Where does the methane from Mars come from? Not the wind | Space

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Mars is a rocky world and some scientists have speculated that erosion caused by the wind caused the rocks of Mars to produce methane. But a new study from the University of Newcastle refutes that. Image via NASA / JPL-Caltech / Phys.org.

What produces methane on Mars? This is a question that scientists have been trying to answer for some time now. There are various possibilities, both geological and biological, but their reduction has been a challenge. Would it really be a sign of … life? Now, a new study has shown that at least one of the geological scenarios was very unlikely: wind erosion of rocks.

Researchers at the University of Newcastle, UK, published their peer-reviewed findings in Scientific reports June 3, 2019 and a new press release was published on August 12, 2019. Abstract article excerpt:

Seasonal changes in background levels of methane and methane peaks have been detected in situ at one meter from the Martian surface, and larger methane plumes detected by ground-based remote sensing, but their origin has not yet been adequately explained. The proposed sources of methane include UV irradiation of organic matter derived from meteorites, hydrothermal reactions with olivine, organic decomposition by the impact of meteoroids, the release of gas hydrates , biological production or the liberation of methane from fluid inclusions in the basalt during wind erosion. Here, we quantify for the first time the potential importance of wind abrasion as a mechanism for releasing methane trapped in rocks by coupling estimates of surface wind abrasion with methane variety of Martian meteorites, similar terrestrial basalts and similar terrestrial systems. sedimentary rocks. We demonstrate that it is very unlikely that abrasion of basalt by current Martian wind erosion rates will produce detectable changes in methane concentrations in the atmosphere. We further show that, although the methane production potential resulting from the wind abrasion of some sedimentary rocks is greater, to produce the magnitude of the methane concentrations analyzed by the Curiosity robot, they should contain methane in concentrations similar to those reserved for biogenes / economics. thermogenic deposits on the Earth. Therefore, we suggest that wind abrasion is an unlikely origin of methane detected in the Martian atmosphere and that other sources of methane are needed.

History of the main measurements of methane on Mars from 1999 to 2018. Image via ESA.

One of the most recent theories has been that wind erosion of rocks could produce the methane detected in the lower atmosphere. The team's findings showed that it could not produce methane in the quantities observed, according to Jon Telling, a geochemist at Newcastle University:

The questions are: where does this methane come from and the source is organic? This is a huge question and to get the answer, we must first dismiss many other factors.

We realized that a potential source of methane that people had not really studied in detail before was wind erosion, releasing gas trapped in the rocks. High resolution images taken in orbit over the past decade have shown that winds on Mars can result in much higher local rates of sand displacement, and thus potential rates of sand erosion, larger than expected.

In fact, in some cases, the rate of erosion is comparable to that of the cold, arid sand dune fields of the Earth.

Using available data, we estimated erosion rates on the surface of Mars and its importance for methane release.

And given all of that, we found that it was very unlikely that it was the source.

The important thing is that it reinforces the argument that methane must come from a different source. Whether organic or not, we still do not know.

ESA's Trace Gas Orbiter artist concept, part of the ExoMars mission, analyzing the Martian atmosphere. Image via ESA / ATG MediaLab.

Observations by both the orbiting spacecraft and the Curiosity rover, as well as by telescopes on Earth, have shown that methane levels in the Martian atmosphere appear to be seasonal, culminating in the summer and continuing into the future. erasing again in winter. We do not know yet why, but it indicates a regular process, whether geological or biological. Curiously, ESA's Trace Gas Orbiter (TGO) has not yet detected methane, although this is one of its main objectives. But this may simply be due to the seasonal nature of methane, or the fact that TGO concentrates its observations on the upper layers of the atmosphere and that most other methane detections have been made closer to the ground.

Most scientists now believe that methane comes from the subsoil, perhaps in the form of ice clathrates that melt in the summer and release methane, or perhaps a biological source that reacts to warmer temperatures. Even if methane is linked to clathrates, its real origin could still be geological or biological (old life). Or it can be produced by warm groundwater interacting with olivine in the rocks. If this were the case, this would indicate that residual geological activity remains below the surface of Mars and that this could be a habitable environment for microorganisms, even if they did not actually produce methane. According to recent studies, other causes, such as meteorites or comets, probably would not produce enough gas to match the observations.

Last April, a new report revealed that the Curiosity mobile and the satellite in orbit around Mars Express had detected a methane spike at the same time, for the first time, in 2013. And last June, Curiosity detected its largest measure to date. of methane up to now. Why are there spikes in methane emissions while the gas disappears virtually after? Emmal Safi, a postdoctoral researcher at Newcastle University, said many things were not known:

It's always an open question. Our paper is just a small part of a much bigger story.

Ultimately, we try to determine whether it is possible for life to exist on planets other than ours, either living now, or perhaps in the past, which are now preserved in the form of fossil or chemical signatures.

Illustration illustrating which processes could create and destroy methane on Mars. The methane probably comes from the surface and is released into the atmosphere by cracks below the surface. Image via ESA.

The idea that Mars methane could come from life is obviously an interesting idea, because most of the methane on Earth is produced by living organisms. But non-biological explanations will have to be eliminated first. Newcastle University research shows that at least one of the possible geological explanations for methane is unlikely, but scientists still have a lot of work to do to determine exactly is producing it.

Conclusion: this new study seems to eliminate a possible source of methane from Mars: wind erosion of rocks on the surface. This reinforces the probability that methane will come from the subsoil.

Source: Wind Abrasion of Rocks as a Methane Production Mechanism in the Martian Atmosphere

Via Newcastle University