Astronomers Have Discovered Where Most of the Asteroids and Meteorites in the Solar System Came From

This is an illustration of a large asteroid splintering. Don Davis

Most asteroids and meteorites originate from just a handful of minor ancient planets formed in the early years of the Solar System, according to a study published in the journal Nature Astronomy.

Researchers from the University of Florida found that at least 85 percent of 200,000 asteroids—which are responsible for most of the meteorites that strike Earth—came from the splintering, or breaking up, of perhaps five or six ancient minor planets that existed four billion years ago. It is also possible that the remaining 15 percent came from these bodies. However, at present, this remains unclear.

Asteroids are small rocky bodies that orbit the Sun, according to NASA. Meanwhile, meteorites are rocks that land on the Earth's surface, most of which are fragments of asteroids that broke up long ago.

The new findings broaden our understanding of how asteroids evolved and the materials they contain—knowledge that could be useful in deflecting large, potentially hazardous space rocks on course to strike Earth. That's according to Stanley Dermott, a theoretical astronomer from the University of Florida and lead author of the study.

"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," he said in a statement. "If ever one of these comes towards the earth, and we want to deflect it, we need to know what its nature is."

In their paper, the astronomers showed that the type of orbit an asteroid has depends on its size. In light of this, they concluded that the differences in meteorites found on Earth could only be explained by processes taking place in a handful of large precursor bodies, and not in lots of tiny objects, as previously thought.

"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," Dermott said.

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The study could have implications for determining where Earth-like planets may exist in the universe, according to Dermott, as well as shining a light on the materials that shaped our own planet.