New analysis casts doubt on 'biosignatures' found on planet K2-18B

Summary

Scientists are debating whether data from the James Webb Space Telescope is really pointing to biosignature gases in the atmosphere of planet K2-18b. Adriana M. Gutierrez (CI Lab)/NASA-GSFC hide caption toggle caption Adriana M. Gutierrez (CI Lab)/NASA-GSFC Astronomers have been poring over last week's claim of the detection of life-associated gases in the atmosphere of a distant planet named K2-18b — "the strongest evidence yet that life may exist on a planet outside our solar system," as a University of Cambridge press release put it. But already, one independent check suggests the announcement was overhyped. Jake Taylor of the University of Oxford, who studies the atmospheres of far-away planets with the James Webb Space Telescope, did a quick reanalysis of the starlight filtering through K2-18b's atmosphere. He used a simple method to look for the tell-tale signals of gas molecules of any kind. He was "agnostic" in his approach, and did not look specifically for the exciting sulfur-based gases that, on Earth, are primarily associated with life-forms such as marine microbes. "I wanted to not 'assume' what molecules would be in the atmosphere," Taylor told NPR in an email. "I directly analysed the transmission spectrum that they analysed, in order to have a similar comparison." The results he got suggested that there's too much noise in the data to draw any conclusions. Rather than seeing a bump or a wiggle that indicated a signal, "the data is consistent with a flat line," says Taylor, adding that more observations from the telescope are needed to know what can be reliably said about this planet's atmosphere. "If we want to claim biosignatures, we need to be extremely sure." What this new work shows is that "the strength of the evidence depends on the nitty gritty details of how we interpret the data, and that doesn't pass the bar for me for a convincing detection," says Laura Kreidberg, an expert on the atmospheres of distant planets at the Max Planck Institute ...