The atmospheric gases of Mars certainly give us a lot of mystery. First, there was this business with the disappearing, re-emerging methane. Oxygen levels are now observed to rise and fall above the Galle crater, in quantities that simply do not respond to any known chemical processes.
The data comes from Curiosity, a rover that makes its slow and methodical journey through the crater floor and up at the foot of Mount Sharp.
The robot not only looks down at the rocks beneath its protectors; Curiosity also takes into account the readings of the Martian atmosphere to measure seasonal atmospheric changes. For three years on Mars (these are six Earth years) and scientists examining the measurements have noticed that the oxygen in the atmosphere of the planet is not fully behaving as expected.
Not really all that much oxygen on Mars. Most of its thin atmosphere (95% by volume) is carbon dioxide or CO2. The rest consists of 2.6 percent molecular nitrogen (N2), 1
(The Earth's atmosphere, by contrast, is mostly nitrogen, with 78.09 volume percent and 20.95 percent oxygen.)
At Mars, atmospheric pressure changes throughout the year. In the winter hemisphere, CO2 freezes above the pole, causing the pressure in the hemisphere to drop. This results in the redistribution of gases between hemispheres and hemispheres to equalize atmospheric pressure across the globe.
In the spring, when the polar caps melt and release CO2, the opposite effect occurs: initially the pressure rises in this hemisphere, then equalizes as the gases redistribute to the winter hemisphere.
Thus, the fluctuations of the other gas are predictable in proportion to the CO2 levels. Or at least they should be. In the case of nitrogen and argon, these gases behaved more or less exactly as expected. But oxygen?
In the spring and summer, oxygen increased by about 30 percent, again in the fall to normal levels. This happens every year, but as the amount of oxygen increases varies from year to year, it seems that something adds oxygen and then takes it back again.
No known process This can lead to this result.
The obvious question for such an odd measurement was whether there could be anything wrong with the quadrupole mass spectrometer instrument or software. Several checks saw that everything was working fine.
Alternatively, oxygen may be produced from water or carbon dioxide in some way to decompose into the atmosphere. This was also quickly ruled out – there is not enough water in the Martian atmosphere and CO2 is decomposed too slowly to absorb the observed fluctuations.
Martian soil contains a lot of oxygen. But the conditions required for his release have not been met – and that does not explain where he disappears every year. The process by which solar radiation splits oxygen and dissipates into space is also too slow.
"We're struggling to explain this," says planetary scientist Melissa Coach of the NASA Goddard Space Flight Center.
"The fact that the behavior of oxygen is not completely repeatable every season makes us think that this is not a problem related to the dynamics of the atmosphere. It must be some kind of chemical source and sink that we still cannot account for. "
But there is one clue. Methane. It also increases dramatically during the summer months of Mars, increasing by up to 60 percent. Sometimes the levels of methane and oxygen even seem to rise in tandem. which causes methane fluctuations also causes oxygen fluctuations.
What could be is still a huge issue Both gases can be produced through organic processes – that is, life – both can be produced through geological processes
So far we have no evidence that Mars is alive from, but neither can be governed by. as a cause. (Mars 2020 will search for fossils, so maybe we'll find out soon.)
However, the team thinks it's much more likely to be geological. [19659003"Wehavenotbeenabletocomeupwithaprocessthatstillproducesthenecessaryamountofoxygen"saidastronomerTimMcConchyoftheUniversityofMaryland
"But we think there must be something in the soil surface that changes seasonally because there is not enough oxygen atoms in the atmosphere to create the behavior we see."
So … any ideas?
The study was published in Journal of Geophysical Research: Planets .