• Merlin, F.
• Guilbert, Aurélie
• Brunetto, R.
• Sarid, G.
• Fornasier, S.
• Delsanti, A.
• Alvarez-Candal, A.
• Barucci, A.
• De Bergh, C.

Abstract

Several near-infrared spectra of Centaur Chariklo have confirmed the presence of water ice on its surface (Brown et al., 1998, Brown & Koresko, 1998, Dotto et al., 2003). Indeed, absorption bands centered at 1.5 and 2.0 µm have been detected on four different spectra, with depths reaching 20%. No crystalline water ice band at 1.65 µm has been detected so far. We present data obtained in the framework of the new ESO Large Program on TNOs and Centaurs, in March 2007 and February 2008. Visible and near-infrared photometric and spectroscopic data were obtained simultaneously with three different instruments of the ESO/VLT facility (FORS, ISAAC and SINFONI). Both H+K spectra are very different from the previously published ones: they are indeed both featureless. We applied a spectral modeling on the 0.43-2.38 µm wavelength range: the best fit models -obtained with geographical mixtures of amorphous carbon, olivine, Triton and Titan tholins- do not include any water ice. We study the possibility for these various spectral behaviours to be due to temporal or spatial variations on Chariklo. We find that cometary activity is unlikely to be responsible for the observed variations, although we cannot definitively discard that explanation. Similarly, spatial variations cannot properly reproduce the variations seen on both spectroscopic and photometric data, although we cannot exclude the presence of different patches with varying compositions on the surface....

Topics

• impedance spectroscopy
• surface
• amorphous
• Carbon