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All chondrites are shown to have Ru isotopic compositions that are more different from that of the Earth’s mantle the further from the Sun they formed; this means the Earth’s late veneer cannot derive from volatile-rich material formed in the outer Solar System. The origin of the Earth's late veneer Mario Fischer-Gödde and Thorsten Kleine show that all chondrites, including carbonaceous chondrites, have ruthenium isotopic compositions that are distinct from that of the Earth's mantle. The ruthenium isotope anomalies increase in the order of enstatite to ordinary to carbonaceous chondrites, demonstrating that material formed at greater heliocentric distance has larger ruthenium isotope anomalies. The authors conclude that the 'late veneer' of material accreted to the Earth following the Moon-forming impact must not have originated in the outer Solar System, and that the late veneer was not the primary source of volatiles and water on the Earth. The excess of highly siderophile elements in the Earth’s mantle is thought to reflect the addition of primitive meteoritic material after core formation ceased 1 , 2 , 3 , 4 . This ‘late veneer’ either comprises material remaining in the terrestrial planet region after the main stages of the Earth’s accretion 5 , 6 , or derives from more distant asteroidal 7 or cometary 8 sources. Distinguishing between these disparate origins is important because a late veneer consisting of carbonaceous chondrite-like asteroids 7 or comets 8 could be the principal source of the Earth’s volatiles and water. Until now, however, a ‘genetic’ link between the late veneer and such volatile-rich materials has not been established or ruled out. Such genetic links can be determined using ruthenium (Ru) isotopes, because the Ru in the Earth’s mantle predominantly derives from the late veneer 9 , and because meteorites exhibit Ru isotope variations arising from the heterogeneous distribution of stellar-derived dust 10 , 11 . Although Ru isotopic data and the correlation of Ru and molybdenum (Mo) isotope anomalies in meteorites were previously used to argue that the late veneer derives from the same type of inner Solar System material as do Earth’s main building blocks 6 , the Ru isotopic composition of carbonaceous chondrites has not been determined sufficiently well to rule them out as a source of the late veneer. Here we show that all chondrites, including carbonaceous chondrites, have Ru isotopic compositions distinct from that of the Earth’s mantle. The Ru isotope anomalies increase from enstatite to ordinary to carbonaceous chondrites, demonstrating that material formed at greater heliocentric distance contains larger Ru isotope anomalies. Therefore, these data refute an outer Solar System origin for the late veneer and imply that the late veneer was not the primary source of volatiles and water on the Earth.

Precise measurements of the tungsten isotopic composition of lunar rocks show that the Moon exhibits a well-resolved excess of 182 W of about 27 parts per million over the present-day Earth’s mantle: this excess is consistent with the expected 182 W difference resulting from a late veneer with a total mass and composition inferred from previously measured highly siderophile elements. Late accretion to Earth and Moon Two papers published in this issue of Nature present precise measurements of tungsten isotope composition in lunar rocks that are best explained by the Earth and Moon having had similar composition immediately following formation of the Moon, and then having diverged as a result of disproportional late accretion of material to the two bodies. Mathieu Touboul et al . found small 182 W excess of about 21 parts per million relative to the present-day Earth's mantle in metals extracted from two KREEP-rich Apollo 16 impact-melt rocks, while Thomas Kruijer et al . measured tungsten isotopes in seven KREEP-rich whole rock samples that span a wide range of cosmic ray exposure ages, and found a 182 W excess of about 27 parts per million over the present-day Earth's mantle. 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 1 . 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 2 . One explanation for this overabundance is that a ‘late veneer’ of primitive material was added to the bulk silicate Earth after the core formed 2 . 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 3 . 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 2 . 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.

