Ryugu samples include water from the early outer solar system

Sep. 26 () –

The first analysis of samples from the asteroid Ryugu include water with CO2 in a crystal of nickel iron sulfide, indicating that the main body formed in the outer Solar System.

A study published in Science offers the results of examining 17 individual grains brought to Earth by the Japanese spacecraft Hayabusa 2.

The mission sampled the surface twice: one on February 21, 2019 and again on July 11, 2019. The first sampled the intact surface, the second sampled the regolith excavated by the artificial impact created earlier during the mission.

This study examined grains from both sample sites, providing samples that can actually provide insight into the evolution of Ryugu. Also, the finest grained powder samples less than 1 millimeter in size from both sample collection chambers were examined using reflectance spectroscopy techniques.

“The goal of these initial studies is to understand and characterize the formation history of Ryugu. While the orbital data identified the presence of phyllosilicates, it was the analysis of the samples that gave us insight into the detailed mineral composition and physical properties of Ryugu.” regolith grains,” said it’s a statement Deborah Domingue, scientist at the PSI (Planetary Science Institute) and author of the study.

The article argues that numerical simulations based on these results show that Ryugu’s parent body formed approximately 2 million years after the birth of our Solar System, in the outer Solar System.

The mineralogy and petrology of the samples indicate that the original body formed in the region of the early Solar System where water and carbon dioxide existed as solids, more than 3 or 4 times the distance between the Sun and Earth, possibly even beyond the orbit of Jupiter.

This was followed by an inward scattering of the main asteroid belt, to the current orbital position of the Polana and Eulalia families of asteroids, which are about 2.5 times the distance between the Sun and Earth. The Polana and Eulalia asteroid families are the possible parent families of Ryugu based on orbital dynamic calculations of the origin of Ryugu.

Ryugu’s main body was broken up by a large-scale impact that formed the Eulalia or Polana families of asteroids, including Ryugu, which then migrated into its current orbit. Using the measured physical properties of the samples, models of the collision show that Ryugu formed from materials far from the impact site.

The lack of shock features in the mineralogy and the temperature consistent with interlayer water found in the Ryugu saponite (a clay mineral) are consistent with the formation of Ryugu from fragments excavated in areas remote from the site. of the impact. The composition of Ryugu, mineralogical and chemical, indicates that Ryugu was formed from fragments from multiple depths within his main body.