on the magnetic and optical properties, as well as the specific gravity of bodies of cosmic origin. The most common chemical elements in meteorites are:

1. Iron (Fe). It is the main chemical element. Occurs as nickel iron. Even in stony meteorites, the average Fe content is 15.5%.

2. Nickel (Ni). It is part of nickel iron, as well as minerals (carbides, phosphides, sulfides and chlorides). Compared to Fe, it occurs 10 times less frequently.

3. Cobalt (Co). V pure form not found. Compared to nickel, it is 10 times rarer.

4. Sulfur (S). It is part of the mineral troilite.

5. Silicon (Si). It is part of the silicates that form the bulk of stony meteorites.

3. Rhombic pyroxene. Often found in stony meteorites, among silicates - the second most common.

4. Monoclinic pyroxene. In meteorites, it is rare and in small quantities, with the exception of achondrites.

5. Plagioclase. A common rock-forming mineral that is part of the feldspar group. Its content in meteorites varies widely.

6. Glass. It is the main component of stone meteorites. Contained in chondrules, and also occurs as inclusions in minerals.

Meteors are particles of interplanetary material that pass through the Earth's atmosphere and are heated to incandescence by friction. These objects are called meteoroids and race through space, becoming meteors. In a few seconds, they cross the sky, creating luminous trails.

meteor showers
Scientists have calculated that 44 tons of meteoritic matter falls to Earth every day. A few meteors per hour can usually be seen on any given night. Sometimes the number increases dramatically - these phenomena are called meteor showers. Some occur annually or at regular intervals as the Earth passes through a trail of dusty debris left by a comet.

Leonid meteor shower

Meteor showers are usually named after the star or constellation closest to where the meteors appear in the sky. Perhaps the most famous are the Perseids, which appear on August 12 every year. Each Perseid meteor is a tiny piece of the Swift-Tuttle comet that takes 135 years to orbit the Sun.

Other meteor showers and related comets are the Leonids (Tempel-Tuttle), the Aquarids and Orionids (Halley), and the Taurids (Encke). Most of the comet dust in meteor showers burns up in the atmosphere before reaching the Earth's surface. Some of this dust is captured by aircraft and analyzed at NASA laboratories.

meteorites
Pieces of rock and metal from asteroids and other cosmic bodies that survive their journey through the atmosphere and fall to earth are called meteorites. Most meteorites found on Earth are pebbly, about the size of a fist, but some are larger than buildings. Once upon a time, the Earth experienced many serious meteor attacks that caused significant destruction.

One of the best-preserved craters is the Barringer meteorite crater in Arizona, about 1 km (0.6 miles) in diameter, formed by the fall of a piece of iron-nickel metal approximately 50 meters (164 feet) in diameter. It is 50,000 years old and so well preserved that it is used to study meteorite impacts. Since the site was recognized as such an impact crater in 1920, about 170 craters have been found on Earth.

Barringer Meteor Crater

A severe asteroid impact 65 million years ago that created the 300 kilometers wide (180 miles) Chicxulub crater in the Yucatán Peninsula contributed to the extinction of about 75 percent of the marine and land animals on Earth at that time, including dinosaurs.

There is little documented evidence of meteorite damage or death. In the first known case, an extraterrestrial object injured a person in the United States. Ann Hodges of Sylacauga, Alabama, was injured after a 3.6 kilogram (8 lb) stony meteorite hit the roof of her house in November 1954.

Meteorites may look like terrestrial rocks, but they usually have a burnt surface. This burnt crust is the result of a meteorite melting due to friction as it passes through the atmosphere. There are three main types of meteorites: silver, stony, and stony-silver. Although most of the meteorites that fall to Earth are stony, more meteorites are found in Lately- silver. These heavy objects are easier to distinguish from the rocks of the Earth than stony meteorites.

This meteorite image was taken by the Opportunity rover in September 2010.

Meteorites also fall on other bodies in the solar system. The Opportunity rover was exploring different types of meteorites on another planet when it discovered a basketball-sized iron-nickel meteorite on Mars in 2005, and then found a much larger and heavier iron-nickel meteorite in 2009 in the same area. In all, the Opportunity rover discovered six meteorites during its journey across Mars.

