An international team of astronomers studied the atmosphere of exoplanet K2-18 b with the James Webb Space Telescope. The analysis indicates that the gas envelope hosts methane and carbon dioxide, suggesting conditions that could support organic chemistry and perhaps life under certain scenarios. The findings were published through an official channel of the European Space Agency. [Attribution: ESA]
Located about 120 light-years from Earth, exoplanet K2-18 b has a mass roughly 8.6 times that of our world. It orbits the red dwarf star K2-18 in the Leo constellation. Earlier research proposed that parts of the planet’s surface might be covered by liquid water, hinting at intriguing possibilities for atmospheric and surface interactions. [Attribution: NASA/ESA]
Lead author Nikku Madhusudhan of the University of Cambridge remarked that the results underscore the need to consider a wider range of potentially habitable environments when searching for life. Historically, scientists focused on smaller, rocky planets for biosignature signals, but larger worlds offer clearer opportunities for studying their atmospheres at optical and infrared wavelengths. [Attribution: Cambridge University]
The observed mixture of methane and carbon dioxide, along with a lack of ammonia, supports a scenario in which a subsurface ocean could lie beneath K2-18 b’s hydrogen-rich envelope. The observations also detected dimethyl sulfide (DMS), a molecule on Earth closely associated with biological activity, mainly produced by phytoplankton. [Attribution: ESA/NASA]
Despite its location in the so-called habitable zone and the presence of complex carbon-containing molecules, the planet’s large size plays a crucial role in shaping its habitability prospects. With a radius about 2.6 times that of Earth, the atmosphere is expected to be more hydrogen-dominated and thinner in certain layers. This composition raises questions about surface temperatures and pressure conditions that could affect any potential life forms. The search continues with future missions and more detailed modeling to assess whether oceans could persist near the surface or at depth. [Attribution: Cambridge/NASA]
Some scientists note that the presence of liquid water or water-related processes on such a world would not automatically imply life. Instead, they emphasize a broader view of habitable environments, including atmospheric chemistry, ocean dynamics, and geological activity, as researchers refine models of planetary interiors and climate. The ongoing work illustrates how next‑generation telescopes can broaden the scope of habitable-zone exploration beyond traditional, small rocky planets. [Attribution: ESA/University of Cambridge]