Tunguska event

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Trees felled by the Tunguska blast. Photograph from Kulik's 1927 expedition.
File:Russia-CIA WFB Map--Tunguska.png
Approximate location of the Tunguska event, in Siberia.

The Tunguska event was an aerial explosion that occurred at Template:Coor dm, near the Podkamennaya (Stony) Tunguska River in what is now Evenkia, Siberia, at 7:17 AM on June 30, 1908. The size of the blast was later estimated to be between 10 and 15 megatons. It felled an estimated 60 million trees over 2,150 square kilometers.


A global map of ground zero.

At around 7:15 AM, Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a huge fireball moving across the sky, nearly as bright as the Sun. A few minutes later, there was a flash that lit up half of the sky, followed by a shock wave that knocked people off their feet and broke windows up to 650 km (400 mi) away. The explosion registered on seismic stations across Eurasia, and produced fluctuations in atmospheric pressure strong enough to be detected by the recently invented barographs in Britain. Over the next few weeks, night skies were aglow such that one could read in their light. In the United States, the Smithsonian Astrophysical Observatory and the Mount Wilson Observatory observed a decrease in atmospheric transparency that lasted for several months.


Surprisingly, 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, their records were lost during the subsequent chaotic years — World War I, the Russian Revolution of 1917, and the Russian Civil War.

The first expedition for which records have survived 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. 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 iron would more than pay for the expedition alone.

File:Tunguska trees.jpg
Photograph from Kulik's 1927 expedition.

Kulik's expedition reached the site in 1927. To their surprise, no crater was to be found. There was instead a region of scorched trees about 50 kilometres across. A few near ground zero were still strangely standing upright, their branches and bark stripped off. 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. In 1938, Kulik managed to arrange for an aerial photographic survey of the area, which revealed that the event had knocked over trees in a huge butterfly-shaped pattern. 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, indicating that they were of extraterrestrial origin. Expeditions led by Gennady Plekhanov found no elevated levels of radiation, which might have been expected if the detonation were nuclear in nature.

Meteorite hypothesis

Meteor airburst

In scientific circles, the leading explanation for the blast is the airburst of a meteor 6 to 10 kilometers above the Earth's surface.

Meteors are constantly entering the Earth's atmosphere from outer space, usually travelling at a speed of more than 10 kilometers per second. The heat generated by compression of air in front of the meteor as it travels through the atmosphere is immense, and most meteors completely burn up or explode before they can reach the ground. Starting from the second half of the 20th century, close monitoring of the Earth's atmosphere has led to the discovery that such meteor airbursts occur rather frequently. A stony meteoroid of about 10 meters in diameter can produce an explosion of around 20 kilotons, similar to the Little Boy bomb that flattened Hiroshima, and data released by the U.S. Air Force's Defense Support Program has shown that such explosions occur at a rate of more than once a year. Tunguska-like megaton-range events are much rarer. Eugene Shoemaker has estimated that such events occur at the rate of about once every 300 years.

Blast patterns

The curious effect of the Tunguska explosion on the trees near ground zero has been observed during atmospheric nuclear tests in the 1950s and 1960s, and is due to the shock wave produced by such large explosions. (The radioactivity emitted by nuclear blasts does not have any effect on the phenomena in question.) The trees directly below the explosion are stripped as the blast wave moves vertically downward, while trees further away are felled because the blast wave is travelling closer to the horizontal when it reaches them.

Soviet experiments performed in the mid-1960s, with model forests and small explosive charges slid downward on wires, produced butterfly-shaped blast patterns strikingly similar to the pattern found at the Tunguska site. The experiments suggested that the object had approached at an angle of roughly 30 degrees from the ground and 115 degrees from north, and 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. 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. The comet hypothesis was further supported by the glowing skies (or "skyglows") observed across Europe for several evenings after the impact, apparently caused by dust that had been dispersed across the upper atmosphere. In addition, chemical analyses of the area have shown it to be rich in cometary material. In 1978, Slovak astronomer Lubor Kresak suggested that the body was a piece 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. It is now known such bodies regularly explode tens to hundreds of kilometres above the ground, as military satellites have been observing such explosions for decades.

In 1983, astronomer Zdenek 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. 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.

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. 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 had to be 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.

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.

On July 4, 2005, a NASA space probe dubbed Deep Impact launched a 370 kilogram (814 pound) probe at comet Tempel 1. The impact, at a relative velocity of 10.3 km/s (37,000 km/h or 23,000 mi/h), revealed that the comet has very loose structure, more like a pile of powder than like a bunch of rocks. Although this could explain the lack of a crater in the Tunguska event, NASA scientists are still compiling their conclusions, and any correlation with Tunguska remains speculative.

