Hydrocode simulation of Ganymede and Europa cratering trends – How thick is Europa’s crust?

Bray, V. J.; Collins, G. S.; Morgan, J. V.; Melosh, H. J.; Schenk, P.

doi:10.1016/j.icarus.2013.12.009

Cited by 56 publications

(113 citation statements)

References 55 publications

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“…An animation of the best fit simulation for R i = 230 m is shown in the supporting information (Animation S1). This result is broadly consistent with the estimates derived from earlier numerical studies (Bray et al, ; Cox & Bauer, ).…”

Section: Resultssupporting

confidence: 92%

“…Recent numerical studies (Bray et al, ; Cox & Bauer, ) reproduced the observed crater d ‐ D and inflection points using a fully conductive icy shell over ocean. Bray et al () also matched crater morphology (e.g., summit pits and central domes) to discern the thickness of Europa's ice shell.…”

Section: Discussionmentioning

confidence: 84%

“…Recent developments and improvements in numerical models have opened the door for more sophisticated studies. Bray et al () estimated the ice shell thickness at 7 km, while simultaneously matching the observed crater morphologies (e.g., summit pit and dome craters) and depth‐diameter relationships (Schenk, ) (Figure ). Cox and Bauer () placed Europa's icy shell thickness at 10 km by numerically probing the effects of crust breaching and matching the observed crater depth‐diameter relationships (Figure ), regardless of observed morphology.…”

Section: Introductionmentioning

confidence: 88%

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Impact Crater Morphology and the Structure of Europa's Ice Shell

Silber

Johnson

2017

JGR Planets

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We performed numerical simulations of impact crater formation on Europa to infer the thickness and structure of its ice shell. The simulations were performed using iSALE to test both the conductive ice shell over ocean and the conductive lid over warm convective ice scenarios for a variety of conditions. The modeled crater depth‐diameter is strongly dependent on the thermal gradient and temperature of the warm convective ice. Our results indicate that both a fully conductive (thin) shell and a conductive‐convective (thick) shell can reproduce the observed crater depth‐diameter and morphologies. For the conductive ice shell over ocean, the best fit is an approximately 8 km thick conductive ice shell. Depending on the temperature (255–265 K) and therefore strength of warm convective ice, the thickness of the conductive ice lid is estimated at 5–7 km. If central features within the crater, such as pits and domes, form during crater collapse, our simulations are in better agreement with the fully conductive shell (thin shell). If central features form well after the impact, however, our simulations suggest that a conductive‐convective shell (thick shell) is more likely. Although our study does not provide a firm conclusion regarding the thickness of Europa's ice shell, our work indicates that Valhalla class multiring basins on Europa may provide robust constraints on the thickness of Europa's ice shell.

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Section: Resultssupporting

confidence: 92%

Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 88%

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Impact Crater Morphology and the Structure of Europa's Ice Shell

Silber

Johnson

2017

JGR Planets

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“…For a structure the size of the SP basin the curvature of Pluto's surface is important. Following Bray et al [2014], we use the Tillotson EOS for the ice shell and the ANEOS equation of state for water [Turtle and Pierazzo, 2001] to represent the ocean layer. Testing at a lower resolution (4 km resolution) revealed that models using full self-gravity were nearly identical to those that use a realistic central gravity field.…”

Section: Impact Modeling Methodsmentioning

confidence: 99%

“…To account for any viscous contribution, we consider a full viscoelastic-plastic ice rheology [Durham and Stern, 2001]. We apply an acoustic fluidization [Melosh, 1989] model using parameters motivated by Bray et al [2014]. We apply an acoustic fluidization [Melosh, 1989] model using parameters motivated by Bray et al [2014].…”

Section: Impact Modeling Methodsmentioning

confidence: 99%

Formation of the Sputnik Planum basin and the thickness of Pluto's subsurface ocean

Johnson

Bowling

Trowbridge

et al. 2016

Geophysical Research Letters

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We simulate the formation of the large elliptical impact basin associated with Pluto's Sputnik Planum (SP; informal name). The location of SP suggests that it represents a large positive mass anomaly. To find the conditions necessary for SP to have a positive mass anomaly, we consider impacts into targets with a range of thermal states and ocean thicknesses. Assuming the basin evolves to its current‐day configuration, we calculate the mass and gravity anomalies associated with SP. We find that SP can only achieve a large positive mass anomaly if Pluto has a more than 100 km thick salty ocean. This conclusion may help us better understand the composition and thermal evolution of Pluto. Furthermore, our work supports the hypothesis that SP basin has an impact origin.

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Impact breaching of Europa's ice: Constraints from numerical modeling

Cox

Bauer

2015

JGR Planets

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Numerical simulations show that impactors can penetrate Europa's ice, creating conduits to the underlying ocean. Breaching becomes inevitable when transient cavity depth exceeds 90% of ice thickness. Results indicate that a 0.5 km comet would penetrate 5 km ice, and a 5 km comet could breach 40 km ice. Thinner ice would be breached more frequently, thicker ice less so, but even the 40 km upper estimates for ice thickness would be penetrated by comets with recurrence intervals less than 250 Ma. If actual ice thickness is 8–13 km (indicated by comparing Europan and simulated crater geometries), the ocean could be exposed by impactors in the range 0.7–1.5 km, which have recurrence intervals ≈3 to 7 Ma. Thus, it seems that Europa's ice has been penetrated often in the past and possibly in geologically recent time. The largest known impact sites, Callanish and Tyre, probably represent transition from craters to penetrating impacts. The geomorphic expression of full penetration must exist on the surface; chaos terrain is a candidate. Astrobiological materials could be transported to the ocean via these impact‐created conduits.

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Hydrocode simulation of Ganymede and Europa cratering trends – How thick is Europa’s crust?

Cited by 56 publications

References 55 publications

Impact Crater Morphology and the Structure of Europa's Ice Shell

Impact Crater Morphology and the Structure of Europa's Ice Shell

Formation of the Sputnik Planum basin and the thickness of Pluto's subsurface ocean

Impact breaching of Europa's ice: Constraints from numerical modeling

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