File:Webb Discovers Methane, Carbon Dioxide in Atmosphere of Exoplanet K2-18 b (Artist Illustration) (53179463277).png

English: The James Webb Space Telescope has detected carbon dioxide and methane in the atmosphere of exoplanet K2-18 b, a potentially habitable world 8.6 times as massive as Earth. An abundance of carbon dioxide and methane (along with a shortage of ammonia) is intriguing to astronomers: It supports the idea that this planet may have a water ocean underneath a hydrogen-rich atmosphere.

Webb also hinted at a detection of dimethyl sulphide (DMS) on K2-18 b. On Earth, this molecule is only produced by microbial life. Because the detection needs to be confirmed, the team plans to follow up and look for additional evidence of biological activity on the planet.

K2-18 b orbits the cool dwarf star K2-18 in the habitable zone (where conditions are right for liquid water to exist) and lies about 120 light-years from Earth. While K2-18 b is in the habitable zone, that does not necessarily mean it can support life. For instance, it may have a hostile environment due to its active star. Its ocean may also be too hot to be habitable. More: www.nasa.gov/goddard/2023/webb-discovers-methane-carbon-d...

This illustration shows what exoplanet K2-18 b could look like based on science data. The exoplanet K2-18 c is shown between K2-18 b and its star.

Illustration: NASA, ESA, CSA, Ralf Crawford (STScI), Joseph Olmsted (STScI). Science: Nikku Madhusudhan (IoA)

Image description: Artist illustration (as labeled in the upper left corner) of a planet and its cool red dwarf star. In the foreground on the right is the planet, which fills most of the frame. The planet is various shades of blue, with wisps of white scattered throughout. The left edge of the planet (the side facing the star) is lit, while the rest is in shadow. In the background at the lower left is the star, which appears smaller. The star has a bright red glow. Also in the background is another planet, which appears as a small crescent. The black background of space is speckled with a few small stars.