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

Probably 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.

Dwelling creatures produce a lot 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 moveable chemistry lab aboard Curiosity, referred to as SAM, or Pattern Evaluation at Mars, has frequently sniffed out traces of the fuel close to the floor of Gale Crater, the one place on the floor of Mars the place methane has been detected so far. Its doubtless 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 sudden methods in Gale Crater. It seems at evening and disappears throughout the day. It fluctuates seasonally, and typically spikes to ranges 40 occasions greater than normal. Surprisingly, the methane additionally is not accumulating within the environment: ESA’s (the European Area Company) ExoMars Hint Gasoline Orbiter, despatched to Mars particularly to check the fuel within the environment, has detected no methane.

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

“It is a story with a whole lot of plot twists,” mentioned Ashwin Vasavada, Curiosity’s challenge 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 purpose to elucidate why the fuel behaves unusually and is detected solely in Gale Crater. A NASA analysis group lately shared an fascinating proposal.

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

Led by Alexander Pavlov, a planetary scientist at NASA’s Goddard Area Flight Middle in Greenbelt, Maryland, the researchers counsel the fuel 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 group’s speculation could assist clarify why methane is detected solely in Gale Crater, Pavlov mentioned, provided that’s it is one in all 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 referred to as halophiles, which reside in saltwater lakes and different salt-rich environments on Earth, might thrive in comparable situations on Mars.

The microbe-growing outcomes proved inconclusive, he mentioned, however the researchers seen one thing sudden: The highest layer of soil shaped a salt crust as salty ice sublimated, turning from a strong to a fuel and leaving the salt behind.

Permafrost on Mars and Earth

“We did not assume a lot of it in the mean time,” Pavlov mentioned, 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 mentioned. And that is when he and a group started testing the situations that might type and crack hardened salt seals.

Pavlov’s group examined 5 samples of permafrost infused with various concentrations of a salt referred to as perchlorate that is widespread on Mars. (There’s doubtless no permafrost in Gale Crater immediately, however the seals might have shaped 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 group injected neon, a methane analog, beneath the soil pattern and measured the fuel stress under and above it. Larger stress beneath the pattern implied the fuel was trapped. In the end, a seal shaped underneath Mars-like situations 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 kind of salt minerals referred to as sulfates, which Pavlov’s group needs to check subsequent to see if they’ll additionally type seals.

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

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

SAM sniffs for methane solely a number of occasions a yr 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 now have to be very strategic after we determine to do them,” mentioned Goddard’s Charles Malespin, principal investigator for SAM.

But, to check how usually methane ranges spike, for example, would require a brand new technology 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 might be extra centered on answering these particular questions,” Vasavada mentioned.