A nitrogen-rich atmosphere on ancient Mars consistent with isotopic evolution models
- Creators
- Hu, Renyu
- Thomas, Trent B.
Abstract
The ratio of nitrogen isotopes in the Martian atmosphere is a key constraint on the planet's atmospheric evolution. However, enrichment of the heavy isotope expected due to atmospheric loss from sputtering and photochemical processes is greater than measurements. A massive, multi-bar early CO₂-dominated atmosphere and recent volcanic outgassing have been proposed to explain this discrepancy, and many previous models have assumed atmospheric nitrogen rapidly reached a steady state where loss to space balanced volcanic outgassing. Here we show using time-dependent models that the abundance and isotopic composition of nitrogen in the Martian atmosphere can be explained by a family of evolutionary scenarios in which the initial partial pressure of nitrogen is sufficiently high that a steady state is not reached and nitrogen levels gradually decline to present-day values over 4 billion years. Our solutions do not require a multi-bar early CO₂ atmosphere and are consistent with volcanic outgassing indicated by both geologic mapping and the atmospheric ³⁶Ar/³⁸Ar ratio. Monte Carlo simulations that include these scenarios estimate that the partial pressure of N₂ was 60–740 mbar (90% confidence, with a median value of 310 mbar) at 3.8 billion years ago when the valley networks formed. We suggest that such a high nitrogen partial pressure could have contributed substantially to warming on early Mars.
Additional Information
© 2022 Nature Publishing Group. Received 27 May 2020; Accepted 16 December 2021; Published 10 February 2022. We thank Y. L. Yung, B. Ehlmann, B. Jakosky, H. Kurokawa, C. Manning, R. Johnson, M. Grott, F. Gaillard, M. Slipski and C.-Y. Ng for helpful discussions. This work was supported by NASA Habitable Worlds grant NNN13D466T, later changed to 80NM0018F0612. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Data availability: The data needed to generate all figures in the main text (Figs. 1–3) and Extended Data Figs. 2 and 3 are publicly available at Zenodo (https://doi.org/10.5281/zenodo.5760095). Code availability: The source code of the nitrogen evolution model and the associated configuration files used in this study are publicly available at Zenodo (https://doi.org/10.5281/zenodo.5760095). Author Contributions: R.H. designed the study and the evolution model, interpreted the results and wrote the manuscript. T.B.T. implemented the evolution model, carried out the simulations and interpreted the results. The authors declare no competing interests. Peer review information: Nature Geoscience thanks Ramses Ramirez and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editors: Tamara Goldin; Xujia Jiang; Stefan Lachowycz.Attached Files
Accepted Version - 2202.04825.pdf
Supplemental Material - 41561_2021_886_Fig4_ESM.webp
Supplemental Material - 41561_2021_886_Fig5_ESM.webp
Supplemental Material - 41561_2021_886_Fig6_ESM.webp
Supplemental Material - 41561_2021_886_Fig7_ESM.webp
Supplemental Material - 41561_2021_886_Fig8_ESM.webp
Supplemental Material - 41561_2021_886_Fig9_ESM.webp
Supplemental Material - 41561_2021_886_MOESM1_ESM.pdf
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Additional details
- Eprint ID
- 113516
- Resolver ID
- CaltechAUTHORS:20220222-671676600
- NNN13D466T
- NASA
- 80NM0018F0612
- NASA
- NASA/JPL/Caltech
- Created
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2022-02-22Created from EPrint's datestamp field
- Updated
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2022-05-17Created from EPrint's last_modified field