Trees knocked over by the Tunguska blast. Photograph from Kulik's 1927 expedition

The Tunguska Event, sometimes called the Tunguska explosion, was a massive explosion that occurred near the Podkamennaya (Lower Stony) Tunguska River in what is now Krasnoyarsk Krai of Russia, at around 7:14 a. An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release The Podkamennaya Tunguska (Подкаменная Тунгуска literally Substone Tunguska) is a river in Krasnoyarsk Krai, Russia; it is a right Krasnoyarsk Krai (Красноя́рский край Krasnoyarsky kray; not to be confused with Krasnodar Krai) is a federal subject of Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending m. ^[1] (0:14 UT, 7:02 a. m. local solar time^[2]) on June 30, 1908 (June 17 in the Julian calendar, in use locally at the time). Events 350 - Roman usurper Nepotianus, of the Constantinian dynasty, is defeated and killed by troops of the Usurper Year 1908 ( MCMVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year Events 1462 - Vlad III the Impaler attempts to assassinate Mehmed II ( The Night Attack) forcing him to retreat The Julian calendar, a reform of the Roman calendar, was introduced by Julius Caesar in 46 BC and came into force in 45 BC (709 Ab urbe condita ^[2]

The explosion was most likely caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3–6 miles) above Earth's surface. An air burst occurs whenever an Explosive device such as an Anti-personnel Artillery shell or a Nuclear weapon is detonated in the Air A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand A mile is a unit of Length, usually used to measure Distance, in a number of different systems including Imperial units United States EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Different studies have yielded varying estimates for the object's size, with general agreement that it was a few tens of metres across. ^[3]

Although the meteor or comet burst in the air rather than directly hitting the surface, this event is still referred to as an impact. See also Impact crater An impact event is the Collision of a large Meteoroid, Asteroid or Comet (generically Estimates of the energy of the blast range from 5 megatons^[4] to as high as 30 megatons^[5] of TNT, with 10–15 megatons the most likely^[5] - about 1000 times as powerful as the bomb dropped on Hiroshima, Japan and about one third the power of Tsar Bomba. Trinitrotoluene ( TNT) is a Chemical compound with the formula C6H2(NO23CH3 The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at For a topic outline on this subject see List of basic Japan topics. Tsar Bomba (ru Царь-бомба literally " King Bomb" is the Western name for the RDS-220 hydrogen bomb (codenamed "Иван" (Ivan by its ^[6] The explosion knocked over an estimated 80 million trees over 2,150 square kilometres (830 square miles). Square Kilometre ( US spelling square kilometer) symbol km2, is a decimal multiple of the SI unit of The square mile is an imperial and US unit of Area equal the area of a square of one statute mile. It is estimated that the earthquake from the blast would have measured 5. 0 on the Richter scale, which was not yet developed at the time. The Richter magnitude scale, or more correctly local magnitude M L scale assigns a single number to quantify the amount of seismic energy released An explosion of this magnitude is capable of destroying a large metropolitan area. A metropolitan area is a large population center consisting of a large Metropolis and its adjacent zone of influence or of more than one closely adjoining neighboring central ^[7] This possibility has helped to spark discussion of asteroid deflection strategies. Asteroid deflection strategies are methods by which Near-Earth objects could be diverted preventing potentially catastrophic Impact events A sufficiently large

The Tunguska event is believed to be the largest impact event on land in Earth's recent history;^[8] impacts of similar size in remote ocean areas would have gone unnoticed before the advent of global satellite monitoring in the 1960s and 1970s. See also Impact crater An impact event is the Collision of a large Meteoroid, Asteroid or Comet (generically EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001

Description

Approximate location of the Tunguska event in Siberia. Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving

At around 7:17 a. m. local time, Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a column of bluish light, nearly as bright as the Sun, moving across the sky. The Evenks or Evenki (autonym Эвэнкил Evenkil; Эвенки Evenki; 鄂温克族 pny ''Èwēnkè Zú'' formerly known as Tungus Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending Lake Baikal (о́зеро Байка́л Ozero Baykal, ˈozʲɪrə bʌjˈkɑl Байгал нуур Baygal nuur) is in Southern Siberia in Russia The Sun (Sol is the Star at the center of the Solar System. About 10 minutes later, there was a flash and a sound similar to artillery fire. Eyewitnesses closer to the explosion reported the sound source moving east to north. The sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of miles away. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called The majority of eyewitnesses reported only the sounds and the tremors, and not the sighting of the explosion. Eyewitness accounts differ as to the sequence of events and their overall duration.

