2005ApJ...630L..93L

Eight low-resolution near-infrared spectra (0.8-2.4 µm) of 32522 Thereus were obtained on 2002 August 28 from 0:30 to 5:30 UT, covering more than half of its rotation period, with the 3.56 m Telescopio Nazionale Galileo (TNG) at El Roque de los Muchachos Observatory (ORM, Canary Islands, Spain). All the spectra are red, probably due to a mantle of organic materials resulting from long-term irradiation. During at least 1.5 hr, the spectra clearly present the typical water ice absorption bands at 1.5 and 2.0 µm indicative of an inhomogeneous surface with a major concentration of water ice in part of it. One possible scenario is that a collision destroyed part of the irradiation mantle and moved ice from below to the surface, part of the material being vaporized over the surface by the impact.