Enrichment of moderately volatile elements in first-generation planetesimals of the inner Solar System.

The depletion of moderately volatile elements (MVEs) in terrestrial planets remains poorly understood, with explanations including partial nebular condensation and MVE loss during planetesimal differentiation or collisions. In this study, we use magmatic iron meteorites to reconstruct the MVE inventory of the earliest inner [noncarbonaceous (NC)] and outer [carbonaceous (CC)] Solar System planetesimals. We show that several NC and CC iron meteorite parent bodies (IMPBs) exhibit chondrite-like MVE abundances, indicating that "first-generation" inner Solar System planetesimals were remarkably MVE rich. Consistent with isotopic signatures of MVEs in Earth and Mars, these planetesimals made a substantial contribution to the MVE inventories of terrestrial planets. Variations in MVE abundances among IMPBs, particularly the two volatile-depleted NC and CC IMPBs (IVA and IVB), reflect secondary volatile loss after disruption of their parent bodies. Consequently, MVE depletion in terrestrial planets is more closely linked to the protracted history of MVE loss during planetesimal collisions rather than incomplete condensation or MVE loss during planetesimal differentiation.