Methanol on Enceladus

Near infrared spectra of the surface of Enceladus returned by Cassini show the presence of an absorption feature at 3.53 μm, ascribed by Brown et al. (2006) to “short chain organics,” and by Newman et al. (2007) to hydrogen peroxide. We assign this feature tentatively to methanol. Variations in the peak position of the feature suggest that methanol in the “tiger stripes” region may be segregated from the water ice, and not homogeneously distributed in the ice matrix. The photolytic destruction of methanol implies that methane or methanol itself must be continually deposited on the surface. On Enceladus, methanol may be generated photochemically from a mixed methane/water ice, or deposited from the plume itself. The variation in the concentration of methanol over the surface could be used to distinguish between these two processes.