  IRTF/SpeX observations of Pluto's near-infrared reflectance spectrum during
2013 show vibrational absorption features of CO and N$_2$ ices at 1.58 and 2.15
{\mu}m, respectively, that are weaker than had been observed during the
preceding decade. To reconcile declining volatile ice absorptions with a lack
of decline in Pluto's atmospheric pressure, we suggest these ices could be
getting harder to see because of increasing scattering by small CH$_4$
crystals, rather than because they are disappearing from the observed
hemisphere.
