Seismologists have recognised since the 1970s that two mysterious continent-sized blobs reside in the deepest part of Earth's mantle, one under Africa and the other under the South Pacific region.
These blobs, denser than the material surrounding them, may be relics from a cataclysm early in our planet's history hypothesised to have spawned the moon - the collision between primordial Earth and a Mars-sized object called Theia, researchers said on Wednesday.
This giant impact, which recent research determined occurred more than 4.46 billion years ago, blasted molten rock into space that orbited Earth and coalesced into the moon. But chunks of Theia may have remained inside Earth, sinking to a location just above our planet's wickedly hot spherical core of iron and nickel.
