Traces of a Destroyed Planet Theia Found in Earth’s Mantle

Earth and the moon were created when a Mars-sized planetary embryo named Planet Theia collided with our young world.

Scientists have long puzzled over dense regions deep underground called Large Low Shear Velocity Provinces (LLSVPs). New evidence indicates these LLSVPs may contain pieces of an ancient world destroyed in a cataclysmic collision over 4 billion years ago.

theia collisionImage courtesy:

Qian Yuan from Caltech and colleagues conducted cutting-edge simulations recreating the aftermath of the suspected giant impact that formed Earth’s moon. Their findings provide the strongest support yet for one of astronomy’s most popular theories – that remnants of a Mars-sized planet called Theia still lie buried within our own.

What Happened to Planet Theia? New Clues to an Ancient Catastrophe

Over 100 years ago, scientists first proposed that Earth and the moon were created when a Mars-sized planetary embryo named Theia collided with our young world. This “Giant Impact Hypothesis” has become the leading explanation for how the moon came into existence.

At the time, Theia would have been approximately 10% of Earth’s mass and size. Computer models indicate it slammed into Earth at over 10,000 mph, the two partially merging in an explosion of vaporized rock before their cores reunited. Much of Theia was blown away and reaccumulated to form the moon, while the rest dispersed throughout the solar system.

Or so the theory went. Yuan’s group wondered – could some fragments of Theia still remain on Earth? Their innovative simulations tracked the behavior of mantle materials from Earth and Theia post-collision. The findings were stunning – remnants of Theia seemingly sunk deep into Earth’s mantle, gradually coalescing into two dense piles over billions of years.

Those puddles correspond precisely in location and density to the known LLSVP formations, one under Africa and the other the Pacific. Further, geochemical signatures within LLSVP plumes match lunar compositions better than native Earth rocks. The evidence points to the mantle’s dense blobs containing our sole trace of a destroyed terrestrial planet – Theia.

How Big Was Theia? Implications of a Survivng Remnant

Standing roughly one-third Earth’s diameter,Theia packed enough material to forever alter our planet’s trajectory had it struck at a slightly different angle or time. Its collision fragmented Earth’s initial crust, ejecting iron and sulfur into orbit to eventually coalesce as our moon – solving longstanding mysteries as to how Earth stabilized its spin and where the moon materialized from.

Finding tangible remnants of Theia embedded in the mantle has major bearings on understanding Earth’s dramatic origins and habitability. It confirms the prevailing giant impact hypothesis after decades of indirect support. More pieces of Theia may emerge from additional study of the LLSVPs’ unique compositions.

Altogether, the discovery adds new color and complexity to Earth’s beginnings. Our world was not simply forged from swirling gas and dust aeons ago, but shaped through cataclysmic astronomical circumstances eons in the making. Buried within lie frozen truths from the cosmos – remnants of a Titan whose collision birthed the only home we’ve ever known.

Theia’s Trace Elements: Chemical Clues from the Deep Earth

To further test their theory, Yuan’s group suggests geochemists hunting for isotopic “fingerprints” matching Theia’s mantle composition within basalts sourced from the LLSVPs. Plumes rising from the dense blobs offer a potential window to probe their makeup without drilling over a kilometer underground.

Certain elements like tungsten and molybdenum form different isotopes under varying conditions early in solar system history. Comparing LLSVP basalt ratios to lunar and martian meteorites could provide a definitive “smoking gun” linking them to Theia’s mantle. Ongoing seismic mapping may also image the blobs at higher resolution, revealing internal structures hinting at an extraterrestrial origin.

As tools and databases expand, opportunities grow to scrutinize Earth’s deep interiors like never before. Additional exploration holds promise to pin down exactly what types and proportions of Theia persist in our living planet. With further clues extracted from the dense remains, more light may shine on the momentous collision that established the very framework for life’s emergence on Earth.

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