What light is best absorbed by cosmic dust particles? Where does cosmic dust come from?
Where does cosmic dust come from? Our planet is surrounded by a dense air shell - the atmosphere. The composition of the atmosphere, in addition to the gases known to everyone, also includes solid particles - dust.
It mainly consists of soil particles that rise upward under the influence of the wind. During volcanic eruptions, powerful dust clouds are often observed. Entire “dust caps” hang over large cities, reaching a height of 2-3 km. The number of dust particles in one cubic meter. cm of air in cities reaches 100 thousand pieces, while in clean mountain air there are only a few hundred of them. However, dust of terrestrial origin rises to relatively low altitudes - up to 10 km. Volcanic dust can reach a height of 40-50 km.
Origin of cosmic dust
The presence of dust clouds has been established at altitudes significantly exceeding 100 km. These are the so-called “noctilucent clouds”, consisting of cosmic dust.
The origin of cosmic dust is extremely diverse: it includes the remains of disintegrated comets and particles of matter ejected by the Sun and brought to us by the force of light pressure.
Naturally, under the influence of gravity, a significant part of these cosmic dust particles slowly settles to the ground. The presence of such cosmic dust was discovered on high snowy peaks.
Meteorites
In addition to this slowly settling cosmic dust, hundreds of millions of meteors burst into our atmosphere every day - what we call “falling stars”. Flying at cosmic speeds of hundreds of kilometers per second, they burn out from friction with air particles before they reach the surface of the earth. The products of their combustion also settle on the ground.
However, among the meteors there are also exceptionally large specimens that reach the surface of the earth. Thus, the fall of the large Tunguska meteorite at 5 o’clock in the morning on June 30, 1908 is known, accompanied by a number of seismic phenomena noted even in Washington (9 thousand km from the place of fall) and indicating the power of the explosion when the meteorite fell. Professor Kulik, who with exceptional courage examined the site of the meteorite fall, found a thicket of windfall surrounding the site of the fall within a radius of hundreds of kilometers. Unfortunately, he was unable to find the meteorite. An employee of the British Museum, Kirkpatrick, made a special trip to the USSR in 1932, but did not even get to the site of the meteorite fall. However, he confirmed the assumption of Professor Kulik, who estimated the mass of the fallen meteorite at 100-120 tons.
Cloud of cosmic dust
An interesting hypothesis is that of Academician V.I. Vernadsky, who considered it possible that it was not a meteorite that would fall, but a huge cloud of cosmic dust moving at colossal speed.
Academician Vernadsky confirmed his hypothesis with the appearance these days of a large number of luminous clouds moving at high altitudes at a speed of 300-350 km per hour. This hypothesis could also explain the fact that the trees surrounding the meteorite crater remained standing, while those located further were knocked down by the blast wave.
In addition to the Tunguska meteorite, a number of craters of meteorite origin are known. The first of these craters to be surveyed can be called the Arizona crater in Devil's Canyon. It is interesting that not only fragments of an iron meteorite were found near it, but also small diamonds formed from carbon from high temperature and pressure during the fall and explosion of the meteorite.
In addition to the indicated craters, indicating the fall of huge meteorites weighing tens of tons, there are also smaller craters: in Australia, on the island of Ezel and a number of others.
In addition to large meteorites, quite a lot of smaller ones fall out every year - weighing from 10-12 grams to 2-3 kilograms.
If the Earth were not protected by a thick atmosphere, we would be bombarded every second by tiny cosmic particles traveling at speeds faster than bullets.
There are billions of stars and planets in the universe. And while a star is a glowing sphere of gas, planets like Earth are made up of solid elements. Planets form in clouds of dust that swirl around a newly formed star. In turn, the grains of this dust are composed of elements such as carbon, silicon, oxygen, iron and magnesium. But where do cosmic dust particles come from? A new study from the Niels Bohr Institute in Copenhagen shows that dust grains can not only form in giant supernova explosions, they can also survive the subsequent shock waves of various explosions that impact the dust.
