Amorphous iron sulfate pentahydrate has been identified as one of the iron sulfates found on the Martian surface during the Spirit and Opportunity Rover missions in recent years. The existence of amorphous iron sulfate (AFS) phases resonates with amorphous calcium carbonate and phosphate phases which are known to play important roles in biomineralisation, although sulfates do not. Our project is to carry out a structural characterisation of AFS using experimental probes of X-ray and neutron diffraction, and X-ray absorption spectroscopy, and combined with EPSR modelling. The amorphous pentahydrate can be heated up to 300 °C to produce AFS in which the water content is reduced to approximately Fe2(SO4)3¿0.5H2O and SANDALS is a very suitable diffractometer to use for such a material. In addition, for comparison we will study a sample of AFS produced by ball milling.