[REVIEW] : NASA could detect inhabited planets by tracing methane

Methane. With the chemical formula CH4. It’s a powerful greenhouse gas. Which we may soon have to hunt. Just as we are already chasing the carbon dioxide (CO2). To limit the global warming anthropogenic. But researchers at the University of California at Santa Cruz (United States), they propose to hunt methane in a completely different place than the atmosphere of our Earth and for a completely different reason. Because in the atmospheres of exoplanets, it could mark the presence of extraterrestrial life forms.

the methane as a biosignature — the sign that a form of life has passed through there. The astronomers are particularly interested in it today. Because it could be detectable in the atmosphere of some exoplanets thanks to the James-Webb Space Telescope (JWST). But be careful! Methane, indeed, can also be emitted by non-biological processes.

While waiting for the first observations of the JWST, the researchers looked into the question. To follow their reasoning, it is good to remember that methane does not stay long in the atmosphere. In just a few years, it was destroyed by photochemical reactions. Thus, the only explanation for the detection of a quantity of methane in an atmosphere is the presence of a source which emits it more or less continuously.

Biosignature or not, the important thing is to avoid errors

And it is possible that non-biological sources emit a lot of methane as well. From volcanoesreactions that occur for example in mid-ocean ridge type environments, chimneys hydrothermal vents or areas of subduction tectonics or impacts of comets orasteroids. But what researchers at the University of California suggest today is that these sources would then necessarily generate in parallel other observable clues betraying the origin of all this CH4. the degassing volcanoes, for example, would add both methane and carbon to the atmosphere of a rocky exoplanet. carbon monoxide (CO). What biological sources would not do.

According to astronomers, therefore, if methane can give an important clue, it remains only a simple piece of the puzzle of the extraterrestrial life. And the study published in the Proceedings of the National Academy of Sciences (USA) offers some guidelines to avoid “false positives”. To also prevent researchers from unfortunately missing out on a real biosignature.

For example, on a rocky planet in orbit around a star similar to our Sun, methane could begin to form a robust biosignature if said planet’s atmosphere also contains CO2 and if CH4 is far more abundant than CO. But in matter of extraterrestrial atmospheres, there is still much to learn. And researchers at the University of California are calling for more work on the subject. Studies that could analyze even the most unusual mechanisms of non-biological methane production. In order to avoid as much as possible the errors of interpretation of the results which could be transmitted soon by the James Webb Space Telescope.

A simulation predicts what the James-Webb of the first billion years of the Universe will be able to see

The 1960s saw the discovery of two phenomena astrophysics who quickly accredited the theory of big Bang by Georges Gamow and Georges Lemaitremaking increasingly untenable the previous standard cosmological model where the observable cosmos was only a fraction of a universe infinite. An eternally expanding universe without beginning or end in which processes of creation of matter gave rise to new galaxies to maintain a constant material density despite the diluting effect of expansion.

These phenomena were quasarswhich are now known to be most likely supermassive black holes of Kerr in rotation accreting a lot of matter, and the cosmic radiation.

Quasars have strong lines ofepisode Lyman-alpha, i.e. an emission of photons in the field ofultraviolet well described by Bohr model of the’atom of hydrogen which de-excites in a certain way. These emission lines are also produced in the same way by matter heated by the birth of young stars in galaxies.

the red shift of spectrum quasars that are measured with a quantity denoted “z” which is all the higher as a quasar is observed far away, therefore early in the history of the observable cosmos, indicates to us according to the law of Hubble-Lemaître that they are mostly located billions oflight years of the Milky Way. We also observe a series of lines ofabsorption in the quasar spectrum. This is the same Lyman-alpha emission line absorbed by matter between a quasar and an instrument on Earth. But as the distances of the quasars vary, we also see lines shifted according to the distance and which ultimately form what are called Lyman-alpha forests.

It is paradoxical, as evidenced by the taking into account at a given moment of an effect discovered by astrophysicists James Gunn and Bruce Peterson in 1965. Indeed, neutral hydrogen known to exist between galaxies should quite quickly block measurable Lyman-alpha radiation by absorbing it. Unless you imagine that part of the hydrogen present is ionized.