International. The search for potentially habitable planets is often interpreted as the search for a twin of Earth. And yet, some rocky planets outside our Solar System may in fact be more promising candidates for future research. Scientists at the Catholic University of Leuven have run 165 climate simulations of exoplanets permanently facing their "sun" on one side, finding that two of the three possible climates are potentially habitable.
Most exoplanets orbit relatively small, cool stars known as red dwarfs. Only exoplanets orbiting close to their star can be hot enough to get liquid water. What's more, being close to your star also makes these potentially habitable planets relatively easy to detect and observe for research purposes.
Many of these planets orbiting close to their stars face it always on the same side. As a result, they have permanent day and night on opposite sides. However, the climate on these planets is not necessarily very harsh due to a "very efficient 'air conditioning' system that keeps surface temperatures within the habitable range."
On exoplanets with rotation periods of 12 days, a jet of eastward wind was detected in the upper layers of the atmosphere along the equator. This jet of wind interferes with atmospheric circulation on the planet, so its day side becomes too hot to be habitable. A second possible wind system is characterized by two weaker westward wind jets at high latitudes. The third climate option combines weak super-rotation with two high-latitude wind jets. These last two wind systems do not interfere with the "air conditioning system", so the planets remain potentially habitable.
The results provide valuable information for future space missions. Specifically, researchers are currently involved in the preparation of the James Webb Space Telescope mission – Hubble's successor --, as well as the Plato mission.
