The shape and surface variation of 2 Pallas from the Hubble Space Telescope.
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.
Schmidt
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Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA. britneys@ucla.edu
Thomas
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Bauer
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Li
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McFadden
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Mutchler
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Radcliffe
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Rivkin
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Russell
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Parker
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Stern
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