On the Distribution and Variation of Radioactive Heat Producing Elements Within Meteorites, the Earth, and Planets

O’Neill, Craig; O’Neill, Hugh St. C.; Jellinek, M.

doi:10.1007/s11214-020-00656-z

Cited by 22 publications

(15 citation statements)

References 109 publications

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“…As illustrated in Fig. 1, depending on their speed of growth before or after disk dissipation and their orbital locations of origin/destination, protoplanets will evolve into objects with different volatile and elemental abundances, which results in different elemental ratios compared to their initial ones due to subsequent atmospheric escape and/or impact erosion of atmospheres and crustal/mantle material (e.g., Lammer et al, 2020a;this issue;O'Neill et al, 2020; this issue). Safronov (1969) proposed the first physical model for the formation of the terrestrial planets.…”

Section: Introductionmentioning

confidence: 99%

Formation of Venus, Earth and Mars: Constrained by Isotopes

et al. 2020

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Here we discuss the current state of knowledge of terrestrial planet formation from the aspects of different planet formation models and isotopic data from 182 Hf-182 W, U-Pb, lithophile-siderophile elements, 48 Ca/ 44 Ca isotope samples from planetary building blocks, recent reproduction attempts from 36 Ar/ 38 Ar, 20 Ne/ 22 Ne, 36 Ar/ 22 Ne isotope ratios in Venus' and Earth's atmospheres, the expected solar 3 He abundance in Earth's deep mantle and Earth's D/H sea water ratios that shed light on the accretion time of the early protoplanets. Accretion scenarios that can explain the different isotope ratios, including a Moon-forming event ca. 50 Myr after the formation of the Solar System, support the theory that the bulk of Earth's mass (≥ 80 %) most likely accreted within 10-30 Myr. From a combined analysis of the before mentioned isotopes, one finds that proto-Earth accreted a mass of 0.5-0.6 MEarth within the first ≈ 4-5 Myr, the approximate lifetime of the protoplanetary disk. For Venus, the available atmospheric noble gas data are too uncertain for constraining the planet's accretion scenario accurately. However, from the available imprecise Ar and Ne isotope measurements, one finds that proto-Venus could have grown to a mass of 0.85-1.0 MVenus before the disk dissipated. Classical terrestrial planet formation models have struggled to grow large planetary embryos, or even cores of giant planets, quickly from the tiniest materials within the typical lifetime of protoplanetary disks. Pebble accretion could solve this long-standing time scale controversy. Pebble accretion and streaming instabilities produce large planetesimals that grow into Marssized and larger planetary embryos during this early accretion phase. The later stage of accretion can be explained well with the Grand-Tack model as well as the annulus and depleted disk models. The relative roles of pebble accretion and planetesimal accretion/giant impacts are poorly understood and should be investigated with N-body simulations that include pebbles and multiple protoplanets. To summarise, different isotopic dating methods and the latest terrestrial planet formation models indicate that the accretion process from dust settling, planetesimal formation, and growth to large planetary embryos and protoplanets is a fast process that occurred to a great extent in the Solar System within the lifetime of the protoplanetary disk.

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Section: Introductionmentioning

confidence: 99%

Formation of Venus, Earth and Mars: Constrained by Isotopes

et al. 2020

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“…If the ratio of internal to basal heating increased in the past, then that would imply that boundary layer interaction has increased over the Earth's history and that the cooling rate of the Earth may not be adequately captured by scaling laws based on end‐member cases. Models of the Earth's bulk composition can be used to constrain the percentage of radioactive elements within the mantle which can provide estimates of internal heat generation in the past (O'Neill et al., 2020). Minimum basal heat flux constraints come from the need to maintain a geodynamo in the Earth's past (Nimmo, 2015).…”

Section: Discussionmentioning

confidence: 99%

Convective and Tectonic Plate Velocities in a Mixed Heating Mantle

Lenardic

Seales

Moore

et al. 2021

Geochem Geophys Geosyst

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Mantle convection and, by association, plate tectonics is driven by the transport of heat from a planetary interior. This heat comes from the internal energy of the mantle and from heat flowing into the base of the mantle from the core. Past investigations of such mixed mode heating have revealed unusual behavior that confounds our intuition based on end‐member cases. In particular, increased internal heating leads to a decrease in convective velocity. We investigate this behavior using a suite of numerical experiments and develop a scaling for velocity in the mixed heating case. We identify a planform transition, as internal heating increases, from sheet‐like to plume‐like downwellings that impacts heat flux and convective velocities. More significantly, we demonstrate that increased internal heating leads not only to a decrease in internal velocities but also a decrease in the velocity of the upper thermal boundary layer (a model analog of the Earth's lithosphere). This behavior is connected to boundary layer interactions and is independent of any particular rheological assumptions. In cases with a temperature‐dependent viscosity and weak plate margin analogs, increased internal heating does not cause an absolute decrease in surface velocity but does cause a decrease relative to purely bottom or internally heated cases as well as a transition to rigid‐lid behavior at high heating rates. The differences between a mixed system and end‐member cases have implications for understanding the connection between plate tectonics and mantle convection and for planetary thermal history modeling.