The explosion registered on seismic stations across Eurasia. Seismology (from Greek grc σεισμός seismos, "earthquake" and grc -λογία -logia) is the scientific study of Earthquakes For the superstate in George Orwell 's novel see Nations of Nineteen Eighty-Four. Although the Richter scale was not developed until 1935, in some places the shock wave would have been equivalent to an earthquake of 5. The Richter magnitude scale, or more correctly local magnitude M L scale assigns a single number to quantify the amount of seismic energy released 0 on the Richter scale. It also produced fluctuations in atmospheric pressure strong enough to be detected in Great Britain. The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom, the UK or Britain,is a Sovereign state located Over the next few weeks, night skies were aglow such that one could read in their light, from dust suspended in the stratosphere by the explosion. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere. In the United States, the Smithsonian Astrophysical Observatory and the Mount Wilson Observatory observed a decrease in atmospheric transparency that lasted for several months, also from the suspended dust. The United States of America —commonly referred to as the The Smithsonian Astrophysical Observatory (SAO is a "research institute" of the Smithsonian Institution headquartered in Cambridge Massachusetts, The Mount Wilson Observatory (MWO is an Astronomical observatory in Los Angeles County California. An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere "

The Guinness Book of World Records (1966 edition) states that due to the rotation of Earth, if the collision had occurred 4 hours 47 minutes later, it would have completely destroyed the Imperial Russian capital, Saint Petersburg. Guinness World Records, known until 2000 as The Guinness Book of Records (and in previous U Year 1966 ( MCMLXVI) was a Common year starting on Saturday (link will display full calendar of the 1966 Gregorian calendar. The Russian Empire ( Pre-reform Russian: Pоссійская Имперія Modern Russian: Российская Империя translit: Rossiyskaya Saint Petersburg ( tr: Sankt-Peterburg,) is a city and a federal subject of Russia located on the Neva River

Selected eyewitness reports

• Testimony of S. Semenov, as recorded by Leonid Kulik's expedition in 1930. Leonid Alekseyevich Kulik ( Russian: Леонид Алексеевич Кулик August 19, 1883, Tartu &ndash April 24, ^[9]

"At breakfast time I was sitting by the house at Vanavara trading post (65 kilometres/40 miles south of the explosion), facing North. [. . . ] I suddenly saw that directly to the North, over Onkoul's Tunguska road, the sky split in two and fire appeared high and wide over the forest (as Semenov showed, about 50 degrees up - expedition note). The split in the sky grew larger, and the entire Northern side was covered with fire. At that moment I became so hot that I couldn't bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few yards. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped. "

• Testimony of Chuchan of Shanyagir tribe, as recorded by I. M. Suslov in 1926. ^[10]

"We had a hut by the river with my brother Chekaren. We were sleeping. Suddenly we both woke up at the same time. Somebody shoved us. We heard whistling and felt strong wind. Chekaren said, 'Can you hear all those birds flying overhead?' We were both in the hut, couldn't see what was going on outside. Suddenly, I got shoved again, this time so hard I fell into the fire. I got scared. Chekaren got scared too. We started crying out for father, mother, brother, but no one answered. There was noise beyond the hut, we could hear trees falling down. Chekaren and I got out of our sleeping bags and wanted to run out, but then the thunder struck. This was the first thunder. The Earth began to move and rock, wind hit our hut and knocked it over. My body was pushed down by sticks, but my head was in the clear. Then I saw a wonder: trees were falling, the branches were on fire, it became mighty bright, how can I say this, as if there was a second sun, my eyes were hurting, I even closed them. It was like what the Russians call lightning. And immediately there was a loud thunderclap. This was the second thunder. The morning was sunny, there were no clouds, our Sun was shining brightly as usual, and suddenly there came a second one! "Chekaren and I had some difficulty getting out from under the remains of our hut. Then we saw that above, but in a different place, there was another flash, and loud thunder came. This was the third thunder strike. Wind came again, knocked us off our feet, struck against the fallen trees. "We looked at the fallen trees, watched the tree tops get snapped off, watched the fires. Suddenly Chekaren yelled 'Look up' and pointed with his hand. I looked there and saw another flash, and it made another thunder. But the noise was less than before. This was the fourth strike, like normal thunder. "Now I remember well there was also one more thunder strike, but it was small, and somewhere far away, where the Sun goes to sleep. "

