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An interstellar energetic and non-aqueous pathway to peptide formation

Nature Astronomy (2026)Cite this article

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Abstract

The origin of the molecular building blocks of life is a central question in science. A few α-amino acids, such as glycine, the simplest proteinogenic amino acid, have been detected in meteorites and comets, indicating an extraterrestrial origin for some prebiotic molecules. However, the formation of peptides, short chains of α-amino acids linked by peptide bonds, has remained unresolved under astrophysical conditions. Here we show that the building blocks of proteins can form in interstellar ice analogues exposed to ionizing radiation without the presence of liquid water. Using isotopically labelled glycine irradiated with protons at cryogenic temperatures, we detect the formation of glycylglycine, the simplest dipeptide, along with deuterated and undeuterated water as by-products. The formation of peptide bonds is confirmed by infrared spectroscopy and high-resolution mass spectrometry, which also reveal the production of other complex organic species. These findings demonstrate a non-aqueous route to peptide formation under space-like conditions and suggest that such molecules could form in the cold interstellar medium and be incorporated into forming planetary systems. Our results challenge aqueous-centric models of early biochemical evolution and broaden potential settings for the origins of life.

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Fig. 1: Peptide formation induced by energetic processing in the ISM.
Fig. 2: FTIR spectra of the three glycine isotopologues and their changes during 10-keV proton exposure.
Fig. 3: QMS detections of H2O, HDO and D2O with the corresponding FTIR spectra during TPD measurements of all three glycine isotopologues after proton exposure.
Fig. 4: Number of D2O and H2O molecules normalized to the final irradiation yield plotted as a function of the fluence of proton bombardment, showing the rate of formation.
Fig. 5: FTIR spectra of the residue obtained after processing glycine with 1-MeV protons with a fluence of 1.24 × 1015 H+ cm−2.
Fig. 6: Selected ex situ ESI-MS data on the newly detected molecules with some of the larger masses labelled.

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Data availability

Data for this project are available via Zenodo at https://doi.org/10.5281/zenodo.17814722 (ref. 53).

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Acknowledgements

Support from the Danish National Research Foundation through the Centre of Excellence InterCat (Grant Agreement No. DNRF150) is acknowledged by A.T.H., A.M.W., J.P., A.T.M., L.H. and S.I. The research was supported by the Europlanet 2024 RI, which was funded by the European Union Horizon 2020 Research Innovation Programme (Grant Agreement No. 871149) and is acknowledged by A.T.H. and N.J.M. The main components of the ICA set-up were purchased using funds obtained from the Royal Society through Grant Nos. UF130409, RGF/EA/180306 and URF/R/191018 and are acknowledged by S.I. Further developments of the installation were supported in part by the Eötvös Loránd Research Network (Grant Nos. ELKH IF-2/2019 and ELKH IF-5/2020) and are acknowledged by R.R., P.H., G.L., S.B., Z.J., D.V.M., B.S., R.W.M. and N.J.M. This work has also received support from the European Union and the State of Hungary, cofinanced by the European Regional Development Fund (Grant No. GINOP-2.3.3-15-2016-00005). Support has also been received from the Research, Development, and Innovation Fund of Hungary (Grant Nos. K128621 and ADVANCED-151196). These grants are acknowledged by R.R., P.H., G.L., S.B., Z.J., D.V.M., B.S., R.W.M. and N.J.M. This paper is also based on work from the COST Actions CA20129 MultIChem and CA22133 PLANETS, which are supported by COST (European Cooperation in Science and Technology) and are acknowledged by R.R., P.H., G.L., S.B., Z.J., D.V.M., B.S., R.W.M. and N.J.M. Z.J. is grateful for the support of the Hungarian Academy of Sciences through the János Bolyai Research Scholarship. R.W.M. is the grateful recipient of an honorary visiting scholar post at Queen’s University Belfast.

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Authors and Affiliations

  1. Center for Interstellar Catalysis, Physics and Astronomy Department, Aarhus University, Aarhus, Denmark

    Alfred Thomas Hopkinson, Ann Mary Wilson, Joe Pitfield, Liv Hornekær & Sergio Ioppolo

  2. School of Electronic Engineering and Computer Science, Queen Mary University of London, London, UK

    Alejandra Traspas Muiña

  3. HUN-REN Institute for Nuclear Research (Atomki), Debrecen, Hungary

    Richárd Rácz, Duncan V. Mifsud, Péter Herczku, Gergö Lakatos, Béla Sulik, Zoltán Juhász & Sándor Biri

  4. Institute of Chemistry, University of Debrecen, Debrecen, Hungary

    Gergö Lakatos

  5. Doctoral School of Chemistry, University of Debrecen, Debrecen, Hungary

    Gergö Lakatos

  6. Department of Physics and Astronomy, School of Mathematics and Physics, Queen’s University Belfast, Belfast, UK

    Robert W. McCullough & Nigel J. Mason

  7. Centre for Astrophysics and Planetary Science (CAPS), School of Physics and Astronomy, University of Kent, Canterbury, UK

    Nigel J. Mason

  8. Department of Molecular Biology and Genetics – Protein Science, Aarhus University, Aarhus, Denmark

    Carsten Scavenius

  9. Interdisciplinary Nanoscience Center, Aarhus University, Aarhus, Denmark

    Liv Hornekær

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  1. Alfred Thomas Hopkinson
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Contributions

A.T.H. conceived the experiments with input from S.I. and L.H. A.T.H., A.M.W. and A.T.M. conducted the IR and QMS experiments, and A.T.H. analysed the results with input from S.I. and L.H. R.R., P.H., G.L., S.B., Z.J., D.V.M., B.S., R.W.M. and N.J.M. enabled the irradiation experiments at HUN-REN Atomki. C.S. conducted the ex situ ESI-MS experiments, and A.T.H. and C.S. analysed the results. J.P. conducted the theoretical calculations, and A.T.H. and J.P. analysed the results. A.T.H., C.S., J.P. and S.I. wrote the draft paper. All authors reviewed the paper.

Corresponding authors

Correspondence to Alfred Thomas Hopkinson or Sergio Ioppolo.

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Nature Astronomy thanks Guillermo Munoz Caro and Sergio Pilling and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary discussion relating to the main paper finding. Contains Supplementary Figs. 1–7 and Tables 1 and 2.

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Hopkinson, A.T., Wilson, A.M., Pitfield, J. et al. An interstellar energetic and non-aqueous pathway to peptide formation. Nat Astron (2026). https://doi.org/10.1038/s41550-025-02765-7

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