Sources of meteorites
Over 50,000 meteorites have been found on Earth. Of these, 99.8% came from the Asteroid Belt. Evidence for their origin from asteroids includes a meteorite impact orbit computed from photographic observations projected back onto the asteroid belt. An analysis of several classes of meteorites showed a coincidence with some classes of asteroids, and they also have an age of 4.5 to 4.6 billion years.

Researchers discover new meteorite in Antarctica

However, we can only match one group of meteorites to a particular type of asteroid - eucrite, diogenite and howardite. These igneous meteorites come from the third largest asteroid, Vesta. The asteroids and meteorites that fall to Earth are not parts of the planet that broke up, but are made up of the original materials from which the planets formed. The study of meteorites tells us about the conditions and processes during the formation and early history of the solar system, such as age and composition. solids, the nature of the organic matter, the temperatures reached on the surface and inside the asteroids, and the shape into which these materials were brought by the impact.

The remaining 0.2 percent of meteorites can be divided roughly equally between meteorites from Mars and the Moon. More than 60 known Martian meteorites have been ejected from Mars as a result of meteor showers. They are all igneous rocks that have crystallized from magma. The stones are very similar to those of the earth, with some hallmarks, which indicate a Martian origin. Nearly 80 lunar meteorites are similar in mineralogy and composition to moon rocks from the Apollo mission, but are different enough to show that they came from different parts of the moon. Research on lunar and Martian meteorites complements research on the rocks of the Moon by the Apollo mission and robotic exploration of Mars.

Types of meteorites
Quite often, an ordinary person, imagining what a meteorite looks like, thinks of iron. And it's easy to explain. Iron meteorites are dense, very heavy, and often take on unusual and even impressive shapes as they fall and melt in our planet's atmosphere. And although iron is associated with the typical composition of space rocks in most people, iron meteorites are one of the three main types of meteorites. And they are quite rare compared to stony meteorites, especially the most common group of them - single chondrites.

Three main types of meteorites
There are a large number of types of meteorites, divided into three main groups: iron, stone, stone-iron. Almost all meteorites contain extraterrestrial nickel and iron. Those that do not contain iron at all are so rare that even if we ask for help identifying possible space rocks, we will most likely not find anything that does not contain a large amount of metal. The classification of meteorites is, in fact, based on the amount of iron contained in the sample.

iron meteorites
Iron meteorites were part of the core of a long-dead planet or large asteroid that is thought to have formed the Asteroid Belt between Mars and Jupiter. They are the densest materials on Earth and are very strongly attracted to a strong magnet. Iron meteorites are much heavier than most of the Earth's rocks, if you've lifted a cannonball or a slab of iron or steel, you know what I'm talking about.

An example of an iron meteorite

In most samples of this group, the iron component is approximately 90% -95%, the rest is nickel and trace elements. Iron meteorites are divided into classes according to their chemical composition and structure. Structural classes are determined by examining two components of iron-nickel alloys: kamacite and taenite.

These alloys have a complex crystal structure known as the Widmanstetten structure, named after Count Alois von Widmanstetten, who described the phenomenon in the 19th century. This lattice-like structure is very beautiful and is clearly visible if the iron meteorite is cut into plates, polished and then etched in a weak solution of nitric acid. For kamacite crystals found in the process, the average band width is measured and the resulting figure is used to separate iron meteorites into structural classes. Iron with a thin band (less than 1 mm) is called "fine-structured octahedrite", with a wide band "coarse octahedrite".

stone meteorites
The largest group of meteorites are stony, they formed from the outer crust of a planet or an asteroid. Many stony meteorites, especially those that have been on the surface of our planet for a long time, are very similar to ordinary terrestrial stones, and it takes an experienced eye to find such a meteorite in the field. Recently fallen rocks have a black lustrous surface that was formed by the burning of the surface in flight, and the vast majority of rocks contain enough iron to be attracted to a powerful magnet.

A typical representative of chondrites

Some stony meteorites contain small, colorful, grain-like inclusions known as "chondrules". These tiny grains originated from the solar nebula, therefore, before the formation of our planet and the entire solar system, which makes them the oldest known matter available for study. Stony meteorites containing these chondrules are called "chondrites".

