Meteorites: types, mineral and chemical composition.

Let's talk about how a meteor differs from a meteorite in order to know the mystery and uniqueness of the starry sky. People trust the stars with their most cherished desires, but we will talk about other celestial bodies.

Meteor Features

The concept of "meteor" is associated with phenomena occurring in the earth's atmosphere, in which foreign bodies invade it at a considerable speed. The particles are so small that they are rapidly destroyed by friction.

Do meteors hit? The description of these celestial bodies, offered by astronomers, is limited to indicating a short-term luminous strip of light in the starry sky. Scientists call them "shooting stars".

Characteristics of meteorites

A meteorite is the remains of a meteoroid that hits the surface of our planet. Depending on the composition, there is a division of these celestial bodies into three types: stone, iron, iron-stone.

Differences between celestial bodies

How is a meteor different from a meteorite? This question has long remained a mystery for astronomers, an occasion for observations and research.

Meteors after the invasion of the earth's atmosphere lose their mass. Before the combustion process, the mass of this celestial object does not exceed ten grams. This value is so insignificant in comparison with the size of the Earth that there will be no consequences from the fall of the meteor.

Meteorites that hit our planet have a significant weight. The Chelyabinsk meteorite, which fell to the surface on February 15, 2013, according to experts, had a weight of about ten tons.

The diameter of this celestial body was 17 meters, the speed of movement exceeded 18 km / s. The Chelyabinsk meteorite began to explode at an altitude of about twenty kilometers, and the total duration of its flight did not exceed forty seconds. The power of the explosion was thirty times higher than the bombing in Hiroshima, as a result, numerous pieces and fragments were formed that fell on the Chelyabinsk soil. So, arguing over how a meteor differs from a meteorite, first of all, we note their mass.

The largest meteorite was an object discovered at the beginning of the twentieth century in Namibia. Its weight was sixty tons.

Fall frequency

How is a meteor different from a meteorite? Let's continue talking about the differences between these celestial bodies. Hundreds of millions of meteors flare up in the earth's atmosphere every day. In the case of clear weather, you can observe about 5-10 “shooting stars” per hour, which are actually meteors.

Meteorites also quite often fall on our planet, but most of them burn out during the journey. During the day, several hundred such celestial bodies hit the earth's surface. Due to the fact that most of them land in the desert, seas, oceans, they are not found by researchers. Scientists per year manage to study only a small number of these celestial bodies (up to five pieces). Answering the question of what meteors and meteorites have in common, one can note their composition.

Fall danger

Small particles that make up a meteoroid can cause serious harm. They render the surface of spacecraft unusable and can disable the operation of their energy systems.

It is difficult to assess the real danger posed by meteorites. A huge number of "scars" and "wounds" remain on the surface of the planet after their fall. If such a celestial body is large, after its impact on the Earth, an axis shift is possible, which will negatively affect the climate.

In order to fully appreciate the full scale of the problem, we can give an example of the fall of the Tunguska meteorite. It fell into the taiga, causing serious damage to an area of ​​several thousand square kilometers. If this territory was inhabited by people, we could talk about a real disaster.

A meteor is a light phenomenon that is often observed in the starry sky. Translated from Greek, this word means "heavenly". A meteorite is a solid body of cosmic origin. Translated into Russian, this term sounds like "a stone from the sky."

Scientific research

In order to understand how comets differ from meteorites and meteors, we analyze the results of scientific research. Astronomers managed to find out that after a meteor hits the earth's layers of the atmosphere, they flare up. In the process of combustion, a luminous trace remains, consisting of The particles of the meteor fade away at an altitude of approximately seventy kilometers from the Comet leaves a "tail" in the starry sky. Its basis is the core, which includes dust and ice. In addition, the following substances can be located in the comet: carbon dioxide, ammonia, organic impurities. The dust tail that it leaves during its movement consists of particles of gaseous substances.