• Sibir newspaper, July 2, 1908^[11]

"On the 17th of June, around 9 in the AM, we observed an unusual natural occurrence. Events 310 - Pope Miltiades is elected 626 - In fear of assassination Li Shimin ambushes and kills his rival Year 1908 ( MCMVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year In the N Karelinski village (200 verst N of Kirensk) the peasants saw to the North-West, rather high above the horizon, some strangely bright (impossible to look at) bluish-white heavenly body, which for 10 minutes moved downwards. A verst (Russian versta, верста is an obsolete Russian Unit of length. The body appeared as a "pipe", i. e. a cylinder. The sky was cloudless, only a small dark cloud was observed in the general direction of the bright body. It was hot and dry. As the body neared the ground (forest), the bright body seemed to smudge, and then turned into a giant billow of black smoke, and a loud knocking (not thunder) was heard, as if large stones were falling, or artillery was fired. A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. All buildings shook. At the same time the cloud began emitting flames of uncertain shapes. All villagers were stricken with panic and took to the streets, women cried, thinking it was the end of the world. "The author of these lines was meantime in the forest about 6 verst N of Kirensk, and heard to the NE some kind of artillery barrage, that repeated in intervals of 15 minutes at least 10 times. A verst (Russian versta, верста is an obsolete Russian Unit of length. In Kirensk in a few buildings in the walls facing north-east window glass shook. "

• Siberian Life newspaper, July 27, 1908^[12]

"When the meteorite fell, strong tremors in the ground were observed, and near the Lovat village of the Kansk uezd two strong explosions were heard, as if from large-caliber artillery. Events 1214 - Battle of Bouvines: In France, Philip II of France defeats John of England. Year 1908 ( MCMVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year Uyezd or uezd (уе́зд uˈjɛst was an admistrative subdivision of Rus', Muscovy, and Russian Empire used from the 13th century originally "

• Krasnoyaretz newspaper, July 13, 1908^[13]

"Kezhemskoe village. Events 1174 - William I of Scotland, a key rebel in the Revolt of 1173-1174, is captured at Alnwick by forces loyal to Year 1908 ( MCMVIII) was a Leap year starting on Wednesday (link will display the full calendar of the Gregorian calendar (or a Leap year On the 17th an unusual atmospheric event was observed. At 7:43 the noise akin to a strong wind was heard. Immediately afterwards a horrific thump sounded, followed by an earthquake which literally shook the buildings, as if they were hit by a large log or a heavy rock. The first thump was followed by a second, and then a third. Then - the interval between the first and the third thumps were accompanied by an unusual underground rattle, similar to a railway upon which dozens of trains are traveling at the same time. Afterwards for 5 to 6 minutes an exact likeness of artillery fire was heard: 50 to 60 salvoes in short, equal intervals, which got progressively weaker. After 1. 5 - 2 minutes after one of the "barrages" six more thumps were heard, like cannon firing, but individual, loud, and accompanied by tremors. "The sky, at the first sight, appeared to be clear. There was no wind and no clouds. However upon closer inspection to the North, i. e. where most of the thumps were heard, a kind of an ashen cloud was seen near the horizon which kept getting smaller and more transparent, and possibly by around 2-3 p. m. completely disappeared. "

History

There was little scientific curiosity about the impact at the time, possibly due to the isolation of the Tunguska region. If there were any early expeditions to the site, the records were likely to have been lost during the subsequent chaotic years — World War I, the Russian Revolution of 1917, and the Russian Civil War. World War I (abbreviated WWI; also known as the First World War, the Great War, and the War to End All See also Russian Revolution (1905 The Russian Revolution of 1916 refers to a series of popular revolutions in Russia, and the events surrounding them The Russian Civil War (1917–1923 was a multi-party war that occurred within the former Russian Empire after the Russian provisional government collapsed

The first recorded expedition arrived at the scene more than a decade after the event. In 1921, the Russian mineralogist Leonid Kulik, visiting the Podkamennaya Tunguska River basin as part of a survey for the Soviet Academy of Sciences, deduced from local accounts that the explosion had been caused by a giant meteorite impact. Mineralogy is an Earth Science focused around the Chemistry, Crystal structure, and physical (including optical) properties of Minerals Leonid Alekseyevich Kulik ( Russian: Леонид Алексеевич Кулик August 19, 1883, Tartu &ndash April 24, The Russian Academy of Sciences (Российская Академия Наук Rossi'iskaya Akade'miya Nau'k, shortened to PAH RAN) consists of the National See also Impact crater An impact event is the Collision of a large Meteoroid, Asteroid or Comet (generically He persuaded the Soviet government to fund an expedition to the Tunguska region, based on the prospect of meteoric iron that could be salvaged to aid Soviet industry. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Iron Meteorites consist overwhelmingly of Nickel - Iron Alloys The metal taken from these meteorites is known as meteoric iron' and

Photograph from the Soviet Academy of Science 1927 expedition led by Leonid Kulik.

