Optical spectroscopy of the large kuiper belt objects 136472 (2005 FY9) and 136108 (2003 EL61)

We present high signal precision optical reflectance spectra of the large Kuiper Belt objects 2005 FY9 and 2003 EL61. The spectrum of 2005 FY9 exhibits strong CH₄ ice bands. A comparison between the spectrum and a Hapke model indicates that the CH₄ bands are shifted 3.25 ± 2.25 Å relative to pure CH₄ ice, suggesting the presence of another ice component on the surface of 2005 FY9, possibly N₂ ice, CO ice, or Ar. The spectrum of 2003 EL61 is remarkably featureless. There is a hint of an O₂ ice band at 5773 Å; however, this feature needs to be confirmed by future spectroscopic observations of 2003 EL61 with a higher continuum signal precision sufficient to detect a second, weaker O₂ ice band at 6275 Å.