How much hydrogen is in Earth's core?
Evidence for a vast hydrogen reservoir deep below
New experiments and analyses published recently suggest Earth’s core may hold far more hydrogen than previously thought. Laboratory measurements comparing the density and behavior of iron alloys under extreme pressures, together with modelling of how light elements affect core properties, point to hydrogen amounts equivalent to many times the mass of our oceans. Researchers report figures ranging up to about 45 oceans’ worth of hydrogen, or expressed another way, the core might contain roughly nine to 45 times the hydrogen found in the surface oceans.
Why this matters
- Origin of Earth’s water: If large hydrogen stores sat in the core from early in planetary formation, it weakens scenarios that require late delivery of water by comets or asteroids. Core hydrogen could represent an early internal source for some surface volatiles.
- Core and mantle chemistry: Hydrogen as a light element changes the core’s density, melting behavior and the way it interacts chemically with the mantle. That can affect heat flow, core crystallization, and the geodynamo that sustains Earth’s magnetic field.
- Long-term volatile cycling: Deep hydrogen reservoirs open a potential pathway for exchange of hydrogen between the deep interior and surface over geologic time, influencing atmospheric and ocean chemistry.
What remains uncertain
- Exact amounts and distribution: Estimates vary widely depending on laboratory calibrations and theoretical models; “up to 45 oceans” represents an upper-range interpretation, not a settled number.
- Transport processes: It’s still unclear how readily hydrogen trapped in the core could migrate to the mantle or surface, and on what timescales.
In short, the new work shifts how scientists think about hydrogen’s role in Earth’s deep interior and its influence on surface habitability, but key details about quantity, transport, and timing remain to be nailed down by further experiments and geophysical observations.