Chalcogen isotopes reveal limited volatile contribution from late veneer to Earth

Wenzhong Wang; Michael J Walter; John P Brodholt; Shichun Huang; Michail I Petaev

doi:10.1126/sciadv.adh0670

Chalcogen isotopes reveal limited volatile contribution from late veneer to Earth

Sci Adv. 2023 Dec 8;9(49):eadh0670. doi: 10.1126/sciadv.adh0670. Epub 2023 Dec 6.

Authors

Wenzhong Wang^{1

2

3

4}, Michael J Walter³, John P Brodholt^{4

5}, Shichun Huang⁶, Michail I Petaev⁷

Affiliations

¹ Deep Space Exploration Lab/School of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
² CAS Center for Excellence in Comparative Planetology, University of Science and Technology of China, Hefei, Anhui 230026, China.
³ Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA.
⁴ Department of Earth Sciences, University College London, London WC1E 6BT, UK.
⁵ Centre of Planetary Habitability, University of Oslo, Oslo, Norway.
⁶ Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA.
⁷ Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.

Abstract

The origin of Earth's volatile elements is highly debated. Comparing the chalcogen isotope ratios in the bulk silicate Earth (BSE) to those of its possible building blocks, chondritic meteorites, allows constraints on the origin of Earth's volatiles; however, these comparisons are complicated by potential isotopic fractionation during protoplanetary differentiation, which largely remains poorly understood. Using first-principles calculations, we find that core-mantle differentiation does not notably fractionate selenium and tellurium isotopes, while equilibrium evaporation from early planetesimals would enrich selenium and tellurium in heavy isotopes in the BSE. The sulfur, selenium, and tellurium isotopic signatures of the BSE reveal that protoplanetary differentiation plays a key role in establishing most of Earth's volatile elements, and a late veneer does not substantially contribute to the BSE's volatile inventory.