Space rocks without chondrules are called "achondrites". These are volcanic rocks, shaped by volcanic activity on their "parent" space objects, where melting and recrystallization have obliterated all traces of the ancient chondrules. Achondrites contain little or no iron, making it difficult to find compared to other meteorites, although specimens often have a glossy crust that looks like enamel paint.

Stone meteorites from the Moon and Mars
Can we really find lunar and Martian rocks on the surface of our own planet? The answer is yes, but they are extremely rare. More than one hundred thousand lunar and about thirty Martian meteorites have been found on Earth, and all of them belong to the achondrite group.

lunar meteorite

The collision of the surface of the Moon and Mars with other meteorites threw fragments into outer space and some of them fell to the ground. From a financial point of view, lunar and Martian samples are among the most expensive meteorites. In the collectors' markets, they cost up to a thousand dollars per gram, which makes them several times more expensive than if they were made of gold.

Stony-iron meteorites
The least common of the three main types, stony-iron, accounts for less than 2% of all known meteorites. They consist of approximately equal parts of iron-nickel and stone, and are divided into two classes: pallasite and mesosiderite. Stone-iron meteorites were formed at the border of the crust and mantle of their "parent" bodies.

An example of a stone-iron meteorite

Pallasites are perhaps the most enticing of all meteorites and are definitely of great interest to private collectors. Pallasite is composed of an iron-nickel matrix filled with olivine crystals. When olivine crystals are clear enough to appear emerald green, they are known as gem perodot. Pallasites got their name in honor of the German zoologist Peter Pallas, who described the Russian meteorite Krasnoyarsk, found near the capital of Siberia in the 18th century. When a pallasite crystal is cut into slabs and polished, it becomes translucent, giving it an ethereal beauty.

Mesosiderites are the smaller of the two stony-iron groups. They are composed of iron-nickel and silicates and are usually attractive. The high contrast of the silver and black matrix, when the plate is cut and sanded, and the occasional blotch, results in a very unusual look. The word mesosiderite comes from the Greek for "half" and "iron" and they are very rare. In thousands of official catalogs of meteorites, there are less than a hundred mesosiderites.

Classification of meteorites
Meteorite classification is a complex and technical subject and the above is only intended as a brief overview of the topic. Classification methods have changed several times over the years. last years; known meteorites were reclassified to another class.

martian meteorites
A Martian meteorite is a rare type of meteor that came from the planet Mars. Until November 2009, more than 24,000 meteors had been found on Earth, but only 34 of them were Martian. The Martian origin of meteors was known from the composition of isotopic gas, which is contained in meteors in microscopic quantities, the analysis of the Martian atmosphere was carried out by the Viking spacecraft.

The emergence of the Martian meteorite Nakhla
In 1911, the first Martian meteorite called Nakhla was found in the Egyptian desert. The appearance and belonging of the meteorite to Mars was established much later. And they established its age - 1.3 billion years. These stones appeared in space after large asteroids fell on Mars or during massive volcanic eruptions. The strength of the explosion was such that the thrown out pieces of rock acquired the speed necessary to overcome the gravity of the planet Mars and leave its orbit (5 km / s). In our time, up to 500 kg of Martian stones fall to Earth in one year.

Two parts of the Nakhla meteorite

In August 1996, an article was published in the journal Science about the study of the meteorite ALH 84001, found in Antarctica in 1984. started new job, centered around a meteorite found in a glacier in Antarctica. The study was carried out using a scanning electron microscope, they revealed "biogenic structures" inside the meteor, which theoretically could be formed by life on Mars.

The isotope date showed that the meteor appeared about 4.5 billion years ago, and having fallen into interplanetary space, fell to Earth 13 thousand years ago.

"Biogenic structures" found on a cut of a meteorite

While studying the meteor with an electron microscope, experts found microscopic fossils suggestive of bacterial colonies, consisting of individual parts with a volume of approximately 100 nm. Traces of preparations resulting from the decomposition of microorganisms were also found. Evidence of the origin of a Martian meteor requires microscopic examination and special chemical analyses. A specialist can testify to the Martian occurrence of a meteor in accordance with the presence of minerals, oxides, calcium phosphates, silicon and iron sulfide.

The known specimens are invaluable because they are typical time capsules from Mars' geologic past. We received these Martian meteorites without any space missions.

