Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities

Lock, S. J.; Bermingham, K. R.; Parai, Rita; Boyet, Maud

doi:10.1007/s11214-020-00729-z

Cited by 25 publications

(18 citation statements)

References 260 publications

(414 reference statements)

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“…If  sin E k factors are held constant at present-day values, a backwards extrapolation in time yields the "Gerstenkorn event," a collision between Earth and Moon at about 1.6 Ga (Bills & Ray, 1999;Gerstenkorn, 1955Gerstenkorn, , 19671969;Lambeck, 1977). If the Gerstenkorn event had taken place, the Moon would have an age of only 1.6 Ga, much less than the 4.40-4.54 Ga age of the Earth-Moon system extrapolated from geochemical and geochronological evidence (e.g., Barboni et al, 2017;Borg et al, 2011;Kruijer & Kleine, 2017;Lock et al, 2020;Maurice et al, 2020). Therefore, the  sin E k factors must have been lower throughout most of Earth-Moon history.…”

Section: Tidal Energy Dissipationmentioning

confidence: 99%

Long‐Term Earth‐Moon Evolution With High‐Level Orbit and Ocean Tide Models

et al. 2021

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Tides and Earth-Moon system evolution are coupled over geological time. Tidal energy dissipation on Earth slows  Earth Es rotation rate, increases obliquity, lunar orbit semi-major axis and eccentricity, and decreases lunar inclination. Tidal and core-mantle boundary dissipation within the Moon decrease inclination, eccentricity and semi-major axis. Here we integrate the Earth-Moon system backwards for 4.5 Ga with orbital dynamics and explicit ocean tide models that are "high-level" (i.e., not idealized). To account for uncertain plate tectonic histories, we employ Monte Carlo simulations, with tidal energy dissipation rates (normalized relative to astronomical forcing parameters) randomly selected from ocean tide simulations with modern ocean basin geometry and with 55, 116, and 252 Ma reconstructed basin paleogeometries. The normalized dissipation rates depend upon basin geometry and  Earth E s rotation rate. Faster Earth rotation generally yields lower normalized dissipation rates. The Monte Carlo results provide a spread of possible early values for the Earth-Moon system parameters. Of consequence for ocean circulation and climate, absolute (un-normalized) ocean tidal energy dissipation rates on the early Earth may have exceeded  today E s rate due to a closer Moon. Prior to  E 3 Ga, evolution of inclination and eccentricity is dominated by tidal and core-mantle boundary dissipation within the Moon, which yield high lunar orbit inclinations in the early Earth-Moon system. A drawback for our results is that the semi-major axis does not collapse to near-zero values at 4.5 Ga, as indicated by most lunar formation models. Additional processes, missing from our current efforts, are discussed as topics for future investigation. Plain Language Summary Tidal dissipation ins oceans and solid body cause the distance to the Moon and the length of day to increase over time. Tides also change the eccentricity and tilt of the lunar orbit, and  Earth E s obliquity (the tilt between the equator plane and the ecliptic plane of our orbit around the Sun). This paper attempts to calculate the evolution of the Earth-Moon system over the whole of  Earth E s history using sophisticated ocean tide and orbit models. Over long time scales, the rate at which tidal energy is being dissipated is affected by the geometrical configuration of the continents, the length of day, and mean sea level, which is affected by plate tectonic forces and the presence or absence of large ice caps. The faster rotating Earth of the past was less efficient at dissipating energy and the present placement of the continents enhances some tides due to resonances. In addition, tidal dissipation in the Moon slows the orbit evolution by absorbing energy from the orbit and there was a time in the distant past when the  Moon s E tidal dissipation was large. The evolution of the Earth-Moon system is complex and uncertain, but it can be addressed with advanced models.

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Section: Tidal Energy Dissipationmentioning

confidence: 99%

Long‐Term Earth‐Moon Evolution With High‐Level Orbit and Ocean Tide Models

et al. 2021

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“…The similarity in stable isotopes (e.g., for oxygen) between the Earth and Moon would be expected if Theia had a similar provenance to the proto-Earth. However, the stable isotope similarity with Earth is just one of several outstanding issues in lunar origin, including the large mass of the Moon, the similarity in tungsten isotopes, the pattern of moderately volatile element depletion, and the inclination of the lunar orbit (Lock et al 2020;Canup et al 2021). Thus, factors other than material provenance must also be considered when discriminating between giant impact scenarios.…”

Section: Moon Formationmentioning

confidence: 99%

Did Earth Eat Its Leftovers? Impact Ejecta as a Component of the Late Veneer

Carter¹,

Stewart²

2022

Planet. Sci. J.

