Inner Main-Belt Asteroids Are Remnants of Few Ancient Minor Planets, Study Shows


According to new research, at least 85% of 200,000 asteroids in the inner asteroid belt — the main source of Earth’s meteorites — originate from five or six large primordial planetesimals; the other 15% may also trace their origins to the same group of ancient bodies.

This artist’s concept shows a young planetary system. Image credit: NASA / JPL-Caltech.

This artist’s concept shows a young planetary system. Image credit: NASA / JPL-Caltech.

The findings, published in the journal Nature Astronomy, provide a more robust understanding of the evolutionary history of asteroids and the materials that form them — information could prove essential to protecting the Earth and ourselves from massive meteorites.

“These large bodies whiz by the Earth, so of course we’re very concerned about how many of these there are and what types of material are in them,” said lead author Professor Stanley Dermott, from the University of Florida.

“If ever one of these comes towards the Earth, and we want to deflect it, we need to know what its nature is.”

Professor Dermott and his colleagues from Armagh Observatory and Planetarium, the National Optical Astronomy Observatory, Florida Space Institute, and the University of Florida demonstrated that the type of orbit an asteroid has depends on the size of the asteroid.

This finding suggests that differences in meteorites found on Earth appear because of the evolutionary changes that occurred inside a few large, precursor bodies that existed more than 4 billion years ago.

“I wouldn’t be surprised if we eventually trace the origins of all asteroids in the main asteroid belt, not just those in the inner belt, to a small number of known parent bodies,” Professor Dermott said.

“Building knowledge of the evolutionary history of bodies that formed our early Solar System helps theoretical astronomers answer questions related to where planets like our own might exist in the Universe.”

“But, first, we have to understand the processes that produced the planet we live on.”


Stanley F. Dermott et al. The common origin of family and non-family asteroids. Nature Astronomy, published online July 2, 2018; doi: 10.1038/s41550-018-0482-4