Absorption Spectra of Martian Dust Simulants

Understanding the Martian climate requires a detailed characterization of the optical properties of Martian dust as it is a ubiquitous component of the atmosphere. The continued improvement of Martian atmosphere observations motivates measurements of terrestrial simulants under controlled conditions to support field studies and computational modeling. This investigation demonstrates an in situ method to entrain and directly measure the absorption spectrum of six Martian dust simulants using photoacoustic spectroscopy. Measured size distributions and absorption cross sections (C-abs) are used in Mie theory calculations to retrieve the effective imaginary component of the refractive index (k(eff)) of each sample while constraining the real component to n = 1.5, the refractive index of silica. The weakly absorbing simulants have k(eff) values ranging between 0.002 and 0.03 at a wavelength of 500 nm that are correlated with the mass fraction of iron oxides.