Kulik's party reached the site in 1927. Year 1927 ( MCMXXVII) was a Common year starting on Saturday (link will display full calendar of the Gregorian calendar. To their surprise, no crater was to be found. In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body There was instead a region of scorched trees about 50 kilometres (30 miles) across. A few near ground zero were still strangely standing upright, their branches and bark stripped off. The term Ground Zero may be used to describe the point on the earth's surface where an explosion occurs Those farther away had been knocked down in a direction away from the center.

During the next ten years there were three more expeditions to the area. Kulik found a little "pothole" bog that he thought might be the crater, but after a laborious exercise in draining the bog, he found there were old stumps on the bottom, ruling out the possibility that it was a crater. A bog or mire is a Wetland type that accumulates Acidic Peat, a deposit of dead plant material &ndash usually Mosses but also After a Tree has been cut and felled the stump or tree stump is usually a small remaining portion of the trunk with the Roots still in the ground In 1938, Kulik arranged for an aerial photographic survey of the area,^[14] which revealed that the event had knocked over trees in a huge butterfly-shaped pattern. Year 1938 ( MCMXXXVIII) was a Common year starting on Saturday (link will display the full calendar of the Gregorian calendar. Despite the large amount of devastation, there was no crater to be seen.

Expeditions sent to the area in the 1950s and 1960s found microscopic glass spheres in siftings of the soil. Chemical analysis showed that the spheres contained high proportions of nickel and iridium, which are found in high concentrations in meteorites, hinting that they were of extraterrestrial origin. Analytical chemistry is the study of the Chemical composition of natural and artificial Materials. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 A meteorite is a natural object originating in Outer space that survives an impact with the Earth 's surface

Detailed systematic eyewitness reports began to be gathered as late as 1959, when interviews were conducted with many of the indigenous people who had been within 100 kilometres (60 miles) of the explosion. Most of these accounts claimed that the local people had been covered with boils after the explosion, with whole families dying. Boil or furuncle is a skin disease caused by the infection of Hair follicles resulting in the localized accumulation of Pus and dead tissue The medical scientists attached to the expedition concluded that there had been an epidemic of smallpox in the area at the time. Smallpox is an Infectious disease unique to humans caused by either of two virus variants named Variola major and Variola minor.

Earth impactor

Meteoroid airburst

In scientific circles, the leading explanation for the explosion is the airburst of a meteoroid 6–10 kilometres (4–6 miles) above Earth's surface.

Meteoroids enter Earth's atmosphere from outer space every day, usually travelling at a speed of more than 10 kilometres per second (6 miles/sec or 21,600 mph). An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " Outer space, often simply called space, comprises the relatively empty regions of the Universe outside the escape velocities of Celestial bodies. Most are small but occasionally a larger one enters. The heat generated by compression of air in front of the body (ram pressure) as it travels through the atmosphere is immense and most meteoroids burn up or explode before they reach the ground. In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature In Physics, ram pressure is a pressure exerted on a body which is moving through a Fluid medium Since the second half of the 20th century, close monitoring of Earth's atmosphere has led to the discovery that such meteoroid airbursts occur rather frequently. A stony meteoroid of about 10 metres (30 ft) in diameter can produce an explosion of around 20 kilotons, similar to that of the Fat Man bomb dropped on Nagasaki, and data released by the U.S. Air Force's Defense Support Program indicate that such explosions occur high in the upper atmosphere more than once a year. A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United "Fat Man" is the codename for the Atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9 The atomic bombings of Hiroshima and Nagasaki were nuclear attacks near the end of World War II against the Empire of Japan by the United States at The Defense Support Program (DSP is a program of the US Air Force that operates the Reconnaissance satellites which form the principal component of the Satellite Tunguska-like megaton-range events are much rarer. Eugene Shoemaker estimated that such events occur about once every 300 years. Eugene Merle Shoemaker (or Gene Shoemaker ( April 28, 1928  &ndash July 18, 1997) was one of the founders of the fields of Planetary

