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Insights from early life in the 3.45-Ga Kitty’s Gap Chert for the search for elusive life in the Universe

Nature Astronomy volume 9, pages 1615–1623 (2025)Cite this article

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Abstract

The search for extraterrestrial life and habitable planets is at the heart of many space missions. A vast range of biosignatures have been proposed for this purpose, but such signatures are predicated on a concatenation of circumstances related to the geological evolution of the Earth and the co-evolution of life. However, an extraterrestrial observer could probably have detected any biosignature for Earth only in the last 800 Myr, even though Earth has probably been inhabited since the Hadean (4.56–4.0 Ga). The nature of life for the greater part of a planet’s history would thus be undetermined. Here we analyse 3.45-Gyr-old volcanic sediments from the Kitty’s Gap Chert (Pilbara, Australia), a Mars-analogue location, to characterize the nature of the microfossils contained therein. We conclude that the most common forms of extraterrestrial life on a rocky planet will be similar to terrestrial chemotrophic organisms, specifically chemolithotrophs, which are notoriously difficult to detect and identify. This study highlights the difficulties in determining the biogenicity and syngenicity of signatures in a sample and shows the importance of terrestrial analogue examples for demonstrating the methodological challenges.

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Fig. 1: Telescopes involved in the search for habitable planets and life.
Fig. 2: Mineralogical contexts of the purported microfossils in the areas analysed by the J105 cluster SIMS instrument.
Fig. 3: J105 cluster SIMS positive-ion image maps and principal component analysis of areas containing interpreted microfossil colonies.
Fig. 4: Principal component analysis of ROI 2.

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Data availability

The instrumental data supporting the experimental results in this study are available at https://astromat.org and within the manuscript and its Supplementary Information file. Additional information can be provided upon reasonable request.

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Acknowledgements

The following entities are acknowledged for their funding: the CNRS (F.W. and F.F.), the CNES (F.W., F.F. and L.C.), the European Union’s Horizon 2020 Framework Programme, grant number ERC-2020-COG, project 101001311—BIOMAMA (T.M.) and grant ANR-22-CPJ1-0066-01 (T.M.). V. Bazin is thanked for help with the SEM acquisitions.

Author information

Authors and Affiliations

  1. CNRS—Centre de Biophysique Moléculaire, Orléans, France

    Frances Westall, Laura Clodoré & Tetyana Milojevic

  2. Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK

    Graham Purvis

  3. Ionoptika Ltd, Chandler’s Ford, UK

    Naoko Sano

  4. Department of Engineering, University of Newcastle, Newcastle upon Tyne, UK

    Jake Sheriff

  5. CNRS—Conditions Extrêmes et Matériaux: Haute Température et Irradiation, Orléans, France

    Frédéric Foucher

  6. University of Orléans, Orléans, France

    Tetyana Milojevic

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  1. Frances Westall
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Contributions

Conception of the project, sample collection, contribution to all analyses and general interpretation, and writing are attributed to F.W. N.S. carried out the cluster SIMS analysis and interpretation, to which G.P. and J.S. contributed. J.S. carried out the HIM acquisitions; L.C. and F.F. carried out the Raman analyses. T.M. contributed to the microbiology of chemolithotrophs. All authors contributed to the writing.

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Correspondence to Frances Westall.

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Nature Astronomy thanks Dominic Papineau and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Text, Figs. 1–15, Tables 1 and 2 and References.

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Westall, F., Purvis, G., Sano, N. et al. Insights from early life in the 3.45-Ga Kitty’s Gap Chert for the search for elusive life in the Universe. Nat Astron 9, 1615–1623 (2025). https://doi.org/10.1038/s41550-025-02661-0

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