How many groups are meteorites divided into? Origin of meteorites. Iron type meteorite

Meteorite is a solid extraterrestrial substance that was preserved during its passage through the atmosphere and reached the surface of the Earth. Meteorites are the most primitive substance of the SS, which has not experienced further fractionation since its formation. This is based on the fact that the relative distribution refractory el. in meteorites corresponds to solar distribution. Meteorites are divided into (based on metal phase content): Stone(aerolites): achondrites, chondrites, Iron-stone(siderolites), Iron(Siderites). Iron meteorites – consist of kamacite - native Fe cosmic origin with an admixture of nickel from 6 to 9%. Stone-iron meteorites Low spread group. They have coarse-grained structures with equal weight fractions of silicate and Fe phases. (Silicate minerals - Ol, Px; Fe phase - kamacite with Widmanstätten growths). Stone meteorites – consist of Mg and Fe silicates with an admixture of metals. Divided into Chondrite, achondrite and carbonaceous.Chondrites: spheroidal segregations of a few mm or less in size, composed of silicates, less often silicate glass. Immersed in a Fe-rich matrix. The main mass of chondrites is a fine-grained mixture of Ol, Px-s (Ol-bronzite, Ol-hypersthene and Ol-pigeonite) with nickel Fe (Ni-4-7%), troilite (FeS) and plagioclase. Chondrites are crystalline. or glassy drops, cat. Image. by melting pre-existing silicate material that has been subjected to heat. Achondrites: They do not contain chondrules and have a lower content. nickel Fe and coarser structures. Their main minerals are Px and Pl, some types are enriched in Ol. In composition and structural features, achondrites are similar to terrestrial Gabbroids. The composition and structure indicate igneous origin. Sometimes bubble structures like lavas are observed. Carbonaceous chondrites (large amounts of carbonaceous matter) A characteristic feature of carbonaceous chondrites is presence of a volatile component, which indicates primitiveness (volatile elements were not removed) and did not undergo fractionation. Type C1 contains a large number chlorite(aqueous Mg, Fe aluminosilicates), as well as magnetite, water-soluble salt, nativeS, dolomite, olivine, graphite, organ. connections. Those. from the moment of their image, they are beings. at T, not > 300 0 C. In the composition chondritic meteorites lack of 1/3 chemical Email compared to composition carbonaceous chondrites, cat. are closest to the composition of protoplanetary matter. The most likely cause of the shortage of volatile electricity. - sequential condensation of electricity. and their compounds in the reverse order of their volatility.

