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A Review of the Lunar 182Hf-182W Isotope System Research. MINERALS 2022. [DOI: 10.3390/min12060759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In recent years, the extinct nuclide 182Hf-182W system has been developed as an essential tool to date and trace the lunar origin and evolution. Despite a series of achievements, controversies and problems exist. As a review, this paper details the application principles of the 182Hf-182W isotope system and summarizes the research development on W isotopes of the Moon. A significant radiogenic ε182W excess of 0.24 ± 0.01 was found in the lunar mantle, leading to heated debates. There are three main explanations for the origin of the excess, including (1) radioactive origin; (2) the mantle of the Moon-forming impactor; and (3) disproportional late accretion to the Earth and the Moon. Debates on these explanations have revealed different views on lunar age. The reported ages of the Moon are mainly divided into two views: an early Moon (30–70 Ma after the solar system formation); and a late Moon (>70 Ma after the solar system formation). This paper discusses the possible effects on lunar 182W composition, including the Moon-forming impactor, late veneer, and Oceanus Procellarum-forming projectile. Finally, the unexpected isotopic similarities between the Earth and Moon are discussed.
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2
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Chu Z. Analytical Methods for Os Isotope Ratios and Re-PGE Mass Fractions in Geological Samples. Front Chem 2021; 8:615839. [PMID: 33681141 PMCID: PMC7925887 DOI: 10.3389/fchem.2020.615839] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 12/21/2020] [Indexed: 11/26/2022] Open
Abstract
The recent advances in analytical methods of Re-Os and PGE in geological materials including sample dissolution, chemical separation, mass spectrometric determinations, as well as the developments of matrix-matched reference materials for data quality control are thoroughly reviewed. Further, the in-situ measurement methods for Re-PGE mass fractions and 187Os/188Os ratios, as well as the measurement methods for stable isotope ratios of Re and PGE are also briefly reviewed. This review stands as a comprehensive reference for researchers to consider in the development of measurement methods for Re-PGE mass fractions and 187Os/188Os ratios in geological materials.
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Affiliation(s)
- Zhuyin Chu
- State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
- Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing, China
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3
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Benner SA, Bell EA, Biondi E, Brasser R, Carell T, Kim H, Mojzsis SJ, Omran A, Pasek MA, Trail D. When Did Life Likely Emerge on Earth in an RNA‐First Process? CHEMSYSTEMSCHEM 2020. [DOI: 10.1002/syst.201900035] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Steven A. Benner
- Foundation for Applied Molecular Evolution Alachua FL USA
- Firebird Biomolecular Sciences LLC Alachua FL USA
| | - Elizabeth A. Bell
- Department of Earth, Planetary, and Space SciencesUniversity of California Los Angeles USA
| | - Elisa Biondi
- Foundation for Applied Molecular Evolution Alachua FL USA
| | - Ramon Brasser
- Earth Life Science InstituteTokyo Institute of Technology Tokyo Japan
| | - Thomas Carell
- Fakultät für Chemie und PharmazieLudwig-Maximilians-Universität München Germany
| | | | - Stephen J. Mojzsis
- Department of Geological SciencesUniversity of Colorado Boulder CO USA
- Hungarian Academy of Sciences Budapest Hungary
| | - Arthur Omran
- School of GeosciencesUniversity of South Florida Tampa, FL USA
| | | | - Dustin Trail
- Department of Earth and Environmental SciencesUniversity of Rochester Rochester NY USA
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Zhu MH, Artemieva N, Morbidelli A, Yin QZ, Becker H, Wünnemann K. Reconstructing the late-accretion history of the Moon. Nature 2019; 571:226-229. [DOI: 10.1038/s41586-019-1359-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 05/23/2019] [Indexed: 11/10/2022]
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Day JMD, Moynier F, Shearer CK. Late-stage magmatic outgassing from a volatile-depleted Moon. Proc Natl Acad Sci U S A 2017; 114:9547-9551. [PMID: 28827322 PMCID: PMC5594690 DOI: 10.1073/pnas.1708236114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The abundance of volatile elements and compounds, such as zinc, potassium, chlorine, and water, provide key evidence for how Earth and the Moon formed and evolved. Currently, evidence exists for a Moon depleted in volatile elements, as well as reservoirs within the Moon with volatile abundances like Earth's depleted upper mantle. Volatile depletion is consistent with catastrophic formation, such as a giant impact, whereas a Moon with Earth-like volatile abundances suggests preservation of these volatiles, or addition through late accretion. We show, using the "Rusty Rock" impact melt breccia, 66095, that volatile enrichment on the lunar surface occurred through vapor condensation. Isotopically light Zn (δ66Zn = -13.7‰), heavy Cl (δ37Cl = +15‰), and high U/Pb supports the origin of condensates from a volatile-poor internal source formed during thermomagmatic evolution of the Moon, with long-term depletion in incompatible Cl and Pb, and lesser depletion of more-compatible Zn. Leaching experiments on mare basalt 14053 demonstrate that isotopically light Zn condensates also occur on some mare basalts after their crystallization, confirming a volatile-depleted lunar interior source with homogeneous δ66Zn ≈ +1.4‰. Our results show that much of the lunar interior must be significantly depleted in volatile elements and compounds and that volatile-rich rocks on the lunar surface formed through vapor condensation. Volatiles detected by remote sensing on the surface of the Moon likely have a partially condensate origin from its interior.
