Hydrogen, a key ingredient of water, may have been seeping out of Earth’s metallic core and into the rocky mantle above it for billions of years, according to a new computer-modeling study in Science Advances.
The work comes from geoscientists at the University of Science and Technology of China in Hefei. It offers a possible explanation for a long-standing puzzle in volcanic rocks, and it hints that the core and mantle trade material more than textbooks once assumed.
The puzzle in the lava
Hydrogen comes in two common forms: ordinary hydrogen and a heavier version called deuterium. Geochemists track the ratio of the two, known as the D/H ratio, because it works like a fingerprint for where water-forming material came from.
Some volcanic rocks from places such as Baffin Island in the Canadian Arctic and Iceland carry unusually low deuterium levels. Those rocks are thought to come from hot upwellings that start near the boundary between the core and the mantle. So the question is why the deep Earth holds so much light hydrogen.
What the researchers did
The team ran machine-learning-enhanced simulations that model the quantum behavior of atoms. They used them to follow how the two forms of hydrogen would have been distributed as Earth’s early ocean of molten rock cooled and crystallized, roughly 4.5 billion years ago.
In their models, that cooling produced a mantle with an essentially uniform hydrogen signature. The result held across wide swings in pressure, temperature and starting assumptions. In other words, the early cooling process alone could not easily create the strongly low-deuterium pockets seen in those volcanic rocks.
The authors argue that the signal must instead reflect ongoing exchange between core and mantle over Earth’s history. As iron sank to form the core, it would have drawn in lighter hydrogen. Over time, some of that light hydrogen could have worked its way back out and into the lowest part of the mantle.
Other clues point the same way
Press coverage of the study notes that other deep-Earth signals fit the idea. Some of the same kinds of volcanic rocks show unusually high ratios of helium-3 to helium-4, which may be leftover primordial helium, along with odd tungsten isotope patterns that suggest a contribution from the core. Those observations come from earlier work, not from this simulation.
Why it matters for everyday readers
Nothing here will change your weather or your water bill. But it matters for how scientists think about the planet’s long-term plumbing. If the core really does leak material upward, then the deep interior is not a sealed vault. It is part of a slow cycle that may have helped shape the chemistry of the mantle, and perhaps some of what eventually erupts at the surface.
It also feeds a bigger debate about where Earth’s water came from. This study does not settle that question, and the headline claim that the core is “leaking water” is a simplification. The research concerns hydrogen, one of water’s building blocks, not liquid water.
For context, the core sits roughly 1,800 miles (2,900 kilometers) below the surface, far beyond any drill. That is why scientists rely on clues like isotope ratios in lava, which act as rare messages from the deep. Each new line of evidence, and each independent simulation, helps narrow down what the planet’s interior is really doing.
The catch
This is a modeling study. Nobody can sample the core, so the conclusions rest on simulations plus indirect clues in rocks. The results depend on assumptions, especially the starting hydrogen composition of the early magma ocean. Reporting on the paper does not explain how hydrogen physically moves from core to mantle, and the researchers say that is a target for future work. Other teams will want to test the idea with their own models and data.
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