The largest meteorites that fell to Earth
From time to time, cosmic bodies fall to Earth ... more and not very much, made of stone or metal. Some of them are no more than a grain of sand, others weigh several hundred kilograms or even tons. Scientists from the Astrophysical Institute in Ottawa (Canada) claim that several hundred solid alien bodies with a total mass of more than 21 tons visit our planet every year. The weight of most meteorites does not exceed a few grams, but there are those that weigh several hundred kilograms or even tons.

The places where meteorites fall are either fenced off or vice versa open to the public so that everyone can touch the extraterrestrial "guest".

Some confuse comets and meteorites due to the fact that both of these celestial bodies have a fiery shell. In ancient times, people considered comets and meteorites a bad omen. People tried to avoid places where meteorites fell, considering them to be a cursed zone. Fortunately, in our time, such cases are no longer observed, and even vice versa - the places where meteorites fall are of great interest to the inhabitants of the planet.

Let's remember the 10 largest meteorites that fell on our planet.

A meteorite fell on our planet on April 22, 2012, the speed of the fireball was 29 km / s. Flew over the states of California and Nevada, the meteorite scattered its burning fragments for tens of kilometers and exploded in the sky over the US capital. The power of the explosion is relatively small - 4 kilotons (in TNT equivalent). For comparison, the explosion of the famous Chelyabinsk meteorite was 300 kilotons in TNT.

According to scientists, the Sutter Mill meteorite was formed at the time of the birth of our solar system, a cosmic body more than 4566.57 million years ago.

On February 11, 2012, hundreds of tiny meteorite stones flew over the territory of China and fell over an area of ​​over 100 km in the southern regions of China. The largest of them weighed about 12.6 kg. According to scientists, the meteorites came from the asteroid belt between Jupiter and Mars.

On September 15, 2007, a meteorite fell near Lake Titicaca (Peru) near the border with Bolivia. According to eyewitnesses, the event was preceded by a loud noise. Then they saw a falling body engulfed in flames. The meteorite left a bright trail in the sky and a plume of smoke, which was visible several hours after the fireball fell.

A huge crater 30 meters in diameter and 6 meters deep formed at the crash site. The meteorite contained toxic substances, as people living nearby started getting headaches.

Most often, meteorites made of stone (92% of the total), consisting of silicates, fall to Earth. The Chelyabinsk meteorite is an exception, it was iron.

The meteorite fell on June 20, 1998 near the Turkmen city of Kunya-Urgench, hence its name. before the fall locals saw a bright flash. The largest part of the car weighs 820 kg, this piece fell into the field and formed a funnel of 5 meters.

According to geologists, the age of this celestial body is about 4 billion years. The Kunya-Urgench meteorite is certified by the International Meteoritic Society and is considered the largest of all fireballs that fell on the territory of the CIS and third world countries.

Iron car Sterlitamak, whose weight was more than 300 kg, fell on May 17, 1990 on the field of the state farm west of the city of Sterlitamak. When a celestial body fell, a crater of 10 meters was formed.

Initially, small metal fragments were discovered, a year later, scientists managed to extract the largest fragment of a meteorite weighing 315 kg. Currently, the meteorite is in the Museum of Ethnography and Archeology of the Ufa Scientific Center.

This event took place in March 1976 in Jilin Province in eastern China. The largest meteor shower lasted more than half an hour. Space bodies fell at a speed of 12 km per second.

Only a few months later, about a hundred meteorites were found, the largest - Jilin (Girin), weighed 1.7 tons.

This meteorite fell on February 12, 1947 in the Far East in the city of Sikhote-Alin. The fireball was fragmented in the atmosphere into small iron pieces, which scattered over an area of ​​15 sq. km.

Several dozen craters 1-6 meters deep and 7 to 30 meters in diameter were formed. Geologists have collected several tens of tons of meteorite material.

Goba meteorite (1920)

Meet Goba - one of the largest meteorites ever found! It fell to Earth 80 thousand years ago, but was found in 1920. A real iron giant weighed about 66 tons and had a volume of 9 cubic meters. Who knows with what myths the people living at that time associated the fall of this meteorite.

composition of the meteorite. 80% of this celestial body consists of iron, it is considered the heaviest of all meteorites that have ever fallen on our planet. Scientists took samples, but did not transport the entire meteorite. Today it is at the crash site. This is one of the largest pieces of iron on Earth of extraterrestrial origin. The meteorite is constantly decreasing: erosion, vandalism and scientific research have done their job: the meteor has decreased by 10%.

