Researchers from the University of Zurich, Switzerland, have suggested that large rocky exoplanets at some distance from their star could retain their hydrogen and helium-dominated atmospheres.

The study suggests that these planets can sustain temperate conditions and liquid water on their surface for long periods of time.

As hydrogen and helium gases were readily available in the planet-forming materials around young stars, all planets built up atmospheres that were dominated by these two elements.

In our own Solar System, rocky planets lost this atmosphere in favour of heavier elements, such as oxygen and nitrogen on Earth.

Marit Mol Lous and colleagues from the University of Zurich investigated the evolution of such planets. They modelled the duration that hydrogen and helium-rich exoplanets could host liquid water on their surface.

Their findings suggest that depending on the mass of the planet and how far away it is from its star, these planets could...