Scientists studying the meteor that exploded over a Russian city on February 15 say the threat of asteroids smashing into Earth is bigger than previously thought.
Studies published on November 6 in the journals "Nature" and "Science" say that meteors the size of the one that exploded over Chelyabinsk -- and others even larger and more dangerous -- are probably four to seven times more likely to hit the planet than scientists previously assumed.
NASA scientist Paul Chodas told a news conference on November 6 that some 20 million meteors the size of the Chelyabinsk asteroid may be traveling around the solar system, instead of 3 million.
Scientists said the Chelyabinsk meteor was only 19 meters across but exploded with the force of 40 Hiroshima-type atomic bombs.
Experts say early warning systems need to be put in place.
Based on reporting by AP, AFP, and the BBC