A special fence was created around it, and now Goba is known to the whole planet, many tourists come to visit it.

The mystery of the Tunguska meteor (1908)

The most famous Russian meteorite. In the summer of 1908, a huge fire ball. The meteorite exploded at an altitude of 10 km above the taiga. The blast wave circled the Earth twice and was recorded by all observatories.

The power of the explosion is simply monstrous and is estimated at 50 megatons. Flight space giant hundreds of kilometers per second. Weight, according to various estimates, varies - from 100 thousand to one million tons!

Fortunately, no one was hurt in this. The meteorite exploded over the taiga. In nearby settlements the window was blown out by the blast.

Trees fell down as a result of the explosion. Forest areas of 2,000 sq. turned into rubble. The blast killed animals within a radius of more than 40 km. For several days, artifacts were observed over the territory of central Siberia - luminous clouds and the glow of the sky. According to scientists, this was caused by inert gases that were released at the moment the meteorite entered the Earth's atmosphere.

What was it? The meteorite would have left a huge crater at the site of impact, at least 500 meters deep. No expedition has been able to find anything like it...

The Tunguska meteor, on the one hand, is a well-studied phenomenon, on the other hand, one of the biggest mysteries. The celestial body exploded in the air, the pieces burned up in the atmosphere, and no remnants remained on Earth.

The working title "Tunguska meteorite" appeared because this is the simplest and most understandable explanation for a flying ball of fire that caused an explosion effect. The Tunguska meteorite was also called crashed alien ship, and a natural anomaly, and a gas explosion. What he was in reality - one can only guess and build hypotheses.

Meteor shower in the USA (1833)

On November 13, 1833, a meteor shower fell over the eastern territory of the United States. The duration of the meteor shower is 10 hours! During this time, about 240 thousand small and medium-sized meteorites fell on the surface of our planet. The meteor shower of 1833 is the most powerful of all known meteor showers.

Every day, dozens of meteor showers fly near our planet. About 50 potentially dangerous comets are known that can cross the Earth's orbit. The collision of our planet with small (not capable of inflicting great harm) by cosmic bodies occur once every 10-15 years. A special danger to our planet is the fall of an asteroid.

Chelyabinsk meteorite
Almost two years have passed since the people of South Urals became eyewitnesses of a cosmic cataclysm - the fall of the Chelyabinsk meteorite, which became the first modern history incident that caused significant damage to the local population.

The fall of the asteroid occurred in 2013, on February 15th. At first, it seemed to the people of South Urals that an “obscure object” had exploded, many saw strange lightning bolts illuminating the sky. This is the opinion of scientists who have studied this incident for a year.

meteorite data
A rather ordinary comet fell in the area near Chelyabinsk. Falls of space objects of precisely this nature occur once in a century. Although according to other sources, they happen repeatedly, on average up to 5 times in 100 years. According to scientists, comets about 10 meters in size fly into the atmosphere of our Earth approximately once a year, which is 2 times more than the Chelyabinsk meteorite, but this often happens over regions with a small population or over the oceans. At what comets burn down and collapse at a great height, without causing any damage.

The plume from the Chelyabinsk meteorite in the sky

Before the fall, the mass of the Chelyabinsk aerolite was from 7 to 13 thousand tons, and its parameters were presumably 19.8 m. At present, a little more than one ton has been collected from this amount, including one of the large fragments of aerolite weighing 654 kg., Lifted from the bottom of Chebarkul Lake.

The study of the Chelyabinsk mayorite according to geochemical indicators revealed that it belongs to the type of ordinary chondrites of the LL5 class. This is the most common subgroup of stony meteorites. All currently discovered meteorites, about 90%, are chondrites. They got their name due to the presence of chondrules in them - spherical melted formations with a diameter of 1 mm.

The indications of infrasound stations indicate that in the minute of strong deceleration of the Chelyabinsk aerolite, when about 90 km remained to the ground, a powerful explosion occurred with a force equal to the TNT equivalent of 470-570 kilotons, which is 20-30 times stronger than the atomic explosion in Hiroshima, however, in terms of explosive power it yields to the fall of the Tunguska meteorite (approximately from 10 to 50 megatons) by more than 10 times.