A computer image of how cosmic dust is formed during supernova explosions. Source: ESO/M. Kornmesser
How cosmic dust was formed has long been a mystery to astronomers. The dust elements themselves form in flaming hydrogen gas in stars. Hydrogen atoms combine with each other to form increasingly heavier elements. As a result, the star begins to emit radiation in the form of light. When all the hydrogen is exhausted and it is no longer possible to extract energy, the star dies, and its shell flies into outer space, which forms various nebulae in which young stars can again be born. Heavy elements are formed primarily in supernovae, the progenitors of which are massive stars that die in a giant explosion. But how single elements clump together to form cosmic dust remained a mystery.
“The problem was that even if dust were formed along with elements in supernova explosions, the event itself is so violent that these small grains simply should not survive. But cosmic dust exists, and its particles can be of completely different sizes. Our research sheds light on this problem,” Professor Jens Hjort, head of the Center for Dark Cosmology at the Niels Bohr Institute.
A Hubble telescope image of the unusual dwarf galaxy that produced the bright supernova SN 2010jl. The image was taken before its appearance, so the arrow shows its progenitor star. The star that exploded was very massive, approximately 40 solar masses. Source: ESO
In cosmic dust studies, scientists are observing supernovae using the X-shooter astronomical instrument at the Very Large Telescope (VLT) facility in Chile. It has amazing sensitivity, and the three spectrographs included in it. can observe the entire range of light at once, from ultraviolet and visible to infrared. Hjorth explains that they initially expected a “proper” supernova explosion to occur. And so, when this happened, a campaign to monitor it began. The observed star was unusually bright, 10 times brighter than the average supernova, and its mass was 40 times that of the Sun. In total, observing the star took the researchers two and a half years.
“Dust absorbs light, and using our data we were able to calculate a function that could tell us about the amount of dust, its composition and grain size. We found something truly exciting in the results,” Krista Gaul.
The first step toward the formation of cosmic dust is a mini-explosion in which a star ejects material containing hydrogen, helium and carbon into space. This gas cloud becomes a kind of shell around the star. A few more such flashes and the shell becomes denser. Finally, the star explodes and a dense gas cloud completely envelops its core.
“When a star explodes, the shock wave hits the dense gas cloud like a brick hitting a concrete wall. All this happens in the gas phase at incredible temperatures. But the place where the explosion hit becomes dense and cools down to 2000 degrees Celsius. At this temperature and density, the elements can nucleate and form solid particles. We found dust grains as small as one micron, which is very large for these elements. With such dimensions, they will be able to survive their future journey through the galaxy.”
Thus, scientists believe that they have found the answer to the question of how cosmic dust is formed and lives.
Supernova SN2010jl Photo: NASA/STScI
For the first time, astronomers observed in real time the formation of cosmic dust in the immediate vicinity of a supernova, which allowed them to explain this mysterious phenomenon that occurs in two stages. The process begins soon after the explosion, but continues for many years, the researchers write in the journal Nature.
We are all made of star dust, elements that are the building material for new celestial bodies. Astronomers have long assumed that this dust is formed when stars explode. But how exactly this happens and how dust particles are not destroyed in the vicinity of galaxies where active activity is taking place has remained a mystery until now.
This question was first clarified by observations made using the Very Large Telescope at the Paranal Observatory in northern Chile. An international research team led by Christa Gall from the Danish University of Aarhus examined a supernova that occurred in 2010 in a galaxy 160 million light years away. Researchers spent months and early years observing catalog number SN2010jl in visible and infrared light using the X-Shooter spectrograph.
“When we combined the observational data, we were able to make the first measurement of the absorption of different wavelengths in the dust around the supernova,” Gall explains. “This allowed us to learn more about this dust than was previously known.” This made it possible to study in more detail the different sizes of dust grains and their formation.
