Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images

Binzel, Richard P.; Gaffey, M. J.; Thomas, P. C.; Zellner, B.; Storrs, A. D.; Wells, Edward F.

doi:10.1006/icar.1997.5734

Cited by 194 publications

(177 citation statements)

References 12 publications

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“…The asteroid Vesta is of great interest because Earth-based telescopic spectroscopy suggests that it has a basaltic to ultramafic composition (McCord et al, 1970;Binzel et al, 1997;Gaffey, 1997;Thomas et al, 1997;De Sanctis et al, 2012), which matches closely with that of the howardite-eucrite-diogenite (HED) basaltic achondrite meteorites. The presence of basaltic compositions and textures in the HEDs (e.g., McSween et al, 2011;McSween et al, 2013 and references therein) suggest that basaltic lava flows once extruded onto Vesta's surface (e.g., Wilson and Keil, 1996) or alternatively were derived from the crystallized remnants of a global magma ocean (Righter and Drake, 1997;Ruzicka et al, 1997;Warren, 1997), and that Vesta must have differentiated into a crust, mantle, and core (e.g., Keil, 2002;McSween et al, 2011).…”

Section: Introductionmentioning

confidence: 97%

“…Earth-based telescopic observations showed spectral evidence of basaltic mineralogies, and the inferred relationship of the HED meteorites to Vesta is well established (e.g., McCord et al, 1970;Feierberg et al, 1980;Gaffey, 1997;Binzel et al, 1997;Cochran and Villas, 1998) and has been confirmed by the Dawn observations De Sanctis et al, 2012). Petrologic study of the Vesta-derived HED meteorites demonstrates the presence of basaltic minerals and glassy textures that are diagnostic of basaltic lava flows on Earth (McSween et al, 2011(McSween et al, , 2013, or alternatively that these basaltic minerals were derived from crystallization of a global magma ocean that may have once covered Vesta (e.g., Righter and Drake, 1997;Ruzicka et al, 1997;Warren, 1997).…”

Section: Volcanic Hypothesismentioning

confidence: 99%

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Lobate and flow-like features on asteroid Vesta

Williams

O’Brien

Schenk

et al. 2014

Planetary and Space Science

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a b s t r a c tWe studied high-resolution images of asteroid Vesta's surface ( $ 70 and 20-25 m/pixel) obtained during the High-and Low-Altitude Mapping Orbits (HAMO, LAMO) of NASA's Dawn mission to assess the formation mechanisms responsible for a variety of lobate, flow-like features observed across the surface. We searched for evidence of volcanic flows, based on prior mathematical modeling and the well-known basaltic nature of Vesta's crust, but no unequivocal morphologic evidence of ancient volcanic activity has thus far been identified. Rather, we find that all lobate, flow-like features on Vesta appear to be related either to impact or erosional processes. Morphologically distinct lobate features occur in and around impact craters, and most of these are interpreted as impact ejecta flows, or possibly flows of impact melt. Estimates of melt production from numerical models and scaling laws suggests that large craters like Marcia ( $ 60 km diameter) could have potentially produced impact melt volumes ranging from tens of millions of cubic meters to a few tens of cubic kilometers, which are relatively small volumes compared to similar-sized lunar craters, but which are consistent with putative impact melt features observed in Dawn images. There are also examples of lobate flows that trend downhill both inside and outside of crater rims and basin scarps, which are interpreted as the result of gravity-driven mass movements (slumps and landslides).

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Section: Introductionmentioning

confidence: 97%

Section: Volcanic Hypothesismentioning

confidence: 99%

Lobate and flow-like features on asteroid Vesta

Williams

O’Brien

Schenk

et al. 2014

Planetary and Space Science

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“…Albedo differences on 4 Vesta's surface were observed in multispectral images obtained by the Hubble Space Telescope Binzel et al, 1997;. However, regions of very low albedo on Vesta's surface were first discovered by the Dawn mission (Jaumann et al, 2012a;Russell et al, 2012;McCord et al, 2012;Reddy et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

The geological nature of dark material on Vesta and implications for the subsurface structure

