Relics of huge primordial collision reside in Earth's deep interior

Seismologists have discovered two continent-sized blobs in the Earth's mantle, one under Africa and the other under the South Pacific region. These blobs, denser than their surroundings, may have formed from the remnants of a collision between Earth and a Mars-sized object called Theia. Computer simulations suggest that most of Theia was absorbed into Earth, forming the blobs, while residual debris formed the moon. If this theory is correct, the blobs would provide the first direct evidence of the moon-forming collision.