http://en.rian.ru/science/20080630/112598958.html
Acid rain traces support meteor theory for 1908 Tunguska blast
MOSCOW, June 30 (RIA Novosti) - International researchers investigating the
Tunguska Event, an explosion exactly 100 years ago in central Siberia, say acid
rain traces in the region back up the theory that the blast was caused by a
meteorite.
On June 30, 1908, an explosion equivalent to between 5 and 30 megatons of TNT
occurred approximately 7-10 km (3-6 miles) above the Podkamennaya Tunguska
River in a remote Siberian region.
"Extremely high temperatures occurred as the meteorite entered the atmosphere,
during which the oxygen in the atmosphere reacted with nitrogen causing a build
up of nitrogen oxides," one of the authors of the joint research, Natalia
Kolesnikova, told RIA Novosti.
Kolesnikova said a similar impact 66 million years ago wiped out a significant
portion of life on Earth, including the dinosaurs.
The Tunguska blast flattened 80 million trees, destroying an area of around
2,150 sq km (830 sq miles). However, despite the shockwaves being detected as
far away as the United Kingdom, the Tunguska Event went largely unnoticed,
eclipsed by global events leading up to WWI, the Russian Revolution and
subsequent civil war.
If the explosion had occurred some 4 hours and 47 minutes later, due to the
Earth's rotation it would have completely destroyed the then Russian imperial
capital of St. Petersburg.
It took almost 20 years, until 1927, before a research expedition led by Leonid
Kulik, a leading meteorite expert at the Academy of Sciences, first managed to
visit the remote Siberian region and see the awesome destruction caused by the
blast, and to take witness statements from locals living in the area.
It was assumed that a huge meteorite had hit the area, although Kulik failed,
during his research in Siberia, to find an obvious crater.
In 1930, a British astronomer suggested the blast could have been caused by a
small comet, composed of ice and dust, which would have been vaporized on
impact with the Earth's atmosphere.
The research carried out by the Moscow State Lomonosov University, Italy's
Bologna University and Germany's Center for Environmental Research in Leipzig
backs up the most likely theory of a meteor explosion.
However it is unlikely to put a stop to speculation on theories ranging from
alien attacks, UFOs, antimatter, doomsday events and black holes.
The Tunguska mystery - 100 years on. What caused the explosion? (Poll)
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