K2-18b, the planet with a possible sign of life
The account
The James Webb telescope supposedly found, on a distant planet, a gas that on Earth is produced only by living things.
What investigators found
The detection of the gas is weak and disputed by other researchers. It is an intriguing clue, still far from proof.
The story
K2-18b is a planet larger than Earth, about 120 light-years away, that orbits its star in the zone where liquid water could exist. In 2023, the James Webb Space Telescope analyzed its atmosphere and found methane and carbon dioxide, plus a faint signal of dimethyl sulfide, a gas that on Earth is produced almost exclusively by living things in the ocean.
In 2025, the same team, led by Nikku Madhusudhan of the University of Cambridge, announced a stronger signal. Other astronomers redid the calculations and concluded that the data do not yet allow any firm claim. The search continues, and K2-18b has become one of the most observed targets in the sky.