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Cubical model of Earth's core discovered

tech reviews Updated: Feb 11, 2008 13:54 IST
PTI
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Rubik's Cube in the centre of our planet? Well, a team of Swedish scientists claims to have found evidence to support this new model of Earth's core.

According to the researchers, this new discovery will entail a revaluation of the cooling off of the Earth and of the stability of its magnetic field as well as open new perspectives for understanding its past, present and future.

"We found that the body centred cubic structure of iron is the only structure that could correspond to the experimental observations," according to Prof Brje Johansson of Uppsala University.

It has long been known that the inner core of the Earth, a sphere consisting of a solid mass with a radius of about 1,200 km, is mainly made up of iron.

But, in this study, the team has found that elastic waves pass more rapidly through the Earth's core in directions parallel to our planet's axis of rotation than in directions parallel to Equator, a phenomenon not previously explained.

In fact, the researchers have shown simulations of how seismic waves are reproduced in iron under the conditions that prevail in Earth's core, revealing a difference of 12 per cent depending on their direction that suffices as an explanation for the puzzling observation.

First the trajectories of movement were calculated for several million atoms in strong interaction with each other. On this basis, the scientists were then able to determine that the progress of the sound waves was actually accurately described in the computer-generated model for iron under the conditions prevailing in the core of the Earth.

The Earth's heat balance, like its magnetic field, is dependent on the amount of heat that is stored in the inner core of the planet. These conditions, in turn, are dependent on the crystal structure of the iron in the inner core.

Previously these estimates were based on models deriving from hexagonal structure of iron in the inner core.

"This study opens new perspectives for our understanding of the Earth's past, present, and future," the 'ScienceDaily' quoted Natalia Skorodumova, another researcher at the Department of Physics and Materials Science, as saying.

In their studies, these researchers have used models based on the so-called density functional theory for which Walter Kohn was awarded the 1999 Nobel Prize. The calculations were carried out using the most powerful supercomputers in existence, in Stockholm and Linkping.

The body centred cubic-crystal structure forms a cube with atoms in each corner and a further atom in the middle of this cube. It's oriented in such a way that its great diagonal is directed along the Earth's axis of rotation, which makes it possible for the iron to evince sound propagations with the velocities observed. The results of the study have been published in the 'Science' journal.