The asteroid Bennu is a hybrid world that formed near the solar system’s “water-ice line”, where fire met ice in the early solar system, scientists said in a study published this month.

Researchers at ETH Zurich, led by Maria Schönbächler, analysed samples returned by NASA’s OSIRIS-REx mission — 120 grams of rock collected in 2020 and delivered to Earth in September 2023. Isotopes of iron, titanium and chromium show Bennu mixes material from both the inner and outer solar system.

The findings suggest Bennu’s parent body formed exactly where water could freeze into ice but rock remained hot — a boundary that shaped how planets, and possibly life’s ingredients, were distributed across the young solar system.

Bennu’s composition closely matches Japan’s Ryugu samples and a rare class of meteorites called CI chondrites, reinforcing the idea that carbon-rich asteroids seeded the early Earth with water and organic molecules. The mission itself was a landmark: OSIRIS-REx touched down on Bennu in 2020, grabbed its sample, and returned the capsule to Earth in September 2023. Scientists say the pristine material will be studied for decades, with each new instrument revealing more about the solar system’s earliest days.