KABOOM! – 100 years on

On the 30th June 2008 – 100 years ago today – a chunk of rock & ice was casually making its way across the solar system when a planet called Earth rudely decided to get in its way.

It entered the atmosphere travelling approximately towards the west, at a speed of thousands of miles per hour. Beaten by massive forces, the object reached a few miles from the surface before exploding like a megaton bomb. The air blast – the shock wave produced by a large explosion – flattened trees for roughly 800 square miles around ground zero.

Witnesses reported that the ground immediately shook, followed by a wind of heat – felt miles away. The shock wave propagated around the world. The “impact” happened in the remote Siberian Krasnoyarsk Krai region – an area of swampland and the Podkamennaya Tunguska River. Had it happened over a populated area such as Moscow or St Petersburg, around a million people could have been killed.

It is now known as the Tunguska Event and is a relatively comtemporary example of how much of a cosmic shooting range the Earth sits in.

The event has been studied comprehensively since then. After the immediate impact, little interest was taken due to the remote nature of the region. (it is thought a expedition may have taken place soon after but any record of it was lost in the subsequent turbulant times of post World War One Russia).

In the 1920s the first recorded expeditions took place. Leonid Kulik, a mineralogist and geologist of the Soviet Academy, travelled to Tunguska to the region. He took accounts from locals and deduced the explosion had been caused by a meteorite impact.

However his studies revealed no crater, only a 30 miles region of scorched and flattened trees, stripped of bark. These were the first clues that it was an air blast. He continued to receive funding for his expeditions as he had persuaded the Soviet government based on the prospects of finding a valuable iron source from the impacted object.

No debris, or crater, has ever been conclusively identified at Tunguska, leading to debates over the nature of the object – was it a rocky asteroid or an icy comet? Recent spacecraft surveys of asteroids have shown that some resemble fragile piles of rubble, which may more easily explode in such an event.

Later expeditions found microscopic glass spheres soil samples. Chemical analysis showed that the spheres contained high proportions of nickel and iridium. These elements are found in high concentrations in meteorites, hinting that they could likely be of extraterrestrial origin – part of the

The Earth has come a long, long way in the hundred years since that morning in Northern Russia. But if another similar object was incoming, we likely wouldn’t know about until we, like the Siberian locals, saw a flash of light in our sky, felt the waves of hot air, and were knocked down by the ground shaking.

The odds of it happening again soon are quite low. But this anniversary should remind us that it can and will happen again.


Posted on 30 June, 2008, in Astronomy News, Space exploration and tagged , , , , . Bookmark the permalink. Comments Off on KABOOM! – 100 years on.

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