Structure – What are planets made of?

If you want to learn about the structure of planets, the best place to start is with the one you’re standing on!


We can check out what other planets are made of by looking at our own – right under our feet!

Scientists believe all the planets are made of the same stuff, give or take a little. The reason why they believe this is because the meteorites that have landed on Earth have mostly been made of the exact same compounds you can find inside the Earth, which suggests the structure of other planets is pretty similar to own.

You can see bits of meteorites in museums around the world and they do look just like regular rocks!

So what is the Earth’s structure?


The first layer is the crust.

On Earth, the crust is sixty kilometres thick.

Some planets have thick crusts, others have thin ones.


The next layer is the mantle – a big gloopy mass of molten rock!

It’s nearly three thousand kilometres thick.

Where it pushes against the crust you get moving layers called tectonic plates. These moving tectonic plates are what causes volcanoes up on the surface.

If you watch a video of a volcano erupting, you’ll see fiery molten rock has come from the mantle.

We call it lava when it erupts out of volcanoes but under the crust it’s called magma.


At the very centre is the core.

We think all planets have a core.

Some will be big, others much smaller but scientists believe they’re probably all made of similar stuff.

Click here to explore more from Deep Space High: Earth Watch