The composition of the primitive mantle derived here shows that Earth was assembled from material that shows many of the same chemical fractionation processes as chondritic meteorites. These processes occurred at the initial stage of the solar system formation, under conditions thought to be present in the solar nebula. But the stable isotope record excludes chondritic meteorites as the ‘building blocks’ of Earth. Meteorites formed in local environments separated from that part of the inner solar system where much of the material forming the terrestrial planets was sourced.

https://booksite.elsevier.com/brochures/treatiseongeochemistry/contents/sample2.pdf

Cosmochemical Estimates of Mantle Composition

Geochemical evidence continues to challenge giant impact models, which predict that the Moon formed from both proto-Earth and impactor material. Analyses of lunar samples reveal isotopic homogeneity in titanium, a highly refractory element, suggesting lunar material was derived predominantly from the mantle of the proto-Earth.

/pdf/the-proto-earth-as-a-significant-source-of-lunar-material-3xmkzcu1wi.pdf

The proto-Earth as a significant source of lunar material

https://ntrs.nasa.gov/api/citations/20150008274/downloads/20150008274.pdf

Water Delivery and Giant Impacts in the 'Grand Tack' Scenario

A large number of N-body simulations of the giant-impact phase of planet formation, combined with the measured concentrations of highly siderophile elements in Earth’s mantle, reveal that the Moon must have formed at least 40 million years after the condensation of the first solids of the Solar System. The age of the Moon has been a focus for geochemists for at least the past three decades. A number of chronometers have been used to address the question but the results differ from method to method, in part because of the varying assumptions required in the calculation of the so-called model ages. Seth Jacobson et al. have used an alternative approach. They run a large number of numerical simulations, some based on early Moon-forming events, others later events. They then arrive at a model-independent correlation between the formation age of the Moon and the amount of mass accreted by the Earth since then, the so-called Late Veneer. The concentration of highly-siderophile (iron-loving) elements observed in the Earth's mantle provides a constraint on the timing and rules out an early Moon-forming event. Instead, the authors calculate that the Moon-forming impact must have occurred at least 40 million years after formation of the Solar System. According to the generally accepted scenario, the last giant impact on Earth formed the Moon and initiated the final phase of core formation by melting Earth’s mantle. A key goal of geochemistry is to date this event, but different ages have been proposed. Some1,2,3 argue for an early Moon-forming event, approximately 30 million years (Myr) after the condensation of the first solids in the Solar System, whereas others4,5,6 claim a date later than 50 Myr (and possibly as late as around 100 Myr) after condensation. Here we show that a Moon-forming event at 40 Myr after condensation, or earlier, is ruled out at a 99.9 per cent confidence level. We use a large number of N-body simulations to demonstrate a relationship between the time of the last giant impact on an Earth-like planet and the amount of mass subsequently added during the era known as Late Accretion. As the last giant impact is delayed, the late-accreted mass decreases in a predictable fashion. This relationship exists within both the classical scenario7,8 and the Grand Tack scenario9,10 of terrestrial planet formation, and holds across a wide range of disk conditions. The concentration of highly siderophile elements (HSEs) in Earth’s mantle constrains the mass of chondritic material added to Earth during Late Accretion11,12. Using HSE abundance measurements13,14, we determine a Moon-formation age of 95 ± 32 Myr after condensation. The possibility exists that some late projectiles were differentiated and left an incomplete HSE record in Earth’s mantle. Even in this case, various isotopic constraints strongly suggest that the late-accreted mass did not exceed 1 per cent of Earth’s mass, and so the HSE clock still robustly limits the timing of the Moon-forming event to significantly later than 40 Myr after condensation.

Highly siderophile elements in Earth’s mantle as a clock for the Moon-forming impact

Meteorites, which are remnants of solar system formation, provide a direct glimpse into the dynamics and evolution of a young stellar object (YSO), namely our Sun. Much of our knowledge about the astrophysical context of the birth of the Sun, the chronology of planetary growth from micrometer- sized dust to terrestrial planets, and the activity of the young Sun comes from the study of extinct radionuclides such as 26 Al (t1/2 = 0.717 Myr). Here we review how the signatures of extinct radionuclides (short-lived isotopes that were present when the solar system formed and that have now decayed below detection level) in planetary materials influence the current paradigm of solar system formation. Particular attention is given to tying meteorite measurements to remote astronomical observations of YSOs and modeling efforts. Some extinct radionuclides were inherited from the long-term chem- ical evolution of the Galaxy, others were injected into the solar system by a nearby supernova, and some were produced by particle irradiation from the T-Tauri Sun. The chronology inferred from extinct radionuclides reveals that dust agglomeration to form centimeter-sized particles in the inner part of the disk was very rapid (<50 kyr), planetesimal formation started early and spanned several million years, planetary embryos (possibly like Mars) were formed in a few million years, and terrestrial planets (like Earth) completed their growths several tens of million years after the birth of the Sun.

/pdf/a-perspective-from-extinct-radionuclides-on-a-young-stellar-17edlgb11j.pdf

A Perspective from Extinct Radionuclides on a Young Stellar Object: The Sun and Its Accretion Disk

The Earth’s tungsten budget during mantle melting and crust formation

Doublet Pool is an active hydrothermal feature in Yellowstone National Park, USA. Approximately every half hour, it thumps for about 10 min due to bubbles collapsing at the base of the pool. To understand its thermodynamics and sensitivity to external factors, we performed a recurring multiple‐year passive seismic experiment. By linking recorded hydrothermal tremor with active thumping, we determine the onset and end of thumping, and the duration of silence between each thumping cycle. The silence interval decreased from around 30 min before November 2016 to around 13 min in September 2018. This change followed unusual thermal activity on the surrounding Geyser Hill. On a shorter time scale, wind‐driven evaporative cooling can lengthen the pre‐thumping silence interval. Based on energy conservation, we determine the heating rate and heat needed to initiate thumping to be 3–7 MW and ∼6 GJ, respectively.

Thumping Cycle Variations of Doublet Pool in Yellowstone National Park, USA

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The Earth’s tungsten budget during mantle melting and crust formation

Thumping Cycle Variations of Doublet Pool in Yellowstone National Park, USA