On the morning of June 30, 1908, the sky above Tunguska, Siberia, exploded.
“Suddenly in the north sky … the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire,” one eyewitness recounted in 1927.
“At that moment, there was a bang in the sky and a mighty crash…. The crash was followed by a noise like stones falling from the sky or of guns firing. The earth trembled.”
This was the renowned Tunguska event, the most recent devastating case of an asteroid colliding with Earth.
The asteroid, a 37-metre, 100,000-kilogram piece of rock entered our atmosphere at a neck-breaking 54,000 km/h, heating to 25,000 C. It released energy equal to 185 Hiroshima bombs.
The intense heat, together with the speed, generated intense air pressure that caused the asteroid to break apart. It left a bright fireball that one witness 64 kilometres away said made him feel like his shirt was on fire.
In the end, 2,072 square kilometres of forest were destroyed and 80 million trees levelled.
Though the Tunguska event was tragic for wildlife and the area’s forests, fortunately no one was killed, as it exploded over a remote area. But could one that’s big enough wipe us out?
Good news: It’s unlikely.
Thanks to a number of asteroid surveys, such as NASA’s Center for Near Earth Object Studies, there is a healthy inventory of large asteroids.
“We’ve found 95 per cent of all the really big, one-kilometre-sized asteroids,” said Peter Brown, professor of physics and astronomy at Western University in London, Ont.
“We’re going to know within the next couple of decades for sure if any time over the next century if there’s an asteroid that’s going to hit.”
Of course, there can’t be an absolute guarantee that a smaller asteroid wouldn’t impact Earth.
We got a dose of what a smaller one could do on Feb. 15, 2013 when a 20-metre piece of space rock exploded in the atmosphere over Chelyabinsk, Russia. Two minutes after it passed, an air blast shattered windows, injuring almost 1,000 people. Travelling nearly 70,000 km/h, it released energy equivalent to 30 Hiroshima bombs.
You can hear it in the video below.
One of the most…