By WILIAM HUNTER, SENIOR SCIENCE & TECHNOLOGY REPORTER
Published: 10:19 BST, 1 September 2026 | Updated: 10:21 BST, 1 September 2026
Scientists have uncovered six never-before-seen mystery structures lurking deep inside the Earth.
Although our planet's deep layers are totally inaccessible, scientists can use the seismic waves from powerful earthquakes to probe the hidden depths.
Now, Chinese scientists have uncovered structures sitting on the boundary between the viscous mantle and the liquid outer core, 1,800 miles (2,900km) beneath our feet.
These 'deep-seated scatterers' are all but invisible, except for the way that they subtly influence the path of passing seismic waves.
In their paper, published in the journal JGR Solid Earth, the scientists suggest these structures could have been formed when material from the outer layers was dragged deep into the Earth.
They could include pieces of the continental crust or even the remains of Theia, a Mars-sized protoplanet believed to have formed the moon after hitting Earth 4.5 billion years ago.
Under the vast pressures and incredible temperatures at the mantle boundary, these chunks transform, partially melt, or undergo mineral transformation.
The researchers suggest that this has left six 'thermochemical piles' of material very different from the surrounding mantle.
Scientists have uncovered six never-before-seen mystery structures lurking deep inside the Earth (labelled in dashed boxes)
These structures are located right on the boundary between the solid yet malleable mantle and the liquid metal outer core (stock image)
While Earth looks relatively stable from our perspective up on the surface, deep below the planet is violent and dynamic, especially at the boundaries between layers.
One particularly dramatic boundary is the one between the mantle and the outer core, where solid-yet-viscous rocks meet liquid nickel and iron.
There is an enormous temperature jump across the boundary, with a difference of about 1,000°C (1,800°F) from one layer to another.
