Overview
- The MIT-led study, published October 14 in Nature Geoscience, reports a distinct potassium-40 deficit in ancient rocks from Greenland and Canada and in mantle-derived Hawaiian lavas.
- High-precision mass spectrometry detected a reproducible isotope imbalance relative to most modern Earth materials, and analyses found no known modern geological process could generate it.
- Impact and accretion simulations using documented meteorite compositions evolve a potassium-40–deficient starting material to match typical present-day Earth compositions.
- The isotopic signature does not precisely match any known meteorite, indicating gaps in the meteorite inventory and leaving the exact source material unresolved.
- Lead author Nicole Nie describes the result as possibly the first direct evidence of preserved pre–giant-impact material in Earth’s mantle, with further sampling and isotopic surveys identified as next steps.