James Webb Space Telescope mission announced on September 11th 2023 that it has found methane and carbon dioxide in the atmosphere of exoplanet K2-18 b. Actually it has an abundance of methane and carbon dioxide – and a shortage of ammonia – and exactly this chemical setup supports the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere. Last but not least, they also found indications of the presence of Dimethyl Sulfide (DMS) from phytoplankton, which could be a sign of alien life on the far away planet.
The K2-18 b first found in 2015 is an exoplanet 8.6 times as massive as Earth. Recent studies suggests that it could be a Hycean exoplanet (a hypothetical type of planet, described as a hot, water-covered planet with a hydrogen atmosphere). It has the potential to possess a hydrogen-rich atmospheric layer and a H2O (water) ocean-covered surface. K2-18 b orbits a so-called cool red dwarf star (K2-18) in the habitable zone in only 33 days. The K2-18 solar system resides in the zodiac sign Leo 120 light-years from Earth.
Dimethyl Sulfide (DMS) is a sign of life
The initial observations by the James Webb space telescope revealed a possible detection of a molecule called Dimethyl Sulfide (DMS). DMS is emitted from phytoplankton in marine environments and discharged to the atmosphere here on Earth. If DMS is found on an exoplanet it would be a sign of life and an indication of an eco-system, at least in marine environments. But the conclusion of DMS on K2-18 b is less robust and requires further validation. More Webb observations is needed and will be able to confirm if DMS is present in the atmosphere.
If there are found phytoplankton on K2-18 b we should still not count on alien life in the same way as here on earth. The life that may exist on the planet is probably only, or primarily in the ocean. But the presence of plankton in the alien ocean would indicate a food chain and larger animals.
The James Webb Space Telescope
The James Webb Space Telescope (JWST) is the world’s premier space observatory solving mysteries in our solar system. It is specifically designed to conduct infrared astronomy. and with it´s state-of-the-art instruments it sees objects too old, distant, or faint for the Hubble Space Telescope.
JWST is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency. JWST was launched on December 25, 2021 and after initial calibration took it´s first image on July 12, 2022.
Image credits: Illustration: NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University).