Petrography of Ryugu particles. (Top left) Largest allocated Ryugu particle (A0002); (bottom left) synchrotron X-ray based CT image of A0002 obtained at the SPring-8 facility; (middle) False-color X-ray elemental image. Mineral assemblages formed in the presence of water, red: phyllosilicates, green: carbonates, blue: magnetite, yellow: sulfides; (right) High resolution back-scattered electron image. Area enlarged from the white box in the middle panel. Image: Modified from Ito et al. (2022)


The Phase-2 curation Kochi Team, led by Motoo Ito of the Extra-cutting-edge Science and Technology Avant-garde Research (X-star), Kochi Institute for Core Sample Research, JAMSTEC, began analysis of Ryugu particles on June 20, 2021. The results of the first-year analytical campaign, based on systematic investigations conducted at institutes and universities across Japan, the USA, and the UK, has been published in Nature Astronomy on August 15, 2022 (August 16, JST).

Title:A pristine record of outer Solar System materials from asteroid Ryugu's returned sample
Journal:Nature Astronomy

Key points

  1. The mineralogy of the Ryugu particles indicate that they underwent extensive aqueous alteration.
  2. The deuterium-rich and 15N-rich isotopic compositions of fine-grained minerals and organics suggest that the constituents of the Ryugu particles formed in the outer Solar System.
  3. Aliphatic carbon-rich organics associated with coarse-grained phyllosilicates were found. Such an association has not been observed in any meteorite study and could be unique to the asteroid Ryugu.
  4. The results suggest that coarse-grained phyllosilicates may have served as "cradles" for organics and water, which may subsequently have been transported to the early Earth.

For details, please see the JAXA press release.