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Iron Rain

August 18, 2015

The young planet Earth may have received some occasional showers. Not cooling rain showers like you might hope for on a summer afternoon, but showers of liquid iron — the aftermath of collisions between Earth and big asteroids.

Researchers came to that conclusion after vaporizing bits of iron in the Z machine, a test chamber at Sandia National Laboratories. The machine uses powerful pulses of electricity to create X-rays and strong magnetic fields.

The researchers were trying to understand why there are blobs of iron in Earth’s mantle — the layer of hot rock beneath our planet’s crust.

The iron probably came from iron-rich asteroids that slammed into the young Earth. But that’s a puzzler, because big blobs of iron should have settled into Earth’s iron core.

So the researchers wondered if perhaps the iron vaporized in the collisions, then condensed and fell to Earth as rain. The smaller iron “raindrops” would have then collected in the mantle.

Theoretical models say the conditions in the impacts shouldn’t have been extreme enough to vaporize the iron. But the researchers used the Z machine to instantly squeeze and heat small samples of iron. Their tests showed that the iron vaporized at pressures similar to the conditions found in asteroid collisions — suggesting that the young Earth could have been pelted with showers of iron.

We’ll talk about another Z machine experiment tomorrow.


Script by Damond Benningfield, Copyright 2015

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