A global group of researchers, including three from CNRS1, the European Southern Observatory (ESO), and Charles University in the Czech Republic, has revealed that 70% of all registered meteorite falls come from only three young asteroid families. These families were formed following recent collisions in the main asteroid belt approximately 5.8, 7.5, and around 40 million years ago. The team also identified the origins of other meteorite types, now clarifying the sources of over 90% of meteorites. The findings are published in three papers, with the first appearing on September 13, 2024, in the journal Astronomy and Astrophysics, and two additional papers scheduled for publication on October 16, 2024, in Nature.
A team of international scientists has discovered that 70% of all recognized meteorite falls come from three young asteroid families—Karin, Koronis, and Massalia—formed by collisions in the main asteroid belt 5.8, 7.5, and about 40 million years ago. Notably, the Massalia family accounts for 37% of all known meteorites.
Despite the identification of more than 70,000 meteorites, only 6% have been clearly linked to particular sources like the Moon, Mars, or Vesta, one of the largest asteroids. The sources of the remaining 94% of meteorites, primarily ordinary chondrites2, were previously unrecognized.
Why do these three young asteroid families contribute to so many meteorites?
This phenomenon can be clarified through the life cycle of asteroid families. Young asteroid families have a large number of small fragments resulting from collisions, increasing the chances of these fragments colliding with one another. Their high mobility allows many to escape the asteroid belt, potentially heading toward Earth. Conversely, older asteroid families, created by earlier collisions, are seen as “depleted” sources of meteorites. Over time, the small fragments that once made up these older families have diminished due to countless collisions and natural evolution. Consequently, families like Karin, Koronis, and Massalia coexist with newer sources from more recent collisions and will gradually give way to them.
A technique for mapping the lineage of meteorites and asteroids
This groundbreaking finding was achieved through a comprehensive telescopic survey examining the composition of major asteroid families in the main belt, paired with cutting-edge computer simulations modeling their collisional and dynamic evolution. This methodology was broadened to include all meteorite families, uncovering primary sources of carbonaceous chondrites and achondrites beyond those from the Moon, Mars, and Vesta.
This research has confirmed the origins of over 90% of meteorites and has allowed scientists to trace the origins of kilometer-sized asteroids, which pose potential threats to life on Earth. These larger objects are the focus of various space missions, such as NEAR Shoemaker, Hayabusa1, Chang’E 2, Hayabusa2, OSIRIS-Rex, DART, and Hera. Notably, the asteroids Ryugu and Bennu, which were recently sampled in the Hayabusa2 and OSIRIS-REx missions and analyzed globally, including in France, trace back to the same parent asteroid as the Polana family.
However, the sources of the remaining 10% of known meteorites are still a mystery. To address this, the team intends to further their research by characterizing all young asteroid families that were formed within the last 50 million years.
- From the Laboratory of Astrophysics of Marseille (Aix-Marseille Université/CNRS/CNES).
- Meteorites made up of silicates, which constitute about 80% of all known meteorites.
