We aren’t always lucky with asteroids. We suspect our own moon was formed when a Mars-sized object hit the proto-Earth and generated a splash of lighter weight material that formed the Moon while the heavier bits of both objects stayed together to make up our Earth. In a new paper in Science, scientists used seismographic maps of the Earth’s innards — maps like InSight is trying to make of Mars — to identify two continent-sized layers of rock buried deep inside the Earth’s mantle. These structures are unusual, and according to the article summary: [they] simply have crystallized out of the depths of Earth’s primordial magma ocean. Or they might be dense puddles of primitive mantle rock that survived the trauma of the Moon-forming impact. But based on new isotopic evidence and modeling, [lead author] Qian Yuan believes the [structures] are the guts of the alien impactor itself.
We aren’t in a position to go digging, but it is cool to think there may be shrapnel still intact in our world.
Giant Impact Origin for the Large Low Shear Velocity Provinces (LPSC Abstract)