title: The geologically recent giant impact basins at Vesta's south pole.
abstract: Dawn's global mapping of Vesta reveals that its observed south polar depression is composed of two overlapping giant impact features. These large basins provide exceptional windows into impact processes at planetary scales. The youngest, Rheasilvia, is 500 kilometers wide and 19 kilometers deep and finds its nearest morphologic analog among large basins on low-gravity icy satellites. Extensive ejecta deposits occur, but impact melt volume is low, exposing an unusual spiral fracture pattern that is likely related to faulting during uplift and convergence of the basin floor. Rheasilvia obliterated half of another 400-kilometer-wide impact basin, Veneneia. Both basins are unexpectedly young, roughly 1 to 2 billion years, and their formation substantially reset Vestan geology and excavated sufficient volumes of older compositionally heterogeneous crustal material to have created the Vestoids and howardite-eucrite-diogenite meteorites.
authors.affiliation: Lunar and Planetary Institute, Houston, TX 77058, USA. schenk@lpi.usra.edu
authors.forename: Paul
authors.initials: P
authors.lastname: Schenk
authors.forename: David P
authors.initials: DP
authors.lastname: O'Brien
authors.forename: Simone
authors.initials: S
authors.lastname: Marchi
authors.forename: Robert
authors.initials: R
authors.lastname: Gaskell
authors.forename: Frank
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authors.lastname: Preusker
authors.forename: Thomas
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authors.lastname: Roatsch
authors.forename: Ralf
authors.initials: R
authors.lastname: Jaumann
authors.forename: Debra
authors.initials: D
authors.lastname: Buczkowski
authors.forename: Thomas
authors.initials: T
authors.lastname: McCord
authors.forename: Harry Y
authors.initials: HY
authors.lastname: McSween
authors.forename: David
authors.initials: D
authors.lastname: Williams
authors.forename: Aileen
authors.initials: A
authors.lastname: Yingst
authors.forename: Carol
authors.initials: C
authors.lastname: Raymond
authors.forename: Chris
authors.initials: C
authors.lastname: Russell