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Affiliation(s)
- James M D Day
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244;
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, 75005 Paris, France
| | - Frédéric Moynier
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, 75005 Paris, France
- Institut Universitaire de France, 75005 Paris, France
| | - Charles K Shearer
- Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131
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7
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Raymond SN, Izidoro A. The empty primordial asteroid belt. SCIENCE ADVANCES 2017; 3:e1701138. [PMID: 28924609 PMCID: PMC5597311 DOI: 10.1126/sciadv.1701138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 08/14/2017] [Indexed: 05/23/2023]
Abstract
The asteroid belt contains less than a thousandth of Earth's mass and is radially segregated, with S-types dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having formed empty, without any planetesimals between Mars and Jupiter's present-day orbits. This is consistent with models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside 1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a preference for the inner main belt. C-types are implanted from the outside, as the giant planets' gas accretion destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid belt may thus represent a repository for planetary leftovers that accreted across the solar system but not in the belt itself.
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Affiliation(s)
- Sean N. Raymond
- Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
| | - Andre Izidoro
- Laboratoire d’Astrophysique de Bordeaux, Université de Bordeaux, CNRS, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
- Universidade Estadual Paulista (UNESP), Grupo de Dinamica Orbital e Planetologia, Guaratinguetá, CEP 12.516-410, São Paulo, Brazil
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Abstract
The short-lived Hf-W isotope system has a wide range of important applications in cosmochemistry and geochemistry. The siderophile behavior of W, combined with the lithophile nature of Hf, makes the system uniquely useful as a chronometer of planetary accretion and differentiation. Tungsten isotopic data for meteorites show that the parent bodies of some differentiated meteorites accreted within 1 million years after Solar System formation. Melting and differentiation on these bodies took ~1-3 million years and was fueled by decay of 26Al. The timescale for accretion and core formation increases with planetary mass and is ~10 million years for Mars and >34 million years for Earth. The nearly identical 182W compositions for the mantles of the Moon and Earth are difficult to explain in current models for the formation of the Moon. Terrestrial samples with ages spanning ~4 billion years reveal small 182W variations within the silicate Earth, demonstrating that traces of Earth's earliest formative period have been preserved throughout Earth's history.
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Affiliation(s)
- Thorsten Kleine
- Institut für Planetologie, University of Münster, 48149 Muenster, Germany
| | - Richard J Walker
- Department of Geology, University of Maryland, College Park, Maryland 20742
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Sleep NH. Asteroid bombardment and the core of Theia as possible sources for the Earth's late veneer component. GEOCHEMISTRY, GEOPHYSICS, GEOSYSTEMS : G(3) 2016; 17:2623-2642. [PMID: 35095346 PMCID: PMC8793101 DOI: 10.1002/2016gc006305] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The silicate Earth contains Pt-group elements in roughly chondritic relative ratios, but with absolute concentrations <1% chondrite. This veneer implies addition of chondrite-like material with 0.3-0.7% mass of the Earth's mantle or an equivalent planet-wide thickness of 5-20 km. The veneer thickness, 200-300 m, within the lunar crust and mantle is much less. One hypothesis is that the terrestrial veneer arrived after the moon-forming impact within a few large asteroids that happened to miss the smaller Moon. Alternatively, most of terrestrial veneer came from the core of the moon-forming impactor, Theia. The Moon then likely contains iron from Theia's core. Mass balances lend plausibility. The lunar core mass is ~1.6 × 1021 kg and the excess FeO component in the lunar mantle is 1.3-3.5 × 1021 kg as Fe, totaling 3-5 × 1021 kg or a few percent of Theia's core. This mass is comparable to the excess Fe of 2.3-10 × 1021 kg in the Earth's mantle inferred from the veneer component. Chemically in this hypothesis, Fe metal from Theia's core entered the Moon-forming disk. H2O and Fe2O3 in the disk oxidized part of the Fe, leaving the lunar mantle near a Fe-FeO buffer. The remaining iron metal condensed, gathered Pt-group elements eventually into the lunar core. The silicate Moon is strongly depleted in Pt-group elements. In contrast, the Earth's mantle contained excess oxidants, H2O and Fe2O3, which quantitatively oxidized the admixed Fe from Theia's core, retaining Pt-group elements. In this hypothesis, asteroid impacts were relatively benign with ~1 terrestrial event that left only thermophile survivors.
