A meteoroid in outer space is a small
rocky or metallic body. Meteoroids are substantially smaller than asteroids,
ranging from small grains to objects one meter wide. Objects smaller than this
are classified as space dust or micrometeoroids.
Meteoroids crash into these bodies,
creating craters and throwing back into the solar system space dust (more
meteoroids). Most meteoroids are made from silicon and oxygen (minerals known
as silicates) and heavier metals such as nickel and iron.
Read: How does a meteor, a meteor, a meteorite, an asteroid, and a comet differ?