Seasonality in Mars Atmospheric Methane Driven by Microseepage, Barometric Pumping, Adsorption, and Proximity of the Source to Curiosity
Abstract
Measurements of atmospheric methane by the Curiosity rover's SAM-TLS instrument are providing increasing evidence of seasonality with bimodal peaks in concentration. Given methane's short atmospheric lifetime relative to geological timescales, its presence implies a continuous replenishing source, and the observed seasonality demands the proposition of a modulation mechanism. We focus 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 can explain the observed bimodal peaks in the seasonal variations of methane concentration. In the model, an active, steady-state deep source of methane is assumed, and carbon dioxide flow into/out of the uppermost part of the cryosphere serves as the carrier gas for the vertical transport of methane and other trace constituents to the atmosphere. Our work also presents a comprehensive flow chart for modeling the vertical migration and microseepage of methane on Mars from its origin below the cryosphere to the surface. Our model can accommodate a wide range of hypothesized microseepage rates.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.P23B..03K