Water ice is ubiquitous in the outer Solar System: it was firmly detected on about ten objects (Kuiper Belt Objects -KBOs and Centaurs), thanks to the wide absorption bands which sign at 1.5 and 2.0 microns in reflectance spectra. In 2004, 50000 Quaoar was diagnosed with the 1.65 microns feature, which is characteristic of crystalline water ice (Jewitt and Luu 2004, Nature 432 p731). The presence of crystalline water ice at distances where the surface equilibrium temperature is predicted to be 50K was not expected. It implies that the ice was heated above 100K and is constantly replenished to balance the destruction caused by the high-energy particle flux.We searched the surface of water-bearing KBO (90482) Orcus for crystalline water ice. It was studied in near infrared spectroscopy (with GEMINI+NIRI in service mode on February 20-22 and March 1-3, 2005) but also in visible spectroscopy (with KECK+LRIS on April 9, 2005) to obtain a wider wavelength coverage of the surface properties. We emphasized H-band observations (about 3h in the 1.4-1.8 microns domain at a resolution R 350). In this paper we will present the results and discuss the presence of several molecular species in addition to crystalline water ice.
AAS/Division for Planetary Sciences Meeting Abstracts #38
- Pub Date:
- December 2006