Where do meteorites of different types come from?

For centuries, scientists have sought to understand the origins of meteorites that fall to Earth. Recent research has provided a clearer picture, linking these space rocks to specific regions within the asteroid belt.

With 75 meteorite falls now traced to their original orbits, a new map of the asteroid belt is emerging, offering valuable insights into planetary defense and asteroid evolution.

Meteorites typically originate from meteoroids and asteroids measuring between 0.1 to 1 meter in diameter. These fragments were once part of larger asteroids that collided and broke apart in space. Past estimates suggested that meteorites sampled up to 148 parent bodies, but those with known approach orbits appear to originate from only about 15 distinct sources.

Larger near-Earth asteroids (NEAs), ranging from 20 meters to 35 kilometers in size, are also traced back to the asteroid belt through spectroscopic classification. By comparing the reflection spectra of meteorites and asteroids, researchers identify their parent bodies. Additionally, dynamical models reveal how asteroid fragments evolve over time, eventually reaching Earth.

"This has been a decade-long detective story, with each recorded meteorite fall providing a new clue," said Peter Jenniskens, a meteor astronomer at the SETI Institute and NASA Ames Research Center. "We now have the first outlines of a geologic map of the asteroid belt."

Most meteorites originate from asteroid families—groups of space rocks created by large collisions. When an asteroid is struck, the fragments disperse based on the impact's conditions and the target asteroid's properties. Some of these fragments eventually enter Earth's orbit.

One of the strongest connections is between H-chondrite meteorites and the Koronis asteroid family in the pristine main belt. Jenniskens and his team found that 12 H chondrites, which are rich in iron, likely originated from this region. Three of them were traced to the Karin cluster, a subgroup within the Koronis family that formed 5.8 million years ago. Two others appear linked to the Koronis2 cluster, which is 10 to 15 million years old.

Other meteorite types follow similar patterns. L and LL chondrites, which contain lower iron content, seem to come from the inner main belt. Scientists have long suspected a link between LL chondrites and the Flora asteroid family, and recent data confirms this connection. The L chondrites are now proposed to originate from the Hertha asteroid family, which was likely altered by a violent impact 468 million years ago.

"Asteroid Hertha doesn’t look like its debris," said Jenniskens. "Its surface is covered by dark, shock-blackened rocks, a sign of an unusually intense collision."

Once asteroid fragments are released, their orbits evolve due to forces like the Yarkovsky effect, which results from uneven heat absorption and radiation. Small objects drift toward gravitational resonances—areas where Jupiter’s gravity alters asteroid orbits—until they are propelled toward Earth.

The efficiency of these resonances varies. The ν6 resonance, located near the inner edge of the asteroid belt, is responsible for about 1% of meteorite deliveries to Earth. The 3:1 resonance with Jupiter, located at 2.50 AU, is less efficient, contributing only 0.03%. Further out, the 5:2 resonance near 2.82 AU has an even lower efficiency of 0.003%.

Once in Earth's orbit, meteorites can be influenced by further interactions. "Near-Earth asteroids do not arrive on the same orbits as meteorites because their journey to Earth takes longer," explained Jenniskens. "But they do come from some of the same asteroid families."

Collisions also play a role. The exposure age of meteorites—determined by measuring cosmic-ray exposure—suggests that some meteorites were buried within asteroids for millions of years before being ejected. Iron meteorites, for instance, have some of the longest exposure ages, up to 1.5 billion years.

By contrast, carbonaceous chondrites tend to survive only briefly at close distances to the Sun, often lasting less than 500,000 years before breaking apart.

The effort to trace meteorite origins gained momentum in the last decade with the development of all-sky camera networks. Jenniskens and astronomer Hadrien Devillepoix of Curtin University led the expansion of a network in California and Nevada, capturing fireballs as they entered Earth's atmosphere. This effort, combined with global collaborations such as the Global Fireball Observatory, has tracked the orbits of 17 meteorite falls.

Advancements in technology have further improved detection. Doorbell and dashboard cameras have contributed to tracking fireballs worldwide. In some cases, asteroids were observed in space before their fragments fell to Earth. This was the case for four recovered meteorites: 2008 TC3, 2018 LA, 2023 CX1, and 2024 BX1—the last of which resulted in the January 2024 fall of the aubrite Ribbeck in Germany.

"Altogether, this quest has yielded 75 laboratory-classified meteorites with impact orbits tracked by cameras," said Jenniskens. "That proves to be enough to start seeing patterns in the directions from which meteorites approach Earth."

Looking ahead, the next phase of research involves detecting more asteroids before impact. New astronomical observatories will soon come online, allowing scientists to observe space rocks in real-time before they enter Earth's atmosphere. By refining these observations, researchers aim to build a more complete map of the asteroid belt’s influence on our planet.

"Like the first cartographers who traced the outline of Australia, our map reveals a continent of discoveries still ahead," said Jenniskens. "We are proud of how far we have come, but there is still a long way to go."

Research findings are published in the journal Meteoritics & Planetary Science.

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