NASA's Robotics Rover continues to make discoveries that challenge our understanding of the environment from Mars. The latest weird puzzles that scientists are taxing are the variation in oxygen levels on the planet's surface, as revealed by the portable laboratory for chemistry of ioscience, Mars Specimen Analysis (SAM).
In his journey around the Gale Crater, Curiousness discovered that Mars's atmosphere has a composition of 95% by volume of carbon dioxide (CO2), 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0, 16% molecular oxygen (O2) and 0.06% carbon monoxide (CO). Nitrogen and argon levels follow a predictable seasonal pattern, varying in amount of carbon dioxide. Oxygen levels, however, did not match expected patterns, rising by as much as 30% during spring and summer.
Scientists have lowered oxygen levels. "The first time we saw it, it was just thinking," Sushil Atrea, a professor of climate and space science at the University of Michigan, said in a statement.
Scientists have tried different hypotheses to explain the variation in oxygen. They checked whether the SAM was functioning properly and examined whether carbon dioxide molecules could decompose into the atmosphere to produce oxygen, but no approach yielded results.
"We are struggling to explain this," said Melissa Trainer, a planetary scientist at GSD Goddard Space Flight Center and research leader. "The fact that oxygen behavior is not perfectly repeatable every season has made us think that this is not a problem related to atmospheric dynamics. It has to be some chemical source and sink that we still can't count on. "
One possibility is that oxygen levels are linked to another Marian puzzle: Fluctuating methane levels on the planet. As with the expected seasonal variations in methane levels, curiosity discovered spikes of methane up to 60% in some periods. Scientists cannot yet explain this finding, but may find a link between methane and oxygen levels: It seems that the two gases differ at certain times.
"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 ".
Although both oxygen and methane can be produced biologically, their presence does not necessarily mean life on the planet. They can also be produced chemically, with water and rock. Curiosity can only detect the levels of gases, not their origin, so the source of this mystery remains unknown for now.
The research is published in the journal Geophysical Research: Planets.