Researchers are talking about evidence that at a depth of hundreds of kilometers beneath Botswana, there is a large...very large volume of water.

In 1864, French writer Jules Verne published the adventure novel "Journey to the Center of the Earth," a fantasy about the discovery of a world and a planetary ocean beneath Earth's crust. Monsieur Verne proved to be a prophet.

The existence of an ocean in the mantle of our planet is no longer new – this was extensively written about in science journals in 2014. Since then, researchers have tried to quantify the volume of water in the so-called "transition zone" between Earth's upper mantle and lower mantle, a layer at a depth of between 410 and 660 km.

Since then, the number of suspected oceans existing in the mantle of the planet has grown to six.

A team of scientists notes in a statement that, after analyzing an extremely rare diamond, formed at a depth of about 660 km beneath the African state of Botswana, between Earth's upper and lower mantle, in the so-called transition region, there is an enormous volume of water and carbon dioxide than previously believed.

The research results, systematized in a study published by the Institute of Geo-Sciences of the Goethe University in Frankfurt in the journal "Nature Geoscience," could have profound implications for our understanding of the water cycle and how the planet evolved into an oceanic world – as we know it today – over the last 4.5 billion years.

"In this study, we have shown that the transition zone is not a dry sponge, but contains significant amounts of water...[...] bringing us one step closer to Jules Verne's idea of an ocean inside the Earth," says the German institute's statement.

While this vast reservoir is likely a dark sludge of sediment and hydrated rock – and is subject to almost inconceivable pressures – as a total volume, it can have extraordinary proportions, containing vast quantities of water and CO2.

What was not clear until now is the volume that enters the transition zone in the form of more stable minerals and carbonates or hydrated minerals, and therefore, no one could answer the question of how much water is stored there.

The answer is as follows: a volume about six times larger than all the oceans on Earth combined.

The diamond analyzed by the team members comes from a region in Earth's mantle where there are the most deposits of ringwoodite – a mineral that only forms under high pressures and temperatures in Earth's mantle but can retain water quite well.

This is also the main argument – if the diamond contains ringwoodite, then there is a lot of water there.

In 2014, another diamond with the same properties was discovered in the depths of Brazil, which excludes coincidence and speaks of a global phenomenon.

It remains to be seen if there will be an Elon Musk among us who will launch a real journey in the style of Jules Verne.