Ariel, the Atmospheric remote-sensing infrared exoplanet large-survey mission, addresses one of the key themes of ESA's Cosmic Vision programme: What are the conditions for planet formation and the emergence of life? Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of around 1000 planetary atmospheres simultaneously in visible and infrared wavelengths.

Ariel will be ESA's third dedicated exoplanet mission to launch within a ten-year period, with each mission tackling a unique aspect of exoplanet science. Cheops, the CHaracterising ExOPlanet Satellite, launched in December 2019, is already producing world-class science. Plato, the PLAnetary Transits and Oscillations of stars mission, will be launched in the 2026 timeframe to find and study extrasolar planetary systems, with a special emphasis on rocky planets around Sun-like stars in the habitable zone – the distance from a star where liquid water can exist on a planet's surface. Ariel, planned to launch in 2029, will focus on warm and hot planets, ranging from super-Earths to gas giants orbiting close to their parent stars, taking advantage of their well-mixed atmospheres to decipher their bulk composition.