Quantitative Mineral Analysis of Zhurong Landing Area Based on In-situ SWIR Spectral Unmixing

In May 2021, China’s first Mars exploration mission, Tianwen-1, successfully landed its rover, Zhurong, on the southern part of Utopia Planitia, an Amazonian geological unit on Mars. Zhurong is equipped with a Shortwave Infrared Spectrometer (SWIR) capable of capturing spectra in the 0.85–2.4 μm range from the surface of landing area. Previous studies of the SWIR spectra have primarily been qualitative, suggesting evidence of hydrated activities in the region. These findings indicate that water activity during the Amazonian era may have been more active than previously thought. The SWIR spectra obtained by Zhurong are mixed spectra comprising signals from multiple components. Through further quantitative analysis, the mineral abundances in the landing site can be determined, providing better constraints on the intensity of hydrated processes and enhancing our understanding of Amazonian hydrology on Mars. This study selected olivine, high-calcium pyroxene, low-calcium pyroxene, plagioclase, and glass as common Martian spectral endmembers, and hydrated minerals such as gypsum as characteristic endmembers. Using the Hapke radiative transfer model combined with the Cascading Adaptive Transitional Metropolis In Parallel (CATMP) algorithm, we performed linear spectral unmixing of the SWIR data. The analysis retrieved the surface mineral abundances, grain sizes, and associated uncertainties. The spectral unmixing results across the 2-km traversed area of the landing area were highly consistent, showing a dominance of primary minerals such as olivine, with a relatively low abundance of hydrated minerals. This suggests limited chemical weathering processes in the region. Our unmixing results enable more precise quantitative characterization of surface hydration activity, contributing to a deeper understanding of the Amazonian climate and hydrological evolution on Mars.