Getting into the upper layers of the Earth's atmosphere, fragments of destroyed cosmic bodies or dust particles are heated by friction and flare up. The smallest of them immediately burn out, and the largest, continuing to fall, leave behind a luminous trail of ionized gas. They go out, reaching a distance approximately equal to seventy kilometers from the surface of the earth.

The duration of the flash is determined by the mass of this celestial body. In the case of burning large meteors, you can admire bright flashes for several minutes. It is this process that astronomers call stellar rain. In the case of a meteor shower, about a hundred burning meteors can be seen in one hour. If a celestial body has a large size, in the process of moving through the dense earth's atmosphere, it does not burn out and falls on the surface of the planet. No more than ten percent of the initial weight of the meteorite reaches the Earth.

Iron meteorites contain significant amounts of nickel and iron. The basis of stone celestial bodies are silicates: olivine and pyroxene. Iron-stone bodies have almost equal amounts of silicates and nickel iron.

Conclusion

People at all times of their existence have tried to study celestial bodies. They made calendars by the stars, determined the weather conditions, tried to predict fate, experienced fear of the starry sky.

After the advent of various types of telescopes, astronomers managed to unravel many mysteries and mysteries of the starry sky. Comets, meteors, meteorites were studied in detail, the main distinguishing and similar features between these celestial bodies were determined. For example, the largest meteorite that hit the surface of the earth was the iron Goba. His scientists discovered in Young America, his weight was about sixty tons. The most famous comet in the solar system is Halley's comet. It is she who is connected with the discovery of the law of universal gravitation.

A meteorite is a piece of matter, of cosmic origin, that has fallen on the surface of any large celestial object. Literally, the meteorite is translated as "a stone from the sky." The vast majority of meteorites that have been found on earth weigh from a few grams to several kilograms. Goba - the largest meteorite found, weighed approximately 60 tons. Scientists believe that up to 5 tons of meteorites fall to Earth every day. But until quite recently, their existence was not recognized by well-known academicians and specialists in space research. All information and hypotheses about their extraterrestrial origin were recognized as pseudoscientific and stopped in the bud.

Meteorites are considered the oldest known minerals, which can be up to 4.5 billion years old. Therefore, scientists believe that the remnants of the processes that accompanied the formation of the planets should be preserved in them. Meteorites remained the only unique samples of extraterrestrial origin until samples of lunar soil were brought to Earth. Chemists, geologists and physicists have been collecting information and studying meteorites in detail for more than two hundred years. This knowledge gave impetus to the development of a new science of meteorites. People have known about the fall of celestial bodies to Earth since ancient times, and some nations even revered and worshiped them. Only scientists were very skeptical about them. But the facts and common sense prevailed, over time it became pointless to deny their cosmic origin.

Classification of meteorites

There are several types and names of meteorites: siderolites, uranoliths, aerolites, meteor stones and others. Any cosmic body before entering the atmosphere is called a meteoroid. It is classified according to various astronomical features. It can be a meteorite, an asteroid, space dust, fragments, etc. Flying through the earth's atmosphere and leaving a bright luminous trail, the object can be called a fireball or meteor. And a solid body that fell to the surface of the Earth and left a characteristic depression - a crater, is considered a meteorite. It is customary to give them "names" after the names of the places where they were found.

Stony meteorites are divided into two subclasses: chondrites and achondrites. Chondrites are so named because almost all of them contain chondrules - spheroidal formations of predominantly silicate composition. Chondrules are the most primitive types of meteorites. They are in a fine crystalline matrix, and most of the chondrules are less than 1 mm in diameter. Chondrites can be up to 4.5 billion years old.

Less than 10% of the total number of stony meteorites form a subclass of achondrites. Achondrites are very similar to terrestrial igneous rocks. They are devoid of chondrules and consist of a substance that was formed as a result of the processes of melting of planetary and protoplanetary and planetary bodies. Most of the meteorites that hit Earth come from the asteroid belt between Mars and Jupiter, and this is not surprising. After all, the largest and most famous accumulation of meteorite bodies is observed there.

