Seasonality in Mars atmospheric methane driven by microseepage, barometric pumping, and adsorption

Creators: Klusman, Ronald W.¹; Luo, Yangcheng²; Chen, Pin³; Yung, Yuk L.²; Tallapragada, Sindhoora³

1. Colorado School of Mines
2. California Institute of Technology
3. Jet Propulsion Lab

Abstract

Measurements of atmospheric methane by the Curiosity rover's SAM-TLS instrument are providing evidence of seasonality with bimodal peaks in concentration. Given methane's short atmospheric lifetime relative to geological timescales, its presence implies a replenishing source, and the observed seasonality demands the proposition of a modulation mechanism. This paper focuses on the modulation mechanism. Our modeling study shows that barometric pumping driven by seasonal variation of atmospheric pressure, along with adsorption and desorption of methane in the shallow subsurface driven by temperature change, can explain the observed bimodal peaks in the seasonal variations of methane concentration. In the model, an active, continuous, steady-state deep source of methane is assumed, and carbon dioxide serves as the carrier gas for producing seasonal variation in the upper part of the sedimentary column for methane and other possible trace gaseous constituents. Our work also presents a comprehensive flow chart for modeling the microseepage of methane on Mars from first principles.

Copyright and License

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).

Acknowledgement

RWK is an Emeritus Professor and has conducted this research on a part-time basis without an external source of funding. A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Yangcheng Luo is a graduate student supported by Professor Yuk L. Yung from a Caltech account YLY.2500006-1-OAID.CITRESRCH. YLY acknowledged support from the Virtual Planetary Laboratory at the University of Washington. We thank the Keck Institute for Space Studies (KISS) for hosting and supporting the "Methane on Mars" workshops, which were seminal to this collaborative research. An anonymous reviewer and P.-Y. Meslin contributed a thorough analysis of the manuscript with suggestions for revision and clarification.

Contributions

RWK proposed the original hydrate model in Klusman, 2019, Klusman, 2020, the subsequent microseepage model, and wrote the coding contained in the custom programs VERTMIG2 and BAROADS2. YL obtained TREMS, PREMS, and optical density data from original sources, β-tested some of the computer code which continues, and developed improved figures; ST completed background work on brine composition used in Bridges et al. (2015); PC and YLY served as advisors based on their considerable planetary science experience and encouragement to RWK.

Supplemental Material

Supplementary material - Seasonality in Mars Atmospheric Methane - data (DOCX)

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