LPL Colloquium: Dr. Qian Yuan

Uncovering the "buried" planet that formed our Moon


3:45 to 4:45 p.m., Feb. 13, 2024


Dr. Qian Yuan
O.K. Earl Postdoctoral Fellow
California Institute of Technology

Uncovering the "buried" 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.

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