At the same time, he noted, there was still a 0.3% chance that their observation was a statistical fluke. “We need to be open and continue exploring other scenarios,” he added.

K2-18b is part of the “sub-Neptune” class of nearly 6,000 exoplanets that have been discovered beyond the solar system since the 1990s.

Finding evidence of life in the cosmos was the “holy grail” of exoplanet science, Madhusudhan said.