In what could mark a turning point in the search for extraterrestrial life, researchers using NASA’s James Webb Space Telescope have detected intriguing chemical traces in the atmosphere of a distant planet that may suggest biological activity.

The planet, K2-18 b, is located more than 100 light-years away and orbits within its star’s habitable zone—the region where conditions may support liquid water. What makes this discovery particularly compelling is the presence of two gases—dimethyl sulfide (DMS) and dimethyl disulfide (DMDS)—which, on Earth, are produced almost exclusively by living organisms, especially ocean-dwelling microbes like phytoplankton.

While scientists emphasize that this is not confirmation of alien life, the findings represent what may be the most compelling biosignature detected outside our solar system to date.

“This could be a game-changer in our understanding of potentially habitable worlds,” said Dr. Nikku Madhusudhan, an astrophysicist at the University of Cambridge and lead author of the study, which appears in the Astrophysical Journal Letters. “We’re seeing chemical markers that, as far as we know, only living things produce here on Earth.”

The discovery suggests that microbial life—if it exists on K2-18 b—might thrive in a manner similar to marine life on Earth. Still, researchers urge caution. More data and follow-up observations are needed to confirm the source of these gases and rule out non-biological explanations.

K2-18 b is considered a “Hycean” planet, meaning it could have a hydrogen-rich atmosphere and a liquid water ocean beneath. It is approximately 8.6 times the mass of Earth and more than twice as wide, suggesting a vastly different environment than our own.

“We’ve now entered a new era where we can begin to directly study the atmospheres of planets beyond our solar system,” Madhusudhan said. “It’s an exciting time for observational astrobiology.”

The research is part of a broader scientific effort to detect signs of life across the cosmos, as missions continue to explore potentially habitable environments not only around distant stars but also within our own solar system—on Mars, Venus, and the icy moons of Jupiter and Saturn.