Isochrons reveal Bennu's hybrid origin in solar system's transition zone

New analysis of samples returned by NASA's OSIRIS-REx mission suggests that the asteroid Bennu is not a primitive body from the outer solar system, as previously believed. Instead, scientists propose that Bennu is a hybrid, formed from materials originating from both the inner and outer reaches of our solar system. This revised understanding challenges existing models of asteroid formation. Hybrid Origins Revealed by Isotopic Analysis The capsule carrying Bennu's samples landed in Utah's West Desert in September 2023, containing approximately 120 grams of rock. A portion of this material, about half a gram, was analyzed by a team led by Maria Schönbächler at ETH Zurich. Her team focused on the isotopes of iron, titanium, and chromium, whose relative abundances serve as a unique fingerprint of a celestial body's origin. The measurements yielded definitive results: titanium and iron are uniformly distributed throughout Bennu. Its isotopic profile aligns with that of the asteroid Ryugu and CI-class meteorites, indicating that all three originated from the same primordial cosmic dust cloud. However, their chemical composition significantly differs from other known asteroids, meteorite groups, and planets.