The accretion of volatile-rich material from the outer Solar System represents a crucial prerequisite for Earth to develop oceans and become a habitable planet 1 – 4 . However, the timing of this accretion remains controversial 5 – 8 . It has been proposed that volatile elements were added to Earth by the late accretion of a late veneer consisting of carbonaceous-chondrite-like material after core formation had ceased 6 , 9 , 10 . This view could not be reconciled with the ruthenium (Ru) isotope composition of carbonaceous chondrites 5 , 11 , which is distinct from that of the modern mantle 12 , or of any known meteorite group 5 . As a possible solution, Earth’s pre-late-veneer mantle could already have contained a fraction of Ru that was not fully extracted by core formation 13 . The presence of such pre-late-veneer Ru can only be established if its isotope composition is distinct from that of the modern mantle. Here we report the first high-precision, mass-independent Ru isotope compositions for Eoarchaean ultramafic rocks from southwest Greenland, which display a relative 100 Ru excess of 22 parts per million compared with the modern mantle value. This 100 Ru excess indicates that the source of the Eoarchaean rocks already contained a substantial fraction of Ru before the accretion of the late veneer. By 3.7 billion years ago, the mantle beneath southwest Greenland had not yet fully equilibrated with late accreted material. Otherwise, no Ru isotopic difference relative to the modern mantle would be observed. If constraints from other highly siderophile elements besides Ru are also considered 14 , the composition of the modern mantle can only be reconciled if the late veneer contained substantial amounts of carbonaceous-chondrite-like materials with their characteristic 100 Ru deficits. These data therefore relax previous constraints on the late veneer and are consistent with volatile-rich material from the outer Solar System being delivered to Earth during late accretion. Ruthenium isotope compositions of the oldest preserved mantle rocks from Greenland imply that volatile-rich outer Solar System material was not delivered to Earth until very late in the planet’s formation.

Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s-process component. We report isotopic relations of ϵ 92Mo versus ϵ 100Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s-process abundance variations. We show that two p-process isotopes 92Mo and 94Mo require the presence of distinct p-process components in meteoritic materials. The nucleosynthetic origin of abundant magic (N = 50) p-process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp-antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p-process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p-nuclides.

The processes of planet formation in our Solar System resulted in a final product of a small number of discreet planets and planetesimals characterized by clear compositional distinctions. A key advance on this subject was provided when nucleosynthetic isotopic variability was discovered between different meteorite groups and the terrestrial planets. This information has now been coupled with theoretical models of planetesimal growth and giant planet migration to better understand the nature of the materials accumulated into the terrestrial planets. First order conclusions include that carbonaceous chondrites appear to contribute a much smaller mass fraction to the terrestrial planets than previously suspected, that gas-driven giant planet migration could have pushed volatile-rich material into the inner Solar System, and that planetesimal formation was occurring on a sufficiently rapid time scale that global melting of asteroid-sized objects was instigated by radioactive decay of 26 Al. The isotopic evidence highlights the important role of enstatite chondrites, or something with their mix of nucleosynthetic components, as feedstock for the terrestrial planets. A common degree of depletion of moderately volatile elements in the terrestrial planets points to a mechanism that can effectively separate volatile and refractory elements over a spatial scale the size of the whole inner Solar System. The large variability in iron to silicon ratios between both different meteorite groups and between the terrestrial planets suggests that mechanisms that can segregate iron metal from silicate should be given greater importance in future investigations. Such processes likely include both density separation of small grains in the nebula, but also preferential impact erosion of either the mantle or core from differentiated planets/planetesimals. The latter highlights the important role for giant impacts and collisional erosion during the late stages of planet formation.

