As Earth was molten early during its formation, dense metals should have sunk toward the core, yet iron is found closer to the surface. Did asteroids and comets deliver some of these materials?
Douglas Kaupa, Council Bluffs, Iowa
Published: Monday, September 28, 2015
This question has long puzzled planetary scientists. Shortly after our planet took shape, it was bombarded by planetesimals — rocky objects that hadn’t yet coalesced into worlds. Astronomers expected these iron-rich bodies would sink to the core after impact. Instead, we now know iron is found scattered throughout Earth’s mantle.
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