Search for radio signals finds no hint of alien civilisation on K2-18b

The planet K2-18b, which sparked intense speculation last year due to apparent signs of life, shows no signs of advanced civilization after an extensive search of its radio signals.

In 2025, Nikku Madhusudhan of the University of Cambridge and colleagues sensationally claimed that K2-18b, an apparent water world 124 light-years away, showed evidence of the dimethyl sulfide (DMS) molecule in its atmosphere. Significant quantities of this molecule on Earth are produced solely by life. Madhusudhan and his team therefore argued that the signals suggest we might also see signs of life coming from K2-18b.

However, subsequent observations and more rigorous analyzes showed that evidence for the existence of DMS could have come from other molecules not associated with life. Scientists concluded that all that could be said about the planet is that it is rich in water, either in the form of an ocean or in the form of a water-rich atmosphere.

Madhusudhan and other researchers are now investigating whether K2-18b might show signs of intelligent life in the form of radio signals beamed into space, like the signals humans have been transmitting since the 1960s.

They observed K2-18b in several orbits around its star, using the Very Large Array telescope in New Mexico and the MeerKAT radio telescope in South Africa, looking for radio signals in frequencies similar to those emitted on Earth. The research would have picked up any signals from transmitters of similar power to that of Arecibo, Puerto Rico’s now-defunct radio telescope.

But after filtering out potential sources of terrestrial interference, they found no signals suggesting K2-18b had powerful radio transmitters. The researchers declined to speak with New scientist on their work.

“If there were an Arecibo-class beacon emitting continuously and directed toward Earth, [from K2-18b]they probably would have detected it,” says Michael Garrett of the University of Manchester, UK.

“Of course, a non-detection does not tell us that the system is uninhabited. It simply restricts a very specific and perhaps rare class of signals: relatively narrow-band persistent radio transmitters operating in the observed frequency range and illuminating the Earth during observation windows,” says Garrett. “Civilizations, if they exist, might not use radio in this way or transmit intermittently, directionally, or at much lower power levels. On a water world, very low frequency radio waves might be more prevalent.”

It may be that alien water worlds are suitable for simple life forms, but they are difficult environments for complex, intelligent life capable of developing technologies, Garrett says. “Without exposed landmasses, the path forward toward building complex infrastructure could be very different from what we have experienced on Earth. »

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