Astronomers have detected potential chemical indicators of life on the exoplanet K2-18b, located 124 light-years away. Led by scientists at the University of Cambridge, the research, utilizing data from NASA and the European Space Agency's James Webb Space Telescope (JWST), has identified compounds in the planet's atmosphere that, on Earth, are primarily produced by living organisms.
The team detected the chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS) in the atmosphere of K2-18b, which orbits its star in the habitable zone. On Earth, DMS and DMDS are produced by microbial life such as marine phytoplankton. While an unknown chemical process may be the source of these molecules in K2-18b's atmosphere, the results are the strongest evidence yet that life may exist on a planet outside our solar system.
K2-18b is about 8.6 times as massive and 2.6 times as large as Earth. The 2023 results showed K2-18b could be a 'Hycean' planet, meaning a habitable world with a liquid ocean and a hydrogen-rich atmosphere. Scientists emphasize the need for further investigation to rule out alternative explanations for the presence of these compounds. Observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006% probability they occurred by chance.