This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

07 March 2008

Commentary on Tunguska from Alexander Bagrov

Selections from the article (written by Doctor of Physics and Mathematics, Alexander Bagrov, research associate of the Astronomy Institute of the Russian Academy of Sciences)....

The Tunguska blast was the largest meteoroid impact in the Earth's recent history, and demonstrated the awesome destructive power of near-space objects. An explosion of the scale of the one in Tunguska could destroy large metropolitan areas. It is this possibility that has helped to spark discussion of asteroid deflection strategies.

Due to the rotation of Earth, if the collision had occurred 4 hours 47 minutes later, it would have completely destroyed the Imperial Russian capital, St. Petersburg. A little later still, and the Tunguska meteorite would have wreaked chaos and destruction in densely populated Europe. Although scientists have advanced over 80 theories explaining the Tunguska event, none of them offers any conclusive evidence. Moreover, it is now impossible to verify them.

When I became an astronomer 30 years ago, I believed that the mystery of the Tunguska meteorite would never be solved. However, astronomers have since then obtained additional information about the origin of celestial bodies, and can offer more convincing explanations for the Tunguska blast.

I am going to tell an upcoming international conference in Moscow to mark the 100th anniversary of the Tunguska event that it was most likely caused by a comet fragment consisting of the Solar System's primary matter.

There are two kinds of comets in our Solar System. "Primary" comets consist of micron-sized inter-stellar dust and gas, whereas "secondary" comets feature meteorite substance. A disintegrating "secondary" comet forms the meteor showers that are frequently observed from the Earth. Some of their fragments do not burn up during reentry and can be recovered. On February 12, 1947, a large meteorite disintegrated spilled fragments over a 1.3-sq. km. area in the Sikhote-Alin range, some 440 km from Vladivostok in the Russian Far East. Subsequent expeditions recovered many iron fragments there.

The Astronomy Institute's experts and I believe that if the Tunguska meteorite were a "secondary" comet, then it would have contained several metric tons of meteor substance, and some of it could have been recovered.

It would be therefore logical to assume that the Tunguska meteorite was a huge gas-and-dust snowball, whose tiny fragments vaporized after hitting the terrestrial atmosphere. The remaining comet-nucleus also vaporized instantly, causing the loud and powerful air burst that was registered by many observatories all over the world.

When a "primary" comet blows up, surviving comet-nucleus particles, including tiny hard-to-melt dust, are dispersed in the Earth's atmosphere, subsequently becoming embedded in tree bark. Unfortunately, scientists in 1908 lacked modern methods for detecting space-bolide substances.

Tunguska meteorite: a warning from outer space
06 March 2008
Opinion & analysis
RIA Novosti

Link: RIA Novosti Article

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