90482 Orcus Etruscan equivalent of the Roman Pluto, and later became an alternate name for Pluto. The surface of Orcus is relatively bright with albedo reaching 23%, grey in color and water-rich. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present. The existence of a satellite allowed astronomers to determine the mass of the system, which is approximately equal to that of the Saturnian moon Tethys. The ratio of masses of Orcus and Vanth is uncertain, possibly anywhere from 1:33 to 1:12. The diameter of Orcus
90482 Orcus a result of rotational fission of the primordial Orcus, which would have rotated much faster than now. On 23 March 2009, Brown asked readers of his weekly column to suggest possible names for the satellite, with the best one to be submitted to the International Astronomical Union (IAU) on 5 April. The name Vanth, after the Etruscan goddess who guided the souls of the dead to the underworld, was eventually chosen from among a large pool of submissions. This submission was assessed by the IAU's Committee for Small Body Nomenclature, which voted to approve it in March 2010, in accordance