Near-Earth asteroid

Near-Earth asteroids are asteroids whose orbit intersects Earth's orbit and which may therefore pose a collision danger, as well as being most easily accessible for spacecraft from Earth. In fact, some near-Earth asteroids can be reached with much less ΔV than the Moon. The most famous near-Earth asteroid is 433 Eros that was visited by NASA's Near Earth Asteroid Rendezvous probe.

Asteroid orbit classification

• Atens
• Apollos
• Amors

"Near-Earth asteroid" is a more restrictive term than "near-Earth object."

External Link
JPL Near Earth Asteroid Tracking program (NEAT)

Example On 2002 Jun 6 an object with an estimated diameter of 10 meters collided with Earth. The collision occurred over the Mediteranean Ocean. The energy released was comparible to a small atomic bomb. At that time India and Pakistan were at a heightened state of alert, ready to iniate a nuclear weapon war with each other. If this asteroid impact had hit in this area the results might have been catastrophic.

Frequency Ateroids with a 1 kilometer diameter hit the Earth a few times in each million year interval. Large collisions with 5 kilometer objects happen every ten million years. Small collisions (but still potentially dangerous ones) occur a couple times each month.