2025-11-21 東京大学
地球深部の環境を実現するダイヤモンドアンビルセル装置（左）と高圧高温下でコアとマントル物質の化学反応を見るための実験試料（右）
＜関連情報＞
地球の水素と炭素の起源は、核マントルの分離と地球全体の存在量によって制限される Origin of Earth’s hydrogen and carbon constrained by their core-mantle partitioning and bulk Earth abundance
Yutaro Tsutsumi,Naoya Sakamoto,Kei Hirose,Shuhei Mita,Shunpei Yokoo,Han Hsu & Hisayoshi Yurimoto
Nature Communications Published:21 November 2025
DOI:https://doi.org/10.1038/s41467-025-65729-5
Abstract
Hydrogen and carbon concentrations in the Earth’s core are yet known. Here we determined their metal/silicate partition coefficients (D) simultaneously under typical conditions of core formation and found that DH and DC diminish in the presence of carbon and hydrogen, respectively, because of strong interactions between hydrogen and carbon in liquid metal, being markedly different from those separately examined in earlier experiments. With these partitioning data, we investigated the core and bulk Earth abundances of hydrogen and carbon based on core formation scenarios that are compatible with the bulk silicate Earth composition and the mass fraction and density of the core. The modelling results indicate that the Earth building blocks do not match enstatite chondrites in water abundance but require contributions by carbonaceous chondrites. The multi-stage core formation models combined with an Earth accretion scenario accounting for isotopic composition show 0.18–0.49 wt% H and 0.19–1.37 wt% C in the core, leading to 0.53–1.40 wt% H2O (present as H in the core) and 0.07–0.44 wt% C in the bulk Earth. Our modelling also demonstrates that up to 53% and 72% of Earth’s water (hydrogen) and carbon, respectively, could have been derived from non-carbonaceous chondritic materials.
