[ad_1]
In 2016, the United Nations designated June 30 of every year as “Asteroid Day” to raise public awareness about the asteroid impact hazard. But why June 30? Because it falls on the anniversary of the Tunguska, a massive 12-megaton explosion that happened in Siberia in Russia.
What was the Tunguska explosion?
In 1908, a man was sitting on the front porch of a trading station in Vanavara in Siberia. In a few moments, he was hurled from his chair to the ground and it was so hot that he felt his shirt was on fire. That is how an eyewitness describes the event while sitting more than 60 kilometres away from the epicentre, according to NASA.
On June 30 that year, a gigantic explosion near the Podkamennaya Tunguska River in the region flattened an estimated 80 million trees that covered an area of more than 2,150 square kilometres, according to CBC. The Siberian region is sparsely populated but eyewitness accounts from the time speak of a “sky split apart by fire.”
The event was followed by a powerful shockwave that broke windows hundreds of kilometres away and even knocked people off their feet, according to EarthSky. While the explosion was a spectacularly dramatic event, it was after a few decades that there was an explanation for it.
Trees radiating away from the epicentre of the explosion. (Image credit: Leonid Kulik via The Conversation)
The Tunguska impact event is interesting because the meteor did not leave behind a crater. The best explanations for the event put it down to an asteroid or comet, about 50 metres in length, exploding in the atmosphere between six to ten kilometres above the surface. Scientists believe that the asteroid exploded in the atmosphere, creating what is known as an air burst.
The explosion released energy equivalent to 185 times that was released during the Hiroshima atomic bombing, according to The New Yorker.
Why did it take so long to explain the Tunguska explosion?
The impact happened in 1908 but scientists only reached the area for the first time around 19 years later, according to NASA. After a previous attempt to reach the area was thwarted by the harsh Siberian winter, Leonid Kulik, chief curator for a meteorite collection at the St. Petersburg museum at the time, reached there in 1927.
According to Don Yeomans, a retired planetary scientist at NASA, the locals were hesitant to talk to Kulik about the event, believing that the blast was caused by the god Ogdy who cursed the area by smashing trees and killing animals.
Even though eyewitness accounts may have been difficult to obtain, there was enough evidence to go around. Eight million trees were lying on the floor and they created a radial pattern which pointed directly away from the epicentre of the blast.
According to some estimates, the asteroid entered our planet travelling at a speed of more than 53,00 kilometres an hour. The nearly 100,000-kilogram asteroid would have heated the air around it to a temperature of around 25,000 degrees Celsius. At around 7.17 AM Siberia time on that day, the combination of pressure and heat would have caused the asteroid to explode, producing a fireball and releasing all that energy.
[ad_2]
