An international team of scientists from France, Germany, and the Czech Republic discovered last October that the majority of Earth’s meteorites originate from just three asteroid families in the main asteroid belt. This finding has solved a decades-old mystery about the origins of meteorites.
The groundbreaking findings, published in Nature and Astronomy & Astrophysics, revealed that 70% of meteorites originate from three asteroid families: Karin, Koronis, and Massalia. The youngest of these families, Karin, was created 5.8 million years ago and consists of 90 asteroids. Koronis, which dates back 7.5 million years, includes 5,940 members, such as the asteroid Ida and its moon Dactyl (see image), famously photographed by NASA’s Galileo spacecraft. Massalia, the oldest family at 40 million years, contains over 6,000 asteroids and accounts for 37% of meteorite impacts on Earth. Out of approximately 70,000 known meteorites, only 6% of origins were definitively traced to the Moon, Mars, and Vesta, a large asteroid in the main belt between Mars and Jupiter. The remaining 94% of impacts remained a mystery, until last October.
To uncover the truth, the team conducted telescopic surveys to analyse asteroid compositions and used advanced computer modelling to trace the collisional and dynamical evolution of asteroid families. An asteroid family is a group of fragments believed to have resulted from a single catastrophic collision. Asteroids typically have similar orbital patterns, meaning the likelihood of collision is high. Additionally, Research by Paolo Farinella, University of Pisa, determined that “family asteroids undergo collisions with other members of the same family two to three times more frequently than with non-family” asteroids.
The research team led by Dr. Miroslav Brož, an astrophysicist from Charles University in Prague, also discovered that younger asteroid families retain a greater number of fragments. This increases the chances of debris escaping the main asteroid belt and traveling toward Earth. Over time, however, older families lose their fragments, making them less significant sources of meteorites.
These discoveries shed light on the asteroid belt’s role as the birthplace of many of Earth’s meteorites. Meteorites that travel to Earth are fragments of these catastrophic events, serving as time capsules that provide critical insights into the solar system’s history.
The discoveries have enabled scientists to pinpoint the origins of kilometre-sized asteroids, known to pose significant threats to life on Earth. This discovery strengthens NASA’s focus on tracking near-Earth objects (NEOs) like asteroid Bennu and Ryugu, another asteroid with a high probability of impacting Earth in the distant future. Missions such as NASA’s OSIRIS-REx and JAXA’s Hayabusa 2 will further study these space rocks, aiming to prevent catastrophic collisions.
By tracing meteorite origins, scientists can prioritize targets for research and improve models for planetary defence. Having identified the origins of 90% of meteorites, scientists are now turning their attention to younger asteroid families, formed within the past 50 million years, to trace the sources of the remaining 10%. This ongoing research promises to uncover more about the processes driving recent asteroid collisions and their influence on Earth’s meteorite population.
Ida and Dactyl, as photographed by the Galileo Space probe, 28 August, 1993 (Source: NASA Science)