During the experiment, the researchers took a virtual trip inside the Earth by reproducing the conditions of Earth’s mantle at the ESRF. They placed the sample of iron-bearing perovskite between the two diamond tips of a diamond-anvil cell and subjected them to pressures from 20 to 145 GPa. By using x-rays, they could extract information from the sample and its behaviour under those conditions.
It is generally assumed that heat from Earth’s core and mantle, due to the low thermal conductivity of the latter, is transferred to the outer part mainly by convection. The sample became more transparent to heat above 70 GPa (bottom third of the mantle) and almost completely transparent above 120 GPa (D? layer above the core-mantle boundary); this is more than one million times greater than atmospheric pressure. Increased transparency is the reason why these researchers suggest that in the deep Earth, radiation plays a larger role with respect to convection in transferring heat.