2006A&A...457..329L

The knowledge of the physical properties of the population of known large trans-Neptunian objects (TNOs) is a key issue in understanding the origin and evolution of the Solar System. In particular, the knowledge of their surface composition helps to understand the original composition of the TNOs and the processes that affect their surfaces during their life. We studied the surface composition of bright TNO 2002 TX₃₀₀, an object with a few hundred kilometer diameter (900-400 km if visual albedo is 0.08<p_V<0.4). We report visible and near infrared spectra covering the 0.5-2.2µm spectral range, obtained with the Italian 3.58m Telescopio Nazionale Galileo at ``El Roque de los Muchachos'' Observatory (La Palma, Spain), and derive mineralogical information using multiple scattering models. The spectrum of this large TNO is dominated by strong water ice absorption bands in the near-infrared and also presents a neutral to blue slope in the whole observed range. Models suggest that the surface of 2002 TX₃₀₀ is fresh, composed of a large fraction of large water ice particles and dark materials (may be carbon and/or silicates) and a very low fraction of highly processed organic materials (tholins). The spectrum of 2002 TX₃₀₀ is very similar to that of Pluto's satellite Charon. This can indicate that there is an ubiquitous mechanism that keeps water ice as the principal component of the outher layer of the surface of some large TNOs.