The Homogeneus Surface Of 2003 EL61, A Snowball In The TNb

PINILLA-ALONSO, NOEMI; BRUNETTO, R.; LICANDRO, J.; GIL-HUTTON, R.; CAMPINS, H.

Florida, Estados Unidos

Congreso; 39th Meeting of the AAS Division for Planetary Sciences; 2007

Division of Planetary Sciences, American Astronomical Society

We present a detailed study on the surface composition of 2003 EL61. We use visible and near-infrared spectra of 2003 EL61 obtained for more than three consecutive hours covering more than 80% of the rotational period, in the Telescopio Nazionale Galileo and William Herschel Telescope, sited in the Observatorio del Roque de los Muchachos. First we show that our observations do not evidence large spectral variations, neither concerning the spectral gradient in the visible nor the depth of water ice bands what agrees with Rabinowitz et al 2006. suggestion of an homogeneus composition of the surface. We show later a detailed set of fitings to the spectra using Hapke theory, our models show that: - It is not possible to reproduce the spectrum of 2003El61 with simple amorphous or crystalline water ice or an spatial mixture of both. - This spectrum is compatible with an intimate mixture of crystalline and amorphous water ice in the proportion of about 1:1 what is consistent with the scenario of an homogeneus body. - We explore the possibility of reproducing this spectrum with a configuration of two layers of water ice with different proportion of crystalline and amorphous ice, what is consistent with the effects of ion irradiation on the surface of TNOs. - Finally we investigate the presence of other minor components such as poly-HCN or hydrated silicates and find that none of them helps us to improve the fit quality. Furthermore, more than a 5% of each of these components in the fittings is enough to produce non-neutral slopes in the visible range, which is in complete disagreement with the observations.