© Eduard Kalinin
A hole blasted through the ice of Lake Chebarkul, southwest of Chelyabinsk, Russia, by a meteorite.
When an asteroid exploded over the Russian city of Chelyabinsk in February
, shattering windows for miles and injuring well over 1,000 people, experts said it was a rare event - of a magnitude that might occur only once every 100 to 200 years, on average.
But now a team of scientists is suggesting that the Earth is vulnerable to many more Chelyabinsk-size space rocks than was previously thought.
In research being published Wednesday by the journal Nature
, they estimate that such strikes could occur as often as every decade or two.
The prospect "really makes a lot of people uncomfortable," said Peter G. Brown
, a professor of physics and astronomy at the University of Western Ontario and an author of the two studies
. A third paper by other scientists describing the Chelyabinsk explosion was published online this week by the journal Science
The findings are helping to elevate the topic of planetary defense - identifying dangerous asteroids and deflecting them if necessary - from Hollywood fantasy to real-world concern.