Nasa has noticed unexpected and unexplained changes in the oxygen of Mars.
The discovery comes after the space agency used the Curiosity rover to measure seasonal changes in the gas that fills the air above Mars' Galle crater for the first time.
But the data sent back from the planet left the scientists who received it buried. They say that there is no known explanation for the planet's unusual oxygen fluctuations.
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"The first time we saw it was just mind-blowing," says Sushil Atreia, professor of climate and Space Science at the University of Michigan, Ann Arbor
Comes as researchers continue to fight the mystery of methane on the red planet.As already revealed for oxygen, the amount of gas rises and sinks in a way that seems random and for which scientists have no reason.
During the study using an analysis tool in Mars air for three Martian years or just under six Earth years, a scientist finds that gases such as nitrogen and argon are kept predictably throughout the year. The proportion of gas increases and decreases with respect to the amount of carbon dioxide, which makes up 95% of the Martian air.
They believed that oxygen would have the same changes. But they were shocked to find that it had actually increased in the spring and summer, with varying amounts of oxygen in the atmosphere, suggesting that it was being produced and then removed from the air.
Researchers were so shocked by the findings that their first course of action was to check the accuracy of the tool used to find the data, but found it to work fine. Other possible explanations based on what we know about the Martian atmosphere have also been considered but rejected.
"We're struggling to explain it," said Melissa Trainer, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who led the study. "The fact that oxygen behavior does not repeat itself perfectly every season makes us think that this is not a problem with atmospheric dynamics. It must be some kind of chemical source and sink that we cannot yet account for."  The similarities between the mystery of Martian methane and Martian oxygen may be more than a coincidence, scientists suggest. It is possible that they both have the same, as yet, unidentified cause.
"We are beginning to see this painful link between methane and oxygen for much of the year of Mars," Atreia said. "I think there is something about it. I just don't have the answers yet. No one does.
Scientists now hope to continue to measure the atmosphere to try and solve the mystery of oxygen.
" the first time we see this interesting behavior in a few years. We don't fully understand it, Coach said.
"To me, this is an open call to all smart people who are interested in this: See what you can think of. "
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