Meteors have been battering the Earth for billions of years, ever since Earth formed, but only recently, in October 2024, have scientists found out where most of these cosmic space rocks came from.
Before these findings, the origin of only 6% of Earth’s meteorites was known. They came from the Moon, Mars, and Vesta – one of the largest objects in the main asteroid belt between Mars and Jupiter. But new studies show that 70% of the meteorites found on Earth come from three recent collisions in the main asteroid belt.
These collisions happened 5.8, 7.5, and 40 million years ago, according to the journal Astronomy and Astrophysics and two papers published in Nature.These collisions come from three young asteroid “families,” known as Karin, Koronis, and Massalia. An asteroid family is a group of asteroids with a similar orbit to each other, according to the European Space Agency. These families formed from the destruction of asteroids at least 30km across. These break-ups explain where most of the meteors currently falling to Earth came from.
Younger asteroid families have a large number of small fragments left over from the collisions that led to the asteroid family’s formation. Usually, these small pieces are also highly mobile, meaning they can escape the gravity of other objects in the asteroid belt and be flung into space.
Meteorites are made of chondrite. They come in different classes including carbonaceous chondrites (C chondrites – like those from the Moon and Mars), H chondrites and L chondrites. H chondrites are the most common, making up about 40% of known meteorites. L chondrites are the second most common at 35%. But which groups of asteroids the H and L chondrites came from has remained a mystery until now.
According to the scientist’s findings, 37% of meteors come from the Massalia family. This family is also responsible for much older meteors, from another collision 450 million years ago. The study also tracked the origins of asteroids more than a kilometer across, big enough to threaten life on Earth.