Letter

Prebiotic chemistry and atmospheric warming of early Earth by an active young Sun

Received:
Accepted:
Published online:

Abstract

Nitrogen is a critical ingredient of complex biological molecules1. Molecular nitrogen, however, which was outgassed into the Earth’s early atmosphere2, is relatively chemically inert and nitrogen fixation into more chemically reactive compounds requires high temperatures. Possible mechanisms of nitrogen fixation include lightning, atmospheric shock heating by meteorites, and solar ultraviolet radiation3,4. Here we show that nitrogen fixation in the early terrestrial atmosphere can be explained by frequent and powerful coronal mass ejection events from the young Sun—so-called superflares. Using magnetohydrodynamic simulations constrained by Kepler Space Telescope observations, we find that successive superflare ejections produce shocks that accelerate energetic particles, which would have compressed the early Earth’s magnetosphere. The resulting extended polar cap openings provide pathways for energetic particles to penetrate into the atmosphere and, according to our atmospheric chemistry simulations, initiate reactions converting molecular nitrogen, carbon dioxide and methane to the potent greenhouse gas nitrous oxide as well as hydrogen cyanide, an essential compound for life. Furthermore, the destruction of N2, CO2 and CH4 suggests that these greenhouse gases cannot explain the stability of liquid water on the early Earth. Instead, we propose that the efficient formation of nitrous oxide could explain a warm early Earth.

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Acknowledgements

This work was supported by NASA GSFC Science Task Group funds. V.S.A. performed the part of this work while staying at ELSI/Tokyo Tech. G.G. was supported by NASA Astrobiology Institute grant NNX15AE05G and by the NASA HIDEE Program, E.H. was supported by an appointment to the NASA Postdoctoral Program at NASA Goddard Space Flight Center, administered by Universities Space Research Association through a contract with NASA.

Author information

Affiliations

  1. NASA Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, Maryland 20771, USA

    • V. S. Airapetian
    • , A. Glocer
    • , E. Hébrard
    •  & W. Danchi
  2. Science Systems and Application, Inc. & NASA Langley Research Center, Hampton, Virginia 23681, USA

    • G. Gronoff
  3. NASA Postdoctoral Program, Universities Space Research Association, Columbia, Maryland 21046, USA

    • E. Hébrard

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Contributions

V.S.A. conceived and designed the numerical experiments, analysed the data, contributed materials and wrote the manuscript. A.G. and G.G. contributed to the development and execution of codes and data analysis. E.H. contributed to the chemistry model and data analysis, W.D. contributed to development of the manuscript, to data analysis and proofreading of the paper.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to V. S. Airapetian.

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