Graduate student Qian Yuan (ASU) and colleagues looked at continent-size features deep in Earth’s mantle, known as large, low shear velocity provinces (LLSVPs). While the cores of Earth and Theia probably merged right away, where did the rest of the rogue impactor go? An animation of LLSVP regions deep within the Earth, based on seismic tomography. Stable isotope samples brought back by Apollo astronauts also suggest a common origin for Earth and the Moon.īut direct evidence for Theia hypothesis has so far been lacking. The abundance of indirect evidence for this cataclysmic event includes the high angular velocity seen in the Earth-Moon system today, as well as the Moon's tiny iron core and high mass ratio relative to Earth. The leading theory for the formation of the Moon is that a roughly Mars-size object, dubbed Theia (named for the Titan who was mother to the moon goddess Selene), struck young Earth around 4.5 billion years ago. The study will appear in Geophysical Research Letters. Their study posits that the large Theia impactor that struck Earth early on in its history, leading to the Moon's formation, might have left large, dense masses deep in our planet’s mantle today. Researchers out of Arizona State University (ASU) made their case in a great piece of planetary forensics presented at the virtual 52nd Lunar and Planetary Science Conference. An artist's conception of Theia hitting the Earth.Įvidence for the past impact that created our one large Moon might lie far beneath our feet.