Why is methane seeping on Mars? NASA scientists have new ideas

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Full of briny lakes, the Quisquiro salt flat in South America’s Altiplano area represents the sort of panorama that scientists suppose could have existed in Gale Crater on Mars, which NASA’s Curiosity Rover is exploring. Credit score: Maksym Bocharov

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Full of briny lakes, the Quisquiro salt flat in South America’s Altiplano area represents the sort of panorama that scientists suppose could have existed in Gale Crater on Mars, which NASA’s Curiosity Rover is exploring. Credit score: Maksym Bocharov

Essentially the most stunning revelation from NASA’s Curiosity Mars Rover—that methane is seeping from the floor of Gale Crater—has scientists scratching their heads.

Residing creatures produce many of the methane on Earth. However scientists have not discovered convincing indicators of present or historic life on Mars, and thus did not look forward to finding methane there. But, the transportable chemistry lab aboard Curiosity, often known as SAM, or Pattern Evaluation at Mars, has frequently sniffed out traces of the gasoline close to the floor of Gale Crater, the one place on the floor of Mars the place methane has been detected up to now. Its seemingly supply, scientists assume, are geological mechanisms that contain water and rocks deep underground.

If that have been the entire story, issues can be straightforward. Nevertheless, SAM has discovered that methane behaves in surprising methods in Gale Crater. It seems at evening and disappears throughout the day. It fluctuates seasonally, and generally spikes to ranges 40 instances greater than traditional. Surprisingly, the methane additionally is not accumulating within the ambiance: ESA’s (the European Area Company) ExoMars Hint Gasoline Orbiter, despatched to Mars particularly to review the gasoline within the ambiance, has detected no methane.

Why do some science devices detect methane on the Purple Planet whereas others do not?

“It is a story with quite a lot of plot twists,” stated Ashwin Vasavada, Curiosity’s mission scientist at NASA’s Jet Propulsion Laboratory in Southern California, which leads Curiosity’s mission.

Methane retains Mars scientists busy with lab work and laptop modeling tasks that goal to clarify why the gasoline behaves unusually and is detected solely in Gale Crater. A NASA analysis group lately shared an attention-grabbing proposal.

Reporting in a March paper within the Journal of Geophysical Analysis: Planets, the group advised that methane—irrespective of the way it’s produced—may very well be sealed underneath solidified salt that may kind in Martian regolith, which is “soil” manufactured from damaged rock and mud. When temperature rises throughout hotter seasons or instances of day, weakening the seal, the methane might seep out.

Led by Alexander Pavlov, a planetary scientist at NASA’s Goddard Area Flight Heart in Greenbelt, Maryland, the researchers counsel the gasoline can also erupt in puffs when seals crack underneath the stress of, say, a rover the dimensions of a small SUV driving over it. The staff’s speculation could assist clarify why methane is detected solely in Gale Crater, Pavlov stated, on condition that’s it is one in every of two locations on Mars the place a robotic is roving and drilling the floor. (The opposite is Jezero Crater, the place NASA’s Perseverance rover is working, although that rover does not have a methane-detecting instrument.)

Pavlov traces the origin of this speculation to an unrelated experiment he led in 2017, which concerned rising microorganisms in a simulated Martian permafrost (frozen soil) infused with salt, as a lot of Martian permafrost is.

Pavlov and his colleagues examined whether or not micro organism often known as halophiles, which stay in saltwater lakes and different salt-rich environments on Earth, might thrive in related circumstances on Mars.

The microbe-growing outcomes proved inconclusive, he stated, however the researchers observed one thing surprising: The highest layer of soil fashioned a salt crust as salty ice sublimated, turning from a stable to a gasoline and leaving the salt behind.

In 2018, NASA introduced that the Pattern Evaluation at Mars chemistry lab aboard the Curiosity Rover found historic natural molecules that had been preserved in rocks for billions of years. Findings like this one assist scientists perceive the habitability of early Mars and pave the best way for future missions to the Purple Planet. Credit score: NASA’s Goddard Area Flight Heart

Permafrost on Mars and Earth

“We did not suppose a lot of it in the intervening time,” Pavlov stated, however he remembered the soil crust in 2019, when SAM’s tunable laser spectrometer detected a methane burst nobody might clarify.

“That is when it clicked in my thoughts,” Pavlov stated. And that is when he and a staff started testing the circumstances that might kind and crack hardened salt seals.

Pavlov’s staff examined 5 samples of permafrost infused with various concentrations of a salt referred to as perchlorate that is widespread on Mars. (There’s seemingly no permafrost in Gale Crater at this time, however the seals might have fashioned way back when Gale was colder and icier.) The scientists uncovered every pattern to totally different temperatures and air stress inside a Mars simulation chamber at NASA Goddard.

Periodically, Pavlov’s staff injected neon, a methane analog, beneath the soil pattern and measured the gasoline stress under and above it. Increased stress beneath the pattern implied the gasoline was trapped. In the end, a seal fashioned underneath Mars-like circumstances inside three to 13 days solely in samples with 5% to 10% perchlorate focus.

That is a a lot greater salt focus than Curiosity has measured in Gale Crater. However regolith there may be wealthy in a special sort of salt minerals referred to as sulfates, which Pavlov’s staff needs to check subsequent to see if they’ll additionally kind seals.

Curiosity rover has arrived at a area believed to have fashioned as Mars’ local weather was drying.

Bettering our understanding of methane era and destruction processes on Mars is a key advice from the 2022 NASA Planetary Mission Senior Evaluate, and theoretical work like Pavlov’s is crucial to this effort. Nevertheless, scientists say additionally they want extra constant methane measurements.

SAM sniffs for methane solely a number of instances a 12 months as a result of it’s in any other case busy doing its main job of drilling samples from the floor and analyzing their chemical make-up.

“Methane experiments are useful resource intensive, so we’ve to be very strategic once we determine to do them,” stated Goddard’s Charles Malespin, principal investigator for SAM.

But, to check how typically methane ranges spike, as an example, would require a brand new era of floor devices that measure methane constantly from many places throughout Mars, scientists say.

“A few of the methane work must be left to future floor spacecraft which can be extra targeted on answering these particular questions,” Vasavada stated.

Extra info:
Alexander A. Pavlov et al, Formation and Stability of Salty Soil Seals in Mars‐Like Circumstances. Implications for Methane Variability on Mars, Journal of Geophysical Analysis: Planets (2024). DOI: 10.1029/2023JE007841

Journal info:
Journal of Geophysical Analysis


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