Asteroid Bennu holds stardust older than the Sun, hinting at clues to our Solar System's birth

The story of our solar system is written in dust, and scientists say a small asteroid has preserved it for billions of years. Tiny grains collected from asteroid Bennu are now offering rare clues about the birth of stars and planets, long before the sun itself existed.

What did scientists find in Bennu’s samples?
NASA’s OSIRIS-REx spacecraft collected Bennu’s samples in 2020 during a swift touch-and-go. The material contains ancient stardust, interstellar organic matter, and minerals formed from melted ice inside Bennu’s parent body. Researchers say around 80% of the asteroid is made up of minerals created when dust reacted with water. These grains hold chemical signatures of dead stars and represent important records of cosmic history.

A scanning electron microscope shows a micrometeorite crater on a Bennu particle. Three new studies reveal the asteroid’s samples hold diverse materials, including some older than the sun. (Image: NASA/Zia Rahman)

How old is the dust inside Bennu?
The findings, published in Nature Astronomy and Nature Geoscience, confirm some grains are older than the sun. Scientists call them presolar grains, many smaller than a micrometre and traceable only through unusual chemical fingerprints. Pierre Haenecour of the University of Arizona, who analysed the samples, described Bennu as a “time capsule” holding remnants from the solar system’s earliest days. Some grains even survived the catastrophic collision that destroyed Bennu’s parent asteroid millions of years ago.