Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets

Michael A Antonelli (1) , Sang-Tae Kim (2) , Marc Peters (1) , Jabrane Labidi (3) , Pierre Cartigny (3) , Richard J Walker (1) , James R Lyons (4) , Joost Hoek (1) , James Farquhar (1)

1 University of Maryland [College Park]
2 McMaster University [Hamilton, Ontario]
3 IPGP - Institut de Physique du Globe de Paris
4 ASU - Arizona State University [Tempe]

Achondrite meteorites have anomalous enrichments in 33 S, relative to chondrites, which have been attributed to photochemistry in the solar nebula. However, the putative photochemical reactions remain elusive, and predicted accompanying 33 S depletions have not previously been found, which could indicate an erroneous assumption regarding the origins of the 33 S anomalies, or of the bulk solar system S-isotope composition. Here, we report well-resolved anomalous 33 S depletions in IIIF iron meteorites (<−0.02 per mil), and 33 S enrichments in other magmatic iron meteorite groups. The 33 S depletions support the idea that differentiated planetesimals inherited sulfur that was photochemically derived from gases in the early inner solar system (<∼2 AU), and that bulk inner solar system S-isotope composition was chondritic (consistent with IAB iron meteorites, Earth, Moon, and Mars). The range of mass-independent sulfur isotope compositions may reflect spatial or temporal changes influenced by photochemical processes. A tentative correlation between S isotopes and Hf-W core segregation ages suggests that the two systems may be influenced by common factors, such as nebular location and volatile content.

Domains: Astrophysics [astro-ph]

Michael A Antonelli, Sang-Tae Kim, Marc Peters, Jabrane Labidi, Pierre Cartigny, et al.. Early inner solar system origin for anomalous sulfur isotopes in differentiated protoplanets. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111 (50), pp.17749-17754. ⟨10.1073/pnas.1418907111⟩. ⟨insu-01859778⟩