Hubble Finds Water Vapor on Habitable-Zone Exoplanet for the First Time

With data from the NASA/ESA Hubble Space Telescope, water vapour has been detected in the atmosphere of a super-Earth within the habitable zone by University College London (UCL) researchers in a world first. K2-18b, which is eight times the mass of Earth, is now the only planet orbiting a star outside the Solar System, or exoplanet, known to have both water and temperatures that could support life.

The discovery, published today in Nature Astronomy, is the first successful atmospheric detection of an exoplanet orbiting in its star’s habitable zone, at a distance where water can exist in liquid form.

First author, Dr Angelos Tsiaras (UCL Centre for Space Exochemistry Data,CSED), said: “Finding water on a potentially habitable world other than Earth is incredibly exciting. K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?”