Bennu asteroid samples point to a surprising origin involving Jupiter
The asteroid Bennu orbits the sun once every 1.2 years and approaches Earth every six years, passing within around 300,000 kilometers. NASA took advantage of this to collect material from the celestial body. In a spectacular operation in 2023, the US space agency collected samples from the surface of the asteroid Bennu by its OSIRIS-REx probe.
Asteroid Bennu, which orbits the sun every 1.2 years and approaches Earth every six years, was the focus of NASA's OSIRIS-REx mission. In 2023, the probe collected samples from Bennu's surface, with the container landing in Utah in September carrying around 120 grams of material. ETH Zurich professor Maria Schönbächler received a small portion for analysis, with results published in Science Advances confirming a surprising origin involving Jupiter.
The isotopic analysis of iron, titanium, and chromium reveals Bennu shares a unique fingerprint with the asteroid Ryugu and CI meteorites, indicating they formed from the same reservoir of cosmic dust. This suggests Bennu, Ryugu, and CI meteorites formed close to the water-ice line, where materials from the inner and outer solar system mixed.
The findings contradict previous assumptions that asteroids like Bennu formed in the outer regions and formed relatively late in the solar system's evolution. Jupiter's rapid growth and gravitational forces acted as a "bridge pillar" within the early solar system, blocking coarser material while allowing fine dust to mix in the transition zone near the water-ice boundary.
This scenario also explains Bennu's rich water content, as ice in the vicinity evaporated and condensed again in the region where Bennu formed. The analysis of Bennu's geochemistry provides insights into the solar system's formation and the conditions under which planets formed.
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