An unexpected discovery has been found in the Earth's core

American researchers modeled the state of hydrogen in Earth's inner core and concluded that so-called superionic hydrogen may exist there — a substance that flows like a liquid while also conducting electricity. The results were published in the journal PNAS.

The scientists examined two crystal structures of an iron-hydrogen alloy: hexagonal close-packed (HCP) and body-centered cubic (BCC). Under normal conditions, the BCC structure is less stable and more reactive than HCP. The BCC structure becomes more stable only at temperatures above 6,400 kelvins and hydrogen concentrations of at least 20% at pressures of approximately 3.6 million atmospheres — however, such extreme conditions, according to the authors' calculations, would more likely lead to the complete melting of the substance into something resembling a "fiery iron mush" rather than a stable structure.

Therefore, the authors consider the existence of a superionic phase of hydrogen more likely specifically in the HCP structure, which can coexist with the liquid material of the outer core. The scientists also discovered a radial gradient in hydrogen concentration: its amount drops sharply at the boundary between the outer and inner core.

According to the researchers, hydrogen exchange between core layers is not limited to the crystallization process — there is also a constant redistribution of the element, which creates so-called chemical buoyancy that supports the operation of the geodynamo generating the planet's magnetic field. Earth's inner core grows by approximately one millimeter per year, and the distribution of hydrogen between layers is determined primarily by temperature rather than pressure.