A research team affiliated with various institutions in Germany and Japan suggests that the middle of Earth's mantle holds as much water as the planet's oceans. The team explains their experiment as well as the theory to prove that their finding is correct.

Researchers believed that the uppermost part and lower part nearest to the core are water-free since they are made up of materials that cannot store water. But, the layer in between has been long debated. Some think that it is also nearly water-free, while others claim that it holds a massive amount of water considering the mid-mantle is dominated by minerals wadsleyite and ringwoodite - can hold a lot of water.

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In this study, researchers sought to settle the debate through logic and laboratory experiments.

The team notes that a previous study revealed the mid- mantle's viscosity is lower than that of both the lower and upper mantle. To find out whether the mid-mantle holds water, researchers used the information of this prior study to conduct a laboratory experiment to replicate such situations.

The team designed a synthetic ringwoodite to serve as the mid-mantle and bridgmanite to serve as material from the lower mantle. After that, they used a method that is meant to measure the dislocation mobility to understand viscosity and then water was added to the ringwoodite.

The team explains that by doing this technique, the viscosity was reduced and met measures taken of the real mantle - suggesting that the real Earth's mid-mantle really holds water. They have estimated how waterlogged the real-world minerals are through calculating the changes in viscosity and adjusting the amount of water added to the synthetic mantle.

They used this information to determine the amount of water in the mid-mantle and reported their finding is almost equal to the water in the entire ocean of the Earth. However, further study is still needed, but scientists are convinced that the mid-mantle is filled and rich with water. It also raises a question on some theories suggesting that water came on Earth from comets.

The study was published and available in the open access site Science Advances.