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Jones MJ, Evans AJ, Johnson BC, Weller MB, Andrews-Hanna JC, Tikoo SM, Keane JT. A South Pole-Aitken impact origin of the lunar compositional asymmetry. SCIENCE ADVANCES 2022; 8:eabm8475. [PMID: 35394845 PMCID: PMC8993107 DOI: 10.1126/sciadv.abm8475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 02/22/2022] [Indexed: 06/14/2023]
Abstract
The formation of the largest and most ancient lunar impact basin, South Pole-Aitken (SPA), was a defining event in the Moon's evolution. Using numerical simulations, we show that widespread mantle heating from the SPA impact can catalyze the formation of the long-lived nearside-farside lunar asymmetry in incompatible elements and surface volcanic deposits, which has remained unexplained since its discovery in the Apollo era. The impact-induced heat drives hemisphere-scale mantle convection, which would sequester Th- and Ti-rich lunar magma ocean cumulates in the nearside hemisphere within a few hundred million years if they remain immediately beneath the lunar crust at the time of the SPA impact. A warm initial upper mantle facilitates generation of a pronounced compositional asymmetry consistent with the observed lunar asymmetry.
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Affiliation(s)
- Matt J. Jones
- Department of Earth, Environmental and Planetary Sciences, Brown University, Box 1846, 324 Brook Street, Providence, RI 02912, USA
| | - Alexander J. Evans
- Department of Earth, Environmental and Planetary Sciences, Brown University, Box 1846, 324 Brook Street, Providence, RI 02912, USA
| | - Brandon C. Johnson
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
| | - Matthew B. Weller
- Department of Earth, Environmental and Planetary Sciences, Brown University, Box 1846, 324 Brook Street, Providence, RI 02912, USA
- Lunar and Planetary Institute, Houston, TX 77058, USA
| | | | - Sonia M. Tikoo
- Department of Geophysics, Stanford University, Stanford, CA 94305, USA
| | - James T. Keane
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
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Padovan S, Tosi N, Plesa AC, Ruedas T. Impact-induced changes in source depth and volume of magmatism on Mercury and their observational signatures. Nat Commun 2017; 8:1945. [PMID: 29208890 PMCID: PMC5717040 DOI: 10.1038/s41467-017-01692-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 10/10/2017] [Indexed: 11/09/2022] Open
Abstract
Mercury’s crust is mostly the result of partial melting in the mantle associated with solid-state convection. Large impacts induce additional melting by generating subsurface thermal anomalies. By numerically investigating the geodynamical effects of impacts, here we show that impact-generated thermal anomalies interact with the underlying convection modifying the source depth of melt and inducing volcanism that can significantly postdate the impact depending on the impact time and location with respect to the underlying convection pattern. We can reproduce the volume and time of emplacement of the melt sheets in the interior of Caloris and Rembrandt if at about 3.7–3.8 Ga convection in the mantle of Mercury was weak, an inference corroborated by the dating of the youngest large volcanic provinces. The source depth of the melt sheets is located in the stagnant lid, a volume of the mantle that never participated in convection and may contain pristine mantle material. Mantle partial melting produced the volcanic crust of Mercury. Here, the authors numerically model the formation of post-impact melt sheets and find that mantle convection was weak at around 3.7–3.8 Ga and that the melt sheets of Caloris and Rembrandt may contain partial melting of pristine mantle material.
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Affiliation(s)
- Sebastiano Padovan
- Department of Planetary Physics, German Aerospace Center, 12489, Berlin, Germany.
