A world-one world with a global water ocean and an atmosphere rich in hydrogen-orbit in orbit a red dwarf star in the concept of this artist. Credit: A. Smith, N. Madhusudhan (Cambridge University)
Scientists reported new observations from the James Webb Space Telescope (JWST) of NASA who strengthen the case that the exoplanetic K2-18 B has molecules in its atmosphere which, on earth, are produced only by life.
The work, announced on Wednesday, is based on previous JWST observations published in 2023 by the same team that produced weak suggestions of the Dimetyl Solfuro molecule (DMS) on K2-18 B, a planet that the team thinks could be covered by a global ocean. In the new data, further spectra taken with a different on -board tool have seen further tests of the chemical signal of the DM, as well as signs of a correlated molecule, disolfuro dimetyl (DMD).
The team says that they are not claiming to have discovered life and that it is essential to collect more data to confirm the detection. However, they are not moving away from underlining what they feel is the gravity of the moment – which detects the molecules I could Being potential signs of life in other star systems are now within the reach of our most powerful telescopes. In the media comments during an embargo press conference Tuesday reported by points of sale such as The New York TimesThe leader of the team Nikku Madhusudhan of the University of Cambridge, in the United Kingdom, said it was a “revolutionary moment”.
Madhusudhan also claimed that the best explanation for data is that K2-18 B hosts life. But in the astronomical community, the proposal was accepted with a healthy dose of skepticism. Many praised JWST’s power to be able to try the detections of these weak signals. But there has also been a widespread caution applied to any interpretation that invokes life, since recent studies have discovered that even DMS can be produced without life.
The Mit Sara Seager scientist said the planetary scientist Astronomy That “with thousands of exoplanets in sight, the temptation of over-interpreter is strong-and some are jumping the gun. When it comes to K2-18 b, the enthusiasm is overcoming the tests”.
Biosignatura or not?
At 124 light years of distance in the Leo constellation, K2-18 b orbit in the habitable area of its red-dwarf-a star star a distance in which the surface temperature of the planet can support liquid water. But about 8 or 9 times as much as the Earth – equivalent to half the mass of the Nettuno ice giant – is not clear how that surface is.
JWST’s observations that Madhusudhan’s team reported in 2023 showed clear signs of methane (CH4) and carbon dioxide (CO2) in its atmosphere. This, they supported, adapts to a scenario in which an atmosphere rich in hydrogen surrounds a planet with global water (h2O) ocean that could support life. They nicknamed this scenario a “Hycean” world, taken from hydrogen and ocean words. (Other studies, as one published in Arxiv Preprint server on the same day as the new work, they say that different scenarios are more likely for the planet. They include the possibility of a global magma ocean – “about inhospitable as you get”, says Seager – or a mostly gaseous makeup.)
At the time, the team noticed even weak signs of DMS in the data, taken from the spectrograde to infrared near JWST. DMS has been designed by astrobiologists for its potential to indicate life – what scientists call a biosignatura – for over a decade. But the meaning of the detection barely risen to a level of 2-sigma, which means that there was a 5 % probability of the signal that appears by chance-ben of the 5-sigma level considered the statistical Gold Standard in science.
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The new data come from JWST’s medium infrared spectrograde and bring the detection to a 3–sigma level, according to the analysis of the team, which means that there is a probability of 0.3 percent of data that adapt to the spectrum of the model provided for those molecules and does not only do so by chance. With 16-24 additional hours of observation of the time, they think they can reach the 5-Sigma brand, a probability of 0.00006 percent of adapting to the model so well. However, these statistical analyzes can sometimes be misleading as they do not take into account the possibility that the model is wrong or that the data have captured some other chemical that imitates the appearance of the model.
Even if the detection is confirmed, the question remains: how reliable the DMS is as a biosignatura? On Earth, DMS is produced by life such as phytoplankton. It is part of the smell of a marine breeze. And as far as scientists know, life is the only way in which the DMS is produced on earth.
But this does not mean that it cannot be produced by non -living means elsewhere in the universe.
A year ago, the researchers reported a DM detection on the Comet 67P/Churyumov-Gerasimenko-Quasi a full position of life. (The team found the signal in the archive data of the Rosetta Mission of the European Space Agency.) In September last year, a team of researchers reported that in the laboratory experiments, they were able to produce DMS by lighting UV on an atmosphere of simulated and nebulous exoplanet. This suggests that the reactions between the photons and molecules of a star in the atmosphere of a planet could provide a non -biological way to produce DM. And this February, a team of sparse astronomers reported the detection of DM in gas and dust between the stars. All these results challenge the idea that DMS is a clear sign of life.
The team refers to the photochemical experiment in their document, but claims that these reactions could not produce the amount of DM they find on K2-18 b. Neither of them say, the impacts of the comet could provide DMS in the quantities they observe with JWST.
In printing
JWST’s new results were advertised on April 16 in a wave of news published at 19:00 EDT, accompanied by a press release from the University of Cambridge.
According to these reports, the document was published on April 16 in The letters of Astrophysics magazine. When this story was published for the first time, six hours later, the document was not yet online at the link provided to journalists. However, during that period, a manuscript preprint was published in the Arxiv. (In the end the document appeared The letters of Astrophysics magazine Website in the first morning EDT, listed with a publication date of April 17th.)
In the Cambridge press release, Madhusudhan observed: “It is important that we are deeply skeptical towards our results, because it is only by testing and testing again that we will be able to achieve the point where we are confident in them. … This is how science must work.”
NASA, who published a press release when the previous JWST observations of Madhusudhan and its colleagues were published on the K2-18 B, did not issue a press release in the new study.
But the agency seemed to distance himself from speculation on the “discovery of life” or “real biosignures” in a declaration a The Washington PostBy suggesting that the JWST data alone may not be convincing enough. The scientific journalist Joel Achenbach has published on Bluesky that NASA told him that “the detection of a single potential biosignatura would not constitute the discovery of life. We would probably need more lines of convergent evidence to confirm real biosignures and exclude false positives, possibly including data independent of multiple missions.”
In other reactions, the planetary scientist Sarah Hörst of the Johns Hopkins University has led to Bluesky to reject the affirmation that the DMS is equivalent to a biosignatura, indicating the laboratory experiments that show that it can be produced without life.
On the other hand, Astrophysical Adam Frank of the University of Rochester wrote: “This is so exciting. It could go away with more data but it is exactly the type of path that we would expect on the road [to] find life. “
David Kipping, an astronomer at Columbia University, published on X that was worth remembering that the molecule detected (DMS) does not necessarily mean life “. But, he added, he is” exciting JWST can touch this sensitivity! “
Note of the editor: This story has been updated with additional quotes.
