Mass- independent fractionation of oxygen isotopes during high- temperature condensation in cosmochemical plasmas

• 成果类型: Article
• 署名作者: Asset, Nathan; Chaussidon, Marc; Lombardi, Guillaume; Villeneuve, Johan; Tartese, Romain; Mostefaoui, Smail; Robert, Francois
• 署名单位: Centre National de la Recherche Scientifique (CNRS); Universite Paris Cite; Centre National de la Recherche Scientifique (CNRS); Universite de Lorraine; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute for Earth Sciences & Astronomy (INSU); University of Manchester; Museum National d'Histoire Naturelle (MNHN); Centre National de la Recherche Scientifique (CNRS); Sorbonne Universite; Universite Paris Cite; CNRS - Institute of Physics (INP)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2426711122
• 发表日期: 2025-05-06
• 页码: e2426711122
• 关键词: condensation; oxygen mass-independent isotopic fractionation; plasma experiments; protosolar nebula; solar-system; origin; hydrogen; ozone

摘要

Contrary to all terrestrial rocks, planets and meteorites exhibit oxygen isotope variations decorrelated with the mass difference of their atomic nuclei. It has been proposed that, in the protosolar nebula (PSN), these variations could result from mass independent isotopic fractionation (MIF) either during specific chemical reactions similar to those responsible for the formation of ozone in the Earth's atmosphere or during ultraviolet (UV)- photolysis of carbon monoxide (CO) gas in the PSN. However, these potential chemical MIF reactions (Chem-MIFs) are not identified in conditions close to the PSN, and there is no experimental demonstration that large MIF signature can be transferred to solids forming in the PSN. Here, we show that MIFs, up to 60 parts per thousand depletion in 16O, are produced by high-temperature reactions in a plasma during the condensation of carbonaceous solids from a gas containing two of the most abundant PSN molecular species (H2O and CH4). This effect is attributed to the formation in the plasma of the activated complex H2O2* followed by its stabilization by reactions with CHx center dot radicals. Although it is premature to assert that this reaction represents the main process resulting in MIF of oxygen isotopes in the solar system, our result demonstrates the potential importance of a Chem-MIF effect in a PSN where plasma zones develop.