Blast patterns

The explosion's effects on the trees near ground zero was replicated during atmospheric nuclear tests in the 1950s and 1960s. Nuclear weapons tests are experiments carried out to determine the effectiveness yield and explosive capability of Nuclear weapons Throughout the twentieth century most nations These effects are caused by the shock wave produced by large explosions. For the music album by Converter see Shock Front For the 1977 horror film see Shock Waves A shock wave (also called An explosion is a sudden increase in Volume and release of Energy in an extreme manner usually with the generation of high Temperatures and the release The trees directly below the explosion are stripped as the blast wave moves vertically downward, while trees further away are knocked over because the blast wave is travelling closer to the horizontal when it reaches them.

Soviet experiments performed in the mid-1960s, with model forests (made of matches) and small explosive charges slid downward on wires, produced butterfly-shaped blast patterns strikingly similar to the pattern found at the Tunguska site. A match is a consumable Tool for lighting a Fire under controlled circumstances on demand The experiments suggested that the object had approached at an angle of roughly 30 degrees from the ground and 115 degrees from north and had exploded in mid-air.

Asteroid or comet?

The composition of the Tunguska body remains a matter of controversy. In 1930, the British astronomer F.J.W. Whipple suggested that the Tunguska body was a small comet. Francis John Welsh Whipple (1876-1943 was a British mathematician and meteorologist A comet is a small Solar System body that orbits the Sun and when close enough to the Sun exhibits a visible coma (atmosphere or a tail — A cometary meteorite, being composed primarily of ice and dust, could have been completely vaporized by the impact with the Earth's atmosphere, leaving no obvious traces. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia Dust is a general name for minute Solid particles with Diameters less than 500 micrometers. The comet hypothesis was further supported by the glowing skies (or "skyglows" or "bright nights") observed across Europe for several evenings after the impact, possibly explained by dust and ice that had been dispersed from the comet's tail across the upper atmosphere. ^[5] The cometary hypothesis gained a general acceptance amongst Soviet Tunguska investigators by the 1960s. ^[5]

In 1978, Slovak astronomer Ľubor Kresák suggested that the body was a fragment of the short-period Comet Encke, which is responsible for the Beta Taurid meteor shower; the Tunguska event coincided with a peak in that shower,^[15] and the approximate trajectory of the Tunguska impactor is consistent with what would be expected from such a fragment. Slovakia (long form Slovak Republic; Slovak:, long form, is a Landlocked country in Central Europe with a population of over five million Ľubor Kresák (1927 &ndash 1994 was a Slovak Astronomer. He discovered two Comets the periodic comet 41P/Tuttle-Giacobini-Kresak and the Comet Encke (officially designated 2P/Encke) is a periodic Comet, named after Johann Franz Encke, who through laborious study of its Orbit and The Beta Taurids are an annual Meteor shower belonging to a class of "daytime showers" that peak after sunrise A meteor shower, some of which are known as a "meteor storm" or "meteor outburst" is a celestial event where a group of meteors are observed to radiate from one point ^[5] It is now known that bodies of this kind explode at frequent intervals tens to hundreds of kilometres above the ground. Military satellites have been observing these explosions for decades. ^[16]

In 1983, astronomer Zdeněk Sekanina published a paper criticizing the comet hypothesis. He pointed out that a body composed of cometary material, travelling through the atmosphere along such a shallow trajectory, ought to have disintegrated, whereas the Tunguska body apparently remained intact into the lower atmosphere. Sekanina argued that the evidence pointed to a dense, rocky object, probably of asteroidal origin. Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but This hypothesis was further boosted in 2001, when Farinella, Foschini, et al. released a study suggesting that the object had arrived from the direction of the asteroid belt. The asteroid belt is the region of the Solar System located roughly between the orbits of the Planets Mars and Jupiter.

Proponents of the comet hypothesis have suggested that the object was an extinct comet with a stony mantle that allowed it to penetrate the atmosphere.

