We derived ultraviolet refractive indices of Martian dust.
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These refractive indices do not vary much with wavelength.
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We performed retrievals using these indices at lower dust loading conditions.
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Our results produce optical depths consistent with independent derivations.
Abstract
We derived the ultraviolet complex refractive indices of Martian dust aerosols using data from the Mars year 34 global dust storm (GDS). We used data taken by the Imaging Ultraviolet Spectrograph (IUVS) instrument aboard the Mars Atmosphere and Volatile Evolution spacecraft and surface-based derivations of the column-integrated optical depth from the Mastcam instrument on Curiosity. We first created an explicit microphysical representation of dust to compute dust-scattering properties at wavelengths within IUVS’ spectral range for four dust particle-size distributions plausibly present during this GDS. We then used radiative-transfer techniques to iteratively retrieve the single-scattering albedo from IUVS data using the Mastcam-derived column-integrated optical depth as a constraint. We converted the dust single-scattering albedo into its refractive indices and report the refractive indices at the four particle-size distributions. We performed dust optical depth retrievals at another time period using several of these refractive indices and show that our preferred refractive indices produce optical depths which are consistent with optical depths derived from Mastcam data at similar times. These ultraviolet refractive indices will be particularly beneficial for future observational and theoretical studies of Martian dust.
