Incorporation of 16O-rich anhydrous silicates in the protolith of highly hydrated asteroid Ryugu

The abundant phyllosilicate and carbonate minerals characterizing most of the returned particles from asteroid Ryugu suggest a history extensive aqueous alteration on its parent body, similar to rare mineralogically altered, but chemically primitive, CI (Ivuna-type) chondrite meteorites. Particle C0009 differs other examined so far by containing anhydrous silicates at level ~0.5 vol%, thus can help shed light unaltered original materials that constituted Ryugu’s protolith. In situ oxygen isotope measurements Mg-rich olivine pyroxene in reveal two populations ?17O: ?25‰ ?15‰ ?8‰ ?3‰. former latter correlate well with silicate morphologies those seen amoeboid aggregates chondrule phenocrysts, respectively, both which are less aqueously altered carbonaceous chondrites. This result also highlights presence ?17O close solar value either or an CI-chondrite characteristics, provides strong evidence chondrules accreted into Our data raise possibility protoliths chondrites incorporated silicates. About 0.5% volume particle is made up silicates, mostly olivines, despite body. Such aggregates, rich 16O, were present protolith survived fluid activity.