However, SAM has also observed that the methane's presence is transient and variable. It emerges at night and vanishes by day, with seasonal fluctuations and occasional surges up to 40 times above normal levels. Intriguingly, the European Space Agency's ExoMars Trace Gas Orbiter, tasked specifically with studying Martian atmospheric gases, has not detected methane, adding to the enigma.
"It's a story with a lot of plot twists," explained Ashwin Vasavada, project scientist for Curiosity at NASA's Jet Propulsion Laboratory.
A new theory proposed by NASA researchers may shed light on this mystery. Detailed in a recent study published in the Journal of Geophysical Research: Planets, the team suggests that methane might be trapped under salt formations within the Martian soil, known as regolith. These salt caps could periodically break, releasing methane, especially under conditions like temperature increases or physical disturbances, such as those caused by rover activity.
The hypothesis originated from Alexander Pavlov's earlier unrelated experiments with Martian permafrost models, which inadvertently produced a salt crust that could potentially seal and release gases. Testing this theory, Pavlov's team at NASA's Goddard Space Flight Center simulated Martian conditions, revealing that gas could indeed be trapped and then released from beneath these seals, depending on environmental conditions.
"This could explain why we only detect methane in specific conditions and locations, such as Gale Crater," Pavlov stated. His team plans to further investigate the role of different Martian salts in gas entrapment.
This research is part of ongoing efforts to understand methane's role and behavior on Mars, highlighted as a key area of interest in the 2022 NASA Planetary Mission Senior Review. Consistent and comprehensive methane tracking is necessary, notes Charles Malespin, SAM's principal investigator, but is challenging due to the resource demands of such experiments.
"Methane studies are complex and require strategic planning," Malespin said. Future missions equipped with advanced surface instruments will likely continue this investigation, aiming to resolve these Martian methane mysteries definitively.
Research Report:Formation and Stability of Salty Soil Seals in Mars-Like Conditions. Implications for Methane Variability on Mars
Related Links
2022 NASA Planetary Mission Senior Review
Mars News and Information at MarsDaily.com
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