Rocks are a mixture of different minerals, and minerals are the building blocks of rocks and everything that makes up a planet!
Different combinations make different types of rock.
The building blocks of the minerals are called elements, and nearly all the minerals that make up the earth come from just eight elements.
The four most common elements that make up the minerals in the rocks here on earth are oxygen, iron, aluminium and silicon.
Oxygen
We think of oxygen as being something in the air we breathe but itβs under our feet too!
Nearly half of all the minerals in the earthβs crust contain oxides – thatβs a form of oxygen.
You might think it’s strangeΒ that weβre breathing in the same stuffΒ you might find in a planet a billion miles away!
Iron
IronΒ makes up the core at the centre of the Earth.
Think about that next time youβre shutting your iron garden gate!
Silicon
Sand is also linked to the planets.
Sand is made of compounds containing silicon – something thatβs very common in the universe.
You find silicon in the Sun and stars, and in some asteroids too.
Nearly a quarter of the earthβs crust is made of silicon compound and we know that the planets near our Sun have lots of silicon compounds too.
Planets that are further from the SunΒ tend to have fewer mineral composites in common with planets likeΒ Earth which are nearer.
They are often more gassy, which scientists think happens because gasses get blown further by the solar winds.