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Rock from the impact that formed the moon may linger in Earth’s mantle

Strangely dense rock in the mantle is from an impact 4.5 billion years ago, researchers say

An illustration of a large rock hitting what looks like a planet.

Continent-sized zones of dense rock — leftovers from the cosmic collision (illustrated) that formed the moon — sit atop Earth’s core, a study finds.

Hernán Cañellas

By Sid Perkins

About 4.5 billion years ago, a Mars-sized object smashed into the young Earth, spraying debris that coalesced to form the moon, many scientists think. Some remnants of that object, called Theia, exist today as large amounts of dense material sitting atop Earth’s core, researchers propose November 1 in Nature.