5.Historical and modern models of accretion and differentiation of protoplanetary matter O.Yu. Schmidt in the 40s expressed the idea that the Earth and the 3G planets were not formed from hot clumps solar gases, but by accumulating TV. bodies and particles - planetesimals that experienced melting later during accretion (heating due to collisions of large planetesimals, up to a few hundred km in diameter). Those. early core-mantle differentiation and degassing. Noun relates two points of view. the mechanism of accumulation and ideas about the form of the layered structure of planets. Models homogeneous and heterogeneous accretion: HETEROGENEOUS ACCRETION 1. Short-term accretion. Early heterogeneous accretion models(Turekian, Vinogradov) assumed that the earth was accumulated from material as it condensed from a protoplanetary cloud. Early models include early >T accumulation of the Fe-Ni alloy, forming the protocore of the earth, followed by lower. T by accretion of its outer parts from silicates. It is now believed that continuous change occurs during the accretion process. in the accumulating material, the Fe/silicate ratio from the center to the periphery of the forming planet. During accumulation, gold heats up, => melting of Fe, which is separated from silicates and sinks into the core. After the planet cools, about 20% of its mass is added by material enriched in volatiles along the periphery. In the proto-earth there were no sharp boundaries between the core and the mantle, cat. established as a result of gravitational and chem. differentiation at the next stage of the planet's evolution. In early versions, differentiation occurred mainly during the formation of the Earth's Earth, and did not cover the entire Earth. HOMOGENEOUS ACCRETION 2. A longer accretion time is accepted - 10 8 years. During the accretion of the Earth and the planets of the Earth, the condensing bodies had wide variations in composition from carbonaceous chondrites enriched in volatiles to materials enriched in refractory components of the Allende type. Planets of forms. from this set of meteorite objects and their differences and similarities were determined by reference. proportions of ingredients of different composition. The same happened macroscopic homogeneity of protoplanets. The existence of a massive core suggests that the alloy initially brought by Fe-Ni meteorites, uniformly distributed throughout the entire planet, was released into the central part during its evolution. Homogeneous in composition the planet split into shells in the process of gravitational differentiation and chemical processes. Modern model of heterogeneous accretion, allowing us to explain the chemistry. the composition of the mantle is being developed by a group of German scientists (Wencke, Dreybus, Jagoutz). They found that the contents of moderately volatile (Na, K, Rb) and moderately siderophilic (Ni, Co) elements in the mantle, with different The distribution coefficients Me/silicate have the same abundance (normalized by C1) in the mantle, and the most strongly siderophile elements have excess concentrations. Those. the core was not in equilibrium with the mantle reservoir. They proposed heterogeneous accretion :1. Accretion begins with the accumulation of a highly reduced component A, devoid of volatile elements. and containing all other emails. in quantities corresponding to C1, and Fe and all siderophiles in a reduced state. As T increases, core formation begins simultaneously with accretion. 2. After accretion, more and more oxidized material, component B, begins to accumulate in 2/3 of the earth’s mass. Part of the Me component of component A is still preserved and contributes to the extraction of the most siderophilic elements. and transfer them to the nucleus. Source of moderately volatile, volatile and moderately siderophilic el. in the mantle component B, which explains their close relative prevalence. Thus, the Earth consists of 85% component A and 15% B. In general, the composition of the mantle is formed after the separation of the core by homogenization and mixing of the silicate part of component A and the substance of component B.

6. Isotopes chemical elements. Isotopes - atoms of the same electron, but having a different number of neutrons N. They differ only in mass. Isotones - atoms of different elements, having different Z, but the same N. They are located in vertical rows. Isobars - atoms of different elements, cat. equal mass. numbers (A=A), but different Z and N. They are located in diagonal rows. Nuclear stability and isotope abundance; radionuclides The number of known nuclides is ~ 1700, of which ~ 260 are stable. On the nuclide diagram, stable isotopes (shaded squares) form a band surrounded by unstable nuclides. Only nuclides with a certain ratio of Z and N are stable. The ratio of N to Z increases from 1 to ~ 3 with increasing A. 1. Nuclides that have a cat are stable. N and Z are approximately equal. To Ca in N=Z nuclei. 2. Most stable nuclides have even Z and N. 3. Stable nuclides with even numbers are less common. Z and odd. N or even N and odd. Z. 4. P stable nuclides with odd Z and N are rare.

			number of stable nuclides
odd		odd
odd	odd
	odd	odd

In kernels with even Z and N nucleons form an ordered structure, which determines their stability. The number of isotopes is smaller in light el. and took him away. in the middle part of the PS, reaching a maximum at Sn (Z=50), which has 10 stable isotopes. Elements with odd. Z stable isotopes no more than 2.

7. Radioactivity and its types Radioactivity - spontaneous transformations of the nuclei of unstable atoms (radionuclides) into stable nuclei of other elements, accompanied by the emission of particles and/or energy radiation. The state of rad does not depend on the chemical. The properties of atoms are determined by the structure of their nuclei. Radioactive decay is accompanied by change. Z and N of the parent atom and leads to the transformation of an atom of one el. into the atom of another el. Also, Rutherford and other scientists have shown that he is glad. the decay is accompanied by the emission of radiation of three different types, a, b, g. a - rays - streams of high-speed particles - He nuclei, b - rays - streams e - , g - rays - electromagnetic waves with high energy and with a shorter λ. Types of radioactivity a-decay- decay by emission of a-particles, it is possible for nuclides with Z> 58 (Ce), and for a group of nuclides with small Z, including 5He, 5Li, 6Be. the a-particle consists of 2 P and 2N, a shift occurs by 2 positions in Z. The original isotope is called parental or maternal, and the newly formed - subsidiaries.

b-decay- has three types: regular b-decay, positronic b-decay and e – capture. Ordinary b-decay- can be considered as the transformation of a neutron into a proton and e - the latter or beta particle - is ejected from the nucleus, accompanied by the emission of energy in the form of g-radiation. The daughter nuclide is an isobar of the parent, but its charge is greater.

