Atypical Compounds of Gases, which Have Been Called “Noble”

Grochala, Wojciech

doi:10.1002/chin.200751223

Cited by 29 publications

(47 citation statements)

References 41 publications

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“…Due to the limited storage capacity of the associated surface reservoirs, the shale, clathrate and ice hypotheses can be ruled out. However, whilst Xe is relatively inert under ambient and neutral conditions, the potential for its enhanced reactivity at high-temperature and high-pressure 28 , and possible incorporation in to mineral phases at depth, is commonly used to argue for Xe to be stored in the Earth's interior. Here again, although theoretical and experimental investigations suggest possible Xe incorporation into silicate phases found in the Earth's crust 25 , even the highest measured crustal concentrations of Xe are still three orders of magnitude below that required to account for the missing Xe 29 , therefore excluding the upper continental crust as the main "missing" reservoir.…”

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confidence: 99%

The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

Bekaert

Broadley

Marty

2020

Sci Rep

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The origin of terrestrial volatiles remains one of the most puzzling questions in planetary sciences. The timing and composition of chondritic and cometary deliveries to Earth has remained enigmatic due to the paucity of reliable measurements of cometary material. This work uses recently measured volatile elemental ratios and noble gas isotope data from comet 67P/Churyumov-Gerasimenko (67P/C-G), in combination with chondritic data from the literature, to reconstruct the composition of Earth's ancient atmosphere. Comets are found to have contributed ~20% of atmospheric heavy noble gases (i.e., Kr and Xe) but limited amounts of other volatile elements (water, halogens and likely organic materials) to Earth. These cometary noble gases were likely mixed with chondritic-and not solar-sources to form the atmosphere. We show that an ancient atmosphere composed of chondritic and cometary volatiles is more enriched in Xe relative to the modern atmosphere, requiring that 8-12 times the present-day inventory of Xe was lost to space. This potentially resolves the long-standing mystery of Earth's "missing xenon", with regards to both Xe elemental depletion and isotopic fractionation in the atmosphere. The inferred Kr/H 2 O and Xe/H 2 O of the initial atmosphere suggest that Earth's surface volatiles might not have been fully delivered by the late accretion of volatile-rich carbonaceous chondrites. Instead, "dry" materials akin to enstatite chondrites potentially constituted a significant source of chondritic volatiles now residing on the Earth's surface. We outline the working hypotheses, implications and limitations of this model in the last section of this contribution. Earth's early atmosphere experienced a complex history of impact erosion, mantle outgassing and late additions during periods of heavy asteroid and cometary bombardments 1. The purported Moon forming impact is speculated to have removed a significant fraction of the proto-Earth's atmosphere 2 and resulted in a deep magma ocean estimated to have lasted for several million years 3. Although the presence of a Late Heavy Bombardment (LHB), inferred from the lunar cratering record, has been cast into doubt 4 , the net flux of extraterrestrial materials crossing Earth's orbit was arguably higher during the infancy of the solar system 5. Given its inner solar system origin, the Earth is expected to have grown dry. Volatile-rich bodies (carbonaceous chondrites-hereafter CC-and/ or comets) striking the Earth after core formation have been suggested as the suppliers of volatiles that formed the terrestrial oceans and atmosphere, as well as delivering primitive organic materials 6. The late accretion of chondritic material to Earth after formation of the Moon and core segregation, commonly referred to as the terrestrial "late veneer" (~0.5wt.% of the Earth), is required to account for the high and unfractionated abundances of highly siderophile elements in the terrestrial mantle 7. However, the final stages of Earth's accretion have been argued to be predominantly deri...

