NASA Bennu Samples Reveal Solar System Formation Secrets

Samples collected from asteroid Bennu by NASA are providing new insights into the formation of our Solar System approximately 4.5 billion years ago. Chemical analysis challenges previous theories regarding Bennu's birthplace and suggests a significant role for Jupiter in shaping the materials from which Bennu and other ancient objects formed. The OSIRIS-REx mission successfully delivered approximately 120 grams of asteroid material to Earth on September 23, 2023, landing in the Utah desert.

Maria Schönbächler, Professor of Isotope Geochemistry at ETH Zurich, whose laboratory received half a gram, led a team examining the samples. Their research, published in Science Advances, uncovered a distinctive chemical signature. This signature not only identifies Bennu's origins but also offers new evidence about early Solar System processes. Researchers examined isotopes of iron, titanium, and chromium, finding iron and titanium evenly distributed. A close chemical relationship was identified between Bennu, asteroid Ryugu, and rare CI meteorites, suggesting their original materials came from the same ancient cosmic dust reservoir.

The findings challenge the long-held belief that primitive asteroids like Bennu originated in the outer Solar System and formed relatively late. Instead, researchers propose that Bennu's material accumulated near the water-ice line, a boundary in the disk around the young Sun where water vapor froze. This region may have been a crucial mixing point for dust originating from both the inner and outer Solar System, with water ice aiding the accumulation of small particles into larger bodies. Schönbächler noted, "Bennu is a hybrid: the material does not clearly match either the inner or the outer Solar System."

The scenario developed by researchers suggests Jupiter played a key role. Forming within one million years of the Sun's birth, Jupiter's immense gravitational influence reshaped material distribution in the disk. It is proposed that Jupiter acted as a structural barrier, preventing most larger particles from crossing its orbit while allowing finer dust to mix extensively near the water-ice line. This process could explain Bennu's abundance of water-bearing material and its chemical resemblance to the Sun. Jupiter may thus have influenced where these ancient asteroids formed and their constituent ingredients.

What to watch: Further analysis of Bennu samples for more insights into early Solar System conditions.

Editor's note: Comprehensive coverage of the scientific findings and the role of Jupiter in the formation of Bennu, effectively utilizing the provided source text.