| | - Nicola Tosi
- Department of Planetary Physics, German Aerospace Center, 12489, Berlin, Germany.,Department of Astronomy and Astrophysics, Technische Universität Berlin, 10623, Berlin, Germany
| | - Ana-Catalina Plesa
- Department of Planetary Physics, German Aerospace Center, 12489, Berlin, Germany
| | - Thomas Ruedas
- Department of Planetary Physics, German Aerospace Center, 12489, Berlin, Germany.,Institute of Planetology, University of Münster, 48149, Münster, Germany
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Kuang W, Jiang W, Roberts J, Frey HV. Could giant basin-forming impacts have killed Martian dynamo? GEOPHYSICAL RESEARCH LETTERS 2014; 41:8006-8012. [PMID: 26074641 PMCID: PMC4459199 DOI: 10.1002/2014gl061818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 10/24/2014] [Indexed: 06/04/2023]
Abstract
The observed strong remanent crustal magnetization at the surface of Mars suggests an active dynamo in the past and ceased to exist around early to middle Noachian era, estimated by examining remagnetization strengths in extant and buried impact basins. We investigate whether the Martian dynamo could have been killed by these large basin-forming impacts, via numerical simulation of subcritical dynamos with impact-induced thermal heterogeneity across the core-mantle boundary. We find that subcritical dynamos are prone to the impacts centered on locations within 30° of the equator but can easily survive those at higher latitudes. Our results further suggest that magnetic timing places a strong constraint on postimpact polar reorientation, e.g., a minimum 16° polar reorientation is needed if Utopia is the dynamo killer.
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Affiliation(s)
- W Kuang
- Planetary Geodynamics Laboratory, NASA Goddard Space Flight CenterGreenbelt, Maryland, USA
| | - W Jiang
- Science Systems and Applications, Inc.Lanham, Maryland, USA
| | - J Roberts
- Johns Hopkins University Applied Physics LaboratoryLaurel, Maryland, USA
| | - H V Frey
- Planetary Geodynamics Laboratory, NASA Goddard Space Flight CenterGreenbelt, Maryland, USA
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Marchi S, Bottke WF, Elkins-Tanton LT, Bierhaus M, Wuennemann K, Morbidelli A, Kring DA. Widespread mixing and burial of Earth's Hadean crust by asteroid impacts. Nature 2014; 511:578-82. [PMID: 25079556 DOI: 10.1038/nature13539] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/23/2014] [Indexed: 11/09/2022]
Abstract
The history of the Hadean Earth (∼4.0-4.5 billion years ago) is poorly understood because few known rocks are older than ∼3.8 billion years old. The main constraints from this era come from ancient submillimetre zircon grains. Some of these zircons date back to ∼4.4 billion years ago when the Moon, and presumably the Earth, was being pummelled by an enormous flux of extraterrestrial bodies. The magnitude and exact timing of these early terrestrial impacts, and their effects on crustal growth and evolution, are unknown. Here we provide a new bombardment model of the Hadean Earth that has been calibrated using existing lunar and terrestrial data. We find that the surface of the Hadean Earth was widely reprocessed by impacts through mixing and burial by impact-generated melt. This model may explain the age distribution of Hadean zircons and the absence of early terrestrial rocks. Existing oceans would have repeatedly boiled away into steam atmospheres as a result of large collisions as late as about 4 billion years ago.
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Affiliation(s)
- S Marchi
- Southwest Research Institute, Boulder, Colorado 80302, USA
| | - W F Bottke
- Southwest Research Institute, Boulder, Colorado 80302, USA
| | - L T Elkins-Tanton
- 1] Carnegie Institution for Science, Washington DC 20015, USA [2] School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA
| | - M Bierhaus
- Museum für Naturkunde, Berlin 10115, Germany
| | | | - A Morbidelli
- Observatoire de la Côte d'Azur, Nice 06304, France
| | - D A Kring
- Universities Space Research Association, Lunar and Planetary Institute, Houston, Texas 77058, USA
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Stixrude L. Melting in super-earths. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130076. [PMID: 24664915 DOI: 10.1098/rsta.2013.0076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We examine the possible extent of melting in rock-iron 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 super-earths. 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 super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth 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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Affiliation(s)
- Lars Stixrude
- Department of Earth Sciences, University College London, , Gower St, London WC1E 6BT, UK
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Roberts JH, Lillis RJ, Manga M. Giant impacts on early Mars and the cessation of the Martian dynamo. ACTA ACUST UNITED AC 2009. [DOI: 10.1029/2008je003287] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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