NIR reflectance spectra of granular H2O ice, gypsum and ice-gypsum mixtures in martian conditions

In order to investigate the spectral behavior of ice–gypsum mixtures, we have acquired laboratory reflectance spectra of ice samples containing various volumetric proportions of gypsum. The ice was produced by condensation of liquid water on a cooled metal plate. It was then crushed to obtain grain sizes between 500 and 600 µm. These ice grains were homogenously mixed with an synthetic pure gypsum powder. The samples were then placed in a liquid nitrogen cryostat to reproduce the martian pressure and temperature conditions (7 mbar, 150 K) and their spectra were acquired with a Nicolet 5700 Fourier Transform Infrared Spectrometer.