Fluid Water May Be Hiding Deep in Earth's Mantle, Diamond Reveals

Pockets of water may lie as deep as 500 miles into the Earth's mantle, unique diamond impurities reveal.

Scientists discovered a mysterious form of crystallized ice known as ice VII trapped inside diamonds. This is the first time the mineral has been observed in nature, and it could change how scientists understand the make-up of the Earth.

The diamonds were analyzed in a study published in Science.

Diamonds offer scientists a glimpse inside Earth. The prized carbon gems are created under intense pressure over many millions of years. Most were formed 100 to 150 miles into the mantle, while some were created as deep as 500 miles. The rocks can trap other minerals from the mantle and slowly carry them to the surface.

For geologists, these impurities or "inclusions" can be of great scientific value. Some, like ice VII, have never been observed naturally before. Ice VII had only been seen in lab experiments of materials under high pressure.

Read more: Super-deep diamond reveals mineral from Earth's mantle never seen by human eyes

These diamonds would have formed under extremely hot temperatures of more than 1,000 degrees Fahrenheit.

Although it's solid in the diamond, ice VII would have been liquid inside the mantle. This suggests pockets of water lie deep within the Earth's interior, nestled among iron, aluminum and other ingredients that make up the mantle.

Finding ice VII came as a surprise to the team who were searching for a far more familiar substance.

"We were looking for carbon dioxide," study author Tschauner said in a statement. "We're still looking for it, actually."

These pockets of water could be a "global phenomenon," Tschauner said. His team studied diamonds discovered in China, South Africa and Botswana.

This discovery will help scientists create more accurate models of the Earth's interior. Specifically, it can help them get a better idea of the movement of heat-generating radioactive elements under the planet's crust, Tschauner said.

"It's another piece of the puzzle in understanding how our planet works," he added.