Water Vapor Detected in the Atmosphere of Exoplanet in Habitable Zone

These findings might help to improve the evolution of our own livable atmosphere, the researchers said in the paper.

K2-18 b has a mass eight-times larger than that of Earth. The exoplanet was first discovered in 2015. It's not certain whether it is a rocky planet with an extended atmosphere or an icy planet with a high concentration of water under its surface.

Most of the exoplanets that have been detected by the scientific community to have atmospheres have been gas giants, similar to Jupiter. 

Hubble Space Telescope findings

Observing the atmospheres of smaller planets — rocky or icy — could lead to great discoveries in understanding our own planet.

For this study, Angelos Tsiaras and colleagues analyzed exoplanet K2-18 b using spectroscopic data collected by the Hubble Space Telescope. The researchers found strong evidence to suggest the exoplanet has water vapor in its atmosphere. The findings also suggest the planet might contain a large amount of hydrogen in its atmosphere.

Though it is not possible to extract the exact composition of K2-18 b, the authors modeled different scenarios with varying results. One of these indicated that up to 50% of the atmosphere of K2-18 b could be made up of water.

The scientists say that they will continue to study K2-18 b as it is an excellent target for providing further insights into the makeup of habitable-zone exoplanets that could potentially contain life — or give us more knowledge about the formation of our own.