According to the nature of detection, meteorites are divided into "fallen" and "found". Found, consider those meteorites, the fall of which was not observed by man. Their belonging to celestial bodies is established by studying the features of their composition. The vast majority of meteorites in private collections and world museums are just finds. Very often, stone meteorites simply go unnoticed, as they can easily be confused with ordinary terrestrial rocks.

Meteorite- this is a solid extraterrestrial substance that was preserved during the passage through the atmosphere and reached the surface of the Earth. Meteorites are the most primitive of the SS, which have not experienced further fractionation since their formation. This is based on the fact that the relative distribution refractory el. in meteorites corresponds to the solar distribution. Meteorites are classified into (according to the content of the metal phase): Stone(aeroliths): achondrites, chondrites, iron stone(siderolites), iron(siderites). Iron meteorites - consist of kamacite - native Fe of cosmic origin with an admixture of nickel from 6 to 9%. Iron stone meteorites Small distribution Group. They have coarse-grained structures with equal weight proportions of silicate and Fe phases. (Silicate minerals - Ol, Px; Fe phase - kamacite with Widmanstätten intergrowths). Stone meteorites - consist of silicates of Mg and Fe with an admixture of metals. Subdivided into Chondrite, achondrite and carbonaceous.Chondrites: spheroidal segregations of the first mm or less in size, composed of silicates, less often silicate glass. Embedded in a Fe-rich matrix. The groundmass of chondrites is a fine-grained mixture of Ol, Px (Ol-bronzite, Ol-hypersthene and Ol-pijonitic) with nickel Fe (Ni-4-7%), troilite (FeS) and plagioclase. Chondrites - crystallized. or glassy drops, cat. Image. when melting a pre-existing silicate material subjected to heating. Achondrites: Do not contain chondrules, have a lower content. nickel Fe and coarser structures. Their main minerals are Px and Pl, some types are enriched in Ol. Achondrites are similar in composition and structural features to terrestrial Gabbroids. The composition and structure speak of a magmatic origin. Sometimes there are bubbly structures like lavas. Carbonaceous chondrites (large amounts of carbonaceous matter) Characteristic feature of carbonaceous chondrites - the presence of a volatile component, which indicates primitiveness (the removal of volatile elements did not occur) and did not undergo fractionation. Type C1 contains a large number of chlorite(aqueous Mg, Fe aluminosilicates), as well as magnetite, water-soluble salt, nativeS, dolomite, olivine, graphite, organ. connections. Those. since their image-I they are noun. at T, not > 300 0 С. chondrite meteorites lack of 1/3 chem. Email compared to composition carbonaceous chondrites, cat. closest to the composition of protoplanetary matter. The most likely cause of the shortage of volatile email. - sequential condensation el. and their compounds in reverse order of their volatility.