There is a series of decays until a stable nuclide is formed. Example: 19 K40 -> 20 Ca40 b - v- Q. Positron b-decay- emission of a positive positron particle b from the nucleus, its formation - the transformation of a nuclear proton into a neutron, positron and neutrino. The daughter nuclide is isobaric but has less charge.

Example, 9 F18 -> 8 O18 b v Q Atoms with excess N and located to the right of the zone nuclear stability, are b - -radioactive, because in this case, the number N decreases. Atoms to the left of the region of nuclear stability are neutron-deficient, they experience positron decay and their number N increases. Thus, during b- and b-decays there is a tendency for Z and N to change, leading to the daughter nuclides approaching the zone of nuclear stability. e – capture- capture of one of the orbital electrons. There is a high probability of capture from the K-shell, cat. closest to the core. e – capture causes emission of neutrinos from the nucleus. Daughter nuclide yavl. isobaric, and occupies the same position relative to the parent as during positron decay. There is no b - radiation, and when a vacancy in the K shell is filled, X rays are released. At g-radiation neither Z nor A change; when the nucleus returns to its normal state, energy is released in the form g-radiation. Some daughter nuclides of natural isotopes U and Th can decay either by emitting b particles or by a decay. If b-decay occurred first, then a-decay occurred, and vice versa. In other words, these two alternative types of decay form closed cycles and always lead to the same end product - stable isotopes Pb.

8. Geochemical consequences of radioactivity of terrestrial matter. Lord Kelvin (William Thomson) from 1862 to 1899 performed a number of calculations, cat. imposed restrictions on the possible age of the Earth. They were based on consideration of the luminosity of the Sun, the influence of lunar tides and the cooling processes of the Earth. He came to the conclusion that the age of the Earth is 20-40 million years. Rutherford later performed a determination of the age of U min. and obtained values ​​of about 500 million years. Later, Arthur Holmes in his book “The Age of the Earth” (1913) showed the importance of studying radioactivity in geochronology and gave the first GHS. It was based on consideration of data on the thickness of sedimentary sediments and on the content of radiogenic decay products - He and Pb in U-containing minerals. Geochronological scale- scale of natural historical development of the Earth, expressed in numerical units of time. The age of earth's accretion is about 4.55 billion years. A period of up to 4 or 3.8 billion years is the time of differentiation of planetary interiors and formation primary cortex, it is called catarchaeum. The longest period of life of Z. and ZK is the Precambrian, cat. extends from 4 billion years to 570 million years, i.e. about 3.5 billion years. The age of the oldest rocks known today exceeds 4 billion years.

9. Geochemical classification of elements V.M. HolschmidtBased on: 1- electrical distribution. between different phases of meteorites - separation during the primary GC differentiation. 2- specific chemical affinity with certain elements (O, S, Fe), 3- structure of electronic shells. The leading elements composing meteorites are O, Fe, Mg, Si, S. Meteorites consist of three main phases: 1) metal, 2) sulfide, 3) silicate. All email are distributed among these three phases in accordance with their relative affinity for O, Fe and S. In Goldschmidt’s classification, the following groups of elements are distinguished: 1) Siderophilous(lovers of iron) – metal. meteorite phase: electrons forming alloys of arbitrary composition with Fe - Fe, Co, Ni, all platinoids (Ru, Rh, Pd, Pt, Re, Os, Ir), and Mo. They often have a native state. These are the transition elements of group VIII and some of their neighbors. Form the inner core of Z. 2) Chalcophilic(copper-loving) - sulfide phase of meteorites: electrons that form natural compounds with S and its analogues Se and Te, also have an affinity for As (arsenic), sometimes they are called (sulfurophilic). They easily turn into a native state. These are elements of secondary subgroups I-II and main subgroups III-VI of groups PS from 4 to 6 period S. The most famous are Cu, Zn, Pb, Hg, Sn, Bi, Au, Ag. Siderophilic el. – Ni, Co, Mo can also be chalcophile with a large amount of S. Fe in recovery conditions has an affinity for S (FeS2). In the modern model of gold, these metals form the outer, sulfur-enriched core of gold.

