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With unsolved mystery on Mars methane, Curiosity serves scientists new: Oxygen


With unsolved mystery on Mars methane, Curiosity serves scientists new: Oxygen

Credits: Melissa Coach / Dan Gallagher / NASA Goddard

For the first time in the history of space exploration, scientists have measured the seasonal changes in air-filling gases directly above the surface of King Gale on Mars. As a result, they have noticed something puzzling: oxygen, the gas that many creatures on Earth use to breathe, behaves in a way that scientists cannot yet explain through known chemical processes.

For three years on Mars (or nearly six years on Earth), an instrument in the Mars Chemical Transfer Laboratory (SAM) in NASA's NASA Rover spacecraft inhaled Gale Crater's air and analyzed its composition. The results spat by SAM confirmed the make-up of the Martian atmosphere on the surface: 95% by volume of carbon dioxide (CO)2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0.16% molecular oxygen (OH)2), and 0.06% carbon monoxide (CO). They also discovered how the molecules in the Martian air mix and circulate with changes in air pressure throughout the year. These changes are caused when CO2 freezes gas through the columns in winter, thereby reducing air pressure across the planet after redistributing air to maintain pressure balance. When with2 evaporates in spring and summer and mixes across Mars, increasing air pressure.

Within this environment, scientists have found that nitrogen and argon follow a predictable seasonal pattern, targeting and decreasing the Gale Crater's concentration throughout the year relative to how much CO2 is in the air. They were expecting oxygen to do the same. But that failed. Instead, the amount of gas in the air increased by as much as 30% during the spring and summer, and then dropped back to levels predicted by the famous chemistry in the fall. This pattern was repeated every spring, though the amount of oxygen added to the atmosphere varied, meaning it produced something and then took it away.

"The first time we saw it, it was just a push in the mind," said Sushil Atrea, a professor of climate and space science at the University of Michigan in Ann Arbor. Atrea is a co-author of a paper on this topic published on November 12 at Crash for Geophysical Research: Planets.

With unsolved mystery on Mars methane, curiosity serves scientists new - Oxygen

Sunset on Viking Lander page 1, 1976. Credit: NASA / CPL

Once scientists discovered the oxygen ecg, Mars experts tried to work out trying to explain it. They first double and triple checked the accuracy of the SAM instrument they used to measure the gases: Quadrupole Mass Spectrometer. The instrument was fine. They considered the possibility with the CO2 or water (N.2A) The molecules could release oxygen when decomposed into the atmosphere, leading to short-lived elevation. But it will take five times as much water over Mars to produce extra oxygen, and CO2 breaks up too slowly to generate in such a short time. What about oxygen reduction? Can solar radiation break down the oxygen molecules into two atoms blown into space? No, the scientists concluded, because it will take at least 10 years for oxygen to disappear through this process.

"We are struggling to explain this," said Melissa Trainer, a planetary scientist at NASA's Goddard Space Flight in Greenbelt, Maryland, who led the research. "The fact that oxygen behavior is not perfectly repetitive every season made us think that this is not a problem to do with atmospheric dynamics. It must be some chemical source and sink that we still can't count on. "

For scientists studying Mars, the story of oxygen is curiously similar to that of methane. Methane is constantly in the air inside King Gale in such small quantities (on average 0.00000004%) that it is barely detectable by even the most sensitive instruments on Mars. However, it is measured with the SAM's tunable laser spectrometer. The instrument found that as methane grows and falls seasonally, it increases in abundance by about 60% in the summer months for unexplained reasons. (In fact, methane also spreads randomly and dramatically. Scientists are trying to find out why.)

With the new oxygen breakthroughs, the Turner team wonders whether chemistry similar to the natural seasonal variations of methane can also cause oxygen. At least occasionally, the two gases appear to be moving in tandem.

With unsolved mystery on Mars methane, Curiosity serves scientists new: Oxygen

Credit: Melissa Coach / Dan Gallagher / NASA Goddard

"We are starting to see this astonishing correlation between methane and oxygen for a good part of the year on Mars," Atrea said. "I think there is something to it. I don't have the answers yet. Nobody does that".

Oxygen and methane can be produced both biologically (from microbes, for example) and abiotic (from water and rock chemistry). Scientists are considering all options, although they have no conclusive evidence of biological activity on Mars. Curiosity has no instruments that can definitively say whether the source of methane or oxygen on Mars is biological or geological. Scientists expect that non-biological explanations are more likely and worth working to fully understand.

The team of trainers saw Mars soil as a source of extra spring oxygen. After all, it is known to be rich in the element in the form of compounds such as hydrogen peroxide and perchlorate. A Viking earthquake experiment showed decades ago that heat and humidity can release oxygen from the sea. But that experiment was conducted in conditions completely different from the spring environment of Mars and does not explain the decline in oxygen, among other problems. Other possible explanations are also not being added now. For example, high-energy soil radiation can produce additional O2 in the air, but it will take millions of years to accumulate enough oxygen in the soil to take into account the strength measured in just one spring, researchers say in their paper.

"We still haven't been able to find a process that produces the amount of oxygen we need, but we think it has to be something in the surface soil that changes seasonally because there are not enough oxygen atoms in the atmosphere. create the behavior we see. "Said Timothy McConaughey, an assistant research scientist at the University of Maryland College Park and another co-author of the paper.

With unsolved mystery on Mars methane, Curiosity serves scientists new: Oxygen

Credit: Melissa Coach / Dan Gallagher / NASA Goddard

The only previous spacecraft with instruments capable of measuring the composition of Martian air near Earth were NASA's Viking twins, which arrived on the planet in 1976. The Vikings' experiments covered only a few Martian days, however, so they could not detect seasonal patterns in the different gases. The new SAM measurements are the first to do so. The SAM team will continue to measure atmospheric emissions so that scientists can collect more detailed data during each season. Meanwhile, Trainer and her team hope other Mars experts will work on solving the oxygen mystery.

"This is the first time we have seen this interesting behavior over many years. We do not fully understand it," said Turner. "For me, this is an open call to all the smart people who are interested in this: Look what you can come up with."

Step closer to solving the methane mystery of Mars

More info:
Melissa G. Coaching etc. Seasonal variations in atmospheric composition as measured in Kate Galle, Mars, Crash for Geophysical Research: Planets (2019). DOI: 10.1029 / 2019JE006175

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NASA Goddard Space Flight Center

With unsolved mystery on Mars methane, curiosity serves scientists new: Oxygen (2019, November 12)
Retrieved November 12, 2019

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