February 16, 2013
AN EARTH-SHATTERING KABOOM: Estimates raised for nuclear-sized asteroid blast that hit Russia. “Scientists have raised their estimates of the size and power of what turns out to be the most widely witnessed asteroid strike in modern history. The size estimate puts the object that caused Friday’s meteor blast over Russia in a troublesome category of asteroids: big enough to cause damage, but small enough to evade detection. The new estimates, based on additional readings from a sensor network built to detect nuclear blasts, suggest the meteor released the energy equivalent of nearly 500 kilotons of TNT. That’s about 30 times the power of the Hiroshima atomic bomb.”
UPDATE: A reader emails:
The relative lack of ground-level damage from a explosion equivalent to 30 Hiroshima bombs is due to its occurence about 25 miles above ground. And the reason it exploded so high up is that it came in at a shallow angle (20 degrees). If the approach had been steeper (less time in the atmosphere), it would have gotten closer to the ground before exploding. The folks in Chelyabinsk were very lucky.
True. And we were all lucky, in that if something like this had happened at the height of the Cold War it might have ignited a nuclear exchange.
And another reader writes: “Don’t forget in all the worry about asteroids, that a Carrington event could be devastating as well.” True enough.