5.Historical and modern models of accretion and differentiation of protoplanetary matter O.Yu. Schmidt in the 1940s expressed the idea that the Earth and the planets of the CG were formed not from hot clots of solar gases, but through the accumulation of HB. bodies and particles - planetesimals that experienced melting later during accretion (heating due to collisions of large planetesimals, up to a few hundreds of kilometers in diameter). Those. early differentiation of the core and mantle and degassing. Ex. relates two points of view. accumulation mechanism and ideas about the form of the layered structure of the planets. Models homogeneous and heterogeneous accretion: HETEROGENEOUS ACCRETION 1. Short-term accretion. Early heterogeneous accretion models(Turekian, Vinogradov) assumed that Z. accumulated from the material as it condensed from the protoplanetary cloud. Early models include an early > T accumulation of the Fe-Ni alloy, which forms the proto-core of Z., changing from lower. T by accretion of its outer parts from silicates. Now it is believed that in the process of accretion there is a continuous change. in the accumulating material of the Fe/silicate ratio from the center to the periphery of the formed planet. As the earth accumulates, it heats up and melts Fe, which separates from the silicates and sinks into the core. After the cooling of the planet, about 20% of its mass is added with material enriched in volatiles along the periphery. In the proto-earth, there were no sharp boundaries between the core and the mantle, a cat. established as a result of gravitation. and chem. differentiation at the next stage of the evolution of the planet. In the early versions, differentiation occurred mainly during the formation of the ZK, and did not capture the Earth as a whole. HOMOGENEOUS ACCRETION 2. A longer accretion time of 108 years is assumed. 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 substances enriched in refractory components of the Allende type. Planets of forms. from this set of meteorites in-va and their difference and similarity was determined by relative. proportions in-va different composition. It also took place macroscopic homogeneity of protoplanets. The existence of a massive core suggests that the alloy initially introduced by Fe-Ni meteorites, uniformly distributed throughout the Earth, separated out in the course of its evolution into the central part. Homogeneous in composition the planet was stratified into shells in the process of gravitational differentiation and chemical processes. Modern model of heterogeneous accretion to explain the chem. the composition of the mantle is being developed by a group of German scientists (Wencke, Dreybus, Yagoutz). They found that the content in the mantle of moderately volatile (Na, K, Rb) and moderately siderophilic (Ni, Co) el., with different. The distribution coefficients of 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 :one. Accretion begins with the accumulation of a strongly reduced component A, devoid of volatile elements. and containing all the other email. in quantities corresponding to C1, and Fe and all siderophiles in the reduced state. With an increase in T, the formation of a nucleus 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. and transfer them to the kernel. A source of moderately volatile, volatile and moderately siderophilic el. in the mantle yavl. component B, which explains their close relative abundance. Thus, the Earth is 85% composed of component A and 15% of component B. In general, the composition of the mantle is formed after separation of the core by homogenization and mixing of the silicate part of component A and the substance of component B.

6. Isotopes of chemical elements. isotopes - atoms of the same electron, but having a different number of neutrons N. They differ only in mass. isotons - atoms of different el., having different Z, but the same N. They are arranged in vertical rows. isobars - atoms of different el., in a cat. equal masses. numbers (A=A), but different Z and N. They are arranged 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 are stable, in a cat. N and Z are approximately equal. Up to Ca in N=Z nuclei. 2. Most stable nuclides have even Z and N. 3. Less common are stable nuclides with even numbers. Z and odd. N or even N and odd. Z. 4. Rare stable nuclides with odd Z and N.

In kernels from even. Z and N nucleons form an ordered structure, which determines their stability. The number of isotopes is less in light email. and took away. in the middle part of the PS, reaching a maximum for 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 emission of particles and/or radiation of energy. St. glad-ty does not depend on the chemical. Holy atoms, but determined by the structure of their nuclei. Radioactive decay is accompanied by changes. Z and N of the parent atom and leads to the transformation of an atom of one el. into an atom of another email. It has also been shown by Rutherford and other scientists 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 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. a-particle consists of 2 P and 2N, there is a shift of 2 positions in Z. The initial isotope is called parental or maternal, and the newly formed - child.

b-decay- has three types: normal b-decay, positron b-decay and e - capture. Ordinary b-decay- can be considered as the transformation of a neutron into a proton and e - , the last 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 from the nucleus of a positive particle of a positron b, its formation - the transformation of a nuclear proton into a neutron, positron and neutrino. The daughter nuclide is an isobar but has a smaller charge.

Example, 9 F18 -> 8 O18 b v Q while the number N decreases. Atoms to the left of the region of nuclear stability are neutron-deficient, they undergo positron decay, and their number N increases. Thus, during b- and b-decay, there is a tendency for Z and N to change, leading to the approach of daughter nuclides to the zone of nuclear stability. e – capture- capture of one of the orbital electrons. High probability of capture from the K-shell, cat. closest to the core. e - capture causes emission from the neutrino nucleus. Daughter nuclide yavl. isobar, and occupies the same position relative to the parent as in positron decay. b - radiation is absent, and when a vacancy is filled in the K-shell, X-rays are emitted. 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 U and Th isotopes can decay either by emitting b-particles or by a-decay. If b-decay occurred first, then a-decay followed, and vice versa. In other words, these two alternative decay modes form closed cycles and always lead to the same end product - stable isotopes of Pb.

