Ancient Rock Traces Found in Ryugu Samples Predate Sun's Existence

Samples from asteroid Ryugu contain clasts of rock with a chemical composition different from the rest of the asteroid, indicating they were acquired through a later impact. These clasts contain tiny grains of rock made from stars that died before the Sun existed, suggesting they originated in the outer reaches of the Solar System. The majority of these presolar grains came from asymptotic giant branch (AGB) stars, while one grain showed signs of a possible supernova origin. The impact that brought these grains to Ryugu or its parent body likely occurred after the loss of water, and some of the presolar grains may have originally come from a comet. This discovery provides insights into the early history of the Solar System.