ESA’s Ariel mission will analyse the atmospheres of about a thousand exoplanets. During its survey, Ariel will study rocky planets and gas giants and discover the ingredients that make up their atmospheres. By studying a large sample of hot gaseous planets, like the ones in this artistic impression, scientists can determine trends, which can be used to predict behaviour in other exoplanets. This is extremely useful because it provides insight into how planets may form and evolve.