Unexplained phenomena

There are still some aspects that have not been convincingly explained. The site lies in the middle of an ancient volcanic eruption zone, and researchers once detected an emission of radon gas that lasted four hours. Attempts to apply carbon-14 dating have shown that the soil was enriched in radioactive carbon-14. The Russian geologist Vladimir Epifanov and German astrophysicist Wolfgang Kundt have suggested that the explosion was an explosion of methane gas which was emitted from the earth. Something similar seems to have occurred in 1994 near the village of Cando in Spain. See 'New Scientist', 7 Sept. 2002, p. 14 [1] [2].

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, a great many other hypotheses for the Tunguska event have sprung up, with varying degrees of credibility. The hypotheses listed below are all rejected by modern science and by skeptics who generally see them as being gross violations of Occam's Razor.

Black Hole

In 1973, Jackson and Ryan proposed that the Tunguska event was caused by a "small" (around 1020–1022 g) black hole passing through the Earth. Unfortunately for this hypothesis, there is no evidence for a second explosion occurring as the black hole exited the Earth and it has not gained wide acceptance. Furthermore, the subsequent discovery by Stephen Hawking that black holes radiate energy indicates that such a small black hole would have evaporated away long before it could encounter the Earth.


In 1965, Cowan, Atluri, and Libby suggested that the Tunguska event was caused by the annihilation of a chunk of antimatter falling from space. 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. 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.


Some hypotheses link the Tunguska event to the magnetic storms similar to those that occur after thermonuclear explosions in the stratosphere. For example, in 1984 V. K. Zhuravlev and A. N. Dmitriev proposed a "heliophysical" model based on "plasmoids" ejected from the Sun. Valeriy Buerakov has also developed an independent model of an electromagnetic "fireball".


UFO aficionados have long claimed that the Tunguska event is the result of an exploding alien spaceship or an alien weapon going off to "save the Earth from an imminent threat". This hypothesis appears to originate from a science fiction story penned by Soviet engineer Aleksander Kazantsev in 1946, in which a nuclear-powered Martian spaceship, seeking fresh water from Lake Baikal, blew up in mid-air. This story was inspired by Kazantsev's visit to Hiroshima in late 1945.

A 1951 novel, and a subsequent 1960 movie, seized upon the UFO concept.

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, 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. In 2004, a group of Russian scientists from the Tunguska Space Phenomenon Public State Fund claimed to have found the wreck of an alien spacecraft at the site [3].

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 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 (which survived).

The Wardenclyffe Tower

It has also been suggested that the Tunguska explosion was the result of an experiment by Nikola Tesla at his Wardenclyffe Tower, performed during Robert Peary's second North Pole expedition. Allegedly he had sent a communication to Peary advising him to be on the alert for unusual auroral phenomena encountered as he attempted to reach the North Pole. However, by 1908 most work at Wardenclyffe had already ended and the site was mostly abandoned. Nor is it obvious how a small energy input at Wardenclyffe could be responsible for a large energy output elsewhere, something that is essentially a physical impossibility.

Even if it was possible for the facility to produce such an effect, the main contention that Tesla was not responsible for the Tunguska event is that it occurred at about 7:17 AM. Given accounts (if they can be trusted) stating that Tesla performed his experiments in the evening of June 30th, and that his facility was 1/4 a day ahead of Tunguska time, his Wardenclyffe experiment would then have been the day after the Tunguska event (which occurred around 1:00 in the morning on June 30th New York time).