Dust in the immediate vicinity of a supernova occurs in two stages. Photo: © ESO/M. Kornmesser
As it turns out, dust particles larger than a thousandth of a millimeter form in the dense material around the star relatively quickly. The sizes of these particles are surprisingly large for cosmic dust grains, making them resistant to destruction by galactic processes. “Our evidence of the formation of large dust particles shortly after a supernova explosion means that there must be a fast and efficient way for them to form,” adds co-author Jens Hjorth from the University of Copenhagen. “But we do not yet understand how exactly this happens.”
However, astronomers already have a theory based on their observations. Based on it, dust formation occurs in 2 stages:
- The star pushes material into its surroundings shortly before exploding. Then the supernova shock wave comes and spreads, behind which a cool and dense shell of gas is created - an environment in which dust particles from the previously ejected material can condense and grow.
- In the second stage, several hundred days after the supernova explosion, material that was ejected by the explosion itself is added and an accelerated process of dust formation occurs.
“Recently, astronomers have discovered a lot of dust in the remnants of supernovae that arose after the explosion. However, they also found evidence of a small amount of dust that actually originated from the supernova itself. New observations explain how this apparent contradiction may be resolved,” writes Christa Gall in conclusion.
Scientists at the University of Hawaii made a sensational discovery - cosmic dust contains organic matter, including water, which confirms the possibility of transferring various forms of life from one galaxy to another. Comets and asteroids traveling through space regularly bring masses of stardust into the atmosphere of planets. Thus, interstellar dust acts as a kind of “transport” that can deliver water and organic matter to Earth and other planets of the solar system. Perhaps, once upon a time, a stream of cosmic dust led to the emergence of life on Earth. It is possible that life on Mars, the existence of which causes much controversy in scientific circles, could have arisen in the same way.
The mechanism of water formation in the structure of cosmic dust
As they move through space, the surface of interstellar dust particles is irradiated, which leads to the formation of water compounds. This mechanism can be described in more detail as follows: hydrogen ions present in solar vortex flows bombard the shell of cosmic dust grains, knocking out individual atoms from the crystalline structure of a silicate mineral - the main building material of intergalactic objects. As a result of this process, oxygen is released, which reacts with hydrogen. Thus, water molecules containing inclusions of organic substances are formed.
Colliding with the surface of the planet, asteroids, meteorites and comets bring a mixture of water and organic matter to its surface
What cosmic dust- a companion of asteroids, meteorites and comets, carries molecules of organic carbon compounds, it was known before. But it has not been proven that stardust also transports water. Only now have American scientists discovered for the first time that organic matter transported by interstellar dust particles together with water molecules.
How did water get to the Moon?
The discovery of scientists from the United States may help lift the veil of mystery over the mechanism of formation of strange ice formations. Despite the fact that the surface of the Moon is completely dehydrated, an OH compound was discovered on its shadow side using sounding. This find indicates the possible presence of water in the depths of the Moon.
The far side of the Moon is completely covered with ice. Perhaps it was with cosmic dust that water molecules reached its surface many billions of years ago
Since the era of the Apollo rovers in lunar exploration, when lunar soil samples were brought to Earth, scientists have come to the conclusion that sunny wind causes changes in the chemical composition of stardust covering the surfaces of planets. There was still debate about the possibility of the formation of water molecules in the thickness of cosmic dust on the Moon, but the analytical research methods available at that time were unable to either prove or disprove this hypothesis.
Cosmic dust is a carrier of life forms
Due to the fact that water is formed in a very small volume and is localized in a thin shell on the surface cosmic dust, only now it has become possible to see it using a high-resolution electron microscope. Scientists believe that a similar mechanism for the movement of water with molecules of organic compounds is possible in other galaxies where it revolves around the “parent” star. In their further research, scientists expect to identify in more detail which inorganic and organic matter carbon-based are present in the structure of stardust.
Interesting to know! An exoplanet is a planet that is located outside the solar system and orbits a star. At the moment, about 1000 exoplanets have been visually discovered in our galaxy, forming about 800 planetary systems. However, indirect detection methods indicate the existence of 100 billion exoplanets, of which 5-10 billion have parameters similar to the Earth, that is, they are. A significant contribution to the mission of searching for planetary groups similar to the Solar System was made by the Kepler astronomical telescope satellite, launched into space in 2009, together with the Planet Hunters program.
