Analysis of material collected from asteroid Bennu by NASA’s OSIRIS-REx mission is providing new insights into Solar System formation during its earliest stages. The spacecraft retrieved approximately 120 grams of surface material that landed in Utah in 2023, with scientists worldwide receiving samples for detailed examination. Researchers at ETH Zurich analyzed isotopes of iron, titanium, and chromium in the Bennu material to establish its chemical fingerprint and determine its origins.
The research revealed that Bennu shares remarkably similar isotopic signatures with asteroid Ryugu and a rare class of primitive meteorites known as CI meteorites. This chemical kinship suggests that all three types of objects originated from the same reservoir of ancient cosmic material. Unlike previous theories proposing that primitive asteroids like Bennu formed in the outer Solar System, the new findings indicate the asteroid’s parent material accumulated near the water-ice line, a boundary region in the young Sun’s disk where temperatures were cold enough for water vapor to freeze. The analysis suggests that dust and particles from both inner and outer Solar System regions mixed at this location, creating a hybrid composition that neither fully resembles inner nor outer system materials.
Researchers propose that Jupiter played a significant role in facilitating this mixing process. The gas giant formed exceptionally rapidly, within approximately one million years of the Sun’s birth, and its growing gravitational influence reshaped material distribution throughout the disk. The massive planet may have acted as a barrier preventing larger particles from crossing its orbital zone while allowing fine dust to circulate and mix extensively. This mechanism could have brought material from different disk regions to converge near the water-ice boundary, where water ice enabled small particles to adhere and gradually accumulate into larger bodies.
The proposed formation scenario explains several of Bennu’s distinctive characteristics, including its abundance of water-bearing minerals and its chemical composition closely matching the Sun’s elemental mixture. Fine dust circulating throughout the disk could preserve a representative sample of Solar System ingredients from that early period, similar to how household dust settles across multiple surfaces rather than remaining localized. These findings contribute to understanding not only Bennu’s history but also the processes and conditions that shaped the materials from which all planets, including Earth, eventually formed.
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