Scientists at the University of Cambridge have made a remarkable discovery that may bring humanity a step closer to answering one of its most profound questions: are we alone in the universe?
A research team led by Professor Nikku Madhusudhan has detected chemical signatures in the atmosphere of a distant planet, K2-18b, which may point to the presence of life. The planet, located 700 trillion miles away and more than twice the size of Earth, is orbiting a cool red dwarf star. Using data from NASA's James Webb Space Telescope (JWST), the researchers found potential traces of two key molecules—dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). On Earth, both gases are typically produced by simple marine organisms like phytoplankton and bacteria.
This is the second time that possible signs of life-related chemicals have been detected on K2-18b, and the new findings are considered more promising. The research suggests an unusually high concentration of these molecules in the planet’s atmosphere—thousands of times higher than what is found on Earth.
Professor Madhusudhan expressed cautious optimism, stating that this could be the strongest evidence yet of life beyond Earth. He is hopeful that with further observations, confirmation could be achieved within the next one to two years.
Despite the excitement, the team acknowledges that more data is necessary. Currently, the detection stands at a "three sigma" level of certainty, equating to a 99.7% chance that the findings are not due to random error. For the scientific community to consider it a confirmed discovery, a "five sigma" result—99.99999% certainty—is required.
Independent experts also urge caution. Professor Catherine Heymans, Astronomer Royal for Scotland, noted that even with a five sigma result, it would be difficult to conclusively determine whether the detected gases are of biological origin. The challenge lies in distinguishing between signs of life and those of exotic geological or chemical processes unfamiliar to Earth.
To address this, the Cambridge team is collaborating with other researchers to explore whether DMS and DMDS can be produced through non-biological means. Some scientists propose alternative explanations for the findings, such as geological activity or even the possibility that K2-18b has a molten rock ocean rather than a liquid water ocean, which would make life less likely.
Others, like Dr Nicolas Wogan from NASA’s Ames Research Center, suggest that K2-18b could be a mini gas giant with no solid surface at all. These theories continue to fuel intense scientific debate about the nature of the planet and the true source of the observed molecules.
Still, the absence of ammonia in K2-18b’s atmosphere supports the hypothesis that a vast ocean may exist, absorbing the gas. Whether this ocean is of water or molten rock remains unresolved.
Professor Madhusudhan remains hopeful and sees this as a potentially historic moment in the search for extraterrestrial life. He believes that the coming years may yield definitive answers.
The full findings have been published in "The Astrophysical Journal Letters".