8. Geochemical consequences of the radioactivity of terrestrial matter. Lord Kelvin (William Thomson) from 1862 to 1899 performed a series 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 processes of cooling of the Earth. He came to the conclusion that the age of the Earth is 20-40 million years. Later, Rutherford performed the determination of the age of U min. and received 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 deposits and on the content of radiogenic decay products - He and Pb in U-bearing minerals. Geological scale- the scale of the natural historical development of the ZK, expressed in numerical units of time. The accretion age of Earth is about 4.55 billion years. The period up to 4 or 3.8 billion years is the time of differentiation of the planetary interior and the formation of the primary crust, it is called katarchey. 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 most ancient rocks known now exceeds 4 billion years.

9. Geochemical classification of elements by V.M. HolshmidtBased on: 1- distribution email. between different phases of meteorites - separation in the course of primary HC differentiation Z. 2 - specific chemical affinity with certain elements (O, S, Fe), 3 - structure of electron shells. The leading elements that make up meteorites are O, Fe, Mg, Si, S. Meteorites consist of three main phases: 1) metal, 2) sulfide, 3) silicate. All e-mail are distributed between these three phases in accordance with their relative affinity for O, Fe and S. In the Goldschmidt classification, the following groups of elec. are distinguished: 1) siderophilic(loving iron) - metal. phase of meteorites: el., 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 transitional elements of group VIII and some of their neighbors. Form the inner core Z. 2) Chalcophilic(copper-loving) - the sulfide phase of meteorites: elements that form natural compounds with S and its analogues Se and Te also have an affinity for As (arsenic), sometimes they are called (sulfurophilic). Easily pass into a native state. These are elements of secondary subgroups I-II and main subgroups III-VI groups of PS from 4 to 6 period S. The most famous are Cu, Zn, Pb, Hg, Sn, Bi, Au, Ag. Siderophile el. – Ni, Co, Mo can also be chalcophilic with a large amount of S. Fe under reducing conditions has an affinity for S (FeS2). In the modern model of the star, these metals form the outer, sulfur-enriched core of the star.

3) lithophilic(loving stone) - 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, widespread 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 the rest except atmophilic ones). Under oxidizing conditions, iron is oxyphilic - Fe2O3. form the mantle Z. 4) Atmophilic(har-but gaseous state) - chondrite matrix: H, N inert gases (He, Ne, Ar, Kr, Xe, Rn). They form the atmosphere Z. 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- with conc. no more than 0.01%. scattered- microel. not forming their own minerals accessory- form accessory min. ore- form ore mines.

