Small, extraterrestrial bodies, most of which probably originate in the asteroid belt, that enter the Earth’s atmosphere and land on the surface. Most are only a few centimetres in size. Meteorites are classified into four main groups according to their composition and structure as: chondrites; achondrites; stony-irons; and irons. See also antarctic meteorite; aubrite; basaltic meteorites; carbonaceous chondrite; eucrite; shergottyite/nakhlite/chassignite meteorites; stony meteorite; tektite.