Predictions for impactor contamination on Ceres based on hypervelocity impact experiments

Daly, R. T.; Schultz, P. H.

doi:10.1002/2015gl065601

Cited by 30 publications

(33 citation statements)

References 40 publications

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“…According to numerical simulations, which were applied to craters on the Moon's surface, the biggest proportion of the impactor's material remained in the crater for impacts occurring at 0 • angles (see Fig.1). Decreasing amount of projectile material is expected to be embedded in the target with increasing impact speed, as has been demonstrated for the Moon's surface by Bland et al (2008) and, more recently, by Daly & Schultz (2016) and, Daly & Schultz (2015b) for asteroid surfaces. In order to study this effect, we used impact speeds between 0.38 and 3.50 km/s.…”

Section: Experimental Set-upmentioning

confidence: 85%

“…However, considering an average impact speed of v = 5.3 km/s for Main Belt asteroid collisions (Bottke et al 1994), the collisional speed range that was tested (<1 km/s) in the experiments of Nagaoka et al (2014) was at the lower end of inter-asteroid collision velocities. Moreover, Daly & Schultz (2013, 2015a, Daly & Schultz (2016) and, Daly & Schultz (2015b) used aluminum and basalt projectiles which were fired onto pumice and highly porous waterice trying to explain the implantation of an impactor's material onto vestan regolith, and the possibility of a similar process onto Ceres' surface. McDermott et al (in preparation) used copper projectiles impacting porous (∼50%) water-ice targets at a wide range of speeds (1.00 -7.05 km/s).…”

Section: Introductionmentioning

confidence: 99%

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Survival of the impactor during hypervelocity collisions – I. An analogue for low porosity targets

Avdellidou¹,

Price²,

Delbò³

et al. 2015

Mon. Not. R. Astron. Soc.

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Recent observations of asteroidal surfaces indicate the presence of materials that do not match the bulk lithology of the body. A possible explanation for the presence of these exogenous materials is that they are products of inter-asteroid impacts in the Main Belt, and thus interest has increased in understanding the fate of the projectile during hypervelocity impacts. In order to gain insight into the fate of impactor we have carried out a laboratory programme, covering the velocity range of 0.38 -3.50 km/s, devoted to measuring the survivability, fragmentation and final state of the impactor. Forsterite olivine and synthetic basalt projectiles were fired onto low porosity (<10%) pure water-ice targets using the University of Kent's Light Gas Gun (LGG). We developed a novel method to identify impactor fragments which were found in ejecta and implanted into the target. We applied astronomical photometry techniques, using the SOURCE EXTRACTOR software, to automatically measure the dimensions of thousands of fragments. This procedure enabled us to estimate the implanted mass on the target body, which was found to be a few percent of the initial mass of the impactor. We calculated an order of magnitude difference in the energy density of catastrophic disruption, Q*, between peridot and basalt projectiles. However, we found very similar behaviour of the size frequency distributions for the hypervelocity shots (>1 km/s). After each shot, we examined the largest peridot fragments with Raman spectroscopy and no melt or alteration in the final state of the projectile was observed.

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Section: Experimental Set-upmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Survival of the impactor during hypervelocity collisions – I. An analogue for low porosity targets

Avdellidou¹,

Price²,

Delbò³

et al. 2015

Mon. Not. R. Astron. Soc.

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“…An exogenous origin of the olivine could be easily explained, from a qualitative point of view, as the natural outcome of the continuous flux of impactors on Vesta over the lifetime of the asteroid ) and would be supported by the results of hydrodynamic simulations of the fate of projectiles after hypervelocity impacts (Svetsov 2011;Turrini&Svetsov 2014;Svetsov and Shuvalov 2016). Recent impact experiments (Daly & Schultz 2015McDermott et al 2016, Avdellidou et al 2016) have provided strong observational support to this scenario, as they confirm that, in contrast to hypervelocity (>20-30 km/s) impacts where stony projectiles undergo complete vaporization (e.g., Melosh 1989; Svetsov and Shuvalov 2016), a significant fraction of the projectile indeed survives the impact at the velocities characteristic of the asteroid belt (Daly & Schultz 2015McDermott et al 2016, Avdellidou et al 2016).…”

