Improving our understanding of the limits of habitability in preparation for ANDES and PCS

One of the objectives of the study of telluric exoplanets is the discovery of liquid water on their surface, a sine qua non condition for the appearance of life as we know it. Such temperate objects are inaccessible to current instruments, apart from the significant contribution made by JWST to our understanding of the TRAPPIST system, for instance. Future ELT instruments, especially ANDES and then PCS, will enable to go even further in characterizing this type of planet, with Proxima-b as a prime target. The concept of the habitable zone (ZH) is a generic tool that brings together all the processes affecting the phase of water on the surface of a planet. It is defined as a virtual zone within which a planet can maintain liquid water. However, this concept remains incomplete. Indeed, the interest of the community has so far focused on the effect of stellar type on the position of the inner and outer edges of this HZ (e.g. Selsis et al. 2007, Kopparapu et. al. 2013). In this presentation, we first propose to review the current state of knowledge regarding habitability of exoplanets. Second, we present recent results showing the influence of atmospheric composition on the position of the inner edge of the HZ, based on 1D climate modeling. Understanding the limits of habitability is essential to select relevant targets for ELT instruments, as well as to estimate their observability.