Asymmetric craters on Vesta: Impact on sloping surfaces

Krohn, Katrin; Jaumann, R.; Elbeshausen, D.; Kneissl, T.; Schmedemann, N.; Wagner, Roland; Voigt, Joana; Otto, Katharina A.; Matz, Klaus-Dieter; Preusker, Frank; Stephan, K.; Raymond, C. A.; Russell, C.T.

doi:10.1016/j.pss.2014.04.011

Cited by 37 publications

(54 citation statements)

References 49 publications

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“…The eastern part is mainly composed by regolith deposited by mass movements (Schafer et al, 2014;Krohn et al, 2014) and for this reason, it is darker than ejecta materials, which originated from depth and are hence fresher.…”

Section: Rheasilvia Terrains and Superimposed Ejectamentioning

confidence: 99%

Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key features

Longobardo

Palomba

Sanctis

et al. 2015

Icarus

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Section: Rheasilvia Terrains and Superimposed Ejectamentioning

confidence: 99%

Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key features

Longobardo

Palomba

Sanctis

et al. 2015

Icarus

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“…The high ejection angle would have prevented the material moving far away from the crater and create secondary craters outside the ejecta blanket (Schmedemann et al, in preparation; Bierhaus et al, 2012). Krohn et al (2013) mapped the distribution of the asymmetric craters on a global scale and discussed their formation on Vesta. They suggested that the downhill rim is a mixture of ejected material and material of the original slope.…”

Section: This Issue)mentioning

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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“…8). Helena is one of the common asymmetric craters found on Vesta (Krohn et al, 2014). These craters form when impacts hit a steep slope.…”

Section: Geological Settings Of Dark Materialsmentioning

confidence: 99%

“…In addition, the occurrences of the striations indicate an inhomogeneous distribution of the dark material in the subsurface as small patches rather than extended layers. This impact produced an asymmetric crater (Jaumann et al, 2012a;Krohn et al, 2014), striking a southto-north tilted slope with fallback ejecta covering the northern downslope rim. This explains the lack of dark outcrops and striations in the northern part of the crater (Fig.…”

Section: Interpretation Of Craters With Dark Ejectamentioning

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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Asymmetric craters on Vesta: Impact on sloping surfaces

Cited by 37 publications

References 49 publications

Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key features

Mineralogical and spectral analysis of Vesta’s Gegania and Lucaria quadrangles and comparative analysis of their key features

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

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

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