Investing Space Weathering on Ryugu by Laboratory Comparative Analysis

The Hayabusa2 mission (JAXA) investigated the NEA Ryugu from June 2018 to November 2019. On 6 December 2020, 5g of samples from the C-type asteroid 162173 Ryugu were returned to Earth. Samples have sizes ranging from ~8 mm, the largest average diameter, down to fine submillimeter dusts. For one year, the Initial Analysis Team, has lead a detailed characterization of some selected grains. These samples show various and different lithologies, with the most common mineralogy containing Mg-rich phyllosilicates, MgCa and MgFe carbonates, hydroxyapatite, Fe sulphides and Fe oxides. Rare fragments also contain islands of anhydrous silicates such as olivine and pyroxene, amorphous silicates, Ca carbonate, phosphide, Fe-Ni oxides and poorly crystalline phyllosilicate. Overall, the major lithology is consistent with a CI chondrite unaltered by terrestrial weathering processes.