Solar Elemental Abundances

Lodders, K.

doi:10.1093/acrefore/9780190647926.013.145

Cited by 53 publications

(61 citation statements)

References 111 publications

(182 reference statements)

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“…The average NiI/FeI abundance ratio is about unity (log(Ni/Fe) = -0.06 ± 0.31), i.e., an order of magnitude higher than the solar value 17 (−1.25 ± 0.04) or the ratio measured in comet Ikeya-Seki (−1.11±0.09) and it does not depend on the heliocentric distance or the comet origin. In our sample, comet 103P has the lowest value (−0.64±0.07), and the carbon-chain depleted comet 73P the highest value (0.60±0.23), both at heliocentric distances r~1 au (Fig.…”

mentioning

confidence: 73%

Iron and nickel atoms in cometary atmospheres even far from the Sun

Manfroid

Hutsemékers

Jehin

2021

Nature

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In comets, iron and nickel are found in refractory dust particles or in metallic and sulfide grains 1 . No iron-or nickel-bearing molecules have been observed in the gaseous coma of comets 2 . Iron and a few other heavy atoms such as copper and cobalt were only observed in two exceptional objects, the Great Comet of 1882 3 and, almost a century later, C/1965 S1 (Ikeya-Seki) 4-9 . These sungrazing comets approached the Sun so close that the refractory materials could sublimate. The relative abundance of nickel to iron was similar to the Sun and the meteorites 7 . More recently the presence of iron vapor was inferred from the properties of a faint tail in comet C/2006 P1 (McNaught) at perihelion 10 but neither iron nor nickel was reported in the gaseous coma of comet 67P/Churyumov-Gerasimenko by the in situ Rosetta mission 11 . Here we report that neutral FeI and NiI emission lines are ubiquitous in cometary atmospheres, even far from the Sun, as revealed by high-resolution UV-optical spectra of a large sample of comets of various compositions and dynamical origins. The abundances of both species appear to be of the same order of magnitude, contrasting the typical Solar System abundance ratio.

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confidence: 73%

Iron and nickel atoms in cometary atmospheres even far from the Sun

Manfroid

Hutsemékers

Jehin

2021

Nature

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“…The circularity and the aspect ratio are more sensitive to the elongation while the roundness and the solidity are indicators of the sharp edges of the grains. (Lodders and Palme, 2009). EPMA data are obtained as described in (Hewins et al, 2014).…”

Section: Shape Analysismentioning

confidence: 99%

Nebular thermal processing of accretionary fine-grained rims in the Paris CM chondrite

Zanetta

Leroux

Guillou

et al. 2021

Geochimica et Cosmochimica Acta

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Fine-grained rims (FGRs) are ubiquitous in chondrites. They consist of unequilibrated mineral assemblages that surround chondrules and refractory inclusions. As such, they carry information about the material that was accreted onto chondrules. To decipher the nature and the formation mechanism of FGRs and compare them to adjacent matrix material, we investigated their composition, mineralogy, density and texture in the pristine Paris CM chondrite. We coupled a new method (ACADEMY; Zanetta et al., 2019) at the scanning electron microscope (SEM) scale that allows high-resolution quantitative petrology and an analytical transmission electron microscope (TEM) study. Significant differences in modal abundance, grain size and porosity are observed between the FGRs and their adjacent matrix. Domains of amorphous silicates with embedded nanosulfides indicate a high degree of preservation. They are less abundant in the matrix than in the rims. In contrast, secondary alteration phases (phyllosilicates, carbonates and tochilinites) are more abundant in the matrix and associated with larger and fewer sulfide grains. The similar composition of the amorphous silicate in the rims and the matrix attests for a close relationship between the two reservoirs. However, matrix underwent more aqueous alteration. We interpret it as the result of the accretion of material with a higher amount of water in the matrix, leading to a more aqueously altered microenvironment. We also find that coarse-grained anhydrous silicates (olivine and pyroxene) are present in the matrix but not in the FGRs, likely as a result of a chondrule fragmentation episode that occurred after FGR but before matrix accretion. Most of the time, FGRs display distinct inner and outer layers. The inner part is compact and displays larger sulfide grains than the outer part, which is more porous (porosity ~ 45%) and altogether more pristine. These mineral and textural differences are not easily explained by differential aqueous alteration. Instead, a pre-accretion thermal process that preferentially affected the inner rim could have induced loss of porosity, compaction of the amorphous silicate domains as well as sulfides growth. We therefore suggest that FGRs acquired their characteristics in the nebula before matrix accretion to form Paris parent body and discuss possible mechanisms such as dust heating in the chondrule formation environment or secondary heating episode of the previously rimmed chondrule as well as gas friction in high-speed collision conditions.

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“…Compositional models for the terrestrial planets are constructed from the following data sets: composition of the Sun (i.e., > 99% mass of the solar system) (Lodders 2020), chemical trends for samples from a planet, satellite observations, and compositions of chondritic meteorites (i.e., the solar system's building blocks of undifferentiated rock and metal mixtures) (Wasson and Kallemeyn 1988;Alexander 2019a;2019b). Importantly, the chondrites that we have, however, are leftovers from the planetary formation.…”

Section: Composition Of the Terrestrial Planetsmentioning

confidence: 99%

Terrestrial planet compositions controlled by accretion disk magnetic field

McDonough

Yoshizaki

2021

Prog Earth Planet Sci

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Terrestrial planets (Mercury, Venus, Earth, and Mars) are differentiated into three layers: a metallic core, a silicate shell (mantle and crust), and a volatile envelope of gases, ices, and, for the Earth, liquid water. Each layer has different dominant elements (e.g., increasing iron content with depth and increasing oxygen content to the surface). Chondrites, the building blocks of the terrestrial planets, have mass and atomic proportions of oxygen, iron, magnesium, and silicon totaling ≥ 90% and variable Mg/Si (∼ 25%), Fe/Si (factor of ≥2), and Fe/O (factor of ≥ 3). What remains an unknown is to what degree did physical processes during nebular disk accretion versus those during post-nebular disk accretion (e.g., impact erosion) influence these planets final bulk compositions. Here we predict terrestrial planet compositions and show that their core mass fractions and uncompressed densities correlate with their heliocentric distance, and follow a simple model of the magnetic field strength in the protoplanetary disk. Our model assesses the distribution of iron in terms of increasing oxidation state, aerodynamics, and a decreasing magnetic field strength outward from the Sun, leading to decreasing core size of the terrestrial planets with radial distance. This distribution enhances habitability in our solar system and may be equally applicable to exoplanetary systems.

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Solar Elemental Abundances

Cited by 53 publications

References 111 publications

Iron and nickel atoms in cometary atmospheres even far from the Sun

Iron and nickel atoms in cometary atmospheres even far from the Sun

Nebular thermal processing of accretionary fine-grained rims in the Paris CM chondrite

Terrestrial planet compositions controlled by accretion disk magnetic field

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