'A planet crashed into Earth': Scientists uncover a 2,900 km deep seismic surprise

Produced by: Mohsin Shaikh

Planet Beneath

New research suggests two colossal blobs buried 2,900 km beneath Africa and the Pacific aren't just geological oddities—they may be the fossilized remains of Theia, a lost planet that helped form the Moon.

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Twice the Moon

Each of these underground masses is nearly twice the size of the Moon. Hidden near Earth’s core, they’ve been undisturbed for 4.5 billion years—until seismic science cracked open the mystery.

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The Theia Hypothesis

Once a Mars-sized wanderer, Theia is thought to have collided with proto-Earth. The Moon rose from the debris. But now, scientists say Theia’s iron-rich guts never left—they sank and settled deep within Earth itself.

LLVP Secrets

For decades, scientists puzzled over LLVPs—giant regions where seismic waves slow mysteriously. The new theory? They're ancient planetary DNA, unmixed, unmelted, and 100% extraterrestrial in origin.

Credit: Dr. Paula Koelemeijer

4.5 Billion-Year Vault

Buried just above Earth’s core, Theia’s remnants were too dense to rise, too cold to dissolve, and too deep to notice—until seismic tomography and AI-driven simulations exposed their presence.

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Cosmic Forensics

At Caltech, scientists ran high-energy simulations of Earth’s primordial collision. The models matched seismic maps perfectly, placing Theia’s “blobs” beneath the same spots where LLVPs now lurk.

Not Earth’s Bones

The iron-rich signature of the blobs doesn’t match Earth’s internal chemistry. That chemical mismatch supports the boldest claim yet: parts of another world are lodged in ours, forming geologic “ghost organs.”

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Geology Rewritten

If these are indeed Theia’s remains, it means Earth’s structure was never “pure.” Our planet is a patchwork of cosmic collision scars—ones that still affect earthquakes, volcanoes, and the magnetic field today.

Credit: NASA

Universal Implications

If Earth swallowed another planet, what about Mars? Venus? The Moon? This discovery doesn’t just rewrite Earth’s history—it reshapes how we understand planetary evolution across the solar system.