Most meteorites that fall to Earth's surface are believed to originate from the asteroid belt, between Mars and Jupiter; these meteorites are either knocked out of their orbit of the Sun by colliding with other objects, or are pulled out of orbit by the Sun's gravitational field. They are the remains of the "building blocks" of terrestrial planets, such as Earth, that never collected to form into a full-sized planet.

A handful of meteorites appear to come from the Moon and Mars. These meteorites are broken off when another object collides with the Moon or Mars with enough force to launch the debris away from the planet and into orbit around the Sun.

How do we know meteorites come from space?

Meteorites that come from the asteroid belt are about the same age as the solar system, approximately 4.5 billion years old. No Earth rocks are this old, because they have all been ground up and reformed repeatedly by erosion and the Earth's tectonic plate system.

Meteorites from Mars and the Moon are distinguished from Earth rocks and other meteorites by their chemical and mineral compositions and their age. Lunar meteorites are also distinguished by their resemblance to the lunar rocks brought back to Earth by the Apollo astronauts.