With Mars methane thriller unsolved, Curiosity serves scientists a brand new one: Oxygen

NASA/Goddard Area Flight Heart

This can be a sundown on the Viking Lander 1 website, 1976. Credit score: NASA/JPL

For the primary time within the historical past of area exploration, scientists have measured the seasonal modifications within the gases that fill the air immediately above the floor of Gale Crater on Mars. Because of this, they seen one thing baffling: oxygen, the fuel many Earth creatures use to breathe, behaves in a manner that thus far scientists can’t clarify by means of any recognized chemical processes.

Over the course of three Mars years (or practically six Earth years) an instrument within the Pattern Evaluation at Mars (SAM) moveable chemistry lab contained in the stomach of NASA’s Curiosity rover inhaled the air of Gale Crater and analyzed its composition. The outcomes SAM spit out confirmed the make-up of the Martian ambiance on the floor: 95% by quantity of carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), zero.16% molecular oxygen (O2), and zero.06% carbon monoxide (CO). In addition they revealed how the molecules within the Martian air combine and flow into with the modifications in air strain all year long. These modifications are triggered when CO2 fuel freezes over the poles within the winter, thereby reducing the air strain throughout the planet following redistribution of air to keep up strain equilibrium. When CO2 evaporates within the spring and summer season and mixes throughout Mars, it raises the air strain.

Inside this setting, scientists discovered that nitrogen and argon observe a predictable seasonal sample, waxing and waning in focus in Gale Crater all year long relative to how a lot CO2 is within the air. They anticipated oxygen to do the identical. But it surely didn’t. As an alternative, the quantity of the fuel within the air rose all through spring and summer season by as a lot as 30%, after which dropped again to ranges predicted by recognized chemistry in fall. This sample repeated every spring, although the quantity of oxygen added to the ambiance assorted, implying that one thing was producing it after which taking it away.

“The primary time we noticed that, it was simply thoughts boggling,” mentioned Sushil Atreya, professor of local weather and area sciences on the College of Michigan in Ann Arbor. Atreya is a co-author of a paper on this matter revealed on November 12 within the Journal of Geophysical Analysis: Planets.

As quickly as scientists found the oxygen enigma, Mars consultants set to work attempting to elucidate it. They first double- and triple-checked the accuracy of the SAM instrument they used to measure the gases: the Quadrupole Mass Spectrometer. The instrument was positive. They thought of the likelihood that CO2 or water (H2O) molecules may have launched oxygen once they broke aside within the ambiance, resulting in the short-lived rise. However it might take 5 instances extra water above Mars to provide the additional oxygen, and CO2 breaks up too slowly to generate it over such a short while. What concerning the oxygen lower? Might photo voltaic radiation have damaged up oxygen molecules into two atoms that blew away into area? No, scientists concluded, since it might take at the least 10 years for the oxygen to vanish by means of this course of.

“We’re struggling to elucidate this,” mentioned Melissa Coach, a planetary scientist at NASA’s Goddard Area Flight Heart in Greenbelt, Maryland who led this analysis. “The truth that the oxygen conduct isn’t completely repeatable each season makes us suppose that it’s not a problem that has to do with atmospheric dynamics. It needs to be some chemical supply and sink that we are able to’t but account for.”

To scientists who examine Mars, the oxygen story is curiously much like that of methane. Methane is consistently within the air inside Gale Crater in such small portions (zero.00000004% on common) that it’s barely discernable even by essentially the most delicate devices on Mars. Nonetheless, it’s been measured by SAM’s Tunable Laser Spectrometer. The instrument revealed that whereas methane rises and falls seasonally, it will increase in abundance by about 60% in summer season months for inexplicable causes. (The truth is, methane additionally spikes randomly and dramatically. Scientists are attempting to determine why.)

With the brand new oxygen findings in hand, Coach’s group is questioning if chemistry much like what’s driving methane’s pure differences due to the season can also drive oxygen’s. At the very least often, the 2 gases seem to fluctuate in tandem.

“We’re starting to see this tantalizing correlation between methane and oxygen for an excellent a part of the Mars yr,” Atreya mentioned. “I feel there’s one thing to it. I simply don’t have the solutions but. No person does.”

Oxygen and methane could be produced each biologically (from microbes, as an illustration) and abiotically (from chemistry associated to water and rocks). Scientists are contemplating all choices, though they don’t have any convincing proof of organic exercise on Mars. Curiosity doesn’t have devices that may definitively say whether or not the supply of the methane or oxygen on Mars is organic or geological. Scientists count on that non-biological explanations are extra possible and are working diligently to totally perceive them.

Coach’s group thought of Martian soil as a supply of the additional springtime oxygen. In spite of everything, it’s recognized to be wealthy within the component, within the type of compounds akin to hydrogen peroxide and perchlorates. One experiment on the Viking landers confirmed a long time in the past that warmth and humidity may launch oxygen from Martian soil. However that experiment befell in situations fairly totally different from the Martian spring setting, and it doesn’t clarify the oxygen drop, amongst different issues. Different doable explanations additionally don’t fairly add up for now. For instance, high-energy radiation of the soil may produce further O2 within the air, however it might take 1,000,000 years to build up sufficient oxygen within the soil to account for the enhance measured in just one spring, the researchers report of their paper.

“Now we have not been capable of provide you with one course of but that produces the quantity of oxygen we want, however we expect it needs to be one thing within the floor soil that modifications seasonally as a result of there aren’t sufficient obtainable oxygen atoms within the ambiance to create the conduct we see,” mentioned Timothy McConnochie, assistant analysis scientist on the College of Maryland in Faculty Park and one other co-author of the paper.

The one earlier spacecraft with devices able to measuring the composition of the Martian air close to the bottom have been NASA’s twin Viking landers, which arrived on the planet in 1976. The Viking experiments lined just a few Martian days, although, so that they couldn’t reveal seasonal patterns of the totally different gases. The brand new SAM measurements are the primary to take action. The SAM group will proceed to measure atmospheric gases so scientists can collect extra detailed information all through every season. Within the meantime, Coach and her group hope that different Mars consultants will work to resolve the oxygen thriller.

“That is the primary time the place we’re seeing this attention-grabbing conduct over a number of years. We don’t completely perceive it,” Coach mentioned. “For me, that is an open name to all of the sensible folks on the market who’re on this: See what you may provide you with.”

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From EurekAlert!

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