Figure 11

Spectral ratio. Here we show two spectral ratios of Hetpet Regio: in black, one between the area VIMS sees as changed and a nearby, unchanged area, both on T76; and in red, a ratio between the changed area from T76 and the same area back on T61. The areas between the spectral limits of Titan’s infrared spectral atmospheric windows are indicated in white. The ratio between the spectral windows (in grey) is meaningless because the surface cannot be detected from orbit at those wavelengths. This ratio shows that the brightening occurred at all wavelengths where the surface is visible to VIMS (though the displayed ratio is contaminated by atmospheric scattering at the shortest-wavelength windows).