Chemical composition of meteorites and their classification. What is a meteorite - is it really a shooting star?

> Types of meteorites

Find out which ones exist types of meteorites: description of classification with photos, iron, stone and stone-iron, meteorites from the Moon and Mars, asteroid belt.

Quite often, an ordinary person, imagining what a meteorite looks like, thinks about iron. And it's easy to explain. Iron meteorites are dense, very heavy, and often take on unusual, and even spectacular, shapes as they fall and melt through our planet's atmosphere. And although most people associate iron with the typical composition of space rocks, 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

Exists 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 contain no iron at all are so rare that even if we asked for help identifying possible space rocks, we likely wouldn't find anything that didn't contain large amounts of the metal. The classification of meteorites is, in fact, based on the amount of iron contained in the sample.

Iron type meteorite

Iron meteoriteswere part of the core of a long-dead planet or large asteroid from which it is believed to have formed between Mars and Jupiter. They are the densest materials on Earth and are very strongly attracted to strong magnet. Iron meteorites are much heavier than most Earth rocks; if you've lifted a cannonball or a slab of iron or steel, you know what we're talking about.

For most samples in this group, the iron component is approximately 90%-95%, the rest is nickel and trace elements. Iron meteorites are divided into classes based on chemical composition and structure. Structural classes are determined by studying two components of iron-nickel alloys: kamacite and taenite.

These alloys have a complex crystalline structure known as the Widmanstätten structure, named after Count Alois von Widmanstätten who described the phenomenon in the 19th century. This lattice-like structure is very beautiful and clearly visible if the iron meteorite is cut into plates, polished and then etched in a weak solution nitric acid. In kamacite crystals discovered during this process, the average width of the bands is measured, and the resulting figure is used to divide iron meteorites into structural classes. Iron with a fine stripe (less than 1 mm) is called “fine-structured octahedrite”, with a wide stripe “coarse octahedrite”.

Stone view of meteorite

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

Some stony meteorites contain small, colorful, grain-like inclusions known as "chondrules." These tiny grains originated from the solar nebula, therefore predating the formation of our planet and the entire Solar System, making 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 formed by volcanic activity on their “parent” space objects, where melting and recrystallization erased all traces of ancient chondrules. Achondrites contain little or no iron, making it more difficult to find than other meteorites, although specimens are often coated with a glossy crust that looks like enamel paint.

Stone view of meteorite from the Moon and Mars

Can we really find Moon 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 approximately thirty Martian meteorites have been discovered on Earth, all of which belong to the achondrite group.

The collision of the surface of the Moon and Mars with other meteorites threw fragments into outer space and some of them fell to Earth. From a financial point of view, lunar and Martian samples are among the most expensive meteorites. In collector's markets, their price reaches thousands of dollars per gram, making them several times more expensive than if they were made of gold.

Stone-iron type of meteorite

The least common of the three main types - stone-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. Stony-iron meteorites formed at the boundary of the crust and mantle of their “parent” bodies.

Pallasites are perhaps the most alluring of all meteorites and are definitely of great interest to private collectors. Pallasite consists of an iron-nickel matrix filled with olivine crystals. When olivine crystals are pure enough to display an emerald green color, they are known as gem perodot. Pallasites got their name in honor of the German zoologist Peter Pallas, who described the Russian Krasnoyarsk meteorite, 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 lithic-iron groups. They are composed of iron-nickel and silicates, and are usually attractive in appearance. The high contrast of the silver and black matrix, if the plate is cut and sanded, and random inclusions, leads to very unusual looking. 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 meteorite types