3) Lithophilic(stone-loving) – silicate phase of meteorites: el., having an affinity for O 2 (oxyphilic). They form oxygen compounds - oxides, hydroxides, salts of oxygen acids - silicates. In compounds with oxygen they have an 8-electron ext. shell. This is the largest group of 54 elements (C, common petrogenic - Si, Al, Mg, Ca, Na, K, elements of the iron family - Ti, V, Cr, Mn, rare - Li, Be, B, Rb, Cs, Sr , Ba, Zr, Nb, Ta, REE, i.e. all others except atmophilic ones). Under oxidizing conditions, iron is oxyphilic - Fe2O3. form the mantle Z. 4) Atmophilic(typical gaseous state) – chondrite matrix: H, N inert gases (He, Ne, Ar, Kr, Xe, Rn). They form the atmosphere of the Earth. There are also such groups: rare earth Y, alkaline, large-ion lithophile elements LILE (K, Rb, Cs, Ba, Sr), high-charge elements or elements with high field strength HFSE (Ti, Zr, Hf, Nb, Ta , Th). Some definitions of email: petrogenic (rock-forming, main) minor, rare, trace elements- from conc. no more than 0.01%. scattered– microel. not forming their own minerals accessory- form accessory min. ore- form ore mines.

10. Basic properties of atoms and ions that determine their behavior in natural systems. Orbital radii - radii of maxima of radial density e – ext. orbitals. They reflect the sizes of atoms or ions in a free state, i.e. outside chem. communications. The main factor is the e – electrical structure, and the more e – shells, the larger the size. For def. the sizes of atoms or ions in an important way. Def. distance from the center of one atom to the center of another, cat. is called the bond length. X-ray methods are used for this. To a first approximation, atoms are considered as spheres, and the “additivity principle” is applied, i.e. It is believed that the interatomic distance is the sum of the radii of the atoms or ions that make up the substance. Then knowing or accepting a certain value as the radius of one el. you can calculate the sizes of all the others. The radius calculated in this way is called effective radius . Coordination number- the number of atoms or ions located in close proximity around the atom or ion in question. The CN is determined by the ratio R k /R a: Valence - the amount of e – donated or attached by an atom during the formation of a chemical. communications. Ionization potential is the energy required to remove e – from an atom. It depends on the structure of the atom and is determined experimentally. The ionization potential corresponds to the voltage of the cathode rays, which is sufficient to ionize an atom of this electron. There may be several ionization potentials, for several e - removed from the external. e – shells. Breaking off each subsequent e requires more energy and is not always possible. Usually they use the ionization potential of the 1st e – , cat. detects periodicity. On the ionization potential curve, alkali metals, which easily lose e – , occupy the minimums on the curve, and inert gases occupy the peaks. As the atomic number increases, the ionization potentials increase in a period and decrease in a group. The reciprocal is the affinity ke – . Electronegativity - the ability to attract e – when entering into connections. The halogens are the most electronegative, the alkali metals the least. Electronegativity depends on the charge of the atomic nucleus, its valence in a given compound and the structure of the e-shells. Attempts have been made repeatedly to express EO in energy units or in conventional units. The EO values ​​change naturally across PS groups and periods. EO is minimal for alkali metals and increase towards halogens. For lithophilic cations, the EO decreases. from Li to Cs and from Mg to Ba, i.e. with increased ionic radius. In chalcophilic el. EO is higher than that of lithophiles from the same PS group. For anions of group O and F, EO decreases down the group and therefore it is maximum for these elements. Email with sharply different values ​​of EO form compounds with an ionic type of bond, and with close and high ones - with a covalent type of bond, with close and low ones - with a metallic type of bond. The Cartledge ionic potential (I) is equal to the ratio of valence to Ri, it reflects the properties of cationogenicity or ionogenicity. V.M. Golshmidt showed that the properties of cationogenicity and anionogenicity depend on the ratio of valence (W) and Ri for ions such as noble gases. In 1928, K. Cartledge called this ratio the ionic potential I. At small values ​​of I el. behaves like a typical metal and cation (alkali and alkaline earth metals), and at large - like a typical non-metal and anion (halogens). It is convenient to depict