Jaumann

Naß

Otto

et al. 2014

Icarus

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a b s t r a c tDeposits of dark material appear on Vesta's surface as features of relatively low-albedo in the visible wavelength range of Dawn's camera and spectrometer. Mixed with the regolith and partially excavated by younger impacts, the material is exposed as individual layered outcrops in crater walls or ejecta patches, having been uncovered and broken up by the impact. Dark fans on crater walls and dark deposits on crater floors are the result of gravity-driven mass wasting triggered by steep slopes and impact seismicity. The fact that dark material is mixed with impact ejecta indicates that it has been processed together with the ejected material. Some small craters display continuous dark ejecta similar to lunar dark-halo impact craters, indicating that the impact excavated the material from beneath a higher-albedo surface. The asymmetric distribution of dark material in impact craters and ejecta suggests non-continuous distribution in the local subsurface. Some positive-relief dark edifices appear to be impact-sculpted hills with dark material distributed over the hill slopes. Dark features inside and outside of craters are in some places arranged as linear outcrops along scarps or as dark streaks perpendicular to the local topography. The spectral characteristics of the dark material resemble that of Vesta's regolith. Dark material is distributed unevenly across Vesta's surface with clusters of all types of dark material exposures. On a local scale, some craters expose or are associated with dark material, while others in the immediate vicinity do not show evidence for dark material. While the variety of surface exposures of dark material and their different geological correlations with surface features, as well as their uneven distribution, indicate a globally inhomogeneous distribution in the subsurface, the dark material seems to be correlated with the rim and ejecta of the older Veneneia south polar basin structure. The origin of the dark material is still being debated, however, the geological analysis suggests that it is exogenic, from carbon-rich low-velocity impactors, rather than endogenic, from freshly exposed mafic material or melt, exposed or created by impacts.

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“…These density measurement are hardly comparable. Vesta is a differ- entiated asteroid with a pyroxene-rich crust, analog to the HED meteorites, and a denser olivine-rich mantle (e.g., McCord et al 1970;Binzel et al 1997). The low density of Lundia and Frostia implies a high macroporosity, above 50%, in the rubble-pile regime.…”

Section: S-complex and Related End-membersmentioning

confidence: 99%

Density of asteroids

Carry

2012

Planetary and Space Science

525

444

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The small bodies of our solar system are the remnants of the early stages of planetary formation. A considerable amount of information regarding the processes that occurred during the accretion of the early planetesimals is still present among this population. A review of our current knowledge of the density of small bodies is presented here. Density is indeed a fundamental property for the understanding of their composition and internal structure. Intrinsic physical properties of small bodies are sought by searching for relationships between the dynamical and taxonomic classes, size, and density. Mass and volume estimates for 287 small bodies (asteroids, comets, and transneptunian objects) are collected from the literature. The accuracy and biases affecting the methods used to estimate these quantities are discussed and best-estimates are strictly selected. Bulk densities are subsequently computed and compared with meteorite density, allowing to estimate the macroporosity (i.e., amount of voids) within these bodies. Dwarf-planets apparently have no macroporosity, while smaller bodies (<400 km) can have large voids. This trend is apparently correlated with size: C and S-complex asteroids tends to have larger density with increasing diameter. The average density of each Bus-DeMeo taxonomic classes is computed (DeMeo et al., 2009, Icarus 202). S-complex asteroids are more dense on average than those in the C-complex that in turn have a larger macroporosity, although both complexes partly overlap. Within the C-complex asteroids, B-types stand out in albedo, reflectance spectra, and density, indicating a unique composition and structure. Asteroids in the Xcomplex span a wide range of densities, suggesting that many compositions are included in the complex. Comets and TNOs have high macroporosity and low density, supporting the current models of internal structures made of icy aggregates. Although the number of density estimates sky-rocketed during last decade from a handful to 287, only a third of the estimates are more precise than 20%. Several lines of investigation to refine this statistic are contemplated, including observations of multiple systems, 3-D shape modeling, and orbital analysis from Gaia astrometry.Keywords: Minor planets, Mass, Volume, Density, Porosity Small bodies as remnants of planetesimalsThe small bodies of our solar System are the left-overs of the building blocks that accreted to form the planets, some 4.6 Gyr ago. They represent the most direct witnesses of the conditions that reigned in the proto-planetary nebula (Bottke et al. 2002a). Indeed, terrestrial planets have thermally evolved and in some cases suffered erosion (e.g., plate tectonic, volcanism) erasing evidence of their primitive composition. For most small bodies, however, their small diameter limited the amount of radiogenic nuclides in their interior, and thus the amount of energy for internal heating. The evolution of small bodies is therefore mainly exogenous, through eons of collisions, external heating, and bombardm...

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Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images

Cited by 194 publications

References 12 publications

Lobate and flow-like features on asteroid Vesta

Lobate and flow-like features on asteroid Vesta

The geological nature of dark material on Vesta and implications for the subsurface structure

Density of asteroids

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