In a breakthrough that could reshape the search for extraterrestrial life, scientists have uncovered the most compelling evidence to date of potential biological activity beyond Earth. Researchers from the University of Cambridge, using data from the James Webb Space Telescope (JWST), have detected chemical signatures in the atmosphere of exoplanet K2-18 b that—on Earth—are exclusively produced by living organisms.
A Promising Candidate for Life
Located 124 light-years away in the constellation Leo, K2-18 b orbits within the habitable zone of its host red dwarf star, where temperatures might support the presence of liquid water. Classified as a “hycean world,” the planet is believed to have a hydrogen-rich atmosphere and possibly an ocean-covered surface—ideal conditions for supporting microbial life.
According to Reuters, the planet’s unique characteristics have long made it a prime candidate in the search for extraterrestrial biospheres.
A graph shows the observed transmission spectrum of the habitable zone exoplanet K2-18 b using the James Webb Space Telescope MIRI spectrograph instrument. The vertical shows the fraction of star light absorbed in the planet’s atmosphere due to molecules in its atmosphere. The data are shown in the yellow circles with the 1-sigma uncertainties. The curves show the model fits to the data, with the black curve showing the median fit and the cyan curves outlining the 1-sigma intervals of the model fits. The absorption features attributed to dimethyl sulphide and dimethyl disulphide are indicated by the horizontal lines and text. The image behind the graph is an illustration of a hycean planet orbiting a red dwarf star. This image was obtained by Reuters on April 16, 2025. A. Smith, N. Madhusudhan/University of Cambridge/Handout via REUTERS NO RESALES. NO ARCHIVES. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY.
Detection of Potential Biosignatures
The JWST observations revealed the presence of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS)—chemical compounds that, on Earth, are predominantly produced by marine microorganisms such as phytoplankton.
While not conclusive proof of life, these compounds are considered strong biosignatures, or indicators of biological processes. Their detection marks a major milestone in the field of astrobiology.
“This is a transformational moment in the search for life beyond the solar system,” said Professor Nikku Madhusudhan, lead researcher from the University of Cambridge. “We have demonstrated that it is possible to detect biosignatures in potentially habitable planets with current facilities. We have entered the era of observational astrobiology.”
A Measured Approach
Though the findings have generated excitement across the scientific community, researchers caution against premature conclusions. The current data indicates only a 0.3% probability that these compounds occurred by chance, according to the University of Cambridge. Still, scientists stress the importance of further observations to rule out non-biological origins.
An artist’s concept shows what exoplanet K2-18 b could look like based on science data. The illustration was released on September 11, 2023. NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)/Handout via REUTERS NO RESALES. NO ARCHIVES. THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY.
The discovery has been published in The Astrophysical Journal Letters and is expected to catalyze further studies of exoplanetary atmospheres.
Broader Implications for the Search for Life
K2-18 b joins a growing list of planetary bodies—alongside Mars, Venus, and icy moons like Europa and Enceladus—being studied for their potential to harbor life. Yet the ability to detect biosignatures at such vast distances highlights a new era in space exploration.
“Decades from now, we may look back at this point in time and recognise it was when the living universe came within reach,” Madhusudhan added. “This could be the tipping point, where suddenly the fundamental question of whether we’re alone in the universe is one we’re capable of answering.”
As humanity continues to push the boundaries of astronomical research, K2-18 b may represent more than just another data point—it could be the first glimpse of a living world beyond our own.
