In 1864, the French novelist, poet and playwright Jules Verne — the “father of science fiction” — published Journey to the Center of the Earth, a novel imagining a hidden world and a planetary ocean beneath our feet.
Monsieur Verne proved prophetic.
The presence of a vast volume of water in Earth’s mantle is not entirely new — scientific journals covered it extensively in 2014. Since then, researchers have focused on measuring the water volume in the so-called “transition zone” between the upper and lower mantle, at depths between 410 and 660 kilometers. And over time, the number of suspected mantle oceans has grown to six.
According to scientists who analyzed an exceptionally rare diamond formed around 660 km beneath Botswana — right in that transition region, there is evidence of enormous volumes of water and carbon dioxide, far larger than previously believed.
The findings, published in Nature Geoscience by Goethe University Frankfurt’s Institute of Geosciences, could reshape our understanding of Earth’s water cycle and how our planet evolved into the ocean world we know today over the last 4.5 billion years.
Source: Goethe University
It turns out the transition zone of our planet 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.
Though this deep reservoir is likely a dark sludge of sediment and hydrated rock, subjected to unimaginable pressures, its total volume is staggering. What wasn’t clear until now was how much water and CO₂ enter the transition zone via stable minerals, carbonates, or hydrated minerals.
The answer is (can you hear the drums?): roughly six times the volume of all the oceans on Earth combined.
The diamond studied contains ringwoodite — a mineral that forms only under extreme pressure and temperature in the mantle, and one that traps water remarkably well. Its presence is the key argument: where there is ringwoodite, there is abundant water.
In 2014, a similarly revealing diamond was found deep beneath Brazil, suggesting this is no isolated coincidence but a global phenomenon.
Now, the only question left is whether anyone is brave enough to launch a real journey to the center of the Earth one day — in true Jules Verne style.
This story was first published on my blog NewsCafe.