Samples reveal violent past of Asteroid Bennu

The samples from Asteroid Bennu collected by the OSIRIS-REx mission in 2020 and delivered to the Earth in 2023 contain a mixture of organic matter from interstellar space, stardust formed by the death of distant stars, and dust formed within the Solar System. The material provides evidence of past interactions with water and exposure to the harsh environment in space. Bennu is a fragment of a larger parent asteroid that was battered to bits, and occupied the main belt between Mars and Jupiter. This ancestor of Bennu was made up of diverse materials from across the Solar System and beyond. 

Despite the low chances, some of the material from the parent object escaped a number of chemical processes that were driven by heat and water, as well as the violent collision event that caused the fragmentation in the chaotic infancy of the Solar System. Some of the grains of dust in the samples are from before the formation of the Sun, 4.6 billion years ago. There are chemical similarities between the samples from Asteroid Bennu and the samples from Asteroid Ryugu retrieved by Japan's Hayabusa 2 mission, suggesting that both the asteroids may have formed in the outer reaches of the Early Solar System. 

While some of the material survived, most of the material was transformed by reactions with water. There is evidence to indicate that the minerals in the parent asteroid formed, dissolved, and then reformed over time. The parent asteroid accumulated both ice and dust, with the ice melting away, resulting in the reaction of liquid with dust that is preserved in the samples. There are also impact-melts on the material, indicating that the parent object of Bennu was bombarded by micrometeorites. This kind of detailed analysis is not possible using telescopes, and highlights the value of sample return missions.