Uncovering the 'lost' planet that formed our Moon

Earth’s Moon is widely accepted to have been created 4.5 billion years ago through a giant impact between Earth and a hypothetical planet known as Theia. Yet, direct evidence for Theia's existence has remained elusive--until now. Here, we demonstrate that the mantle remnants of Theia explain fundamentally important features of the largest seismically-imaged anomalies within Earth - the two large low-shear-velocity provinces (LLSVPs) in Earth's deepest mantle. We combine state-of-art evidence from theoretical and computational astrophysics, geodynamics, mineral physics and seismology to demonstrate how Theia mantle remnants naturally provide an explanation for a compositionally distinct origin for LLSVPs, as well as their age, density and size. This study substantially expands the influence of giant-impact planetary processes in shaping Earth's evolution, with implications for comprehending the diversity of terrestrial planets and the quest for Earth-like exoplanets.

Speaker: Qian Yuan, Caltech

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Room 350/372