Remnants of the Early Solar System Water Enriched in Heavy Oxygen Isotopes

Oxygen isotopic composition of our solar system is believed to have resulted from mixing of two isotopically distinct nebular reservoirs, ¹⁶O-rich and ¹⁷,¹⁸O-rich relative to Earth. The nature and composition of the ¹⁷,¹⁸O-rich reservoir are poorly constrained. We report an in situ discovery of a chemically and isotopically unique material distributed ubiquitously in fine-grained matrix of a primitive carbonaceous chondrite Acfer 094. This material formed by oxidation of Fe,Ni-metal and sulfides by water either in the solar nebula or on a planetesimal. Oxygen isotopic composition of this material indicates that the water was highly enriched in ¹⁷O and ¹⁸O (δ¹⁷,¹⁸OSMOW = +180[per thousand] per mil), providing the first evidence for an extremely ¹⁷,¹⁸O-rich reservoir in the early solar system.