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

METEORITE
a piece of extraterrestrial matter that fell to the surface of the Earth; Literally - "stone from the sky." Meteorites are the oldest known minerals (4.5 billion years old), so they should preserve traces of the processes that accompanied the formation of the planets. Until samples of lunar soil were brought to Earth, meteorites remained the only samples of extraterrestrial matter. Geologists, chemists, physicists and metallurgists have been collecting and studying meteorites for more than 200 years. From these studies the science of meteorites emerged. Although the first reports of meteorite falls appeared a long time ago, scientists were very skeptical about them. Various facts led them to finally believe in the existence of meteorites. In 1800-1803 several famous European chemists reported that chemical composition"meteor rocks" from different places fall is similar, but different from the composition of earthly rocks. Finally, when in 1803 a terrible “rain of stones” broke out in Aigle (France), littering the ground with fragments and witnessed by many excited eyewitnesses, the French Academy of Sciences was forced to agree that these were indeed “stones from the sky.” It is now believed that meteorites are fragments of asteroids and comets. Meteorites are divided into “fallen” and “found”. If a person saw a meteorite fall through the atmosphere and then actually found it on the ground (a rare event), then such a meteorite is called a "fallen". If it was found by chance and identified, which is typical for iron meteorites, then it is called “found.” Meteorites are named after the places where they were found. In some cases, not one, but several fragments are found. For example, after the 1912 meteor shower in Holbrook (Arizona), more than 20 thousand fragments were collected.
Meteorite fall. Until a meteorite reaches the Earth, it is called a meteoroid. Meteoroids fly into the atmosphere at speeds from 11 to 30 km/s. At an altitude of about 100 km, due to friction with the air, the meteoroid begins to heat up; its surface becomes hot, and a layer several millimeters thick melts and evaporates. At this time it is visible as a bright meteor (see METEOR). The molten and evaporated substance is continuously carried away by air pressure - this is called ablation. Sometimes, under the pressure of air, a meteor is crushed into many fragments. Passing through the atmosphere, it loses from 10 to 90% of its initial mass. However, the interior of the meteor usually remains cold, since it does not have time to warm up during the 10 seconds that the fall lasts. Overcoming air resistance, small meteorites significantly reduce their flight speed by the time they hit the ground and usually go deeper into the ground by no more than a meter, and sometimes they simply remain on the surface. Large meteorites are slowed down only slightly and upon impact produce an explosion with the formation of a crater, such as in Arizona or on the Moon. The largest meteorite found is the iron meteorite Goba (South Africa), whose weight is estimated at 60 tons. It was never moved from the place where it was found. Every year, several meteorites are picked up immediately after their observed fall. In addition, more and more old meteorites are being discovered. In two places in the east of the state. In New Mexico, where the wind constantly blows away the soil, 90 meteorites were found. Hundreds of meteorites have been discovered on the surface of evaporating glaciers in Antarctica. Recently fallen meteorites are covered with a vitrified, sintered crust that is darker than the interior. Meteorites are of great scientific interest; Most major natural science museums and many universities have meteorite experts.

Types of meteorites. There are meteorites made of various substances. Some are primarily composed of an iron-nickel alloy containing up to 40% nickel. Among fallen meteorites only 5.7% are iron, but in collections their share is much larger, since they are destroyed more slowly under the influence of water and wind, and they are also easier to detect by appearance. If you polish a section of an iron meteorite and lightly etch it with acid, you can often see a crystalline pattern of intersecting stripes formed by alloys with different nickel contents. This drawing is called “Widmanstätten figures” in honor of A. Widmanstätten (1754-1849), who was the first to observe them in 1808.

Stony meteorites are divided into two large groups: chondrites and achondrites. Chondrites are the most common, accounting for 84.8% of all fallen meteorites. They contain rounded millimeter-sized grains - chondrules; Some meteorites are composed almost entirely of chondrules. Chondrules have not been found in terrestrial rocks, but glassy grains of similar size have been found in lunar soil. Chemists have studied them carefully because the chemistry of chondrules likely represents primordial material solar system. This standard composition is called the "cosmic abundance of elements." In chondrites of a certain type, containing up to 3% carbon and 20% water, signs of biological matter were intensively searched, but no signs of living organisms were found in either these or other meteorites. Achondrites lack chondrules and resemble lunar rock in appearance.

Parent bodies of meteorites. The study of the mineralogical, chemical and isotopic composition of meteorites has shown that they are fragments of larger objects in the Solar System. The maximum radius of these parent bodies is estimated at 200 km. The largest asteroids are approximately this size. The estimate is based on the cooling rate of the iron meteorite, at which two alloys with nickel are obtained, forming Widmanstätten figures. Rocky meteorites were likely dislodged from the surface of small, atmosphereless, cratered planets like the Moon. Cosmic radiation destroyed the surface of these meteorites in the same way as moon rocks. However, the chemical composition of meteorites and lunar samples is so different that it is quite obvious that the meteorites did not come from the Moon. Scientists were able to photograph two meteorites as they fell and calculate their orbits from the photographs: it turned out that these bodies came from the asteroid belt. Asteroids are likely the main sources of meteorites, although some may be particles from evaporated comets.
LITERATURE
Simonenko A.N. Meteorites are fragments of asteroids. M., 1979

Collier's Encyclopedia. - Open Society. 2000 .

