Is methane seeping on Mars? NASA scientists explain unusual behaviour of gas on the Red Planet's Gale Crater

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NASA's Curiosity Mars Rover has made the most surprising revelation that methane is seeping from the surface of Gale Crater. 

Since scientists did not find any signs of current or ancient life on Mars, they did not expect the gas to be present there, as living creatures produce most methane.

While SAM (Sample Analysis Mars) or the portable laboratory on Curiosity has detected traces of the gas near the surface of the Gale Crater, the European Space Agency's ExoMars Trace Gas Orbiter found no methane in the atmosphere of the Red Planet.

Furthermore, Gale Crater is the only place on Mars where traces of methane have been found, likely due to geological mechanisms involving water and rocks deep underground. Methane also exhibits unexpected behaviour in Gale Crater by appearing at night and disappearing during the day, fluctuating seasonally, and sometimes spiking 40 times higher than usual.

In March, a NASA research group proposed a paper in the journal Geophysical Research: Planets, explaining why the gas behaves unexpectedly and is present in the Gale Crater. 

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The "soil" on Mars comprises broken rock and dust. The study suggests that the solidified salt formed in the Martian regolith could seal methane underneath despite its origin. The methane could seep out as the temperature rises during warmer seasons or times of day, weakening the seal.

Alexander Pavlov, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, led the research, which suggests that the gas could also erupt in whiffs when the seals crack under the pressure of a small SUV-sized rover.

The origin of this hypothesis goes back to an experiment Pavlov conducted in 2017, which involved growing microorganisms in a simulated Martian permafrost infused with salt. While the microbe-growing results proved inconclusive, the researchers noticed that the top layer of the soil formed a salt crust as salty ice sublimated, turning from a solid to a gas and leaving the salt behind.

The research team tested five samples of permafrost infused with varying concentrations of the salt perchlorate, widely present on Mars. They exposed each sample to different temperatures and air pressure inside a Mars simulation chamber. Periodically, they injected neon, a methane analogue, underneath the soil sample and measured the gas pressure below and above the surface. They found higher pressure under the sample, indicating the gas was trapped. 

Within three to 13 days, a seal formed under the Mars-like conditions only in samples with five to ten per cent perchlorate concentration. However, Curiosity has measured much higher concentration in Gale Crater.

(With inputs from agencies)