The Sextilia-region on Asteroid 4Vesta - Stratigraphy and variegation

Mapping Vesta' surface composition in the Sextilia region offers the unique possibility to investigate stratigraphic relationship of the surface compounds throughout the transition from Rheasilvia, Vesta's prominent impact basin, to Vesta's northern equatorial region. The VIR data point to an upper eucrite-dominated layer overlaying extended deposits of diogenite in the subsurface, which reaches the surface at Matronalia Rupes, the uplifted rim of the Rheasilvia impact structure. The dominance of diogenite in Matronalia Rupes suggests the existence of an extended diogenite-rich layer and supports the magma-ocean model as the most plausible formation model for Vesta's interior. Local enrichment of diogenite outside of the Rheasilvia impact basin are interpreted as outcrops of diogenite-dominated breccia excavated during the Rheasilvia impact event and re-excavated by more recent impacts. On the contrary, the asymmetry in the distribution of diogenite-rich outcrops in the norther parts, i.e., the depletion of these deposits in the Veneneia region, is at odds with the equally distributed plutonic intrusions of diogenite-rich material as proposed in the serial magmatism model but could be explained by an uneven distribution of its ejecta on Vesta's surface due to an oblique Rheasilvia impact.