NASA's Curiosity Rover has been trundling around on Mars since August 2012, and in that time it's made a bunch of discoveries. Yet, there always seems to be more stuff to find. And this time, it's made a discovery that's baffling the scientists watching closely.
According to NASA, Curiosity has uncovered an unexpected seasonal variation of the oxygen on Mars. Apparently it goes up and down in levels in a way they can't account for.
Images courtesy: NASA
You see, Curiosity determined a while ago that Mars has a thin atmosphere, a lot of which is carbon dioxide. In the winter, that CO2 freezes over the poles, lowering air pressure across the planet. Then, in the summer, it thaws once more, with the released CO2 lowering the atmospheric pressure again. A similar process happens with the smaller amounts of nitrogen and argon in the air as well.?
However, Curiosity found a while ago that methane found in the Martian atmosphere instead spikes at times at odds with this seasonal cycle. And now it's found that oxygen on the Red Planet behaves the same way too.
Apparently oxygen on Mars has shown "significant seasonal and interannual variability, suggesting an unknown atmospheric or surface process at work," the authors wrote in a paper. Which means, they say, that there's a chemical process at work they don't know about yet.
Mars is tilted on its axis, like Earth. That means, the North and South hemispheres are closer to the Sun at different times of the year, making a summer and winter season. That's why the CO2 freeze and thaw happens, as does the Nitrogen and other trace gases.?
That's why it's so strange oxygen doesn't follow this trend. There's much more oxygen in the Martian northern hemisphere during its "summer", and a lot less during the northern hemisphere's winter.
"The fact that the oxygen behavior isn't perfectly repeatable every season makes us think that it's not an issue that has to do with atmospheric dynamics. It has to be some chemical source and sink that we can't yet account for," the study's first author Melissa Trainer, a planetary scientist at NASA's Goddard Space Flight Center, said.
And right now, there's no saying what that means for Mars.