It has baffled scientists for decades - exactly what is the mystery 'third element' at the Earth's core?
Now, a team has the answer - and says its silicon according to Daily mail.
Researchers have been searching to solve the mystery at the centre of our planet for decades after discovering there is something other than iron and nickel there
Japanese scientists believe they have established the identity of a 'missing element' within the Earth's core.
Lead researcher Eiji Ohtani said: 'We believe that silicon is a major element - about 5% [of the Earth's inner core] by weight could be silicon dissolved into the iron-nickel alloys.'
'We measured the sound velocity of iron alloy compounds at high pressure and temperature relevant to the Earth’s core,' the researchers wrote in their presentation.
Eiji Ohtani and his team created alloys of iron and nickel and mixed them with silicon for the experiment, before subjecting them to the immense pressures and temperatures believed to exist in the inner core.
They found the mix matched what was seen in the Earth's interior with seismic data.
However, Professor Ohtani said more work was needed to confirm the presence of silicon and that it did not rule out the presence of other elements.
The innermost part of Earth is thought to be a solid ball with a radius of roughly 1,200km (745 miles).
Too study it, researchers analyse how seismic waves pass through the region to tell them something of its make-up.
Previous studies have shown it is mainly composed of iron, which makes up an estimated 85% of its weight, and nickel, which accounts for about 10% of the core.
However, the final 5% has baffled them until now.