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Affiliation(s)
- Norman H Sleep
- Department of Geophysics, Stanford University, Stanford, California, USA
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Barnes JJ, Kring DA, Tartèse R, Franchi IA, Anand M, Russell SS. An asteroidal origin for water in the Moon. Nat Commun 2016; 7:11684. [PMID: 27244672 PMCID: PMC4895054 DOI: 10.1038/ncomms11684] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 04/19/2016] [Indexed: 11/09/2022] Open
Abstract
The Apollo-derived tenet of an anhydrous Moon has been contested following measurement of water in several lunar samples that require water to be present in the lunar interior. However, significant uncertainties exist regarding the flux, sources and timing of water delivery to the Moon. Here we address those fundamental issues by constraining the mass of water accreted to the Moon and modelling the relative proportions of asteroidal and cometary sources for water that are consistent with measured isotopic compositions of lunar samples. We determine that a combination of carbonaceous chondrite-type materials were responsible for the majority of water (and nitrogen) delivered to the Earth-Moon system. Crucially, we conclude that comets containing water enriched in deuterium contributed significantly <20% of the water in the Moon. Therefore, our work places important constraints on the types of objects impacting the Moon ∼4.5-4.3 billion years ago and on the origin of water in the inner Solar System.
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Affiliation(s)
- Jessica J Barnes
- Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | - David A Kring
- Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas 77058, USA
| | - Romain Tartèse
- Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
- Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Muséum National d'Histoire Naturelle, Sorbonne Universités, CNRS, UMPC &IRD, Paris 75005, France
| | - Ian A Franchi
- Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | - Mahesh Anand
- Department of Physical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
- Earth Sciences Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | - Sara S Russell
- Earth Sciences Department, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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Day JM, Walker RJ. Highly siderophile element depletion in the Moon. EARTH AND PLANETARY SCIENCE LETTERS 2015; 423:114-124. [PMID: 34465923 PMCID: PMC8404368 DOI: 10.1016/j.epsl.2015.05.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Coupled 187Os/188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance data are reported for Apollo 12 (12005, 12009, 12019, 12022, 12038, 12039, 12040), Apollo 15 (15555) and Apollo 17 (70135) mare basalts, along with mare basalt meteorites La Paz icefield (LAP) 04841 and Miller Range (MIL) 05035. The most magnesian samples have chondrite-relative HSE abundances and chondritic measured and calculated initial 187Os/188Os, with mare basalts having consistently low HSE abundances at ~2 ×10-5 to 2 ×10-7 the chondritic abundance. The lower and more fractionated HSE compositions of evolved mare basalts can be reproduced with bulk-partition coefficients of ~2 for Os, Ir, Ru, Pt and Pd and ~1.5 for Re. Lunar mare basalt bulk-partition coefficients are probably higher than for terrestrial melts as a result of more reducing conditions, leading to increased HSE compatibility. The chondritic-relative abundances and chondritic 187Os/188Os of the most primitive high-MgO mare basalts cannot be explained through regolith contamination during emplacement at the lunar surface. Instead, mare basalt compositions can be modelled as representing ~5-11% partial melting of metal-free sources with low Os, Ir, Ru, Pd (~0.1 ng g-1), Pt (~0.2 ng g-1) Re (~0.01 ng g-1) and S, with sulphide-melt partitioning between 1000 and 10000. Apollo 12 olivine-, pigeonite- and ilmenite normative mare basalts define an imprecise 187Re-187Os age of 3.0 ±0.6 Ga. This age is within uncertainty of 147Sm-143Nd ages for the same samples and the isochron yields an initial 187Os/188Os of 0.109 ±0.008. The Os isotopic composition of the Apollo 12 source indicates that the lunar mantle source of these rocks evolved with Re/Os within ~10% of chondrite meteorites from the time that the mantle source became a system closed to siderophile additions to the time that the basalts erupted. The similarity in absolute HSE abundances between mare basalts from the Apollo 12, 15 and 17 sites, and from unknown regions of the Moon (La Paz mare basalts, MIL 05035) indicates relatively homogeneous and low HSE abundances within the lunar interior. Low absolute HSE abundances and chondritic Re/Os of mare basalts are consistent with ~0.02% late accretion addition that was added prior to the formation of the lunar crust and significantly prior to cessation of lunar mantle differentiation (>4.4 Ga) to enable efficient mixing and homogenization. The HSE abundances are also consistent with the observed, small 182W excess (20 ppm) in the bulk silicate Moon relative to the bulk silicate Earth.
