☄️ Campo del Cielo

Older than the Earth

Where the little block of iron in the glass box came from, and how we know.

It looks like a lump of metal.

But it’s 39 grammes of another world.

And it’s older than the planet you’re standing on.

The object

First, look closely at what’s actually in the box

When you pick it up, the first thing you notice is the weight. It’s much heavier than a stone that size would be, because it isn’t stone at all. It’s solid metal all the way through. The little thumbprint dents on its surface are called regmaglypts, and they were melted into it as it fell.

Your turn. Tap each metal to find out how much of it is in there.

There are four metals in it. Start with the biggest one.

Four and a half billion years ago, there was no Earth.

There was only a young Sun, with a cloud of dust around it.

The dust slowly clumped together into small planets.

In one of them, this metal sank to the core.

The proof

How do we know it’s a planet’s core?

The answer is inside the metal. If you cut an iron meteorite open, polish it and brush it with acid, a pattern of criss-cross bands appears. The bands are crystals of iron and nickel, and together they’re called the Widmanstätten pattern. That pattern only grows in metal that cools extremely slowly.

Your turn. Use the slider to choose how slowly some melted iron and nickel cools, and find out how slow it has to be.

Cooling speed: red-hot to cold in a day

Cooled in a day, the way a blacksmith would. The metal goes solid before any pattern can grow. Every piece of iron people have ever made looks like this inside, with no pattern at all.

Then a collision smashed that little world apart.

For most of the next four billion years, its iron core stayed packed inside the rubble of a bigger body…

…until, in the last few hundred million years, it broke free and drifted through space on its own.

Then one night, the Earth got in its way.

The journey

The long way to a shelf in Ireland

Drag the slider to follow where it’s been, from the very start.

4.5 billion years ago

Forged. Deep inside a young planet, melted iron sinks to the centre and very slowly sets solid. This is where your piece begins, in the core of a planet that no longer exists.

There’s one more thing to know.

There’s iron in you too. It’s what makes your blood red.

And every atom of it was made inside a star.

Same stardust

Your iron and its iron came from the same place

The Earth doesn’t make its own iron. Every atom of it was made inside dying stars and scattered when those stars blew apart. The iron in gates and pans has been melted down and reshaped by people over and over again, but nobody has ever done that to the iron in this box. It was made in a star, set in a planet’s core and brought here in a shower of fire. It also arrived in your life the same week people flew around the Moon for the first time in over half a century.

Specimen record

Name	Campo del Cielo (“Field of Heaven”)
Found	Gran Chaco, Chaco Province, Argentina
Classification	Iron, IAB (coarse octahedrite)
Fell to Earth	around 2,500 BC
First documented	1576
Age of material	~4.5 billion years
Mass of this piece	39 grammes
Made of	iron, nickel, cobalt, a trace of iridium

It spent four billion years out in space…

…and now it’s in a small glass box.

“We are made of star stuff.” – Carl Sagan

Pass it on

Next time someone picks it up and calls it a cool rock, you can tell them what it is: a piece of the core of a planet that was destroyed before the Earth formed. It fell in a shower of fire when the pyramids were still quite new. Nobody can make the crystal pattern inside it, because that pattern only grows when metal cools by about a degree every million years, deep inside a planet. Then watch them nearly drop it when they feel how heavy it is. This one’s yours now.