scholarly journals Chemical Differentiation of Planets: A Core Issue

2022 ◽  
Vol 924 (2) ◽  
pp. 83
Author(s):  
Hervé Toulhoat ◽  
Viacheslav Zgonnik
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
Statistical Physics ◽  
Surface Segregation ◽  
Compositional Data ◽  
Planetary Body ◽  
Element Abundances ◽  
The Earth ◽  
Distribution Of Elements ◽  
Core Issue

Abstract By plotting empirical chemical element abundances on Earth relative to the Sun and normalized to silicon versus their first ionization potentials, we confirm the existence of a correlation reported earlier. To explain this, we develop a model based on principles of statistical physics that predicts differentiated relative abundances for any planetary body in a solar system as a function of its orbital distance. This simple model is successfully tested against available chemical composition data from CI chondrites and surface compositional data of Mars, Earth, the Moon, Venus, and Mercury. We show, moreover, that deviations from the proposed law for a given planet correspond to later surface segregation of elements driven both by gravity and chemical reactions. We thus provide a new picture for the distribution of elements in the solar system and inside planets, with important consequences for their chemical composition. Particularly, a 4 wt% initial hydrogen content is predicted for bulk early Earth. This converges with other works suggesting that the interior of the Earth could be enriched with hydrogen.

The Origin of the Moon

1962 ◽  
Vol 14 ◽  
pp. 149-155 ◽  
Author(s):  
E. L. Ruskol
Keyword(s):  
Chemical Composition ◽  
Solar System ◽  
The Moon ◽  
The Earth ◽  
The Difference ◽  
Origin Of The Moon

The difference between average densities of the Moon and Earth was interpreted in the preceding report by Professor H. Urey as indicating a difference in their chemical composition. Therefore, Urey assumes the Moon's formation to have taken place far away from the Earth, under conditions differing substantially from the conditions of Earth's formation. In such a case, the Earth should have captured the Moon. As is admitted by Professor Urey himself, such a capture is a very improbable event. In addition, an assumption that the “lunar” dimensions were representative of protoplanetary bodies in the entire solar system encounters great difficulties.

scholarly journals Features of the geochemistry of the Moon and the Earth, determined by the mechanism of formation of the Earth – Moon system (report at the 81st international meteorite conference, Moscow, july 2018)

2019 ◽  
Vol 64 (8) ◽  
pp. 762-776
Author(s):  
E. M. Galimov
Keyword(s):  
Solar System ◽  
Volatile Components ◽  
Kinetic Regime ◽  
The Moon ◽  
Mechanism Of Formation ◽  
Planetary Body ◽  
Moon System ◽  
The Earth ◽  
Reversible Nature ◽  
Dust Condensation

