Scientists using the James Webb Space Telescope have found strong signs of possible alien life on K2-18 b, a planet 124 light-years away. They detected dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in its atmosphere—gases that on Earth come only from biological sources like marine phytoplankton.
The researchers say this discovery does not confirm living organisms. Instead, it suggests a potential biosignature—evidence that life-related processes might be happening. Astrophysicist Nikku Madhusudhan of the University of Cambridge called the find a “transformational moment” in the search for life beyond our solar system.
K2-18 b is 8.6 times more massive than Earth and 2.6 times wider. It orbits a red dwarf star in the “habitable zone,” where liquid water could exist. That makes it a strong candidate for hosting life. Earlier Webb data had shown the presence of methane and carbon dioxide. Now, the possible presence of DMS and DMDS deepens the intrigue.
Madhusudhan believes K2-18 b could be a Hycean world—an ocean-covered planet with a hydrogen-rich atmosphere. If true, it might support microbial life in warm, deep oceans. He noted that the concentrations of DMS and DMDS are thousands of times higher than Earth’s. These levels can’t be explained without biological activity, based on current scientific knowledge.
However, Madhusudhan urged caution. The team needs to repeat the observations several times to confirm the findings. They also need more studies to rule out non-biological explanations. “We must stay open to other possibilities,” he said.
The James Webb Space Telescope observed the planet using the transit method. As K2-18 b passed in front of its star, light filtered through its atmosphere. The telescope analyzed that light to identify the gases present.
This method had previously hinted at DMS. New observations used a different instrument and light spectrum to strengthen the evidence.
About 5,800 exoplanets have been discovered since the 1990s. Scientists see K2-18 b as one of the most exciting candidates in the hunt for life. Its chemical fingerprints closely resemble those associated with Earth’s biology.
Despite the excitement, Madhusudhan and other scientists emphasize caution. They aim to reduce the chances of a false signal to less than one in a million. That would meet the threshold for a robust detection.
While the discovery doesn’t prove alien life, it shows that current technology can detect biosignatures. It opens a new era in space exploration. “We’ve entered observational astrobiology,” Madhusudhan said.
The search continues, but K2-18 b now stands as one of the best hopes in our quest to find life beyond Earth.
