New simulants for martian regolith: Controlling iron variability

Existing martian simulants are predominantly based on the chemistry of the average 'global' martian regolith as defined by data on chemical and mineralogical variability detected by orbiting spacecraft, surface rovers and landers. We have therefore developed new martian simulants based on the known composition of regolith from four different martian surface environments: an early basaltic terrain, a sulfur-rich regolith, a haematite-rich regolith and a contemporary Mars regolith. Simulants have been developed so that the Fe2+/Fe3+ ratios can be adjusted, if necessary, leading to the development of four standard simulants and four Fe-modified simulants. Characterisation of the simulants confirm that all but two (both sulfur-rich) are within 5 wt% of the martian chemistries that they were based on and, unlike previous simulants, they have Fe2+/Fe3+ ratios comparable to those found on Mars. Here we outline the design, production and characterisation of these new martian regolith simulants. These are to be used initially in experiments to study the potential habitability of martian environments in which Fe may be a key energy source.