This article discusses some features of geochemistry of the Earth and the Moon, which manifests the specificity of the mechanism of their formation by fragmentation of protoplanetary gas-dust condensation (Galimov & Krivtsov, 2012). The principal difference between this model and other hypotheses of the Earth-Moon system formation, including the megaimpact hypothesis, is that it assumes the existence of a long stage of the dispersed state of matter, starting with the formation of protoplanetary gas-dust condensation, its compression and fragmentation and ending with the final accretion to the formed high-temperature embryos of the Earth and the Moon. The presence of the dispersed state allows a certain way to interpret the observed properties of the Earth-Moon system. Partial evaporation of solid particles due to adiabatic heating of the compressing condensation leads to the loss of volatiles including FeO. Computer simulations show that the final accretion is mainly performed on a larger fragment (the Earth’s embryo) and only slightly increases the mass of the smaller fragment (the Moon embryo).This explains the relative depletion of the Moon in iron and volatile and the increased concentration of refractory components compared to the Earth. The reversible nature of evaporation into the dispersed space, in contrast to the kinetic regime, and the removal of volatiles in the hydrodynamic flow beyond the gas-dust condensation determines the loss of volatiles without the effect of isotopes fractionation. The reversible nature of volatile evaporation also provides, in contrast to the kinetic regime, the preservation of part of the high-volatile components, such as water, in the planetary body, including the Moon. It follows from the essence of the model that at least a significant part of the Earth’s core is formed not by segregation of iron in the silicate-metal melt, but by evaporation and reduction of FeO in a dispersed medium, followed by deposition of clusters of elemental iron to the center of mass. This mechanism of formation of the core explains the observed excess of siderophilic elements in the Earth’s mantle. It also provides a plausible explanation for the observed character of iron isotopes fractionation (in terms of δ57Fe‰) on Earth and on the Moon. It solves the problem of the formation of iron core from initially oxide (FeO) form. The dispersed state of the substance during the period of accretion suggests that the loss of volatiles occurred during the time of accretion. Using the fact that isotopic systems: U–Pb, Rb–Sr, 129J–129Xe, 244Pu–136Xe, contain volatile components, it is possible to estimate the chronology of events in the evolution of the protoplanetary state. As a result, agreed estimates of the time of fragmentation of the primary protoplanetary condensation and formation of the embryos of the Earth and the Moon are obtained: from 10 to 40 million years, and the time of completion of the earth’s accretion and its birth as a planetary body: 110 – 130 million years after the emergence of the solar system. The presented interpretation is consistent with the fact that solid minerals on the Moon have already appeared at least 60 million years after the birth of the solar system (Barboni et al., 2017), and the metal core in the Earth and in the Moon could not have formed before 50 million years from the start of the solar system, as follows from the analysis of the Hf-W system (Kleine et al., 2009). It is shown that the hypothesis of megaimpact does not satisfy many constraints and does not create a basis for the explanation of the geochemistry of the Earth and the Moon.

Earth's thermospheric evolution and implications for planetary habitability

2020 ◽  
Author(s):  
Colin Johnstone
Keyword(s):  
Carbon Dioxide ◽  
Solar Wind ◽  
Chemical Composition ◽  
Solar System ◽  
Planetary Atmospheres ◽  
Upper Atmosphere ◽  
The Sun ◽  
The Earth ◽  
First Time ◽  
Planetary Habitability

<p>During the Archean eon from 3.8 to 2.5 billion years ago, the Earth's upper atmosphere and interactions with the magnetosphere and the solar wind were likely significantly different to how it is today due to major differences in the chemical composition of the atmosphere and the younger Sun being signifcantly more active. Understanding these factors is important for understanding the evolution of planetary atmospheres within our solar system and beyond. While the higher activity of the Sun would have caused additional heating and expansion of the atmosphere, geochemical measurements show that carbon dioxide was far more abundant during this time and this would have led to significantly thermospheric cooling which would have protected the atmosphere from losses to space. I will present a study of the effects of the carbon dioxide composition and the Sun's activity evolution on the thermosphere and ionosphere of the Archean Earth, studying for the first time the effects of different scenarios for the Sun's activity evolution. I will show the importance of these factors for the exosphere and escape processes of the Earth and terrestrial planets outside our solar system.</p>

From the depths of the Earth

2010 ◽  
Author(s):  
Jan Zalasiewicz
Keyword(s):  
Solar System ◽  
Centrifugal Force ◽  
Outer Layer ◽  
The Moon ◽  
Planetary Body ◽  
The Earth ◽  
The One ◽  
Separate Identity ◽  
Two Bodies

