title: The shape and surface variation of 2 Pallas from the Hubble Space Telescope.
abstract: We obtained Hubble Space Telescope images of 2 Pallas in September 2007 that reveal distinct color and albedo variations across the surface of this large asteroid. Pallas's shape is an ellipsoid with radii of 291 (+/-9), 278 (+/-9), and 250 (+/-9) kilometers, implying a density of 2400 (+/-250) kilograms per cubic meter-a value consistent with a body that formed from water-rich material. Our observations are consistent with the presence of an impact feature, 240 (+/-25) kilometers in diameter, within Pallas's ultraviolet-dark terrain. Our observations imply that Pallas is an intact protoplanet that has undergone impact excavation and probable internal alteration.
authors.affiliation: Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA. britneys@ucla.edu
authors.forename: B E
authors.initials: BE
authors.lastname: Schmidt
authors.forename: P C
authors.initials: PC
authors.lastname: Thomas
authors.forename: J M
authors.initials: JM
authors.lastname: Bauer
authors.forename: J-Y
authors.initials: JY
authors.lastname: Li
authors.forename: L A
authors.initials: LA
authors.lastname: McFadden
authors.forename: M J
authors.initials: MJ
authors.lastname: Mutchler
authors.forename: S C
authors.initials: SC
authors.lastname: Radcliffe
authors.forename: A S
authors.initials: AS
authors.lastname: Rivkin
authors.forename: C T
authors.initials: CT
authors.lastname: Russell
authors.forename: J Wm
authors.initials: JW
authors.lastname: Parker
authors.forename: S A
authors.initials: SA
authors.lastname: Stern