Challenges and perspectives for the characterisation of the atmospheres and exospheres of 'terrestrial’ exoplanets

Decyphering the chemical composition and atmospheric conditions of terrestrial planets around other stars is one of the main driver of exoplanetary science. In fact, atmospheric characterisation of Earth-like planets is expected to bring the first insights into the possibility of biological activity on another planet than Earth. Although the road to the detection of such potential biomarkers is long and challenging, recent spectacular progress have been achieved about the composition, climates and evolution of giant exoplanets with new instruments in space (with the James Webb Space Telescope or the Characterising Exoplanets Satellite) and on the ground (with high-resolution spectrographs at giant telescopes). Today, future projects are being designed to bridge the gap between hot gas giants and temperate terrestrial planets and take us closer and closer to this scientific goal. In this talk, I will review the current challenges and exciting perspectives about the atmospheric characterisation of terrestrial exoplanets.