The theory, called the giant-impact hypothesis, explains many fundamental features of the moon and Earth. And many scientists assumed any debris Theia left behind on Earth was blended in the fiery cauldron of our planet’s interior. They were already aware that there are two massive, distinct blobs that are embedded deep within the Earth. That’s when he learned new details about Theia, the mysterious projectile that presumably struck Earth billions of years ago. And, as a trained geophysicist, he knew of those mysterious blobs hidden in Earth’s mantle.

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Persons: Qian Yuan, Yuan, ” Yuan, Hernán, ”, Steve Desch, it’s, wouldn’t, Desch, “, Dr, Seth Jacobson, —, Jacobson, Theia, ” Jacobson Organizations: CNN —, California Institute of Technology, Arizona State University, Arizona State’s School of Earth, Exploration, Arizona State, Caltech, NASA’s Ames Research Center, Michigan State University Locations: Africa, Arizona, Shanghai