Earth’s interior may be hiding a hydrogen cache so extensive that, under some modeled scenarios, its water-equivalent content could rival or exceed the volume of today’s surface oceans, reshaping discussions of planetary history and long-term resource potential. Recent work in Nature Communications estimates that the core could contain enough hydrogen to match, and in certain cases surpass, the water now sitting at the surface, although this material lies thousands of kilometers down, locked into metal at pressures and temperatures that are extremely challenging to reproduce in the laboratory.
This contrast between vast quantity and near-total inaccessibility links deep-core chemistry to the emerging hunt for “white hydrogen” closer to the surface. Taken together, these lines of research suggest Earth is far richer in hydrogen than textbook diagrams imply, while also underscoring how little of that hydrogen can realistically be accessed with current or foreseeable technology.
How much hydrogen could Earth’s core hold?
The latest experimental estimates point to a surprisingly hydrogen-rich core. A peer-reviewed study in Nature Communications that compressed metal samples under core-like conditions reports that Earth’s core may contain between 0.07 and 0.36 weight percent hydrogen, based on measurements of hydrogen dissolved in iron alloys and extrapolated to core pressures and temperatures according to the published core analysis. Although those fractions seem small, multiplying them by the enormous mass of the core yields a planet-scale reservoir of hydrogen bound within metal rather than existing as free gas or liquid water.
Earlier modeling of core formation points in the same direction. A separate peer-reviewed investigation into how hydrogen partitioned between metal and silicate during accretion concluded that between 0.3 and 0.6 weight percent hydrogen could have been incorporated into the core as it formed, providing an upper bracket on plausible hydrogen content according to the formation scenarios. Taken together, the two studies frame a range in which even the lower bound implies a deep reservoir comparable, in water-equivalent terms, to multiple global oceans, while the upper bound would correspond to substantially more than the present-day surface inventory.
Comparing the core’s stash with Earth’s oceans
To interpret those weight percentages, they need to be compared with the water humans can see. The U.S. National Ocean Service states that the global ocean holds about 97 percent of Earth’s water, emphasizing that nearly all liquid water is concentrated in a single surface reservoir that wraps around the planet according to its water overview. This figure refers to water that is directly involved in climate, weather, and human use, in contrast to hydrogen sequestered deep within the planet’s interior.
The U.S. Geological Survey quantifies that surface store, listing “Oceans, Seas, & Bays” as having a combined volume of approximately 321,000,000 cubic miles of water in its tabulated breakdown of Earth’s water distribution, a value that has become a standard reference for ocean volume according to the agency’s water table. When researchers translate the hydrogen implied by core weight percentages into equivalent amounts of water and compare them to this 321,000,000‑cubic‑mile benchmark, some modeled combinations of core mass and hydrogen content yield totals that rival or exceed the modern ocean volume, while others fall below it, highlighting the sensitivity of such comparisons to the exact percentage assumed.
Peering into the core with atom-scale tools
Arriving at these hydrogen estimates requires tools that can resolve atoms in three dimensions. In the newer core study, the research team used three-dimensional compositional mapping with nanoscale spatial resolution, employing atom probe tomography to analyze tiny samples and directly count individual hydrogen atoms within metal grains that serve as analogues for core material, as described in the study’s detailed method section. This approach allows scientists to reconstruct how hydrogen distributes itself inside alloys under controlled high-pressure, high-temperature conditions.
Despite these advances, important limitations remain. Laboratory setups cannot yet reach the full range of pressures and temperatures found at the center of the planet, so researchers must extrapolate from experimentally accessible conditions to the more extreme regime of the actual core. As a result, the 0.07 to 0.36 weight percent and 0.3 to 0.6 weight percent ranges are best interpreted as constrained scenarios consistent with available data, rather than direct measurements of the core, and future refinements in experimental techniques or planetary models could narrow or adjust these intervals.
Where Earth’s hydrogen came from
The presence of substantial hydrogen in the core also informs debates about how Earth acquired its light elements. A peer-reviewed study on the origin of Earth’s hydrogen and carbon argues that their present-day abundances and distribution between core and mantle are tightly constrained by how these elements partitioned during accretion, treating the core as a record of early solar system conditions rather than an isolated reservoir, according to its published partitioning analysis. This perspective links deep geochemistry to larger questions about volatile delivery and retention during planet formation.
Within this framework, hydrogen is inferred to have been present during early accretion and then divided between metallic and silicate reservoirs, rather than arriving solely through late cometary or asteroidal impacts. If the core contains hydrogen at levels between 0.07 and 0.36 weight percent, as suggested by one experimental study, and potentially up to 0.6 weight percent in certain formation scenarios, as indicated by earlier modeling, then deep storage would have been a persistent feature of Earth’s evolution, with implications for the long-term cycling of volatiles between the interior and the surface.
Geologic “white hydrogen” closer to the surface
While the core’s hydrogen is effectively unreachable, another form of natural hydrogen is attracting attention nearer the surface. Reporting on “geologic” hydrogen describes it as being produced when underground water reacts with iron-rich rocks, generating hydrogen that migrates through pores and fractures and can eventually rise toward the atmosphere, a process summarized in coverage of naturally occurring white hydrogen. This naturally generated gas is often distinguished from hydrogen produced from fossil fuels (“grey” or “blue”) or from renewable-powered electrolysis (“green”).
In some geological settings, this hydrogen does not simply leak away but becomes trapped beneath low-permeability rocks such as salt or shale, forming accumulations that have been compared to natural gas fields in both structure and exploration potential. Media reports describe estimates of large quantities of hydrogen—measured in millions of tonnes—potentially trapped in such formations, although these figures remain provisional and depend on assumptions about the continuity and size of subsurface reservoirs, as discussed in accounts of trapped deposits.
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*This article was researched with the help of AI, with human editors creating the final content.