these relationships graphically. Diagram: ionic radius - valence. The magnitude of the ionic potential allows one to judge the mobility of the electron. V aquatic environment. Email with low and high values ​​of I they are the most mobile easily (with low values ​​they pass into ionic solutions and migrate, with high values ​​they form complex soluble ions and migrate), and with intermediate values ​​they are inert. Main types of chemicals bonds, character of bonds in the main groups of minerals. Ionic– an image due to the attraction of ions with opposite charges. (with a large difference in electronegativity) Ionic bonding predominates in most min. ZK - oxides and silicates, this is the most common type of bond also in hydro- and atmospheres. The connection ensures easy dissociation of ions in melts, solutions, gases, due to which wide migration of chemicals occurs. El., their dispersion and concentration in the earth's geospheres. Covalent – noun due to the interaction of e – used by different atoms. Typical for email. with an equal degree of attraction e –, i.e. EO. Characteristic for liquid and gaseous substances (H2O, H2, O2, N2) and less for crystals. Covalent bonds characterize sulfides, related compounds As, Sb, Te, as well as monoel. non-metal compounds - graphite, diamond. Covalent compounds are characterized by low solubility. Metal- a special case covalent bond, when each atom shares its e - with all neighboring atoms. e – capable of free movement. Typical for native metals (Cu, Fe, Ag, Au, Pt). Many min. have a connection, cat. refers partly to ionic, partly to covalent. In sulfide min. The covalent bond is maximally manifested; it occurs between the metal atoms and S, and the metal bond occurs between the metal atoms (metal luster of sulfides). Polarization - This is the effect of distortion of the e-cloud of an anion by a small cation with a high valence so that the small cation, attracting a large anion to itself, reduces its effective R, itself entering its e-cloud. Thus, the cation and anion are not regular spheres, and the cation causes deformation of the anion. The higher the charge of the cation and the smaller its size, the stronger the polarization effect. And the larger the size of the anion and its negative charge, the more it is polarized - deformed. Lithophilic cations (with 8 electron shells) cause less polarization than ions with complementary shells (such as Fe). Chalcophile ions with large ordinal numbers and high valence call the strongest polarization. This is associated with the formation of complex compounds: 2-, , 2-, 2-, cat. soluble and yavl. the main transporters of metals in hydrothermal solutions.

11.State (form of location) email. in nature. In GC the following are distinguished: min. (crystalline phases), impurities in min., various forms of dispersed state; email location form in nature carries information about the degree of ionization, chemical characteristics. email connections in phases, etc. In-vo (el.) is in three main forms. The first is the end atoms, the image. stars are different. types, gas nebulae, planets, comets, meteorites and cosmos. TV particles in. Concentration degree The substance is different in all bodies. The most diffuse states of atoms in gaseous nebulae are held by gravitational forces or are on the verge of overcoming them. The second is scattered atoms and molecules, an image of interstellar and intergalactic gas, consisting of free atoms, ions, molecules, e – . The amount of it in our Galaxy is significantly less than that which is concentrated in stars and gaseous nebulae. Interstellar gas is located at different levels. stages of rarefaction. Third - intensively migrating, flying at enormous speed atomic nuclei and the elementary particles that make up cosmic rays. IN AND. Vernadsky identified the main four forms of occurrence of chemicals. Email in the Earth's Earth and on its surface: 1. rocks and minerals (solid crystalline phases), 2. magma, 3. dispersed state, 4. living matter. Each of these forms is distinguished by a special state of their atoms. Noun and other selection of forms of location of email. in nature, depending on specific holy elements themselves. A.I. Perelman highlighted mobile and inert forms finding chemical Email in the lithosphere. By his definition, movable form represents such a state of chemistry. Email in gp, soils and ores, being in the cat. Email can easily move into the solution and migrate. Inert form represents such a state in mineral deposits, ores, weathering crust and soils, in cat. Email in this situation, it has a low migration ability and cannot move into the region and migrate.

