Surface Composition of Vesta: Issues and Integrated Approach

Pieters, C. M.; McFadden, L. A.; Prettyman, T. H.; Sanctis, M. C. De; McCord, T. B.; Hiroi, T.; Klima, R. L.; Li, Jian‐Yang; Jaumann, R.

doi:10.1007/s11214-011-9809-5

Cited by 25 publications

(19 citation statements)

References 86 publications

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“…; O'Brien and Sykes ), as well as our expectations for the interiors and surfaces of Vesta (Pieters et al. ; Zuber et al. ) and Ceres (McCord et al.…”

Section: Introductionsupporting

confidence: 78%

Dawn completes its mission at 4 Vesta

Russell

Raymond

Jaumann

et al. 2013

Meteorit & Planetary Scien

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Abstract-The Dawn mission was designed to test our hypothesis about the origin and evolution of the early solar system by visiting the largest differentiated basaltic asteroid, 4 Vesta, believed to be a survivor from the earliest times of rocky body formation. Observations from orbit show that Vesta is the parent body of the Howardite, Eucrite, Diogenite meteorites. Vesta has an iron core and a eucritic-diogenitic crust. Its surface is characterized by abundant impact craters but with no evident volcanic features. It has two ancient impact basins in the southern hemisphere that are associated with circum-planetary troughs. The northern hemisphere is the more heavily cratered and contains the oldest terrains. The surface of Vesta is diverse, with north-south and east-west dichotomies in the eucrite-to-diogenite ratio. Its surface contains both very bright and very dark material, and its color varies strongly from region to region. Both the mineralogical and the elemental compositions agree with that expected for the HED parent body. Significant OH or H may be present in the upper crust and the presence of pits in "fresh" craters is consistent with the devolatilization of the surface after a collision either brought to or tapped a source of water on Vesta. The presence of dark material on the surface of Vesta suggests efficient transport pathways for organic material, and the mixing of the dark material with the more pristine pyroxene explains the varying albedo across the surface. Vesta has proven to be a reliable witness to the formation of the solar system.

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“…; O'Brien and Sykes ), as well as our expectations for the interiors and surfaces of Vesta (Pieters et al. ; Zuber et al. ) and Ceres (McCord et al.…”

Section: Introductionsupporting

confidence: 78%

Dawn completes its mission at 4 Vesta

Russell

Raymond

Jaumann

et al. 2013

Meteorit & Planetary Scien

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“…The analysis of the spectra of basaltic asteroids that are not directly connected to Vesta can provide insight into the question of the relevance of the space weathering as a function of the distance from the Sun. They will also be useful in the context of the NASA Dawn mission, which has been in orbit around Vesta since July 2011 (Russell et al 2007;Pieters et al 2011). Preliminary data from Dawn seem to confirm that a variety of colors exist in different regions of Vesta, which is, however, on average, bluer than the majority of V-types.…”

Section: Implications For V-types and Vestamentioning

confidence: 92%

Space weathering of Vesta and V-type asteroids: new irradiation experiments on HED meteorites

Fulvio

Brunetto

Vernazza

et al. 2012

A&A

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Context. In the past few decades, several tens of main belt asteroids have been found to exhibit basaltic surface composition, similar to the one of Vesta and basaltic Howardite, Eucrite, and Diogenite achondrite meteorites (HEDs). Most of these objects (V-types) belong to the Vesta dynamical family. Several questions on the relationship between Vesta, V-types, and HEDs are still unresolved. In particular, Vesta is spectroscopically bluer than most V-types. Aims. To date, it has not yet been understood whether these spectral differences are due to space weathering, similar to what has been observed for OC meteorites and S-type asteroids. To test this hypothesis, ion irradiation experiments were performed on different samples of eucrites to simulate the effects of space weathering on Vesta and V-types by solar wind ions. Methods. Eucrite meteorites were analyzed before and after different stages of ion irradiation by VIS-NIR reflectance spectroscopy (0.4-2.5 μm). We used different ions (Ar + , C + ) with different energies (from 60 to 200 keV) to weather the samples. Results. Ion irradiation was observed to alter the spectral properties of eucrite meteorites, inducing progressive reddening and darkening of the irradiated samples. Different eucrite samples (Bereba and Dar Al Gani 684) show different reddening behaviors. Because they are patchy, reddening also varied between different parts of the same meteorite. Moreover, for both meteorites, irradiation effects are much faster (∼100 times) for C + than for Ar + ions. Conclusions. Comparing the laboratory spectra of eucrites before and after different stages of ion irradiation with those of V-types, it turns out that the slope spread shown by V-type asteroids can be explained by space weathering. These results provide new clues to the connection between Vesta, V-types, and HEDs, and are also useful in the context of the NASA Dawn mission to Vesta.

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“…A stereographic map of three narrowband ratios (749 nm/438 nm, 749 nm/917 nm, and 438 nm/749 nm) in HAMO resolution was applied for surface compositional interpretation. Tompkins and Pieters [] and Pieters et al [] used these band ratios to define the Moon's mafic mineralogy; here Dawn HAMO images were used to calculate the same ratios for Vesta. The ratios indicate the depth of pyroxene absorption around 1000 nm (749 nm/917 nm) and the change of absorption between visible infrared and ultraviolet wavelengths (438 nm/749 nm).…”

Section: Methodsmentioning

confidence: 99%

Mass‐wasting features and processes in Vesta's south polar basin Rheasilvia

et al. 2013

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[1] The Rheasilvia crater is Vesta's largest impact basin. It is a 500 km diameter complex crater centered near the south pole and overlying the 400 km diameter impact basin Veneneia. Using Framing Camera (FC) data from the Dawn spacecraft's Low Altitude Mapping Orbit (20 m/pixel) and a digital terrain model derived from High Altitude Mapping Orbit stereo data, we identified various mass-wasting features within the south polar region. These features include intra-crater mass movements, flow-like and creep-like structures, slumping areas, landslides, and curved radial and concentric ridges. Intra-crater mass-wasting features are represented by lobate slides, talus material, dark patches on the crater wall, spurs along the crater rim and boulders. Slumping areas develop in compact material, whereas landslides form in relatively loose material. Both may be triggered by seismic shaking induced by impacts. Intra-crater mass wasting and slid and slumped materials are homogeneously distributed throughout the basin. Slumping and sliding processes have contributed most efficiently to basin degradation. Flow-like and creep-like features originate from granular material and cluster between 0 ı E and 90 ı E, an area exposing shocked and fractured material from the Rheasilvia impact event. The radial curved ridges are likely to be remnants of the early Rheasilvia collapse process, when radially moving masses were deflected by the Coriolis Effect. The concentric ridges are artifacts from the crater rim collapse. Curved ridges at the intersection of Rheasilvia and Veneneia, and on Rheasilvia's central peak, may also have been influenced by the Rheasilvia basin relaxation process, and an oblique impact, respectively.

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Surface Composition of Vesta: Issues and Integrated Approach

Cited by 25 publications

References 86 publications

Dawn completes its mission at 4 Vesta

Dawn completes its mission at 4 Vesta

Space weathering of Vesta and V-type asteroids: new irradiation experiments on HED meteorites

Mass‐wasting features and processes in Vesta's south polar basin Rheasilvia

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