A network of listening stations used to detect nuclear detonations, which is operated by the Nuclear Test Ban Treaty Organization, picked up 26 explosions on Earth during this period from the low frequency infrasound pulses that they emit. They ranged from 1 to 600 kilotons in energy. For the sake of comparison- the 1945 Hiroshima bomb had an energy impact of “only” 15, so some of these explosions were pretty big.
These results demonstrate that asteroid impacts are certainly not rare events. The fact that none of them caused any significant damage is sheer luck, however, the majority of them exploded too high for them to do much damage once when they hit the ground. Still, it highlights the need for an estimation of the frequency of an impact with a potentially devastating asteroid.
Some notable past events include the 1908 explosion over Tunguska, Siberia, which had an impact of between 5-15 megatons and flattened some 80 million trees, and the 2013 impact over the Russian city of Chelyabinsk which had an impact of 600 kilotons.
According to Dr. Ed Lu, who was one of the astronauts presenting the findings at the Seattle Museum of Flight yesterday, “While most large asteroids with the potential to destroy an entire country or continent have been detected, less than 10,000 of the more than a million dangerous asteroids with the potential to destroy an entire major metropolitan area have been found by all existing space or terrestrially-operated observatories.”
It’s not all doom and gloom; the B612 foundation are hoping to construct an infrared space observatory, the Sentinel Space Telescope, which would generate detailed maps of our inner solar system which could be used to detect asteroids early enough to deflect them. It is predicted to launch in 2018, so hold tight until then.
Check out the B612 asteroid visualization below: