Scientists carrying out extreme boffinry into the makeup of the Earth's liquid core have announced that they are very puzzled to find it is not made of what they had thought it was.

The great bulk of the liquid outer core of the planet, of course, is made of molten iron. That's just as well for us and all life on Earth, as the spinning blob of superhot melted metal we all live on top of generates a tremendously powerful magnetic field which keeps off all the plasma storms and cosmic rays and suchlike deadly space radiation so that we aren't fried out of existence on a routine basis.

But theory suggests that there must also be some lighter elements mixed in to the liquid comprising the outer core, otherwise it wouldn't be the density it is. (This density can be measured by seismic observations.) Until now, scientists specialising in such matters had theorised that the light stuff mixed with the iron was most probably oxygen, which is the next most abundant stuff in the world (various still-lighter elements tending to escape into space).

But it seems this is not the case. Disappointingly perhaps, scientists have discovered this not by carrying out an exciting mole-cruiser expedition beneath the planetary crust, but by (comparatively) humdrum lab work.

“We can’t sample the core directly, so we have to learn about it through improved laboratory experiments combined with modeling and seismic data,” explains the Carnegie Institution’s Yingwei Fei.

Fei and his colleagues mixed up various alloys of iron and lighter materials and then subjected them to conditions of temperature and pressure similar to those seen in the outer core, then carried out seismic shockwave tests on them. It turned out that whatever the outer core is made of, it isn't an iron-oxygen mix.

“The research revealed a powerful way to decipher the identity of the light elements in the core. Further research should focus on the potential presence of elements such as silicon in the outer core,” says Fei.

Thus it turns out that actually silicon may be even more important than we at the Reg have always thought. The new discoveries have important implications for our understanding of how the Earth formed, and thus in turn how other planets - perhaps ones orbiting other stars - might form.

The new results are published this week in hefty boffinry mag Nature. ®