Something is producing an excess of oxygen on Mars and scientists are baffled

First methane and now oxygen on Mars that can represent a biofilm behave in a strange way.

Something is producing an excess of oxygen on Mars and scientists are baffled
Clouds captured by the Curiosity rover on May 17, 2019, on its 2,410 day on Mars.

A team of scientists has managed to measure the seasonal changes of the gases that permeate the air just above the Gale crater, on Mars, the place that the Curiosity rover has been exploring since August 2012.

During the analysis, the researchers found something disconcerting: oxygen on Mars, the gas that most terrestrial creatures use to breathe, is behaving in a way that is impossible to explain through any known chemical process.

During the last three Martian years (equivalent to almost six Earth years) the SAM ( Sample Analysis at Mars ) portable chemistry laboratory has been “inhaling” the air of the Gale crater and analyzing its composition.

 And the results of the Curiosity instrument have allowed us to get an accurate idea of ​​the composition of the Martian atmosphere on the surface of the crater: 95% carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9 % argon (Ar), 0.6% molecular oxygen (O2) and 0.6% carbon dioxide (CO). 

The data also revealed how the molecules of these gases mix and circulate in the air throughout the year.

Seasonal changes

On Mars, seasonal changes occur when CO2 freezes over the poles in winter, thus lowering air pressure across the planet and causing its redistribution. On the contrary, when CO2 evaporates during spring and summer, it mixes with the air and its pressure increases.

In this environment, the researchers discovered that nitrogen and argon follow a predictable seasonal pattern, increasing and decreasing their concentration in the Gale crater during the various seasons and depending on the amount of CO2 present in each moment. But the behavior of oxygen was completely different.

Seasonal changes

On Mars, seasonal changes occur when CO2 freezes over the poles in winter, thus lowering air pressure across the planet and causing its redistribution. On the contrary, when CO2 evaporates during spring and summer, it mixes with the air and its pressure increases.

In this environment, the researchers discovered that nitrogen and argon follow a predictable seasonal pattern, increasing and decreasing their concentration in the Gale crater during the various seasons and depending on the amount of CO2 present in each moment. But the behavior of oxygen was completely different.

Seasonal changes

On Mars, seasonal changes occur when CO2 freezes over the poles in winter, thus lowering air pressure across the planet and causing its redistribution. On the contrary, when CO2 evaporates during spring and summer, it mixes with the air and its pressure increases.

In this environment, the researchers discovered that nitrogen and argon follow a predictable seasonal pattern, increasing and decreasing their concentration in the Gale crater during the various seasons and depending on the amount of CO2 present in each moment. But the behavior of oxygen was completely different.

Seasonal changes

On Mars, seasonal changes occur when CO2 freezes over the poles in winter, thus lowering air pressure across the planet and causing its redistribution. On the contrary, when CO2 evaporates during spring and summer, it mixes with the air and its pressure increases.

In this environment, the researchers discovered that nitrogen and argon follow a predictable seasonal pattern, increasing and decreasing their concentration in the Gale crater during the various seasons and depending on the amount of CO2 present in each moment. But the behavior of oxygen was completely different.

Seasonal changes

On Mars, seasonal changes occur when CO2 freezes over the poles in winter, thus lowering air pressure across the planet and causing its redistribution. 

On the contrary, when CO2 evaporates during spring and summer, it mixes with the air and its pressure increases.

In this environment, the researchers discovered that nitrogen and argon follow a predictable seasonal pattern, increasing and decreasing their concentration in the Gale crater during the various seasons and depending on the amount of CO2 present in each moment. 

But the behavior of oxygen was completely different.

Something is producing an excess of oxygen on Mars and scientists are baffled

In principle, the researchers expected oxygen to do the same as nitrogen and argon, but they found something they did not expect at all: during the spring and summer, the amount of oxygen increased by up to 30%, to return then fall, in autumn, to the levels predicted by known chemistry. The pattern was repeated every spring, although from year to year the amount of oxygen added to the atmosphere varied. The only possible conclusion is that “something” is producing that extra oxygen during the warm months.

“The first time we saw this was amazing,” says Sushil Atreya of the University of Michigan and co-author of the study published in the Journal of Geophysical Research: Planets.

A chemical source

As soon as the scientists discovered the enigma of oxygen, experts got to work to try to explain it. 

The first thing they did was verify, in duplicate and triplicate, the accuracy of the SAM instrument, which was the one that measured the gases. 

But everything worked perfectly. Then, they considered the possibility that the molecules of CO2 or water (H2O) could be responsible for the release of excess oxygen, as it decomposes in the atmosphere. 

But it turns out that it would take an amount of water five times higher than what is in the Martian atmosphere to produce the amount of oxygen detected and, in addition, CO2 decomposes too slowly to produce all the oxygen detected these years.

Something is producing an excess of oxygen on Mars and scientists are baffled
Photograph taken while the rover climbs Mount Sharp, about 5 meters high, in the center of Gale crater, the “neighborhood” Curiosity is currently examining for possible life.

But if the summer increase in oxygen is a mystery, neither is its winter decrease clear. 

To try to explain it, the researchers considered the possibility that solar radiation was breaking down, in the cold months, atmospheric oxygen molecules, which would be lost in space. 

But they soon concluded that this process would take at least 10 years to reduce the oxygen level, and the data clearly showed that their level decreased dramatically once a year.

In the words of Melissa Trainer, a planetary scientist at NASA’s Goddard Space Flight Center, and director of the research, “we are struggling to explain this. 

In addition, the fact that oxygen behavior is not repeated exactly in each season makes us think that we are not facing a problem that has to do with atmospheric dynamics. 

There has to be a chemical source, and a sink, which we still can’t explain.

The methane mystery

For scientists what is happening with oxygen is something similar to what happens with methane, whose amount in the Gale crater also increases up to 60% during the summer for reasons that have not been explained. Will both phenomena be related?

Something is producing an excess of oxygen on Mars and scientists are baffled

With the new oxygen data in hand, Trainer and his team now wonder if chemistry similar to the one that drives seasonal methane variations could also boost oxygen. And, at least on some occasions, fluctuations of both gases occur at the same time.

“We are beginning to see this tempting correlation between methane and oxygen during a good part of the Martian year. And I think that means something. But we don’t have the answers yet. No one has them, ”explains Atreya.

On the ground surface

Oxygen and methane can have both a biological origin (from microbes, for example), and abiotic (from the chemistry of water and rocks). The researchers are considering both options, although at the moment there is no more evidence that there is a biological activity on Mars and the Curiosity, to top it off, does not have the necessary instruments to elucidate the issue.

This is explained by Timothy McConnochie of the University of Maryland and another of the study’s authors: “We have not yet been able to find a process that produces the amount of oxygen we need, but we believe it has to be something on the ground surface. Something that changes seasonally, because there are not enough oxygen atoms in the atmosphere to create the behavior we are seeing ».

“This is the first time we have observed this oxygen behavior for several years, and we do not fully understand it. For me, this is an open call to all intelligent people who are interested in the subject: to see what they can think of, ”concludes Trainer.

Source: NASA

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