Fig. 1.

The evolution of FeO concentration in the magma ocean, over the course of accretion, for 14 redox models. The final FeO content is fixed at the present-day value for the primitive upper mantle, 5.9% FeO (all fractions in mol%). Path 5 is the constant redox path, where FeO concentration is maintained at 5.9% throughout accretion. Paths 1–4 start more reduced than the present-day mantle, and the magma ocean oxidizes throughout accretion. Paths 6–14 all start more oxidized than the present-day mantle, and the magma ocean becomes more reduced over the course of accretion. Some paths have initial FeO concentrations similar to the silicate fractions of common meteorite groups: paths 1 and 2 are similar to that of EH chondrites, but path 1 has a constant low fO₂ until 28% accretion as proposed in ref. 15; path 9 is similar to that of H chondrites; path 10 is similar to that of HED meteorites; paths 11 through 14 are similar to that of L, LL, CV, and CI chondrites, respectively. The paths span four orders of magnitude in initial fO₂ ranging from IW-4.5 (paths 1 and 2) to IW-0.6 (path 14), so as to cover the entire plausible range of redox conditions found in Earth’s accretionary building blocks.