70% of the meteorites that landed on Earth came from a small number of collisions in the asteroid belt

A new study reveals that most of the meteorites on Earth were formed as a result of collisions that occurred in the asteroid belt in the last tens of millions of years. The discovery provides new insights into the origins of meteorites and the possible threat to Earth

An international team led by three researchers from CNRS, the European Southern Observatory (ESO, Europe) and Charles University (Czech Republic) showed that 70% of all known meteorites originate from three young families of asteroids. These families were formed in three collisions that occurred in the main asteroid belt about 5.8, 7.5 and 40 million years ago. The team also discovered the origins of other types of meteorites; Through this research, the origin of more than 90% of meteorites has now been identified. This discovery is described in three papers: the first was published on September 13, 2024 in the journal Astronomy and Astrophysics, and two additional articles will be published on October 16, 2024 in the journal Nature.

An international team of researchers has shown that 70% of all known meteorites originate from three young families of asteroids (Carin, Coronis and Massalia), which were formed following collisions in the main asteroid belt about 5.8, 7.5 and 40 million years ago. In particular, the Massalia family has been identified as the source of 37% of known meteorites.

Although there are more than 70,000 known meteorites, only 6% of them have been clearly identified by their composition (achondrites) as coming from the Moon, Mars or Vesta, one of the largest asteroids in the main asteroid belt. The origin of 94% of the remaining meteorites, most of them ordinary chondrites, remains unidentified.

Why are these three young families the source of so many meteorites?

This can be explained by the life cycle of asteroid families. Young families are characterized by an abundance of small fragments left over from the collisions. This abundance increases the risk of further collisions between the fragments, and together with their high mobility, increases the chance of escaping the asteroid belt, most likely towards Earth. The asteroid families formed from older collisions, however, are "sparse sources" of meteorites. The small fragments that characterized them eroded over time and disappeared following millions of years of collisions and their dynamic evolution. Thus, Karin, Coronis and Massalia are expected to share space with new sources of meteorites from future collisions and eventually give way to them.

A method for tracing the family tree of meteorites and asteroids

This historic discovery was made possible thanks to a telescopic survey of the composition of all the main asteroid families in the asteroid belt, combined with advanced computer simulations of the collisional and dynamic evolution of these families. This approach was extended to all meteorite families, revealing the main sources of carbonaceous chondrites and achondrites, in addition to meteorites from the Moon, Mars, and Vesta.

Thanks to this research, it was possible to identify the origin of more than 90% of the meteorites. In addition, it allowed scientists to trace the origin of asteroids with a diameter of kilometers - a size that threatens life on Earth. These objects are the object of many space missions (NEAR Shoemaker, Hayabusa1, Chang'E 2, Hayabusa2, OSIRIS-Rex, DART, Hera and more). In particular, the asteroids Ryogo and Benu, recently sampled by the Hayabusa2 (JAXA) and OSIRIS-REx (NASA) missions and studied in laboratories around the world, particularly in France, appear to be derived from the same ancestral asteroid as the Polana family.

The origin of the remaining 10% of known meteorites is still unknown. To address this, the team plans to continue the research, this time focusing on characterizing all the young families formed less than 50 million years ago.

From the Marseille Astrophysics Laboratory (University of Aix-Marseille/CNRS/CNES).
Meteorites containing silicates, which make up about 80% of all known meteorites.

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for the scientific article

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