(a) The real component of the effective optical constants, n, as a function of wavenumber from a 2% HDO and 98% H₂O sample at 80 K. (b) The imaginary component of the effective optical constants, k, for the same sample, and the interpolation to separate the HDO band from the H₂O band. (c) Theoretical 100% HDO k-values derived by multiplying the baseline-subtracted k-values in Figure 5(b) by 50. We used these values as an endmember for our Hapke modeling, keeping in mind that it will only be valid for samples with low HDO concentrations (see the main text).