British-American Research Team Spots Possible Biosignatures on Hycean Planet in the Habitable Zone—But Skepticism Remains
LEO CONSTELLATION, DEEP SPACE — In what may become a turning point in the search for extraterrestrial life, a team of British and American astronomers has detected what they describe as the strongest chemical hints yet of life beyond Earth. Using the powerful instruments aboard the James Webb Space Telescope (JWST), scientists identified possible biosignatures in the atmosphere of exoplanet K2-18b, located 124 light-years away in the Leo constellation.
But the discovery is already stirring heated debate within the scientific community—while some hail the finding as a major leap toward answering humanity’s oldest question, others are urging caution, pointing to the planet’s extreme environment and the possibility of false positives.
Webb’s Breakthrough: DMS and the Case for Life
The study, led by Cambridge University astrophysicist Dr. Nikku Madhusudhan, found atmospheric traces of dimethyl sulfide (DMS) and dimethyl disulfide—complex molecules that, on Earth, are produced exclusively by biological organisms, primarily marine algae like phytoplankton.
“These chemicals are classic biosignatures,” Madhusudhan told BBC News. “This is the strongest evidence yet there is possibly life out there.”
However, the team stopped short of declaring a definitive discovery. The findings, published in The Astrophysical Journal Letters, remain in the “three sigma” range of statistical certainty. For a result to be considered scientifically conclusive, it must pass the “five sigma” threshold—a benchmark akin to flipping a coin and getting heads 20 times in a row.
Madhusudhan estimates that just 16 to 24 more hours of JWST observation time could clinch the confirmation, potentially within the next year or two.
Why K2-18b Is Special: A Hycean World in the “Goldilocks Zone”
Among the more than 6,000 exoplanets discovered so far, K2-18b has stood out for years as a prime candidate for life—not because it’s Earth-like, but because it’s part of a class of planets dubbed “hycean worlds.”
Hycean planets are ocean-covered and larger than Earth, with thick, hydrogen-rich atmospheres and the potential to support microbial life. K2-18b is 2.5 times larger than Earth and over eight times its mass, orbiting a cool dwarf star every 33 days.
Importantly, K2-18b lies in its star’s habitable zone, often called the “Goldilocks zone”—not too hot, not too cold, and theoretically capable of maintaining liquid water on its surface.
Last year, the James Webb telescope detected carbon dioxide and methane in the planet’s atmosphere—molecules associated with biological activity on Earth. But it was the recent detection of DMS, and the much stronger signals gathered this time using JWST’s mid-infrared spectrometer, that raised eyebrows across the global astronomy community.
A Divided Scientific Community
Despite the excitement, leading researchers have urged restraint.
Oxford University planetary physicist Raymond Pierrehumbert argues K2-18b may be far too hot to sustain life. “If it does have water, it would be hellishly hot,” he said. “We’re probably looking at oceans of lava, not water.”
MIT’s Sara Seager, a pioneer in exoplanet research, pointed out that earlier claims about water vapor in the planet’s atmosphere were later debunked. “Patience is key,” she advised. “We’ve been here before.”
Adding to the skepticism is a 2022 discovery of DMS on a comet, suggesting that this molecule may form through non-biological processes under the right conditions—though the concentrations observed on K2-18b were thousands of times stronger than what’s found on Earth, making a purely chemical origin less likely, according to Madhusudhan.
What Comes Next: Confirming the Signal
The current level of statistical confidence—three sigma—translates to about a 99.7% probability the detection isn’t a fluke. But in science, especially when it comes to claims as extraordinary as detecting alien life, that isn’t enough.
Cambridge University statistician Stephen Burgess explained it this way: “Three sigma is like flipping a coin ten times and getting all heads. Five sigma? That’s twenty heads in a row. That’s when you can start popping champagne.”
JWST, with its advanced infrared capabilities, will likely revisit K2-18b in the near future to collect the data needed to push the finding into five-sigma territory.
A Cosmic Turning Point?
Regardless of how this specific case plays out, Madhusudhan believes that humanity has entered a new era in astrobiology.
“Whether it’s K2-18b or another target, this is the moment we cross into a reality where confirming extraterrestrial life is not science fiction—it’s science waiting for evidence,” he said.
If confirmed, the presence of biosignatures on K2-18b would represent the first credible detection of life beyond Earth—a discovery that would fundamentally alter our place in the universe.