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Affiliation(s)
- James M.D. Day
- Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0244, USA
| | - Richard J. Walker
- Department of Geology, University of Maryland, College Park, MD 20742, USA
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Tungsten isotopic evidence for disproportional late accretion to the Earth and Moon. Nature 2015; 520:530-3. [PMID: 25855299 DOI: 10.1038/nature14355] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 02/24/2015] [Indexed: 11/09/2022]
Abstract
Characterization of the hafnium-tungsten systematics ((182)Hf decaying to (182)W and emitting two electrons with a half-life of 8.9 million years) of the lunar mantle will enable better constraints on the timescale and processes involved in the currently accepted giant-impact theory for the formation and evolution of the Moon, and for testing the late-accretion hypothesis. Uniform, terrestrial-mantle-like W isotopic compositions have been reported among crystallization products of the lunar magma ocean. These observations were interpreted to reflect formation of the Moon and crystallization of the lunar magma ocean after (182)Hf was no longer extant-that is, more than about 60 million years after the Solar System formed. Here we present W isotope data for three lunar samples that are more precise by a factor of ≥4 than those previously reported. The new data reveal that the lunar mantle has a well-resolved (182)W excess of 20.6 ± 5.1 parts per million (±2 standard deviations), relative to the modern terrestrial mantle. The offset between the mantles of the Moon and the modern Earth is best explained by assuming that the W isotopic compositions of the two bodies were identical immediately following formation of the Moon, and that they then diverged as a result of disproportional late accretion to the Earth and Moon. One implication of this model is that metal from the core of the Moon-forming impactor must have efficiently stripped the Earth's mantle of highly siderophile elements on its way to merge with the terrestrial core, requiring a substantial, but still poorly defined, level of metal-silicate equilibration.
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14
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Lunar tungsten isotopic evidence for the late veneer. Nature 2015; 520:534-7. [PMID: 25855296 DOI: 10.1038/nature14360] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 02/25/2015] [Indexed: 11/09/2022]
Abstract
According to the most widely accepted theory of lunar origin, a giant impact on the Earth led to the formation of the Moon, and also initiated the final stage of the formation of the Earth's core. Core formation should have removed the highly siderophile elements (HSE) from Earth's primitive mantle (that is, the bulk silicate Earth), yet HSE abundances are higher than expected. One explanation for this overabundance is that a 'late veneer' of primitive material was added to the bulk silicate Earth after the core formed. To test this hypothesis, tungsten isotopes are useful for two reasons: first, because the late veneer material had a different (182)W/(184)W ratio to that of the bulk silicate Earth, and second, proportionally more material was added to the Earth than to the Moon. Thus, if a late veneer did occur, the bulk silicate Earth and the Moon must have different (182)W/(184)W ratios. Moreover, the Moon-forming impact would also have created (182)W differences because the mantle and core material of the impactor with distinct (182)W/(184)W would have mixed with the proto-Earth during the giant impact. However the (182)W/(184)W of the Moon has not been determined precisely enough to identify signatures of a late veneer or the giant impact. Here, using more-precise measurement techniques, we show that the Moon exhibits a (182)W excess of 27 ± 4 parts per million over the present-day bulk silicate Earth. This excess is consistent with the expected (182)W difference resulting from a late veneer with a total mass and composition inferred from HSE systematics. Thus, our data independently show that HSE abundances in the bulk silicate Earth were established after the giant impact and core formation, as predicted by the late veneer hypothesis. But, unexpectedly, we find that before the late veneer, no (182)W anomaly existed between the bulk silicate Earth and the Moon, even though one should have arisen through the giant impact. The origin of the homogeneous (182)W of the pre-late-veneer bulk silicate Earth and the Moon is enigmatic and constitutes a challenge to current models of lunar origin.