12.Internal factors of migration.

Migration- movement of chemicals Email in geospheres Z, leading to their dispersion or conc. Clarke - medium conc. in the main types of gp ZK of each chemical. Email can be considered as the state of its equilibrium under the conditions of a given chemical. environment, deviation from cat. is gradually reduced by the migration of this electricity. Under terrestrial conditions, the migration of chemicals. Email occurs in any medium - TV. and gaseous (diffusion), but easier in a liquid medium (in melts and aqueous solutions). At the same time, the forms of migration of chemicals. Email are also different - they can migrate in atomic (gases, melts), ionic (solutions, melts), molecular (gases, solutions, melts), colloidal (solutions) forms and, in the form of clastic particles (air and water environment ). A.I. Perelman distinguishes four types of chemical migration. El.: 1.mechanical, 2.physical-chemical, 3.biogenic, 4.technogenic. The most important internal factors: 1. Thermal properties of electricity, i.e. their volatility or refractoriness. El., having a condensation temperature of more than 1400 o K are called refractory platinoids, lithophilic - Ca, Al, Ti, Ree, Zr, Ba, Sr, U, Th), from 1400 to 670 o K - moderately volatile. [lithophilic – Mg, Si (moderately refractory), many chalcophilic, siderophilic – Fe, Ni, Co ],< 670 o K – летучими (атмофильные). На основании этих св-в произошло разделение эл. по геосферам З. При магм. процессе в условиях высоких Т способность к миграции будет зависеть от возможности образования тугооплавких соединений и, нахождения в твердой фазе. 2. Хим. Св-ва эл. и их соединений. Атомы и ионы, обладающие слишком большими или слишком малыми R или q, обладают и повышенной способностью к миграции и перераспределению. Хим. Св-ва эл. и их соединений приобретают все большее значение по мере снижения T при миграции в водной среде. Для литофильных эл. с низким ионным потенциалом (Na, Ca, Mg) в р-рах хар-ны ионные соединения, обладающие высокой раствор-ю и высокими миграционными способностями. Эл. с высокими ионными потенциалами образуют растворимые комплексные анионы (С, S, N, B). При низких Т высокие миграционные способности газов обеспечиваются слабыми молекулярными связями их молекул. Рад. Св-ва, опред-ие изменение изотопного состава и появление ядер других эл.

Meteorites are small iron, stone or iron-stone space objects that regularly fall to 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 conceal many mysteries from the history of the universe. Meteorites help scientists uncover the secrets of evolution celestial bodies and study processes occurring far beyond our planet.

By analyzing their chemical and mineral composition, it is possible to trace patterns and connections between meteorites various types. But each of them is unique, with qualities inherent only to 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. Studying all known varieties of meteorites, scientists came 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 - origin. All of them are fragments of celestial bodies (asteroids and planets), moving in outer space at high speed.

Morphology

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

Oriented conical shape;

Melting crust;

Special surface relief.

A distinctive feature of real meteorites is the melting crust. It can differ quite significantly in color and structure (depending on the type of body of cosmic origin). In chondrites it is black and matte, in achondrites it is shiny. IN in rare cases The fusion bark can 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 bodies of cosmic origin after a certain time is practically no different from pieces of iron or stones.

Another distinctive external sign, which a real meteorite has, is the presence on the surface of depressions called piezoglypts or regmaglypts. Resembles fingerprints on soft clay. Their size and structure depend on the conditions of movement of the meteorite 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, this 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 noticeable. Comparing the average values ​​of the brightness coefficient of meteorites with the albedo of 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.

Chemical composition of meteorites

Considering the asteroidal origin of meteorites, their chemical composition may differ quite significantly between objects different types. This has a significant impact 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 in the form of nickel iron. Even stony meteorites have an average Fe content of 15.5%.

