Remnants of Theia, an Ancient Planet, May Be Entombed in Earth’s Mantle

Chunks of an ancient planet called Theia may be trapped in Earth’s mantle, according to new research. The prevailing theory of the moon’s formation is the giant impact hypothesis, which suggests that Theia collided with Earth, resulting in the creation of the moon from the debris. However, it seems that remnants of Theia may still exist, specifically in the form of two dense regions in Earth’s mantle known as large low-shear-velocity provinces (LLVPs).

Scientists have known about the existence of these two areas in the mantle for several decades. The LLVPs, located beneath Africa and the Pacific Ocean, behave differently from the surrounding rock and seismic waves travel through them more slowly. Qian Yuan and his colleagues at the California Institute of Technology proposed a connection between the giant impact and the LLVPs. They conducted simulations to study how Theia’s rubble would have behaved after the collision with Earth.

The results showed that rocks from Theia’s mantle would have melted and sunk to the boundary between Earth’s mantle and core, forming a thin layer that coated the entire core. Over time, convection within Earth’s mantle would have collected this dense material, creating the two LLVPs. Unfortunately, digging deep enough to confirm this theory is not currently possible. However, hot material rises from the LLVPs, carrying with it chemical signals that could provide evidence of their origin.

Chemical signatures found in the plumes from the LLVPs resemble those found on the moon but are not typically found on Earth. This suggests that the LLVPs, along with the moon, may indeed be remnants of Theia, supporting the giant impact hypothesis. This significant event, according to Yuan, played a crucial role in shaping Earth’s atmosphere, crust, mantle, and core, making our planet unique. Yuan also suggests that studying other planets that have experienced giant impacts could help in the search for Earth-like planets.