\n Artist\u2019s impression of the exoplanet K2-18b<\/p>\n A. Smith\/N. Mandhusudhan<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n The search for life beyond our solar system heated up this year when scientists reported a tantalising signal from an exoplanet of a molecule that is known to be produced exclusively by life on Earth. Those hopes soon faded when other teams failed to confirm the detection, but the resulting vigorous debate was a good learning process for would-be alien spotters, say exoplanet researchers.<\/p>\n In April, Nikku Madhusudhan at the University of Cambridge and his colleagues announced in a press conference that they had seen the \u201cfirst hints\u2026 of an alien world that is possibly inhabited\u201d. Those hints came from K2-18b, a planet around eight times as massive as Earth, 124 light years away and in the habitable zone of its star, which they had observed with the James Webb Space Telescope (JWST).<\/p>\n <\/p>\n The infrared light from K2-18b suggested that its atmosphere might contain a molecule called dimethyl sulphide (DMS), which, on Earth, is only produced by living organisms, primarily marine phytoplankton.<\/p>\n The news predictably caused a stir among the world\u2019s media and scientific communities. But alongside the excitement, many researchers also urged caution. The DMS signal was extremely weak, and would require many follow-up observations and further analysis to confirm, they said.<\/p>\n Now, after months of additional observations and careful analysis, most astronomers agree that we can\u2019t say that DMS, or anything resembling a biomolecule, exists in K2-18b\u2019s atmosphere \u2013 and if it does, we can\u2019t currently detect it. \u201cThe only two things that we know for sure are that there is methane and carbon dioxide in the atmosphere of this planet,\u201d says Luis Welbanks at Arizona State University.<\/p>\n The claim that we might have seen alien life was premature, says Welbanks. \u201cIt has been repeatedly proven to not be accurate or correct. New observations show that the presence of those gases is not there,\u201d says Welbanks.<\/p>\n However, the spike in the data that was originally attributed to DMS still requires explanation, says Jake Taylor at the University of Oxford. \u201cThere is this bump there. It\u2019s physical. We see it. We just don\u2019t know what the explanation is right now.\u201d<\/p>\n Working out what molecule is causing the spike will require more observations of the planet, which are being planned with JWST next year, says Taylor. Scientists can only measure what is in the planet\u2019s atmosphere using the starlight that passes through it when the planet moves in front of its host star, which happens four times in each Earth year.<\/p>\n For all the strife over the disputed discovery, it has led to some positives, says Taylor. \u201cIt has been a really good learning process for the exoplanet community as a whole. We\u2019ve now gone back to the drawing board in terms of what definitions we should be using for different statistical methods. It\u2019s been really, really useful for us,\u201d he says.<\/p>\n \u201cIt helps us learn how to realign our expectations,\u201d says Welbanks. \u201cThis is a lesson that if you have to play around with numbers to claim the presence of something, that is really challenging. Someone smarter than me said that there\u2019s lies, damned lies and statistics. This whole thing about DMS falls into that category.\u201d<\/p>\n Spend a weekend with some of the brightest minds in science, as you explore the mysteries of the universe in an exciting programme that includes an excursion to see the iconic Lovell Telescope.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/section>\n Topics:<\/p>\n<\/section><\/div>\n![\"Jodrell](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2025\/01\/15113200\/img_6300.jpeg\")
\n <\/picture>\nMysteries of the universe: Cheshire, England<\/h3>\n