The most unattainable part of Earth

By Mejs Hasan

Imagine that you want to explore a place that you simply can’t travel to.  You probably can relate that feeling with the current coronavirus quarantine. But there’s a group of scientists who struggle with this feeling even during normal times — because despite our best technological advances, the place they want to study remains unattainable. The object of their wanderlust? The inside of the Earth. Even though astronauts can visit space — even though we can climb to the top of Mt. Everest — even though we put a rover on Mars for crying out loud — we still are unable to penetrate very far beneath the surface of the Earth.

In school, we learn that the Earth is made up of three basic layers: the core in the very center, the mantle wrapped around that, and then the crust upon which we stand.

If we can mine mountains and drill deep wells surely we can blast our way to the center of the Earth?

Well, we have not.

We haven’t even drilled all the way through the topmost layer, the crust. The deepest hole humans have dug is in western Russia, just south of the icy waters of the Arctic sea. This hole dives almost 7.5 miles (or 12 kilometers) into the depths of the crust, but even this is only about one third of the distance to the mantle at that point.

So what’s a scientist to do when their study area is out of reach? Turns out it takes a lot of creativity and imagination. Let’s find out more.

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Here at Rice, the ExPeRT lab enables scientists recreate the inside of the Earth, all within a capsule that fits in the palm of your hand.

Sanath Aithala, who is part of the CLEVER Planets research group, inspects one such capsule. Sanath and his lab-mates have been running experiments on these capsules for months.

Inside the  capsules are tiny pinches of rock powder mixed together. These pinches are selected to represent the materials from deep inside the Earth. Though we’ve never been there, sometimes a rock from deep inside Earth will be shifted and shaken all the way to the surface. These rare rock samples are Sanath’s guide; they ensure that the pinches of rock powder in his capsule accurately represent rocks deep in the Earth. 

This experimental mixture is supposed to represent the Earth during its infancy, when there was no core/mantle/crust; just a ocean of fiery, burning magma.

And what Sanath wonders in his experiment is: how did we go from that early vicious magma world to the neatly organized planet with core/mantle/crust upon which we are able to live and breathe?

Let’s take a look as Sanath, and his lab-mate, Michael Lara, set up an experiment. The capsules with the rock powders are first hand-packed into a heavy metal donut. The metal donut, holding its bounty, gets placed into a large blue machine. Known as a piston cylinder apparatus, this blue machine squeezes the capsule in order to achieve the same pressure that early Earth experienced.

Once the experiment is complete, Sanath opens up his capsule to see what became of the mixed rock powders. Any guesses about what happens?

As it turns out, the mix of rock powders melts and then neatly separates. Heavier metals collapse into a shiny heart, and the rest spreads out in pool of glass and crystal. Remind you of anything?

If you guessed a tiny layered planet you are right! The results from the experiment is similar the way the core and mantle of the Earth separated long ago, with heavier metals sinking into the core. And what Sanath and his lab-mates aim to decipher is: when this separation happens, what happens to elements like nitrogen, carbon, and oxygen? The all-important brew of elements that we need to live?

Do they sink into the shiny metal heart? Or do they slide out into the surrounding glass pool? If, for example, all the oxygen got cooped up in the buried metal heart, then how did we get the amount of oxygen in the Earth’s crust needed for the evolution of life?

Where did all the rest of those important elements go when Earth transitioned from a fiery ball to a more orderly planet structure? That’s one of the questions that CLEVER Planets seeks to answer. It’s a long and structured process, but bit by bit, different scientists in different parts of the world are working collectively to put together the story of the origins of life on Earth.