26 nuclear-scale explosions from untracked asteroids
Asteroids hitting the Earth caused 26 nuclear-scale explosions between 2000 and 2013, a new report reveals.
Some were more powerful – in one case, dozens of times stronger – than the 15-kiloton atom bomb blast that destroyed Hiroshima in 1945.
The impacts were recorded by the Nuclear Test Ban Treaty Organisation which operates a global network of sensors listening out for nuclear weapon detonations.
Most occurred too high in the atmosphere to cause any serious damage on the ground. But the evidence is a sobering reminder of how vulnerable the Earth is to the threat from space, say scientists.
None of the asteroids was detected or tracked in advance by any existing space or Earth-based observatory.
Former astronaut Ed Lu, who spoke about the new data at a Press briefing at the Museum of Flight in Seattle, US, said: "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."
Dr Lu is co-founder and chief executive of the B612 Foundation, a research body dedicated to finding ways of protecting the Earth from dangerous asteroids.
The most dramatic asteroid impact in recent times occurred when an object exploded over Tunguska, Siberia, in 1908 with an energy yield equivalent to between 5,000 and 15,000 tons of TNT.