It is generally accepted that the Tunguska event resulted from the catastrophic disruption of a large meteor high above the ground.
Previous studies have yielded diverse interpretations as to the meteor's size, composition, velocity, and density before its arrival. Nevertheless, there is consensus that the disruption occurred 6 to 10 km above the ground, depositing approximately 15 Mtons of energy in a narrow altitude band. In a comprehensive analysis, Sekanina concluded that the body was not a comet, but rather an Apollo-type asteroid 90-190 meters across. More recent work has suggested that the object was a stony asteroid perhaps 60 meters in diameter.1 In contrast, Turco et al3 concluded that the meteor was of cometary origin with an effective density of 0.003 gm/cm and a diameter of 1200 meters.
In the early morning hours of June 8th 1908 a huge object is entering Earth’s atmosphere. The object begins to burn and produces a trail of light that is 800 km long. At the trading post of Vanavera the Tungus tribesmen and the Russian fur traders look scared to the sky. The object keeps on flying and explodes on an altitude of 7.2 km, 92 km north of Vanavera. The explosion lights up the sky, even in London people notice it.
The stunning amount of forest devastation at Tunguska a century ago in Siberia may have been caused by an asteroid only a fraction as large as previously published estimates, Sandia National Laboratories supercomputer simulations suggest.
“The asteroid that caused the extensive damage was much smaller than we had thought,” says Sandia principal investigator Mark Boslough of the impact that occurred June 30, 1908. “That such a small object can do this kind of destruction suggests that smaller asteroids are something to consider. Their smaller size indicates such collisions are not as improbable as we had believed.”
Because smaller asteroids approach Earth statistically more frequently than larger ones, he says, “We should be making more efforts at detecting the smaller ones than we have till now.”
The Tunguska Event, or Tunguska explosion, was a powerful explosion that occurred not far from the Podkamennaya (Lower Stony) Tunguska River in what is now Krasnoyarsk Krai in Russia, at 0 hours 13 minutes 35 seconds Greenwich Mean Time (around 07:14 local time) on June 30, 1908 (June 17 in the Julian calendar, in use locally at the time).
The explosion is believed to have been caused by the air burst of a large meteoroid or comet fragment at an altitude of 5–10 kilometres (3.1–6.2 mi) above the Earth's surface. Different studies have yielded varying estimates of the object's size, with general agreement that it was a few tens of metres across.
The number of scholarly publications on the problem of the Tunguska explosion between 1908 and 2009 may be estimated at about 1,000 (mainly in Russian). Many scientists have participated in Tunguska studies, the best-known of them being Leonid Kulik, Yevgeny Krinov, Kirill Florensky, Nikolay Vasiliev, and Wilhelm Fast.