A series of studies is expanding knowledge about the origin of meteorites, these extraterrestrial fragments that reveal a lot about the history of the solar system.
Until very recently, it was very clever who could say about the exact origin of the approximately 70,000 meteorites, these pieces of rocks, metals
or both, which reached the earth’s surface after having partially disintegrated on contact with the atmosphere. Barely 6% of them could be clearly linked, thanks to their composition, to the Moon, Mars or the asteroid Vesta, one of the largest in the main asteroid belt, located between the orbits of Mars and Jupiter. Three studies published in recent months now propel this number to… 90%!
The breakthrough, detailed in reviews Nature et Astronomy and Astrophysicsis the result of more than a decade of research by an international team. “We had to cross-reference several sources of information to digitally reconstruct the dynamics and history of collisions of large families of asteroids [qui génèrent des fragments] within the main belt,” explains Pierre Vernazza, astrophysicist at the Marseille Astrophysics Laboratory and co-author of these articles.
You should know that asteroids of the same family come from a larger parent body which has fragmented over time. These asteroids, as well as their debris, sometimes ending up in meteorites, therefore share similar characteristics, such as their composition, their orbital properties or their shock age, which makes it possible to outline their family tree. This careful work has made it possible to understand that young asteroid families produce more small residual fragments than previously thought. These are likely to collide with each other and thus drift out of the main belt towards the Earth. On the contrarythe fragments of old asteroid families have eroded so much that they have disappeared for millions of years and therefore no longer generate meteorites. Like bloodlines that have died out.
In fact, the research team determined that 70% of the meteorites we know today come from three families of asteroids: Karin, Coronis and Massalia. These were formed 5.8, 7.5 and around 40 million years ago respectively, so quite recently on a cosmological scale. The Massalia family alone provided 37% of all known meteorites; in the jargon, they are called ordinary L-type chondrites, for lowcorresponding to a low iron content.
“Meteorites are literally “pieces of the solar system” that reach Earth. They still contain traces of the conditions that prevailed at the time and place of their formation. And we can study these traces in the laboratory! argues Auriane Egal, scientific advisor to the Montreal Planetarium and specialist in the observation and modeling of meteor showers, who did not participate in this work. So we are interested in knowing precisely where a meteorite was formed, and what its path was before its collision with the Earth. »
Obtaining knowledge about certain asteroids thanks to their daughter meteorites highlights those lesser known. This will guide astronomers in choosing future asteroids to study. The research team has in fact noted that two asteroids recently sampled and studied in several laboratories, Bennu and Ryugu, share the same origins. “It’s a bit of a shame,” underlines the astrophysicist. Even if it means financing space missions, we might as well sample asteroids that do not come from the same family. » Even those of which we have no samples on Earth.
