X‐Ray Amorphous Material Formed Through Clay‐Brine Interaction on the Utopia Planitia, Mars

Abstract X‐ray amorphous materials (XAMs) are observed to be prevalent on the Martian surface, though their formation mechanisms remain unclear. In this study, we utilize mineralogical data from Zhurong, China's first Mars rover, to provide a deeper understanding of this issue. The shortwave infrared spectra revealed signals of Al‐OH near 2.20 μm, and signals of the vibrations of water molecules and hydroxyl in sulfates around 1.95 μm. These findings suggest the presence of clay and possibly Al‐bearing XAM along with sulfate. Comparative studies of analog samples from the western Qaidam Basin and brine soaking experiments present a mineral evolution model for the formation of XAM through clay‐brine interactions. In this model, evaporites crystallize within the interlayers of clay minerals, impacting their structural stability. Structural ions may be continuously released due to the attack of H + ions, forming XAMs as liquid water rapidly evaporates. These findings indicate that clay‐brine interactions could extend beyond the Martian southern hemisphere, highlighting the importance of carefully considering the ancient hydrologic cycle and the resulting post‐depositional impacts on surface minerals in salt‐weathering environments on Mars.