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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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Walker RJ. Siderophile element constraints on the origin of the Moon. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130258. [PMID: 25114313 PMCID: PMC4128271 DOI: 10.1098/rsta.2013.0258] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Discovery of small enrichments in (182)W/(184)W in some Archaean rocks, relative to modern mantle, suggests both exogeneous and endogenous modifications to highly siderophile element (HSE) and moderately siderophile element abundances in the terrestrial mantle. Collectively, these isotopic enrichments suggest the formation of chemically fractionated reservoirs in the terrestrial mantle that survived the putative Moon-forming giant impact, and also provide support for the late accretion hypothesis. The lunar mantle sources of volcanic glasses and basalts were depleted in HSEs relative to the terrestrial mantle by at least a factor of 20. The most likely explanations for the disparity between the Earth and Moon are either that the Moon received a disproportionately lower share of late accreted materials than the Earth, such as may have resulted from stochastic late accretion, or the major phase of late accretion occurred prior to the Moon-forming event, and the putative giant impact led to little drawdown of HSEs to the Earth's core. High precision determination of the (182)W isotopic composition of the Moon can help to resolve this issue.
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Affiliation(s)
- Richard J Walker
- Isotope Geochemistry Laboratory, Department of Geology, University of Maryland, College Park, MD 20742, USA
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17
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Day JMD, Moynier F. Evaporative fractionation of volatile stable isotopes and their bearing on the origin of the Moon. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130259. [PMID: 25114311 PMCID: PMC4128272 DOI: 10.1098/rsta.2013.0259] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Moon is depleted in volatile elements relative to the Earth and Mars. Low abundances of volatile elements, fractionated stable isotope ratios of S, Cl, K and Zn, high μ ((238)U/(204)Pb) and long-term Rb/Sr depletion are distinguishing features of the Moon, relative to the Earth. These geochemical characteristics indicate both inheritance of volatile-depleted materials that formed the Moon and planets and subsequent evaporative loss of volatile elements that occurred during lunar formation and differentiation. Models of volatile loss through localized eruptive degassing are not consistent with the available S, Cl, Zn and K isotopes and abundance data for the Moon. The most probable cause of volatile depletion is global-scale evaporation resulting from a giant impact or a magma ocean phase where inefficient volatile loss during magmatic convection led to the present distribution of volatile elements within mantle and crustal reservoirs. Problems exist for models of planetary volatile depletion following giant impact. Most critically, in this model, the volatile loss requires preferential delivery and retention of late-accreted volatiles to the Earth compared with the Moon. Different proportions of late-accreted mass are computed to explain present-day distributions of volatile and moderately volatile elements (e.g. Pb, Zn; 5 to >10%) relative to highly siderophile elements (approx. 0.5%) for the Earth. Models of early magma ocean phases may be more effective in explaining the volatile loss. Basaltic materials (e.g. eucrites and angrites) from highly differentiated airless asteroids are volatile-depleted, like the Moon, whereas the Earth and Mars have proportionally greater volatile contents. Parent-body size and the existence of early atmospheres are therefore likely to represent fundamental controls on planetary volatile retention or loss.
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Affiliation(s)
- James M D Day
- Scripps Isotope Geochemistry Laboratory, Geosciences Research Division, Scripps Institution of Oceanography, La Jolla, CA 92093-0244, USA
| | - Frederic Moynier
- Institut de Physique du Globe de Paris, Université Paris Diderot, Sorbonne Paris Cité, 1 rue Jussieu, 75005 Paris, France
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Melosh HJ. New approaches to the Moon's isotopic crisis. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2014; 372:20130168. [PMID: 25114301 PMCID: PMC4128260 DOI: 10.1098/rsta.2013.0168] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Recent comparisons of the isotopic compositions of the Earth and the Moon show that, unlike nearly every other body known in the Solar System, our satellite's isotopic ratios are nearly identical to the Earth's for nearly every isotopic system. The Moon's chemical make-up, however, differs from the Earth's in its low volatile content and perhaps in the elevated abundance of oxidized iron. This surprising situation is not readily explained by current impact models of the Moon's origin and offers a major clue to the Moon's formation, if we only could understand it properly. Current ideas to explain this similarity range from assuming an impactor with the same isotopic composition as the Earth to postulating a pure ice impactor that completely vaporized upon impact. Several recent proposals follow from the suggestion that the Earth-Moon system may have lost a great deal of angular momentum during early resonant interactions. The isotopic constraint may be the most stringent test yet for theories of the Moon's origin.
