Englacial authigenesis in deep Antarctic ice: implications for Martian dust oxidation

The discovery of englacial authigenesis has the potential to reshape our interpretation of insoluble dust records in ice cores and our understanding of planetary ice-bearing deposits on Mars. Mineralogical changes in deep ice involve iron mobilization and transformation driven by the circulation of acidic fluids within the ice matrix, leading to the authigenic formation of jarosite. Here we show that englacial authigenesis is documented across different Antarctic deep ice cores and involves the formation of mineral phases such as goethite/lepidocrocite and hematite/maghemite, in addition to jarosite. The coexistence of these phases reflects micron-scale variability in pH and water activity within the englacial brine network. Englacial authigenesis introduces biases in bulk mineralogical proxies used to reconstruct dust source conditions, and provides a grounded explanation for the anomalously high dust magnetization observed in deep Antarctic ice. We further propose that the repeated burial of dust within planetary ice reservoirs, as expected on Mars over orbital timescales, represents a viable mechanism for the oxidation, aggregation and magnetic activation of Martian airborne dust, without requiring prolonged warm and wet surface conditions.