What process is responsible for the formation of cosmic dust? Fallout of cosmic dust on the Earth's surface

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 well-known gases, also includes solid particles - dust.

Basically, it consists of soil particles rising up under the influence of 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 cube. cm of air in cities reaches 100 thousand pieces, while in the clean mountain air they contain only a few hundred. However, dust of terrestrial origin rises to relatively small heights - up to 10 km. Volcanic dust can reach a height of 40-50 km.

Origin of cosmic dust

The presence of dust clouds at a height significantly exceeding 100 km has been established. These are the so-called "silver clouds", consisting of cosmic dust.

The origin of cosmic dust is extremely diverse: it includes the remains of decayed 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 earth. The presence of such cosmic dust has been detected on high snowy peaks.

meteorites

In addition to this slowly settling cosmic dust, hundreds of millions of meteors burst into the confines of our atmosphere every day - what we call "shooting stars". Flying at an cosmic speed of hundreds of kilometers per second, they burn out from friction against 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 exceptionally large specimens that reach the surface of the earth. Thus, the fall of the large Tunguska meteorite at 5 am on June 30, 1908 is known, accompanied by a number of seismic phenomena noted even in Washington (9 thousand km from the place of impact) and indicating the power of the explosion during the fall of the meteorite. Professor Kulik, who examined the meteorite impact site with exceptional courage, found a thicket of windbreak surrounding the impact site within a radius of hundreds of kilometers. Unfortunately, the meteorite was not found. An employee of the British Museum Kirpatrick made a special trip to the USSR in 1932, but did not even get to the place where the meteorite fell. However, he confirmed the assumption of Professor Kulik, who estimated the mass of the fallen meteorite at 100-120 tons.

Space dust cloud

The hypothesis of academician V. I. Vernadsky is interesting, who considered it possible that not a meteorite could fall, but a huge cloud of cosmic dust moving at an enormous speed.

Academician Vernadsky confirmed his hypothesis by the appearance these days of a large number of luminous clouds moving at high altitude 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 also known. The first of these surveyed craters can be called the Arizona crater in the "Devil's Canyon". Interestingly, 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 a meteorite.
In addition to these craters, which testify to the fall of huge meteorites weighing tens of tons, there are also smaller craters: in Australia, on Ezel Island and a number of others.

In addition to large meteorites, quite a lot of smaller ones fall annually - weighing from 10-12 grams to 2-3 kilograms.

If the Earth were not protected by a dense atmosphere, every second we would be bombarded by the smallest cosmic particles, rushing at a speed exceeding the speed of a bullet.

COSMIC DUST, solid particles with characteristic sizes from about 0.001 microns to about 1 microns (and possibly up to 100 microns or more in the interplanetary medium and protoplanetary disks), found in almost all astronomical objects: from the solar system to very distant galaxies and quasars . Dust characteristics (particle concentration, chemical composition, particle size, etc.) vary significantly from one object to another, even for objects of the same type. Cosmic dust scatters and absorbs incident radiation. Scattered radiation with the same wavelength as the incident radiation propagates in all directions. The radiation absorbed by the dust grain is transformed into thermal energy, and the particle usually radiates in a longer wavelength region of the spectrum compared to the incident radiation. Both processes contribute to extinction - the attenuation of the radiation of celestial bodies by dust located on the line of sight between the object and the observer.

Dust objects are studied in almost the entire range of electromagnetic waves - from X-ray to millimeter. Electric dipole radiation from rapidly rotating ultrafine particles appears to make some contribution to microwave radiation at frequencies of 10-60 GHz. An important role is played by laboratory experiments in which they measure the refractive indices, as well as the absorption spectra and scattering matrices of particles - analogues of cosmic dust particles, simulate the processes of formation and growth of refractory dust grains in the atmospheres of stars and protoplanetary disks, study the formation of molecules and the evolution of volatile dust components under conditions similar to those found in dark interstellar clouds.

