The Deep Impact oblique impact cratering experiment

Schultz, P. H.; Eberhardy, C. A.; Ernst, C. M.; A’Hearn, Michael F.; Sunshine, J. M.; Lisse, C. M.

doi:10.1016/j.icarus.2007.06.006

Cited by 95 publications

(84 citation statements)

References 41 publications

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“…Previous studies of hypervelocity impacts on fluffy materials have shown that the resultant craters generally have bowlshaped bottoms (Housen & Holsapple 2003;Schultz et al 2007;Yasui et al 2012). This is one reason for believing that the circular depressions found on 67P and other comets with steep-walls and flat-bottoms are not of impact origin although we cannot rule out that some of the pits may have been related to impact events.…”

Section: Observationsmentioning

confidence: 78%

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Lai

Lee

et al. 2016

A&A

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Aims. We aim to characterize the circular depressions of comet 67P/Churyumov-Gerasimenko and investigate whether such surface morphology of a comet nucleus is related to the cumulative sublimation effect since becoming a Jupiter family comet (JFC). Methods. The images from the Rosetta/OSIRIS science camera experiment are used to construct size frequency distributions of the circular depression structures on comet 67P and they are compared with those of the JFCs 81P/Wild 2, 9P/Tempel 1, and 103P/Hartley 2. The orbital evolutionary histories of these comets over the past 100 000 yr are analyzed statistically and compared with each other. Results. The global distribution of the circular depressions over the surface of 67P is charted and classified. Descriptions are given to the characteristics and cumulative size frequency distribution of the identified features. Orbital statistics of the JFCs visited by spacecraft are derived. Conclusions. The size frequency distribution of the circular depressions is found to have a similar power law distribution to those of 9P/Tempel 1 and 81P/Wild 2. This might imply that they could have been generated by the same process. Orbital integration calculation shows that the surface erosion histories of 81P/Wild 2, and 9P/Tempel 1 could be shorter than those of 67P, 103 P/Hartley 2 and 19P/Borrelly. From this point of view, the circular depressions could be dated back to the pre-JFC phase or the transneptunian phase of these comets. The north-south asymmetry in the distribution of the circular depressions could be associated with the heterogeneous structure of the nucleus of comet 67P and/or the solar insolation history.

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Section: Observationsmentioning

confidence: 78%

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Lai

Lee

et al. 2016

A&A

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“…43 These Swan bands are well known in carbon-rich plasma spectra originating from several sources, including high-speed impacts, the ablation of graphite, the electrical discharge of acetylene, or chemical vapor deposition. 8,10,[47][48][49][50][51] Schultz et al previously examined spectral signatures from oblique impacts into porous particulates and found evidence that Swan band emission can originate from hydrocarbon bearing targets or from the dissociation of carbon-rich compounds under low atmospheric pressure conditions. 10 Additional work by Sugita and Schultz investigated impacts of polycarbonate on water and yielded strong C 2 Swan band emission, which they attributed to a high-temperature carbon-rich vapor that was ablated from rapidly moving, fine-grain fragments in the expanding impact-induced vapor cloud.…”

Section: Fig 15mentioning

confidence: 99%

Examining the temporal evolution of hypervelocity impact phenomena via high-speed imaging and ultraviolet-visible emission spectroscopy

