A Consolidated Mössbauer Spectrum for Undisturbed Soils from Gusev Crater, Mars

The mineralogical and elemental composition of Martian soil provides valuable insights into chemical and physical weathering processes on the Red planet's surface. Data from the Mars Exploration Rovers suggest that bright dust deposits on opposite sides of the planet belong to a global unit rather than being influenced by local rock compositions. Dark soil deposits at both sites exhibit similar basaltic mineralogy, indicating either a global component or comparable local rock sources. The presence of olivine suggests limited aqueous alteration, while elevated nickel concentrations imply that the upper soil layers may contain up to one percent meteoritic material, reinforcing the overall homogeneity of Martian surface soil. Physical weathering, driven by extreme temperature fluctuations and strong winds, plays a significant role in soil formation, with global storms facilitating its uniform distribution. Mossbauer analyses from MIMOS II data collected on Mars provided breakthrough insights into iron mineralogy of the planet’s surface. Resulting from limited measurement time, science operations were divided among multiple instruments, restricting the detection of minor Fe-bearing mineral phases (below 5% WSA). MIMOS II records Mossbauer spectra at 10 K intervals, and to enhance signal to noise ratios, spectra from different intervals were combined, when applicable. For instance, temperature variations between 190 K and 260 K in basaltic samples do not significantly impact the spectra, allowing data from all intervals to be integrated.By combining MIMOS II data from various soil samples and over different temperature ranges, a consolidated M\"ossbauer spectrum for Martian soil at Gusev Crater is proposed, aiming to identify potential minor Fe-bearing mineral phases on the planet's surface. This work combines Mossbauer measurements conducted on undisturbed soils within 10 k and all measurements conducted by Spirit until sOl 2062.