Earth’s core contains lots of sulphur

New research shows that Earth’s core contains vast amounts of sulphur – 90% of our planet’s sulphur – equivalent to 10% of the mass of the moon.

New research confirms that Earth’s core contains vast amounts of sulphur, estimated to be up to 8.5 x 10^18 tons. That’s about 10 times the amount of sulphur in the rest of the Earth, and for comparison, around 10% of the total mass of the moon.

The new study was reported in the journal, Geochemical Perspectives Letters on June 16, 2015.

Enjoying EarthSky? Sign up for our free daily newsletter today!

The Earth’s core begins 2,900 km (1,800 miles) beneath our feet, so it is impossible to investigate directly. However, an international group of researchers have been able to develop indirect geochemical methods to show core composition.

For a long time it has been known that the Earth’s core is too light to be made only of iron and nickel, and it had been assumed that the core contained other lighter elements, such as sulphur, silicon, oxygen and carbon. However, given the depth of the core, this has been impossible to confirm directly.

But, say researchers, a cataclysmic event in the distant past – when the Earth collided with a large, planet-size body, tearing off the part which became our moon – left a fingerprint, which has been used to confirm the core content.

The researchers believe that the impact of the collision melted the Earth’s mantle, allowing a sulphur-rich liquid to form in Earth’s mantle, the vast middle layer between the core and the crust. Some was probably lost into space, but some remained and sunk into the core.

The key to confirming this lay in measuring the isotope ratios of elements (isotopes are atoms of the same element with slightly different masses) in the mantle, and comparing these to certain meteorites, which are believed to be the best match to the Earth’s original composition.

Paul Savage, of the Department of Earth Sciences, Durham University, UK, is the lead researcher. Savage said:

We estimate that the quantity of sulphur in the core is vast, around 8.5 x 10^18 tons, which to give an idea of scale, is around 10% of the mass of the moon. In addition, the work adds weight to the theory that the moon was formed via a collision between the Earth and another body.

In a way, we can also say that we have life imitating art. For millennia, tales have been told of the underworld being awash with fire and brimstone. Now at least, we can be sure of the brimstone.

Bottom line: A study in the June 16, 2015 issue of Geochemical Perspectives Letters confirms that the Earth’s core contains vast amounts of sulphur, estimated to be up to 8.5 x 10^18 tons.

Read more about the study from the European Association of Geochemistry

Eleanor Imster