In April, a significant scientific announcement captured global attention when researchers claimed to have detected a molecule in the atmosphere of a distant planet that could indicate the presence of life. However, recent analysis by scientists at the University of Chicago has cast doubt on these findings.
The team from UChicago reviewed data from multiple observations and concluded that it cannot be considered a conclusive detection. Rafael Luque, a postdoctoral researcher at UChicago and lead author of the study, stated, "We found the data we have so far is much too noisy for the proof that would be needed to make that claim." The research suggests other molecules could explain the readings, leading to caution regarding the initial claim.
The original announcement was made on April 16 by a team led by Cambridge researchers focusing on K2-18b, a planet located 124 light-years from Earth. They analyzed data from the James Webb Space Telescope and suggested they had identified either dimethyl sulfide or dimethyl disulfide—molecules associated with life on Earth.
UChicago astrophysicists reexamined this data due to their belief that extraordinary claims require extraordinary evidence. Michael Zhang, co-author of the study, noted the difficulty in identifying specific molecules given how faint these readings are: "Anything with a carbon bonded to three hydrogens will show up at a particular wavelength," he explained.
Their analysis indicated several other molecules could account for what was observed by the telescope. Ethane is one such molecule; it has been detected in many planetary atmospheres without indicating life. Caroline Piaulet-Ghorayeb, another co-author, emphasized favoring simpler explanations over exotic ones unless necessary.
Another concern raised was that the initial analysis relied solely on one set of observations. Including data from all available passes weakens evidence for dimethyl sulfide. Luque expressed their aim to provide comprehensive insight into these findings: "Answering whether there is life outside the solar system is the most important question of our field."
Alongside Luque, Piaulet-Ghorayeb and Zhang were grad student Qiao Xue; postdoctoral researchers Michael Radica, Maria Steinrueck and Dominic Samra; and Prof. Jacob Bean as co-authors. Their paper titled “Insufficient evidence for DMS and DMDS in the atmosphere of K2-18 b” has been submitted to Astronomy & Astrophysics Letters.
This research received funding support from NASA, Heising-Simons Foundation, Brinson Foundation, and Natural Sciences and Engineering Research Council of Canada.