Iron in Earth’s core is weaker than expected

New Scientist : Earth’s molten outer core and solid inner core are both predominantly made of iron. Their properties are, understandably, difficult to measure directly. Arianna Gleason of Stanford University in California and her colleagues attempted to reproduce some of the conditions in the inner core by subjecting iron foil to a pressure of 200 GPa. Although equivalent to 2 million atmospheres, that pressure is still significantly lower than the actual pressure experienced by Earth’s core, which is believed to be at least 330 GPa. Gleason’s team measured the iron’s density and the speed of deformation waves through the material. From that they were able to calculate the iron’s strength and used that value to extrapolate the strength of the iron in the inner core. The resulting calculations gave a strength value that was lower than expected under those pressures and temperatures. Gleason says that the lower strength of the material may allow the iron grains to align, which may explain why seismic waves that pass through the inner core move 3% faster when traveling pole to pole than they do along the equatorial plane.