Cosmic dust, which is in various physical conditions, is directly studied in the composition of meteorites that fell on the Earth's surface, in the upper layers of the Earth's atmosphere (interplanetary dust and the remains of small comets), during spacecraft flights to planets, asteroids and comets (near planetary and cometary dust) and beyond. limits of the heliosphere (interstellar dust). Ground and space remote observations of cosmic dust cover the Solar System (interplanetary, circumplanetary and cometary dust, dust near the Sun), the interstellar medium of our Galaxy (interstellar, circumstellar and nebular dust) and other galaxies (extragalactic dust), as well as very distant objects (cosmological dust).

Cosmic dust particles mainly consist of carbonaceous substances (amorphous carbon, graphite) and magnesium-iron silicates (olivines, pyroxenes). They condense and grow in the atmospheres of stars of late spectral classes and in protoplanetary nebulae, and then are ejected into the interstellar medium by radiation pressure. In interstellar clouds, especially dense ones, refractory particles continue to grow as a result of the accretion of gas atoms, as well as when particles collide and stick together (coagulation). This leads to the appearance of shells of volatile substances (mainly ice) and to the formation of porous aggregate particles. The destruction of dust grains occurs as a result of dispersion in shock waves arising after supernova explosions, or evaporation in the process of star formation that began in the cloud. The remaining dust continues to evolve near the formed star and later manifests itself in the form of an interplanetary dust cloud or cometary nuclei. Paradoxically, dust around evolved (old) stars is “fresh” (recently formed in their atmosphere), and around young stars it is old (evolved as part of the interstellar medium). It is assumed that cosmological dust, possibly existing in distant galaxies, condensed in the ejecta of matter after the explosions of massive supernovae.

Lit. see at st. Interstellar dust.

Many people admire with delight the beautiful spectacle of the starry sky, one of the greatest creations of nature. In the clear autumn sky, it is clearly visible how a faintly luminous band called the Milky Way runs across the entire sky, having irregular outlines with different widths and brightness. If we look at the Milky Way, which forms our Galaxy, through a telescope, it turns out that this bright band breaks up into many faintly luminous stars, which, to the naked eye, merge into a continuous radiance. It is now established that the Milky Way consists not only of stars and star clusters, but also of gas and dust clouds.

Cosmic dust occurs in many space objects, where there is a rapid outflow of matter, accompanied by cooling. It manifests itself in infrared radiation hot stars Wolf-Rayet with a very powerful stellar wind, planetary nebulae, supernova shells and new stars. A large amount of dust exists in the cores of many galaxies (for example, M82, NGC253), from which there is an intense outflow of gas. The influence of cosmic dust is most pronounced during the radiation of a new star. A few weeks after the maximum brightness of the nova, a strong excess of radiation in the infrared range appears in its spectrum, caused by the appearance of dust with a temperature of about K. Further

Supernova SN2010jl Photo: NASA/STScI

For the first time, astronomers have observed the formation of cosmic dust in the immediate vicinity of a supernova in real time, allowing them to explain this mysterious phenomenon that occurs in two stages. The process begins shortly after the explosion but continues for many more years, the researchers write in the journal Nature.

We are all made up of stardust, of the 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 there is an active one, has so far remained a mystery.

This question was first clarified by observations made with the Very Large Telescope at the Paranal Observatory in northern Chile. An international research team led by Christa Gall (Christa Gall) from the Danish University of Aarhus investigated a supernova that occurred in 2010 in a galaxy 160 million light years away from us. The researchers observed with catalog number SN2010jl in the visible and infrared light ranges for months and first years 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.” Thus, it became possible to study in more detail the various sizes of dust particles and their formation.