The chief difficulty in the asteroid hypothesis is that a stony object should have produced a large crater where it struck the ground, but no such crater has been found. In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body It has been hypothesized that the passage of the asteroid through the atmosphere caused pressures and temperatures to build up to a point where the asteroid abruptly disintegrated in a huge explosion. The destruction would have to have been so complete that no remnants of substantial size survived, and the material scattered into the upper atmosphere during the explosion would have caused the skyglows. Models published in 1993 suggested that the stony body would have been about 60 metres across, with physical properties somewhere between an ordinary chondrite and a carbonaceous chondrite. Chondrites are stony Meteorites that have not been modified due to Melting or Differentiation of the parent body A carbonaceous chondrite or a C-type chondrite is a type of chondritic Meteorite which contains high levels of Water and Organic compounds

Christopher Chyba and others have proposed a process whereby a stony meteorite could have exhibited the behavior of the Tunguska impactor. Their models show that when the forces opposing a body's descent become greater than the cohesive force holding it together, it blows apart, releasing nearly all its energy at once. The result is no crater, and damage distributed over a fairly wide radius, all of the damage being blast and thermal.

During the 1990s, Italian researchers extracted resin from the core of the trees in the area of impact, to examine trapped particles that were present during the 1908 event. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. They found high levels of material commonly found in rocky asteroids and rarely found in comets. ^[17][18]

Lake Cheko

In June of 2007 it was announced that scientists from the University of Bologna had identified a lake in the Tunguska region as a possible impact crater from the event. The University of Bologna (Alma Mater Studiorum Università di Bologna UNIBO) is one of the oldest continually operating degree-granting universities in the world A lake (from Latin lacus) is a Terrain feature (or Physical feature) a body of Liquid on the surface of a world that is localized to the Lake Cheko is a small bowl shaped lake approximately 8 kilometres north-north-west of the hypocenter. Lake Cheko is a small freshwater Lake in Siberia, near the Podkamennaya Tunguska River. ^[19] The hypothesis has been challenged by other impact crater specialists. ^[20] A 1961 investigation had dismissed a modern origin of Lake Cheko, saying that the presence of metres thick silt deposits at the lake's bed suggests an age of at least 5000 years. Silt is Soil or rock derived Granular material of a Grain size between sand and clay ^[21] Work is still being done at Lake Cheko to determine its origins. ^[22]

Speculative hypotheses

Scientific understanding of the behaviour of meteorites in the Earth's atmosphere was much sparser during the early decades of the 20th century. Due to this lack of knowledge, as well as a paucity of scientific data about Tunguska due to Soviet secrecy during the Cold War, a great many other hypotheses for the Tunguska event have sprung up, none of which are accepted by the scientific community. Cold War is the state of conflict tension and competition that existed between the United States and the Soviet Union (USSR and their respective allies from the

End of the World?

According to G. K. Kulesh, head of the Kirensk Meteorological Station^[24]

Natural H-bomb

In 1989, D'Alessio and Harms suggested that some of the deuterium in a comet entering the Earth's atmosphere may have undergone a nuclear fusion reaction,^[25] leaving a distinctive signature in the form of carbon-14. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth They concluded that any release of nuclear energy would have been almost negligible. Independently, in 1990, César Sirvent proposed that a deuterium comet, i. e. , a comet with an anomalous high concentration of deuterium into its composition, could have exploded as a natural hydrogen bomb, generating most of the energy released. The sequence would be first a mechanical or kinetic explosion, triggering a thermonuclear reaction. These proposals are inconsistent with knowledge both of the composition of comets and of the temperature and pressure conditions necessary for initiating a nuclear fusion reaction. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus ^[26]

Black hole

In 1973, Albert A. Jackson and Michael P. Ryan, physicists at the University of Texas, proposed that the Tunguska event was caused by a "small" (around 10²⁰ g to 10²² g) black hole passing through the Earth. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e ^[27] This hypothesis fails, as there was no so-called "exit event" — a second explosion occurring as the black hole, having tunneled through the Earth, shot out the other side on its way back into space - nor were there the continuous seismic disturbances that would occur along the hole's path through the mantle. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided

The hypothesis was used by Larry Niven in his science fiction story The Borderland of Sol, and by David Brin, in his novel Earth, as well as by Bill DeSmedt in his novel Singularity. Laurence van Cott Niven (born April 30, 1938 Los Angeles California) is a US Science fiction author. " The Borderland of Sol " is an English language Science fiction novelette written in 1975 by Larry Niven. Glen David Brin, PhD (born October 6, 1950) is an American scientist and award-winning author of Science fiction. Earth is a 1990 Science fiction novel written by David Brin. The book was nominated for the Hugo Award for Best Novel William H DeSmedt is an American author of Science fiction. His first novel Singularity (2004 explores the 1908 Tunguska event Singularity (ISBN 0-9745734-4-2 is a novel by Bill DeSmedt published by Per Aspera Press on November 8, 2004. It also figures in Dan Simmons's Hyperion novels.

