Samples collected from asteroid Bennu by NASA are revealing surprising new details about how our Solar System formed approximately 4.5 billion years ago. A new chemical analysis challenges earlier theories about the asteroid's birthplace and suggests that Jupiter played an important role in shaping the materials from which Bennu and other ancient objects formed. Bennu completes one orbit around the Sun every 1.2 years and makes a relatively close approach to Earth about every six years, coming within roughly 300,000 kilometers (186,000 miles).
NASA's OSIRIS-REx mission traveled to the asteroid, collected material from its surface, and successfully delivered the samples to Earth in 2023. On September 23, 2023, a capsule carrying approximately 120 grams of asteroid material landed in the Utah desert. Scientists around the world subsequently received small portions of the precious cargo for detailed study.
Among them was Maria Schönbächler, Professor of Isotope Geochemistry at ETH Zurich, whose laboratory received half a gram of Bennu material. Her team immediately began examining the samples for clues about the asteroid's history. The research, now published in Science Advances, has uncovered a distinctive chemical signature that not only helps identify Bennu's origins but also provides new evidence about the processes that shaped the early Solar System.
Bennu's Chemical Fingerprint Reveals Its Cosmic Relatives To investigate Bennu's origins, the ETH Zurich researchers examined isotopes of three elements: iron, titanium, and chromium. Isotopes are different forms of the same chemical element that contain varying numbers of neutrons, giving them slightly different masses. 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, in some cases, when they formed. The analysis revealed that iron and titanium are distributed remarkably evenly throughout Bennu's material. It also uncovered a close chemical relationship between Bennu, the asteroid Ryugu, and a rare group of primitive meteorites known as CI meteorites.
CI meteorites are carbon-rich remnants of the early Solar System that have undergone relatively little alteration over billions of years. They are exceptionally uncommon among meteorites recovered on Earth. Bennu, Ryugu, and CI meteorites share strikingly similar isotopic fingerprints, suggesting that their original materials came from the same reservoir of ancient cosmic dust.
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