The mystery of Mars methane has recently re-emerged in the news, starting with a study announced earlier this month, stating that it is likely not caused by the wind erosion of rocks , Another recent study has refined estimates of methane gas in the Martian atmosphere and showed how concentrations change during a single Mars day.
The peer-reviewed study conducted by John Moores at York University in Canada was published in Geophysical Research Letters on August 20, 201
This new study redefines our understanding How the methane concentration in the Martian atmosphere changes over time helps us to solve the bigger mystery of what the source could be.
The source of Mars methane is the true mystery. Where does the methane come from? Methane gas can be linked to microbial life on Earth. The idea of living microbes on Mars has long fascinated astronomers. Several ships sent to Mars have searched for signs of life, but so far no signs of life have been discovered. In 2018, scientists announced that seasonal variations in Mars methane could be related to microorganisms. Or the variations in methane could be generated by geological means. It's an interesting puzzle!
The new research results are based on data from the Trace Gas Orbiter (TGO) and the Curiosity Rover. The curiosity in the Gale Crater has seen methane outbreaks at different times in recent years, and the analysis shows that it peaks in the summer and disappears in the winter.
Now, the new study shows that methane levels also change over the course of a Mars day. Moores notes:
This recent work suggests that the methane concentration changes during the day. For the first time, we were able to calculate a single figure for the methane seep rate in the Gale Crater on Mars, which averages 2.8 kg [.7 gallons] per Mars day.
From the publication:
The ExoMars trace gas orbiter and the Curiosity Rover have recorded varying amounts of methane in the Martian atmosphere. The trace gas orbiter measured very little methane (<50 volumes per trillion) above 5 km [3 miles] in the sunlit atmosphere, while curiosity at night measured much more (410 volumes per trillion) near the surface. In this article, we describe a scaffold that explains both measurements by suggesting that a small amount of methane constantly seeps out of the ground. During the day, this small amount of methane is rapidly mixed and diluted by vigorous convection, resulting in low total atmospheric values. During the night, convection decreases, causing methane to accumulate near the surface. At dawn, convection increases and the near-surface methane is mixed and diluted with much more atmosphere. With this model and the methane concentrations from both approaches, we can for the first time calculate a single figure for the methane seep rate in the Gale Crater equivalent to 2.8 kg per Mars day. Future spacecraft that measure methane near the surface of Mars could determine how much methane seeps out of the ground at different locations, providing insights into the processes in which this methane builds up underground.
The results should provide more evidence of the source of methane, which could be biological or non-biological, at least for methane detected in the Gale Crater environment While Curiosity noted the increase in methane levels, this was not the case for TGO, as Moores explained:
We were able to remedy these differences by demonstrating that the methane concentrations in the atmosphere Much lower during the day and considerably higher at night near the planet's surface as heat transfer decreases.
TGO has focused on the analysis of the upper atmospheric levels, which may explain why the methane explosions near the ground have been overlooked or because the methane peaks are seasonal.
The seasonal and daily fluctuations could be compatible with biology, as with microbes. As a source of methane, there are other plausible geological explanations. According to Penny King of the Australia National University (ANU):
Some microbes on Earth can survive deep underground without oxygen and release methane as part of their waste. The methane on Mars has other possible sources, such. As water-rock reactions or the decomposition of methane-containing substances.
While the genesis of methane is still unknown, most scientists believe that it comes from underground and is regularly released by cracks. This, in turn, could be compatible with either biology or geology. The geological sources could be the water-rock interactions or icy methane lathrates that contain methane and release it at warmer temperatures. If it were rocks and water, it would still be an exciting finding, suggesting that there is still liquid underground and at least some active geological processes are still present. This alone could provide microbes with a nice habitat, even if they do not produce the methane themselves. Whatever the explanation for the methane, it will give a fascinating insight into the current geological or biological processes on the red planet.
Conclusion: A new study shows how the concentration of methane in the Martian atmosphere changes not only seasonally, but daily. ExoMars trace gas orbiter and curiosity observations