A man in Moscow looks at a computer screen displaying a picture reportedly taken in the Urals city of Chelyabinsk, showing the trail of a falling object above a residential area of the city.
"This type of event, in general, is very extraordinary -- probably [occurring] once per 30 or 40 years -- and it can happen anywhere, in any part of the world. The largest recorded explosion of a space object was the famous Tunguska event in 1908. That was 5,000 kilometers east of Chelyabinsk. It's very, very rare."
