Superionic hydrogen, an exotic state of matter that flows like liquid while conducting electricity, likely permeates the Earth’s inner core, according to a study published in the Proceedings of the National Academy of Sciences. Researchers analyzing core conditions modeled three types of hydrogen structures to determine which phase dominates Earth’s center under extreme pressure and temperature.
Modeling Superionic Hydrogen Phases in Earth’s Core
To understand hydrogen distribution within the planet, researchers modeled three distinct elemental forms. These included two types of superionic iron-hydrogen alloys featuring hydrogen flowing through crystalline iron lattices arranged in different ways, according to the PNAS study.
The first arrangement is the hexagonal close-packed (HCP) structure, while the second is the body-centered cubic (BCC) arrangement. Calculations by the research team show that the BCC phase possesses higher free energy, making it less stable and more reactive than the HCP phase. By contrast, the HCP phase exhibits greater thermodynamic stability under intense planetary pressures.
Did you know? Only 39 fingers’ worth of people have ever visited the ocean’s deepest depths or the surface of the Moon, leaving the Earth’s core as a nearby alien environment that no human will ever personally explore.
Melting Limits and Inner Core Boundaries
Extreme conditions deep within the planet dictate which atomic structures can survive. Hypothetically, the BCC phase may become more stable than the HCP phase only when temperatures surpass 6,400 Kelvin (6,100 degrees Celsius or 11,000 degrees Fahrenheit) and hydrogen content exceeds 20 percent at 3.6 million atmospheres of pressure.
However, researchers found that these extreme conditions likely melt the BCC phase into an igneous iron slushy. Consequently, the study concludes that only the superionic HCP structure coexists with the liquid iron-hydrogen system in the inner core.
Radial Concentration Gradients and Core Dynamics
A radial concentration gradient appears to govern total hydrogen within the inner core. According to the study, hydrogen composition drops sharply when crossing the boundary from the outer core and traveling toward the center of the inner core.
This radial gradient drives superionic hydrogen toward the inner core boundary. Once there, it loses superionic status and re-partitions into a liquid mix that enriches the outer core. Researchers state that this continuous redistribution, alongside inner core crystallization occurring at a rate of 1 millimeter per year, contributes to chemical buoyancy—an energy source believed to drive the geodynamo.
Frequently Asked Questions
What is superionic hydrogen?
Superionic hydrogen is an otherworldly phase of matter where hydrogen flows like a liquid while maintaining the ability to conduct electricity. It forms only under extreme conditions found in planetary interiors.
How does hydrogen move between Earth’s inner and outer core?
Hydrogen exchange occurs through both the direct partitioning of crystallizing inner core material and a continuous redistribution of superionic hydrogen driven by equilibrium thermodynamics.
What controls hydrogen distribution in the core?
According to the published study, the nonuniform distribution of superionic hydrogen is controlled primarily by temperature rather than pressure.
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