Azerbaijan National Academy of Science

A nearby exoplanet with rainclouds in its atmosphere may have habitable conditions at its surface, researchers report today. The planet, dubbed K2-18b, is 124 light-years away and 2.6 times the radius of Earth. Last year, astronomers detected clouds of liquid water in the planet’s hydrogen-rich atmosphere, a first for such a small planet.

K2-18b, which is midway in size between Earth and Neptune, is in the habitable zone of its star, so liquid water on its surface is possible; but no one knows what its surface is like. Researchers can’t say for sure whether it has a rocky exterior and thin atmosphere, like Earth, or a dense hydrogen atmosphere above a high-pressure water-ammonia ocean and metallic core, like Neptune—conditions not at all friendly to life.

sciencemag.org