Hydrated minerals provide direct indications of the early Martian water environment. The various clay minerals and evaporite salts found to date are mainly exposed in the ancient southern highlands of Mars. While it is believed that the area of the northern lowlands could have hosted a global ocean in the past, its surface is covered with a layer of spectrally nonabsorbing materials, and orbital hyperspectral remote sensing has found only sparse evidence for the presence of water. China's first Mars exploration mission, Tianwen-1, landed in the putative ancient shoreline zone of the northern lowlands of Mars. Its rover, Zhurong, conducted high-spatial-resolution reconnaissance to reveal the geological and environmental evolution of this region. Owing to frequent dust storms, not only is the Martian surface covered with dust, but also the spectral calibration panels on the rover are affected by dust coverage. Data from the shortwave infrared (SWIR) spectrometer onboard the rover are also affected by other environmental factors such as instrumental temperature changes and atmospheric carbon dioxide absorption. This study recalibrated the in situ SWIR data to minimize the impact of the above factors. The recalibrated spectral data show that the reflectance of the landing area falls within the normal range of Martian soil, and confirm the presence of several important absorption peaks. The absorption characteristics indicate the presence of polyhydrated sulfates, gypsum, and hydrated silicates in the surface materials along the rover track, with sulfate content of <27-39 wt.%. Our results further confirm past activity of liquid water in the Zhurong rover landing area, providing mineralogical evidence supporting hypotheses related to underground water or an ancient shoreline.
