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.

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 anticipate finding methane there. But, the moveable chemistry lab aboard Curiosity, often called 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 had been the entire story, issues could be simple. Nevertheless, SAM has discovered that methane behaves in sudden methods in Gale Crater. It seems at evening and disappears through the day. It fluctuates seasonally, and typically spikes to ranges 40 instances greater than typical. Surprisingly, the methane additionally is not accumulating within the environment: ESA’s (the European House 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 Purple Planet whereas others do not?

“It is a story with numerous plot twists,” mentioned 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 initiatives that intention to clarify why the fuel behaves unusually and is detected solely in Gale Crater. A NASA analysis group not too long ago shared an fascinating proposal.

Reporting in a March paper in the Journal of Geophysical Research: Planets, the group prompt that methane—regardless of the way it’s produced—might be sealed beneath solidified salt which may type in Martian regolith, which is “soil” manufactured from damaged rock and dust. When temperature rises throughout hotter seasons or instances of day, weakening the seal, the methane may seep out.

Led by Alexander Pavlov, a planetary scientist at NASA’s Goddard House Flight Middle in Greenbelt, Maryland, the researchers recommend the fuel can also erupt in puffs when seals crack beneath the strain 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, on condition that’s it is considered one 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 would 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 called halophiles, which stay in saltwater lakes and different salt-rich environments on Earth, may 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 stable to a fuel and leaving the salt behind.

Permafrost on Mars and Earth

“We did not assume a lot of it in the meanwhile,” Pavlov mentioned, however he remembered the soil crust in 2019, when SAM’s tunable laser spectrometer detected a methane burst nobody may clarify.

“That is when it clicked in my thoughts,” Pavlov mentioned. And that is when he and a group started testing the situations that would type and crack hardened salt seals.

Pavlov’s group examined 5 samples of permafrost infused with various concentrations of a salt known as perchlorate that is widespread on Mars. (There’s doubtless no permafrost in Gale Crater in the present day, however the seals may have shaped way back when Gale was colder and icier.) The scientists uncovered every pattern to totally different temperatures and air strain 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 strain beneath and above it. Larger strain beneath the pattern implied the fuel was trapped. Finally, a seal shaped beneath 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 distinct kind of salt minerals known as sulfates, which Pavlov’s group needs to check subsequent to see if they will 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 era and destruction processes on Mars is a key advice from the 2022 NASA Planetary Mission Senior Assessment, and theoretical work like Pavlov’s is vital to this effort. Nevertheless, scientists say additionally they want extra constant methane measurements.

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

“Methane experiments are useful resource intensive, so now we have to be very strategic after we resolve to do them,” mentioned Goddard’s Charles Malespin, principal investigator for SAM.

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

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