The remnants of a protoplanet that slammed into Earth and created the moon may still be lurking deep in our planet's mantle.
New research suggests that this impactor, which hit a just-formed Earth 4.5 billion years ago, still exists in Earth's mantle as two mysterious "blobs" that have long puzzled geoscientists. These blobs, known as large low-shear-velocity provinces (LLVPs), are places where seismic waves move more slowly than the rest of the mantle, suggesting there's a difference in temperature, composition or both.
