Astronomers have detected a molecule in the atmosphere of a distant planet
that, on Earth, is only known to be produced by living organisms. The
finding, detailed in a new peer-reviewed study in Astrophysical Journal
Letters, comes from data gathered by NASA’s James Webb Space Telescope.
The planet in question, K2-18b, lies 124 light-years from...

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#^Webb Telescope Spots Potential Biosignature on Distant Exoplanet

Astronomers have detected a molecule in the atmosphere of a distant planet that, on Earth, is only known to be produced by living organisms. The finding, detailed in a new peer-reviewed study in Astrophysical Journal Letters, comes from data gathered by NASA’s James Webb Space Telescope.

The planet in question, K2-18b, lies 124 light-years from Earth and orbits a red dwarf star. It is believed to be a “hycean” world, a class of exoplanets with hydrogen-rich atmospheres and deep oceans. Researchers have now found evidence suggesting the presence of dimethyl sulfide (DMS), a compound on Earth generated primarily by the decay of marine microorganisms, such as phytoplankton.

Cautious Optimism from Lead Researchers

Despite the promising nature of the detection, scientists are urging restraint. “This is the first time humanity has ever seen biosignature molecules (potential biosignature molecules) in the atmosphere of a habitable-zone planet,” said lead author Nikku Madhusudhan, an astrophysicist at the University of Cambridge.

While he acknowledged the molecule’s biological origins on Earth, Madhusudhan emphasized that more data is needed to confirm its presence and determine its origin. His team’s observations, using Webb’s mid-infrared instrument in April 2024, strengthened their initial findings from 2023. That earlier data had already identified carbon dioxide and methane in the planet’s atmosphere.

Not Yet Proof of Life

The study’s authors stress that while DMS could be a biosignature, it is not definitive proof of extraterrestrial life. In a statement, Cambridge University noted that an unknown chemical process could also account for the molecule’s presence.

Astrophysicist Sara Seager outlined the hurdles ahead: “(1) Is the signal real? (2) Is it correctly attributed to the proposed gas, or could other gases produce the same feature? (3) Can the gas be produced without life?” She added that the third question “may never be fully resolved with the limited data exoplanets offer.”

NASA also tempered expectations, stating that the detection of a single gas does not constitute the discovery of life.

A New Frontier in the Search for Life

K2-18b, first discovered in 2015 by the Kepler Space Telescope, is around 2.4 billion years old and roughly 2.5 times Earth’s diameter. Its short 33-day orbit keeps it within the habitable zone of its star system.

The research team hopes for further observation time with Webb to confirm their findings. “Either we are looking at a new chemical process that we haven’t seen before … or we’re witnessing the first signs of biological activity outside of Earth,” said co-author Mans Holmberg.

Though far from conclusive, the discovery marks a significant step in the long quest to answer whether we are alone in the universe.

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