Largest Asteroids Near Earth

Why Does Size Matter?

An asteroid's size is one of the most critical factors in assessing impact hazard. The energy released on impact scales with mass × velocity² — and mass scales with the cube of diameter. A 200m asteroid carries roughly 8 times more kinetic energy than a 100m object at the same speed.

NASA's PHA threshold of 140 meters is not arbitrary — objects below this size tend to disintegrate in the atmosphere (becoming fireballs or meteor showers), while larger objects can cause significant ground damage. A 140m impact on land would release energy equivalent to a large nuclear weapon.

Objects above 1 km are considered globally dangerous — an impact would cause climate disruption, agricultural collapse, and mass casualties. No known asteroid above 1 km is currently on a collision course with Earth.