How could life originate on Earth?
It is very likely that comets traveling through space at high speeds are capable of creating enough energy when colliding with a planet to begin the synthesis of more complex organic compounds, including amino acid molecules, from ice components. A similar effect occurs when a meteorite collides with the icy surface of a planet. The shock wave creates heat, which triggers the formation of amino acids from individual molecules of cosmic dust processed by the solar wind.
Interesting to know! Comets are composed of large blocks of ice formed by the condensation of water vapor during the early creation of the solar system, approximately 4.5 billion years ago. In their structure, comets contain carbon dioxide, water, ammonia, and methanol. These substances, during the collision of comets with the Earth, at an early stage of its development, could produce a sufficient amount of energy for the production of amino acids - building proteins necessary for the development of life.
Computer modeling has demonstrated that icy comets that crashed onto the Earth's surface billions of years ago may have contained prebiotic mixtures and simple amino acids such as glycine, from which life on Earth subsequently originated.
The amount of energy released during the collision of a celestial body and a planet is sufficient to trigger the formation of amino acids
Scientists have discovered that icy bodies with identical organic compounds found in comets can be found inside the solar system. For example, Enceladus, one of the satellites of Saturn, or Europa, a satellite of Jupiter, contain in their shell organic matter, mixed with ice. Hypothetically, any bombardment of satellites by meteorites, asteroids or comets could lead to the emergence of life on these planets.
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During 2003–2008 A group of Russian and Austrian scientists, with the participation of Heinz Kohlmann, a famous paleontologist and curator of the Eisenwurzen National Park, studied the catastrophe that occurred 65 million years ago, when more than 75% of all organisms on Earth, including dinosaurs, became extinct. Most researchers believe that the extinction was associated with the impact of an asteroid, although there are other points of view.
Traces of this catastrophe in geological sections are represented by a thin layer of black clay with a thickness of 1 to 5 cm. One of these sections is located in Austria, in the Eastern Alps, in the National Park near the small town of Gams, located 200 km southwest of Vienna. As a result of studying samples from this section using a scanning electron microscope, particles of unusual shape and composition were discovered, which do not form under terrestrial conditions and are classified as cosmic dust.
Space dust on Earth
For the first time, traces of cosmic matter on Earth were discovered in red deep-sea clays by an English expedition that explored the bottom of the World Ocean on the Challenger ship (1872–1876). They were described by Murray and Renard in 1891. At two stations in the South Pacific Ocean, samples of ferromanganese nodules and magnetic microspheres with a diameter of up to 100 microns, which were later called “cosmic balls,” were recovered from a depth of 4300 m. However, the iron microspheres recovered by the Challenger expedition have been studied in detail only in recent years. It turned out that the balls consist of 90% metallic iron, 10% nickel, and their surface is covered with a thin crust of iron oxide.
Rice. 1. Monolith from the Gams 1 section, prepared for sampling. Latin letters indicate layers of different ages. The transitional layer of clay between the Cretaceous and Paleogene periods (age about 65 million years), in which an accumulation of metal microspheres and plates was found, is marked with the letter “J”. Photo by A.F. Gracheva
The discovery of mysterious balls in deep-sea clays is, in fact, the beginning of the study of cosmic matter on Earth. However, an explosion of interest among researchers in this problem occurred after the first launches of spacecraft, with the help of which it became possible to select lunar soil and samples of dust particles from different parts of the Solar System. The works of K.P. were also important. Florensky (1963), who studied the traces of the Tunguska disaster, and E.L. Krinov (1971), who studied meteoric dust at the site of the fall of the Sikhote-Alin meteorite.
Researchers' interest in metal microspheres has led to their discovery in sedimentary rocks of different ages and origins. Metal microspheres have been found in the ice of Antarctica and Greenland, in deep ocean sediments and manganese nodules, in the sands of deserts and coastal beaches. They are often found in and near meteorite craters.
