Quantifying Methane Fluxes on Mars: Modeling the Vertical Evolution of Martian Methane for Improved Detection and Analysis

Searching for the presence of biosignatures on Mars is central to understanding and discovering clues to the geological and chemical history of the planet, and may lead us to unexpected discoveries. Methane has been observed in the Martian atmosphere for several decades, however, our understanding of the behavior of methane on Mars remains limited, particularly in terms of its diurnal variations, and its sources and sinks. On Earth, methane is regulated largely by biological activity, thus the presence of methane on Mars raises the question of whether the source of Martian methane is geochemical or biogenic in origin. Measurements of methane by the Sample Analysis at Mars Tunable Laser Spectrometer (SAM-TLS) aboard NASA's Curiosity Rover have revealed a background seasonal cycle of methane, though no measurement of the full diurnal cycle have yet been made. We use global circulation model (GCM) outputs to model the diurnal vertical evolution of methane on Mars and the strength of its flux from the surface. We also look at the allowable flight temperatures (AFT) for a dedicated instrument that is able to sample the Martian atmosphere hourly at sub-ppbv levels to better characterize the Martian methane cycle. The precision of such an instrument relies on the cooling of the gas sample, which must be kept free of condensing water vapor. Therefore, we look at the variability of the water frost point which reveals the areas of the Martian surface at which the instrument is most sensitive.