Morphological, structural, and spectral characteristics of amorphous iron sulfates

Current or past brine hydrologic activity on Mars may provide suitable conditions for the formation of amorphous ferric sulfates. Once formed, these phases would likely be stable under current Martian conditions, particularly at low‐ to mid‐latitudes. Therefore, we consider amorphous iron sulfates (AIS) as possible components of Martian surface materials. Laboratory AIS were created through multiple synthesis routes and characterized with total X‐ray scattering, thermogravimetric analysis, scanning electron microscopy, visible/near‐infrared (VNIR), thermal infrared (TIR), and Mössbauer techniques. We synthesized amorphous ferric sulfates (Fe(III)2(SO4)3 · ~ 6–8H2O) from sulfate‐saturated fluids via vacuum dehydration or exposure to low relative humidity (