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NASA Warns: 15,000 Undetected 'City-Killer' Asteroids Loom

2/17/2026

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Summary

Story summary

Dr. Kelly Fast, NASA's head of planetary defense, says about 15,000 'city-killer' asteroids remain undetected.
These asteroids are at least 140 meters wide and could cause damage if they impact populated areas.
The DART mission altered an asteroid's orbit, but no other spacecraft are ready if a threat is identified.
NASA aims to find over 90% of near-Earth objects (NEOs) larger than 140 meters through its upcoming NEO Surveyor mission.

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Story summary

Dr. Kelly Fast, NASA's head of planetary defense, says about 15,000 'city-killer' asteroids remain undetected.
These asteroids are at least 140 meters wide and could cause damage if they impact populated areas.
The DART mission altered an asteroid's orbit, but no other spacecraft are ready if a threat is identified.
NASA aims to find over 90% of near-Earth objects (NEOs) larger than 140 meters through its upcoming NEO Surveyor mission.