At about seven o'clock in the morning on June 17 (30), 1908, a large fireball flew over the territory of the Yenisei basin from the south-east to the north-west. The flight ended with an explosion at 07:00 14.5 ± 0.8 minutes local time (0:00 14.5 minutes GMT) at an altitude of 7-10 km above the unpopulated area of the taiga - in the basin of the Podkamennaya Tunguska River (about 60 km to the north and 20 km west of the village of Vanavara, Evenki District of Krasnoyarsk Territory).
According to eyewitnesses, for a few seconds a dazzling bright ball-fireball was observed in the sky, the flight of which was accompanied by a sound that resembled thunder. A powerful dust trail remained on the path of the car's movement, which remained for several hours. After the light phenomena, a super-powerful explosion was heard over the deserted taiga. In a matter of seconds, a blast wave within a radius of about 40 kilometers felled the forest, destroyed animals, and suffered people. At the same time, under the influence of light radiation, the taiga flared up for tens of kilometers around.
In many villages, shaking of the soil and buildings was felt, window panes were breaking, household utensils fell from shelves. Many people, as well as pets, were knocked down by the air wave. The inhabitants of Vanavara and those few nomadic Evenks who were in the taiga became involuntary witnesses of the cosmic catastrophe. The blast wave lifted the plague into the air, scattered the dogs, during the fall of the Tungus body, about a thousand deer were killed among the Evenks, and they themselves suffered.
A hypothetical body, probably of a cometary origin, or part of a cosmic body that underwent destruction, which, presumably, caused a powerful air explosion of 40-50 megatons, which corresponds to the energy of the most powerful exploded hydrogen bomb.
The explosion on Tunguska was heard 800 km from the epicenter, the blast wave was recorded by observatories around the world, including in the Western Hemisphere. As a result of the explosion, trees were toppled over an area of more than 2000 km², window panes in houses were shattered several hundred kilometers from the epicenter of the explosion.
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Soon after the explosion, a magnetic storm began, which lasted for 5 hours. Unusual atmospheric light effects that preceded the explosion peaked on July 1, after which they began to decline (some of them persisted until the end of July). For several days, an intense glow of the sky and glowing clouds were observed in the territory from the Atlantic to central Siberia. The radiance of the sky was so strong that many residents could not sleep. The clouds, formed at an altitude of about 80 kilometers, intensely reflected the sun's rays, thereby creating the effect of bright nights even where they had not been observed before. In a number of cities, a small print newspaper could be read freely at night, and a photograph of the seaport was obtained in Greenwich at midnight. This phenomenon continued for several more nights.
The explosion was unlikely to be point-like, so we can only talk about the projection of the coordinates of a singular point called the epicenter. Kulik L. A. the radial felling of trees determined the geographic coordinates of the epicenter in the region of 60 ° 54′07 ″ N. sh. 101 ° 54′16 ″ in. etc.
In 1921, with the support of Academicians V. I. Vernadsky and A. E. Fersman, mineralogists L. A. Kulik (August 19 (September 1) 1883 - April 14, 1942), a Soviet specialist in mineralogy the study of meteorites, and P. L. Dravert organized the first Soviet expedition to check the incoming reports of meteorite falling on the territory of the country. In 1927 - 1939. Kulik L. A. organized and headed six expeditions to the area of the disaster (according to other sources, four expeditions). L. A. Kulik discovered the radial nature of the solid felling of the forest at the place of the fall, tried to find the remnants of the meteorite, organized aerial photography of the place of the fall, collected information from the witnesses of the fall.
The 1921 expedition only collected eyewitness accounts, which made it possible to more accurately determine the place of the event where the 1927 expedition went. She already made more significant finds: for example, it was discovered that a large area of forest had been tumbled down at the place of the supposed fall of the meteorite, and in the place that was supposed to be the epicenter of the explosion, the forest remained standing, and there were no traces of a meteorite crater.
In 1928-1930, the Academy of Sciences of the USSR conducted two more expeditions under the leadership of Kulik, and in 1938-1939 - aerial photography of the central part of the region of the fallen forest on an area of 250 km² was carried out.
Kulik remained a supporter of the hypothesis of the meteoric nature of the phenomenon (although he was forced to abandon the idea of a solid meteorite falling of a significant mass in favor of the idea of its possible destruction during the fall). He discovered thermokarst pits, which he mistook for small meteorite craters. During his expeditions, Kulik tried to find the remnants of the meteorite, organized aerial photography of the crash site, and collected information about the fall of the meteorite from witnesses of the incident.