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The presence of highly siderophile elements in Earth’s mantle indicates that a small percentage of Earth’s mass was delivered after the last giant impact in a stage of “late accretion.” There is ongoing debate about the nature of late-accreted material and the sizes of late-accreted bodies. Earth appears isotopically most similar to enstatite chondrites and achondrites. It has been suggested that late accretion must have been dominated by enstatite-like bodies that originated in the inner disk, rather than ordinary or carbonaceous chondrites. Here we examine the provenances of “leftover” planetesimals present in the inner disk in the late stages of accretion simulations. Dynamically excited planet formation produces planets and embryos with similar provenances, suggesting that the Moon-forming impactor may have had a stable isotope composition very similar to the proto-Earth. Commonly, some planetesimal-sized bodies with similar provenances to the Earth-like planets are left at the end of the main stage of growth. The most chemically similar planetesimals are typically fragments of protoplanets ejected millions of years earlier. If these similar-provenance bodies are later accreted by the planet, they will represent late-accreted mass that naturally matches Earth’s composition. The planetesimal-sized bodies that exist during the giant impact phase can have large core mass fractions, with core provenances similar to the proto-Earth. These bodies are an important potential source for highly siderophile elements. The range of core fractions in leftover planetesimals complicates simple inferences as to the mass and origin of late accretion based on the highly siderophile elements in the mantle.

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“…for oxygen) between the Earth and Moon would be expected if Theia had a similar provenance to the proto-Earth. However, the stable isotope similarity with Earth is just one of several outstanding issues in lunar origin, including the large mass of the Moon, the similarity in Tungsten isotopes, the pattern of moderately volatile element depletion, and the inclination of the lunar orbit (Lock et al 2020;Canup et al 2021). Thus, factors other than material provenance must also be considered when discriminating between giant impact scenarios.…”

Section: Moon Formationmentioning

confidence: 99%

Did Earth eat its leftovers? Impact ejecta as a component of the late veneer

Carter¹,

Stewart²

2022

Preprint

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The presence of highly siderophile elements in Earth's mantle indicates that a small percentage of Earth's mass was delivered after the last giant impact in a stage of 'late accretion.' There is ongoing debate about the nature of late-accreted material and the sizes of late-accreted bodies. Earth appears isotopically most similar to enstatite chondrites and achondrites. It has been suggested that late accretion must have been dominated by enstatite-like bodies that originated in the inner disk, rather than ordinary or carbonaceous chondrites. Here, we examine the provenances of 'leftover' planetesimals present in the inner disk in the late stages of accretion simulations. Dynamically excited planet formation produces planets and embryos with similar provenances, suggesting that the Moon-forming impactor may have had a stable isotope composition very similar to the proto-Earth. Commonly, some planetesimal-sized bodies with similar provenances to the Earth-like planets are left at the end of the main stage of growth. The most chemically-similar planetesimals are typically fragments of proto-planets ejected millions of years earlier. If these similar-provenance bodies are later accreted by the planet, they will represent late-accreted mass that naturally matches Earth's composition. The planetesimal-sized bodies that exist during the giant impact phase can have large core mass fractions, with core provenances similar to the proto-Earth. These bodies are an important potential source for highly siderophile elements. The range of core fractions in leftover planetesimals complicates simple inferences as to the mass and origin of late accretion based on the highly siderophile elements in the mantle.

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Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities

Cited by 25 publications

References 260 publications

Long‐Term Earth‐Moon Evolution With High‐Level Orbit and Ocean Tide Models

Long‐Term Earth‐Moon Evolution With High‐Level Orbit and Ocean Tide Models

Did Earth Eat Its Leftovers? Impact Ejecta as a Component of the Late Veneer

Did Earth eat its leftovers? Impact ejecta as a component of the late veneer

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