NASA’s James Webb Telescope has detected carbon dioxide and methane in the atmosphere of exoplanet K2-18 b, a potentially habitable world more than eight times the size of Earth.
The groundbreaking discovery has led astronomers to consider the possibility that K2-18 b may belong to a unique class of exoplanets known as “hycean” planets, which have hydrogen-rich atmospheres and potentially water-covered surfaces, making them potential candidates for life.
The first insight was made possible by observations from NASA’s Hubble Space Telescope.
K2-18 b orbits a cool dwarf star called K2-18, about 120 light-years away from Earth, within the constellation Leo—and sits within the habitable zone.
These exoplanets, with sizes between Earth and Neptune, do not exist in our solar system, making their properties a subject of active debate among scientists.
The idea that K2-18 b could be a Hycean exoplanet is particularly fascinating to scientists, with some experts believing that such planets could offer favorable conditions for life to develop.
Nikku Madhusudhan, an astronomer at the University of Cambridge and lead author of the study, said: “Our findings emphasize the importance of considering different habitable environments in the search for life elsewhere.
“Traditionally, the search for life on exoplanets has focused primarily on smaller rocky planets, but the larger Hycean worlds are significantly more conducive to atmospheric observations.”
The abundance of methane and carbon dioxide, combined with the absence of ammonia, suggests that K2-18 b has a hydrogen-rich atmosphere above a potential water ocean, scientists said.
Astronomers said the telescope’s initial observations also suggested the presence of dimethyl sulfide (DMS), a molecule primarily associated with microbial life such as marine phytoplankton on Earth, suggesting the possibility of biological activity on K2-18b.
But Mr Madhusudhan noted that “more observations are needed to determine if it is indeed DMS that we are seeing”.
Analyzing exoplanet atmospheres poses a challenge due to the intense glare of the parent stars, which obscures smaller celestial bodies.
To overcome this obstacle, the team examined the light passing through K2-18 b’s atmosphere as it transited its host star.
The research will soon be published in The Astrophysical Journal Letters, where the team intends to carry out further research.
“Our ultimate goal is the identification of life on a habitable exoplanet, which would transform our understanding of our place in the universe,” concluded Mr. Madhusudhan.
“Our findings are a promising step toward a deeper understanding of Hycean worlds in this quest.”