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Affiliation(s)
- H J Melosh
- Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN 47907, USA Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA Aeronautical and Astronautical Engineering Departments, Purdue University, West Lafayette, IN 47907, USA
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Jacobson SA, Morbidelli A, Raymond SN, O'Brien DP, Walsh KJ, Rubie DC. Highly siderophile elements in Earth’s mantle as a clock for the Moon-forming impact. Nature 2014; 508:84-7. [DOI: 10.1038/nature13172] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 02/17/2014] [Indexed: 11/09/2022]
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20
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Saal AE, Hauri EH, Van Orman JA, Rutherford MJ. Hydrogen isotopes in lunar volcanic glasses and melt inclusions reveal a carbonaceous chondrite heritage. Science 2013; 340:1317-20. [PMID: 23661641 DOI: 10.1126/science.1235142] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Water is perhaps the most important molecule in the solar system, and determining its origin and distribution in planetary interiors has important implications for understanding the evolution of planetary bodies. Here we report in situ measurements of the isotopic composition of hydrogen dissolved in primitive volcanic glass and olivine-hosted melt inclusions recovered from the Moon by the Apollo 15 and 17 missions. After consideration of cosmic-ray spallation and degassing processes, our results demonstrate that lunar magmatic water has an isotopic composition that is indistinguishable from that of the bulk water in carbonaceous chondrites and similar to that of terrestrial water, implying a common origin for the water contained in the interiors of Earth and the Moon.
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Affiliation(s)
- Alberto E Saal
- Department of Geological Sciences, Brown University, Providence, RI 02912, USA.
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21
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Dale CW, Burton KW, Greenwood RC, Gannoun A, Wade J, Wood BJ, Pearson DG. Late accretion on the earliest planetesimals revealed by the highly siderophile elements. Science 2012; 336:72-5. [PMID: 22491852 DOI: 10.1126/science.1214967] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Late accretion of primitive chondritic material to Earth, the Moon, and Mars, after core formation had ceased, can account for the absolute and relative abundances of highly siderophile elements (HSEs) in their silicate mantles. Here we show that smaller planetesimals also possess elevated HSE abundances in chondritic proportions. This demonstrates that late addition of chondritic material was a common feature of all differentiated planets and planetesimals, irrespective of when they accreted; occurring ≤5 to ≥150 million years after the formation of the solar system. Parent-body size played a role in producing variations in absolute HSE abundances among these bodies; however, the oxidation state of the body exerted the major control by influencing the extent to which late-accreted material was mixed into the silicate mantle rather than removed to the core.
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22
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Bottke WF, Walker RJ, Day JMD, Nesvorny D, Elkins-Tanton L. Stochastic Late Accretion to Earth, the Moon, and Mars. Science 2010; 330:1527-30. [DOI: 10.1126/science.1196874] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Core formation should have stripped the terrestrial, lunar, and martian mantles
of highly siderophile elements (HSEs). Instead, each world has disparate, yet
elevated HSE abundances. Late accretion may offer a solution, provided that
≥0.5% Earth masses of broadly chondritic planetesimals reach
Earth’s mantle and that ~10 and ~1200 times less mass goes to Mars and
the Moon, respectively. We show that leftover planetesimal populations dominated
by massive projectiles can explain these additions, with our inferred size
distribution matching those derived from the inner asteroid belt, ancient
martian impact basins, and planetary accretion models. The largest late
terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially
modified Earth’s obliquity by ~10°, whereas those for the Moon, at
~250 to 300 kilometers, may have delivered water to its mantle.