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

3. Cobalt (Co). Not found in pure form. Compared to nickel, it is 10 times less common.

4. Sulfur (S). Part of the mineral troilite.

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

3. Orthorhombic pyroxene. Often found in stony meteorites, it is the second most common among silicates.

4. Monoclinic pyroxene. It is found rarely and in small quantities in meteorites, with the exception of achondrites.

5. Plagioclase. A common rock-forming mineral belonging to the feldspar group. Its content in meteorites varies widely.

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

> 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 it is 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 is a large number 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 a 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 is clearly visible if the iron meteorite is cut into plates, polished and then etched in a weak solution of 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 thin strip(less than 1 mm) is called "fine-structured octahedrite", with a wide band of "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 rocky meteorites, especially those that have been on the surface of our planet for a long time, look very much like ordinary terrestrial 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, even before 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 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 lunar and Martian rocks on our surface? 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 open 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 clear enough to display an emerald green color, they are known as a perodot gemstone. 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, when the plate is cut and sanded, and the occasional inclusions, results in a very unusual appearance. 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 brief overview of the topic. Classification methods have changed several times over the years last years; known meteorites were reclassified into another class.

Meteorites consist of the same chemical elements found on Earth.

Basically there are 8 elements: iron, nickel, magnesium, sulfur, aluminum, silicon, calcium, oxygen. Other elements are also found in meteorites, but in very small quantities. The constituent elements interact with each other to form various minerals in meteorites. Most of them are also present on Earth. But there are meteorites with minerals unknown on earth.
Meteorites are classified according to their composition as follows:
stone(Most of them chondrites, because contain chondrules- spherical or elliptical formations of predominantly silicate composition);
iron-stone;
iron.

Iron meteorites consist almost entirely of iron combined with nickel and a small amount of cobalt.
Rocky meteorites contain silicates - minerals that are a compound of silicon with oxygen and admixtures of aluminum, calcium and other elements. IN stone In meteorites, nickel iron is found in the form of grains in the meteorite mass. Iron-stone meteorites consist mainly of equal amounts of stony material and nickel iron.
Found in different places on Earth tektites– small glass pieces of a few grams. But it has already been proven that tektites are frozen terrestrial matter ejected during the formation of meteorite craters.
Scientists have proven that meteorites are fragments of asteroids (minor planets). They collide with each other and break into smaller fragments. These fragments fall to Earth in the form of meteorites.

Why do we study the composition of meteorites?

This study provides insight into the composition, structure and physical properties other celestial bodies: asteroids, planetary satellites, etc.
Traces of extraterrestrial organic matter have also been found in meteorites. Carbonaceous (carbonaceous) meteorites have one important feature- the presence of a thin glassy crust, apparently formed under the influence of 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. What does it mean? This means that when studying the chemical nature of such meteorites, substances were discovered in their composition that, in modern earthly conditions, are organic compounds, having a biogenic nature. I would like to hope that this fact indicates the existence of life outside the Earth. But, unfortunately, it is impossible to speak about this clearly and with confidence, because theoretically, these substances could also be synthesized abiogenically. Although it can be assumed that if the substances found in meteorites are not products of life, then they may be products of pre-life - similar to that which once existed on Earth.
When studying stony meteorites, even so-called “organized elements” are discovered - microscopic (5-50 microns) “single-cell” formations, often having clearly defined double walls, pores, spines, etc.
Meteorite falls are impossible to predict. Therefore it is unknown where and when meteorite will fall. For this reason, only a small part of the meteorites that fall to Earth ends up in the hands of researchers. Only 1/3 part fallen meteorites observed during a fall. The rest are random finds. Of these, most are iron ones, as they last longer. Let's talk about one of them.

