Zinc isotope anomalies in primitive meteorites identify the outer solar system as an important source of Earth's volatile inventory

The source of and timing of delivery of the volatile elements to Earth is a question that is fundamental to understanding how our planet evolved. Here, we show that primitive meteorites have resolved mass-independent Zn isotope anomalies from the terrestrial reservoir. Carbonaceous chondrites (CC), likely originating from the outer Solar System are distinct from non-CC, and Earth is intermediate between these two components. Modelling based on these data indicates that around 30% of Earth's budget of Zn and other moderately volatile material derives from the participation of 6% of CC-like materials during Earth's accretion, with the remaining coming from NC meteorites. This implies that, despite the relatively minor mass of Earth thought to derive from CC-like material, the CC component of Earth was relatively and significantly volatile-enriched; this is in line with the observation that the terrestrial elemental abundance pattern of moderately volatile elements could be explained by a carbonaceous source, and with the carbonaceous chondrite-like isotopic budget of more volatilerich material accreted later in Earth's accretion history (e.g. Hg, Se, N, noble gases).

Automated summary

The source and timing of delivery of volatile elements to Earth are crucial for understanding the planet's evolution. Recent research suggests that primitive meteorites have provided insights into the isotopic anomalies of zinc from the terrestrial reservoir. The study shows that carbonaceous chondrites from the outer Solar System have distinct characteristics compared to other meteorites, and Earth falls in between these two components. Modeling based on these findings indicates that around 30% of Earth's zinc budget is derived from a small percentage of carbonaceous chondrite-like materials, with the remaining coming from other meteorites.