Two enormous structures that sit at the border between the Earth’s mantle and its core have puzzled scientists for decades, defying reigning theories of how our planet came to be. The continent-sized lumps of dense, hot rock lie almost 1,800 miles beneath the surface under Africa and the Pacific Ocean. “If we start from the magma ocean and do the calculations, we don’t get what we see in Earth’s mantle today. “What we proposed was that it might be coming from material leaking out from the core,” Miyazaki said. It could also indicate why other planets, including Venus and Mars, became inhospitable hellscapes incapable of supporting life as we know it while Earth thrived.