📰 An ancient history of the Earth in the light of the missing xenon paradox


Credit: Chrystèle Sanloup, IMPM

By experimentally showing for the first time that xenon entrapment in high-pressure, high-temperature silicate minerals leads to its isotope fractionation, the scientists solved the “paradox (A paradox is a proposition that contains or appears to contain a logical contradiction, or a …) from xenon (Xenon is a chemical element, symbol Xe and atomic number 54. The …) dispersed “and proposed a scenario related to the ancient history of Land (Earth is the third planet in the Solar System in order of distance …).

The missing xenon paradox (Xe) was gradually established starting in the 1960s: the proportion of Xe to others gas (A gas is a set of very loosely bonded atoms or molecules and …) rare inthe earth’s atmosphere (The Earth’s atmosphere is the gaseous envelope that surrounds the solid Earth. Dry air is made up of …) – or Martian – is much weaker than expected if we refer to that found in meteorites contemporary to the formation of the solar system (The solar system is a planetary system consisting of a star, the …). This deficit is even more marked for the light isotopes of xenon. One track explored for two decades is the possible chemical reactivity of xenon, although it is a rare gas: under the conditions of pressure (Pressure is a fundamental physical notion. You can think of it as a reported force …) and of temperature (Temperature is a physical quantity measured using a thermometer and …) planetary interiors, reacts with the materials (A material is a material of natural or artificial origin that man shapes to …) silicates in the crust and mantle.

For the first time, the researchers of theInstitute (An institution is a permanent organization created for a specific purpose. It is …) from mineralogy (Mineralogy is the science of studying minerals.)from physicist (Physics (from the Greek φυσις, nature) is etymologically the …) materials and cosmochemistry (IMPMC, CNRS / MNHN / Sorbonne Univ.) and the Laboratoire de physique des deux infinis (LP2i, CNRS / Univ. de Bordeaux), have shown experimentally that this chemical reactivity of xenon leads to greater trapping of its isotopes heavy . The precise measurement of this isotopic fractionation led to the evolution of the scenario of formation of the Earth from impacts between planetary embryos: it took at least a dozen of these impacts to obtain the proportions of Xe measured in its atmosphere (The word atmosphere can have several meanings 🙂. In addition to clarifying the missing xenon paradox, understand the chemistry (Chemistry is a natural science divided into several specialties, a …) of xenon opens up prospects for Research (Scientific research primarily refers to all actions undertaken with a view to …) more applied in the study of nuclear reactors or the space propulsion (This article introduces the concept of space propulsion, i.e. any system capable of …) where there are similar conditions. These works do theobject (In general, the word object (from the Latin objectum, 1361) designates an entity defined in …) of a publication in the journal Nature.

During this collaboration interdisciplinary (Interdisciplinary work incorporates concepts from different disciplines.) (physics, chemistry, planetology), scientists studied the chemical reactivity of xenon by bringing together the gas and silicate minerals, under conditions of high temperature and pressure (3.5 GPa, 800 to 1100 ° C) comparable to those assumed during the formation of the earth. Due to its polarizability, Xe is not like that inert (Inert is the state of doing little or nothing.) chemically compared to other rare gases and can replace a atom (An atom (ancient Greek ἄτομος [atomos]” That…) of Si. The physico-chemical equilibrium of xenon between phase (The word phase can have different meanings, it is used in different fields and …) gas and the mineral phase favors the presence of the heavier isotopes in the mineral phase.

Dissolving the minerals laser (A laser is a device that emits light (electromagnetic radiation) …) to analyze trapped xenon thanks to fine measurements of mass spectrometry (Mass spectrometry (MS) is a physical analysis technique …), the researchers confirmed the effectiveness of this capture in minerals and quantified the resulting enrichment of heavy isotopes. From this measurement they were able to deduce a multi-impact model of the Earth’s formation (figure). In fact, at the moment of impact between two planetary embryos, also called protoplanets, a Ocean (An ocean is often referred to in geography as a vast expanse of water …) magma is formed at such pressures and temperatures that xenon reacts and is trapped in the minerals when the atmosphere containing the gaseous xenon is expelled. Some of the deep-trapped xenon will be released into the atmosphere during the next geological era, particularly by volcanism. A single impact could not explain the currently observed proportion of heavy xenon. It took about ten, which is compatible with the size of the Earth.

Earth formation multi-impact scenario, constructed from measurements of the amount of “heavy” Xe.
a) State of the Earth at the end of the impact n: part of the xenon is trapped deep, the other part is in the atmosphere. Heavy isotopes are more trapped than light isotopes.
b) Impact n + 1: the rocks melt upon impact and a new fraction of the heavy xenon is trapped, the atmosphere is expelled.
c) During the subsequent geological era, the atmosphere is fueled by trapped heavy xenon, in particular by volcanism.
Credit: Chrystèle Sanloup, IMPMC.

Isotopic fractionation of the xenon ocean held in deep silicates.

Igor Rzeplinski, Chrystèle Sanloup, Eric Gilabert and Denis Horlait, Naturepublished June 22, 2022.
DOI: 10.1038 / s41586-022-04710-4

– Chrystèle Sanloup – University Professor, Sorbonne (The Sorbonne is a monumental complex in the Latin Quarter of Paris. It takes its name from …) University (A university is a higher education institution whose goal is the …)the Institute of Mineralogy, Physics of Materials and Cosmochemistry – chrystele.sanloup on
Communication (Communication concerns both man (intrapsychic, interpersonal communication, etc.) INP – at cnr (The National Center for Scientific Research, better known by the acronym CNRS, is the largest …).Fr

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