NASA: Avoiding Planetary Asteroid Hits Is A Big Job

Avoiding Planetary Hits Is A Big Job

The Scope of the Hazard
Near-Earth objects are asteroids and comets that orbit the Sun and approach or cross Earth's orbit. An asteroid or comet about 10 kilometers in diameter struck the Yucatan peninsula 65 million years ago and caused global devastation, probably wiping out large numbers of plant and animal species including the dinosaurs. Objects as large as this one strike Earth only about once every 100 million years on average, the report notes.

NASA has been highly successful at detecting and tracking objects 1 kilometer in diameter or larger, and continues to search for these large objects. Objects down to sizes of about 140 meters in diameter - which NASA has been mandated to survey for - would cause regional damage; such impacts happen on average every 30,000 years, the report says.

While impacts by large NEOs are rare, a single impact could inflict extreme damage, raising the classic problem of how to confront a possibility that is both very rare and very important. Far more likely are those impacts that cause only moderate damage and few fatalities.

Conducting surveys for NEOs and detailed studies of ways to mitigate collisions is best viewed as a form of insurance, the report says. How much to spend on these insurance premiums is a decision that must be made by the nation's policymakers.