Tandy

Mihaly

Adams

et al. 2014

Journal of Applied Physics

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A model for debris clouds produced by impact of hypervelocity projectiles on multiplate structures Appl. Phys. Lett. 93, 211905 (2008) Examining the temporal evolution of hypervelocity impact phenomena via high-speed imaging and ultraviolet-visible emission spectroscopy The temporal evolution of a previously observed hypervelocity impact-induced vapor cloud [Mihaly et al., Int. J. Impact Eng. 62, 13 (2013)] was measured by simultaneously recording several full-field, near-IR images of the resulting emission using an OMA-V high-speed camera. A two-stage light-gas gun was used to accelerate 5 mg Nylon 6/6 right-cylinders to speeds between 5 km/s and 7 km/s to impact 1.5 mm thick 6061-T6 aluminum target plates. Complementary laserside-lighting [Mihaly et al., Int. J. Impact Eng. 62, 13 (2013); Proc. Eng. 58, 363 (2013)] and frontof-target (without laser illumination) images were also captured using a Cordin ultra-high-speed camera. The rapid expansion of the vapor cloud was observed to contain a bright, emitting exterior, and a darker, optically thick interior. The shape of this phenomenon was also observed to vary considerably between experiments due to extremely high-rate (>250 000 rpm) of tumbling of the cylindrical projectiles. Additionally, UV-vis emission spectra were simultaneously recorded to investigate the temporal evolution of the atomic and molecular composition of the up-range, impact-induced vapor plume. A PI-MAX3 high-speed camera coupled to an Acton spectrograph was utilized to capture the UV-vis spectra, which shows an overall peak in emission intensity between approximately 6-10 ls after impact trigger, corresponding to an increased quantity of emitting vapor/plasma passing through the spectrometer slit during this time period. The relative intensity of the numerous spectral bands was also observed to vary according to the exposure delay of the camera, indicating that the different atomic/molecular species exhibit a varied temporal evolution during the vapor cloud expansion. Higher resolution spectra yielded additional emission lines/bands that provide further evidence of interaction between fragmented projectile material and the 1 mmHg atmosphere inside the target chamber. A comparison of the data to down-range emission spectra also revealed differences in the relative intensities of the atomic/molecular composition of the observed vapor clouds. V C 2014 AIP Publishing LLC.

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“…Laboratory studies using two-stage light gas guns are limited to about 6 to 8 km s −1 , but this is not very far from the actual conditions. Schultz et al (2007) describe a detailed laboratory simulation approach using just this correspondence.…”

Section: Basic Cratering Physicsmentioning

confidence: 99%

A ballistics analysis of the Deep Impact ejecta plume: Determining Comet Tempel 1's gravity, mass, and density

Richardson

Melosh

Lisse

et al. 2007

Icarus

148

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In July of 2005, the Deep Impact mission collided a 366 kg impactor with the nucleus of Comet 9P/Tempel 1, at a closing speed of 10.2 km s −1 . In this work, we develop a first-order, three-dimensional, forward model of the ejecta plume behavior resulting from this cratering event, and then adjust the model parameters to match the flyby-spacecraft observations of the actual ejecta plume, image by image. This modeling exercise indicates Deep Impact to have been a reasonably "well-behaved" oblique impact, in which the impactor-spacecraft apparently struck a small, westward-facing slope of roughly 1/3-1/2 the size of the final crater produced (determined from initial ejecta plume geometry), and possessing an effective strength of not more thanȲ = 1-10 kPa. The resulting ejecta plume followed well-established scaling relationships for cratering in a medium-to-high porosity target, consistent with a transient crater of not more than 85-140 m diameter, formed in not more than 250-550 s, for the case ofȲ = 0 Pa (gravity-dominated cratering); and not less than 22-26 m diameter, formed in not less than 1-3 s, for the case of Y = 10 kPa (strength-dominated cratering). AtȲ = 0 Pa, an upper limit to the total ejected mass of 1.8 × 10 7 kg (1.5-2.2 × 10 7 kg) is consistent with measurements made via long-range remote sensing, after taking into account that 90% of this mass would have stayed close to the surface and then landed within 45 min of the impact. However, atȲ = 10 kPa, a lower limit to the total ejected mass of 2.3 × 10 5 kg (1.5-2.9 × 10 5 kg) is also consistent with these measurements. The expansion rate of the ejecta plume imaged during the look-back phase of observations leads to an estimate of the comet's mean surface gravity ofḡ = 0.34 mm s −2 (0.17-0.90 mm s −2 ), which corresponds to a comet mass of m t = 4.5 × 10 13 kg (2.3-12.0 × 10 13 kg) and a bulk density of ρ t = 400 kg m −3 (200-1000 kg m −3 ), where the large high-end error is due to uncertainties in the magnitude of coma gas pressure effects on the ejecta particles in flight.

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The Deep Impact oblique impact cratering experiment

Cited by 95 publications

References 41 publications

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Physical properties and dynamical relation of the circular depressions on comet 67P/Churyumov-Gerasimenko

Examining the temporal evolution of hypervelocity impact phenomena via high-speed imaging and ultraviolet-visible emission spectroscopy

A ballistics analysis of the Deep Impact ejecta plume: Determining Comet Tempel 1's gravity, mass, and density

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