Antimatter

In 1965, Cowan, Atluri, and Libby suggested that the Tunguska event was caused by the annihilation of a chunk of antimatter falling from space. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed ^[28] However, as with the other hypotheses described in this section, this does not account for the mineral debris left in the area of the explosion. Furthermore, there is no astronomical evidence for the existence of such chunks of antimatter in our region of the universe. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy If such objects existed, they should be constantly producing energetic gamma rays due to annihilation against the interstellar medium, but such gamma rays have not been observed. Gamma rays (denoted as &gamma) are a form of Electromagnetic radiation or light emission of frequencies produced by sub-atomic particle interactions

UFO crash

Various UFO aficionados have claimed that the Tunguska event was the result of an exploding alien spaceship or even an alien weapon going off to "save the Earth from an imminent threat". These claims appear to originate from a science fiction story penned by Soviet engineer Alexander Kazantsev in 1946, in which a nuclear-powered Martian spaceship, seeking fresh water from Lake Baikal, blew up in mid-air. Alexander Petrovitch Kazantsev ( 2 September 1906 – 13 September 2002) was a popular Soviet Science-fiction author Lake Baikal (о́зеро Байка́л Ozero Baykal, ˈozʲɪrə bʌjˈkɑl Байгал нуур Baygal nuur) is in Southern Siberia in Russia This story was inspired by Kazantsev's visit to Hiroshima in late 1945. The Japanese city of ( is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshū, the largest of Japan 's

Many events in Kazantsev's tale were subsequently confused with the actual occurrences at Tunguska. The nuclear-powered UFO hypothesis was adopted by TV drama critics Thomas Atkins and John Baxter in their book The Fire Came By (1976). The 1998 television series The Secret KGB UFO Files (Phenomenon: The Lost Archives), broadcast on Turner Network Television, referred to the Tunguska event as "the Russian Roswell" and claimed that crashed UFO debris had been recovered from the site. A television program (US television programme (UK or television show (U Turner Network Television, usually referred to as TNT, is an American cable TV network created by media mogul Ted Turner and currently owned The Roswell Incident involved the recovery of materials near Roswell New Mexico, USA, on July 7, 1947, which has become the subject of intense In 2004, a group from the Tunguska Space Phenomenon Public State Fund claimed to have found the wreckage of an alien spacecraft at the site. ^[29]

The proponents of the UFO hypothesis have never been able to provide any significant evidence for their claims. It should be noted that the Tunguska site is downrange from the Baikonur Cosmodrome and has been contaminated repeatedly by Russian space debris, most notably by the failed launch of the fifth Vostok test flight on December 22, 1960. The Baikonur Cosmodrome ( Kazakh: Байқоңыр ғарыш айлағы, Bayqoñır ğarış aylağı; Russian: Космодром The Vostok programme (Восто́к translated as "East") was a Soviet Human spaceflight project that succeeded in putting a person into Events 1790 - The Turkish fortress of Izmail is stormed and captured by Suvorov and his Russian armies Year 1960 ( MCMLX) was a Leap year starting on Friday (link will display full calendar of the Gregorian calendar. The payload landed close to the Tunguska impact site, and a team of engineers was dispatched there to recover the capsule and its two canine passengers (who survived).

Similar events

The Tunguska event is the strongest, but not the only, significant meterorite airburst in recent history. A selection of similar events follows. This list is quite biased, since recording of meteorite explosive yields is relatively recent:

Tunguska event in fiction

Main article: Tunguska event in fiction

See also

• Asteroid deflection strategies
• Cando event
• Cretaceous–Tertiary extinction event
• Doomsday event
• Eastern Mediterranean Event
• Lonar crater
• Vela Incident
• Vitim event