Synonyms:

See what "METEORITE" is in other dictionaries:

Willamette ... Wikipedia

Aerolit, meteor, meteoroid, (alien, outsider, wanderer, stone, messenger, guest) (celestial, stellar, cosmic, universe, from space) Dictionary of Russian synonyms. meteorite noun, number of synonyms: 31 angrit (1) ... Synonym dictionary

meteorite- a, m. météorite f. gr. Aerolite, stone meteorite, fireball. Poppy. 1908. A body of cosmic origin that fell to the surface of the Earth from interplanetary space. BAS 1. Before us lie real meteorites: blocks weighing tens of tons, black,... ... Historical Dictionary of Gallicisms of the Russian Language

METEORITE, part of a large meteoric body (solid particle moving in interplanetary space), which, having passed through earth's atmosphere, reaches the Earth. Most meteoroids burn up in the atmosphere, creating METEORS, but about 10%... ... Scientific and technical encyclopedic dictionary

METEORITE, meteorite, husband. (see meteor) (astro.). A metal or rock mass falling from outer space. Dictionary Ushakova. D.N. Ushakov. 1935 1940 … Ushakov's Explanatory Dictionary

METEORITE, huh, husband. A metal or rocky body falling to Earth from interplanetary space.M. ghost (consisting of ice and gas). | adj. meteoric, oh, oh and meteoric, oh, oh. Ozhegov's explanatory dictionary. S.I. Ozhegov, N.Yu. Shvedova... ... Ozhegov's Explanatory Dictionary

meteorite- meteorite. Incorrect pronunciation [meteorite]... Dictionary of difficulties of pronunciation and stress in modern Russian language

meteorite- A meteoroid that reached the surface of the Earth. [GOST 25645.112 84] Topics meteorite substance EN meteorite DE Meteorit FR metéorite ... Technical Translator's Guide

, meteoroid, asteroid, their fragments, or other meteoroids.

A celestial body flying through the Earth's atmosphere and leaving a bright luminous trail in it, regardless of whether it flies into upper layers atmosphere and goes back into outer space, either burns up in the atmosphere or falls to Earth, can be called either a meteor or a fireball. Meteors are considered bodies no brighter than 4th magnitude, and fireballs - brighter than 4th magnitude, or bodies whose angular dimensions are distinguishable.

A solid body of cosmic origin that fell to the surface of the Earth is called a meteorite.

A crater (astrobleme) may form at the site where a large meteorite falls. One of the most famous craters in the world is Arizona. It is assumed that the largest meteorite crater on Earth is Wilkes Earth Crater (diameter about 500 km).

Other names for meteorites: aerolites, siderolites, uranolites, meteorolites, baituloi, sky, air, atmospheric or meteor stones, etc.

Phenomena similar to the fall of a meteorite on other planets and celestial bodies usually referred to simply as collisions between celestial bodies.

The process of meteorites falling to Earth

The meteor body enters the Earth's atmosphere at a speed of about 11-25 km/sec. At this speed, it begins to warm up and glow. Due to ablation (burning and blowing away by the oncoming flow of particles of the meteoroid body), the mass of the body that reaches the ground may be less, and in some cases significantly less than its mass at the entrance to the atmosphere. For example, a body that enters the Earth's atmosphere at a speed of 25 km/s or more burns up almost completely. At such a speed of entry into the atmosphere, out of tens and hundreds of tons of initial mass, only a few kilograms or even grams of matter reach the ground. Traces of the combustion of a meteoroid in the atmosphere can be found along almost the entire trajectory of its fall.

If the meteor body does not burn up in the atmosphere, then as it slows down it loses the horizontal component of its speed. This results in a change in the trajectory of the fall from often almost horizontal at the beginning to almost vertical at the end. As it slows down, the glow of the meteorite decreases and it cools down (they often indicate that the meteorite was warm and not hot when it fell).

In addition, the meteor body may break into fragments, resulting in a Meteor Shower.

Classification of meteorites

Classification by composition

stone
- chondrites
  - carbonaceous chondrites
  - ordinary chondrites
  - enstatite chondrites
iron-stone
- palasites
- mesosiderites
iron

The most common meteorites are stony meteorites (92.8% of falls). They consist mainly of silicates: olivines (Fe, Mg)2SiO4 (from fayalite Fe2SiO4 to forsterite Mg2SiO4) and pyroxenes (Fe, Mg)SiO3 (from ferrosilite FeSiO3 to enstatite MgSiO3).

The vast majority of stony meteorites (92.3% of stony meteorites, 85.7% of total falls) are chondrites. They are called chondrites because they contain chondrules - predominantly spherical or elliptical formations silicate composition. Most chondrules are no more than 1 mm in diameter, but some can reach several millimeters. Chondrules are found in a detrital or finely crystalline matrix, and often the matrix differs from chondrules not so much in composition as in crystalline structure. The composition of chondrites almost completely replicates the chemical composition of the Sun, with the exception of light gases such as hydrogen and helium. Therefore, it is believed that chondrites formed directly from the protoplanetary cloud that surrounded and surrounded the Sun, through the condensation of matter and the accretion of dust with intermediate heating.

