Spectroscopy of Pluto and Triton at 3-4 Microns: Possible Evidence for Wide Distribution of Nonvolatile Solids

We present new albedo spectra of Triton and Pluto-Charon, covering the 2.8–4.1 μm wavelength range at a spectral resolution of ~60. The new data reveal three strong CH4 ice absorption bands, as well as additional absorption around 2.9 and 4.1 μm in the spectra of both bodies, which we tentatively attribute to widely distributed H2O ice, along with CO2 and/or SO2 ices. Since these species are nonvolatile at typical Triton and Pluto surface temperatures, widespread distribution of any of them in volatile-rich regions challenges current understanding of the surfaces of Pluto and Triton, in which more volatile, mobile ices are thought to be segregated from less volatile species. Our data suggest that small, nonvolatile ice particles on Triton and Pluto may be undergoing redistribution by aeolian transport in seasonal sublimation winds.