10. The main properties of atoms and ions that determine their behavior in natural systems. Orbital radii - radii of the maxima of the radial density e – ext. orbitals. They reflect the sizes of atoms or ions in the free state, i.e. outside the chem. connections. The main factor is e - the structure of the electron, and the more e - shells, the larger the size. For def. sizes of atoms or ions in an important way yavl. Def. distance from the center of one atom to the center of another, cat. is called the bond length. For this, X-ray methods are used. In the first approximation, atoms are considered as spheres, and the “principle of additivity” 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 in-in. Then knowing or accepting a certain value as the radius of one el. you can calculate the dimensions of all others. The radius calculated in this way is called effective radius . coordination number is the number of atoms or ions located in close proximity around the considered atom or ion. CF is determined by the ratio R k /R a: Valence - the amount of e - given or attached to the atom during the formation of chemical. connections. 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 email. There may be several ionization potentials, for several e - removed from the external. e - shells. The separation of each subsequent e - requires more energy and may not always be. Usually use the ionization potential of the 1st e - , cat. detects periodicity. On the curve of ionization potentials, alkali metals, which easily lose e - , occupy minima on the curve, inert gases - peaks. As the atomic number increases, the ionization potentials increase in the period and decrease in the group. The reciprocal is the affinity ke – . Electronegativity - the ability to attract e - when entering into compounds. The halogens are the most electronegative, the alkali metals the least. Electronegativity depends on the charge of the nucleus of an atom, its valence in a given compound, and the structure of the e-shells. Repeated attempts have been made to express EC in units of energy or in conventional units. The EC values ​​regularly change by groups and periods of PS. EO is minimal for alkali metals and increases for halogens. In lithophilic cations, EO is reduced. from Li to Cs and from Mg to Ba, i.e. with a zoom ionic radius. In chalcophile el. EO is higher than that of lithophiles from the same PS group. For anions of the O and F groups, the EO decreases down the group and, therefore, it is maximum for these el. Email with sharply different EO values ​​form compounds with an ionic type of bond, and with close and high - with a covalent, with close and low - with a metallic type of bond. The ionic potential of Cartledge (I) is equal to the ratio of valence to R i , it reflects the properties of cationicity or ionogenicity. V.M. Golshmidt showed that the properties of cationicity and anionicity depend on the ratio of valence (W) and R i for ions of the noble gas type. 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). These relationships are conveniently depicted graphically. Diagram: ionic radius - valency. The value of the ionic potential allows us to judge the mobility of email. in the aquatic environment. Email with low and high values ​​of I 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 ones they are inert. The main types of chem. bonds, character bonds in the main groups of minerals. Ionic- image due to the attraction of ions with opposite charges. (with a large difference in electronegativity) Ionic bonding predominates in most mines. ZK - oxides and silicates, this is the most common type of bond also in hydro and atmospheres. Communication provides easy dissociation of ions in melts, solutions, gases, due to which there is a wide migration of chemical. El., their dispersion and end in the terrestrial geospheres. covalent - noun. due to the interaction e - used by different atoms. Typical for e. with an equal degree of attraction e – , i.e. EO. Har-na for liquid and gaseous substances (H2O, H2, O2, N2) and less for a crystal. Sulfides, related compounds As, Sb, Te, as well as monoel are characterized by a covalent bond. non-metal compounds - graphite, diamond. Covalent compounds are characterized by low solubility. metal- a special case of a 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, a cat. partly ionic, partly covalent. in sulfide mines. the covalent bond is maximally manifested, it takes place between the metal and S atoms, and the metallic one - between the metal atoms (metal, brilliance of sulfides). Polarization - this is the effect of distortion of the e-cloud of an anion by a small cation with a large valence so that a small cation, attracting a large anion to itself, reduces its effective R, itself entering its e-cloud. So the cation and anion are not regular spheres, and the cation causes the deformation of the anion. The higher the charge of the cation and the smaller its size, the stronger the effect of polarization. And the larger the size of the anion and its negative charge, the stronger it is polarized - deformed. Lithophilic cations (with 8 electron shells) cause less polarization than ions with completed shells (such as Fe). Chalcophile ions with large serial numbers and high-valent cause the strongest polarization. This is associated with the formation of complex compounds: 2-, , 2-, 2-, cat. soluble and yavl. the main carriers of metals in hydrothermal solutions.

