Asteroids: between a rock and a hard place
In February 2013, a large asteroid ripped over the Chelyabinsk district of Russia, trailing cartoonish lines of smoke as it made its shallow entry, radiating so much light and heat that onlookers were left with reddened faces. Skin peel. When the asteroid exploded, 15 miles up, there was a terrible, prolonged bang – a noise that has rung on, in its way, ever since.
We now know that the explosion over Chelyabinsk occurred with a force equal to 500 kilotons of TNT, or a couple of dozen Nagasaki bombs
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a Nasa scientist called Bill Cooke said the likely frequency of such meteor strikes was being re-evaluated. That month, a trio of studies published in the journals Nature and Science suggested impacts of Chelyabinsk's magnitude were between three and 10 times more likely to happen than previously supposed.
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Chelyabinsk in 2013. Sudan in 2008. Impacts over Indonesia, Egypt, Australia, Argentina, California and Finland; four in the north Pacific and three in the south, two in the south Atlantic and one in the north, four in the Indian Ocean, one in the Med, one in the Arabian Sea, one in the Tasman and one off Antarctica. Call them what you like – "city‑killers" or "pesky ones" – there have been 26 meteorite strikes since the turn of the century that were large enough to cause a kiloton-class pop.
Lu believes we should be worried by that.
http://www.theguardian.com/science/2014/sep/20/asteroids-rock-hard-place-meteor-strike-russia-nicaragua
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