The planet Theia had, like the Earth, formed early, from the mass of dust and rock-melt droplets of the accretionary disc. Theia is calculated to have been about the size of Mars, yet it was to have nothing like that planet’s longevity. Its orbit was close enough to that of Earth for collision to be certain, sooner or later. The two planets came together at something of the order of 40,000 kilometres per hour. Theia lost its separate identity over a few tumultuous minutes, and the Earth was smashed, like a grapefruit hit hard with a hammer. In that conflagration the material of the two planets, having instantly converted into boiling magma and vapour, simply merged. Theia’s core sank to join the Earth’s. Some of the outer layer of both planets splashed out into a cloud of plasma that encircled the suddenly re-formed Earth, and that cloud condensed to form a new companion to our planet—the Moon. It is a fine story, this, of the Moon’s creation through a spectacular planetary collision. It is likely true, too: though it is not certainly so, simply being the hypothesis that now best explains the character of our Earth and its satellite. Like many such stories in science, it is currently the one that best fits the evidence. It has been calculated, on the basis of these two bodies’ mass, momentum and orbit, that it would have been extraordinarily difficult for the Earth to have captured intact a stray planetary body of this size. However, holding onto a mass of ejecta flung out by impact, kept in balance by the twin, opposing forces of gravity and centrifugal force, is a more plausible means of having formed the Moon. More, this concept explains the remarkable isotopic similarity of these two bodies, generated by the intense mixing associated with impact. Mars, by contrast, has very different proportions of, say, the different isotopes of oxygen, because it formed in a different part of the Solar System, where the atoms of the original accretionary disk had been shuffled into different combinations.

The Origin of the Moon and its Relationship to the Origin of the Solar System

1962 ◽  
Vol 14 ◽  
pp. 133-148 ◽  
Author(s):  
Harold C. Urey
Keyword(s):  
Solar System ◽  
The Moon ◽  
The Past ◽  
The Earth ◽  
Short Period ◽  
Origin Of The Moon

During the last 10 years, the writer has presented evidence indicating that the Moon was captured by the Earth and that the large collisions with its surface occurred within a surprisingly short period of time. These observations have been a continuous preoccupation during the past years and some explanation that seemed physically possible and reasonably probable has been sought.

scholarly journals Isotopic evidence for the formation of the Moon in a canonical giant impact

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sune G. Nielsen ◽  
David V. Bekaert ◽  
Maureen Auro
Keyword(s):  
Solar System ◽  
Isotope Fractionation ◽  
Main Stage ◽  
The Moon ◽  
Giant Impact ◽  
Bulk Silicate Earth ◽  
The Earth ◽  
The Standard Model ◽  
Isotopic Measurements ◽  
Origin Of The Moon

AbstractIsotopic measurements of lunar and terrestrial rocks have revealed that, unlike any other body in the solar system, the Moon is indistinguishable from the Earth for nearly every isotopic system. This observation, however, contradicts predictions by the standard model for the origin of the Moon, the canonical giant impact. Here we show that the vanadium isotopic composition of the Moon is offset from that of the bulk silicate Earth by 0.18 ± 0.04 parts per thousand towards the chondritic value. This offset most likely results from isotope fractionation on proto-Earth during the main stage of terrestrial core formation (pre-giant impact), followed by a canonical giant impact where ~80% of the Moon originates from the impactor of chondritic composition. Our data refute the possibility of post-giant impact equilibration between the Earth and Moon, and implies that the impactor and proto-Earth mainly accreted from a common isotopic reservoir in the inner solar system.

scholarly journals 10. General Discussion

1960 ◽  
Vol 10 ◽  
pp. 677-679 ◽  
Keyword(s):  
Yield Curve ◽  
Fission Products ◽  
Heavy Elements ◽  
Sikhote Alin ◽  
Heavy Nuclei ◽  
Fission Yield ◽  
Element Abundances ◽  
The Earth ◽  
R Process ◽  
Nova Outburst

1. p. SELINOV: Anomalous abundances of Te and Xe isotopes in meteorites and in the Earth permit us to draw some conclusions concerning the age of uranium and the processes of nucleogenesis. According to the estimate by Hoyle the amount of 254Cf disintegrated during a super-nova outburst is of the order of io29 g or io~4 of the stellar mass. According to the fission-yield curve the isotopes of Te comprise about 1 % of the mass of fission products. The abundances of Te 128-131 are anomalously high, due to the fission of heavy nuclei. The element abundances do not permit us to draw any conclusions about the r-process. The isotopes of Te and Xe with even mass numbers give evidence in favour of the r-process (anomalously high abundances). But the amount of Te in meteorites and in Earth is about 1000 times less than it should be if formed during the outburst. The Sikhote- Alin meteorite shows the same anomaly. We may conclude that the heavy elements of the solar system have been formed not in a single super-nova outburst, but as a result of mixing from the totality of outbursts. According to Hoyle, this gives a definite estimate for the age of uranium.