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“…An additional problem with this size-related ηE definition is the lack of knowledge of the potential accretion histories of these ηE-like planets, their internal composition, tectonic regime, and more (see Bermingham et al 2020;Lammer et al 2020b). Each of the mentioned studies have chosen particular limits within possible ranges, but neglected potential relevant parameters such as the distribution and variation of radioactive heat producing elements (see O'Neill et al 2020) within planetary building blocks and consequently within Earth-sized exoplanets. Moreover, the billion years lasting evolution of planetary atmospheres (see Avice and Marty 2020;Lammer et al 2020a), including their shaping factors related to their host stars activity evolution (see Güdel 2020), are also neglected in such estimates.…”

Section: η-Earth and The Relevance Of N 2 -O 2 Dominated Atmosphere Detection By Future Space Missionsmentioning

confidence: 99%

“…Finally, if N 2 -dominated atmospheres are rare, due to the complex interplay of atmosphere, lithosphere, and biosphere (see O'Neill et al 2020;Stüeken et al 2020;Lloyd et al 2020), then one may expect that the atmospheres of most Earth-sized exoplanets in the habitable zones would be CO 2 -dominated . Carbon dioxide molecules present a number of absorption bands in the IR, making them detectable from space with the future James Webb Space Telescope (JWST) and ARIEL space observatories, and from the ground with high-resolution spectrographs attached to the ELTs.…”

Section: η-Earth and The Relevance Of N 2 -O 2 Dominated Atmosphere Detection By Future Space Missionsmentioning

confidence: 99%

“…In the course of its evolution, each planetary atmosphere is fed by additional material from its space environment and from the planet's degassing interior (Stüeken et al 2020) while a fraction of its atmospheric chemical elements escape to outer space (Lammer et al 2020a). A quantitative assessment of the effects of these mechanisms can be partly constrained in the chemical and isotopic composition of the different planetary layers, among them its atmosphere, and in the meteorite record (e.g., O'Neill et al 2020) where they can be most easily measured. These measurements provide constraints on the formation history of Earth, Moon and the terrestrial planets (Lammer et al 2020b), on the evolution of planetary atmospheres (Avice and Marty 2020;Stüeken et al 2020) and on their current composition .…”

Section: Introductionmentioning

confidence: 99%

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Future Missions Related to the Determination of the Elemental and Isotopic Composition of Earth, Moon and the Terrestrial Planets

et al. 2020

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In this chapter, we review the contribution of space missions to the determination of the elemental and isotopic composition of Earth, Moon and the terrestrial planets, with special emphasis on currently planned and future missions. We show how these missions are going to significantly contribute to, or sometimes revolutionise, our understanding of planetary evolution, from formation to the possible emergence of life. We start with the Earth, which is a unique habitable body with actual life, and that is strongly related to its atmosphere. The new wave of missions to the Moon is then reviewed, which are going to study its formation history, the structure and dynamics of its tenuous exosphere and the interaction of the Moon’s surface and exosphere with the different sources of plasma and radiation of its environment, including the solar wind and the escaping Earth’s upper atmosphere. Missions to study the noble gas atmospheres of the terrestrial planets, Venus and Mars, are then examined. These missions are expected to trace the evolutionary paths of these two noble gas atmospheres, with a special emphasis on understanding the effect of atmospheric escape on the fate of water. Future missions to these planets will be key to help us establishing a comparative view of the evolution of climates and habitability at Earth, Venus and Mars, one of the most important and challenging open questions of planetary science. Finally, as the detection and characterisation of exoplanets is currently revolutionising the scope of planetary science, we review the missions aiming to characterise the internal structure and the atmospheres of these exoplanets.

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On the Distribution and Variation of Radioactive Heat Producing Elements Within Meteorites, the Earth, and Planets

Cited by 22 publications

References 109 publications

Formation of Venus, Earth and Mars: Constrained by Isotopes

Formation of Venus, Earth and Mars: Constrained by Isotopes

Convective and Tectonic Plate Velocities in a Mixed Heating Mantle

Future Missions Related to the Determination of the Elemental and Isotopic Composition of Earth, Moon and the Terrestrial Planets

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