Uniform oxygen fugacity of shergottite mantle sources and an oxidized martian lithosphere

Martian meteorites are the only available samples that can be directly measured to constrain geological evolution of Mars. It has been suggested oxygen fugacity (fO2) martian shergottite meteorites, which have low (∼7 wt.%) high-MgO (∼30 compositions, correlates with incompatible trace element enrichment (i.e., La/Yb), and 87Sr/86Sr, 143Nd/144Nd, 187Os/188Os 176Hf/177Hf at time crystallization. These relationships interpreted result from early magmatic processes segregating enriched more oxidized depleted reduced reservoirs in Here we use V-in-olivine oxybarometer fO2 shergottites dunitic chassignites. data, utilizing crystallizing silicate phases, range between −3.72 ± 0.07 −0.21 0.55 ΔFMQ (log units relative fayalite-magnetite-quartz buffer), no correlation or Nd isotope systematics. Previously employed oxybarometers later-formed multiple mineral show such correlations, likely differ they record effects late-stage processes. In contrast shergottites, chassignites relatively oxidized, +2.1 0.4 +2.2 0.5 ΔFMQ. The chassignites, along nakhlites, proposed sourced metasomatized lithospheric mantle, their high strengthens this model. new data implies mantle sources −2.1 1.8 This estimate indicates core Mars not redox equilibrium therefore oxidation following formation is required.