About 466 million years ago, Earth experienced a dramatic influx of space rocks, a bombardment likely triggered by the fragmentation of a large asteroid within the Mars-Jupiter orbital region. New research suggests the Massalia asteroid family, a group sharing similar orbits, may be the primary source of this ancient barrage. Astonishingly, this family, along with two others, accounts for almost 40% of all meteorites found on Earth.
Thousands of meteorites, having endured tumultuous journeys through space, have landed on Earth. Groundbreaking research, detailed in three studies published in Nature and Astronomy and Astrophysics, has traced the origin of a significant portion of these celestial remnants. The findings point to three relatively young asteroid families as the source of over 70% of Earth’s meteorites, potentially unlocking secrets of the early solar system.
These families, named Karin, Koronis, and Massalia, originated from collisions in the main asteroid belt approximately 5.8 million, 7.5 million, and 40 million years ago, respectively. While these timeframes seem vast, they represent relatively recent events within the context of our 4.5-billion-year-old solar system.
“The most recent collisional events in the asteroid belt overwhelmingly dominate the influx of material reaching our planet,” Michaël Marsset, a research fellow at the European Southern Observatory and lead author of one of the studies, explained to MaagX. “Contrary to expectations, the meteorite flux isn’t a uniform blend of all asteroid belt compositions. It’s dominated by debris from three recently fragmented asteroids.” This “flux” refers to the constant stream of meteors traveling from space to Earth.
Marsset aimed to resolve the discrepancy between the composition of meteorites found on Earth and those observed in the asteroid belt. Previously, scientists could only pinpoint the origins of about 6% of meteorites, predominantly from the Moon, Mars, and the large asteroid Vesta. The provenance of the remaining meteorites remained a mystery.
By combining a telescopic survey of the composition of major asteroid families in the main belt with sophisticated computer simulations of their collisional and dynamical evolution, researchers identified the primary source of most other meteorites. Analyzing the chemical composition of these meteorites, they traced them back to their parent bodies within these asteroid families.
“Major asteroid collisions are infrequent, occurring perhaps every 30 to 50 million years. Notably, three such collisions occurred within the last 8 million years,” Pierre Vernazza, a researcher at the French National Center for Scientific Research and another lead author, told MaagX.
The dominance of these young asteroid families in the meteorite flux might be attributed to the abundance of smaller fragments resulting from the initial collisions. These fragments are more susceptible to further collisions, increasing the likelihood of some debris being propelled towards Earth. “The collisional cascade within these families remains active, contributing to their dominant role in meteorite production,” Marsset stated.
Meteorites provide invaluable clues to the solar system’s enigmatic past. Studying them offers a unique window into the early evolution of Earth and its neighboring planets.
“Meteorites retain a wealth of information about our early protoplanetary disk,” Marsset explained. “By linking these meticulously studied meteorites to specific asteroid families, we can reconstruct the original compositional and thermal gradients of this disk. This is the ultimate goal of our research.”
Beyond tracing their origins, close examination of meteorites can illuminate the chaotic beginnings of our solar system, revealing events that transpired millions of years before our arrival.
