NASA Bennu Asteroid Samples Reveal Jupiter Shaped Early Solar System
Chemical Analysis of Asteroid Bennu Samples
The Tech TL;DR:
Half a gram of asteroid dust just helped rewrite our origin story.Scientists at ETH Zurich studied the sample NASA brought home from asteroid Bennu. It points to a birthplace near the solar system's ice line, where young Jupiter blocked coarse rock, fine dust from both sides… pic.twitter.com/N2xL0Voowl
- NASA’s OSIRIS-REx mission delivered roughly 120 grams of Bennu material to the Utah desert on September 23, 2023.
- Isotope analysis of iron, titanium, and chromium conducted by ETH Zurich researchers reveals a chemical fingerprint closely matching asteroid Ryugu and rare CI meteorites.
- The findings propose that Bennu formed near the water-ice line in the early Solar System, with Jupiter acting as a gravitational barrier that facilitated the mixing of inner and outer disk materials.
Isotopic Fingerprints of Iron, Titanium, and Chromium
To investigate Bennu’s origins, researchers at ETH Zurich examined isotopes of three elements: iron, titanium, and chromium. By measuring the relative amounts of these isotopes, scientists can identify a material’s chemical fingerprint. These patterns provide clues about where an asteroid’s ingredients originated and when they formed.
The analysis revealed that iron and titanium are distributed remarkably evenly throughout Bennu’s material.
Bennu Material Accumulated Near the Water-Ice Line
The new findings published in Science Advances challenge both assumptions.
Around 4.5 billion years ago, it served as a meeting place for material traveling from different parts of the developing Solar System. Dust originating in both inner and outer regions mixed near this boundary, and water ice helped the smallest particles stick together into larger bodies.
Bennu is a hybrid, as its material does not clearly match either the inner or outer Solar System, according to Maria Schönbächler, Professor of Isotope Geochemistry at ETH Zurich, whose laboratory received half a gram of Bennu material for study. Its unusual chemical composition suggests it formed from a combination of materials originating in both regions rather than from a single, isolated source.
Jupiter Reshaped the Distribution of Disk Material
Researchers also developed a scenario explaining how this mixing occurred, with Jupiter emerging as a key player.
The proposed formation scenario also explains Bennu’s abundance of water-bearing material and its chemical resemblance to the Sun. Near the water-ice boundary, ice could evaporate as temperatures changed, releasing water vapor that condensed again in cooler regions to concentrate water in the material. Meanwhile, Jupiter’s influence limited the movement of larger particles, leaving the asteroid’s parent material dominated by fine dust that circulated efficiently and preserved a chemical composition closely resembling the overall elemental mixture found in the Sun.
Future Sample-Return Missions to Mars and Phobos
Despite these discoveries, several questions remain unanswered regarding whether other asteroids share the same isotopic signature as Bennu and Ryugu, and how precisely Jupiter influenced the movement of dust. Additional asteroid samples could help scientists test the proposed formation scenario.
Schönbächler plans to apply to JAXA for access to those future samples to determine how different regions of the early Solar System exchanged material to produce the planets, moons, and asteroids observed today.