LONDON, April 17: A research team from the University of Cambridge has found potential indicators of life in the atmosphere of a distant planet known as K2-18b. The team detected molecules that, on Earth, are only produced by simple organisms.

This marks the second—and more promising—detection of life-associated chemicals on K2-18b by NASA’s James Webb Space Telescope (JWST). However, both the Cambridge researchers and independent astronomers emphasize that more data is needed to confirm these findings.

Lead researcher Professor Nikku Madhusudhan, from Cambridge University's Institute of Astronomy, expressed optimism during an interview at his lab, saying, “This is the strongest evidence yet that there could possibly be life out there. I can realistically say that we may confirm this signal within one to two years.”

K2-18b is approximately two and a half times the size of Earth and lies about 700 trillion miles away. Thanks to JWST’s powerful capabilities, scientists can analyze the chemical makeup of the planet’s atmosphere by observing how light from its small red star filters through it.

The Cambridge team found signs of at least one of two molecules—dimethyl sulphide (DMS) and dimethyl disulphide (DMDS)—both of which are associated with biological processes on Earth. Here, such gases are typically produced by marine phytoplankton and certain bacteria.

Prof. Madhusudhan was particularly surprised by the apparent abundance of the gas observed. “The estimated amount of this gas in the atmosphere is thousands of times higher than what we have on Earth,” he said. “So, if this link to life is real, the planet could be teeming with life.”

He went on to say, “If we confirm that life exists on K2-18b, it would strongly suggest that life is common across the galaxy.”

Despite the excitement, the research team acknowledges the current limitations. The latest detection does not yet meet the statistical threshold required for a scientific discovery. To claim such a discovery, the confidence level must reach five sigma—equivalent to 99.99999% certainty. So far, the results stand at three sigma, or 99.7% confidence. While this is a significant improvement from the one sigma (68%) result obtained 18 months ago, it is still not enough to convince the wider scientific community.

Even a five-sigma result, however, may not conclusively prove the presence of life. Professor Catherine Heymans, Scotland’s Astronomer Royal and an astronomer at the University of Edinburgh who is not involved in the study, told the BBC, “Even with that level of certainty, the question remains: what is the origin of this gas? On Earth, it's produced by microorganisms in the ocean, but even perfect data can’t guarantee it's of biological origin on another planet. There may be unknown geological processes at play.”

The Cambridge team agrees and is collaborating with other groups to investigate whether DMS and DMDS can be produced through non-biological processes in laboratory conditions.

Meanwhile, other scientists have proposed alternative explanations for the data, sparking ongoing debate not only about the presence of DMS and DMDS, but also about the composition of K2-18b itself. One theory suggests that the absence of ammonia in the planet’s atmosphere could point to a vast ocean that absorbs it—potentially supporting life. Another theory, however, proposes that the planet may instead have an ocean of molten rock, making life unlikely.

Professor Oliver Shorttle of Cambridge University remarked, “Everything we know about planets orbiting distant stars comes from minuscule amounts of light passing through their atmospheres. It’s an incredibly subtle signal we're trying to interpret—for life, and everything else.”

Dr. Nicolas Wogan at NASA’s Ames Research Center has offered yet another view, proposing that K2-18b might be a mini gas giant with no solid surface at all. This interpretation, along with others, continues to be challenged as new data from JWST emerges.

Despite the uncertainty, Professor Madhusudhan remains hopeful. “There’s still a long scientific journey ahead if we are to answer one of the biggest questions of our time,” he said. “But decades from now, we might look back at this moment as the point when the living universe came within reach. This could be the tipping point—when we became capable of answering the fundamental question: Are we alone in the universe?”

The findings have been published in The Astrophysical Journal Letters.