BULLETIN

Asteroid Ryugu had distant beginnings

The first analysis of samples brought back to Earth from the asteroid Ryugu have now been completed, showing the space rock probably began its life much further out in the cold, dark reaches of the Solar System.

In 2019, the Japanese spacecraft Hayabusa2 took surface samples from Ryugu, returning them to Earth in 2020 to be examined by eager researchers around the world. These preliminary tests found the dust contained water laced with carbon dioxide. This could only happen if both substances were solid when the asteroid body formed, meaning its original orbit was three to four times the Earth–Sun distance; that’s twice as far out as it is now.

“The mineralogy of the Ryugu samples is similar to CI chondrites, a carbon-rich meteorite collected here on Earth,” says Deborah Domingue, from the Planetary Science Institute, who took part in the study. Meteorites are our most easily accessible samples of asteroid material here on Earth, but their source is often unknown. “Understanding the formation history of Ryugu has real implications for understanding the origin of these meteorites and where their parent bodies formed in our Solar System.” www.psi.edu/news/analysisruygusamples