By Ian Randall
Deputy Science Editor
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Astronomers have revealed new sources of meteorites within the solar system's asteroid belt, helping us understand where potentially hazardous asteroids might also originate.
The researchers tracked the source of 75 meteorite fireballs captured on film around the globe by scientific all-sky cameras, doorbell cameras, and dashboard cameras.
"That proves to be enough to start seeing some patterns in the direction from which the meteorites approach Earth," said paper author and astronomer Peter Jenniskens of the SETI Institute and the NASA Ames Research Center in a statement.
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"This has been a decade-long detective story, with each recorded meteorite fall providing a new clue. We now have the first outlines of a geologic map of the asteroid belt."
Knowing where meteorites come from before hitting Earth can also reveal where potentially hazardous Near Earth Asteroids may originate.
"Near Earth Asteroids do not arrive on the same orbits as meteorites, because it takes longer for these to evolve to Earth," Jenniskens explained.
"But they do come from some of the same asteroid families."
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Most meteorites that impact the Earth come from the asteroid belt—the region between Mars and Jupiter's orbits, where over a million space rocks, each more than 0.6 miles wide, circle the sun.
The asteroid belt is believed to have formed from a group of planet precursors whose accretion was disrupted by Jupiter's gravity, causing them to collide and shatter instead.
Jupiter's influence can still cause rocks to fly out of the belt, sometimes heading into the inner solar system and passing near Earth.
Collisions between large asteroids in the belt can create debris fields with shared origins and physical and orbital properties—known to scientists as "clusters."
Where Do Iron-Rich Meteorites Come From?
"We now see that 12 of the iron-rich ordinary chondrite meteorites (H chondrites) originated from a debris field called 'Koronis,' which is located low in the pristine main belt," said Jenniskens.
"These meteorites arrived from low-inclined orbits with orbital periods consistent with this debris field."
Measuring the level of radioactive elements created in individual meteorite samples by exposure to cosmic rays allowed the team to estimate how long ago the rocks broke out of their parent asteroid and match these to the corresponding "dynamical age" of debris fields calculated from measuring the spread of the fields.
"By measuring the cosmic ray exposure age of meteorites, we can determine that three of these twelve meteorites originated from the Karin cluster in Koronis...and two came from the Koronis2 cluster," Jenniskens said.
He explained that the former was created some 5.8 million years ago, while the latter emerged 10-15 million years ago.
"One other meteorite may well measure the age of the Koronis3 cluster: about 83 million years."
In a similar fashion, the researchers were able to connect another group of H chondrites arriving on steep orbits to the 6-million-year-old Nele asteroid family in the central main belt and a third group to the inner main belt from the breakup of an asteroid, 20 Massalia, that occurred some 35 million years ago.
Where Do Low-Iron Meteorites Come From?
Meteorites with very low and very low iron contents (so-called L and LL chondrites), meanwhile, were found to come primarily from the inner main belt, as previously speculated.
"We propose that the L chondrites originated from the Hertha asteroid family, located just above the Massalia family," said Jenniskens.
He added: "Asteroid Hertha doesn't look anything like its debris. Hertha is covered by dark rocks that were shock-blackened, indicative of an unusually violent collision.
"The L chondrites experienced a very violent origin 468 million years ago when these meteorites showered Earth in such numbers that they can be found in the geological record."
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Looking forward, studying more meteorite samples in the future will help the team refine their geologic map.
"We are proud about how far we have come, but there is a long way to go," said Jenniskens.
"Like the first cartographers who traced the outline of Australia, our map reveals a continent of discoveries still ahead when more meteorite falls are recorded."
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Reference
Jenniskens, P., & Devillepoix, H. A. R. (2025). Review of asteroid, meteor, and meteorite-type links. Meteoritics & Planetary Science. https://doi.org/10.1111/maps.14321
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