Episodic warm climates on early Mars primed by crustal hydration
Abstract
Geological records indicate that the surface of ancient Mars harboured substantial volumes of liquid water, a resource gradually diminished by processes such as the chemical alteration of crustal materials by hydration and atmospheric escape. However, how a relatively warm climate existed on early Mars to support liquid water under a fainter young Sun is debated. Greenhouse gases such as H2 in a CO2-rich atmosphere could have contributed to warming through collision-induced absorption, but whether sufficient H2 was available to sustain warming remains unclear. Here we use a combined climate and photochemical model to simulate how atmospheric chemistry on early Mars responded to water–rock reactions and climate variations, as constrained by existing observations. We find that H2 outgassing from crustal hydration and oxidation, supplemented by transient volcanic activity, could have generated sufficient H2 fluxes to transiently foster warm, humid climates. We estimate that Mars experienced episodic warm periods of an integrated duration of ~40 million years, with each event lasting ≥105 years, consistent with the formation timescale of valley networks. Declining atmospheric CO2 via surface oxidant sinks or variations in the planet’s axial tilt could have led to abrupt shifts in the planet’s redox state and transition to a CO-dominated atmosphere and cold climate.
Copyright and License
© 2025, The Author(s), under exclusive licence to Springer Nature Limited
Acknowledgement
We thank D. Lo, S. Stone, M. Wong and S. Bartlett for valuable discussions and for helpful suggestions to the manuscript. This project was supported in part by a Discovery Fund from Caltech Geological and Planetary Sciences and a Research and Technology Development Fund from JPL. D.A.’s research is funded by NASA through the NASA Hubble Fellowship Program Grant HST-HF2-51523.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5‐26555. This work was supported in part by NASA Habitable Worlds grant NNN13D466T, later changed to 80NM0018F0612. R.H.’s research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. T.B.T. acknowledges funding from the NSF GRFP (DGE-1762114) and the Virtual Planetary Laboratory, a member of NASA NExSS, funded via the NASA Astro-biology Program (grant 80NSSC18K0829). R.W. acknowledges funding from Leverhulme Center for Life in the Universe. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
Data Availability
The data repository with KINETICS output data files is available at https://doi.org/10.7910/DVN/8JCR8U. KINETICS and REDFOX outputs and python scripts to generate Figs. 2–4 and Supplementary Fig. 1 are provided at https://doi.org/10.7910/DVN/QAEOFR.
Code Availability
KINETICS was developed by a combination of authors (D.A. and Y.L.Y.) and many who are not co-authors on this work15,49. Per the KINETICS User Agreement, we do not have permission to distribute the source code, but an executable to reproduce the runs can be provided on reasonable request. REDFOX is IP of DLR Berlin, available to developer and co-author M.S. as a courtesy, but not available for public distribution. Outputs from the model are provided to the reader in ‘Data availability’.
Supplemental Material
Supplementary Information:
Supplementary Figs. 1 and 2, Materials 1 and 2, and Table 1.
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Additional details
- National Aeronautics and Space Administration
- HST-HF2-51523.001-A
- National Aeronautics and Space Administration
- 80NM0018F0612
- National Science Foundation
- DGE-1762114
- Leverhulme Center for Life in the Universe
- Accepted
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2024-12-10Accepted
- Available
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2025-01-15Published online
- Caltech groups
- Division of Geological and Planetary Sciences
- Publication Status
- Published