In the last decade, metal microspheres of extraterrestrial origin have been found in sedimentary rocks of different ages: from the Lower Cambrian (about 500 million years ago) to modern formations.
Data on microspheres and other particles from ancient deposits make it possible to judge the volumes, as well as the uniformity or unevenness of the supply of cosmic matter to the Earth, changes in the composition of particles arriving on the Earth from space, and the primary sources of this substance. This is important because these processes influence the development of life on Earth. Many of these questions are still far from being resolved, but the accumulation of data and their comprehensive study will undoubtedly make it possible to answer them.
It is now known that the total mass of dust circulating within the Earth’s orbit is about 1015 tons. From 4 to 10 thousand tons of cosmic matter fall onto the Earth’s surface annually. 95% of the matter falling on the Earth's surface consists of particles with a size of 50–400 microns. The question of how the rate of arrival of cosmic matter on Earth changes over time remains controversial to this day, despite many studies conducted in the last 10 years.
Based on the size of cosmic dust particles, interplanetary cosmic dust itself is currently distinguished with a size of less than 30 microns and micrometeorites larger than 50 microns. Even earlier, E.L. Krinov proposed calling the smallest fragments of a meteorite body melted from the surface micrometeorites.
Strict criteria for distinguishing between cosmic dust and meteorite particles have not yet been developed, and even using the example of the Gams section we studied, it is shown that metal particles and microspheres are more diverse in shape and composition than provided by existing classifications. The almost perfect spherical shape, metallic luster and magnetic properties of the particles were considered as evidence of their cosmic origin. According to geochemist E.V. Sobotovich, “the only morphological criterion for assessing the cosmogenicity of the material under study is the presence of melted balls, including magnetic ones.” However, in addition to the form, which is extremely diverse, the chemical composition of the substance is fundamentally important. Researchers have found that, along with microspheres of cosmic origin, there are a huge number of balls of a different origin - associated with volcanic activity, bacterial activity or metamorphism. There is evidence that ferrous microspheres of volcanogenic origin are much less likely to have an ideal spherical shape and, moreover, have an increased admixture of titanium (Ti) (more than 10%).
A Russian-Austrian group of geologists and a film crew from Vienna Television at the Gams section in the Eastern Alps. In the foreground - A.F. Grachev
Origin of cosmic dust
The origin of cosmic dust is still a subject of debate. Professor E.V. Sobotovich believed that cosmic dust could represent the remnants of the original protoplanetary cloud, which B.Yu. objected to in 1973. Levin and A.N. Simonenko, believing that finely dispersed matter could not survive for long (Earth and Universe, 1980, No. 6).
There is another explanation: the formation of cosmic dust is associated with the destruction of asteroids and comets. As noted by E.V. Sobotovich, if the amount of cosmic dust entering the Earth does not change over time, then B.Yu. is right. Levin and A.N. Simonenko.
Despite the large number of studies, the answer to this fundamental question cannot currently be given, because there are very few quantitative estimates, and their accuracy is debatable. Recently, data from isotopic studies of cosmic dust particles sampled in the stratosphere under the NASA program suggest the existence of particles of presolar origin. Minerals such as diamond, moissanite (silicon carbide) and corundum were found in this dust, which, based on carbon and nitrogen isotopes, allow their formation to be dated back to before the formation of the Solar System.
The importance of studying cosmic dust in a geological context is obvious. This article presents the first results of a study of cosmic matter in the transition layer of clays at the Cretaceous-Paleogene boundary (65 million years ago) from the Gams section, in the Eastern Alps (Austria).
General characteristics of the Gams section
Particles of cosmic origin were obtained from several sections of the transition layers between the Cretaceous and Paleogene (in German-language literature - the K/T boundary), located near the Alpine village of Gams, where the river of the same name opens this boundary in several places.