The new expedition being prepared by L. A. Kulik to the place of the fall of the Tunguska meteorite in 1941 did not take place due to the outbreak of the Great Patriotic War. The results of the long-term work of L. A. Kulik, who died in the Great Patriotic War, to study the problem of the Tunguska meteorite, were summed up in 1949 by his student and member of his expeditions E. L. Krinov in his book "The Tunguska meteorite".
The substance of the hypothetical Tunguska meteorite was not found in any significant amount; however, microscopic silicate and magnetite spheres were discovered, as well as an increased content of some elements, indicating a possible cosmic origin of the substance.
Researchers did not find a typical meteoric crater, although later, over the long years of searching for fragments of the Tunguska meteorite, members of various expeditions found a total of 12 wide conical holes in the territory of the disaster. To what depth they go, no one knows, since no one even tried to study them. It was found that around the place where the Tunguska meteorite fell, the forest fanned out from the center, and in the center, some of the trees remained standing on the root, but without branches and bark. "It looked like a forest of telephone poles."
Subsequent expeditions noticed that the area of the fallen forest was shaped like a butterfly. Computer modeling of the shape of this area, taking into account all the circumstances of the fall, showed that the explosion did not occur when a body collided with the earth's surface, but even before that, in the air, at an altitude of 5-10 km, and the weight of the space alien was estimated at 5 million tons.
Diagram of forest felling around the epicenter of the Tunguska explosion along the “butterfly” with the axis of symmetry AB, taken as the main direction of the trajectory of the Tunguska meteorite.
Since 1958, the study of the epicenter area was resumed, and the Committee on Meteorites of the USSR Academy of Sciences conducted three expeditions under the leadership of the Soviet geochemist Kirill Florensky: in 1958, 1961 and 1962. Important facts were obtained concerning the nature of the Tunguska explosion. At the same time, studies were started by amateur enthusiasts, united in the so-called complex amateur expedition (CSP).
During the 1962 expedition, researchers took aerial photographs of the crash site from a helicopter. Instead of looking for large fragments of a meteorite, as Leonid Kulik did, a group of scientists led by Florensky sifted through the soil in search of microscopic particles that could be scattered during the combustion and grinding of the Tunguska object. Their search was fruitful. Scientists found a narrow strip of cosmic dust, 250 km long, extending to the northwest of the scene and consisted of magnetite (magnetic iron ore) and glassy droplets of molten rock. The expedition found thousands of particles of metals and silicates, which indicated the heterogeneity of the composition of the Tunguska object. It is believed that the low-density rocky composition with the content of iron inclusions is typical of space debris, in particular,meteors (“shooting stars”), which themselves are composed of cometary dust. The particles scattered northwest of the Tunguska explosion were, in the opinion of Florensky's group, the evaporated remnants of the comet's head.
These genuine samples of the Tunguska site were enough to “settle the dispute once and for all”. In 1963, Florensky wrote an article about his expeditions in the Sky & Telescope magazine. The article was titled "Did a comet hit the Earth in 1908?" Comet theory has always dominated among astronomers. In his article, Florensky stressed that "now this point of view has found its confirmation."
Florensky's expedition carefully examined the site of the disaster for the presence of radiation. His reports stated that the only traces of radiation on the trees of the massif of the Evenk taiga where the explosion took place were the radioactive fallout that fell on the trees after the nuclear tests. Florensky's group of scientists also examined in detail the process of accelerating forest growth at the site of the disaster, which some researchers considered genetic damage caused by radioactive radiation. Biologists concluded that there was a well-known phenomenon - the usual acceleration of growth after a fire.
In 2013, the journal Planetary and Space Science published the results of a study conducted by a group of Ukrainian, German and American scientists, which reported that microscopic samples discovered by Nikolai Kovalykh in 1978 in the Podkamennaya Tunguska area revealed the presence of lonsdaleite, troilite, taenite and sheibersite - minerals characteristic of diamond-bearing meteorites. At the same time, an employee of the Australian University Curtin Phil Bland drew attention to the fact that the studied samples showed a suspiciously low concentration of iridium (which is not typical for meteorites), and also that the peat where the samples were found was not dated 1908, which means that the rocks could have hit the Earth earlier or later than the famous explosion.
The Tunguska catastrophe is one of the most well-studied, but at the same time, the most mysterious phenomena of the 20th century. Dozens of expeditions, hundreds of scientific articles, thousands of researchers could only increase their knowledge about it, but they did not manage to clearly answer a simple question: what was it?
Until now, none of the hypotheses explaining all the essential features of the phenomenon has become generally accepted.