scholarly journals Physical Parameters and Chemical Composition of Components of the Am-Type Binary System RR Lyncis

1993 ◽  
Vol 138 ◽  
pp. 192-196
Author(s):  
L.S. Lyubimkov ◽  
T.M. Rachkovskaya
Keyword(s):  
Chemical Composition ◽  
Binary System ◽  
Binary Stars ◽  
Spectroscopic Binaries ◽  
Theoretical Modelling ◽  
Physical Parameters ◽  
Accurate Data ◽  
Element Abundances ◽  
Widespread Phenomenon ◽  
Chemical Anomalies

Duplicity is a very widespread phenomenon among Am-stars. For instance, Abt (1961) investigating 25 such stars found out that 22 of them are spectroscopic binaries. However this important phenomenon is ignored usually in chemical composition investigations of Am-stars. Consequently some “mean” element abundances are determined, which can noticeably differ from real abundances in atmospheres of components. Moreover false chemical anomalies can appear, as shown by the theoretical modelling of spectra of binary stars (Lyubimkov, 1989, 1992). Meanwhile accurate data on chemical composition of Am-stars must be considered as observational test for any hypothesis suggested for explanation of these objects.

scholarly journals A unique basaltic micrometeorite expands the inventory of solar system planetary crusts

2009 ◽  
Vol 106 (17) ◽  
pp. 6904-6909 ◽  
Author(s):  
Matthieu Gounelle ◽  
Marc Chaussidon ◽  
Alessandro Morbidelli ◽  
Jean-Alix Barrat ◽  
Cécile Engrand ◽  
...  
Keyword(s):  
Solar System ◽  
Mineral Chemistry ◽  
Carbonaceous Chondrites ◽  
Isotopic Data ◽  
Solar System Formation ◽  
Sample Return ◽  
Dust Transport ◽  
Element Abundances ◽  
Transport Dynamics ◽  
Sample Return Mission

Micrometeorites with diameter ≈100–200 μm dominate the flux of extraterrestrial matter on Earth. The vast majority of micrometeorites are chemically, mineralogically, and isotopically related to carbonaceous chondrites, which amount to only 2.5% of meteorite falls. Here, we report the discovery of the first basaltic micrometeorite (MM40). This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts and underlines the importance of micrometeorites for sampling the asteroids' surfaces in a way complementary to meteorites, mainly because they do not suffer dynamical biases as meteorites do. The parent asteroid of MM40 has undergone extensive metamorphism, which ended no earlier than 7.9 Myr after solar system formation. Numerical simulations of dust transport dynamics suggest that MM40 might originate from one of the recently discovered basaltic asteroids that are not members of the Vesta family. The ability to retrieve such a wealth of information from this tiny (a few micrograms) sample is auspicious some years before the launch of a Mars sample return mission.

Planet Earth – our oasis in space

2004 ◽  
Vol 12 (1) ◽  
pp. 111-119
Author(s):  
SIEGFRIED J. BAUER
Keyword(s):  
Magnetic Field ◽  
Solar System ◽  
Internal Structure ◽  
Solid Surface ◽  
Liquid Water ◽  
Atmospheric Environment ◽  
Suitable Habitat ◽  
The Earth

Planet Earth is unique in our solar system as an abode of life. In contrast to its planetary neighbours, the presence of liquid water, a benign atmospheric environment, a solid surface and an internal structure providing a protective magnetic field make it a suitable habitat for man. While natural forces have shaped the Earth over millennia, man through his technological prowess may become a threat to this oasis of life in the solar system.

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