Compositional variation on the surface of Centaur 8405 Asbolus

Near-infrared 1-2 mum spectra of the Centaur 8405 Asbolus (1995 GO) have been obtained using the Hubble Space Telescope near-infrared camera and multiobject spectrometer. Strong and variable absorption features indicate a significantly inhomogeneous surface characterized by water ice mixed with additional unknown constituents. Over a 1.7 hr interval, the observed spectra varied from a nearly featureless spectrum to a very complicated absorption spectrum, and the integrated flux varied in a manner consistent with previous light-curve observations. The accepted rotation period of 8.9351 hr assumes a shape-dominated light curve. Our observations indicate that the light curve may in fact be dominated by a relatively bright spot with a period of 4.47 hr, i.e., half the previous value.