Possible Traces of an Ancient Planet Found in Earth's Core

Two large structures, known as large low shear velocity provinces (LLSVPs), located beneath Africa and the Pacific Ocean, could be the remains of an ancient planet that hit the Earth around 4.5 billion years ago, according to the "giant impact hypothesis". These structures occupy around six per cent of the world's entire volume, and seismic tomography has shown that they are made of something different than the surrounding lower mantle. The origin of these structures remains a mystery, but studying Theia has offered important insights into how the possible collision might have kickstarted key plate tectonic and mantle motion inside our planet.