Media ReleaseFrom: Springer Nature
Planetary science: Atmospheric water vapour on a habitable-zone exoplanet *PRESS BRIEFING*
Water vapour has been detected in the atmosphere of an exoplanet lying within the habitable zone of its star, reports a paper published in Nature Astronomy. This finding may improve our understanding of the atmospheric evolution of potentially temperate planets.
Exoplanet K2-18 b has a mass eight-times that of Earth and is twice as large. It was first discovered in 2015 and could either be a rocky planet with an extended atmosphere or an icy planet with a high concentration of water in its interior. Most of the exoplanets with atmospheres previously detected and characterized have been gas giants. Observing the atmospheres of smaller, rocky or icy planets is an essential step towards our understanding of terrestrial bodies.
Angelos Tsiaras and colleagues analysed exoplanet K2-18 b using spectroscopic data obtained by the Hubble Space Telescope. The authors found strong evidence of water vapour in its atmosphere. They also suggest that the planet may have a significant amount of hydrogen in its envelope. Although the precise composition of the atmosphere cannot be extracted, the authors modelled different scenarios that indicate that up to 50% of the atmosphere of K2-18 b could be water.
The authors conclude that K2-18 b provides an excellent target for follow-up observations to provide further insights into the composition and climate of habitable-zone planets.