Scientists discovered suitable biosignature gases for alien life on planet K2-18b. On K2-18b, NASA’s James Webb Space Telescope (JWST) noticed dimethyl sulfide (DMS), a chemical primarily produced by living creatures on Earth. Notably, the exoplanet is nine times the size of our planet and exists in the habitable zone of its planetary system. As exoplanets pass in front of their home stars, the team probes planetary atmospheres using JWST’s Mid-Infrared Instrument (MIRI). Based on its size and other properties, astronomers think K2-18b is a “Hycean” world—that is, one with a large liquid-water ocean and a hydrogen-rich atmosphere.

Although the researchers estimate concentrations of more than 10 parts per million by volume on Earth, they are less than one part per billion. However, further research is required to confirm and expand on their findings.

NASA’s Webb Telescope Finds Possible Life Signs on Exoplanet K2-18b

According to a new study, which was published in The Astrophysical Journal Letters, chemical proof of life on the far-off exoplanet K2-18b has come from NASA’s James Webb Space Telescope. Rare on other planets or moons, these signals, which point to the presence of dimethyl sulfide and dimethyl disulfide, are found in marine plants and bacteria on Earth.

Because K2-18b boasts a hydrogen-rich atmosphere and a planet-wide ocean, researchers classify it as a “hycean world.” Methane and carbon dioxide, found in the planet’s atmosphere in 2023, were the first carbon-based compounds found in the habitable zone of an exoplanet. Though the levels had minimal statistical significance, the researchers also found likely DMS signals, therefore confounding DMS diagnosis. The results underline the possibilities of life on exoplanets.

JWST Data Hints at High Sulfur Levels on Exoplanet, Life or Not

MIRI observations from the JWST expose features in planetary atmospheres that point to DMS or DMDS helping to explain them. Scientists estimate that atmospheric DMS and DMDS levels could be substantially greater than on Earth, that is, above 10 parts per million. Differentiating DMS from DMDS requires more data. Scientists want to investigate undiscovered chemical processes involving no living entities able to generate DMS and DMDS from nothing.