Temperate exoplanet LHS 1140 b may be a world completely covered in ice (left) similar to Jupiter’s moon Europa or may be an ice world with a liquid substellar ocean and a cloudy atmosphere (centre). LHS 1140 b is 1.7 times the size of our planet Earth (right) and is the most promising habitable zone exoplanet yet found in the search for liquid water beyond the Solar System.