Compositional variation on the surface of Centaur 8405 Asbolus

Near-infrared 1-2 mum spectra of the Centaur 8405 Asbolus (1995 GO) have be en obtained using the Hubble Space Telescope near-infrared camera and multi object spectrometer. Strong and variable absorption features indicate a sig nificantly inhomogeneous surface characterized by water ice mixed with addi tional unknown constituents. Over a 1.7 hr interval, the observed spectra v aried from a nearly featureless spectrum to a very complicated absorption s pectrum, and the integrated flux varied in a manner consistent with previou s light-curve observations. The accepted rotation period of 8.9351 hr assum es 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.