Organic-Assisted Synthesis and Spectroscopic Identification of Magnesite–Siderite Solid Solutions in Jezero Crater, Mars

The identification of siderite–magnesite solid solution in Jezero and Gale craters on Mars is of great significance for understanding the characteristics of habitable environments on Mars. However, the specific phases of the siderite–magnesite solid solution have not yet been accurately constrained, which partially impeded our understanding of the geological and geochemical process under which carbonates formed in the Jezero and Gale craters. In this study, a series of siderite–magnesite solid solution were synthesized by hydrothermal method in the laboratory. The X-ray diffraction (XRD) was used to checked the purity and homogenous of synthesized magnesite - siderite solid solutions and help to magnesite–siderite solid solutions in Gale Crater. The Raman spectra of synthesized samples were also measured and compared with the Raman spectra measured by SHERLOC and Time-Resolved Raman Spectroscopy (TRR) at multiple locations to accurately constrain the magnesite - siderite solid solutions in Jezero Crater. Linear relationships between main Raman peak positions (v1) of carbonate ion (CO_3^(2-)) and mole percent of magnesium ions (Mg#) were established (R2=0.996), and the Mg# (0.2-0.8) of magnesite–siderite solid solutions within Jezero crater was accurately identified. In addition, synthesis of siderite–magnesite solid solution was performed under hydrothermal conditions, where reduce organic compounds played a key role in mineral formation, would provide valuable experimental constraints on the geological and geochemical pathways of carbonate formation in Gale crater and Jezero crater.