12-07-2008 Tunguska 100 years later (Article 145)

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Simon Kenny
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12-07-2008 Tunguska 100 years later (Article 145)

Post by Simon Kenny » Wed Dec 31, 2008 10:28 am

Tunguska 100 years later (Article 145)

On the 30 June 1908 shortly after 7:00 AM in central Siberia the largest impact of a cosmic object on Earth, during modern human history, took place. Over time the Earth has suffered cosmic impacts, which have changed the course of evolution. About 65 million years ago it is thought that the extension of the dinosaurs occurred as the result of a cosmic object impacting with the Earth. It is also thought that about 4.4 billion years ago an even greater impact with the Earth resulted in a large size chunk being thrown off, which resulted in the formation of the Moon.

It is still not known what caused the Tunguska event — but it is generally thought that it was either an asteroid or a comet. What is known is that a large area of uninhabited forest was completely flattened and an eyewitness account spoke of a huge explosion high in the atmosphere — the sky appearing to ‘split open’. Brilliantly coloured sunsets and massive silvery clouds were reported in Asia and Northern Europe over he following weeks. It is claimed that newspapers could be read in London at midnight!

Several expeditions to the extremely remote site were made over the years — the first in 1927 discovered a large area of about 2000 square kilometres, where millions of trees were flattened. However, no evidence could be found of an impact crater nor any pieces of the cosmic object could be found. It was even speculated that an alien spacecraft had exploded!


All that may be about to change as a team of Italian scientists have speculated, from evidence collected on field trips, that a lake (Lake Cheko) near the impact site is the possible site of the impact crater. A trip, planned for later this year, will try to drill into the centre of the lake to reach a dense seismic reflector, which may finally solve the mystery surrounding Tunguska.

If the Tunguska event had taken place during the cold war period (circa 1947 - 1990) it is possible that it could have been mistaken for a nuclear attack on the then Soviet Union that could have resulted in a nuclear war between the major military powers. Calculations have put the impact at the equivalent of about 1000 Hiroshima atomic bombs.

While the possibility of nuclear war has receded, impacts from cosmic objects are still a real possibility. Apophis, a 300 metre long asteroid discovered in December 2004, will miss the Earth by about 37000KM/s on Friday 13 April 2029. The ‘fly by’ will reach a magnitude of 3.3 and will be a naked eye object visible over Europe. Calculations vary but best estimates put the energy released, if Apophis was to hit Earth, at about 100 times that of Tunguska. Apophis will return again in 2036 for another close encounter. Don’t forget your 7th April 2029 edition of the Limerick Leader, as the Shannonside Astronomy Club will have all the latest news on Apophis.

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