Ariel mission moves from blueprint to reality

Ariel mission addresses one of the key themes of ESA’s Cosmic Vision programme, which seeks to know the conditions for the formation of planets and for the emergence of life. Ariel will allow us to study the composition of planets, how they form and how they evolve, analyzing a diverse sample of about a thousand planetary atmospheres simultaneously in the visible and in the infrared.

“Ariel will enable planetary science far beyond the boundaries of our own Solar System,” says Günther Hasinger, ESA’s Director of Science. “The adoption of Ariel cements ESA’s commitment to exoplanet research and will ensure European astronomers are at the forefront of this revolutionary field for the next decade and well beyond.”

“This is the first space mission dedicated exclusively to the study of exoplanetary atmospheres, and we know that the atmosphere of a planet is key to knowing its formation and evolution. Gone is the phase where we discovered new planets, and even the one in which water vapor, methane or carbon dioxide were detected for the first time in their atmospheres. With more than four thousand exoplanets discovered to date, we are entering the phase of understanding and explaining their diversity, not only of the planets themselves, but in particular of their atmospheres”, says Manuel López Puertas, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who participates in the mission.

Ariel will not only study the chemical composition and thermal structures of the planets, but will do so by linking them to the environment of the host star. “To know basic data such as the size and mass of the planets we need to precisely determine the parameters of their star. Also, information on the composition of the host star is key to knowing the composition of the planets that formed in its bosom and their migration”, points out Camilla Danielski, IAA-CSIC researcher participating in the mission. This will fill a significant gap in our knowledge about the relationship between the planet's chemistry and the environment in which it formed, or whether the type of host star determines the evolution of the planet.

The telescope’s spectrometers will measure the chemical fingerprints of a planet as it crosses in front of – ‘transits’ – its host star, or passes behind it – an ‘occultation’. Ariel will be able to detect signs of well-known ingredients in the planets’ atmospheres such as water vapour, carbon dioxide and methane. It will also detect more exotic metallic compounds to decipher the overall chemical environment of the distant solar system. For a select number of planets, Ariel will also perform a deep survey of their cloud systems and study seasonal and daily atmospheric variations.

With Ariel we will take exoplanet characterisation to the next level by studying these distant worlds both as individuals and, importantly, as populations, and it will contribute a chemical census of hundreds of solar systems that will allow us to better understand our cosmic neighborhood. Observing these worlds will shed light on the early stages of planetary and atmospheric formation, as well as their subsequent evolution, and will provide insight into how our own Solar System fits into the larger picture of planetary systems.

Several Spanish research centers participate in the mission, both from the scientific and technological fields. Among them is the Institute of Astrophysics of Andalusia, which collaborates in the scientific field through the working groups called "Synergies with the planets of the Solar System" and "Stellar characterization", the latter coordinated by Camilla Danielski (IAA-CSIC). "The experience acquired by the IAA in the study of the planetary atmospheres of our Solar System from space missions and through theoretical models places us in an exceptional position to contribute to the exploitation of this mission", points out Manuel López Puertas (IAA-CSIC).

Ariel is planned for launch on ESA’s new Ariane 6 rocket from Europe’s spaceport in Kourou, French Guiana. It will operate from an orbit around the second Sun-Earth Lagrange point, L2, 1.5 million kilometres directly ‘behind’ Earth as viewed from the Sun, on an initial four-year mission. The ESA-led Comet Interceptor mission will share the ride into space.