Ferropericlase separated into compositionally different oxides in high-pressure laboratory tests. Calculations suggest that this behavior could create a more easily deformable layer deep inside some massive rocky planets. The peer-reviewed study combines mineral experiments with planetary modeling; its proposed changes to super-Earth interiors have not been observed inside an actual exoplanet.
A peer-reviewed laboratory and computational study found that ferropericlase, a magnesium-and-iron oxide common in Earth’s lower mantle, separates under extreme conditions. The products contained different proportions of the two metals. The change appeared near 200 GPa at high temperatures. Evidence from crystal structure and the recovered samples’ chemistry supported separation into iron-rich and magnesium-rich regions.[1]
The experiments covered conditions beyond those inside Earth. Most instances of separation occurred while the material remained below its melting boundary. Calculations also indicated that separation became more favorable as pressure rose. Earth’s mantle reaches about 135 GPa, below the pressure associated with this transformation. Its familiar mineral mixture therefore provides an incomplete guide to the deeper interiors of larger rocky worlds.[1]
For an Earth-like composition, models place pressures above 200 GPa at the mantle base of planets exceeding roughly 1.5 Earth masses. Researchers suggest the iron-rich material could sink and form a less viscous layer, changing heat transfer and mechanical coupling between mantle and core. That planetary layer is a model proposal rather than an observed exoplanet feature; remixing at still greater pressure remains unresolved.[1]
