The structure of the asteroid 4 Vesta as revealed by models of planet-scale collisions

Jutzi, Martin; Asphaug, Erik; Gillet, Philippe; Barrat, Jean‐Alix; Benz, W.

doi:10.1038/nature11892

Cited by 92 publications

(131 citation statements)

References 25 publications

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“…Impact modeling suggests that the Rheasilvia ejecta were globally distributed, reaching also the northern hemisphere (e.g., Jutzi et al, 2013b). Dawn observations show that mantling by Rheasilvia impact debris is limited to within 100 km from the rim (e.g., Schenk et al, 2012) and that the debris morphology changes from flow-like features close to the rim to ripples away from the rim (Otto et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

Geologic map of the northern hemisphere of Vesta based on Dawn Framing Camera (FC) images

Ruesch

Hiesinger

Blewett

et al. 2014

Icarus

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a b s t r a c tThe Dawn Framing Camera (FC) has imaged the northern hemisphere of the Asteroid (4) Vesta at high spatial resolution and coverage. This study represents the first investigation of the overall geology of the northern hemisphere (22-90°N, quadrangles Av-1, 2, 3, 4 and 5) using these unique Dawn mission observations. We have compiled a morphologic map and performed crater size-frequency distribution (CSFD) measurements to date the geologic units. The hemisphere is characterized by a heavily cratered surface with a few highly subdued basins up to $200 km in diameter. The most widespread unit is a plateau (cratered highland unit), similar to, although of lower elevation than the equatorial Vestalia Terra plateau. Large-scale troughs and ridges have regionally affected the surface. Between $180°E and $270°E, these tectonic features are well developed and related to the south pole Veneneia impact (Saturnalia Fossae trough unit), elsewhere on the hemisphere they are rare and subdued (Saturnalia Fossae cratered unit). In these pre-Rheasilvia units we observed an unexpectedly high frequency of impact craters up to $10 km in diameter, whose formation could in part be related to the Rheasilvia basin-forming event. The Rheasilvia impact has potentially affected the northern hemisphere also with S-N small-scale lineations, but without covering it with an ejecta blanket. Post-Rheasilvia impact craters are small (<60 km in diameter) and show a wide range of degradation states due to impact gardening and mass wasting processes. Where fresh, they display an ejecta blanket, bright rays and slope movements on walls. In places, crater rims have dark material ejecta and some crater floors are covered by ponded material interpreted as impact melt.

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Section: Discussionmentioning

confidence: 99%

Geologic map of the northern hemisphere of Vesta based on Dawn Framing Camera (FC) images

Ruesch

Hiesinger

Blewett

et al. 2014

Icarus

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“…We estimate the upper limit of the angular momentum delivered in one such impact. Assuming a diameter of 66 km, velocity of 5400 m s −1 (Jutzi et al, 2013), and density of 3000 kg m −3 for the Rheasilvia impactor, its maximum angular momentum is 0.17×10 27 kg m 2 s −1 for an impact at 75…”

Section: Discussionmentioning

confidence: 99%

“…At the same time, giant impact simulations suggest that ejecta from the Rheasilvia basin-forming event created a belt of increased crustal thickness near the present-day equator and that surface topography north of this equatorial ridge likely underwent minimal modification [e.g., Jutzi and Asphaug (2011);Jutzi et al (2013); Ivanov and Melosh (2012)]. Crustal thickness maps derived from Bouguer gravity anomalies show a clear ring of high crustal thickness in the equatorial region [ Fig.…”

Section: Relic Hydrostatic Terrainsmentioning

confidence: 99%

Efficient early global relaxation of asteroid Vesta

Hager

Ermakov

et al. 2014

Icarus

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The asteroid Vesta is a differentiated planetesimal from the accretion phase of solar system formation. Although its present-day shape is dominated by a non-hydrostatic fossil equatorial bulge and two large, mostly unrelaxed impact basins, Vesta may have been able to approach hydrostatic equilibrium during a brief early period of intense interior heating. We use a finite element viscoplastic flow model coupled to a 1D conductive cooling model to calculate the expected rate of relaxation throughout Vesta's early history. We find that, given sufficient non-hydrostaticity, the early elastic lithosphere of Vesta experienced extensive brittle failure due to self-gravity, thereby allowing relaxation to a more hydrostatic figure. Soon after its accretion, Vesta reached a closely hydrostatic figure with <2 km non-hydrostatic topography at degree-2, which, once scaled, is similar to the maximum disequilibrium of the hydrostatic asteroid Ceres. Vesta was able to support the modern observed amplitude of non-hydrostatic topography only >40-200 My after formation, depending on the assumed depth of megaregolith. The Veneneia and Rheasilvia giant impacts, which generated most non-hydrostatic topography, must have therefore occurred >40-200 My after formation. Based on crater retention ages, topography, and relation to known impact generated features, we identify a large region in the northern hemisphere that likely represents relic hydrostatic terrain from early Vesta. The long-wavelength figure of this terrain suggests that, before the two late giant impacts, Vesta had a rotation period of 5.02 hr (6.3% faster than present) while its spin axis was offset by 3.0• from that of the present. The evolution of Vesta's figure shows that the hydrostaticity of small bodies depends strongly on its age and specific impact history and that a single body may embody both hydrostatic and non-hydrostatic terrains and epochs.

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“…Impacts that formed the Veneneia (Schenk et al, 2012;Reddy et al, 2012b;Marchi et al, 2012) and Rheasilvia basins (Thomas et al, 1997;Jaumann et al, 2012;Schenk et al, 2012;Marchi et al, 2012), modified the shape and topography of Vesta at a global scale (Jaumann et al, 2012;Gaskell, 2012;Buczkowski et al, 2012), and greatly disturbed the surface materials (Jutzi et al, 2013, De Sanctis et al, 2012a, Ammannito et al, 2013b. The northern regions, because of their distance from the Rheasilvia and Veneneia basins, should be least disturbed by the giant impacts.…”

Section: Introductionmentioning

confidence: 95%