The fall of the Chelyabinsk meteorite immediately created a sensation both in time and place. In modern history, this space object is the first meteorite that fell into such a densely populated area, resulting in significant damage. So, during the explosion of a meteorite, the windows of more than 7 thousand houses were shattered, more than one and a half thousand people applied for medical care, of which 112 were hospitalized.

In addition to significant damage, the fall of the meteorite also brought positive results. This event is the best documented to date. In addition, one video camera filmed the phase of falling into Chebarkul Lake of one of the large fragments of the asteroid.

Where did the Chelyabinsk meteorite come from?
For scientists, this question was not difficult. It emerged from the main asteroid belt of our solar system, a zone in the middle of the orbits of Jupiter and Mars, where the paths of most small bodies lie. The orbits of some of them, for example, asteroids of the Aten or Apollo group, are oblong and can pass through the orbit of the Earth.

Astronomers were able to accurately determine the flight path of the Chelyabinsk, thanks to a lot of photo and video recordings, as well as satellite photographs that captured the fall. Then the astronomers continued the path of the meteorite to reverse side, for the atmosphere, in order to build a complete orbit of this object.

Dimensions of fragments of the Chelyabinsk meteorite

Several groups of astronomers have tried to determine the path of the Chelyabinsk meteorite before it hit the Earth. According to their calculations, it can be seen that the semi-major axis of the orbit of the fallen meteorite was approximately 1.76 AU. (astronomical unit), this is the average radius of the earth's orbit; the point of the orbit closest to the Sun - perihelion, was at a distance of 0.74 AU, and the point most distant from the Sun - aphelion, or apohelion, at 2.6 AU.

These figures allowed scientists to try to find the Chelyabinsk meteorite in astronomical catalogs of already identified small space objects. It is clear that most of the previously established asteroids after some time “fall out of sight” again, and then some of the “lost” ones manage to “open” for the second time. Astronomers did not reject this option either, that the fallen meteorite, perhaps, is the “loss”.

Relatives of the Chelyabinsk meteorite
Although the search did not reveal a complete similarity, astronomers nevertheless found a number of probable "relatives" of the asteroid from Chelyabinsk. Scientists from Spain Raul and Carlos de la Fluente Marcos, having calculated all the variations in the orbits of the "Chelyabinsk", sought out its alleged forefather - the asteroid 2011 EO40. In their opinion, the Chelyabinsk meteorite broke away from him about 20-40 thousand years.

Another team (Astronomical Institute of the Czech Academy of Sciences) led by Jiri Borovichka, having calculated the glide path of the Chelyabinsk meteorite, found that it is very similar to the orbit of asteroid 86039 (1999 NC43) with a size of 2.2 km. For example, the semi-major axis of the orbit of both objects is 1.72 and 1.75 AU, and the perihelion distance is 0.738 and 0.74.

Difficult life path
According to the fragments of the Chelyabinsk meteorite that fell to the surface of the earth, scientists "determined" its life history. It turns out that the Chelyabinsk meteorite is a peer of our solar system. When studying the proportions of isotopes of uranium and lead, it turned out that it is approximately 4.45 billion years old.

Fragment of the Chelyabinsk meteorite found on the lake Chebarkul

His difficult biography is indicated by dark threads in the thickness of the meteorite. They arose during the melting of substances that got inside as a result of a strong blow. This shows that approximately 290 million years ago, this asteroid withstood a powerful collision with some kind of cosmic object.

According to the scientists of the Institute of Geochemistry and Analytical Chemistry. Vernadsky RAN, the collision took about a few minutes. This is indicated by the streaks of iron nuclei, which did not have time to fully melt.

At the same time, scientists from the IGM SB RAS (Institute of Geology and Mineralogy) do not reject the fact that traces of melting may have appeared due to the excessive approach of the cosmic body to the Sun.

meteor showers
Several times a year, meteor showers illuminate the clear night sky like stars. But they really have nothing to do with the stars. These small cosmic particles of meteorites are literally celestial debris.

