Lab-Made Minerals Hint at How Earth Could Store Water Deep Below

Scientists have created two previously unknown iron compounds that can retain hydrogen under conditions resembling Earth’s deep interior. The laboratory result offers a new clue to how water could be stored about 2,900 kilometres beneath our feet, near the boundary between the rocky mantle and the core.

In the study, published in Nature Geoscience, researchers squeezed tiny samples between diamonds and heated them with lasers. Intense X-rays allowed the team to examine the resulting crystals and work out their structure. The compounds formed even when the starting material contained less than 0.1% water, suggesting that very little hydrogen is needed to make them stable.

This would not be an underground ocean. Instead, hydrogen, a component of water, would be locked within the minerals’ structure. The researchers suggest that these dense minerals could have formed as the young Earth cooled, then sunk towards the core, potentially keeping water stored for billions of years.

That possibility remains unconfirmed: neither compound has yet been shown to exist naturally inside Earth. Scientists also need to establish exactly how much water they could hold and how readily they might release it.