Tunguska event in fiction

  • A crossover novel featuring Tom Swift and the Hardy Boys, entitled The Alien Factor, reveals that the Tunguska event was due to an antimatter-powered alien lifeboat crash-landing upon the Earth.
  • In a two-episode story arc of "The X-Files" ("Tunguska" and "Terma"), the Tunguska incident was purported to be caused by an asteroid impact. Fox Mulder (David Duchovny) traveled with Alex Krycek (Nicholas Lea) to the site of the impact, where they discovered a military installation mining the rock and experimenting with the Black Oil found inside, which contained a microbial form of alien life capable of possessing a human body.
  • "Listening to Fear," a fifth-season episode of "Buffy the Vampire Slayer" involves a meteor impact, thought to be the newest in a series dating back to the twelfth century. Willow Rosenberg (Alyson Hannigan) notes that "the most recent meteoritic anomaly was the Tunguska blast in Russia in 1917," getting the date wrong by nine years and ascribing it to the infamous year of the Bolshevik Revolution.
  • In the director's cut of the 2004 film Hellboy, Grigori Rasputin purchases a stone key monolith which the Russians had hidden since it landed in Tunguska, which Rasputin states was the Ogdru Jahad sending it as a way to assist him in bringing them to Earth.
  • In the late Predator comics, it reveals that the Tunguska event was due to a Predator or Predator ship self-destruct technology. It was either caused by the Predators themselves to conceal their sophisticated technology from human hands, or either by Soviet or American peoples to keep the technology from the others hands.
  • In a Marvel Comics trilogy of publications entitled Ultimate Nightmare (2004-2005), Ultimate Secret (2005), and "Ultimate Extinction"(2005), the Ultimate universe characters confront the mystery of the event, linking it to an alien encounter with the Ultimate version of Galactus. Ultimate Nightmare #1 errs in giving the year of the Event as 1904 (four years off), and depicting it as leaving a rather large impact crater (it left none).[In the Ultimates universe, several other key events differ considerably from actual history, so it is conceivable that the nature of the Tunguska event is simply another difference from our universe.]
  • Science fiction writer Stanisław Lem in his first novel Astronauts (1951) explains this event as crash of interplanetary reconnaissance vessel from Venus civilization.
  • The 1984 movie Ghostbusters references the Tunguska Event in the line, "You have been a participant in the biggest interdimensional cross-rip since the Tunguska blast of 1909.", which is off by one year.
  • The book Callahan's Key by Spider Robinson uses the connection between Tesla (made immortal in this fiction) and the Tunguska event. The 'death ray' has been stolen by the U.S. government and its use may destroy the known universe.
  • The humorous 1978 alternate history novel And Having Writ by Donald R. Bensen features four space travelers whose ship crashes to Earth at Tunguska. Needing to jumpstart Earth technology to rebuild their ship, they analyze world affairs and foresee the impending World War I, and travel the world attempting to provoke the war to get it out of the way as quickly as possible so science can move on. In the course of their travels, they interact with such characters as Theodore Roosevelt, H.G. Wells, Henry Ford, Kaiser Wilhelm, and Grigori Rasputin.
  • The novel Singularity by Bill DeSmedt explores the Jackson-Ryan hypothesis — i.e., the possibility that the Tunguska Event was caused by a submicroscopic black hole.
  • The novel Earth by David Brin also features the Jackson-Ryan hypothesis.
  • The Tunguska event (and the Jackson-Ryan hypothesis) forms part of the backstory for the 1975 Larry Niven novelette The Borderland Of Sol.
  • In the 1960 movie "First Spaceship on Venus", based on Stanisław Lem's novel, an expedition discovered a magnetic recording device at Tunguska, determined its origin as the planet Venus, and a newly-completed spacecraft was sent to Venus instead of Mars as originally planned. The expedition determined, from translation of the recording, that the aliens planned to occupy Earth, but they discovered that the people of Venus were abruptly rendered extinct by their incomprehensible machinery.
  • The novel Intervention, by Julian May, depicts a commemoration of the 100th anniversary of the impact, which was caused by the destruction of an out-of-control alien craft. Apparently, if the crew had not activated the self-destruct program, the ship would have crashed into Moscow.
  • "Chekhov's Journey" by Ian Watson, 1983, describes the possibility that the famous author Chekhov knew of the 1908 Tunguska explosion back in 1890 which turned out to be caused by an out of control Soviet time-ship.
  • The novel, "Sandstorm," by James Rollins (c)2004, uses the circumstances of Tunguska event -- in this case, a meteor composed of anti-matter -- as evidence to suggest the cause of the explosion in the book's opening pages, and the set up for the cataclysmic events of the book's climax.
  • The Star Trek novel "Prime Directive" depicts the Tunguska incident as the result of benevolent Vulcan interference in human history, where an anthropological survey ship deflected a meteor that would have struck Western Europe and destroyed much of civilization into a largely uninhabited part of the planet.

Tunguska event in music

Alan Parsons' 2004 release entitled A Valid Path features a nine minute epic entitled "Return to Tunguska" that, in his famous instrumental fashion, plays with some of the more other-worldly notions surrounding the event.

Books on Tunguska

  • John Baxter and Thomas Atkins, The Fire Came By: The Riddle of the Great Siberian Explosion, Macdonald and Jane's, London 1975
  • Rupert Furneaux, The Tungus Event, Nordon Publications, New York, 1977
  • Roy A. Gallant, The Day the Sky Split Apart: Investigating a Cosmic Mystery, Atheneum Books for Children, New York, 1995
  • E.L. Krinov, Giant Meteorites, trans. J.S. Romankiewicz (Part III: The Tunguska Meteorite), Pergamon Press, Oxford, 1966
  • Jack Stoneley, Cauldron of Hell: Tunguska, Simon and Schuster, New York, 1977
  • Surendra Verma, The Tunguska Fireball: Solving One of the Great Mysteries of the 20th Century, Icon Books, Cambridge, 2005

See also

External links

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