Ferrous oxide in Mercury's crust and mantle

Mercury has widespread plains deposits proposed to be volcanic in origin. In a Mariner 10 color-derived parameter image, sensitive to FeO and maturity, these volcanic plains have a value equivalent to, or slightly elevated above, the hemispheric average, thus implying FeO equivalent to, or slightly less than, the hemispheric average (∼3 wt% FeO). Since FeO has a solid/liquid distribution coefficient ∼1 during partial melting, we estimate the mantle of Mercury to have an FeO abundance equal to the lava flows. This is consistent with models that predict Mercury was assembled from planetesimals formed near the planet's current position. This new estimate of Mercury's bulk FeO (∼3 wt%) is consistent with data for the other terrestrial planets that suggest there was a radial gradient in FeO in the solar nebula.