A Reevaluation of Impact Melt Production

Pierazzo, E.; Vickery, A. M.; Melosh, H. J.

doi:10.1006/icar.1997.5713

Cited by 461 publications

(599 citation statements)

References 17 publications

(3 reference statements)

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“…We have approximated the best-fit computed relationship by equating mass scaling to volume scaling and to one of pure kinetic energy scaling, which is consistent, within uncertainty, to best fit parameters determined by Pierazzo et al [22]. If we take the limit that the deposited heat is efficiently redistributed through the entire planet, and equate the righthand side of equation (1.3) with the resulting thermal energy: M p C P (T p − T s ) then assuming that the entire planet starts off isothermally at T s , 4) where the prime on the heat capacity indicates an effective value that accounts for the latent heat of melting [23], and the efficiency of kinetic energy deposition…”

Section: −2β Pmentioning

confidence: 81%

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Melting in super-earths

Stixrude

2014

Phil. Trans. R. Soc. A.

104

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We examine the possible extent of melting in rockiron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of superearths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of superearth interiors based on existing experimental and ab initio results and scaling laws. We construct superearth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

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Section: −2β Pmentioning

confidence: 81%

“…A hydrodynamical modelling study [22] found that the amount of melt M melt produced scales with the kinetic energy of the impactor of mass M i and velocity v i as…”

Section: −2β Pmentioning

confidence: 99%

Melting in super-earths

Stixrude

2014

Phil. Trans. R. Soc. A.

104

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“…We now turn to theoretical modeling to assess how much melt should occur from impacts on Vesta. The production of impact melt is highly dependent on impact velocity (e.g., O'Keefe and Ahrens, 1977;Bjorkman and Holsapple, 1987;Pierazzo et al, 1997;Wünnemann et al, 2008). For impacts with a 'melt number' U 2 /E m greater than $ 30, where U is the impact velocity and E m is the internal energy at the critical shock pressure for melting, the volume of the melted region is significantly larger than the volume of the projectile and the melt volume follows a simple linear relationship in log-log space:…”

Section: Results Ii: Modeling Impact Melts On Vestamentioning

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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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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“…[46] Impact crater scaling laws predict that the SPA impact excavated through the crust and melted a potentially large volume of mantle material [Melosh, 1989;Pierazzo et al, 1997;Morrison, 1998;Potter et al, 2012;Vaughan and Head, 2013]. In this scenario, a thick layer of impact melt (~45 km) is predicted to line the inner portion of the basin [Morrison, 1998;Vaughan and Head, 2013].…”

Section: Compositional Differences Among Spa Mafic Peaksmentioning

confidence: 99%

Compositional heterogeneity of central peaks within the South Pole‐Aitken Basin

2013

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[1] Using high-spectral and -spatial resolution Moon Mineralogy Mapper data, we investigate compositional variations across the central peak structures of four impact craters within the South Pole-Aitken Basin (SPA). Two distinct causes of spectral diversity are observed. Spectral variations across the central peaks of Bhabha, Finsen, and Lyman are dominated by soil development, including the effects of space weathering and mixing with local materials. For these craters, the central peak structure is homogeneous in composition, although small compositional differences between the craters are observed. This group of craters is located within the estimated transient cavity of SPA, and their central uplifts exhibit similar mafic abundances. Therefore, it is plausible that they have all uplifted material associated with melts of the lower crust or upper mantle produced during the SPA impact. Compositional differences observed between the peaks of these craters reflect heterogeneities in the SPA subsurface, although the origin of this heterogeneity is uncertain. In contrast to these craters, Leeuwenhoek exhibits compositional heterogeneity across its central peak structure. The peak is areally dominated by feldspathic materials, interspersed with several smaller exposures exhibiting a mafic spectral signature. Leeuwenhoek is the largest crater included in the study and is located in a region of complex stratigraphy involving both crustal (feldspathic) and SPA (mafic melt and ejecta) materials. The compositional diversity observed in Leeuwenhoek's central peak indicates that kilometer-scale heterogeneities persist to depths of more than 10 km in this region.

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A Reevaluation of Impact Melt Production

Cited by 461 publications

References 17 publications

Melting in super-earths

Melting in super-earths

Lobate and flow-like features on asteroid Vesta

Compositional heterogeneity of central peaks within the South Pole‐Aitken Basin

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