1,3Haoan Yin, 1,2Hong Tang, 1,2Xiongyao Li, 1,2Wen Yu, 1Chuanjiao Zhou, 1Tian Zhang, 1Erbin Shi
Icarus (in Press) Link to Article [DOI: 10.1016/j.icarus.2026.117367]
1Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
2CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
3University of Chinese Academy of Sciences, Beijing 100049, China
Copyright Elsevier
Phyllosilicates and hydrated sulfates record aqueous activity on ancient Mars and may participate in present–day atmosphere–regolith water vapor exchange. However, their temperature–dependent spectral behavior has rarely been compared under consistent conditions, limiting discrimination between intrinsic thermal effects and adsorbed water loss. We measured diffuse reflectance infrared spectra of kaolinite, montmorillonite, gypsum, and jarosite from −90 to 30 °C and analyzed H2O/OH band positions, full widths at half maximum, and areas. Band positions remained generally stable in kaolinite, montmorillonite, and jarosite, whereas gypsum hydration bands shifted toward shorter wavelengths during warming. The ~2.75 μm feature of montmorillonite and ~ 3 μm feature of kaolinite narrowed and decreased in area, indicating adsorbed water loss. In contrast, the ~2.9–3 μm features of gypsum and jarosite broadened and increased in area, reflecting changes in molecular vibrations and hydrogen bonding. These mineral–specific responses distinguish adsorbed water exchange from intrinsic thermal effects, improve interpretation of orbital and in situ spectra, and clarify temperature–driven water vapor exchange mechanisms relevant to present-day Martian habitability.
