Dielectric constant estimation of the uppermost Basal Unit layer in the martian Boreales Scopuli region

► We determine the permittivity of the uppermost martian Basal Unit from SHARAD data. ► The inversion is based on subsurface to surface echo power ratio. ► The inversion uses data selected in terms of pulse width and two-way travel time. ► We obtain a permittivity distribution peaked at 5-6. ► Estimated dust content in the uppermost Basal Unit layer exceeds 65%.