Scientists have discovered that one of the most abundant materials deep inside the Earth can change how it conducts electricity without changing its structure. This discovery could forever change how we understand the Earth's interior and impacts our planet's magnetic field - something scientists have never been able to completely explain.
Ronald Cohen of Carnegie's Geophysical Laboratory co-authored the study and found when extreme heat and pressure were applied to the iron oxide (the second-most abundant material in the Earth's lower mantle), it changed how it conducted electricity without the metal changing its structure. Normally, a change in conductivity would mean a change in atomic or subatomic structure, too.
"The fact that one mineral has properties that differ so completely - depending on its composition and where it is within the Earth - is a major discovery," said Russell Hemley, director of the Geophysical Laboratory.
By putting the iron oxide in conditions that are similar to the Earth's core-mantle boundary (1.4 million times atmospheric pressure at sea level and temperatures up to 2,200 C), Cohen and his team saw first-hand that the metal can change from being an insulator to a conductor depending on the heat and pressure it's exposed to.
"At high temperatures, the atoms in iron oxide crystals are arranged with the same structure as common table salt," Cohen said. "Just like the table salt, iron oxide at ambient conditions is a good insulator - it does not conduct electricity."
"Our new results show, instead, that iron oxide metallised without any change in structure and that combined temperatures and pressure are required. Furthermore, our theory shows that the way the electrons behave to make it metallic is different from other materials that become metallic."