Throughout history, the Earth has been hit continuously by meteorites, the origins of which had largely been unknown. Recently, that’s changed. Scientists in 2024 have worked out where the majority have come from, with surprising results.

Scientists now know the origin of more than 70% of meteorites. Previously, only 6% of meteorites had a known origin. Scientists knew that this fraction of meteorites came from the Moon, Mars and Vesta – Vesta is one of the largest objects in the main asteroid belt, which sits between the orbits of Mars and Jupiter.

Through three different studies, scientists have found the origins of more than 70,000 meteorites which have been found on Earth. The research, published in three papers – the journal  Astronomy and Astrophysics, and a further two in Nature –  shows that the meteorites came from three recent collisions in the main asteroid belt.

The studies, which were made possible by using telescopic surveys of major asteroid families in the belt, found that the collisions occurred 5.8, 7.5 and 40 million years ago. This corresponds to three asteroid “families,” known as Karin, Koronis and Massalia, which formed from the destruction of asteroids more than 30 km across. The collisions help explain the majority of meteorites currently falling to Earth.

Younger asteroid families typically have a large number of fragments that are left over from the collisions that formed them. Typically, these pieces are highly mobile and, as such, can escape the gravitational field of other objects in the asteroid belt, which flings them into space.

What meteorites are predominantly made of can help discover where they originated.

Meteorites are made of different types of chondrites, including carbonaceous chondrites, also known as C chondrites (such as the ones found on the Moon and Mars),  H chondrites, and L chondrites. H chondrites make up about 40% of meteorites, and L make up about 35% of known meteorites. However, which meteorites the chondrites came from has only recently been discovered.

The studies found that 37% of meteorites came from the Massalia family. These include L chondrites from a collision 40 million years ago, which helped determine the origins of the meteorites. Researchers found that the family also includes much older meteorites from a collision about 450 million years ago.

Researchers are also using these studies to track the origins of asteroids that could threaten life on Earth which are a kilometre or more across.