Mysterious Continent-sized Blobs in Earth's Mantle

Seismologists discovered two massive blobs in the deepest part of Earth's mantle in the 1970s, and now researchers suggest that these dense blobs are leftovers from a massive collision early in Earth's history. The collision, believed to have led to the formation of the moon, involved a Mars-sized object called Theia that impacted primordial Earth over 4.46 billion years ago. Computer simulations of the impact, the material involved, and the evolution of Earth's mantle led the researchers to propose that the blobs are remnants of Theia, which sank to the bottom of Earth's mantle, while the residual debris formed the moon. The discovery of these blobs could provide tangible evidence of the hypothesized moon-forming collision. These dense blobs, with high levels of iron similar to moon rocks, may offer insight into the events that shaped Earth and other rocky planets.