ONE close shave with an asteroid is cause for excitement. Two on the same day is scary. On February 15th 2013 planet Earth experienced exactly that, as a hunk of itinerant space rock passed by extremely close, while another exploded spectacularly in the skies above Russia.

The first asteroid, called 2012 DA14, had been known to astronomers for around a year. They had calculated that there was no risk of collision. But the 30-metre, 190,000-tonne rock came close: 27,700km (17,200 miles) above the surface, inside the orbit of some satellites. It was the nearest ever recorded for an asteroid that size.

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The second came quite literally out of a clear blue sky, appearing without warning and then disintegrating about 30 seconds later over Chelyabinsk. According to NASA, the 10,000-tonne meteor released about 500 kilotonnes of energy when it broke apart, equivalent to the yield of a largish nuclear bomb. Only the height of the detonation—dozens of kilometres up—kept the fatality count at zero, although more than 1,000 people were injured as windows were blown out of buildings.

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Video link: Sky News

Text: The Economist Website