Methane may be the first sign of life beyond Earth

Although non-biological processes can generate methane, a new study by scientists at Santa Cruz University, California, It identifies a set of conditions under which a compelling case of biological activity as a source of methane in the atmosphere of a rocky planet can be presented.

Methane is one of the few potential signs of life, or biosignatures, that can be easily detected with the James Webb Space Telescope. (JWST), released by NASA in December. “Oxygen is often talked about as one of the best biometric fingerprints, but it can be difficult to detect. with JWST”. Maggie ThompsonPostgraduate student in Astronomy and Astrophysics at the University of California, Santa Cruz (UCSC) and lead author of the new study.

Biometrics or indicators of life are substances, items, or phenomena that provide scientific evidence of possible signs of life, either in the past or in the present. Despite some previous studies of methane’s biosignatures, there has been no up-to-date, dedicated assessment of the planetary conditions necessary for methane to be a good indicator of life.

We wanted to provide a framework for interpreting the notes, so If we see a rocky planet with methane in it, we know what other observations are needed to make it a convincing biosignature.Thompson noted.

Posted in Proceedings of the National Academy of SciencesAnd the The study examines a variety of non-biological sources of methane and assesses their ability to maintain a methane-rich atmosphere. These include volcanoes. interactions in environments such as mid-ocean ridges, hydrothermal vents, and tectonic subduction zones; Comet or asteroid impacts.

The issue of methane as a vital signature stems from its atmospheric instability.. Since photochemical reactions destroy atmospheric methane, it must be continually replenished to maintain its high levels.. “If a large amount of methane is detected on a rocky planet, an enormous source is usually needed to explain its appearance. Full co-author Joshua Krissansen-Totton, also a member of UCSC-. We know that biological activity produces large amounts of methane on Earth, and that may have happened in the early stages as well, because methane production is very easy metabolically. “

However, Non-biological sources cannot produce the same amount of methane without generating observable evidence about its origins. Outgassing from volcanoes, for example, would add both methane and carbon monoxide to the atmosphere, while biological activity tends to easily consume carbon monoxide. The researchers found that non-biological processes could not easily produce habitable planetary atmospheres rich in methane and carbon dioxide with little or no carbon monoxide.

The study emphasized the need to take into account the full planetary context when assessing potential biosignatures.. The researchers concluded that For a rocky planet orbiting a sun-like star, atmospheric methane would likely be considered a strong signal of life if the atmosphere also contained carbon dioxide.Methane is more abundant than carbon monoxide and very rich in water. Planetary formations can be excluded.

“The molecule will not give you the answer, you have to take into account the whole context of the planet Thomson warned. “Methane is one piece of the puzzle, but to determine if there is life on a planet, you have to think about its geochemistry, how it interacts with its star, and the many processes that can affect a planet’s atmosphere on geological time scales. “

The study looked at a variety of false positives and provided guidelines for assessing methane’s biosignatures.. “There are two things that can go wrong: We can misread something as a bio signature and get a false positive, or we may miss something that is a true bio signature Krissansen warned Totton. With this document, we wanted to develop a framework to avoid each of these potential risks with methane. “

The authors state that there is still much work to be done to fully understand any future discovery of methane.. “This study focuses on the most obvious false positives for methane as a biological classification,” Krissansen-Totton concluded. ambiance outer planets The rocky outcrops are likely to surprise us, and we’ll have to be careful in our interpretations. Future work should attempt to anticipate and estimate the more unusual mechanisms of non-biological methane production.”

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