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The discovery of life outside the solar system, which is more technologically advanced, would undoubtedly be one of the greatest scientific discoveries of all time, with far-reaching philosophical implications. It is possible that this will happen by 2050 by analyzing the atmospheres of many exoplanets near the Sun, which we can already begin to do to a significant extent during planetary transits with the James Webb Space Telescope (JWSTJWST).
To do this, however, we ultimately need to identify possible biosignatures, since there are no technosignatures that are significantly less ambiguous a priori. In fact, to detect them we would need to find a set of molecules that we would be reasonably certain cannot be produced by natural phenomena, or, as exobiologists would say, that they are not abiotic.
A team of researchers has just published a paper in Nature Astronomy, the open access version of which can be found on arXiv, providing elements of this search for the Holy Grail of Life elsewhere.
This work indirectly concerns an exoplanet that has been studied for more than a decade and whose discovery was made using the radial velocity method with the Harps instrument, a spectrometer-spectrometer equipped with the ESOESO 3.6-meter telescope in Chile . AstronomersAstronomers then discovered Gliese 1214 b (GJ 1214 b), completing its orbit in 38 hours around a red dwarf located about 40 light-years from Earth in the constellation Ophiuchus (Slytherin).
It would have a radius of about 2.6 times the radius of Earth and would be about 6.5 times more massive, which would put it more in the category of super-Earths, although some prefer to call it a mini-Neptune. Its host star, as its name suggests, is number 1214 in the Gliese-jahriss catalog (named after astronomers Wilhelm Gliese and Hartmut Jahriss), which attempts to list all stars at a distance of less than 25 parsecsparsecs from Earth.
A planetary atmosphere has a spectral signature that represents its chemical composition, but also its cloud and “mist” composition. Thanks to various techniques, it is possible to determine the physicochemical properties of the atmosphere of an exoplanet. These techniques include: spectroscopic transit, secondary transit or eclipse, direct spectroscopic observation of the planet, or even observation of the planet in different phases around the star to measure temporal and seasonal variations. Discover exoplanets in our 9-part web series, available on our YouTube channel. A playlist proposed by the CEA and the University of Paris-Saclay as part of the European research project H2020 Exoplanets-A. © CEA
Spectra through transmission of problematic atmospheres
The authors of the publication in Nature include Sarah Hörst, Professor of Earth and Planetary Sciences at the renowned Johns Hopkins University. Years ago, she and her colleagues first set out to create computer models of various atmospheres that might be possible on super-Earths, super-Earths and mini-Neptunes, none of which exist in our solar system.
This involved combining different fractions of carbon dioxide (carbon dioxide, hydrogen, hydrogen and water) with helium, helium, carbon monoxide, carbon monoxide, methane and nitrogen, nitrogen, all at different temperatures, to see what happened.
The researchers then tested the models’ predictions in these atmospheres in the laboratory by circulating these gases through a plasma chamber to simulate interactions with the solar wind corresponding to the solar wind, which produced haze particles.
One of the goals of the current experiments, which expand on the previous ones and are discussed today, was to learn more about how organic haze particles (which are also thought to be photochemically present in the atmosphere of temperate exoplanets < 1,000 K, which are the preferred targets are produced photochemically). for observations to assess their habitability) influence the spectra observed by telescopes such as the JWST.
On the one hand, we could not rule out that the compositions and properties of the organic nebulae of exoplanets could be very different from what we know for the solar system and, on the other hand, and most importantly, that they could change the transmission spectra (see video above). ), emissionEmission and reflected lightreflected light. Understanding this is therefore essential for interpreting spectroscopic data from exoplanets in order to understand their atmospheres in the context of exobiology. Six years ago, however, Sarah Hörst showed that the hydrocarbon nebulae that shroud Titan, the moon of SaturnSaturn, could form in the atmosphere of super-Earths and mini-Neptunes.
The atmosphere of Gliese 1214 b in the laboratory on Earth
Today the researcher has just reproduced results on the atmosphere of Gliese 1214 b and, icing on the cake, announced this after the exoplanet has been examined in more detail by James-Webb!
The press release from Johns Hopkins University contains numerous comments from the researcher and her colleagues. Sarah Hörst explains: “The most important thing is to know whether there is life outside the solar system, but to answer this type of question we need very detailed modeling of all types of exoplanets, especially those with a lot of water.” “It was a big challenge because we simply didn’t have a laboratory for it. That’s why we’re trying to use these new techniques to get the most out of the data we collect with all the large, sophisticated telescopes.”
The new experiments were therefore carried out in a specially designed chamber in Hörst’s laboratory. His co-author of the online article, planetary scientist Chao He, says: “Water is the first thing we look for when we want to find out whether a planet is habitable, and there are already exciting observations of water in the atmosphere of exoplanets .” But our experiments and modeling suggest that these planets most likely also contain haze. This haze really complicates our observations because it obscures our view of the atmospheric chemistry and molecular properties of an exoplanet.”
Exobiologists therefore looked at gas mixtures containing water vapor that exposed them to ultraviolet light, as occurs under the conditions of light emitted by a star, to see more clearly the photochemical reactions that lead to the formation of solid organic particles that form nebulae .
The new data obtained matches the chemical signatures observed in the GJ 1214 b case more closely than previous research, leading Hörst to say that “people can use this data when modeling atmospheres to try to predict things like temperature in the atmosphere.” and whether there are clouds on the surface of this planet, how high they are and what they are made of or how fast the winds are. All of these things can help us really focus our attention on specific planets and make our experiments unique, rather than just doing general tests to try to understand the big picture.”