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The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

Bekaert

Broadley

Marty

2020

Sci Rep

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“…Evidence for xenon doping of hydrogen in matrix isolation experiments at ambient pressure has been reported 9,10 , but the nature of the bonding in these metastable phases is not well understood. There has been growing interest in the chemistry of xenon to form bulk compounds at high pressures 11 as well as recognition of the biological effects of xenon at high pressures 12 . During the course of investigating the Xe-H 2 system, we have discovered novel compound formation in Xe and H 2 .…”

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Pressure-induced bonding and compound formation in xenon–hydrogen solids

et al. 2009

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Closed electron shell systems, such as hydrogen, nitrogen or group 18 elements, can form weakly bound stoichiometric compounds at high pressures. An understanding of the stability of these van der Waals compounds is lacking, as is information on the nature of their interatomic interactions. We describe the formation of a stable compound in the Xe-H(2) binary system, revealed by a suite of X-ray diffraction and optical spectroscopy measurements. At 4.8 GPa, a unique hydrogen-rich structure forms that can be viewed as a tripled solid hydrogen lattice modulated by layers of xenon, consisting of xenon dimers. Varying the applied pressure tunes the Xe-Xe distances in the solid over a broad range from that of an expanded xenon lattice to the distances observed in metallic xenon at megabar pressures. Infrared and Raman spectra indicate a weakening of the intramolecular covalent bond as well as persistence of semiconducting behaviour in the compound to at least 255 GPa.

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“…Xe retention in crusts and mantles could thus be at stake for both planets. High Xe reactivity has been proved, with the synthesis of several Xe compounds (Grochala, ), among which Xe oxides at ambient conditions (Brock & Schrobilgen, ), at high P ‐ T conditions (Dewaele et al, ), and Xe‐bearing perovskite (Britvin et al, ). Furthermore, Xe can be incorporated as a minor or trace element in SiO 2 phases (Sanloup et al, , ) and in olivine (Crépisson et al, ; Sanloup et al, ) at upper crustal and mantle conditions with up to 0.4 at% Xe possibly stored in olivine.…”

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The Xe‐SiO₂ System at Moderate Pressure and High Temperature

Crépisson

Sanloup

Blanchard

et al. 2019

Geochem Geophys Geosyst

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Xenon (Xe), the heaviest of the stable noble gases, is missing by a factor of 20 relatively to other noble gases, when comparing the Earth's and Mars's atmospheres with chondrites. In this work, the possibility of Xe retention in quartz, a major mineral of the continental crust, is tested. The Xe-SiO 2 system is investigated from 0.7 to 2.7 GPa and up to 1900 K, by in situ X-ray powder diffraction and infrared spectroscopy. Experimental data are complemented by ab initio calculations to retrieve Xe incorporation mechanisms. An excess of quartz unit cell volume up to 4.2% is observed, consistent with a Xe for Si substitution in the quartz structure. Xe has a linear oxygen environment composed of two O atoms located at 1.98-2.00 Å from the Xe atom. Moreover, a new phase is evidenced above Xe melting curve at 0.8-1.0 GPa. The new (Xe,Si)O 2 phase is orthorhombic and corresponds to an elongation of the quartz unit cell. In this phase, Xe substitutes for Si with a nearly planar oxygen environment composed of four O atoms located at 2.06-2.09 Å from the Xe atom. Xe incorporation in SiO 2 proves to be significant, as previously shown for olivine. Xe incorporation is therefore expected to occur in the whole range of lithospheric silicate minerals. These findings emphasize the need to consider Xe incorporation in crust and upper mantle minerals as a process to store and fractionate xenon, in the framework of the "missing xenon" issue.

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Atypical Compounds of Gases, which Have Been Called “Noble”

Abstract: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Cited by 29 publications

References 41 publications

The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

Pressure-induced bonding and compound formation in xenon–hydrogen solids

The Xe‐SiO₂ System at Moderate Pressure and High Temperature

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Atypical Compounds of Gases, which Have Been Called “Noble”

Abstract: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Cited by 29 publications

References 41 publications

The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

The origin and fate of volatile elements on Earth revisited in light of noble gas data obtained from comet 67P/Churyumov-Gerasimenko

Pressure-induced bonding and compound formation in xenon–hydrogen solids

The Xe‐SiO2 System at Moderate Pressure and High Temperature

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Product

Resources

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The Xe‐SiO₂ System at Moderate Pressure and High Temperature