The James Webb telescope would have detected « clues » linked to life on an exoplanet – Liberation
Figures, letters, and the hope of traces of life. K2-18Bexoplanet located at 124 light years from the earth, in the Constellation of the Lion, is the subject of animated debates within the scientific community, which wonders if it could be an oceanic world likely to house a microbial life. This Thursday, April 17, a team of American-British researchers announced that it has detected, using The James Webb space telescopein its atmosphere signs of chemical compounds long considered as « biosignatures » of a possible extraterrestrial life – dimethyl sulfide and dimethyl disulfide, which on earth are only produced by living organisms, mainly phytoplankton. Or the most promising « indices » to date of a potential life on a planet outside our solar systemaccording to astronomers.
« What we observe at this stage are indices of a possible biological activity outside the solar system », said at a press conference Nikku Madhusudhan, astrophysicist at the University of Cambridge and the main author of the study published in The Astrophysical Journal Letters. « To be frank, I think this is the case closest to a characteristic that we can attribute to life », He said, while stressing that other observations were necessary.
The telescopes manage to observe the exoplanets when they transit in front of their star, allowing astronomers to analyze how the molecules filter the light which crosses their atmosphere and to deduce its composition. In 2023, James Webb had already detected the presence of methane and carbon dioxide in the atmosphere of K2-18B. A first for an exoplanet located in the « habitable zone », that is to say neither too close, nor too far from his star so that there is an essential ingredient to life: from water to the liquid state. He had also recorded low dimensions of dimethyl sulfide, leading astronomers to reject the NASA telescope to K2-18B a year ago, this time using other wavelengths.
If the signs are now much sharper, they remain far below the threshold of statistical meaning considered crucial by scientists to validate a discovery. And researchers who did not participate in the study call to take these results with caution: last year, scientists thus found traces of dimethyle sulphide on a comet, suggesting that this substance could be produced by means still unknown, without link with life. Its concentration on K2-18B seems to be thousands of times higher than the levels recorded on earth, pointing strongly towards a biological origin, however advances Nikku Madhusudhan.
Another difficulty, K2-18B, with a mass more than eight times that of the earth and a diameter 2.5 times higher, orbit around its star in just thirty-three days. For Raymond Pierrehumbert, professor of planetary physics at the University of Oxford, who studied it, she would therefore be too hot to shelter life. « If this planet had water, it would be an infernal furnace, completely uninhabitable », He told AFP, adding that lava oceans were more plausible.
Previous announcements on the discovery of water vapor in its atmosphere has proven to be wrong, also reminds AFP Sara Seager, professor of planetary sciences at MIT (United States). Within our solar system, Mars, Venus and moons like Encelade – a Saturn satellite – have « More chances » to shelter life, she believes. According to Nikku Madhusudhan, sixteen to twenty-four hours of additional observations should not be sixteen with the James Webb telescope to confirm-or invalidate-the presence of dimethyle sulfide. Which could happen in the coming years.
