Although thousands of exoplanets of different masses, sizes and orbits have already been discovered – some of them potentially habitable – there seem to be no apparent pattern linking these characteristics to their parent star. Ariel mission will investigate the atmospheres of hundreds of planets orbiting different types of stars. Observations of these worlds will give insights into the early stages of planetary and atmospheric formation, and their subsequent evolution, and might put our Solar System in context.
In particular, the mission will focus on a sample of 1,000 warm and hot exoplanets, ranging from super-Earths to gas giants orbiting close to their parent stars. High temperatures keep different molecular species circulating throughout the atmosphere preventing them from sinking or forming cloud layers, where they can become hidden from remote detection. This provides Ariel with better information about the planet’s internal composition and the formation history of the planetary system.
As well as detecting signs of well-known ingredients such as water vapour, carbon dioxide and methane, Ariel will also be able to measure more exotic metallic compounds, putting the planet in the context of the chemical environment of the host star.
Ariel’s metre-class telescope will operate at visible and infrared wavelengths. It will be launched on ESA’s new Ariane 6 rocket in mid-2028. It will work from an orbit around the second Lagrange point, L2, 1.5 million kilometres directly ‘behind’ Earth as viewed from the Sun, on an initial four-year mission.
Following its selection by ESA’s Science Programme Committee, the mission will now continue into another round of detailed mission studies to define the satellite’s design.