In 2013, a fireball exploded over Chelyabinsk, Russia. No one saw it coming. Even though NASA has been able to identify over 14,000 near-earth objects, its asteroid tracking technology is not completely ready to see everything that heads towards the Earth.
NASA's Planetary Defense Coordination Officer Lindley Johnson told Headlines & Global News about the unsettling reasons why.
Produced by Ruchika Agarwal and Jessica Orwig
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