Meteoroid, meteor or meteorite?
Whenever a meteoroid enters the Earth's atmosphere, it generates a burst of light called a meteor or "shooting star". The high temperatures caused by the friction between the meteor and the gas in Earth's atmosphere heats the meteorite to the point where it glows. This is the same glow that makes the meteor visible from the surface of the Earth.

Meteors usually glow for a very short period of time - they tend to burn up completely before hitting the Earth's surface. If the meteor does not break up as it passes through the Earth's atmosphere and falls to the surface, then it is known as a meteorite. Meteorites are believed to come from the Asteroid Belt, although some pieces of debris have been identified as belonging to the Moon and Mars.

What are meteor showers?
Sometimes meteors fall in huge showers known as meteor showers. Meteor showers occur when a comet approaches the Sun and leaves debris behind it in the form of breadcrumbs. When the orbit of the Earth and comets intersect, Earth falls meteor shower.

So the meteors that form a meteor shower travel on a parallel path and at the same speed, so for observers they come from the same point in the sky. This point is known as the "radiant". By convention, meteor showers, especially regular ones, are named after the constellation they come from.

What are the chemical composition of meteorites? and got the best answer

Answer from Tata[guru]
Chemical composition.
The chemical composition of asteroids is similar to the chemical composition of meteorites, so the description of the composition of meteorites is fully applicable to asteroids. Comets, on the other hand, have a more complex composition, as they consist of several parts (core, head and tail) consisting of various chemical elements.
We can judge the chemical composition of meteorites by the composition of those meteorites that fell into the hands of scientists. To date, they are usually divided into three classes: stone, stone-metal and metal. Asteroids are much larger in size than meteorites, and so far their structure can only be assumed from their reflectivity. There are three groups of asteroids - dark, light and metallic.
The table below gives only average values ​​for the content of individual chemical elements in meteorites of different classes. It follows from the above that there are only three classes of meteorites and asteroids, but this is not entirely true. The classes of meteorites are divided into big number subclasses, that is, the chemical composition of meteorites within each class varies widely.
Consider metallic meteorites. The main chemical elements, the content of which determines the type of meteorite, are iron and nickel. Therefore, depending on the nickel content, meteorites are subdivided into hexahedrites, octahedrites and ataxites. But even within these subclasses, meteorites differ in nickel content. Ataxites, depending on the nickel content, are divided into rich and poor in nickel.
The average chemical composition of nickel iron, which forms inclusions in stony meteorites and mesosiderites, and also forms the basis of pallastites, is generally close to the average composition of fine and very fine structure octahedrites.
The distribution of chemical elements in meteorites obeys the same pattern as on Earth, that is, the Oddo-Harkins law. According to this law, an element with an even ordinal number is more common than its neighboring elements with odd ordinal numbers.
An interesting feature of the content of rare impurities in meteorites was also established. It turned out that the amount of these impurities contained in meteorites in millionths of a percent depends on the chemical composition of the meteorite, in particular, on the nickel content. Thus, the maximum content of gallium is observed in hexahedrites, nickel-poor ataxites and octahedrites, and the minimum content is observed in nickel-poor ataxites. In other words, the higher the nickel content in a meteorite, the less gallium it contains.
Meteorites also contain a number of gases as their constituents. Hydrogen, nitrogen, carbon monoxide and carbon dioxide have been isolated from various meteorites. It was also found that hydrogen and carbon monoxide predominate in metallic meteorites, while carbon dioxide predominates in stone meteorites. Also in meteorites there are some radioactive elements, in particular: uranium, helium, potassium, thorium. This allows, by measuring the amount of radioactive elements and their decay products, to determine the age of meteorites. (Age here refers to the period of time that has elapsed since the moment of solidification of the substance that makes up meteorites.
metal meteorites.
Hexahedrites are entirely composed of one mineral type of iron - kamacite. Accessory minerals are represented by troilite and schreibersite; Dobreelite occurs as an occasional mineral.
Octahedrites are composed of both mineral types of nickel iron, that is, kamacite (ground mass) and taenite. The largest amount of taenite is contained in very fine-grained octahedrites, while the content of taenite in coarse-grained octahedrites is very low. Very rare are octahedrites, such as Sikhote-Alin, almost entirely composed of kamacite.
ATAXITES consist entirely of a mixture of grains of kamacite and taenite, called plessite. Thus, in its own way mineral composition ataxites are similar to octahedrites, differing from