Section: Introductionmentioning

confidence: 93%

Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations

Turrini

Svetsov

Consolmagno

et al. 2016

Icarus

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The survival of asteroid Vesta during the violent early history of the Solar System is a pivotal constraint on theories of planetary formation. Particularly important from this perspective is the amount of olivine excavated from the vestan mantle by impacts, as this constrains both the interior structure of Vesta and the number of major impacts the asteroid suffered during its life. The NASA Dawn mission revealed that olivine is present on Vesta's surface in limited quantities, concentrated in small patches at a handful of sites not associated with the two large impact basins Rheasilvia and Veneneia. The first detections were interpreted as the result of the excavation of endogenous olivine, even if the depth at which the detected olivine originated was a matter of debate. Later works raised instead the possibility that the olivine had an exogenous origin, based on the geologic and spectral features of the deposits. In this work, we quantitatively explore the proposed scenario of a exogenous origin for the detected vestan olivine to investigate whether its presence on Vesta can be explained as a natural outcome of the collisional history of the asteroid over the last one or more billion years. To perform this study we took advantage of the impact contamination model previously developed to study the origin and amount of dark and hydrated materials observed by Dawn on Vesta, a model we updated by performing dedicated hydrocode impact simulations. We show that the exogenous delivery of olivine by the same impacts that shaped the vestan surface can offer a viable explanation for the currently identified olivine-rich sites without violating the constraint posed by the lack of global olivine signatures on Vesta. Our results indicate that no mantle excavation is in principle required to explain the observations of the Dawn mission and support the idea that the vestan crust could be thicker than indicated by simple geochemical models based on the Howardite-Eucrite-Diogenite family of meteorites.al. 2016) in the first 3 Ma of the life of the Solar System (Bizzarro et al. 2005;Schiller et al. 2011; Consolmagno et al. 2015 and references therein).Compositional models of Vesta's interior based on the information provided by the HEDs and on cosmochemical constraints (Mandler and Elkins-Tanton 2013;Toplis et al. 2013;Consolmagno et al. 2015 and references therein) indicate that eucrites and diogenites represent the main components of the upper and lower crust of the asteroid, and that the total thickness of this crust should range between 20 and 40 km (see Consolmagno et al. 2015 for a detailed discussion of

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“…Based on the median excavation depth of all the impacts, the upper 5 km crustal layer contains the accreted material. Projectile retention efficiencies depend on the properties of the impactor and crust (82). Since the portion of accreted material retained in the crust is unknown, we estimated the pristine crustal composition for different retention efficiencies (from 0% to 50% in steps of 10%).…”

Section: Estimates Of Exogenic Pollutionmentioning

confidence: 99%

Extensive water ice within Ceres’ aqueously altered regolith: Evidence from nuclear spectroscopy

Prettyman

Yamashita

Toplis

et al. 2017

Science

185

251

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The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA’s Dawn mission, we determined the concentrations of elemental hydrogen, iron, and potassium on Ceres. The data show that surface materials were processed by the action of water within the interior. The non-icy portion of Ceres’ carbon-bearing regolith contains similar amounts of hydrogen to those present in aqueously altered carbonaceous chondrites; however, the concentration of iron on Ceres is lower than in the aforementioned chondrites. This allows for the possibility that Ceres experienced modest ice-rock fractionation, resulting in differences between surface and bulk composition. At mid-to-high latitudes, the regolith contains high concentrations of hydrogen, consistent with broad expanses of water ice, confirming theoretical predictions that ice can survive for billions of years just beneath the surface.

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Predictions for impactor contamination on Ceres based on hypervelocity impact experiments

Cited by 30 publications

References 40 publications

Survival of the impactor during hypervelocity collisions – I. An analogue for low porosity targets

Survival of the impactor during hypervelocity collisions – I. An analogue for low porosity targets

Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations

Extensive water ice within Ceres’ aqueously altered regolith: Evidence from nuclear spectroscopy

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