Alien Planet Inside Earth

In new research, scientists speculate that Earth was formed by a Mars-sized rogue planet known as Theia—with identifiable bits of the alien planet still found in Earth’s interior.

Scientists believe the same fateful impact also formed the moon, but this is the first time they’ve studied the specific traces of the clash that remain behind in the Earth’s mantle.In 2016, UCLA researchers proposed that Earth could actually be two planets that fused together after colliding: itself and Theia. At the time, scientists said they believe the two planetary masses mixed together uniformly. Now, Qian Yuan of Arizona State University and his colleagues suggest the mysterious dense spots in Earth’s interior are the specific pieces of Theia that are still intact.

Yuan’s team presented a paper earlier this month at the 52nd Lunar and Planetary Science Conference they explain 

Here, we demonstrate that theia’s mantle may be several percent intrinsically denser than Earth’s mantle, which enables the theia mantle materials to sink to the Earth’s lowermost mantle and accumulate into thermochemical piles that may cause the seismically-observed [dense areas].These dense areas are “continent-sized Large Low Shear Velocity provinces.