Trans-neptunian object (55636) 2002 TX, a fresh icy surface in the outer solar system

¹ Isaac Newton Group, PO Box 321, 38700 Santa Cruz de La Palma, Tenerife, Spain e-mail: licandro@ing.iac.es
² Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
³ Centro Galileo Galilei & Telescopio Nazionale Galileo, PO Box 565, 38700 Santa Cruz de La Palma, Tenerife, Spain

Received: 11 June 2004
Accepted: 3 May 2006

Abstract

Context.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.

Aims.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 ).

Methods.We report visible and near infrared spectra covering the 0.5–2.2 μm spectral range, obtained with the Italian 3.58 m Telescopio Nazionale Galileo at “El Roque de los Muchachos” Observatory (La Palma, Spain), and derive mineralogical information using multiple scattering models.

Results.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.