In the Gams 1 section, a monolith was cut out of the outcrop, in which the K/T boundary is very well expressed. Its height is 46 cm, width is 30 cm at the bottom and 22 cm at the top, thickness is 4 cm. For a general study of the section, the monolith was divided 2 cm apart (from bottom to top) into layers designated by letters of the Latin alphabet (A, B ,C...W), and within each layer, also every 2 cm, markings are made with numbers (1, 2, 3, etc.). The transition layer J at the K/T boundary was studied in more detail, where six sublayers with a thickness of about 3 mm were identified.
The research results obtained in the Gams 1 section were largely repeated in the study of another section, Gams 2. The complex of studies included the study of thin sections and monomineral fractions, their chemical analysis, as well as X-ray fluorescence, neutron activation and X-ray structural analyses, isotope analysis of helium, carbon and oxygen, determination of the composition of minerals using a microprobe, magnetomineralogical analysis.
Variety of microparticles
Iron and nickel microspheres from the transition layer between the Cretaceous and Paleogene in the Gams section: 1 – Fe microsphere with a rough reticulate-lumpy surface (upper part of the transition layer J); 2 – Fe microsphere with a rough longitudinally parallel surface (lower part of the transition layer J); 3 – Fe microsphere with crystallographic cut elements and a rough cellular-mesh surface texture (layer M); 4 – Fe microsphere with a thin mesh surface (upper part of the transition layer J); 5 – Ni microsphere with crystallites on the surface (upper part of the transition layer J); 6 – aggregate of sintered Ni microspheres with crystallites on the surface (upper part of the transition layer J); 7 – aggregate of Ni microspheres with microdiamonds (C; upper part of the transition layer J); 8, 9 – characteristic forms of metal particles from the transition layer between the Cretaceous and Paleogene in the Gams section in the Eastern Alps.
In the transition layer of clay between two geological boundaries - Cretaceous and Paleogene, as well as at two levels in the overlying Paleocene deposits in the Gams section, many metal particles and microspheres of cosmic origin were found. They are significantly more diverse in shape, surface texture and chemical composition than anything hitherto known from transitional layers of clay of this age in other regions of the world.
In the Gams section, cosmic matter is represented by fine particles of various shapes, among which the most common are magnetic microspheres ranging in size from 0.7 to 100 microns, consisting of 98% pure iron. Such particles in the form of balls or microspherules are found in large quantities not only in layer J, but also higher, in Paleocene clays (layers K and M).
The microspheres are composed of pure iron or magnetite, some of them contain impurities of chromium (Cr), an alloy of iron and nickel (awareuite), and also pure nickel (Ni). Some Fe-Ni particles contain molybdenum (Mo) impurities. All of them were discovered for the first time in the transition layer of clay between the Cretaceous and Paleogene.
Never before have we encountered particles with a high nickel content and a significant admixture of molybdenum, microspheres containing chromium, and pieces of helical iron. In addition to metal microspheres and particles, Ni-spinel, microdiamonds with microspheres of pure Ni, as well as torn plates of Au and Cu, which were not found in the underlying and overlying deposits, were found in the transition layer of clay in Gamsa.
Characteristics of microparticles
Metal microspheres in the Gams section are present at three stratigraphic levels: iron particles of various shapes are concentrated in the transition clay layer, in the overlying fine-grained sandstones of layer K, and the third level is formed by siltstones of layer M.
Some spheres have a smooth surface, others have a network-lumpy surface, and others are covered with a network of small polygonal or a system of parallel cracks extending from one main crack. They are hollow, shell-shaped, filled with clay mineral, and may have an internal concentric structure. Metal particles and Fe microspheres occur throughout the transition clay layer, but are mainly concentrated in the lower and middle horizons.
Micrometeorites are melted particles of pure iron or iron-nickel alloy Fe-Ni (avaruite); their sizes range from 5 to 20 microns. Numerous awaruite particles are confined to the upper level of the transition layer J, while purely ferruginous particles are present in the lower and upper parts of the transition layer.
Particles in the form of plates with a transversely lumpy surface consist only of iron, their width is 10–20 µm, their length is up to 150 µm. They are slightly arcuate and occur at the base of the transition layer J. In its lower part, Fe-Ni plates with an admixture of Mo are also found.
