Water Ice on the Satellite of Kuiper Belt Object 2003 EL61
  We have obtained a near infrared spectrum of the brightest satellite of the large Kuiper Belt Object, 2003 EL61. The spectrum has absorption features at 1.5 and 2.0 microns, indicating that water ice is present on the surface. We find that the satellite's absorption lines are much deeper than water ice features typically found on Kuiper Belt Objects. We argue that the unusual spectrum indicates that the satellite was likely formed by impact and not by capture. 
K.M Barkume, M.E. Brown, and E.L. Schaller