A Caltech-led study suggests that two massive, iron-rich structures deep within Earth’s mantle are the remains of Theia, an ancient planet that collided with Earth, also creating the Moon. This discovery answers long-standing questions about the Moon’s origin and Theia’s fate.
Scientists first discovered the LLVPs by measuring seismic waves traveling through the earth. Seismic waves travel at different speeds through different materials, and in the 1980s, the first hints emerged of large-scale three-dimensional variations deep within the structure of Earth. In the deepest mantle, the seismic wave pattern is dominated by the signatures of two large structures near the Earth’s core that researchers believe possess an unusually high level of iron.
“Right after Mikhail had said that no one knows where the impactor is now, I had a ‘eureka moment’ and realized that the iron-rich impactor could have transformed into mantle blobs,” says Yuan. The next steps are to examine how the early presence of Theia’s heterogeneous material deep within the earth might have influenced our planet’s interior processes, such as plate tectonics.