Left: Nineteen Umbriel spectra (black, labeled a–s) and 1σ uncertainties (gray error bars) that display 2.14 μm (purple markers), 2.2 μm (blue markers), 2.22 μm (green markers), and/or 2.24 μm (red markers) absorption features with both band depths and areas >2σ (Tables A2–A5). The subobserver longitude for each spectrum is also listed (Table 1). All spectra were normalized to unity between 1.74 and 1.77 μm and offset vertically for clarity. To make spectral features easier to identify, the data have been lightly smoothed using boxcar functions ranging from 4 pixels wide (IRTF/SpeX PRISM mode spectra), 8 to 12 pixels wide (IRTF/SpeX SXD mode spectra), and 16 pixels wide (3.5 m/TripleSpec spectra). Right: Modified simple cylindrical map projection of the Voyager 2/Imaging Science System image mosaic of Umbriel (NASA/JPL/Caltech/USGS). The subobserver longitude and latitude for all 33 spectra are indicated with filled circles that represent the center of the target disk. These observations were disk integrated and averaged over an entire hemisphere. The 19 spectra on the left are represented by colored circles (labeled a–s), with colors and band centers defined below the map. Spectra that display two bands are represented by two-color semicircles, spectra that display three bands are represented by three-color wedges, and spectra without band depth and area measurements >2σ are shown as black circles. The white arrow points to the bright annulus of material mantling the floor of Wunda crater. The candidate constituents listed below the map are shown in Figure 4 and discussed in further detail in Sections 3.4 and 4.2.