What is a Near-Earth Object (NEO)?
Q: What is a Near-Earth Object (NEO)?
A: A Near-Earth Object (NEO) is an object in the Solar System whose orbit brings it close to the Earth. It can include near-Earth asteroids, near-Earth comets, some solar-orbiting spacecraft, and meteoroids large enough to be tracked in space before striking the Earth.
Q: How close does a NEO have to be from the Sun?
A: The least distance of a NEO from the Sun, its perihelion, must be less than 1.3 AU.
Q: What happens when a NEO collides with Earth?
A: Most of these meteors explode harmlessly in the upper atmosphere but some are dangerous and can cause significant destruction on impact.
Q: What was an example of a destructive NEO collision?
A: On 30 June 1908, a meteorite of around 45 metres in diameter exploded over the basin of the Podkamennaya Tunguska River releasing an energy of 10–15 megatons of TNT and destroying roughly 2,000 square kilometres of forest.
Q: How often does an event like this occur?
A: The Association of Space Explorers estimates that a Tunguksa-like event happens two or three times every thousand years on average.
Q: What is believed to have caused one of Earth's greatest extinction events?
A: An asteroid roughly 10 km in diameter is thought to have hit Earth 66 million years ago and caused the K/T extinction event, including the extinction of all non-avian dinosaurs.