11.Status (form of location) email. in nature. In GC allocate: actually min. (crystal. phases), impurities in min., various forms of the scattered state; email location form in nature carries information about the degree of ionization, har-re chem. email connections in phases, etc. V-in (el.) is in three main forms. The first is the end atoms, the image. stars are different. types, gaseous nebulae, planets, comets, meteorites and space. tv. particles in-va. Degree of conc. V-va in all bodies is different. The most scattered states of atoms in gaseous nebulae are held by gravitational forces or are on the verge of overcoming them. The second - scattered atoms and molecules, an image of interstellar and intergalactic gas, consisting of free atoms, ions, molecules, e -. Its quantity in our Galaxy is much less than that which is concentrated in stars and gaseous nebulae. Interstellar gas is located at different sparse stages. The third one is intensively migrating atomic nuclei and elementary particles, which make up cosmic rays, flying with tremendous speed. IN AND. Vernadsky singled out the main four forms of finding chem. Email in the ZK and on its surface: 1. rocks and minerals (solid crystalline phases), 2. magmas, 3. scattered state, 4. living matter. Each of these forms is distinguished by the special state of their atoms. Ex. and other allocation of forms of finding e-mail. in nature, depending on the specific sv-in themselves email. A.I. Perelman singled out mobile and inert forms finding chem. Email in the lithosphere. By his definition, movable form is such a state of chemistry. Email in gp, soils and ores, being in a cat. Email can easily pass into the solution and migrate. inert form represents such a state in urban settlements, ores, weathering crust and soils, in the cat. Email under the conditions of this situation, it has a low migratory mode and cannot move into the solution 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 chem. Email can be considered as a state of its equilibrium under the conditions of a given chemical. Wednesdays, a deviation from a cat. gradually reduced by migrating this email. Under terrestrial conditions, the migration of chemical Email happens 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 chemical 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 detrital particles (air and water environment ). A.I. Perelman distinguishes four types of chemical migration. El.: 1.mechanical, 2.phys.-chemical, 3.biogenic, 4.technogenic. The most important internal factors: 1. Thermal properties of electricity, i.e. their volatility or infusibility. El., having a condensation T 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. [lithophile - Mg, Si (moderately refractory), many chalcophile, siderophile - 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.

The main feature of meteorites is the so-called melting crust. It has a thickness of no more than 1 mm and covers the meteorite in the form of a thin shell from all sides. Black bark is especially visible on stone meteorites.

The second sign of meteorites are characteristic pits on their surface. Usually meteorites are in the form of debris. But sometimes there are meteorites of a wonderful cone shape. They resemble the head of a projectile. Such a conical shape is formed as a result of the “grinding” action of air.

The largest solid meteorite was found in Africa in 1920. This iron meteorite weighs about 60 tons. Usually meteorites weigh several kilograms. Meteorites weighing tens, and even more so hundreds of kilograms, fall very rarely. The smallest meteorites weigh fractions of a gram. For example, at the site of the fall of the Sikhote-Alin meteorite, the smallest specimen was found in the form of a grain weighing only 0.18 g; the diameter of this meteorite is only 4 mm.

Most often, stone meteorites fall: on average, out of 16 fallen meteorites, only one turns out to be iron.

WHAT ARE METEOORITES COMPOSED OF?

By studying the chemical composition of meteorites, scientists have found that meteorites are composed of the same chemical elements that are found on Earth. No new elements were found in them.

The eight elements most commonly found in meteorites are iron, nickel, sulfur, magnesium, silicon, aluminium, 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 composed almost entirely 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 acid solution, 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 white particles are visible in the fracture. 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 the yellowish-green color of the mineral olivine are enclosed.

ORIGIN OF METEORITES

Most scientists believe that meteorites are fragments of one or (more likely) several large celestial bodies, similar to asteroids that previously existed in the solar system.

Soviet scientists - academician V. G. Fesenkov, S. V. Orlov and others - believe that asteroids and meteorites are closely related. Asteroids are giant meteorites, and meteorites are very small, dwarf asteroids. 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.

HELP OF THE POPULATION IN COLLECTING METEORITES

Meteorites always fall unexpectedly, and it is impossible to predict when and where this will happen. Therefore, specialists cannot prepare in advance for observations of meteorite falls. Meanwhile, the study of the motions of meteoroids in the earth's atmosphere is of very great scientific importance.

In addition, observing the fireball, you can approximately determine the place where the meteorite could fall, and search for it there. Therefore, scientists in their work can be of great help to the population if eyewitnesses of the meteorite fall describe in detail all the phenomena that they noticed during the movement of the fireball and the fall of the meteorite to Earth.

Upon receipt of a large number of such descriptions made by eyewitnesses in different settlements, it is possible to determine quite accurately the path of the meteoroid in the Earth's atmosphere, the height of the appearance and disappearance of the fireball, as well as the slope and direction of its path. Messages about meteorites should be sent to the Committee on Meteorites of the USSR Academy of Sciences.

When a meteorite is found, in no case should it be crushed. It is necessary to take all measures to protect it and transfer it to the Committee on Meteorites.

