Crammed with briny lakes, the Quisquiro salt flat in South America’s Altiplano represents the sort of panorama that scientists assume could have existed in Gale Crater, which NASA’s Curiosity rover is exploring. This salt flat is positioned in Chile, although the Altiplano sprawls throughout international locations. Streams and rivers flowing from mountain ranges into this arid, high-altitude plateau result in closed basins much like Mars’ historical Gale Crater. Lakes on the Altiplano are closely influenced by local weather in the identical manner as Gale. — NASA
A latest paper could assist clarify why a transportable chemistry lab on NASA’s Curiosity rover has regularly sniffed out traces of the gasoline close to the floor of Gale Crater.
Probably the most shocking 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 haven’t discovered convincing indicators of present or historical life on Mars, and thus didn’t anticipate finding methane there. But, the moveable chemistry lab aboard Curiosity, referred to as SAM, or Pattern Evaluation at Mars, has regularly 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. Nonetheless, SAM has discovered that methane behaves in sudden methods in Gale Crater. It seems at evening and disappears in the course of the day. It fluctuates seasonally and generally spikes to ranges 40 occasions greater than typical. Surprisingly, the methane additionally isn’t accumulating within the ambiance: ESA’s (the European Area Company) ExoMars Hint Fuel Orbiter, despatched to Mars particularly to check the gasoline within the ambiance, has detected no methane.
“It’s a narrative with numerous plot twists,” stated 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 pc modeling initiatives that purpose to elucidate why the gasoline behaves surprisingly and is detected solely in Gale Crater. A NASA analysis group just lately shared an attention-grabbing proposal.
This picture is of a pattern of mock Martian “soil” after it was faraway from the Mars simulation chamber. The floor is sealed with a stable crust of salt. Alexander Pavlov and his workforce discovered {that a} seal shaped after a pattern spent three to 13 days below Mars-like circumstances, and provided that it had 5% to 10% perchlorate salt focus. The colour is lighter within the heart the place the pattern was scratched with a metallic decide. The sunshine colour signifies a drier soil beneath the highest layer, which absorbed moisture from the air as quickly because the pattern was faraway from the simulation chamber, turning brown. Credit score: NASA/Alexander Pavlov
Reporting in a March paper within the Journal of Geophysical Analysis: Planets, the group urged that methane — irrespective of the way it’s produced — could possibly be sealed below solidified salt that may type in Martian regolith, which is “soil” manufactured from damaged rock and dirt. When temperature rises throughout hotter seasons or occasions of day, weakening the seal, the methane may seep out.
Led by Alexander Pavlov, a planetary scientist at NASA’s Goddard Area Flight Middle in Greenbelt, Maryland, the researchers counsel the gasoline can also erupt in puffs when seals crack below the stress of, say, a rover the dimensions of a small SUV driving over it. The workforce’s speculation could assist clarify why methane is detected solely in Gale Crater, Pavlov stated, on condition that’s it’s 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 doesn’t have a methane-detecting instrument.)
It is a pattern of mock Martian regolith, which is “soil” manufactured from damaged rock and dirt. It’s one in every of 5 samples that scientists infused with various concentrations of a salt referred to as perchlorate that’s widespread on Mars. They uncovered every pattern to Mars-like circumstances within the Mars simulation chamber at NASA’s Goddard Area Flight Middle in Greenbelt, Maryland. The brittle clumps within the pattern above present {that a} seal of salt didn’t type on this pattern as a result of the focus of salt was too low. Credit score: NASA/Alexander Pavlov This picture is of one other pattern of mock Martian “soil” after it was faraway from the Mars simulation chamber. Credit score: NASA/Alexander Pavlov
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, may thrive in comparable circumstances on Mars.
The microbe-growing outcomes proved inconclusive, he stated, 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 gasoline and leaving the salt behind.
“We didn’t assume a lot of it for the time being,” Pavlov stated, however he remembered the soil crust in 2019, when SAM’s tunable laser spectrometer detected a methane burst nobody may clarify.
“That’s when it clicked in my thoughts,” Pavlov stated. And that’s when he and a workforce started testing the circumstances that might type and crack hardened salt seals.
Pavlov’s workforce examined 5 samples of permafrost infused with various concentrations of a salt referred to as perchlorate that’s widespread on Mars. (There’s seemingly no permafrost in Gale Crater right this moment, however the seals may have shaped way back when Gale was colder and icier.) The scientists uncovered every pattern to completely different temperatures and air stress inside a Mars simulation chamber at NASA Goddard.
(a) Mars Simulation Chamber, (b) a close-up of the pattern within the pattern holder within the chamber, (c) block diagram of your complete setup. The Chamber may attain temperatures under −100°C and pressures right down to as little as 0.1 mbar. — JGR planets
Periodically, Pavlov’s workforce injected neon, a methane analog, beneath the soil pattern and measured the gasoline stress under and above it. Larger stress beneath the pattern implied the gasoline was trapped. Finally, a seal shaped below Mars-like circumstances inside three to 13 days solely in samples with 5% to 10% perchlorate focus.
That’s a a lot greater salt focus than Curiosity has measured in Gale Crater. However regolith there’s wealthy in a distinct sort of salt minerals referred to as sulfates, which Pavlov’s workforce desires to check subsequent to see if they will additionally type seals.
Diagram of the facet profile of the pattern holder with a typical pattern inside.– JGR planets
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. Nonetheless, scientists say additionally they want extra constant methane measurements.
SAM sniffs for methane solely a number of occasions 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 have now to be very strategic after we resolve to do them,” stated 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 repeatedly from many areas throughout Mars, scientists say.
“Among the methane work should be left to future floor spacecraft which can be extra centered on answering these particular questions,” Vasavada stated.
Formation and Stability of Salty Soil Seals in Mars-Like Situations. Implications for Methane Variability on Mars, JGR planets (open entry)
Extra Concerning the Mission
Curiosity was constructed by JPL, which is managed by Caltech in Pasadena, California. JPL leads the mission on behalf of NASA’s Science Mission Directorate in Washington.
For extra about Curiosity, go to: https://mars.nasa.gov/msl
Astrobiology