Dust in the immediate vicinity of a supernova occurs in two stages. Photo: © ESO/M. Kornmesser

As it turned out, dust particles larger than a thousandth of a millimeter are formed in the dense material around the star relatively quickly. The sizes of these particles are surprisingly large for cosmic dust particles, which makes them resistant to destruction by galactic processes. "Our evidence of large dust particles occurring shortly after a supernova explosion means that there must be a fast and efficient way to form them," adds co-author Jens Hjorth of the University of Copenhagen. "But we don't yet understand exactly how this happens."

However, astronomers already have a theory based on their observations. Based on it, the formation of dust proceeds in 2 stages:

The star pushes material into its surrounding space shortly before the explosion. Then comes and spreads the supernova shock wave, behind which a cool and dense shell of gas is created - the environment into which dust particles from the previously ejected material can condense and grow.
In the second stage, several hundred days after the supernova explosion, the material that was ejected in the explosion itself is added and an accelerated process of dust formation occurs.

“Recently, astronomers have found a lot of dust in the remnants of supernovae that emerged after the explosion. However, they also found evidence for a small amount of dust that actually originated in the supernova itself. New observations explain how this seeming contradiction can be resolved," concludes Christa Gall.

Scientists at the University of Hawaii made a sensational discovery - space dust contains organic matter, including water, which confirms the possibility of transferring various life forms from one galaxy to another. Comets and asteroids plying in space regularly bring masses of stardust into the atmosphere of planets. Thus, interstellar dust acts as a kind of "transport" that can deliver water with organic matter to the Earth and to other planets of the solar system. Perhaps, once, the flow 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

In the process of moving 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 particles, knocking out individual atoms from the crystal 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 space dust- a companion of asteroids, meteorites and comets, carries molecules of organic carbon compounds, it was known before. But the fact that stardust also transports water has not been proven. Only now American scientists have discovered for the first time that organic matter carried by interstellar dust particles together with water molecules.

How did water get to the moon?

The discovery of scientists from the US 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 found on its shadow side using sounding. This find testifies in favor of the possible presence of water in the bowels of the moon.

The other side of the Moon is completely covered with ice. Perhaps it was with cosmic dust that water molecules hit its surface many billions of years ago.

Since the era of the Apollo lunar rovers in the exploration of the moon, when samples of lunar soil were delivered to Earth, scientists have come to the conclusion that sunny wind causes changes in the chemical composition of stellar dust that covers the surfaces of planets. The possibility of the formation of water molecules in the thickness of cosmic dust on the Moon was still debated then, but the analytical research methods available at that time were not able to either prove or disprove this hypothesis.

Space dust - the 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 space dust, only now it has become possible to see it with a high-resolution electron microscope. Scientists believe that a similar mechanism for the movement of water with molecules of organic compounds is also possible in other galaxies, where it revolves around the "parent" star. In their further studies, scientists intend to identify in more detail which inorganic and organic matter based on carbon are present in the structure of star dust.

Interesting to know! An exoplanet is a planet that is outside the solar system and revolves around a star. At the moment, about 1000 exoplanets have been visually detected 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 astronomical satellite-telescope Kepler, 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 speed are capable of creating enough energy when colliding with the planet to begin the synthesis of more complex organic compounds, including amino acid molecules, from the components of ice. A similar effect occurs when a meteorite collides with the icy surface of the planet. The shock wave creates heat, which triggers the formation of amino acids from individual molecules of space dust, processed by the solar wind.

Interesting to know! Comets are made up of large blocks of ice formed by the condensation of water vapor during the early creation of the solar system, about 4.5 billion years ago. Comets contain carbon dioxide, water, ammonia, and methanol in their structure. These substances during the collision of comets with the Earth, at an early stage of its development, could produce enough energy to produce amino acids - the building proteins necessary for the development of life.

Computer simulations have shown that icy comets that crashed on the Earth's surface billions of years ago may have contained prebiotic mixtures and simple amino acids like glycine, from which life on Earth subsequently originated.

The amount of energy released during the collision of a celestial body and a planet is enough to start the process of formation of amino acids

Scientists have found 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 can lead to the emergence of life on these planets.

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