Although most asteroids drift harmlessly around the Sun for billions of years, some are occasionally knocked out of their orbits. Some of these asteroids pass very close to Earth. In 1994, an asteroid measuring 10m (32ft) in diameter passed within 105,000km (65,000 miles) of our planet — around one third of the distance to the Moon. If a large asteroid were to collide with Earth, the impact could he powerful enough to annihilate all life on the planet. Vast waves of water, dust and fire would flatten cities in seconds, and billions of tonnes of dust entering the atmosphere would block out the Sun’s light for hundreds of years.
This is a list of examples where an asteroid or meteoroid travels close to the Earth. Some are regarded as potentially hazardous objects if they are estimated to be large enough to cause regional devastation.
Near-Earth object detection technology greatly improved about 1998, so objects being detected as of 2004 could have been missed only a decade earlier due to a lack of dedicated near-Earth astronomical surveys. As sky surveys improve, smaller and smaller asteroids are regularly being discovered. The small near-Earth asteroids 2008 TC3, 2014 AA, 2018 LA and 2019 MO are the only four asteroids discovered before impacting into Earth (see asteroid impact). Scientists estimate that several dozen asteroids in the 6–12 m (20–39 ft) size range fly by Earth at a distance closer than the moon every year, but only a fraction of these are actually detected.