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M.A. Barucci, F. Merlin (LESIA, Observatoire de Paris), E. Dotto (INAF-Osservatorio Astronomico di Roma)
New observations on NIR have been obtained on the Centaur 32532 Thereus and on the Plutino 47171 (1999 TC36) at 8m-Very Large Telescope (VLT, ESO-Cerro Paranal) by ISAAC instrument. Studies on surface composition at different rotational phases are carried out by modeling the different spectra to interpret the possible evolution of these objects.
Several spectra obtained at different hemispheres show a homogeneous surface for the transneptunian 47171 confirming the previous model (Dotto et al. 2003, Icarus 162; 418) composed of 57% Titan tholins, 25% ice tholins and 10% amorphous carbon assuming an albedo of 0.13 at 0.55 mm.
The spectra obtained for the Centaur 32532 compared with those obtained by Barucci et al., 2002 (A&A, 392, 335) evidence a clear heterogeneity of the surface. The new spectra have been interpreted by geographical mixture model of 13% Titan tholin, 75% amorphous carbon, 5% water ice and 7% olivine assuming an albedo of 0.11 at 0.55 mm. The heterogeneity is evident with a clear presence of water ice on a portion of the surface.
The state of art on compositional properties of TNOs and Centaurs is presented as well as the summary of their known surface heterogeneity.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.