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How do near-Earth asteroids create an impact hazard for Earth?

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Illustration showing the eight planets of the solar system in order from the Sun-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune-depicted to scale by size, with labeled diameters in miles and kilometers. The Sun is partially visible on the left for comparison. — Solar system The planets (in comparative size) in order of distance from the Sun.

Near-Earth asteroids (NEAs) create an impact hazard primarily because their orbits around the Sun cross or closely approach the orbit of Earth. These objects, which include Aten and Apollo asteroids, move through the inner solar system and may eventually collide with a planet.21

The severity of the hazard depends on the object's size:
* Regional devastation: Objects roughly 100 metres in diameter can cause significant regional damage and are estimated to strike Earth once every 1,000 years.3
* Global catastrophe: Asteroids larger than 1 km (0.6 miles) are considered "planet-killers." A collision of this magnitude could release the energy of several hydrogen bombs, causing global climate disturbances, tsunamis, and potential mass extinction. Such events are estimated to occur on timescales of 100,000 years or longer.2143

Scientists monitor these threats through planetary defense programs, using the Torino Impact Hazard Scale to quantify risk and developing mitigation strategies, such as the Double Asteroid Redirection Test (DART), to deflect potentially hazardous objects.54