Plates made of an alloy of iron and nickel have an elongated shape, slightly curved, with longitudinal grooves on the surface, dimensions range in length from 70 to 150 microns with a width of about 20 microns. They are more often found in the lower and middle parts of the transition layer.
Ferrous plates with longitudinal grooves are identical in shape and size to plates of the Ni-Fe alloy. They are confined to the lower and middle parts of the transition layer.
Of particular interest are particles of pure iron, shaped like a regular spiral and bent in the shape of a hook. They are mainly composed of pure Fe, rarely a Fe-Ni-Mo alloy. Spiral iron particles occur in the upper part of the transition layer J and in the overlying sandstone layer (layer K). A spiral-shaped Fe-Ni-Mo particle was found at the base of the J transition layer.
In the upper part of the transition layer J there were several microdiamond grains sintered with Ni microspheres. Microprobe studies of nickel balls, carried out on two instruments (with wave and energy-dispersive spectrometers), showed that these balls consist of almost pure nickel under a thin film of nickel oxide. The surface of all nickel balls is dotted with clear crystallites with pronounced twins 1–2 μm in size. Such pure nickel in the form of balls with a well-crystallized surface is not found either in igneous rocks or in meteorites, where nickel necessarily contains a significant amount of impurities.
When studying a monolith from the Gams 1 section, balls of pure Ni were found only in the uppermost part of the transition layer J (in its uppermost part - a very thin sedimentary layer J 6, the thickness of which does not exceed 200 μm), and according to thermagnetic analysis, metallic nickel is present in transition layer, starting from sublayer J4. Here, along with Ni balls, diamonds were also discovered. In a layer removed from a cube with an area of 1 cm2, the number of diamond grains found is in the tens (with sizes ranging from fractions of microns to tens of microns), and nickel balls of the same size are in the hundreds.
Samples of the upper transition layer taken directly from the outcrop revealed diamonds with fine nickel particles on the surface of the grain. It is significant that when studying samples from this part of layer J, the presence of the mineral moissanite was also revealed. Previously, microdiamonds were found in the transition layer at the Cretaceous-Paleogene boundary in Mexico.
Finds in other areas
Gams microspheres with a concentric internal structure are similar to those obtained by the Challenger expedition in deep-sea clays of the Pacific Ocean.
Iron particles of irregular shape with melted edges, as well as in the form of spirals and curved hooks and plates, are very similar to the destruction products of meteorites falling to the Earth; they can be considered as meteorite iron. Particles of awaruite and pure nickel can also be included in this category.
The curved iron particles are similar to the various shapes of Pele's tears - drops of lava (lapillas) that volcanoes eject in a liquid state from the vent during eruptions.
Thus, the transitional layer of clay in Gamsa has a heterogeneous structure and is clearly divided into two parts. The lower and middle parts are dominated by iron particles and microspheres, while the upper part of the layer is enriched in nickel: awaruite particles and nickel microspheres with diamonds. This is confirmed not only by the distribution of iron and nickel particles in the clay, but also by chemical and thermomagnetic analysis data.
A comparison of the data from thermomagnetic analysis and microprobe analysis indicates extreme heterogeneity in the distribution of nickel, iron and their alloy within layer J, however, according to the results of thermomagnetic analysis, pure nickel is recorded only from layer J4. It is also noteworthy that spiral-shaped iron is found predominantly in the upper part of layer J and continues to be found in the overlying layer K, where, however, there are few particles of Fe, Fe-Ni of isometric or lamellar shape.
We emphasize that such a clear differentiation in iron, nickel, and iridium, manifested in the transition layer of clay in Gamsa, is also found in other areas. Thus, in the American state of New Jersey, in the transitional (6 cm) spherulic layer, the iridium anomaly sharply manifested itself at its base, and impact minerals are concentrated only in the upper (1 cm) part of this layer. In Haiti, at the Cretaceous-Paleogene boundary and in the uppermost part of the spherulic layer, a sharp enrichment of Ni and impact quartz is noted.
