Earth's Surface Water Transforms Core's Outer Layer

Researchers have discovered that water from Earth's surface can penetrate deep into the planet, reaching the core-mantle boundary and triggering a chemical reaction that alters the composition of the outermost region of the metallic liquid core. This reaction forms a distinct layer, rich in hydrogen and depleted in silicon, which creates a film-like structure. The discovery suggests a more extensive global water cycle and highlights the dynamic interaction between Earth's core and mantle, with implications for geochemical cycles connecting the surface-water cycle with the deep metallic core.