References

• Baxter, John and Thomas Atkins, The Fire Came By: The Riddle of the Great Siberian Explosion, Macdonald and Jane's, London 1975. Events 1508 - Maximilian I Holy Roman Emperor, is defeated in Friulia by Venetian forces; he is forced to sign a three-year See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. The Eastern Mediterranean Event was a high-energy aerial Explosion over the Mediterranean Sea, around 34°N 21°E (between Libya and Crete The Tunguska event was an explosion that occurred on June 30, 1908 in the Siberian region of Russia, possibly caused by a Asteroid deflection strategies are methods by which Near-Earth objects could be diverted preventing potentially catastrophic Impact events A sufficiently large The Cando event was an Explosion that occurred in the village of Cando Spain, in the morning of January 18, 1994. The Cretaceous–Tertiary extinction event, which occurred approximately ( Ma) was a large-scale mass extinction of animal and plant species in a geologically A doomsday event is a specific occurrence which has an exceptionally destructive effect on the human race The Eastern Mediterranean Event was a high-energy aerial Explosion over the Mediterranean Sea, around 34°N 21°E (between Libya and Crete Lonar crater is an Impact crater situated in the Buldhana district of the Indian state of Maharashtra. The Vela Incident (sometimes referred to as the South Atlantic Flash) was an as-yet unidentified double flash of Light detected by a United States The Vitim event or Bodaybo event is believed to be an impact by a Bolide or Comet nucleus in the Vitim River basin ISBN 044689396X.
• Brown, J. C, and Hughes, D. W. Nature 268, 512–514 (1977)
• Furneaux, Rupert. The Tungus Event, Nordon Publications, New York, 1977. ISBN 058604423X.
• Gallant, Roy A. The Day the Sky Split Apart: Investigating a Cosmic Mystery, Atheneum Books for Children, New York, 1995. ISBN 0689803230.
• Krinov, E. L. Giant Meteorites, trans. J. S. Romankiewicz (Part III: The Tunguska Meteorite), Pergamon Press, Oxford, 1966
• Kundt, W. Current Science. 81. 399-407 (2001) [1]
• Morgan, J. Phipps, Ranero, C. R. , Reston, T. J. Earth and Planetary Science Letters. 217. 263-284 (2004)
• Lerman, J. C. , Mook, W. G. & Vogel, J. C. Nature, Effect of the Tunguska Meteor and Sunspots on Radiocarbon in Tree Rings, (9 December 1967) | doi:10. 1038/216990a0; 216, 990–1 (1967)[2]
• Ol'khovatov, A. Yu. Earth, Moon and Planets, v. 93, pp. 163–173 (2003)
• Stoneley, Jack. Cauldron of Hell: Tunguska, Simon and Schuster, New York, 1977. ISBN 0671229435.
• Verma, Surendra. The Tunguska Fireball: Solving One of the Great Mysteries of the 20th century, Icon Books, Cambridge, 2005. ISBN 1840466200.
• Verma, Surendra. The Mystery of the Tunguska Fireball, Icon Books, Cambridge, 2006. ISBN 1840467282.

Notes

External links

• Article about the events, special attention to Leonid Kulik on MysteryDatabase. com
• Quasi Three-Dimensional Modeling of Tunguska Comet Impact (1908) Dr. Andrei E. Zlobin, Paper of 2007 Planetary Defense Conference.
• Tunguska Comet Impact 1908
• The Tunguska Event in 1908: Evidence from Tree-Ring Anatomy - Evgenii A. Vaganov, Malkolm K. Hughes, Pavel P. Silkin and Valery D. Nesvetailo, Astrobiology, Volume 4, Number 3, 2004, pp. 391-399
• Tunguska.ru Russian site with a tiny English section. Includes some gorgeous Tunguska photos.
• Tunguska A research group at University of Bologna that has conducted several recent expeditions to the site. The University of Bologna (Alma Mater Studiorum Università di Bologna UNIBO) is one of the oldest continually operating degree-granting universities in the world
• Tunguska pictures Many Tunguska-related pictures with comments in English.
• Preliminary results from the 1961 combined Tunguska meteorite expedition
• Probable asteroidal origin of the Tunguska Cosmic Body A 2001 paper arguing for the asteroidal hypothesis.
• "Russian Alien Spaceship Claims Raise Eyebrows, Skepticism" article, arguing the event was caused by meteor explosion
• "The Vurdalak Conjecture" website explores the science behind the black-hole impact hypothesis.
• 1908 Siberia Explosion. Reconstruction by William K. Hartmann.
• Simulation of such an event & origin of King Tut's glass
• Team makes Tunguska crater claim (BBC News)
• Astonomy Picture of the Day on Tunguska
• Mystery space blast 'solved' (BBC News)