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Is there extraterrestrial life in space?
The greenhouse gas methane could help in the search
Photo: Bhavik Jagani/EyeEm/Getty Images
Are we alone in the Universe?
Or do alien beings live on alien planets?
A research team from the USA has described a way that could facilitate the search for extraterrestrial life in space: Humanity should therefore look out for methane.
The study, by researchers from the University of California Santa Cruz, was scheduled to appear March 28 in the journal Proceedings of the National Academy of Sciences.
Only a press release from the university is available online so far, but not the study.
In February 2022, the team had already published on the subject in the journal "Nature Astronomy".
Atmospheric methane could be the first sign of life beyond Earth, the press release says.
The gas is suitable as a so-called “biosignature”, a trace of life.
And it can be measured and detected with currently available instruments - for example with the James Webb Space Telescope, which is scheduled to start observations this year.
Methane can also escape from a volcanic eruption
Methane is a colorless and odorless gas that occurs in nature primarily through the microbial degradation of biomass.
Microorganisms decompose organic material in the absence of oxygen.
Methane is produced as a metabolic product.
If the substance were measured in the atmosphere of an alien planet, it could mean that there are living organisms there.
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However, methane can also be released during non-biological processes, for example during a volcanic eruption, asteroid impact or in hydrothermal vents on the sea floor.
However, methane is not particularly stable in the atmosphere.
In order for high methane levels to be maintained over a long period of time, new gas must be continuously emitted.
"Typically, when you find a lot of methane on a rocky planet, it can only be explained by a massive source," says researcher Joshua Krissansen-Totton, who was involved in the study.
“We know that biological activities produce large amounts of methane on Earth.
This was probably the case on early Earth as well, since the production of methane is a fairly simple matter and is possible through metabolic processes."
A “framework for the interpretation of observations”
Non-biological sources, such as volcanoes, could not produce such large amounts of methane without providing observable clues as to where the gas came from.
For example, if a volcano were to release methane into a planet's atmosphere, carbon monoxide would also be released.
In biological processes, on the other hand, carbon monoxide is usually consumed sooner.
According to the experts, it is unlikely that non-biological processes could easily produce a habitable planetary atmosphere rich in both methane and carbon dioxide - while containing little or no carbon monoxide.
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According to the scientists involved, the study provides precise descriptions of when methane is a reliable biosignature and can actually be interpreted as an indication of extraterrestrial life.
"We wanted to create a framework for interpreting observations," said researcher Maggie Thompson, "so that when we see a rocky planet with methane, we know what other observations are needed for it to be a convincing biosignature."
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