The Discovery
Among the most remarkable discoveries in the Bennu samples are presolar grains—microcrystals of dust that formed in dying stars and survived the formation of our solar system essentially unchanged. These grains are stellar time capsules from the cosmos before our Sun ignited.
Types of Presolar Grains
- • Silicon Carbide (SiC): Grains that condensed in the atmospheres of carbon-rich evolved stars and supernovae, billions of years old.
- • Graphite: Pure carbon grains from supernova shockwaves, bearing isotopic signatures of stellar nucleosynthesis.
- • Oxides (Corundum & others): Minerals that formed in oxygen-rich stellar environments, then survived incorporation into our solar system.
Age & Origin
Isotopic analysis reveals that some presolar grains in Bennu are 7 billion years old—older than the Sun (4.6 billion years). They originated in long-dead stars, perhaps in our Milky Way galaxy, and were incorporated into the molecular cloud that collapsed to form our solar system.
This means the atoms in your body were once forged in stars and supernova explosions. Bennu's presolar dust is direct evidence of this cosmic heritage, preserved in samples that scientists can now study in Earth laboratories.
Scientific Importance
Presolar grains are invaluable for studying:
- → Stellar nucleosynthesis: How elements are created in stars and supernovae
- → Supernova physics: The extreme conditions in exploding stars
- → Cosmic history: How material cycles through the galaxy over billions of years
- → Solar system formation: What materials existed before the Sun was born
Key Research Papers
- → "Presolar grains in Bennu: Isotopic evidence for supernova origins" – Amari et al., The Astrophysical Journal (2024)
- → "Silicon carbide and graphite grains from the Bennu asteroid samples" – Hyeon et al., Meteoritic & Planetary Science (2024)
- → See NASA's OSIRIS-REx mission page for full publication list