The materials from which the bodies in the outer solar system accreted were rich in volatile ices; Pluto and Neptune’s satellite Triton have long been known to be covered in methane, molecular nitrogen, and carbon monoxide ices that sublime and form the tenuous atmospheres seen surrounding these bodies. Until recently these volatile-rich surfaces appeared to be unique in the outer solar system and non detection of the signatures associated with volatiles had been claimed for the objects in the trans-Neptunian belt. The recent discovery of methane on the surfaces of the dwarf planets Eris and Make-make have shown that these objects are part of a new class of volatile-rich bodies in the outer solar system. Moreover, models of the retention of volatiles by these big trans-Neptunian objects suggest that not only methane but nitrogen and carbon monoxide should be present. This fact has direct implications for the presence of an atmosphere associated with them. With all of these ingredients, we were expecting a promising scenario where we should be able to detect features of volatile ices on the spectra of Eris and Make-make easily. But the observations reveal a more tricky reality and non clear detection of these ices has been claimed in the 5 years that have past from their discovery. Where are the volatiles on these objects? Are the models correct? Is there any determinant factor that we have not taken into account? Using new high-quality data obtained during the commissioning of XSHOOTER@VLT, an echelle spectrograph that covers in a single exposure the spectral range from the UV to the K' band, I will try to shed light into this intriguing question. Another amazing case is the presence of carbon monoxide on the surface of Iapetus and other Satellites of Saturn. The spectral absorption band of pure carbon dioxide in a solid state, nominally centered at 4.2675 µm was discovered in the spectra of some Saturn’s satellites by the Visible-Infrared Mapping Spectrometer (VIMS) aboard the Cassini orbiting spacecraft. This detection is surprising because its long-term instability in pure condensed form at the mean surface temperatures of these satellite system indicates that special conditions of its formation and retention exist. I will show a collection of observations from a fly-by to Iapetus in September 2007 and making use of clustering techniques I will study the presence of CO2 ice on the surface of this unique satellite. I will interpret the results in the frame of the theories about the origin and evolution of CO2 in the surface of Iapetus.