Two new studies report that most of Earth’s meteorites can be linked to a few collisions within the asteroid belt between Mars and Jupiter, with a particularly cataclysmic impact event occurring around 470 million years ago. This discovery provides researchers with vital context, allowing them to better understand how the building blocks of planets came together to create the solar system as it is today. However, it also suggests that there may be an extremely biased meteorite collection that only tells a small part of the story.
Meteorites record the history of the solar system’s formative years, but their origins are often unknown. Knowing the asteroid that a sample came from is essential for scientists studying meteorites, as it provides valuable information about the history of the rock. Most of the meteorites on Earth are ordinary chondrites, with two classes, H and L, making up 70% of all meteorite falls. It is believed that the L chondrites originated from a single parent asteroid that was involved in a supersonic collision.
Researchers used radioactively decaying elements to determine that the L chondrites emerged from a collision that occurred 470 million years ago. By scanning prominent stony-type asteroids in the asteroid belt, scientists were able to identify the Massalia family as the likely source of the L chondrites. Independent lines of data, including the orbits of near-Earth asteroids and L chondrite meteors, also point to the Massalia family as the origin of this meteorite class. The impact that created the L chondrites also led to more recent bombardments, sending streams of material back onto the largest asteroid remnant.
H chondrites, on the other hand, originated from a different impact event or events, with many being 5-8 million years old. By reconstructing the past orbits of the mineralogically matching Koronis2 and Karin asteroid families, researchers were able to trace the source of this meteorite class. The study’s findings suggest that Earth’s meteorite collection could be biased towards just a few asteroids within the asteroid belt, limiting our understanding of the solar system’s history. To overcome this bias, researchers suggest that space missions be conducted to explore and collect samples directly from asteroids in order to expand our knowledge.
Overall, while the discovery that most of Earth’s meteorites can be linked to a few collisions within the asteroid belt provides valuable context for understanding the solar system’s formation, it also highlights the limitations of our current meteorite collection. By identifying the origins of different meteorite classes and tracing them back to specific asteroid families, researchers can gain valuable insights into the history of the solar system. Moving forward, exploring and collecting samples directly from asteroids through space missions may be key to expanding our understanding of the solar system’s early years.
