FT: Astronomers discover strongest evidence yet of extraterrestrial life

Key topics.Possible signs of life found on ocean-covered planet K2-18bOrganic molecules detected that suggest biological activityFindings mark strongest evidence yet for life beyond Earth.Sign up for your early morning brew of the BizNews Insider to keep you up to speed with the content that matters. The newsletter will land in your inbox at 5:30am weekdays. Register here..Support South Africa's bastion of independent journalism, offering balanced insights on investments, business, and the political economy, by joining BizNews Premium. Register here..If you prefer WhatsApp for updates, sign up for the BizNews channel here..By Clive Cookson.Distant planet is covered with an ocean that may be teeming with microbial activityAstronomers have found signs of biological activity on a planet 124 light years from Earth, in what they call the strongest evidence yet of extraterrestrial life.Scientists used a space telescope to detect specific organic molecules in the atmosphere of K2-18b, a distant water-covered planet that is 8.6 times bigger than Earth and orbits a red dwarf star. On Earth such molecules are only produced by living organisms.“Given everything we know about this planet, a world with an ocean that is teeming with life is the scenario that best fits the data,” said Nikku Madhusudhan, professor of astrophysics at Cambridge university, who led the international project. The research suggests that conditions on K2-18b could mirror Earth’s early oceans.The astronomers stopped short of claiming definitive evidence of biological activity but they said the new findings were compelling, as no known non-biological process could account for such a large quantity of organic molecules. Past claims for extraterrestrial life have not withstood further scrutiny.K2-18b is unlike any body in our solar system — a planet covered in liquid water with a hydrogen-rich atmosphere at habitable temperatures, known as a Hycean world.Astrobiologists investigating extraterrestrial life first became excited about K2-18b in 2023 when data from the new James Webb Space Telescope showed methane and carbon dioxide were present — the first time carbon-based molecules had been detected in the atmosphere of a habitable planet beyond our solar system.Now two separate instruments on the telescope have detected high levels of dimethyl sulphide (DMS) and dimethyl disulphide (DMDS), molecules that are produced on Earth only by living organisms, particularly marine phytoplankton. The results were published on Thursday in Astrophysical Journal Letters.There is no known non-biological process capable of generating DMS and DMDS in the large quantities observed, the Cambridge scientists said, but they remain cautious as they seek confirmation.The team is preparing for more thorough theoretical and experimental work to see whether anything other than living organisms could be responsible for the gases in K2-18b’s atmosphere. .“It’s important that we’re deeply sceptical of our own results, because it’s only by testing and testing again that we will be able to reach the point where we’re confident in them,” Madhusudhan said.“If this is due to life, our baseline assumption is that these oceans could have very high levels of biological activity due to microbial life, similar to what was in Earth’s early oceans,” he said. Whether K2-18b might also host a marine food chain, with larger creatures feeding on the microbes, is impossible to tell.Astronomers measure the composition of a distant planet’s atmosphere by analysing the light from its parent star as the planet passes in front of it. A small fraction of the starlight travels through the planetary atmosphere, leaving an imprint on its spectrum which can reveal which gases are present.Direct imaging of K2-18b is probably beyond the capability of telescopes developed in the foreseeable future because it is too far from Earth and too close to its parent star, said Madhusudhan.Astronomers not involved in K2-18b research gave the findings a cautious welcome. “This paper is another step in the right direction on the very long road to an announcement that we have discovered life elsewhere,” said Dave Clements, an astrophysicist at Imperial College London.“Even the remote chance that we’ve found evidence for an ocean full of bugs on a planet 124 light years away is an incredible thought. We should all pay a lot of attention to what happens next,” said Robert Massey, deputy director of the Royal Astronomical Society.Astronomers have detected about 5,800 planets beyond our solar system since the first were identified 30 years ago, using ever more powerful telescopes. Many others besides K2-18b are being investigated as candidates for extraterrestrial life.Closer to home, astrobiologists hope to find evidence of past or present life in our solar system. The closest analogues to K2-18b may be oceans believed to exist beneath the icy surfaces of some of Jupiter’s and Saturn’s moons. Two spacecraft, the European Space Agency’s Jupiter Icy Moons Explorer and Nasa’s Europa Clipper, are en route to explore them in the early 2030s..© 2025 The Financial Times Ltd.

FT: Astronomers discover strongest evidence yet of extraterrestrial life

Related Stories