The Earth is special to us: it’s our home. But is it really special as a planet? Every star we can see in the night sky is likely to be orbited by planets, so that there probably are a thousand billion planets in our galaxy alone. 

Since the discovery of the first extra-solar planet (exoplanet) about thirty years ago, more than 6000 exoplanets have been discovered in distant solar systems, with many surprising planets and planetary systems, often very different from our own. A suite of ground-based and space telescopes are currently in operation or will be launched within this decade to discover more exciting planets and unveil their nature: what are they made of? How did they form? What’s the weather like there? Are they habitable? The Ariel Space Telescope, to be launched in 2031 as part of the ESA Science Programme, is the first mission dedicated to the determination of the chemical composition of hundreds of exoplanets, enabling planetary science far beyond the boundaries of the Solar System. 

Finding out why are these new worlds as they are and what is the Earth’s place in our galaxy and –ultimately– in the universe, is one of the key challenges of modern astrophysics. The Ariel mission will bring a fundamental contribution to addressing this challenge, as Prof. Tinetti will illustrate in her talk.