Sikhote-Alin meteorite

He fell in the Ussuri taiga in the Sikhote-Alin mountains on Far East On February 12, 1947, at 10:38 a.m., it fragmented in the atmosphere and fell as iron rain over an area of ​​35 square kilometers. Parts of the rain were scattered across the taiga over an area in the form of an ellipse with an axis about 10 kilometers long. In the head part of the ellipse (crater field) 106 craters were discovered, with a diameter from 1 to 28 meters, the depth of the largest crater reached 6 meters.
According to chemical analyses, the Sikhote-Alin meteorite is classified as iron: it consists of 94% iron, 5.5% nickel, 0.38% cobalt and small amounts of carbon, chlorine, phosphorus and sulfur.
The first to discover the site of the meteorite fall were the pilots of the Far Eastern Geological Department, who were returning from a mission.
In April 1947, to study the fall and collect all parts of the meteorite, the Committee on Meteorites of the USSR Academy of Sciences organized an expedition led by Academician V. G. Fesenkov.
Now this meteorite is in the meteorite collection Russian Academy Sci.

How to recognize a meteorite?

Almost most meteorites are found by accident. How can you determine that what you found is a meteorite? Here are the simplest signs of meteorites.
They have high density. They are heavier than granite or sedimentary rocks.
The surface of meteorites often shows smooth depressions, like finger indentations in clay.
Sometimes a meteorite looks like a blunted projectile head.
Fresh meteorites show a thin melting crust (about 1 mm).
The fracture of a meteorite is most often gray in color, on which small balls - chondrules - are sometimes visible.
In most meteorites, inclusions of iron are visible in the cross-section.
Meteorites are magnetized, the compass needle deviates noticeably.
Over time, meteorites oxidize in air, acquiring a rusty color.

Updated 10/24/2018

Depending on the dominant composition of the material of the meteorite, three main types of meteorites are distinguished (type of meteorites):

stony meteorites– the composition of the meteorite is dominated by mineral material

iron meteorites- the metal component dominates in the composition of the meteorite

iron-stone meteorites– the meteorite consists of mixed material

This is a traditional, classical classification of meteorites, quite simple and convenient. However, the modern scientific classification of meteorites is based on the division into groups in which meteorites have common physical, chemical, isotopic and mineralogical properties...

Stone meteorites

Stone meteorites ( stony meteorites- English) at first glance resemble earthly stones. This is the most common type of meteorite (about 93% of all falls). There are two groups of stony meteorites: chondrites(overwhelming majority 86%) and achondrites.

olivines(Fe, Mg)2 - (fayalite Fe2 and forsterite Mg2)

pyroxenes(Fe, Mg)2Si2O6 - (ferrosilite Fe2Si2O6 and enstatite Mg2Si2O6)

There are no chondrules in achondrites. It has been established that achondrites are fragments of planets and asteroids, for example, meteorites from Mars and the Moon are achondrites. The structure and composition of these stony meteorites are close to terrestrial basalts. Achondrites are a fairly common type of meteorite (about 8% of all meteorites found).

Stone meteorites contain inclusions of nickel iron (usually no more than 20% of the mass), as well as other. According to experts, the age of stone meteorites is about 4.5 billion years.

Iron meteorites

Iron meteorites ( iron meteorites- English) consist mainly of metal, a mixture (alloy) of iron and nickel in various proportions, and they also contain inclusions of other elements and minerals, but they rarely account for more than 20% of the mass (about 6% of the fall). The Ni content in iron meteorites ranges from 5 to 30% or more.

Even ordinary meteorites react most clearly to this type of meteorite. The fracture of the meteorite has a characteristic metallic sheen. Melting bark is gray or brown, making it difficult to see visually.

Stone-iron meteorites

Stone-iron meteorites ( iron-stony meteorites- English) quite a rare type of meteorite (about 1.5% of falls). The composition of these meteorites is intermediate between stone and iron meteorites. There are two groups of iron-stony meteorites: pallasites And mesosiderites.

The structure of pallasite is translucent crystals of olivine (Fe, Mg)2, enclosed in a matrix of iron and nickel. Pallasites on a fracture (in section) have an attractive aesthetic appearance and are a desirable acquisition for collectors. is in the range of $6 - $60 or more per gram of meteorite matter.

Mesosiderites this is a very rare type of meteorite (about 0.5% of falls). Mesosiderites contain approximately equal proportions of iron, nickel and silicate minerals such as pyroxenes, olivine, and feldspar.

The most valuable, both from the point of view of science and from the point of view of business on meteorites and collecting, are, first of all, as well as the entire “family” of iron-stone meteorites.

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