Differentiated planetesimals record differing sources of sulfur in inner and outer solar system materials.

Abstract

The isotope anomalies of noncarbonaceous (NC) and carbonaceous (CC) extraterrestrial materials provide a framework for tracing the distribution and accretion of matter in the early solar system. Here, we extend this framework to sulfur (S)-one of six "life-essential" volatile elements [T_C ~ 664 K]-via the mass-independent S-isotope compositions of differentiated meteorites. We observe that on average, NC and CC iron meteorites are characterized by distinct Δ³³S (Δ³³S_NC = 0.013 ± 0.003‰; Δ³³S_CC = -0.021 ± 0.009‰; 2 SE). The average Δ³⁶S of NC and CC irons are less well resolved (Δ³⁶S_NC = -0.006 ± 0.039‰; Δ³⁶S_CC = -0.101 ± 0.114‰; 2 SE), but the Δ³⁶S values of the CC irons are concentrated in the lower half of the range of those observed for iron meteorites. A lack of CC achondrite S-isotope analyses prevents direct comparison of the Δ³³S and Δ³⁶S of NC and CC achondrites, but the average Δ³³S and Δ³⁶S of NC achondrites (Δ³³S = 0.02 ± 0.008; Δ³⁶S = -0.019 ± 0.064‰; 2 SE) overlap with those of the NC irons. The average Δ³³S values of NC achondrite groups also correlate with nucleosynthetic anomalies of other elements (e.g., Cr) previously used to define isotopic heterogeneity within the NC reservoir. The position of the Earth in Δ³³S-Δ³⁶S composition space implies that ~24% of terrestrial S derives from CC materials, while the majority (~76%) was delivered by NC materials.