Background phenomenon for the Earth
Many features of the found Fe and Fe-Ni spherules are similar to the spherules discovered by the Challenger expedition in deep-sea clays of the Pacific Ocean, in the area of the Tunguska catastrophe and the fall sites of the Sikhote-Alin meteorite and the Nio meteorite in Japan, as well as in sedimentary rocks of different ages from many areas of the world. Except for the areas of the Tunguska catastrophe and the fall of the Sikhote-Alin meteorite, in all other cases the formation of not only spherules, but also particles of various morphologies, consisting of pure iron (sometimes containing chromium) and a nickel-iron alloy, has no connection with the impact event. We consider the appearance of such particles as a result of the fall of cosmic interplanetary dust onto the Earth's surface - a process that has continuously continued since the formation of the Earth and represents a kind of background phenomenon.
Many particles studied in the Gams section are close in composition to the bulk chemical composition of the meteorite substance at the site of the fall of the Sikhote-Alin meteorite (according to E.L. Krinov, it is 93.29% iron, 5.94% nickel, 0.38% cobalt).
The presence of molybdenum in some particles is not unexpected, since many types of meteorites include it. The molybdenum content in meteorites (iron, stony and carbonaceous chondrites) ranges from 6 to 7 g/t. The most important was the discovery of molybdenite in the Allende meteorite in the form of an inclusion in a metal alloy of the following composition (wt.%): Fe – 31.1, Ni – 64.5, Co – 2.0, Cr – 0.3, V – 0.5, P – 0.1. It should be noted that native molybdenum and molybdenite were also found in lunar dust sampled by the Luna-16, Luna-20 and Luna-24 automatic stations.
The first found balls of pure nickel with a well-crystallized surface are not known either in igneous rocks or in meteorites, where nickel necessarily contains a significant amount of impurities. This structure of the surface of nickel balls could arise in the event of an asteroid (meteorite) fall, which led to the release of energy, which made it possible not only to melt the material of the fallen body, but also to evaporate it. Metal vapors could be raised by an explosion to a great height (probably tens of kilometers), where crystallization occurred.
Particles consisting of awaruite (Ni3Fe) were found along with nickel metal balls. They belong to meteoric dust, and melted iron particles (micrometeorites) should be considered as “meteorite dust” (according to the terminology of E.L. Krinov). The diamond crystals found together with the nickel balls probably resulted from ablation (melting and evaporation) of the meteorite from the same vapor cloud during its subsequent cooling. It is known that synthetic diamonds are obtained by spontaneous crystallization from a solution of carbon in a melt of metals (Ni, Fe) above the graphite–diamond phase equilibrium line in the form of single crystals, their intergrowths, twins, polycrystalline aggregates, framework crystals, needle-shaped crystals, irregular grains. Almost all of the listed typomorphic features of diamond crystals were found in the studied sample.
This allows us to conclude that the processes of diamond crystallization in a cloud of nickel-carbon vapor upon cooling and spontaneous crystallization from a carbon solution in a nickel melt in experiments are similar. However, a final conclusion about the nature of diamond can be made after detailed isotopic studies, for which it is necessary to obtain a sufficiently large amount of the substance.
Thus, the study of cosmic matter in the transitional clay layer at the Cretaceous-Paleogene boundary showed its presence in all parts (from layer J1 to layer J6), but signs of an impact event are recorded only from layer J4, whose age is 65 million years. This layer of cosmic dust can be compared with the time of the death of dinosaurs.
A.F. GRACHEV Doctor of Geological and Mineralogical Sciences, V.A. TSELMOVICH Candidate of Physical and Mathematical Sciences, Institute of Physics of the Earth RAS (IPZ RAS), O.A. KORCHAGIN Candidate of Geological and Mineralogical Sciences, Geological Institute of the Russian Academy of Sciences (GIN RAS).
Magazine "Earth and Universe" No. 5 2008.
