Strongest hints yet of biological activity outside the solar system

Astronomers have detected the most promising signs yet of a possible biosignature outside the solar system, although they remain cautious.

Using data from the James Webb Space Telescope (JWST), the astronomers, led by Professor Nikku Madhusudhan from the University of Cambridge, have detected the chemical fingerprints of dimethyl sulfide (DMS) and/or dimethyl disulfide (DMDS), in the atmosphere of the exoplanet K2-18b, which orbits its star in the habitable zone.

On Earth, DMS and DMDS are only produced by life, primarily 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.

The observations have reached the ‘three-sigma’ level of statistical significance – meaning there is a 0.3% probability that they occurred by chance. To reach the accepted classification for scientific discovery, the observations would have to cross the five-sigma threshold, meaning there would be below a 0.00006% probability they occurred by chance.

The researchers say between 16 and 24 hours of follow-up observation time with JWST may help them reach the all-important five-sigma significance. While they are not yet claiming a definitive discovery, the researchers that with powerful tools like JWST and future planned telescopes, humanity is taking new steps toward answering that most essential of questions: are we alone?