Scientists have found two new compounds that can trap the building blocks of water

The findings were published in Nature Geoscience led by researchers at China’s Centre for High Pressure Science and Technology Advanced Research.

The two compounds, Fe₅O₁₂Hₓ and Fe₇O₁₂Hₓ, are called iron oxyhydroxides. They don’t contain water itself but instead they hold the “building blocks” of water | Representative Image

New Delhi: The Earth could have a large reservoir of water hidden nearly 2,900 km beneath its crust. However, much of this “water” is not in the form of an underground ocean, instead it is likely to be stored in compounds that can trap both hydrogen and oxygen.

In a recent breakthrough, scientists have found two new iron-rich compounds which can store hydrogen deep inside the Earth’s mantle. The findings were published on 8 September in Nature Geoscience led by researchers at China’s Centre for High Pressure Science and Technology Advanced Research.

“Liquid water is the key component of Earth’s habitability. Identifying these iron oxyhydroxides is important because they are seemingly stable, dense phases that capture and retain water across a wide range of lower-mantle conditions,” wrote geoscientist Alfred Wilson from the University of Leeds in a commentary accompanying the study.

The two compounds, Fe₅O₁₂Hₓ and Fe₇O₁₂Hₓ, are called iron oxyhydroxides. They don’t contain water itself but instead they hold the “building blocks” of water. To test this out, researchers recreated the conditions of the Earth’s inner layers inside a lab. They placed samples of the two compounds between diamond tips and squeezed them under pressure, heated them with lasers up to 2,500°C to observe the result.

What they found was that the compounds could retain hydrogen particles even when there was not much water around to begin with. This suggests that such iron compounds might exist in layers between the mantle and the core, one the least understood parts of the planet.

“The minerals needed to transport water into the deepest parts of the Earth’s mantle remain unclear. High-pressure and high-temperature experiments conducted at lower-mantle conditions suggest that iron oxyhydroxide phases may be important to such transport,” wrote Wilson.

While it is known that water seeps into the Earth when tectonic plates shift or sink, such research suggests that some of that water could get trapped into iron-rich minerals and remain there for extremely long periods of time.

Scientists are yet to establish whether the newly identified compounds can occur naturally inside the Earth.