Low temperature optical constants of some hydrated sulfates relevant to planetary surfaces

We derive optical constants (n(λ) and k(λ)) from laboratory reflectance spectra acquired at visible to near‐infrared wavelengths for epsomite (MgSO4⋅7H2O), bloedite (Na2Mg(SO4)2⋅4H2O), and hexahydrite (MgSO4⋅6H2O) at both room temperature and 120 K. These hydrated sulfates are candidate surface compounds for outer solar system icy satellites such as Europa, Ganymede, and Callisto, as well as Mars. Our results permit quantitative abundance modeling of Galileo, Cassini‐Huygens, New Horizons, Mars Reconnaissance Orbiter, Mars Express, and future mission spacecraft observations leading to better interpretation of these objects' surface and interior geological processes and histories.