2023-12-03 20:40:16
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The discovery of life outside the Solar System, furthermore technologically developed, would undoubtedly be one of the greatest scientific discoveries of all time, with major philosophical implications. It is possible that this will happen by 2050 by analyzing the atmospheresatmospheres of many exoplanets near the Sun, which we can already begin to do in a meaningful way during planetary transitsplanetary transits using the James Webb Space Telescope (JWSTJWST) ).
However, for this we ultimately need to determine possible biosignatures, in the absence of technosignatures which are first significantly less ambiguous. Indeed, we would have to find a set of molecules to detect of which we would be reasonably sure that they cannot be produced by natural phenomena, or as exobiologists would say that they are not abioticabiotic.
A team of researchers has just published an article in Nature Astronomy an open access version of which can be found on arXiv which brings elements to this quest for the Grail of Life elsewhere.
This work indirectly concerns an exoplanet studied for more than a decade and whose discovery was made using the radial velocity method using the Harps instrument, a spectrometer spectrometer equipping the 3.6 meter telescope of the ESOESO in Chile. Astronomersastronomers then discovered Gliese 1214 b (GJ 1214 b) which completes its orbitorbit in 38 hours around a red dwarfred dwarf located about 40 light-years from Earth in the constellation Ophiuchus (Slytherin).
It would have a radius of approximately 2.6 times that of the Earth and would be approximately 6.5 times more massive, which would place it more in the category of super-Earths but some prefer to call it a mini-Neptune. . Its host star has, as its name indicates, number 1214 in the Gliese-Jahreiss catalog (named after astronomers Wilhelm Gliese and Hartmut Jahreiss) which attempts to list all stars at a distance within 25 parsecsparsecs of Earth.
A planetary atmosphere has a spectral signature which represents its chemical composition, but also its composition in clouds and “fog”. Thanks to several techniques, it is possible to determine the physicochemical characteristics of the atmosphere of an exoplanet. Among these techniques: spectroscopic transit, secondary transit or eclipse, direct spectroscopic observation of the planet or even observation of the planet at different phases around the star in order to measure temporal and seasonal variations. Discover exoplanets through our 9-episode web series, available on our YouTube channel. A playlist proposed by the CEA and the University of Paris-Saclay as part of the H2020 Exoplanets-A European research project. © CEA
Spectra by transmission of problematic atmospheres
Among the authors of the publication in Nature, we find Sarah Hörst, professor of Earth and planetary sciences at the famous Johns Hopkins University. Years ago, she and colleagues first set out to create computer models of various atmospheres that might be possible on super-Earthssuper-Earths and mini-NeptunesNeptunes, none of which are found in our solar system.
This involved combining various fractions of carbon dioxidecarbon dioxide, hydrogen hydrogen and water with heliumhelium, carbon monoxidecarbon monoxide, methane and nitrogennitrogen, all at different temperatures, and to see what was happening.
The researchers then tested the models’ predictions in these atmospheres in the laboratory, circulating these gases through a plasma chamber to simulate interactions with the solar wind’s equivalentsolar wind, which produced haze particles.
One of the goals of the current experiments, extending the previous ones and discussed today, was to learn more about how organic haze particles (which are also thought to be produced photochemically in atmospherics of temperate exoplanets, < 1,000 K, which are the preferred targets for observations to assess their habitability) impact the spectraspectrums observed by telescopes like the JWST.
We could not exclude on the one hand that the compositions and properties of the organic mists of exoplanets could be very distinct from what we know for the Solar System and on the other hand and above all that they could modify the transmission spectra ( see video above), emissionemission and reflected lightreflected light. Understanding how is therefore essential for interpreting spectroscopic data from exoplanets in order to understand their atmospheres within the framework of exobiology. Six years ago, however, Sarah Hörst showed that the hydrocarbon mists that envelop Titan, Saturn’s moon, could form in the atmospheres of super-Earths and mini-Neptunes.
The atmosphere of Gliese 1214 b in the laboratory on Earth
Today, the researcher has just reproduced results concerning the atmosphere of Gliese 1214 b and, the icing on the cake, this is announced after the exoplanet was examined more closely by the James-Webb!
The Johns Hopkins University press release contains numerous comments from the researcher and her colleagues. Sarah Hörst explains that “ The bottom line is whether there is life outside the Solar System, but answering that kind of question requires very detailed modeling of all types of exoplanets, especially those with a lot of water. It’s been a huge challenge because we just haven’t had a lab to do it, so we’re trying to use these new techniques to get the most out of the data we’re collecting with all the big, sophisticated telescopes. ».
The new experiments were therefore carried out in a custom-designed chamber in Hörst’s laboratory. His co-author of the online article, planetary scientists Chao He, specifies that: “ Water is the first thing we look for when trying to see if a planet is habitable, and there are already exciting observations of water in the atmospheres of exoplanets. But our experiments and modeling suggest that these planets very likely also contain haze. This haze really complicates our observations, because it obscures our view of the atmospheric chemistry and molecular characteristics of an exoplanet. ».
Exobiologists therefore considered gas mixtures containing water vapor which they exposed to ultraviolet light, as in the conditions of that emitted by a star, in order to see more clearly the photochemical reactions leading to the formation of solid organic particles forming mists.
The new data obtained correspond more precisely to the chemical signatures observed in the GJ 1214 b case than previous research, leading Hörst to say that “ people will be able to use this data when they model atmospheres to try to understand things like the temperature in the atmosphere and on the surface of this planet, if there are clouds, how high they are, and what they are constituted, or how fast the winds are. All of these kinds of things can help us really focus our attention on specific planets and make our experiences unique instead of just running generalized tests to try to understand the big picture ».
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