The shape and surface variation of 2 Pallas from the Hubble Space Telescope.

Schmidt, B E; Thomas, P C; Bauer, J M; Li, J-Y; McFadden, L A; Mutchler, M J; Radcliffe, S C; Rivkin, A S et al. · Science · 2009

basic_science · Level V

Where this comes from

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.