ESF researchers journey to the Earth's core
Researchers from the European Science Foundation (ESF) have overturned conventional thinking about what really goes on 3,000 kilometres beneath our feet. Until now, scientists have believed that the Earth's core is made up of iron atoms packed together, in fact the picture might not be quite so straightforward. Given the great pressures and temperatures found at the Earth's centre (3.5 millibar and 7000 °Kelvin), which make it impossible to recreate these conditions in a laboratory, all our knowledge comes from extrapolation. This method involves observing the way seismic waves travel through the core. As a result, scientists know that the core is mostly made up of iron, but that it must also contain light impurities such as oxygen, silicon, sulphur, hydrogen, magnesium and nickel (between 5% and 15%). 'It was assumed that the alloy elements were not very important for the structural and elastic properties of the core,' says Igor Abrikosov, a theoretical physicist at Linköping University in Sweden. Based on these experimental and theoretical studies, a 'standard model' was established, showing iron atoms placed in a close hexagonal formation resembling a honeycomb. 'At moderate pressures other structures have some magnetism and they turn out to have lower stability,' explains Dr Abrikosov. In recent years, computer developments have enabled scientists to develop more sophisticated models. 'Expertise has been developed in 'Ab initio' (first principles) calculations and we are able to do higher quality extrapolations to understand core conditions,' Dr Abrikosov adds. Using these powerful new simulations, researchers have been able to include elements such as nickel and magnesium in their calculations and so have reached remarkable new conclusions. 'At high pressures the magnetism is squeezed out of the other structures and they all have similar stability,' says Dr Abrikosov, who has revealed that 'face centred cubic' and 'body centred cubic' structures cannot be ruled out and that all of these structures are energetically possible. 'The standard model has been killed,' Dr Abrikosov concludes. As the Earth's core produces our magnetic field, protecting us from being bombarded by dangerous cosmic rays, our understanding of it is not only important, but essential to our survival. Furthermore, increased knowledge of the Earth's core could also help us to develop technologies such as satellites, which rely on the magnetic field for staying in place.