High resolution Raman microscopy and imaging to propose a jarosite formation process in the MIL 090030 Martian...

Jarosite is an iron sulphate that has been found in different Martian meteorites as well as on the Martian surface. In most of the cases, this mineral was detected related to olivine grains. In this work the Miller Range 090,030 Martian Nakhlite (MIL 090030) has been analysed by high resolution Raman microscopy and imaging in areas where jarosite was present. In the case of MIL 090030 meteorite, jarosite was found beside olivine and rasvumite (KFe₂S₃). There are different hypotheses for the formation of jarosite on Martian related samples, but so far, no explanation for the formation of jarosite from olivine and rasvumite has been proposed. In this study, such hypothesis for this transformation is proposed based on the obtained Raman image results where jarosite appears surrounding primary compounds. The proposed alteration mechanism consists on the formation of magnetite and jarosite from rasvumite and Fe-rich olivine, with the subsequent enrichment of olivine in forsterite and the formation of quartz. With the ions released in the different chemical reactions, jarosite can precipitate as a stable phase. Taking this into account, the jarosite detected in the MIL 090030 Martian Meteorite can be considered as an original Martian mineral.