A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the object enters the atmosphere, various factors like friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and emit light, thus creating what is commonly called a “shooting star” or “falling star”. Meteorites are distinguished from meteoroids by their size; meteoroids are bodies in space that are at most one meter across, whereas meteorites can range in size from microscopic dust particles to gigantic boulders.
Meteorites have been found on all of the terrestrial planets and on most of their moons. In contrast, very few meteoroids make it to Earth intact; instead they burn up in our atmosphere or break apart before reaching the ground. It is estimated that only about 500 tonnes of extraterrestrial material falls on Earth each year (most of which is dust). Nevertheless, this small amount can still have a significant impact; for example, when a large meteorite exploded over Chelyabinsk Russia in 2013 it caused widespread damage and injured over 1 000 people.
The vast majority of known meteorites are fragments of asteroids that have broken apart due to collisions or other disruption events. The largest asteroid fragment so far identified is 4 Vesta which lost a large chunk of itself during an impact event around 1 billion years ago; this fragment ended up becoming the HED (howardite-eucrite-diogenite) family of meteorites. However, not all asteroids produce fragments when they break up; sometimes they simply grind themselves down into smaller pieces through collisions with other objects (this process is called comminution). Over time these smaller pieces can become so fine that they form what are known as “dustballs”; these objects eventually drift into stable orbits around stars where they may be observed as circumstellar disks made up of dusty debris.