Tunguska Impact Event General Information
Size of the crater: none
Time: 7:17 AM, June 30, 1908
Site: 6 to 10 km above Tunguska river region, Siberia, Russia; 60°55′N 101°57′E
Size of the body: 50-60 m in diameter
Velocity: 12 to 20 km/sec

Investigation History
Surprisingly, this latest large meteoritic event is poorly investigated. And there are several reasons for that. The first thing is that it has happened in almost uninhabited area – Siberian Taiga. At the time of explosion it was mostly populated by native Siberians, among which tribal religions were still spread, which means that the mostly describe the explosion as a “magical flash of light”, “message from the Heaven” etc. It was not a good time for impact study in Russia as well – soon after the war with Japan and first revolution, not long before the World War 1 and October revolution.
Another reason is that the meteorite didn’t leave any crater, leaving no traces of the body around. This is not the worst part. Such untraceable events are numerous – take the phenomena of “shooting stars”. But, unlike the shooting star, this body caused an enigmatic devastation of surrounding area – the forest fallout at the area of about 1700 km2. So very few reliable papers exist to investigate the impact. The most important sources of information are still eyewitnesses’ records, so let’s look through some.

"I was sitting on the porch of the house at the trading station, looking north. Suddenly in the north...the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire. I felt a great heat, as if my shirt had caught fire... At that moment there was a bang in the sky, and a mighty crash... I was thrown twenty feet from the porch and lost consciousness for a moment.... The crash was followed by a noise like stones falling from the sky, or guns firing. The earth trembled.... At the moment when the sky opened, a hot wind, as if from a cannon, blew past the huts from the north. It damaged the onion plants. Later, we found that many panes in the windows had been blown out and the iron hasp in the barn door had been broken."
“We had a hut by the river with my brother Chekaren. We were sleeping. Suddenly we both woke up at the same time. We heard whistling and felt strong wind. There was noise beyond the hut, we could hear trees falling down. Me and Chekaren 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. 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 a 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.”
“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.”
These are one of many evidences of the blast. People in 200 km area heard thunder, saw the explosion, and witnessed wild fires. Remember, it was the very beginning of the 20th century, so it must have been a real shock for them. It is no wonder that numerous non-scientific theories appeared on the origin of the blast.
Due to the isolation of the region, scientific expedition didn’t reach the site until 1921, when Leonid Kulik, a scientist of Soviet Union Science Academy conducted an expedition to the region.
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 meteoritic iron that could be salvaged to aid Soviet industry. The iron would more than pay for the expedition.
Kulik's party reached the site in 1927. To their surprise, no crater was to be found. There was instead a region of scorched trees about 50 kilometers 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, hinting that they were of extraterrestrial origin. But there are problems in assigning the particles to the Tunguska event, especially as Tunguska occurred in the ancient volcanic region with iridium abundance.
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 kilometers of the explosion. Most of these accounts claimed that the local people had been covered with boils after the explosion, with whole families dying off. Expeditions led by Gennady Plekhanov found no elevated levels of radiation, which might have been expected had the detonation been nuclear in nature.
Though as we have found out, the meteoritic hypothesis was introduced during the first expedition, it caused severe debates among scientists. The enigmatic event was supposed to originate from all kinds of events, including methane explosion or a UFO blast.

Reconstruction of the impact
At 7:17 AM on the morning of June 30, 1908, a mysterious explosion occurred in the skies over Siberia. It was caused by the impact and breakup of a large meteorite, at an altitude roughly six kilometers in the atmosphere. Realistic pictures of the event are unavailable. However, Russian scientists collected eyewitness accounts of the event.
Crater could not be found at the impact site, as the body was totally disrupted, decelerated and vaporized at an altitude of about 8-10 km. However, a strong shock wave reached the surface and, interacting with the surface, caused taiga fallout.
All meteoritical material (tiny droplets and fragments) flew away from the impact site within the wake, created by Tunguska-asteroid in atmosphere (which operated like a chimney). Final depositions of these fragments strongly depend on particle size and local atmospheric conditions (winds). Most probably, we can find some tracers of Tunguska impact hundred- thousand km away from the impact site (in uprange direction, i.e. to south-east). Phil Bland will go to Siberia this May with the single goal – to find this enigmatic meteorite.

Ecological effect
Though the impact was not strong enough to cause any serious damage to the Earth’s ecology, it did change the life of the local area for decades. Earthquakes occurred, knocking down buildings, braking trees. Wild fires killed many animals and plants. The blast caused a strange shockwave in the air, with trees knocked down, forming the strangest butterfly-shaped figure on the ground. Luckily, the blast happened over uninhabited area, which narrowed its effect and number of victims greatly.

Cultural effect
As I have already mentioned, the impact is the most enigmatic one. New hypothesis are proposed every year. I would like to list the most popular, giving a short description of every.
Black hole
In 1973 physicists at the University of Texas, proposed that the Tunguska event was caused by a "small" 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.
Antimatter
In 1965, Cowan 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.
UFO Crash
UFO aficionados have long claimed that the Tunguska event is the result of an exploding alien spaceship or even 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 Alexander Kazantsev in 1946, in which a nuclear-powered Martian spaceship, seeking fresh water from Lake Baikal, blew up in mid-air.
Though most of these hypothesis seem intriguin and far more interesting then the impact one, most of them have absolutely no scientific base and are impossible to prove.
As you see, no catastrophe has ever created such a resonance as Tunguska event. But Tunguska blast is also one of a few examples of space catastrophes resultig in not only scientific interest, but also huge effect on public. There are enormous science fiction books, pictures, movies and even poems on the event. Here is the list of few:
Most of the literature offers us half-scientific hypothesis of the event. A list of book might include:
1) “Agains the Day” by Thomas Pynchon
2) “The Alien Factor” by Tom Swift and Hardy Boys
3) “The Astronauts” by Stanislaw Lem
4) “Burning Island” by Alexander Kazantzev
5) “Monday Begins on Saturday” by Strugatzki Brothers
Science-fiction movies and TV shows are another important part of the popular culture. And they probably have the greatest impact on the society. Let’s remember some of the movies featuring Tunguska or the theories built around it:
1) The screen version of Stanislaw Lem’s novel called “The First Spaceship On Venus”
2) One of the series of “Buffy the Vampire Slayer”
3) “That which survives” from “Star Trek”
4) The “X-files” series
And it would very hard to list enourmous songs, legends, joke poems, just poems, riddles and other folk art emerged after the impact. Thousand of words have been said about Tunguska, and, unfortunately, there are still more legends than realistic fact-suported stories.