So Mars pumps methane into the atmosphere

NASA's Curiosity spacecraft. Credits: NASA/Jpl-Caltech/Msss

One of the primary goals of current Mars missions is to detect signs of present or past life on the planet. One of these signs is what insiders call… biofirmeand represents it Methane. Composed of one carbon atom and four hydrogen atoms, this gas is of particular astrobiological interest because of its possible association with microbial life.

On the Red Planet, the molecule has been detected several times by spacecraft curiousity From the mission Mars Science Laboratory. In particular, just above the surface Gale CraterIn the part of the atmosphere in direct contact with the Earth – the so-called Planetary boundary layers Planetary boundary layer (Pbl) – NASA Probe Record Gas concentrations appear to fluctuate seasonally and on a daily time scale. These observations have sparked controversy in the scientific community, due to the failure to detect methane at medium to high altitudes by the European Space Agency's ExoMars spacecraft. Track the gas orbit (Tjo). According to the researchers, this discrepancy between the measurements can be explained by the presence of episodic nature of migration and emission of methane towards the surface, similar to that known on Earth as “natural gas bleeding” (gas leaking, In English), followed by rapid gas destruction.

At this point several questions arise: What is the reason for the accidental nature of the emissions? And again: Since the source of methane on Mars is most likely underground, how can we reconcile atmospheric variations of the gas with a possible transport mechanism?

A team of researchers tried to answer these questions Los Alamos National Laboratory (Lanl) which, using powerful supercomputers, simulated the transport of methane from the Earth's interior to the atmosphere driven by a mechanism involving the release of the gas under the pressure of atmospheric pressure fluctuations. A mechanism known as Air pumping.

In this regard, he explains that “atmospheric systems are linked to changes in atmospheric pressure.” John B. Ortiza researcher at Los Alamos National Laboratory and first author of the book studio Published in the magazine Journal of Geophysical Research – Planets, which displays the search results. “Storm systems, for example, bring low pressure. Clear sky conditions are associated with high pressure. These pressure changes also impose themselves on the soil and rocks beneath our feet. If soil and rock have well-connected fractures, changes in atmospheric pressure can push or pull gases out of these geological materials. This phenomenon is known as atmospheric pumping.”

Illustration showing how an atmospheric pumping mechanism could be responsible for transporting methane from Earth's interior to the surface of Mars. Credit: John P. Ortiz et al., JGR Planets, 2024

In the study, the researchers not only simulated methane transport through this mechanism, but also designed a modelAdsorption Gas molecules on the surface of Martian rocks break down as temperature changes, ultimately assessing how much of the molecule mixes in a simulated planetary boundary layer.

The researchers explain that the methane abundance modeled in this work is controlled by two factors: Underground transportation Driven by air pumping and Planetary boundary layer dynamics.

Scientists add that the results of the simulations are consistent with atmospheric methane emissions that occur in the summer in the Northern Hemisphere before dawn. Confirmation of data obtained by the Curiosity spacecraftUnder which gas levels vary not only seasonally, but also daily.

The methane emission in the models also changed significantly with the size of subsurface cracks, on which the effect of atmospheric pressure on gas transport depends, suggesting that methane variations in Gale Crater are also influenced by the interaction between subsurface geology and atmospheric conditions.

To test the transport mechanism proposed in this study and extend the current characterization of diurnal variation of methane on Mars, the researchers propose a series of measurements using the instrument Tunable laser spectrometer (Tls) aboard the Curiosity rover, scheduled for mid-next summer in the northern hemisphere of Mars. Researchers suggest Two measurement options, one in the mid/late morning and one in the early evening, each of which will allow us to better constrain the apparent morning decrease in methane and the development of the nighttime increase. Moreover, both measurements can support or refute the effect of a transport mechanism, such as atmospheric pumping.

“Our work suggests several key time windows during which Curiosity can collect data,” the researchers concluded. “We believe these time windows provide The best opportunity to constrain the timing of methane fluctuations H – or not – “To bring us closer to understanding their origin on Mars.”

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