Are the remains of an ancient planet deep inside Earth?

“In the 1980s, geophysicists made a startling discovery: two continent-sized blobs of unusual material were found deep near the center of the Earth, one beneath the African continent and one beneath the Pacific Ocean. Each blob is twice the size of the Moon and likely composed of different proportions of elements than the mantle surrounding it.”

What are these mysterious blobs?

New geophysics research from Caltech suggests the blobs, known as the large low-velocity provinces (LLVPs), could be buried relics from something called the Giant-Impact Hypothesis or the Theia Impact. In this hypothesis, an ancient Mars-size planet we call Theia smashed into proto-Earth, creating the Moon 4.5 billion years ago.

Scientists have long looked to space to find traces of Theia’s existence, but this research suggests they were looking in the wrong direction.

In the Caltech video above, geodynamicist Qian Yuan introduces the compelling evidence—simulations, chemical analyses, and high-resolution mantle convection studies—that Theia’s remains have been found. From Caltech:

“Yuan worked with multidisciplinary collaborators to model different scenarios for Theia’s chemical composition and its impact with Earth. The simulations confirmed that the physics of the collision could have led to the formation of both the LLVPs and the Moon. Some of Theia’s mantle could have become incorporated into the Earth’s own, where it ultimately clumped and crystallized together to form the two distinct blobs detectable today at Earth’s core–mantle boundary today; other debris from the collision mixed together to form the Moon.”

Watch these related videos next:
• Did the moon form in just a few hours? NASA Ames investigates.
• A NASA-Guided Tour of How the Moon Evolved
• Moon 101, a quick primer on our 4.51 billion-year-old natural satellite
• Earthrise from the moon, captured by JAXA Kaguya Spacecraft

Bonus: We Are Dead Stars. Dr. Michelle Thaller explains.