Around 4.5 billion years ago, the young Earth was largely a molten world. As the planet heated and gradually differentiated, dense iron sank toward its center, forming the metallic core, while lighter silicate materials rose to form the mantle. This separation shaped Earth’s internal structure, but it may not have marked the end of the interaction between these two vast reservoirs.
In a recent study published in Science Advances, scientists investigated whether Earth’s core has remained isolated from the mantle or whether material has continued to move between them over billions of years. The scientists turned to unusual chemical signatures found in volcanic rocks, which could offer clues that trace back to Earth’s earliest history.
The findings suggest that hydrogen—a key component of water—has been leaking from the planet’s metallic core into the lowest layer of the mantle, eventually influencing the composition of volcanic rocks at the surface.
Earth’s interior is not necessarily chemically uniform. Some regions of Earth’s deep mantle retained material from the planet’s formation, surviving the enormous heat and mixing of its early history. Some unusual material may have originated in the core and later traveled toward the overlying rocky mantle.
The researchers behind the new study used computer simulations to replicate conditions found deep inside the Earth. They set out to examine how two forms of hydrogen, standard light hydrogen and a heavier version called deuterium, behaved as molten rock cooled and crystallized into different minerals.
The simulations revealed that as Earth’s ancient magma ocean cooled and crystallized, its two forms of hydrogen were distributed relatively evenly throughout the mantle.
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