Short-term variation in Mars atmospheric methane concentrations driven by barometric pumping

Creators: Klusman, Ronald W.¹; Luo, Yangcheng²; Chen, Pin³; Mischna, Michael A.³; Yung, Yuk L.²

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

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Abstract

Measurements of atmospheric methane by the Curiosity rover's SAM-TLS instrument are providing evidence of seasonality and diurnal variation in concentration. Given methane's short atmospheric lifetime relative to geological timescales, its presence implies a replenishing source, and the observed variation demands the proposition of a modulation mechanism. This paper focuses on the modulation mechanism on a diurnal scale, extending earlier modeling of seasonal variation. Our modeling shows that barometric pumping driven by both diurnal and seasonal variation of atmospheric pressure, along with possible adsorption and desorption of methane in the shallow subsurface driven by temperature and pressure change, can explain the variation in 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 drawing methane and possible trace gaseous constituents into the atmosphere.

Copyright and License

This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/bync/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 (80NM0018D0004) where PC and MAM are employed. Yangcheng Luo is a graduate student supported by Professor Yuk L. Yung from a Caltech account YLY.2500006-1-OAID.CITRESRCH. YLY acknowledges support from the Virtual Planetary Laboratory at the University of Washington. Two anonymous reviewers provided thorough and useful comments on the manuscript as it has evolved.

Contributions

RWK proposed the original hydrate model in Klusman (2019, 2020), the subsequent microseepage model, and wrote the coding contained in the custom programs VERTMIG2, BAROADS2, BAROADS3, and preliminary gravity modeling. YL obtained TREMS, PREMS, barometric pressure and optical density data from original sources and developed improved figures. MAM suggested that diurnal barometric pumping was of significance in addition to the seasonal barometric pumping. PC and YLY advised the team regarding the geochemical, atmospheric, and observational contexts on Mars.

Data Availability

The input data file contained in Table 1 and the large output data file for the Southern Hemisphere summer “favorable” flux season is contained in a California Institute of Technology data repository: (https://data.caltech.edu/records/3qjaa-c1j77). The output file contains data extracted and used in the construction of Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6.

Conflict of Interest

The authors have no competing interests. This manuscript has not been submitted for publication elsewhere.

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