Neon illuminates the mantle

Abstract

The outer Earth grew largely from material added by impacts from planetesimals, rather than by capture of dust grains from the solar nebula — or at least that's the inference from the latest geochemical analyses. New noble gas data from volcanic gases reveal how volatiles (compounds and elements such as water and nitrogen that are gases at high temperatures at atmospheric pressure) were incorporated into the Earth during its early history. The neon isotope measurements suggest that the primordial volatiles were implanted by solar wind into dust or small planetesimals before they coalesced to form the Earth. Previous models had proposed equilibration between a planetary wide magma ocean and the Earth's early atmosphere as the dominant source. The new data also provide insight into how the Earth's mantle has evolved since accretion.