On June 30, 1908, Russia was the setting for a major, although relatively localized, catastrophe. That morning, at 7:17 local time, a ball of fire crossed the central Siberian sky. A few moments later, a powerful explosion occurred above the Stony Tunguska River, devastating a region of over 2,000 square kilometers, roughly five times the area of Montréal Island.
Luckily, the wooded, marshy region was practically deserted, and the catastrophe as a result left no human victims. Nevertheless, testimony collected after the events is startling.
A witness situated in a trappers’ station over 50 kilometers from the impact was thrown to the ground more than seven meters away by the blast of the explosion. The windows of the station were shattered, and the ground trembled. A shockwave equivalent to an earthquake measuring 5.0 on the Richter scale was recorded all over Europe, and even in America, following the explosion.
The noise of the blast spread for 1,500 kilometers, while a gigantic fireball could be seen over 700 kilometers from the blast location. In the days that followed, the sky was so bright in Russia and in Europe that people could read the newspaper in the middle of the night!
The Kulik expeditions
In 1927 a first scientific expedition traveled to the site, led by Leonid Kulik, a Russian mineralogist specializing in meteorites.
He was amazed to discover that, within a radius of 20 kilometers, 60 million trees had been destroyed. Damage could be observed over a radius of more than 100 kilometers. Despite intensive research in the course of six expeditions, Kulik was never able to find any crater traces or meteorite fragments.
In fact, it wasn’t until 1957 that dust was found from the meteorite that caused the enormous explosion: in the form of minuscule spheres of metal and silicate, encrusted in fragments of trees brought back by Kulik.
Asteroid or comet
Even today, the nature of the object that struck the Earth in 1908 remains unclear. However, our current knowledge of the celestial bodies that make up the solar system, combined with computer simulations, allow for a better understanding of what took place.
According to the hypothesis most widely accepted, it would have been a rocky object 50 meters in diameter – an asteroid or the nucleus of a comet – that disintegrated completely at an altitude of 10 kilometers. It was the shockwave generated by the explosion that lay waste to the region of the Tunguska River.
All the same we were lucky that day, because if the object had struck the Earth five hours later, the explosion would have taken place over the city of St. Petersburg. The town and its 1,700,000 inhabitants would have been wiped out.
It’s estimated that an event like Tunguska occurs once every 1,000 years. The Tunguska catastrophe demonstrates how important it is to track the asteroids that cross the orbit of our planet, so that we have a better chance of protecting ourselves from them.