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Scientists Cambridge University have identified promising signs of extraterrestrial marine life in the exoplanet's atmosphere K2-18b. The substances DMS e DMDS, recognized by the James Webb Telescope on the exoplanet, are produced exclusively by living organisms — mainly by microscopic marine life forms — here on Earth, which takes the discovery to a new chapter in the search for life on another planet. Understand how James Webb detected the molecules and what they mean for the existence of life outside Earth. 2a6br
How the discovery was made 6v571m
The discovery was made possible by the advanced observation capabilities of the James Webb Space Telescope (JWST), developed by NASA in partnership with European Space Agency (ESA) and Canadian Space Agency. Using spectroscopy technology — which allows the analysis of light that es through the atmosphere of distant planets as they transit in front of the star they orbit — the telescope identified specific chemical patterns on the exoplanet. K2-18b.
These patterns indicate the presence of molecules such as dimethyl sulfide (DMS) and dimethyldisulfide (DMDS), gases associated with biological activity on Earth. This is possible because certain compounds leave unique marks on the light that reaches us, as if they were chemical signatures.
Largely responsible for research, Professor of Astrophysics and Exoplanetary Sciences at the Institute of Astronomy at the University of Cambridge, Nikku Madhusudhan, spoke about the size of the discovery:
“Decades from now, we may look back on this moment and recognize that this is when the living universe became accessible. This may be the tipping point, where suddenly the fundamental question of whether we are alone in the universe becomes something we are able to answer.”
Nikku Madhusudhan, a professor at the Institute of Astronomy in Cambridge, who led the research.
O JWST used different instruments, at different times, to confirm these indications. The first observations, made with spectrographs NIRISS e NIRSpec (which operate in the near-infrared range) had already suggested the possible presence of DMS. To confirm the data, the researchers conducted a new round of observations with MIRI, an instrument that captures mid-infrared.
The second measurement, made at another wavelength and with different equipment, yielded an even clearer and more consistent result, increasing confidence in the discovery and reducing the margin of error.
Getting to know the exoplanet K2-18b 361u3m
The exoplanet K2-18b it's located approximately 124 light years from Earth, in the constellation Leo, and orbits a red dwarf star called K2-18. With about 8,6 times the mass of Earth and 2,6 times its size, it is a planet classified as “sub-Neptune” — that is, larger than Earth, but smaller than the gas giants in our solar system, such as Jupiter, Saturn, Uranus and Neptune.
What makes K2-18b Particularly interesting is the fact that it is located in the so-called “habitable zone” of its star, the region where temperatures can allow the existence of liquid water on the surface, an essential condition for life as we know it. In our solar system, for example, this zone encomes the EARTH e Mars.
Previous observations had already detected methane and carbon dioxide in the atmosphere of K2-18b, important elements in regulating the planetary climate. This carbon-rich composition is compatible with a type of planet known as Hycean — a world possibly covered by oceans and surrounded by a dense atmosphere composed mainly of hydrogen.
This type of planet has been theoretically proposed as a possible environment conducive to the emergence of life, especially in microbial forms. The model Hycean represents a new frontier in astrobiology, as it expands the types of worlds considered habitable beyond those similar to Earth.
“Previous theoretical work predicted the possibility of high levels of sulfur-based gases such as DMS and DMDS on Hycean planets. And now we see this, in line with what was predicted. Given everything we know about this planet, a Hycean planet with an ocean teeming with life is the scenario that best fits the data we have.”
Nikku Madhusudhan, professor at the Cambridge Institute of Astronomy, in a statement to the University of Cambridge itself.
Another important factor is the intensity of the molecules observed. While on Earth compounds such as DMS and DMDS appear in very small quantities — generally below one part per billion —, on K2-18b, it is estimated that these concentrations are thousands of times higher. If these compounds are indeed of biological origin, this could mean that the activity that generates them occurs on a much larger scale than here. On the other hand, scientists do not rule out the hypothesis that these gases are being generated by unknown chemical processes.
Furthermore, the density and structure of the K2-18b indicate that it may harbor vast oceans beneath its thick atmosphere, shielding potential life forms from stellar radiation. Still, its more intense gravity and the composition of its atmosphere make it a very different environment from Earth.
Next steps for confirmation 4v5l2e
Despite the encouraging evidence, scientists cannot yet say with certainty that they have found a habitable exoplanet. The presence of compounds such as DMS e DMDS in the atmosphere of K2-18b, although compatible with biological activity, may also have reasons that do not involve living organisms and are not yet known. Therefore, the team responsible for the discovery maintains a cautious stance and emphasizes that validating a biosignature requires not only repeating the data, but also excluding all possible non-biological alternatives.
In the scientific arena, a discovery is only considered officially confirmed when it reaches the level of statistical significance of five sigma. This means that the chance of the detected signal being the result of chance needs to be less than 0,00006%. Currently, observations made with the James Webb Space Telescope reach the level of three sigma, Ou seja, there is still a 0,3% chance that the result does not represent a real discovery. To achieve the necessary level of confidence, scientists need to continue the analyses and perform additional observations with complementary instruments, independently confirming the data.
The team of researchers themselves estimates that between 16 and 24 extra hours of observation with the JWST may be enough to reach the long-awaited five-sigma mark. In addition, parallel theoretical and laboratory work will be essential to investigate whether the observed compounds could arise without the presence of life. This rigorous care is fundamental to the credibility of the scientific process. After all, faced with a possible answer to one of humanity's oldest questions — "are we alone?" — it is essential that any evidence be based with the utmost precision and responsibility.
What did you think of this discovery? Tell us in the comments!
See also:
Sources: with the BBC, The Annapurna News e NY Times.
Text revised by Felipe Faustino in 17 / 04 / 2025