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Abstract
For the past 40 years, the Moon has been described as nearly devoid of indigenous water; however, evidence for water both on the lunar surface and within the lunar interior have recently emerged, calling into question this long-standing lunar dogma. In the present study, hydroxyl (as well as fluoride and chloride) was analyzed by secondary ion mass spectrometry in apatite [Ca(5)(PO(4))(3)(F,Cl,OH)] from three different lunar samples in order to obtain quantitative constraints on the abundance of water in the lunar interior. This work confirms that hundreds to thousands of ppm water (of the structural form hydroxyl) is present in apatite from the Moon. Moreover, two of the studied samples likely had water preserved from magmatic processes, which would qualify the water as being indigenous to the Moon. The presence of hydroxyl in apatite from a number of different types of lunar rocks indicates that water may be ubiquitous within the lunar interior, potentially as early as the time of lunar formation. The water contents analyzed for the lunar apatite indicate minimum water contents of their lunar source region to range from 64 ppb to 5 ppm H(2)O. This lower limit range of water contents is at least two orders of magnitude greater than the previously reported value for the bulk Moon, and the actual source region water contents could be significantly higher.
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Early formation of evolved asteroidal crust. Nature 2009; 457:179-82. [PMID: 19129845 DOI: 10.1038/nature07651] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2008] [Accepted: 11/17/2008] [Indexed: 11/08/2022]
Abstract
Mechanisms for the formation of crust on planetary bodies remain poorly understood. It is generally accepted that Earth's andesitic continental crust is the product of plate tectonics, whereas the Moon acquired its feldspar-rich crust by way of plagioclase flotation in a magma ocean. Basaltic meteorites provide evidence that, like the terrestrial planets, some asteroids generated crust and underwent large-scale differentiation processes. Until now, however, no evolved felsic asteroidal crust has been sampled or observed. Here we report age and compositional data for the newly discovered, paired and differentiated meteorites Graves Nunatak (GRA) 06128 and GRA 06129. These meteorites are feldspar-rich, with andesite bulk compositions. Their age of 4.52 +/- 0.06 Gyr demonstrates formation early in Solar System history. The isotopic and elemental compositions, degree of metamorphic re-equilibration and sulphide-rich nature of the meteorites are most consistent with an origin as partial melts from a volatile-rich, oxidized asteroid. GRA 06128 and 06129 are the result of a newly recognized style of evolved crust formation, bearing witness to incomplete differentiation of their parent asteroid and to previously unrecognized diversity of early-formed materials in the Solar System.
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Halliday AN. A young Moon-forming giant impact at 70-110 million years accompanied by late-stage mixing, core formation and degassing of the Earth. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2008; 366:4163-81. [PMID: 18826916 DOI: 10.1098/rsta.2008.0209] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
New W isotope data for lunar metals demonstrate that the Moon formed late in isotopic equilibrium with the bulk silicate Earth (BSE). On this basis, lunar Sr isotope data are used to define the former composition of the Earth and hence the Rb-Sr age of the Moon, which is 4.48+/-0.02Ga, or 70-110Ma (million years) after the start of the Solar System. This age is significantly later than had been deduced from W isotopes based on model assumptions or isotopic effects now known to be cosmogenic. The Sr age is in excellent agreement with earlier estimates based on the time of lunar Pb loss and the age of the early lunar crust (4.46+/-0.04Ga). Similar ages for the BSE are recorded by xenon and lead-lead, providing evidence of catastrophic terrestrial degassing, atmospheric blow-off and significant late core formation accompanying the ca 100Ma giant impact. Agreement between the age of the Moon based on the Earth's Rb/Sr and the lead-lead age of the Moon is consistent with no major losses of moderately volatile elements from the Earth during the giant impact. The W isotopic composition of the BSE can be explained by end member models of (i) gradual accretion with a mean life of roughly 35Ma or (ii) rapid growth with a mean life of roughly 10Ma, followed by a significant hiatus prior to the giant impact. The former assumes that approximately 60 per cent of the incoming metal from impactors is added directly to the core during accretion. The latter includes complete mixing of all the impactor material into the BSE during accretion. The identical W isotopic composition of the Moon and the BSE limits the amount of material that can be added as a late veneer to the Earth after the giant impact to less than 0.3+/-0.3 per cent of ordinary chondrite or less than 0.5+/-0.6 per cent CI carbonaceous chondrite based on their known W isotopic compositions. Neither of these on their own is sufficient to explain the inventories of both refractory siderophiles such as platinum group elements and rhenium, and volatiles such as sulphur, carbon and water.
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Affiliation(s)
- Alex N Halliday
- Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK.
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