Earth’s mantle is far more oxidized than its building blocks. The oxidation of the mantle has a large effect on our planet’s habitability, as it sets the necessary precondition for the formation of an oxygen-rich atmosphere to support life. Mantle oxidation may have occurred during the “magma ocean” stage of Earth’s history, through iron disproportionation (3FeO ⇔ Fe + Fe₂O₃) in molten silicate. However, experiments at relevant pressure and temperature conditions are lacking to test this hypothesis. Here, we present new data from laser-heating diamond-anvil cell experiments in combination with X-ray Diffraction (XRD), Synchrotron Mössbauer spectroscopy (in situ and recovery), and analyses of recovered samples using the focused ion beam (FIB), scanning electron microscopy (SEM), and transition electron microscopy (TEM). Preliminary data suggest spin crossover in pyrolite glass and considerable disproportionation in pyrolite melt at moderate pressures. We will discuss the implications for the role of self-redox reaction in oxidizing the mantle and facilitating Earth’s evolution into an inhabited world.

Earth, Planet