Signs of life on a distant planet? Not so fast, say these astronomers

Why are other researchers skeptical?

For starters, there are questions about whether K2-18 b even has water — or a surface that could support life. Modelling studies of it and similar planets suggest that they are probably barren4,5. “A lifeless mini-Neptune scenario remains the most parsimonious explanation,” says Joshua Krissansen-Totton, a planetary scientist at the University of Washington in Seattle.

Then there’s the issue of whether DMS or DMDS is actually present, or whether the signal is spurious. The measurement reported by the Cambridge team is “really pushing the limit of what JWST can do”, says Laura Kreidberg, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany.

Schmidt and his colleagues recently re-analysed the 2023 claim from the Cambridge team and found no evidence of biosignature molecules in the data6. Schmidt says that the new observations are “pretty noisy, and any reported features could still just be statistical fluctuations”. The Cambridge researchers, however, say that there is just a 0.3% probability that the signal is due to chance.