Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust

Abstract As a sub-type of micrometeorites, I-type cosmic spherules form by complete melting and oxidation of extraterrestrial Fe, Ni metal particles during their atmospheric entry. All oxygen in the resulting Fe, Ni oxides sources from the Earth’s atmosphere and hence makes them probes for the compo...

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Main Authors: Fabian Zahnow, Martin D. Suttle, Marina Lazarov, Stefan Weyer, Tommaso Di Rocco, Luigi Folco, Andreas Pack
Format: Article
Language:English
Published: Nature Portfolio 2025-07-01
Series:Communications Earth & Environment
Online Access:https://doi.org/10.1038/s43247-025-02541-5
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author Fabian Zahnow
Martin D. Suttle
Marina Lazarov
Stefan Weyer
Tommaso Di Rocco
Luigi Folco
Andreas Pack
author_facet Fabian Zahnow
Martin D. Suttle
Marina Lazarov
Stefan Weyer
Tommaso Di Rocco
Luigi Folco
Andreas Pack
author_sort Fabian Zahnow
collection DOAJ
description Abstract As a sub-type of micrometeorites, I-type cosmic spherules form by complete melting and oxidation of extraterrestrial Fe, Ni metal particles during their atmospheric entry. All oxygen in the resulting Fe, Ni oxides sources from the Earth’s atmosphere and hence makes them probes for the composition of atmospheric oxygen. When recovered from sedimentary rocks, they allow the reconstruction of the triple oxygen isotope composition of past atmospheric O2, providing quantitative constraints on past CO2 levels or global primary production. Here we establish using fossil I-type cosmic spherules as an archive of Earth’s atmospheric composition with the potential for a unique record of paleo-atmospheric conditions dating back billions of years. We present combined triple oxygen and iron isotope compositions of a collection of fossil I-type cosmic spherules recovered from Phanerozoic sediments. We reconstruct the triple oxygen isotope anomalies of past atmospheric O2 and quantify moderate ancient CO2 levels during the Miocene (~8.5 million years) and late Cretaceous (~87 million years). We also demonstrate this method’s competitive precision for paleo-CO2 determination, despite challenges in finding micrometer-sized unaltered fossil I-type cosmic spherules. Our work indicates that morphologically intact spherules can be isotopically altered by terrestrial processes, underscoring the need for rigorous sample screening.
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spelling doaj-art-e88f987d88dd421d853000056b3c7aaf2025-08-20T04:03:11ZengNature PortfolioCommunications Earth & Environment2662-44352025-07-016111010.1038/s43247-025-02541-5Traces of the oxygen isotope composition of ancient air in fossilized cosmic dustFabian Zahnow0Martin D. Suttle1Marina Lazarov2Stefan Weyer3Tommaso Di Rocco4Luigi Folco5Andreas Pack6Geoscience Center, University of GöttingenSchool of Physical Sciences, The Open UniversityLeibniz University Hannover, Institute of Earth System Sciences (Mineralogy section)Leibniz University Hannover, Institute of Earth System Sciences (Mineralogy section)Geoscience Center, University of GöttingenDipartimento di Scienze della Terra, Università di PisaGeoscience Center, University of GöttingenAbstract As a sub-type of micrometeorites, I-type cosmic spherules form by complete melting and oxidation of extraterrestrial Fe, Ni metal particles during their atmospheric entry. All oxygen in the resulting Fe, Ni oxides sources from the Earth’s atmosphere and hence makes them probes for the composition of atmospheric oxygen. When recovered from sedimentary rocks, they allow the reconstruction of the triple oxygen isotope composition of past atmospheric O2, providing quantitative constraints on past CO2 levels or global primary production. Here we establish using fossil I-type cosmic spherules as an archive of Earth’s atmospheric composition with the potential for a unique record of paleo-atmospheric conditions dating back billions of years. We present combined triple oxygen and iron isotope compositions of a collection of fossil I-type cosmic spherules recovered from Phanerozoic sediments. We reconstruct the triple oxygen isotope anomalies of past atmospheric O2 and quantify moderate ancient CO2 levels during the Miocene (~8.5 million years) and late Cretaceous (~87 million years). We also demonstrate this method’s competitive precision for paleo-CO2 determination, despite challenges in finding micrometer-sized unaltered fossil I-type cosmic spherules. Our work indicates that morphologically intact spherules can be isotopically altered by terrestrial processes, underscoring the need for rigorous sample screening.https://doi.org/10.1038/s43247-025-02541-5
spellingShingle Fabian Zahnow
Martin D. Suttle
Marina Lazarov
Stefan Weyer
Tommaso Di Rocco
Luigi Folco
Andreas Pack
Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
Communications Earth & Environment
title Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
title_full Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
title_fullStr Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
title_full_unstemmed Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
title_short Traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
title_sort traces of the oxygen isotope composition of ancient air in fossilized cosmic dust
url https://doi.org/10.1038/s43247-025-02541-5
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