Achondrites make up 7.3% of stony meteorites. These are fragments of protoplanetary (and planetary?) bodies that have undergone melting and differentiation by composition (into metals and silicates).

Iron meteorites are composed of an iron-nickel alloy. They account for 5.7% of falls.

Iron silicate meteorites have a composition intermediate between stony and iron meteorites. They are relatively rare (1.5% incidence).

Achondrites, iron and iron-silicate meteorites are classified as differentiated meteorites. They presumably consist of matter that has undergone differentiation as part of asteroids or other planetary bodies. Previously, it was believed that all differentiated meteorites were formed as a result of the rupture of one or more large bodies, for example the planet Phaethon. However, an analysis of the composition of different meteorites showed that they were more likely formed from the debris of many large asteroids.

Classification by detection method

falls (when a meteorite is found after observing its fall in the atmosphere);
finds (when the meteorite origin of the material is determined only by analysis);

Traces of extraterrestrial organics in meteorites

Coal complex

Carbonaceous (carbonaceous) meteorites have one important feature- the presence of a thin glassy cortex, apparently formed under the influence high temperatures. This crust is a good heat insulator, thanks to which minerals that cannot withstand strong heat, such as gypsum, are preserved inside carbonaceous meteorites. Thus, it became possible during the study chemical nature similar meteorites to detect in their composition substances that, under modern earthly conditions, are organic compounds, having a biogenic nature ( Source: Rutten M. Origin of life (naturally). - M., Publishing House "Mir", 1973) :

Saturated hydrocarbons
- - Isoprenoids
  - n-Alkanes
  - Cycloalkanes

Aromatic hydrocarbons
- - Naphthalene
  - Alkybenzenes
  - Acenaphthenes
  - Pyrene

Carboxylic acids
- - Fatty acid
  - Benzenecarboxylic acids
  - Hydroxybenzoic acids

Nitrogen compounds
- - Pyrimidines
  - Purines
  - Guanylurea
  - Triazines
  - Porphyrins

The presence of such substances does not allow us to unambiguously declare the existence of life outside the Earth, since theoretically, if certain conditions were met, they could be synthesized abiogenically.

On the other hand, if the substances found in meteorites are not products of life, then they may be products of pre-life - similar to that one, which once existed on Earth.

"Organized Elements"

When studying stony meteorites, so-called “organized elements” are discovered - microscopic (5-50 microns) “single-cell” formations, often having clearly defined double walls, pores, spines, etc. ( Source: Same)

It is not an indisputable fact that these fossils are the remains of some form of extraterrestrial life. But, on the other hand, these formations have such high degree organization that is usually associated with life ( Source: Same).

In addition, such forms have not been found on Earth.

A feature of “organized elements” is also their large number: per 1g. The substances of the carbonaceous meteorite account for approximately 1800 “organized elements”.

Large modern meteorites in Russia

Tunguska phenomenon (at this moment It is unclear exactly the meteorite origin of the Tunguska phenomenon. For details, see the article Tunguska meteorite). Fell on June 30 this year in the Podkamennaya Tunguska river basin in Siberia. The total energy is estimated at 15−40 megatons of TNT equivalent.
Tsarevsky meteorite (meteor shower). Fell on December 6 near the village of Tsarev, Volgograd region. This is a rock meteorite. The total mass of the collected fragments is 1.6 tons over an area of about 15 square meters. km. The weight of the largest fallen fragment was 284 kg.
Sikhote-Alin meteorite (total mass of fragments is 30 tons, energy is estimated at 20 kilotons). It was an iron meteorite. Fell in the Ussuri taiga on February 12.
Vitimsky car. Fell in the area of the villages of Mama and Vitimsky, Mamsko-Chuysky district, Irkutsk region, on the night of September 24-25. The event had a great public resonance, although total energy The meteorite explosion is apparently relatively small (200 tons of TNT equivalent, with an initial energy of 2.3 kilotons), the maximum initial mass (before combustion in the atmosphere) is 160 tons, and the final mass of the fragments is on the order of several hundred kilograms.

The discovery of a meteorite is quite a rare event. The Meteoritics Laboratory reports: “In total, only 125 meteorites have been found on the territory of the Russian Federation over 250 years.”

The only documented case of a meteorite hitting a person occurred on November 30 in Alabama. The meteorite, weighing about 4 kg, crashed through the roof of the house and ricocheted Anna Elizabeth Hodges on the arm and thigh. The woman received bruises.

Other Interesting Facts about meteorites:

Individual meteorites

Channing
Chainpur
Beeler
Arcadia
Arapahoe