¹Nicole X. Nie,^1,2Da Wang,¹Zachary A. Torrano,¹Richard W. Carlson,¹Conel M. O’D. Alexander,¹Anat Shahar
Science 379, 6630 Link to Article [DOI: 10.1126/science.abn178]
¹Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC 20015, USA.
²International Center for Planetary Science, College of Earth Sciences, Chengdu University of Technology, 610059 Chengdu, China.
Reprinted with permission from AAAS

Meteorites record processes that occurred before and during the formation of the Solar System in the form of nucleosynthetic anomalies: isotopic compositions that differ from the Solar System patterns. Nucleosynthetic anomalies are rarely seen in volatile elements such as potassium at bulk meteorite scale. We measured potassium isotope ratios in 32 meteorites and identified nucleosynthetic anomalies in the isotope potassium-40. The anomalies are larger and more variable in carbonaceous chondrite (CC) meteorites than in noncarbonaceous (NC) meteorites, indicating that CCs inherited more material produced in supernova nucleosynthesis. The potassium-40 anomaly of Earth is close to that of the NCs, implying that Earth’s potassium was mostly delivered by NCs.

¹Rayssa Martins,¹Sven Kuthning,¹Barry J. Coles,¹Katharina Kreissig,¹Mark Rehkämper
Science 379, 6630 Link to Article [DOI: 10.1126/science.abn1021]
¹Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK.
Reprinted with permission from AAAS

Material inherited from different nucleosynthesis sources imparts distinct isotopic signatures to meteorites and terrestrial planets. These nucleosynthetic isotope anomalies have been used to constrain the origins of material that formed Earth. However, anomalies have only been identified for elements with high condensation temperatures, leaving the origin of Earth’s volatile elements unconstrained. We determined the isotope composition of the moderately volatile element zinc in 18 bulk meteorites and identified nucleosynthetic zinc isotope anomalies. Using a mass-balance model, we find that carbonaceous bodies, which likely formed beyond the orbit of Jupiter, delivered about half of Earth’s zinc inventory. Combined with previous constraints obtained from studies of other elements, these results indicate that ~10% of Earth’s mass was provided by carbonaceous material.