With plate tectonics operating on Earth, the preservation potential for mantle reservoirs from the Hadean Eon (>4.0 Ga) has been regarded as very small. The quest for such early remnants has been spurred by the observation that many Archean rocks exhibit excesses of 182W, the decay product of short-lived 182Hf. However, it remains speculative whether Archean 182W anomalies and also 182W deficits found in many young ocean island basalts (OIBs) mirror primordial Hadean mantle differentiation or merely variable contributions from older meteorite building blocks delivered to the growing Earth. Here, we present a high-precision 182W isotope dataset for 3.22- to 3.55-Ga-old rocks from the Kaapvaal Craton, southern Africa. In expanding previous work, our study reveals widespread 182W deficits in different rock units from the Kaapvaal Craton and also the discovery of a negative covariation between short-lived 182W and long-lived 176Hf–143Nd–138Ce patterns, a trend of global significance. Among different models, these distinct patterns can be best explained by the presence of recycled mafic restites from Hadean protocrust in the ancient mantle beneath the Kaapvaal Craton. Further, the data provide unambiguous evidence for the operation of silicate differentiation processes on Earth during the lifetime of 182Hf, that is, the first 60 million y after solar system formation. The striking isotopic similarity between recycled protocrust and the low-182W endmember of modern OIBs might also constitute the missing link bridging 182W isotope systematics in Archean and young mantle-derived rocks.

In the context of bank-financed takeovers, I examine the influence of loans and their characteristics on the success of acquisitions. The unique setting of matched syndicated loans allows me to forego the regular assumption in academic literature of cash payment being equal to debt financing. Consequently, I am able to distinguish between the payment effect and the financing effect of an acquisition. My three main findings are: (i) Payment method is just an estimator of the debt proportion in takeovers. Although percentage of cash has significant explanatory power to account for the sources of financing, variation still remains. (ii) Controlling for the real financial structure renders the payment method insignificant. Hence, the well-known outperformance of cash payment around the announcement of a takeover might actually just be an outperformance of debt-financed takeovers. (iii) Bank-financed acquisitions are associated, on average, with positive abnormal returns for acquirers’ stockholders. Higher bank involvements—approximated by greater deal leverage, higher loan costs, longer maturity, lower interest coverage, or no previous banking relationship—are signals for a more successful takeover.

PurposeLong-term follow-up after sleeve gastrectomy (SG) revealed a high incidence of gastroesophageal reflux disease (GERD) frequently caused by preoperative silent pathologic reflux. We aimed to evaluate prevalence and phenotypes of GERD in asymptomatic patients with morbid obesity prior to metabolic surgery according to modern objective testing.Material and MethodsProspective collection of data including consecutive patients with morbid obesity (body mass index (BMI) ≥ 35 kg/m2) prior to metabolic surgery was applied for this study between 2014 and 2019. Patients underwent clinical examinations, endoscopy, pH metry, and high-resolution manometry and were analyzed according to the Lyon consensus.ResultsOf 1379 patients undergoing metabolic surgery, 177 (12.8%, females = 105) asymptomatic individuals with a median age of 42.6 (33.8; 51.6) years and a median BMI of 44.6 (41.3; 50.8) kg/m2 completed objective testing and were included during the study period. GERD was diagnosed in 55 (31.1%), whereas criteria of borderline GERD were met in another 78 (44.1%). GERD was mediated by a structural defective lower esophageal sphincter (p = 0.004) and highlighted by acidic (p = 0.004) and non-acidic (p = 0.022) reflux episodes. Esophageal motility disorders were diagnosed in 35.6% (n = 63) of individuals with a novel hypercontractile disorder found in 7.9% (n = 14) of patients.ConclusionGERD affects a majority of asymptomatic patients with morbid obesity prior to primary bariatric surgery. Future longitudinal trials will have to reveal the clinical significance of esophageal motility disorders in patients with morbid obesity.

We use market-wide implied cost of capital to investigate changes in mutual funds’ risk exposures. Our approach is solely based on market information at the respective time and seems natural, as analysts and fund managers possess similar knowledge and skills. Using a sample of 4147 US equity mutual funds, we provide evidence for time-varying risk exposures for all funds, independent of their style and size focus. Furthermore, value (growth) funds reduce their value (momentum) loadings in times of a high expected market risk premium. However, only for small- and mid-cap funds, this beneficial behavior can be attributed to active management. After controlling for time-varying risk factors, all fund types perform equally poorly measured by their alpha.