Spectral pair with a high CSSI of 0.34. The compacted off-swirl spectrum with a filling factor of 0.144 can almost perfectly describe and recreate the on-swirl spectrum. The space weathered on-swirl spectrum with a respective npFe 1.217 wt % and mpFe 0.17 wt% does not recreate the off-swirl spectrum accurately. The position of the spectral pair is marked in Fig. 1. The on-swirl location is: 10.198 ° N, 304.152 ° E and the off-swirl location is: 10.302° N, 303.945° E. The root mean squared errors (RMSE) of the modeled with respect to the measured spectra are listed in the corresponding captions.