When describing the phenomenon of fireballs, it is necessary, if possible, to answer the following questions: 1) the date and time of the fall; 2) place of observation; 3) the direction of movement of the fireball; 4) flight duration of the fireball in seconds; 5) the dimensions of the bolide compared with the apparent dimensions of the Moon or the Sun; 6) the color of the car; 7) whether the area was illuminated during the flight of the car; 8) whether crushing of the fireball was observed; 9) whether there was a trace left after the car; what is its form and subsequent change, as well as the duration of visibility; 10) what sounds were observed during the flight of the fireball and after its disappearance.

The description must also include the last name, first name, patronymic and address of the observer.

If you find an error, please highlight a piece of text and click Ctrl+Enter.

Meteorites are made up of the same chemical elements found on Earth.

Basically it is 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, forming 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 composition as follows:
stone(Most of them chondrites, because contain chondrules- spherical or elliptical formations of predominantly silicate composition);
iron-stone;
iron.

iron meteorites are almost entirely composed of iron combined with nickel and a small amount of cobalt.
rocky meteorites contain silicates - minerals, which are a combination of silicon with oxygen and an admixture of aluminum, calcium and other elements. IN stone meteorites found nickel iron in the form of grains in the mass of the meteorite. Iron-stone meteorites consist mainly of equal amounts of rocky matter and nickel iron.
Found in different places on Earth tektites- glass pieces of small size in 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 study the composition of meteorites?

This study gives an idea of ​​the composition, structure and physical properties of other celestial bodies: asteroids, satellites of planets, 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 stand high heat, such as gypsum, are preserved inside carbonaceous meteorites. What does it mean? This means that in the study of the chemical nature of such meteorites, substances were found in their composition that, under modern terrestrial conditions, are organic compounds of 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 unambiguously and with certainty, because. theoretically, these substances could be synthesized abiogenically. Although it can be assumed that if the substances found in meteorites are not products of life, then they can be products of pre-life - similar to the one that once existed on Earth.
In the study of stone meteorites, even the so-called "organized elements" are found - microscopic (5-50 microns) "unicellular" formations, often having pronounced double walls, pores, spikes, etc.
The fall of meteorites is impossible to predict. Therefore, it is not known where and when the meteorite will fall. For this reason, only a small part of the meteorites that fell to Earth falls into the hands of researchers. Only 1/3 of the fallen meteorites was observed during the fall. The rest are random finds. Of these, most of all are iron, since they last longer. Let's talk about one of them.

Sikhote-Alin meteorite

It fell in the Ussuri taiga in the Sikhote-Alin mountains in the Far East on February 12, 1947 at 10:38, was disintegrated in the atmosphere and fell like iron rain over an area of ​​35 square kilometers. Parts of the rain scattered over the taiga in 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 funnels were found, with a diameter of 1 to 28 meters, the depth of the largest funnel reached 6 meters.
According to chemical analysis, the Sikhote-Alin meteorite belongs to iron: it consists of 94% iron, 5.5% nickel, 0.38% cobalt and small amounts of carbon, chlorine, phosphorus and sulfur.
The first place where the meteorite fell was discovered by the pilots of the Far Eastern Geological Administration, 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 Academy of Sciences of the USSR organized an expedition led by Academician V. G. Fesenkov.
Now this meteorite is in the meteorite collection of the Russian Academy of Sciences.

How to recognize a meteorite?

In fact, 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 a high density. They are heavier than granite or sedimentary rocks.
On the surface of meteorites, smoothed depressions are often visible, as if the indentations of fingers in clay.
Sometimes a meteorite looks like a blunt projectile head.
On fresh meteorites, a thin melting crust (about 1 mm) is visible.
The fracture of a meteorite is most often gray, on which small balls - chondrules are sometimes visible.
In most meteorites, inclusions of iron are visible on the section.
Meteorites are magnetized, the compass needle deviates noticeably.
Over time, meteorites oxidize in air, acquiring a rusty color.